Merge tag 'mm-nonmm-stable-2023-04-27-16-01' of git://git.kernel.org/pub/scm/linux...

[platform/kernel/linux-starfive.git] / tools / lib / bpf / libbpf.c

// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

/*
 * Common eBPF ELF object loading operations.
 *
 * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
 * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
 * Copyright (C) 2015 Huawei Inc.
 * Copyright (C) 2017 Nicira, Inc.
 * Copyright (C) 2019 Isovalent, Inc.
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <libgen.h>
#include <inttypes.h>
#include <limits.h>
#include <string.h>
#include <unistd.h>
#include <endian.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>
#include <asm/unistd.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/filter.h>
#include <linux/limits.h>
#include <linux/perf_event.h>
#include <linux/ring_buffer.h>
#include <sys/epoll.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/vfs.h>
#include <sys/utsname.h>
#include <sys/resource.h>
#include <libelf.h>
#include <gelf.h>
#include <zlib.h>

#include "libbpf.h"
#include "bpf.h"
#include "btf.h"
#include "str_error.h"
#include "libbpf_internal.h"
#include "hashmap.h"
#include "bpf_gen_internal.h"
#include "zip.h"

#ifndef BPF_FS_MAGIC
#define BPF_FS_MAGIC            0xcafe4a11
#endif

#define BPF_INSN_SZ (sizeof(struct bpf_insn))

/* vsprintf() in __base_pr() uses nonliteral format string. It may break
 * compilation if user enables corresponding warning. Disable it explicitly.
 */
#pragma GCC diagnostic ignored "-Wformat-nonliteral"

#define __printf(a, b)  __attribute__((format(printf, a, b)))

static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);

static const char * const attach_type_name[] = {
        [BPF_CGROUP_INET_INGRESS]       = "cgroup_inet_ingress",
        [BPF_CGROUP_INET_EGRESS]        = "cgroup_inet_egress",
        [BPF_CGROUP_INET_SOCK_CREATE]   = "cgroup_inet_sock_create",
        [BPF_CGROUP_INET_SOCK_RELEASE]  = "cgroup_inet_sock_release",
        [BPF_CGROUP_SOCK_OPS]           = "cgroup_sock_ops",
        [BPF_CGROUP_DEVICE]             = "cgroup_device",
        [BPF_CGROUP_INET4_BIND]         = "cgroup_inet4_bind",
        [BPF_CGROUP_INET6_BIND]         = "cgroup_inet6_bind",
        [BPF_CGROUP_INET4_CONNECT]      = "cgroup_inet4_connect",
        [BPF_CGROUP_INET6_CONNECT]      = "cgroup_inet6_connect",
        [BPF_CGROUP_INET4_POST_BIND]    = "cgroup_inet4_post_bind",
        [BPF_CGROUP_INET6_POST_BIND]    = "cgroup_inet6_post_bind",
        [BPF_CGROUP_INET4_GETPEERNAME]  = "cgroup_inet4_getpeername",
        [BPF_CGROUP_INET6_GETPEERNAME]  = "cgroup_inet6_getpeername",
        [BPF_CGROUP_INET4_GETSOCKNAME]  = "cgroup_inet4_getsockname",
        [BPF_CGROUP_INET6_GETSOCKNAME]  = "cgroup_inet6_getsockname",
        [BPF_CGROUP_UDP4_SENDMSG]       = "cgroup_udp4_sendmsg",
        [BPF_CGROUP_UDP6_SENDMSG]       = "cgroup_udp6_sendmsg",
        [BPF_CGROUP_SYSCTL]             = "cgroup_sysctl",
        [BPF_CGROUP_UDP4_RECVMSG]       = "cgroup_udp4_recvmsg",
        [BPF_CGROUP_UDP6_RECVMSG]       = "cgroup_udp6_recvmsg",
        [BPF_CGROUP_GETSOCKOPT]         = "cgroup_getsockopt",
        [BPF_CGROUP_SETSOCKOPT]         = "cgroup_setsockopt",
        [BPF_SK_SKB_STREAM_PARSER]      = "sk_skb_stream_parser",
        [BPF_SK_SKB_STREAM_VERDICT]     = "sk_skb_stream_verdict",
        [BPF_SK_SKB_VERDICT]            = "sk_skb_verdict",
        [BPF_SK_MSG_VERDICT]            = "sk_msg_verdict",
        [BPF_LIRC_MODE2]                = "lirc_mode2",
        [BPF_FLOW_DISSECTOR]            = "flow_dissector",
        [BPF_TRACE_RAW_TP]              = "trace_raw_tp",
        [BPF_TRACE_FENTRY]              = "trace_fentry",
        [BPF_TRACE_FEXIT]               = "trace_fexit",
        [BPF_MODIFY_RETURN]             = "modify_return",
        [BPF_LSM_MAC]                   = "lsm_mac",
        [BPF_LSM_CGROUP]                = "lsm_cgroup",
        [BPF_SK_LOOKUP]                 = "sk_lookup",
        [BPF_TRACE_ITER]                = "trace_iter",
        [BPF_XDP_DEVMAP]                = "xdp_devmap",
        [BPF_XDP_CPUMAP]                = "xdp_cpumap",
        [BPF_XDP]                       = "xdp",
        [BPF_SK_REUSEPORT_SELECT]       = "sk_reuseport_select",
        [BPF_SK_REUSEPORT_SELECT_OR_MIGRATE]    = "sk_reuseport_select_or_migrate",
        [BPF_PERF_EVENT]                = "perf_event",
        [BPF_TRACE_KPROBE_MULTI]        = "trace_kprobe_multi",
        [BPF_STRUCT_OPS]                = "struct_ops",
};

static const char * const link_type_name[] = {
        [BPF_LINK_TYPE_UNSPEC]                  = "unspec",
        [BPF_LINK_TYPE_RAW_TRACEPOINT]          = "raw_tracepoint",
        [BPF_LINK_TYPE_TRACING]                 = "tracing",
        [BPF_LINK_TYPE_CGROUP]                  = "cgroup",
        [BPF_LINK_TYPE_ITER]                    = "iter",
        [BPF_LINK_TYPE_NETNS]                   = "netns",
        [BPF_LINK_TYPE_XDP]                     = "xdp",
        [BPF_LINK_TYPE_PERF_EVENT]              = "perf_event",
        [BPF_LINK_TYPE_KPROBE_MULTI]            = "kprobe_multi",
        [BPF_LINK_TYPE_STRUCT_OPS]              = "struct_ops",
        [BPF_LINK_TYPE_NETFILTER]               = "netfilter",
};

static const char * const map_type_name[] = {
        [BPF_MAP_TYPE_UNSPEC]                   = "unspec",
        [BPF_MAP_TYPE_HASH]                     = "hash",
        [BPF_MAP_TYPE_ARRAY]                    = "array",
        [BPF_MAP_TYPE_PROG_ARRAY]               = "prog_array",
        [BPF_MAP_TYPE_PERF_EVENT_ARRAY]         = "perf_event_array",
        [BPF_MAP_TYPE_PERCPU_HASH]              = "percpu_hash",
        [BPF_MAP_TYPE_PERCPU_ARRAY]             = "percpu_array",
        [BPF_MAP_TYPE_STACK_TRACE]              = "stack_trace",
        [BPF_MAP_TYPE_CGROUP_ARRAY]             = "cgroup_array",
        [BPF_MAP_TYPE_LRU_HASH]                 = "lru_hash",
        [BPF_MAP_TYPE_LRU_PERCPU_HASH]          = "lru_percpu_hash",
        [BPF_MAP_TYPE_LPM_TRIE]                 = "lpm_trie",
        [BPF_MAP_TYPE_ARRAY_OF_MAPS]            = "array_of_maps",
        [BPF_MAP_TYPE_HASH_OF_MAPS]             = "hash_of_maps",
        [BPF_MAP_TYPE_DEVMAP]                   = "devmap",
        [BPF_MAP_TYPE_DEVMAP_HASH]              = "devmap_hash",
        [BPF_MAP_TYPE_SOCKMAP]                  = "sockmap",
        [BPF_MAP_TYPE_CPUMAP]                   = "cpumap",
        [BPF_MAP_TYPE_XSKMAP]                   = "xskmap",
        [BPF_MAP_TYPE_SOCKHASH]                 = "sockhash",
        [BPF_MAP_TYPE_CGROUP_STORAGE]           = "cgroup_storage",
        [BPF_MAP_TYPE_REUSEPORT_SOCKARRAY]      = "reuseport_sockarray",
        [BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE]    = "percpu_cgroup_storage",
        [BPF_MAP_TYPE_QUEUE]                    = "queue",
        [BPF_MAP_TYPE_STACK]                    = "stack",
        [BPF_MAP_TYPE_SK_STORAGE]               = "sk_storage",
        [BPF_MAP_TYPE_STRUCT_OPS]               = "struct_ops",
        [BPF_MAP_TYPE_RINGBUF]                  = "ringbuf",
        [BPF_MAP_TYPE_INODE_STORAGE]            = "inode_storage",
        [BPF_MAP_TYPE_TASK_STORAGE]             = "task_storage",
        [BPF_MAP_TYPE_BLOOM_FILTER]             = "bloom_filter",
        [BPF_MAP_TYPE_USER_RINGBUF]             = "user_ringbuf",
        [BPF_MAP_TYPE_CGRP_STORAGE]             = "cgrp_storage",
};

static const char * const prog_type_name[] = {
        [BPF_PROG_TYPE_UNSPEC]                  = "unspec",
        [BPF_PROG_TYPE_SOCKET_FILTER]           = "socket_filter",
        [BPF_PROG_TYPE_KPROBE]                  = "kprobe",
        [BPF_PROG_TYPE_SCHED_CLS]               = "sched_cls",
        [BPF_PROG_TYPE_SCHED_ACT]               = "sched_act",
        [BPF_PROG_TYPE_TRACEPOINT]              = "tracepoint",
        [BPF_PROG_TYPE_XDP]                     = "xdp",
        [BPF_PROG_TYPE_PERF_EVENT]              = "perf_event",
        [BPF_PROG_TYPE_CGROUP_SKB]              = "cgroup_skb",
        [BPF_PROG_TYPE_CGROUP_SOCK]             = "cgroup_sock",
        [BPF_PROG_TYPE_LWT_IN]                  = "lwt_in",
        [BPF_PROG_TYPE_LWT_OUT]                 = "lwt_out",
        [BPF_PROG_TYPE_LWT_XMIT]                = "lwt_xmit",
        [BPF_PROG_TYPE_SOCK_OPS]                = "sock_ops",
        [BPF_PROG_TYPE_SK_SKB]                  = "sk_skb",
        [BPF_PROG_TYPE_CGROUP_DEVICE]           = "cgroup_device",
        [BPF_PROG_TYPE_SK_MSG]                  = "sk_msg",
        [BPF_PROG_TYPE_RAW_TRACEPOINT]          = "raw_tracepoint",
        [BPF_PROG_TYPE_CGROUP_SOCK_ADDR]        = "cgroup_sock_addr",
        [BPF_PROG_TYPE_LWT_SEG6LOCAL]           = "lwt_seg6local",
        [BPF_PROG_TYPE_LIRC_MODE2]              = "lirc_mode2",
        [BPF_PROG_TYPE_SK_REUSEPORT]            = "sk_reuseport",
        [BPF_PROG_TYPE_FLOW_DISSECTOR]          = "flow_dissector",
        [BPF_PROG_TYPE_CGROUP_SYSCTL]           = "cgroup_sysctl",
        [BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE] = "raw_tracepoint_writable",
        [BPF_PROG_TYPE_CGROUP_SOCKOPT]          = "cgroup_sockopt",
        [BPF_PROG_TYPE_TRACING]                 = "tracing",
        [BPF_PROG_TYPE_STRUCT_OPS]              = "struct_ops",
        [BPF_PROG_TYPE_EXT]                     = "ext",
        [BPF_PROG_TYPE_LSM]                     = "lsm",
        [BPF_PROG_TYPE_SK_LOOKUP]               = "sk_lookup",
        [BPF_PROG_TYPE_SYSCALL]                 = "syscall",
        [BPF_PROG_TYPE_NETFILTER]               = "netfilter",
};

static int __base_pr(enum libbpf_print_level level, const char *format,
                     va_list args)
{
        if (level == LIBBPF_DEBUG)
                return 0;

        return vfprintf(stderr, format, args);
}

static libbpf_print_fn_t __libbpf_pr = __base_pr;

libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn)
{
        libbpf_print_fn_t old_print_fn;

        old_print_fn = __atomic_exchange_n(&__libbpf_pr, fn, __ATOMIC_RELAXED);

        return old_print_fn;
}

__printf(2, 3)
void libbpf_print(enum libbpf_print_level level, const char *format, ...)
{
        va_list args;
        int old_errno;
        libbpf_print_fn_t print_fn;

        print_fn = __atomic_load_n(&__libbpf_pr, __ATOMIC_RELAXED);
        if (!print_fn)
                return;

        old_errno = errno;

        va_start(args, format);
        __libbpf_pr(level, format, args);
        va_end(args);

        errno = old_errno;
}

static void pr_perm_msg(int err)
{
        struct rlimit limit;
        char buf[100];

        if (err != -EPERM || geteuid() != 0)
                return;

        err = getrlimit(RLIMIT_MEMLOCK, &limit);
        if (err)
                return;

        if (limit.rlim_cur == RLIM_INFINITY)
                return;

        if (limit.rlim_cur < 1024)
                snprintf(buf, sizeof(buf), "%zu bytes", (size_t)limit.rlim_cur);
        else if (limit.rlim_cur < 1024*1024)
                snprintf(buf, sizeof(buf), "%.1f KiB", (double)limit.rlim_cur / 1024);
        else
                snprintf(buf, sizeof(buf), "%.1f MiB", (double)limit.rlim_cur / (1024*1024));

        pr_warn("permission error while running as root; try raising 'ulimit -l'? current value: %s\n",
                buf);
}

#define STRERR_BUFSIZE  128

/* Copied from tools/perf/util/util.h */
#ifndef zfree
# define zfree(ptr) ({ free(*ptr); *ptr = NULL; })
#endif

#ifndef zclose
# define zclose(fd) ({                  \
        int ___err = 0;                 \
        if ((fd) >= 0)                  \
                ___err = close((fd));   \
        fd = -1;                        \
        ___err; })
#endif

static inline __u64 ptr_to_u64(const void *ptr)
{
        return (__u64) (unsigned long) ptr;
}

int libbpf_set_strict_mode(enum libbpf_strict_mode mode)
{
        /* as of v1.0 libbpf_set_strict_mode() is a no-op */
        return 0;
}

__u32 libbpf_major_version(void)
{
        return LIBBPF_MAJOR_VERSION;
}

__u32 libbpf_minor_version(void)
{
        return LIBBPF_MINOR_VERSION;
}

const char *libbpf_version_string(void)
{
#define __S(X) #X
#define _S(X) __S(X)
        return  "v" _S(LIBBPF_MAJOR_VERSION) "." _S(LIBBPF_MINOR_VERSION);
#undef _S
#undef __S
}

enum reloc_type {
        RELO_LD64,
        RELO_CALL,
        RELO_DATA,
        RELO_EXTERN_LD64,
        RELO_EXTERN_CALL,
        RELO_SUBPROG_ADDR,
        RELO_CORE,
};

struct reloc_desc {
        enum reloc_type type;
        int insn_idx;
        union {
                const struct bpf_core_relo *core_relo; /* used when type == RELO_CORE */
                struct {
                        int map_idx;
                        int sym_off;
                        int ext_idx;
                };
        };
};

/* stored as sec_def->cookie for all libbpf-supported SEC()s */
enum sec_def_flags {
        SEC_NONE = 0,
        /* expected_attach_type is optional, if kernel doesn't support that */
        SEC_EXP_ATTACH_OPT = 1,
        /* legacy, only used by libbpf_get_type_names() and
         * libbpf_attach_type_by_name(), not used by libbpf itself at all.
         * This used to be associated with cgroup (and few other) BPF programs
         * that were attachable through BPF_PROG_ATTACH command. Pretty
         * meaningless nowadays, though.
         */
        SEC_ATTACHABLE = 2,
        SEC_ATTACHABLE_OPT = SEC_ATTACHABLE | SEC_EXP_ATTACH_OPT,
        /* attachment target is specified through BTF ID in either kernel or
         * other BPF program's BTF object
         */
        SEC_ATTACH_BTF = 4,
        /* BPF program type allows sleeping/blocking in kernel */
        SEC_SLEEPABLE = 8,
        /* BPF program support non-linear XDP buffer */
        SEC_XDP_FRAGS = 16,
};

struct bpf_sec_def {
        char *sec;
        enum bpf_prog_type prog_type;
        enum bpf_attach_type expected_attach_type;
        long cookie;
        int handler_id;

        libbpf_prog_setup_fn_t prog_setup_fn;
        libbpf_prog_prepare_load_fn_t prog_prepare_load_fn;
        libbpf_prog_attach_fn_t prog_attach_fn;
};

/*
 * bpf_prog should be a better name but it has been used in
 * linux/filter.h.
 */
struct bpf_program {
        char *name;
        char *sec_name;
        size_t sec_idx;
        const struct bpf_sec_def *sec_def;
        /* this program's instruction offset (in number of instructions)
         * within its containing ELF section
         */
        size_t sec_insn_off;
        /* number of original instructions in ELF section belonging to this
         * program, not taking into account subprogram instructions possible
         * appended later during relocation
         */
        size_t sec_insn_cnt;
        /* Offset (in number of instructions) of the start of instruction
         * belonging to this BPF program  within its containing main BPF
         * program. For the entry-point (main) BPF program, this is always
         * zero. For a sub-program, this gets reset before each of main BPF
         * programs are processed and relocated and is used to determined
         * whether sub-program was already appended to the main program, and
         * if yes, at which instruction offset.
         */
        size_t sub_insn_off;

        /* instructions that belong to BPF program; insns[0] is located at
         * sec_insn_off instruction within its ELF section in ELF file, so
         * when mapping ELF file instruction index to the local instruction,
         * one needs to subtract sec_insn_off; and vice versa.
         */
        struct bpf_insn *insns;
        /* actual number of instruction in this BPF program's image; for
         * entry-point BPF programs this includes the size of main program
         * itself plus all the used sub-programs, appended at the end
         */
        size_t insns_cnt;

        struct reloc_desc *reloc_desc;
        int nr_reloc;

        /* BPF verifier log settings */
        char *log_buf;
        size_t log_size;
        __u32 log_level;

        struct bpf_object *obj;

        int fd;
        bool autoload;
        bool autoattach;
        bool mark_btf_static;
        enum bpf_prog_type type;
        enum bpf_attach_type expected_attach_type;

        int prog_ifindex;
        __u32 attach_btf_obj_fd;
        __u32 attach_btf_id;
        __u32 attach_prog_fd;

        void *func_info;
        __u32 func_info_rec_size;
        __u32 func_info_cnt;

        void *line_info;
        __u32 line_info_rec_size;
        __u32 line_info_cnt;
        __u32 prog_flags;
};

struct bpf_struct_ops {
        const char *tname;
        const struct btf_type *type;
        struct bpf_program **progs;
        __u32 *kern_func_off;
        /* e.g. struct tcp_congestion_ops in bpf_prog's btf format */
        void *data;
        /* e.g. struct bpf_struct_ops_tcp_congestion_ops in
         *      btf_vmlinux's format.
         * struct bpf_struct_ops_tcp_congestion_ops {
         *      [... some other kernel fields ...]
         *      struct tcp_congestion_ops data;
         * }
         * kern_vdata-size == sizeof(struct bpf_struct_ops_tcp_congestion_ops)
         * bpf_map__init_kern_struct_ops() will populate the "kern_vdata"
         * from "data".
         */
        void *kern_vdata;
        __u32 type_id;
};

#define DATA_SEC ".data"
#define BSS_SEC ".bss"
#define RODATA_SEC ".rodata"
#define KCONFIG_SEC ".kconfig"
#define KSYMS_SEC ".ksyms"
#define STRUCT_OPS_SEC ".struct_ops"
#define STRUCT_OPS_LINK_SEC ".struct_ops.link"

enum libbpf_map_type {
        LIBBPF_MAP_UNSPEC,
        LIBBPF_MAP_DATA,
        LIBBPF_MAP_BSS,
        LIBBPF_MAP_RODATA,
        LIBBPF_MAP_KCONFIG,
};

struct bpf_map_def {
        unsigned int type;
        unsigned int key_size;
        unsigned int value_size;
        unsigned int max_entries;
        unsigned int map_flags;
};

struct bpf_map {
        struct bpf_object *obj;
        char *name;
        /* real_name is defined for special internal maps (.rodata*,
         * .data*, .bss, .kconfig) and preserves their original ELF section
         * name. This is important to be able to find corresponding BTF
         * DATASEC information.
         */
        char *real_name;
        int fd;
        int sec_idx;
        size_t sec_offset;
        int map_ifindex;
        int inner_map_fd;
        struct bpf_map_def def;
        __u32 numa_node;
        __u32 btf_var_idx;
        __u32 btf_key_type_id;
        __u32 btf_value_type_id;
        __u32 btf_vmlinux_value_type_id;
        enum libbpf_map_type libbpf_type;
        void *mmaped;
        struct bpf_struct_ops *st_ops;
        struct bpf_map *inner_map;
        void **init_slots;
        int init_slots_sz;
        char *pin_path;
        bool pinned;
        bool reused;
        bool autocreate;
        __u64 map_extra;
};

enum extern_type {
        EXT_UNKNOWN,
        EXT_KCFG,
        EXT_KSYM,
};

enum kcfg_type {
        KCFG_UNKNOWN,
        KCFG_CHAR,
        KCFG_BOOL,
        KCFG_INT,
        KCFG_TRISTATE,
        KCFG_CHAR_ARR,
};

struct extern_desc {
        enum extern_type type;
        int sym_idx;
        int btf_id;
        int sec_btf_id;
        const char *name;
        bool is_set;
        bool is_weak;
        union {
                struct {
                        enum kcfg_type type;
                        int sz;
                        int align;
                        int data_off;
                        bool is_signed;
                } kcfg;
                struct {
                        unsigned long long addr;

                        /* target btf_id of the corresponding kernel var. */
                        int kernel_btf_obj_fd;
                        int kernel_btf_id;

                        /* local btf_id of the ksym extern's type. */
                        __u32 type_id;
                        /* BTF fd index to be patched in for insn->off, this is
                         * 0 for vmlinux BTF, index in obj->fd_array for module
                         * BTF
                         */
                        __s16 btf_fd_idx;
                } ksym;
        };
};

struct module_btf {
        struct btf *btf;
        char *name;
        __u32 id;
        int fd;
        int fd_array_idx;
};

enum sec_type {
        SEC_UNUSED = 0,
        SEC_RELO,
        SEC_BSS,
        SEC_DATA,
        SEC_RODATA,
};

struct elf_sec_desc {
        enum sec_type sec_type;
        Elf64_Shdr *shdr;
        Elf_Data *data;
};

struct elf_state {
        int fd;
        const void *obj_buf;
        size_t obj_buf_sz;
        Elf *elf;
        Elf64_Ehdr *ehdr;
        Elf_Data *symbols;
        Elf_Data *st_ops_data;
        Elf_Data *st_ops_link_data;
        size_t shstrndx; /* section index for section name strings */
        size_t strtabidx;
        struct elf_sec_desc *secs;
        size_t sec_cnt;
        int btf_maps_shndx;
        __u32 btf_maps_sec_btf_id;
        int text_shndx;
        int symbols_shndx;
        int st_ops_shndx;
        int st_ops_link_shndx;
};

struct usdt_manager;

struct bpf_object {
        char name[BPF_OBJ_NAME_LEN];
        char license[64];
        __u32 kern_version;

        struct bpf_program *programs;
        size_t nr_programs;
        struct bpf_map *maps;
        size_t nr_maps;
        size_t maps_cap;

        char *kconfig;
        struct extern_desc *externs;
        int nr_extern;
        int kconfig_map_idx;

        bool loaded;
        bool has_subcalls;
        bool has_rodata;

        struct bpf_gen *gen_loader;

        /* Information when doing ELF related work. Only valid if efile.elf is not NULL */
        struct elf_state efile;

        struct btf *btf;
        struct btf_ext *btf_ext;

        /* Parse and load BTF vmlinux if any of the programs in the object need
         * it at load time.
         */
        struct btf *btf_vmlinux;
        /* Path to the custom BTF to be used for BPF CO-RE relocations as an
         * override for vmlinux BTF.
         */
        char *btf_custom_path;
        /* vmlinux BTF override for CO-RE relocations */
        struct btf *btf_vmlinux_override;
        /* Lazily initialized kernel module BTFs */
        struct module_btf *btf_modules;
        bool btf_modules_loaded;
        size_t btf_module_cnt;
        size_t btf_module_cap;

        /* optional log settings passed to BPF_BTF_LOAD and BPF_PROG_LOAD commands */
        char *log_buf;
        size_t log_size;
        __u32 log_level;

        int *fd_array;
        size_t fd_array_cap;
        size_t fd_array_cnt;

        struct usdt_manager *usdt_man;

        char path[];
};

static const char *elf_sym_str(const struct bpf_object *obj, size_t off);
static const char *elf_sec_str(const struct bpf_object *obj, size_t off);
static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx);
static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name);
static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn);
static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn);
static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn);
static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx);
static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx);

void bpf_program__unload(struct bpf_program *prog)
{
        if (!prog)
                return;

        zclose(prog->fd);

        zfree(&prog->func_info);
        zfree(&prog->line_info);
}

static void bpf_program__exit(struct bpf_program *prog)
{
        if (!prog)
                return;

        bpf_program__unload(prog);
        zfree(&prog->name);
        zfree(&prog->sec_name);
        zfree(&prog->insns);
        zfree(&prog->reloc_desc);

        prog->nr_reloc = 0;
        prog->insns_cnt = 0;
        prog->sec_idx = -1;
}

static bool insn_is_subprog_call(const struct bpf_insn *insn)
{
        return BPF_CLASS(insn->code) == BPF_JMP &&
               BPF_OP(insn->code) == BPF_CALL &&
               BPF_SRC(insn->code) == BPF_K &&
               insn->src_reg == BPF_PSEUDO_CALL &&
               insn->dst_reg == 0 &&
               insn->off == 0;
}

static bool is_call_insn(const struct bpf_insn *insn)
{
        return insn->code == (BPF_JMP | BPF_CALL);
}

static bool insn_is_pseudo_func(struct bpf_insn *insn)
{
        return is_ldimm64_insn(insn) && insn->src_reg == BPF_PSEUDO_FUNC;
}

static int
bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog,
                      const char *name, size_t sec_idx, const char *sec_name,
                      size_t sec_off, void *insn_data, size_t insn_data_sz)
{
        if (insn_data_sz == 0 || insn_data_sz % BPF_INSN_SZ || sec_off % BPF_INSN_SZ) {
                pr_warn("sec '%s': corrupted program '%s', offset %zu, size %zu\n",
                        sec_name, name, sec_off, insn_data_sz);
                return -EINVAL;
        }

        memset(prog, 0, sizeof(*prog));
        prog->obj = obj;

        prog->sec_idx = sec_idx;
        prog->sec_insn_off = sec_off / BPF_INSN_SZ;
        prog->sec_insn_cnt = insn_data_sz / BPF_INSN_SZ;
        /* insns_cnt can later be increased by appending used subprograms */
        prog->insns_cnt = prog->sec_insn_cnt;

        prog->type = BPF_PROG_TYPE_UNSPEC;
        prog->fd = -1;

        /* libbpf's convention for SEC("?abc...") is that it's just like
         * SEC("abc...") but the corresponding bpf_program starts out with
         * autoload set to false.
         */
        if (sec_name[0] == '?') {
                prog->autoload = false;
                /* from now on forget there was ? in section name */
                sec_name++;
        } else {
                prog->autoload = true;
        }

        prog->autoattach = true;

        /* inherit object's log_level */
        prog->log_level = obj->log_level;

        prog->sec_name = strdup(sec_name);
        if (!prog->sec_name)
                goto errout;

        prog->name = strdup(name);
        if (!prog->name)
                goto errout;

        prog->insns = malloc(insn_data_sz);
        if (!prog->insns)
                goto errout;
        memcpy(prog->insns, insn_data, insn_data_sz);

        return 0;
errout:
        pr_warn("sec '%s': failed to allocate memory for prog '%s'\n", sec_name, name);
        bpf_program__exit(prog);
        return -ENOMEM;
}

static int
bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
                         const char *sec_name, int sec_idx)
{
        Elf_Data *symbols = obj->efile.symbols;
        struct bpf_program *prog, *progs;
        void *data = sec_data->d_buf;
        size_t sec_sz = sec_data->d_size, sec_off, prog_sz, nr_syms;
        int nr_progs, err, i;
        const char *name;
        Elf64_Sym *sym;

        progs = obj->programs;
        nr_progs = obj->nr_programs;
        nr_syms = symbols->d_size / sizeof(Elf64_Sym);

        for (i = 0; i < nr_syms; i++) {
                sym = elf_sym_by_idx(obj, i);

                if (sym->st_shndx != sec_idx)
                        continue;
                if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
                        continue;

                prog_sz = sym->st_size;
                sec_off = sym->st_value;

                name = elf_sym_str(obj, sym->st_name);
                if (!name) {
                        pr_warn("sec '%s': failed to get symbol name for offset %zu\n",
                                sec_name, sec_off);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                if (sec_off + prog_sz > sec_sz) {
                        pr_warn("sec '%s': program at offset %zu crosses section boundary\n",
                                sec_name, sec_off);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                if (sec_idx != obj->efile.text_shndx && ELF64_ST_BIND(sym->st_info) == STB_LOCAL) {
                        pr_warn("sec '%s': program '%s' is static and not supported\n", sec_name, name);
                        return -ENOTSUP;
                }

                pr_debug("sec '%s': found program '%s' at insn offset %zu (%zu bytes), code size %zu insns (%zu bytes)\n",
                         sec_name, name, sec_off / BPF_INSN_SZ, sec_off, prog_sz / BPF_INSN_SZ, prog_sz);

                progs = libbpf_reallocarray(progs, nr_progs + 1, sizeof(*progs));
                if (!progs) {
                        /*
                         * In this case the original obj->programs
                         * is still valid, so don't need special treat for
                         * bpf_close_object().
                         */
                        pr_warn("sec '%s': failed to alloc memory for new program '%s'\n",
                                sec_name, name);
                        return -ENOMEM;
                }
                obj->programs = progs;

                prog = &progs[nr_progs];

                err = bpf_object__init_prog(obj, prog, name, sec_idx, sec_name,
                                            sec_off, data + sec_off, prog_sz);
                if (err)
                        return err;

                /* if function is a global/weak symbol, but has restricted
                 * (STV_HIDDEN or STV_INTERNAL) visibility, mark its BTF FUNC
                 * as static to enable more permissive BPF verification mode
                 * with more outside context available to BPF verifier
                 */
                if (ELF64_ST_BIND(sym->st_info) != STB_LOCAL
                    && (ELF64_ST_VISIBILITY(sym->st_other) == STV_HIDDEN
                        || ELF64_ST_VISIBILITY(sym->st_other) == STV_INTERNAL))
                        prog->mark_btf_static = true;

                nr_progs++;
                obj->nr_programs = nr_progs;
        }

        return 0;
}

static const struct btf_member *
find_member_by_offset(const struct btf_type *t, __u32 bit_offset)
{
        struct btf_member *m;
        int i;

        for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
                if (btf_member_bit_offset(t, i) == bit_offset)
                        return m;
        }

        return NULL;
}

static const struct btf_member *
find_member_by_name(const struct btf *btf, const struct btf_type *t,
                    const char *name)
{
        struct btf_member *m;
        int i;

        for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
                if (!strcmp(btf__name_by_offset(btf, m->name_off), name))
                        return m;
        }

        return NULL;
}

#define STRUCT_OPS_VALUE_PREFIX "bpf_struct_ops_"
static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
                                   const char *name, __u32 kind);

static int
find_struct_ops_kern_types(const struct btf *btf, const char *tname,
                           const struct btf_type **type, __u32 *type_id,
                           const struct btf_type **vtype, __u32 *vtype_id,
                           const struct btf_member **data_member)
{
        const struct btf_type *kern_type, *kern_vtype;
        const struct btf_member *kern_data_member;
        __s32 kern_vtype_id, kern_type_id;
        __u32 i;

        kern_type_id = btf__find_by_name_kind(btf, tname, BTF_KIND_STRUCT);
        if (kern_type_id < 0) {
                pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
                        tname);
                return kern_type_id;
        }
        kern_type = btf__type_by_id(btf, kern_type_id);

        /* Find the corresponding "map_value" type that will be used
         * in map_update(BPF_MAP_TYPE_STRUCT_OPS).  For example,
         * find "struct bpf_struct_ops_tcp_congestion_ops" from the
         * btf_vmlinux.
         */
        kern_vtype_id = find_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX,
                                                tname, BTF_KIND_STRUCT);
        if (kern_vtype_id < 0) {
                pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n",
                        STRUCT_OPS_VALUE_PREFIX, tname);
                return kern_vtype_id;
        }
        kern_vtype = btf__type_by_id(btf, kern_vtype_id);

        /* Find "struct tcp_congestion_ops" from
         * struct bpf_struct_ops_tcp_congestion_ops {
         *      [ ... ]
         *      struct tcp_congestion_ops data;
         * }
         */
        kern_data_member = btf_members(kern_vtype);
        for (i = 0; i < btf_vlen(kern_vtype); i++, kern_data_member++) {
                if (kern_data_member->type == kern_type_id)
                        break;
        }
        if (i == btf_vlen(kern_vtype)) {
                pr_warn("struct_ops init_kern: struct %s data is not found in struct %s%s\n",
                        tname, STRUCT_OPS_VALUE_PREFIX, tname);
                return -EINVAL;
        }

        *type = kern_type;
        *type_id = kern_type_id;
        *vtype = kern_vtype;
        *vtype_id = kern_vtype_id;
        *data_member = kern_data_member;

        return 0;
}

static bool bpf_map__is_struct_ops(const struct bpf_map *map)
{
        return map->def.type == BPF_MAP_TYPE_STRUCT_OPS;
}

/* Init the map's fields that depend on kern_btf */
static int bpf_map__init_kern_struct_ops(struct bpf_map *map,
                                         const struct btf *btf,
                                         const struct btf *kern_btf)
{
        const struct btf_member *member, *kern_member, *kern_data_member;
        const struct btf_type *type, *kern_type, *kern_vtype;
        __u32 i, kern_type_id, kern_vtype_id, kern_data_off;
        struct bpf_struct_ops *st_ops;
        void *data, *kern_data;
        const char *tname;
        int err;

        st_ops = map->st_ops;
        type = st_ops->type;
        tname = st_ops->tname;
        err = find_struct_ops_kern_types(kern_btf, tname,
                                         &kern_type, &kern_type_id,
                                         &kern_vtype, &kern_vtype_id,
                                         &kern_data_member);
        if (err)
                return err;

        pr_debug("struct_ops init_kern %s: type_id:%u kern_type_id:%u kern_vtype_id:%u\n",
                 map->name, st_ops->type_id, kern_type_id, kern_vtype_id);

        map->def.value_size = kern_vtype->size;
        map->btf_vmlinux_value_type_id = kern_vtype_id;

        st_ops->kern_vdata = calloc(1, kern_vtype->size);
        if (!st_ops->kern_vdata)
                return -ENOMEM;

        data = st_ops->data;
        kern_data_off = kern_data_member->offset / 8;
        kern_data = st_ops->kern_vdata + kern_data_off;

        member = btf_members(type);
        for (i = 0; i < btf_vlen(type); i++, member++) {
                const struct btf_type *mtype, *kern_mtype;
                __u32 mtype_id, kern_mtype_id;
                void *mdata, *kern_mdata;
                __s64 msize, kern_msize;
                __u32 moff, kern_moff;
                __u32 kern_member_idx;
                const char *mname;

                mname = btf__name_by_offset(btf, member->name_off);
                kern_member = find_member_by_name(kern_btf, kern_type, mname);
                if (!kern_member) {
                        pr_warn("struct_ops init_kern %s: Cannot find member %s in kernel BTF\n",
                                map->name, mname);
                        return -ENOTSUP;
                }

                kern_member_idx = kern_member - btf_members(kern_type);
                if (btf_member_bitfield_size(type, i) ||
                    btf_member_bitfield_size(kern_type, kern_member_idx)) {
                        pr_warn("struct_ops init_kern %s: bitfield %s is not supported\n",
                                map->name, mname);
                        return -ENOTSUP;
                }

                moff = member->offset / 8;
                kern_moff = kern_member->offset / 8;

                mdata = data + moff;
                kern_mdata = kern_data + kern_moff;

                mtype = skip_mods_and_typedefs(btf, member->type, &mtype_id);
                kern_mtype = skip_mods_and_typedefs(kern_btf, kern_member->type,
                                                    &kern_mtype_id);
                if (BTF_INFO_KIND(mtype->info) !=
                    BTF_INFO_KIND(kern_mtype->info)) {
                        pr_warn("struct_ops init_kern %s: Unmatched member type %s %u != %u(kernel)\n",
                                map->name, mname, BTF_INFO_KIND(mtype->info),
                                BTF_INFO_KIND(kern_mtype->info));
                        return -ENOTSUP;
                }

                if (btf_is_ptr(mtype)) {
                        struct bpf_program *prog;

                        prog = st_ops->progs[i];
                        if (!prog)
                                continue;

                        kern_mtype = skip_mods_and_typedefs(kern_btf,
                                                            kern_mtype->type,
                                                            &kern_mtype_id);

                        /* mtype->type must be a func_proto which was
                         * guaranteed in bpf_object__collect_st_ops_relos(),
                         * so only check kern_mtype for func_proto here.
                         */
                        if (!btf_is_func_proto(kern_mtype)) {
                                pr_warn("struct_ops init_kern %s: kernel member %s is not a func ptr\n",
                                        map->name, mname);
                                return -ENOTSUP;
                        }

                        prog->attach_btf_id = kern_type_id;
                        prog->expected_attach_type = kern_member_idx;

                        st_ops->kern_func_off[i] = kern_data_off + kern_moff;

                        pr_debug("struct_ops init_kern %s: func ptr %s is set to prog %s from data(+%u) to kern_data(+%u)\n",
                                 map->name, mname, prog->name, moff,
                                 kern_moff);

                        continue;
                }

                msize = btf__resolve_size(btf, mtype_id);
                kern_msize = btf__resolve_size(kern_btf, kern_mtype_id);
                if (msize < 0 || kern_msize < 0 || msize != kern_msize) {
                        pr_warn("struct_ops init_kern %s: Error in size of member %s: %zd != %zd(kernel)\n",
                                map->name, mname, (ssize_t)msize,
                                (ssize_t)kern_msize);
                        return -ENOTSUP;
                }

                pr_debug("struct_ops init_kern %s: copy %s %u bytes from data(+%u) to kern_data(+%u)\n",
                         map->name, mname, (unsigned int)msize,
                         moff, kern_moff);
                memcpy(kern_mdata, mdata, msize);
        }

        return 0;
}

static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
{
        struct bpf_map *map;
        size_t i;
        int err;

        for (i = 0; i < obj->nr_maps; i++) {
                map = &obj->maps[i];

                if (!bpf_map__is_struct_ops(map))
                        continue;

                err = bpf_map__init_kern_struct_ops(map, obj->btf,
                                                    obj->btf_vmlinux);
                if (err)
                        return err;
        }

        return 0;
}

static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
                                int shndx, Elf_Data *data, __u32 map_flags)
{
        const struct btf_type *type, *datasec;
        const struct btf_var_secinfo *vsi;
        struct bpf_struct_ops *st_ops;
        const char *tname, *var_name;
        __s32 type_id, datasec_id;
        const struct btf *btf;
        struct bpf_map *map;
        __u32 i;

        if (shndx == -1)
                return 0;

        btf = obj->btf;
        datasec_id = btf__find_by_name_kind(btf, sec_name,
                                            BTF_KIND_DATASEC);
        if (datasec_id < 0) {
                pr_warn("struct_ops init: DATASEC %s not found\n",
                        sec_name);
                return -EINVAL;
        }

        datasec = btf__type_by_id(btf, datasec_id);
        vsi = btf_var_secinfos(datasec);
        for (i = 0; i < btf_vlen(datasec); i++, vsi++) {
                type = btf__type_by_id(obj->btf, vsi->type);
                var_name = btf__name_by_offset(obj->btf, type->name_off);

                type_id = btf__resolve_type(obj->btf, vsi->type);
                if (type_id < 0) {
                        pr_warn("struct_ops init: Cannot resolve var type_id %u in DATASEC %s\n",
                                vsi->type, sec_name);
                        return -EINVAL;
                }

                type = btf__type_by_id(obj->btf, type_id);
                tname = btf__name_by_offset(obj->btf, type->name_off);
                if (!tname[0]) {
                        pr_warn("struct_ops init: anonymous type is not supported\n");
                        return -ENOTSUP;
                }
                if (!btf_is_struct(type)) {
                        pr_warn("struct_ops init: %s is not a struct\n", tname);
                        return -EINVAL;
                }

                map = bpf_object__add_map(obj);
                if (IS_ERR(map))
                        return PTR_ERR(map);

                map->sec_idx = shndx;
                map->sec_offset = vsi->offset;
                map->name = strdup(var_name);
                if (!map->name)
                        return -ENOMEM;

                map->def.type = BPF_MAP_TYPE_STRUCT_OPS;
                map->def.key_size = sizeof(int);
                map->def.value_size = type->size;
                map->def.max_entries = 1;
                map->def.map_flags = map_flags;

                map->st_ops = calloc(1, sizeof(*map->st_ops));
                if (!map->st_ops)
                        return -ENOMEM;
                st_ops = map->st_ops;
                st_ops->data = malloc(type->size);
                st_ops->progs = calloc(btf_vlen(type), sizeof(*st_ops->progs));
                st_ops->kern_func_off = malloc(btf_vlen(type) *
                                               sizeof(*st_ops->kern_func_off));
                if (!st_ops->data || !st_ops->progs || !st_ops->kern_func_off)
                        return -ENOMEM;

                if (vsi->offset + type->size > data->d_size) {
                        pr_warn("struct_ops init: var %s is beyond the end of DATASEC %s\n",
                                var_name, sec_name);
                        return -EINVAL;
                }

                memcpy(st_ops->data,
                       data->d_buf + vsi->offset,
                       type->size);
                st_ops->tname = tname;
                st_ops->type = type;
                st_ops->type_id = type_id;

                pr_debug("struct_ops init: struct %s(type_id=%u) %s found at offset %u\n",
                         tname, type_id, var_name, vsi->offset);
        }

        return 0;
}

static int bpf_object_init_struct_ops(struct bpf_object *obj)
{
        int err;

        err = init_struct_ops_maps(obj, STRUCT_OPS_SEC, obj->efile.st_ops_shndx,
                                   obj->efile.st_ops_data, 0);
        err = err ?: init_struct_ops_maps(obj, STRUCT_OPS_LINK_SEC,
                                          obj->efile.st_ops_link_shndx,
                                          obj->efile.st_ops_link_data,
                                          BPF_F_LINK);
        return err;
}

static struct bpf_object *bpf_object__new(const char *path,
                                          const void *obj_buf,
                                          size_t obj_buf_sz,
                                          const char *obj_name)
{
        struct bpf_object *obj;
        char *end;

        obj = calloc(1, sizeof(struct bpf_object) + strlen(path) + 1);
        if (!obj) {
                pr_warn("alloc memory failed for %s\n", path);
                return ERR_PTR(-ENOMEM);
        }

        strcpy(obj->path, path);
        if (obj_name) {
                libbpf_strlcpy(obj->name, obj_name, sizeof(obj->name));
        } else {
                /* Using basename() GNU version which doesn't modify arg. */
                libbpf_strlcpy(obj->name, basename((void *)path), sizeof(obj->name));
                end = strchr(obj->name, '.');
                if (end)
                        *end = 0;
        }

        obj->efile.fd = -1;
        /*
         * Caller of this function should also call
         * bpf_object__elf_finish() after data collection to return
         * obj_buf to user. If not, we should duplicate the buffer to
         * avoid user freeing them before elf finish.
         */
        obj->efile.obj_buf = obj_buf;
        obj->efile.obj_buf_sz = obj_buf_sz;
        obj->efile.btf_maps_shndx = -1;
        obj->efile.st_ops_shndx = -1;
        obj->efile.st_ops_link_shndx = -1;
        obj->kconfig_map_idx = -1;

        obj->kern_version = get_kernel_version();
        obj->loaded = false;

        return obj;
}

static void bpf_object__elf_finish(struct bpf_object *obj)
{
        if (!obj->efile.elf)
                return;

        elf_end(obj->efile.elf);
        obj->efile.elf = NULL;
        obj->efile.symbols = NULL;
        obj->efile.st_ops_data = NULL;
        obj->efile.st_ops_link_data = NULL;

        zfree(&obj->efile.secs);
        obj->efile.sec_cnt = 0;
        zclose(obj->efile.fd);
        obj->efile.obj_buf = NULL;
        obj->efile.obj_buf_sz = 0;
}

static int bpf_object__elf_init(struct bpf_object *obj)
{
        Elf64_Ehdr *ehdr;
        int err = 0;
        Elf *elf;

        if (obj->efile.elf) {
                pr_warn("elf: init internal error\n");
                return -LIBBPF_ERRNO__LIBELF;
        }

        if (obj->efile.obj_buf_sz > 0) {
                /* obj_buf should have been validated by bpf_object__open_mem(). */
                elf = elf_memory((char *)obj->efile.obj_buf, obj->efile.obj_buf_sz);
        } else {
                obj->efile.fd = open(obj->path, O_RDONLY | O_CLOEXEC);
                if (obj->efile.fd < 0) {
                        char errmsg[STRERR_BUFSIZE], *cp;

                        err = -errno;
                        cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
                        pr_warn("elf: failed to open %s: %s\n", obj->path, cp);
                        return err;
                }

                elf = elf_begin(obj->efile.fd, ELF_C_READ_MMAP, NULL);
        }

        if (!elf) {
                pr_warn("elf: failed to open %s as ELF file: %s\n", obj->path, elf_errmsg(-1));
                err = -LIBBPF_ERRNO__LIBELF;
                goto errout;
        }

        obj->efile.elf = elf;

        if (elf_kind(elf) != ELF_K_ELF) {
                err = -LIBBPF_ERRNO__FORMAT;
                pr_warn("elf: '%s' is not a proper ELF object\n", obj->path);
                goto errout;
        }

        if (gelf_getclass(elf) != ELFCLASS64) {
                err = -LIBBPF_ERRNO__FORMAT;
                pr_warn("elf: '%s' is not a 64-bit ELF object\n", obj->path);
                goto errout;
        }

        obj->efile.ehdr = ehdr = elf64_getehdr(elf);
        if (!obj->efile.ehdr) {
                pr_warn("elf: failed to get ELF header from %s: %s\n", obj->path, elf_errmsg(-1));
                err = -LIBBPF_ERRNO__FORMAT;
                goto errout;
        }

        if (elf_getshdrstrndx(elf, &obj->efile.shstrndx)) {
                pr_warn("elf: failed to get section names section index for %s: %s\n",
                        obj->path, elf_errmsg(-1));
                err = -LIBBPF_ERRNO__FORMAT;
                goto errout;
        }

        /* ELF is corrupted/truncated, avoid calling elf_strptr. */
        if (!elf_rawdata(elf_getscn(elf, obj->efile.shstrndx), NULL)) {
                pr_warn("elf: failed to get section names strings from %s: %s\n",
                        obj->path, elf_errmsg(-1));
                err = -LIBBPF_ERRNO__FORMAT;
                goto errout;
        }

        /* Old LLVM set e_machine to EM_NONE */
        if (ehdr->e_type != ET_REL || (ehdr->e_machine && ehdr->e_machine != EM_BPF)) {
                pr_warn("elf: %s is not a valid eBPF object file\n", obj->path);
                err = -LIBBPF_ERRNO__FORMAT;
                goto errout;
        }

        return 0;
errout:
        bpf_object__elf_finish(obj);
        return err;
}

static int bpf_object__check_endianness(struct bpf_object *obj)
{
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
        if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
                return 0;
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
        if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
                return 0;
#else
# error "Unrecognized __BYTE_ORDER__"
#endif
        pr_warn("elf: endianness mismatch in %s.\n", obj->path);
        return -LIBBPF_ERRNO__ENDIAN;
}

static int
bpf_object__init_license(struct bpf_object *obj, void *data, size_t size)
{
        if (!data) {
                pr_warn("invalid license section in %s\n", obj->path);
                return -LIBBPF_ERRNO__FORMAT;
        }
        /* libbpf_strlcpy() only copies first N - 1 bytes, so size + 1 won't
         * go over allowed ELF data section buffer
         */
        libbpf_strlcpy(obj->license, data, min(size + 1, sizeof(obj->license)));
        pr_debug("license of %s is %s\n", obj->path, obj->license);
        return 0;
}

static int
bpf_object__init_kversion(struct bpf_object *obj, void *data, size_t size)
{
        __u32 kver;

        if (!data || size != sizeof(kver)) {
                pr_warn("invalid kver section in %s\n", obj->path);
                return -LIBBPF_ERRNO__FORMAT;
        }
        memcpy(&kver, data, sizeof(kver));
        obj->kern_version = kver;
        pr_debug("kernel version of %s is %x\n", obj->path, obj->kern_version);
        return 0;
}

static bool bpf_map_type__is_map_in_map(enum bpf_map_type type)
{
        if (type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
            type == BPF_MAP_TYPE_HASH_OF_MAPS)
                return true;
        return false;
}

static int find_elf_sec_sz(const struct bpf_object *obj, const char *name, __u32 *size)
{
        Elf_Data *data;
        Elf_Scn *scn;

        if (!name)
                return -EINVAL;

        scn = elf_sec_by_name(obj, name);
        data = elf_sec_data(obj, scn);
        if (data) {
                *size = data->d_size;
                return 0; /* found it */
        }

        return -ENOENT;
}

static Elf64_Sym *find_elf_var_sym(const struct bpf_object *obj, const char *name)
{
        Elf_Data *symbols = obj->efile.symbols;
        const char *sname;
        size_t si;

        for (si = 0; si < symbols->d_size / sizeof(Elf64_Sym); si++) {
                Elf64_Sym *sym = elf_sym_by_idx(obj, si);

                if (ELF64_ST_TYPE(sym->st_info) != STT_OBJECT)
                        continue;

                if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
                    ELF64_ST_BIND(sym->st_info) != STB_WEAK)
                        continue;

                sname = elf_sym_str(obj, sym->st_name);
                if (!sname) {
                        pr_warn("failed to get sym name string for var %s\n", name);
                        return ERR_PTR(-EIO);
                }
                if (strcmp(name, sname) == 0)
                        return sym;
        }

        return ERR_PTR(-ENOENT);
}

static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
{
        struct bpf_map *map;
        int err;

        err = libbpf_ensure_mem((void **)&obj->maps, &obj->maps_cap,
                                sizeof(*obj->maps), obj->nr_maps + 1);
        if (err)
                return ERR_PTR(err);

        map = &obj->maps[obj->nr_maps++];
        map->obj = obj;
        map->fd = -1;
        map->inner_map_fd = -1;
        map->autocreate = true;

        return map;
}

static size_t bpf_map_mmap_sz(const struct bpf_map *map)
{
        long page_sz = sysconf(_SC_PAGE_SIZE);
        size_t map_sz;

        map_sz = (size_t)roundup(map->def.value_size, 8) * map->def.max_entries;
        map_sz = roundup(map_sz, page_sz);
        return map_sz;
}

static char *internal_map_name(struct bpf_object *obj, const char *real_name)
{
        char map_name[BPF_OBJ_NAME_LEN], *p;
        int pfx_len, sfx_len = max((size_t)7, strlen(real_name));

        /* This is one of the more confusing parts of libbpf for various
         * reasons, some of which are historical. The original idea for naming
         * internal names was to include as much of BPF object name prefix as
         * possible, so that it can be distinguished from similar internal
         * maps of a different BPF object.
         * As an example, let's say we have bpf_object named 'my_object_name'
         * and internal map corresponding to '.rodata' ELF section. The final
         * map name advertised to user and to the kernel will be
         * 'my_objec.rodata', taking first 8 characters of object name and
         * entire 7 characters of '.rodata'.
         * Somewhat confusingly, if internal map ELF section name is shorter
         * than 7 characters, e.g., '.bss', we still reserve 7 characters
         * for the suffix, even though we only have 4 actual characters, and
         * resulting map will be called 'my_objec.bss', not even using all 15
         * characters allowed by the kernel. Oh well, at least the truncated
         * object name is somewhat consistent in this case. But if the map
         * name is '.kconfig', we'll still have entirety of '.kconfig' added
         * (8 chars) and thus will be left with only first 7 characters of the
         * object name ('my_obje'). Happy guessing, user, that the final map
         * name will be "my_obje.kconfig".
         * Now, with libbpf starting to support arbitrarily named .rodata.*
         * and .data.* data sections, it's possible that ELF section name is
         * longer than allowed 15 chars, so we now need to be careful to take
         * only up to 15 first characters of ELF name, taking no BPF object
         * name characters at all. So '.rodata.abracadabra' will result in
         * '.rodata.abracad' kernel and user-visible name.
         * We need to keep this convoluted logic intact for .data, .bss and
         * .rodata maps, but for new custom .data.custom and .rodata.custom
         * maps we use their ELF names as is, not prepending bpf_object name
         * in front. We still need to truncate them to 15 characters for the
         * kernel. Full name can be recovered for such maps by using DATASEC
         * BTF type associated with such map's value type, though.
         */
        if (sfx_len >= BPF_OBJ_NAME_LEN)
                sfx_len = BPF_OBJ_NAME_LEN - 1;

        /* if there are two or more dots in map name, it's a custom dot map */
        if (strchr(real_name + 1, '.') != NULL)
                pfx_len = 0;
        else
                pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1, strlen(obj->name));

        snprintf(map_name, sizeof(map_name), "%.*s%.*s", pfx_len, obj->name,
                 sfx_len, real_name);

        /* sanitise map name to characters allowed by kernel */
        for (p = map_name; *p && p < map_name + sizeof(map_name); p++)
                if (!isalnum(*p) && *p != '_' && *p != '.')
                        *p = '_';

        return strdup(map_name);
}

static int
map_fill_btf_type_info(struct bpf_object *obj, struct bpf_map *map);

/* Internal BPF map is mmap()'able only if at least one of corresponding
 * DATASEC's VARs are to be exposed through BPF skeleton. I.e., it's a GLOBAL
 * variable and it's not marked as __hidden (which turns it into, effectively,
 * a STATIC variable).
 */
static bool map_is_mmapable(struct bpf_object *obj, struct bpf_map *map)
{
        const struct btf_type *t, *vt;
        struct btf_var_secinfo *vsi;
        int i, n;

        if (!map->btf_value_type_id)
                return false;

        t = btf__type_by_id(obj->btf, map->btf_value_type_id);
        if (!btf_is_datasec(t))
                return false;

        vsi = btf_var_secinfos(t);
        for (i = 0, n = btf_vlen(t); i < n; i++, vsi++) {
                vt = btf__type_by_id(obj->btf, vsi->type);
                if (!btf_is_var(vt))
                        continue;

                if (btf_var(vt)->linkage != BTF_VAR_STATIC)
                        return true;
        }

        return false;
}

static int
bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
                              const char *real_name, int sec_idx, void *data, size_t data_sz)
{
        struct bpf_map_def *def;
        struct bpf_map *map;
        int err;

        map = bpf_object__add_map(obj);
        if (IS_ERR(map))
                return PTR_ERR(map);

        map->libbpf_type = type;
        map->sec_idx = sec_idx;
        map->sec_offset = 0;
        map->real_name = strdup(real_name);
        map->name = internal_map_name(obj, real_name);
        if (!map->real_name || !map->name) {
                zfree(&map->real_name);
                zfree(&map->name);
                return -ENOMEM;
        }

        def = &map->def;
        def->type = BPF_MAP_TYPE_ARRAY;
        def->key_size = sizeof(int);
        def->value_size = data_sz;
        def->max_entries = 1;
        def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_KCONFIG
                         ? BPF_F_RDONLY_PROG : 0;

        /* failures are fine because of maps like .rodata.str1.1 */
        (void) map_fill_btf_type_info(obj, map);

        if (map_is_mmapable(obj, map))
                def->map_flags |= BPF_F_MMAPABLE;

        pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n",
                 map->name, map->sec_idx, map->sec_offset, def->map_flags);

        map->mmaped = mmap(NULL, bpf_map_mmap_sz(map), PROT_READ | PROT_WRITE,
                           MAP_SHARED | MAP_ANONYMOUS, -1, 0);
        if (map->mmaped == MAP_FAILED) {
                err = -errno;
                map->mmaped = NULL;
                pr_warn("failed to alloc map '%s' content buffer: %d\n",
                        map->name, err);
                zfree(&map->real_name);
                zfree(&map->name);
                return err;
        }

        if (data)
                memcpy(map->mmaped, data, data_sz);

        pr_debug("map %td is \"%s\"\n", map - obj->maps, map->name);
        return 0;
}

static int bpf_object__init_global_data_maps(struct bpf_object *obj)
{
        struct elf_sec_desc *sec_desc;
        const char *sec_name;
        int err = 0, sec_idx;

        /*
         * Populate obj->maps with libbpf internal maps.
         */
        for (sec_idx = 1; sec_idx < obj->efile.sec_cnt; sec_idx++) {
                sec_desc = &obj->efile.secs[sec_idx];

                /* Skip recognized sections with size 0. */
                if (!sec_desc->data || sec_desc->data->d_size == 0)
                        continue;

                switch (sec_desc->sec_type) {
                case SEC_DATA:
                        sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
                        err = bpf_object__init_internal_map(obj, LIBBPF_MAP_DATA,
                                                            sec_name, sec_idx,
                                                            sec_desc->data->d_buf,
                                                            sec_desc->data->d_size);
                        break;
                case SEC_RODATA:
                        obj->has_rodata = true;
                        sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
                        err = bpf_object__init_internal_map(obj, LIBBPF_MAP_RODATA,
                                                            sec_name, sec_idx,
                                                            sec_desc->data->d_buf,
                                                            sec_desc->data->d_size);
                        break;
                case SEC_BSS:
                        sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
                        err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS,
                                                            sec_name, sec_idx,
                                                            NULL,
                                                            sec_desc->data->d_size);
                        break;
                default:
                        /* skip */
                        break;
                }
                if (err)
                        return err;
        }
        return 0;
}


static struct extern_desc *find_extern_by_name(const struct bpf_object *obj,
                                               const void *name)
{
        int i;

        for (i = 0; i < obj->nr_extern; i++) {
                if (strcmp(obj->externs[i].name, name) == 0)
                        return &obj->externs[i];
        }
        return NULL;
}

static int set_kcfg_value_tri(struct extern_desc *ext, void *ext_val,
                              char value)
{
        switch (ext->kcfg.type) {
        case KCFG_BOOL:
                if (value == 'm') {
                        pr_warn("extern (kcfg) '%s': value '%c' implies tristate or char type\n",
                                ext->name, value);
                        return -EINVAL;
                }
                *(bool *)ext_val = value == 'y' ? true : false;
                break;
        case KCFG_TRISTATE:
                if (value == 'y')
                        *(enum libbpf_tristate *)ext_val = TRI_YES;
                else if (value == 'm')
                        *(enum libbpf_tristate *)ext_val = TRI_MODULE;
                else /* value == 'n' */
                        *(enum libbpf_tristate *)ext_val = TRI_NO;
                break;
        case KCFG_CHAR:
                *(char *)ext_val = value;
                break;
        case KCFG_UNKNOWN:
        case KCFG_INT:
        case KCFG_CHAR_ARR:
        default:
                pr_warn("extern (kcfg) '%s': value '%c' implies bool, tristate, or char type\n",
                        ext->name, value);
                return -EINVAL;
        }
        ext->is_set = true;
        return 0;
}

static int set_kcfg_value_str(struct extern_desc *ext, char *ext_val,
                              const char *value)
{
        size_t len;

        if (ext->kcfg.type != KCFG_CHAR_ARR) {
                pr_warn("extern (kcfg) '%s': value '%s' implies char array type\n",
                        ext->name, value);
                return -EINVAL;
        }

        len = strlen(value);
        if (value[len - 1] != '"') {
                pr_warn("extern (kcfg) '%s': invalid string config '%s'\n",
                        ext->name, value);
                return -EINVAL;
        }

        /* strip quotes */
        len -= 2;
        if (len >= ext->kcfg.sz) {
                pr_warn("extern (kcfg) '%s': long string '%s' of (%zu bytes) truncated to %d bytes\n",
                        ext->name, value, len, ext->kcfg.sz - 1);
                len = ext->kcfg.sz - 1;
        }
        memcpy(ext_val, value + 1, len);
        ext_val[len] = '\0';
        ext->is_set = true;
        return 0;
}

static int parse_u64(const char *value, __u64 *res)
{
        char *value_end;
        int err;

        errno = 0;
        *res = strtoull(value, &value_end, 0);
        if (errno) {
                err = -errno;
                pr_warn("failed to parse '%s' as integer: %d\n", value, err);
                return err;
        }
        if (*value_end) {
                pr_warn("failed to parse '%s' as integer completely\n", value);
                return -EINVAL;
        }
        return 0;
}

static bool is_kcfg_value_in_range(const struct extern_desc *ext, __u64 v)
{
        int bit_sz = ext->kcfg.sz * 8;

        if (ext->kcfg.sz == 8)
                return true;

        /* Validate that value stored in u64 fits in integer of `ext->sz`
         * bytes size without any loss of information. If the target integer
         * is signed, we rely on the following limits of integer type of
         * Y bits and subsequent transformation:
         *
         *     -2^(Y-1) <= X           <= 2^(Y-1) - 1
         *            0 <= X + 2^(Y-1) <= 2^Y - 1
         *            0 <= X + 2^(Y-1) <  2^Y
         *
         *  For unsigned target integer, check that all the (64 - Y) bits are
         *  zero.
         */
        if (ext->kcfg.is_signed)
                return v + (1ULL << (bit_sz - 1)) < (1ULL << bit_sz);
        else
                return (v >> bit_sz) == 0;
}

static int set_kcfg_value_num(struct extern_desc *ext, void *ext_val,
                              __u64 value)
{
        if (ext->kcfg.type != KCFG_INT && ext->kcfg.type != KCFG_CHAR &&
            ext->kcfg.type != KCFG_BOOL) {
                pr_warn("extern (kcfg) '%s': value '%llu' implies integer, char, or boolean type\n",
                        ext->name, (unsigned long long)value);
                return -EINVAL;
        }
        if (ext->kcfg.type == KCFG_BOOL && value > 1) {
                pr_warn("extern (kcfg) '%s': value '%llu' isn't boolean compatible\n",
                        ext->name, (unsigned long long)value);
                return -EINVAL;

        }
        if (!is_kcfg_value_in_range(ext, value)) {
                pr_warn("extern (kcfg) '%s': value '%llu' doesn't fit in %d bytes\n",
                        ext->name, (unsigned long long)value, ext->kcfg.sz);
                return -ERANGE;
        }
        switch (ext->kcfg.sz) {
        case 1:
                *(__u8 *)ext_val = value;
                break;
        case 2:
                *(__u16 *)ext_val = value;
                break;
        case 4:
                *(__u32 *)ext_val = value;
                break;
        case 8:
                *(__u64 *)ext_val = value;
                break;
        default:
                return -EINVAL;
        }
        ext->is_set = true;
        return 0;
}

static int bpf_object__process_kconfig_line(struct bpf_object *obj,
                                            char *buf, void *data)
{
        struct extern_desc *ext;
        char *sep, *value;
        int len, err = 0;
        void *ext_val;
        __u64 num;

        if (!str_has_pfx(buf, "CONFIG_"))
                return 0;

        sep = strchr(buf, '=');
        if (!sep) {
                pr_warn("failed to parse '%s': no separator\n", buf);
                return -EINVAL;
        }

        /* Trim ending '\n' */
        len = strlen(buf);
        if (buf[len - 1] == '\n')
                buf[len - 1] = '\0';
        /* Split on '=' and ensure that a value is present. */
        *sep = '\0';
        if (!sep[1]) {
                *sep = '=';
                pr_warn("failed to parse '%s': no value\n", buf);
                return -EINVAL;
        }

        ext = find_extern_by_name(obj, buf);
        if (!ext || ext->is_set)
                return 0;

        ext_val = data + ext->kcfg.data_off;
        value = sep + 1;

        switch (*value) {
        case 'y': case 'n': case 'm':
                err = set_kcfg_value_tri(ext, ext_val, *value);
                break;
        case '"':
                err = set_kcfg_value_str(ext, ext_val, value);
                break;
        default:
                /* assume integer */
                err = parse_u64(value, &num);
                if (err) {
                        pr_warn("extern (kcfg) '%s': value '%s' isn't a valid integer\n", ext->name, value);
                        return err;
                }
                if (ext->kcfg.type != KCFG_INT && ext->kcfg.type != KCFG_CHAR) {
                        pr_warn("extern (kcfg) '%s': value '%s' implies integer type\n", ext->name, value);
                        return -EINVAL;
                }
                err = set_kcfg_value_num(ext, ext_val, num);
                break;
        }
        if (err)
                return err;
        pr_debug("extern (kcfg) '%s': set to %s\n", ext->name, value);
        return 0;
}

static int bpf_object__read_kconfig_file(struct bpf_object *obj, void *data)
{
        char buf[PATH_MAX];
        struct utsname uts;
        int len, err = 0;
        gzFile file;

        uname(&uts);
        len = snprintf(buf, PATH_MAX, "/boot/config-%s", uts.release);
        if (len < 0)
                return -EINVAL;
        else if (len >= PATH_MAX)
                return -ENAMETOOLONG;

        /* gzopen also accepts uncompressed files. */
        file = gzopen(buf, "r");
        if (!file)
                file = gzopen("/proc/config.gz", "r");

        if (!file) {
                pr_warn("failed to open system Kconfig\n");
                return -ENOENT;
        }

        while (gzgets(file, buf, sizeof(buf))) {
                err = bpf_object__process_kconfig_line(obj, buf, data);
                if (err) {
                        pr_warn("error parsing system Kconfig line '%s': %d\n",
                                buf, err);
                        goto out;
                }
        }

out:
        gzclose(file);
        return err;
}

static int bpf_object__read_kconfig_mem(struct bpf_object *obj,
                                        const char *config, void *data)
{
        char buf[PATH_MAX];
        int err = 0;
        FILE *file;

        file = fmemopen((void *)config, strlen(config), "r");
        if (!file) {
                err = -errno;
                pr_warn("failed to open in-memory Kconfig: %d\n", err);
                return err;
        }

        while (fgets(buf, sizeof(buf), file)) {
                err = bpf_object__process_kconfig_line(obj, buf, data);
                if (err) {
                        pr_warn("error parsing in-memory Kconfig line '%s': %d\n",
                                buf, err);
                        break;
                }
        }

        fclose(file);
        return err;
}

static int bpf_object__init_kconfig_map(struct bpf_object *obj)
{
        struct extern_desc *last_ext = NULL, *ext;
        size_t map_sz;
        int i, err;

        for (i = 0; i < obj->nr_extern; i++) {
                ext = &obj->externs[i];
                if (ext->type == EXT_KCFG)
                        last_ext = ext;
        }

        if (!last_ext)
                return 0;

        map_sz = last_ext->kcfg.data_off + last_ext->kcfg.sz;
        err = bpf_object__init_internal_map(obj, LIBBPF_MAP_KCONFIG,
                                            ".kconfig", obj->efile.symbols_shndx,
                                            NULL, map_sz);
        if (err)
                return err;

        obj->kconfig_map_idx = obj->nr_maps - 1;

        return 0;
}

const struct btf_type *
skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
{
        const struct btf_type *t = btf__type_by_id(btf, id);

        if (res_id)
                *res_id = id;

        while (btf_is_mod(t) || btf_is_typedef(t)) {
                if (res_id)
                        *res_id = t->type;
                t = btf__type_by_id(btf, t->type);
        }

        return t;
}

static const struct btf_type *
resolve_func_ptr(const struct btf *btf, __u32 id, __u32 *res_id)
{
        const struct btf_type *t;

        t = skip_mods_and_typedefs(btf, id, NULL);
        if (!btf_is_ptr(t))
                return NULL;

        t = skip_mods_and_typedefs(btf, t->type, res_id);

        return btf_is_func_proto(t) ? t : NULL;
}

static const char *__btf_kind_str(__u16 kind)
{
        switch (kind) {
        case BTF_KIND_UNKN: return "void";
        case BTF_KIND_INT: return "int";
        case BTF_KIND_PTR: return "ptr";
        case BTF_KIND_ARRAY: return "array";
        case BTF_KIND_STRUCT: return "struct";
        case BTF_KIND_UNION: return "union";
        case BTF_KIND_ENUM: return "enum";
        case BTF_KIND_FWD: return "fwd";
        case BTF_KIND_TYPEDEF: return "typedef";
        case BTF_KIND_VOLATILE: return "volatile";
        case BTF_KIND_CONST: return "const";
        case BTF_KIND_RESTRICT: return "restrict";
        case BTF_KIND_FUNC: return "func";
        case BTF_KIND_FUNC_PROTO: return "func_proto";
        case BTF_KIND_VAR: return "var";
        case BTF_KIND_DATASEC: return "datasec";
        case BTF_KIND_FLOAT: return "float";
        case BTF_KIND_DECL_TAG: return "decl_tag";
        case BTF_KIND_TYPE_TAG: return "type_tag";
        case BTF_KIND_ENUM64: return "enum64";
        default: return "unknown";
        }
}

const char *btf_kind_str(const struct btf_type *t)
{
        return __btf_kind_str(btf_kind(t));
}

/*
 * Fetch integer attribute of BTF map definition. Such attributes are
 * represented using a pointer to an array, in which dimensionality of array
 * encodes specified integer value. E.g., int (*type)[BPF_MAP_TYPE_ARRAY];
 * encodes `type => BPF_MAP_TYPE_ARRAY` key/value pair completely using BTF
 * type definition, while using only sizeof(void *) space in ELF data section.
 */
static bool get_map_field_int(const char *map_name, const struct btf *btf,
                              const struct btf_member *m, __u32 *res)
{
        const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
        const char *name = btf__name_by_offset(btf, m->name_off);
        const struct btf_array *arr_info;
        const struct btf_type *arr_t;

        if (!btf_is_ptr(t)) {
                pr_warn("map '%s': attr '%s': expected PTR, got %s.\n",
                        map_name, name, btf_kind_str(t));
                return false;
        }

        arr_t = btf__type_by_id(btf, t->type);
        if (!arr_t) {
                pr_warn("map '%s': attr '%s': type [%u] not found.\n",
                        map_name, name, t->type);
                return false;
        }
        if (!btf_is_array(arr_t)) {
                pr_warn("map '%s': attr '%s': expected ARRAY, got %s.\n",
                        map_name, name, btf_kind_str(arr_t));
                return false;
        }
        arr_info = btf_array(arr_t);
        *res = arr_info->nelems;
        return true;
}

static int pathname_concat(char *buf, size_t buf_sz, const char *path, const char *name)
{
        int len;

        len = snprintf(buf, buf_sz, "%s/%s", path, name);
        if (len < 0)
                return -EINVAL;
        if (len >= buf_sz)
                return -ENAMETOOLONG;

        return 0;
}

static int build_map_pin_path(struct bpf_map *map, const char *path)
{
        char buf[PATH_MAX];
        int err;

        if (!path)
                path = "/sys/fs/bpf";

        err = pathname_concat(buf, sizeof(buf), path, bpf_map__name(map));
        if (err)
                return err;

        return bpf_map__set_pin_path(map, buf);
}

/* should match definition in bpf_helpers.h */
enum libbpf_pin_type {
        LIBBPF_PIN_NONE,
        /* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
        LIBBPF_PIN_BY_NAME,
};

int parse_btf_map_def(const char *map_name, struct btf *btf,
                      const struct btf_type *def_t, bool strict,
                      struct btf_map_def *map_def, struct btf_map_def *inner_def)
{
        const struct btf_type *t;
        const struct btf_member *m;
        bool is_inner = inner_def == NULL;
        int vlen, i;

        vlen = btf_vlen(def_t);
        m = btf_members(def_t);
        for (i = 0; i < vlen; i++, m++) {
                const char *name = btf__name_by_offset(btf, m->name_off);

                if (!name) {
                        pr_warn("map '%s': invalid field #%d.\n", map_name, i);
                        return -EINVAL;
                }
                if (strcmp(name, "type") == 0) {
                        if (!get_map_field_int(map_name, btf, m, &map_def->map_type))
                                return -EINVAL;
                        map_def->parts |= MAP_DEF_MAP_TYPE;
                } else if (strcmp(name, "max_entries") == 0) {
                        if (!get_map_field_int(map_name, btf, m, &map_def->max_entries))
                                return -EINVAL;
                        map_def->parts |= MAP_DEF_MAX_ENTRIES;
                } else if (strcmp(name, "map_flags") == 0) {
                        if (!get_map_field_int(map_name, btf, m, &map_def->map_flags))
                                return -EINVAL;
                        map_def->parts |= MAP_DEF_MAP_FLAGS;
                } else if (strcmp(name, "numa_node") == 0) {
                        if (!get_map_field_int(map_name, btf, m, &map_def->numa_node))
                                return -EINVAL;
                        map_def->parts |= MAP_DEF_NUMA_NODE;
                } else if (strcmp(name, "key_size") == 0) {
                        __u32 sz;

                        if (!get_map_field_int(map_name, btf, m, &sz))
                                return -EINVAL;
                        if (map_def->key_size && map_def->key_size != sz) {
                                pr_warn("map '%s': conflicting key size %u != %u.\n",
                                        map_name, map_def->key_size, sz);
                                return -EINVAL;
                        }
                        map_def->key_size = sz;
                        map_def->parts |= MAP_DEF_KEY_SIZE;
                } else if (strcmp(name, "key") == 0) {
                        __s64 sz;

                        t = btf__type_by_id(btf, m->type);
                        if (!t) {
                                pr_warn("map '%s': key type [%d] not found.\n",
                                        map_name, m->type);
                                return -EINVAL;
                        }
                        if (!btf_is_ptr(t)) {
                                pr_warn("map '%s': key spec is not PTR: %s.\n",
                                        map_name, btf_kind_str(t));
                                return -EINVAL;
                        }
                        sz = btf__resolve_size(btf, t->type);
                        if (sz < 0) {
                                pr_warn("map '%s': can't determine key size for type [%u]: %zd.\n",
                                        map_name, t->type, (ssize_t)sz);
                                return sz;
                        }
                        if (map_def->key_size && map_def->key_size != sz) {
                                pr_warn("map '%s': conflicting key size %u != %zd.\n",
                                        map_name, map_def->key_size, (ssize_t)sz);
                                return -EINVAL;
                        }
                        map_def->key_size = sz;
                        map_def->key_type_id = t->type;
                        map_def->parts |= MAP_DEF_KEY_SIZE | MAP_DEF_KEY_TYPE;
                } else if (strcmp(name, "value_size") == 0) {
                        __u32 sz;

                        if (!get_map_field_int(map_name, btf, m, &sz))
                                return -EINVAL;
                        if (map_def->value_size && map_def->value_size != sz) {
                                pr_warn("map '%s': conflicting value size %u != %u.\n",
                                        map_name, map_def->value_size, sz);
                                return -EINVAL;
                        }
                        map_def->value_size = sz;
                        map_def->parts |= MAP_DEF_VALUE_SIZE;
                } else if (strcmp(name, "value") == 0) {
                        __s64 sz;

                        t = btf__type_by_id(btf, m->type);
                        if (!t) {
                                pr_warn("map '%s': value type [%d] not found.\n",
                                        map_name, m->type);
                                return -EINVAL;
                        }
                        if (!btf_is_ptr(t)) {
                                pr_warn("map '%s': value spec is not PTR: %s.\n",
                                        map_name, btf_kind_str(t));
                                return -EINVAL;
                        }
                        sz = btf__resolve_size(btf, t->type);
                        if (sz < 0) {
                                pr_warn("map '%s': can't determine value size for type [%u]: %zd.\n",
                                        map_name, t->type, (ssize_t)sz);
                                return sz;
                        }
                        if (map_def->value_size && map_def->value_size != sz) {
                                pr_warn("map '%s': conflicting value size %u != %zd.\n",
                                        map_name, map_def->value_size, (ssize_t)sz);
                                return -EINVAL;
                        }
                        map_def->value_size = sz;
                        map_def->value_type_id = t->type;
                        map_def->parts |= MAP_DEF_VALUE_SIZE | MAP_DEF_VALUE_TYPE;
                }
                else if (strcmp(name, "values") == 0) {
                        bool is_map_in_map = bpf_map_type__is_map_in_map(map_def->map_type);
                        bool is_prog_array = map_def->map_type == BPF_MAP_TYPE_PROG_ARRAY;
                        const char *desc = is_map_in_map ? "map-in-map inner" : "prog-array value";
                        char inner_map_name[128];
                        int err;

                        if (is_inner) {
                                pr_warn("map '%s': multi-level inner maps not supported.\n",
                                        map_name);
                                return -ENOTSUP;
                        }
                        if (i != vlen - 1) {
                                pr_warn("map '%s': '%s' member should be last.\n",
                                        map_name, name);
                                return -EINVAL;
                        }
                        if (!is_map_in_map && !is_prog_array) {
                                pr_warn("map '%s': should be map-in-map or prog-array.\n",
                                        map_name);
                                return -ENOTSUP;
                        }
                        if (map_def->value_size && map_def->value_size != 4) {
                                pr_warn("map '%s': conflicting value size %u != 4.\n",
                                        map_name, map_def->value_size);
                                return -EINVAL;
                        }
                        map_def->value_size = 4;
                        t = btf__type_by_id(btf, m->type);
                        if (!t) {
                                pr_warn("map '%s': %s type [%d] not found.\n",
                                        map_name, desc, m->type);
                                return -EINVAL;
                        }
                        if (!btf_is_array(t) || btf_array(t)->nelems) {
                                pr_warn("map '%s': %s spec is not a zero-sized array.\n",
                                        map_name, desc);
                                return -EINVAL;
                        }
                        t = skip_mods_and_typedefs(btf, btf_array(t)->type, NULL);
                        if (!btf_is_ptr(t)) {
                                pr_warn("map '%s': %s def is of unexpected kind %s.\n",
                                        map_name, desc, btf_kind_str(t));
                                return -EINVAL;
                        }
                        t = skip_mods_and_typedefs(btf, t->type, NULL);
                        if (is_prog_array) {
                                if (!btf_is_func_proto(t)) {
                                        pr_warn("map '%s': prog-array value def is of unexpected kind %s.\n",
                                                map_name, btf_kind_str(t));
                                        return -EINVAL;
                                }
                                continue;
                        }
                        if (!btf_is_struct(t)) {
                                pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
                                        map_name, btf_kind_str(t));
                                return -EINVAL;
                        }

                        snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", map_name);
                        err = parse_btf_map_def(inner_map_name, btf, t, strict, inner_def, NULL);
                        if (err)
                                return err;

                        map_def->parts |= MAP_DEF_INNER_MAP;
                } else if (strcmp(name, "pinning") == 0) {
                        __u32 val;

                        if (is_inner) {
                                pr_warn("map '%s': inner def can't be pinned.\n", map_name);
                                return -EINVAL;
                        }
                        if (!get_map_field_int(map_name, btf, m, &val))
                                return -EINVAL;
                        if (val != LIBBPF_PIN_NONE && val != LIBBPF_PIN_BY_NAME) {
                                pr_warn("map '%s': invalid pinning value %u.\n",
                                        map_name, val);
                                return -EINVAL;
                        }
                        map_def->pinning = val;
                        map_def->parts |= MAP_DEF_PINNING;
                } else if (strcmp(name, "map_extra") == 0) {
                        __u32 map_extra;

                        if (!get_map_field_int(map_name, btf, m, &map_extra))
                                return -EINVAL;
                        map_def->map_extra = map_extra;
                        map_def->parts |= MAP_DEF_MAP_EXTRA;
                } else {
                        if (strict) {
                                pr_warn("map '%s': unknown field '%s'.\n", map_name, name);
                                return -ENOTSUP;
                        }
                        pr_debug("map '%s': ignoring unknown field '%s'.\n", map_name, name);
                }
        }

        if (map_def->map_type == BPF_MAP_TYPE_UNSPEC) {
                pr_warn("map '%s': map type isn't specified.\n", map_name);
                return -EINVAL;
        }

        return 0;
}

static size_t adjust_ringbuf_sz(size_t sz)
{
        __u32 page_sz = sysconf(_SC_PAGE_SIZE);
        __u32 mul;

        /* if user forgot to set any size, make sure they see error */
        if (sz == 0)
                return 0;
        /* Kernel expects BPF_MAP_TYPE_RINGBUF's max_entries to be
         * a power-of-2 multiple of kernel's page size. If user diligently
         * satisified these conditions, pass the size through.
         */
        if ((sz % page_sz) == 0 && is_pow_of_2(sz / page_sz))
                return sz;

        /* Otherwise find closest (page_sz * power_of_2) product bigger than
         * user-set size to satisfy both user size request and kernel
         * requirements and substitute correct max_entries for map creation.
         */
        for (mul = 1; mul <= UINT_MAX / page_sz; mul <<= 1) {
                if (mul * page_sz > sz)
                        return mul * page_sz;
        }

        /* if it's impossible to satisfy the conditions (i.e., user size is
         * very close to UINT_MAX but is not a power-of-2 multiple of
         * page_size) then just return original size and let kernel reject it
         */
        return sz;
}

static bool map_is_ringbuf(const struct bpf_map *map)
{
        return map->def.type == BPF_MAP_TYPE_RINGBUF ||
               map->def.type == BPF_MAP_TYPE_USER_RINGBUF;
}

static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
{
        map->def.type = def->map_type;
        map->def.key_size = def->key_size;
        map->def.value_size = def->value_size;
        map->def.max_entries = def->max_entries;
        map->def.map_flags = def->map_flags;
        map->map_extra = def->map_extra;

        map->numa_node = def->numa_node;
        map->btf_key_type_id = def->key_type_id;
        map->btf_value_type_id = def->value_type_id;

        /* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
        if (map_is_ringbuf(map))
                map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);

        if (def->parts & MAP_DEF_MAP_TYPE)
                pr_debug("map '%s': found type = %u.\n", map->name, def->map_type);

        if (def->parts & MAP_DEF_KEY_TYPE)
                pr_debug("map '%s': found key [%u], sz = %u.\n",
                         map->name, def->key_type_id, def->key_size);
        else if (def->parts & MAP_DEF_KEY_SIZE)
                pr_debug("map '%s': found key_size = %u.\n", map->name, def->key_size);

        if (def->parts & MAP_DEF_VALUE_TYPE)
                pr_debug("map '%s': found value [%u], sz = %u.\n",
                         map->name, def->value_type_id, def->value_size);
        else if (def->parts & MAP_DEF_VALUE_SIZE)
                pr_debug("map '%s': found value_size = %u.\n", map->name, def->value_size);

        if (def->parts & MAP_DEF_MAX_ENTRIES)
                pr_debug("map '%s': found max_entries = %u.\n", map->name, def->max_entries);
        if (def->parts & MAP_DEF_MAP_FLAGS)
                pr_debug("map '%s': found map_flags = 0x%x.\n", map->name, def->map_flags);
        if (def->parts & MAP_DEF_MAP_EXTRA)
                pr_debug("map '%s': found map_extra = 0x%llx.\n", map->name,
                         (unsigned long long)def->map_extra);
        if (def->parts & MAP_DEF_PINNING)
                pr_debug("map '%s': found pinning = %u.\n", map->name, def->pinning);
        if (def->parts & MAP_DEF_NUMA_NODE)
                pr_debug("map '%s': found numa_node = %u.\n", map->name, def->numa_node);

        if (def->parts & MAP_DEF_INNER_MAP)
                pr_debug("map '%s': found inner map definition.\n", map->name);
}

static const char *btf_var_linkage_str(__u32 linkage)
{
        switch (linkage) {
        case BTF_VAR_STATIC: return "static";
        case BTF_VAR_GLOBAL_ALLOCATED: return "global";
        case BTF_VAR_GLOBAL_EXTERN: return "extern";
        default: return "unknown";
        }
}

static int bpf_object__init_user_btf_map(struct bpf_object *obj,
                                         const struct btf_type *sec,
                                         int var_idx, int sec_idx,
                                         const Elf_Data *data, bool strict,
                                         const char *pin_root_path)
{
        struct btf_map_def map_def = {}, inner_def = {};
        const struct btf_type *var, *def;
        const struct btf_var_secinfo *vi;
        const struct btf_var *var_extra;
        const char *map_name;
        struct bpf_map *map;
        int err;

        vi = btf_var_secinfos(sec) + var_idx;
        var = btf__type_by_id(obj->btf, vi->type);
        var_extra = btf_var(var);
        map_name = btf__name_by_offset(obj->btf, var->name_off);

        if (map_name == NULL || map_name[0] == '\0') {
                pr_warn("map #%d: empty name.\n", var_idx);
                return -EINVAL;
        }
        if ((__u64)vi->offset + vi->size > data->d_size) {
                pr_warn("map '%s' BTF data is corrupted.\n", map_name);
                return -EINVAL;
        }
        if (!btf_is_var(var)) {
                pr_warn("map '%s': unexpected var kind %s.\n",
                        map_name, btf_kind_str(var));
                return -EINVAL;
        }
        if (var_extra->linkage != BTF_VAR_GLOBAL_ALLOCATED) {
                pr_warn("map '%s': unsupported map linkage %s.\n",
                        map_name, btf_var_linkage_str(var_extra->linkage));
                return -EOPNOTSUPP;
        }

        def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
        if (!btf_is_struct(def)) {
                pr_warn("map '%s': unexpected def kind %s.\n",
                        map_name, btf_kind_str(var));
                return -EINVAL;
        }
        if (def->size > vi->size) {
                pr_warn("map '%s': invalid def size.\n", map_name);
                return -EINVAL;
        }

        map = bpf_object__add_map(obj);
        if (IS_ERR(map))
                return PTR_ERR(map);
        map->name = strdup(map_name);
        if (!map->name) {
                pr_warn("map '%s': failed to alloc map name.\n", map_name);
                return -ENOMEM;
        }
        map->libbpf_type = LIBBPF_MAP_UNSPEC;
        map->def.type = BPF_MAP_TYPE_UNSPEC;
        map->sec_idx = sec_idx;
        map->sec_offset = vi->offset;
        map->btf_var_idx = var_idx;
        pr_debug("map '%s': at sec_idx %d, offset %zu.\n",
                 map_name, map->sec_idx, map->sec_offset);

        err = parse_btf_map_def(map->name, obj->btf, def, strict, &map_def, &inner_def);
        if (err)
                return err;

        fill_map_from_def(map, &map_def);

        if (map_def.pinning == LIBBPF_PIN_BY_NAME) {
                err = build_map_pin_path(map, pin_root_path);
                if (err) {
                        pr_warn("map '%s': couldn't build pin path.\n", map->name);
                        return err;
                }
        }

        if (map_def.parts & MAP_DEF_INNER_MAP) {
                map->inner_map = calloc(1, sizeof(*map->inner_map));
                if (!map->inner_map)
                        return -ENOMEM;
                map->inner_map->fd = -1;
                map->inner_map->sec_idx = sec_idx;
                map->inner_map->name = malloc(strlen(map_name) + sizeof(".inner") + 1);
                if (!map->inner_map->name)
                        return -ENOMEM;
                sprintf(map->inner_map->name, "%s.inner", map_name);

                fill_map_from_def(map->inner_map, &inner_def);
        }

        err = map_fill_btf_type_info(obj, map);
        if (err)
                return err;

        return 0;
}

static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
                                          const char *pin_root_path)
{
        const struct btf_type *sec = NULL;
        int nr_types, i, vlen, err;
        const struct btf_type *t;
        const char *name;
        Elf_Data *data;
        Elf_Scn *scn;

        if (obj->efile.btf_maps_shndx < 0)
                return 0;

        scn = elf_sec_by_idx(obj, obj->efile.btf_maps_shndx);
        data = elf_sec_data(obj, scn);
        if (!scn || !data) {
                pr_warn("elf: failed to get %s map definitions for %s\n",
                        MAPS_ELF_SEC, obj->path);
                return -EINVAL;
        }

        nr_types = btf__type_cnt(obj->btf);
        for (i = 1; i < nr_types; i++) {
                t = btf__type_by_id(obj->btf, i);
                if (!btf_is_datasec(t))
                        continue;
                name = btf__name_by_offset(obj->btf, t->name_off);
                if (strcmp(name, MAPS_ELF_SEC) == 0) {
                        sec = t;
                        obj->efile.btf_maps_sec_btf_id = i;
                        break;
                }
        }

        if (!sec) {
                pr_warn("DATASEC '%s' not found.\n", MAPS_ELF_SEC);
                return -ENOENT;
        }

        vlen = btf_vlen(sec);
        for (i = 0; i < vlen; i++) {
                err = bpf_object__init_user_btf_map(obj, sec, i,
                                                    obj->efile.btf_maps_shndx,
                                                    data, strict,
                                                    pin_root_path);
                if (err)
                        return err;
        }

        return 0;
}

static int bpf_object__init_maps(struct bpf_object *obj,
                                 const struct bpf_object_open_opts *opts)
{
        const char *pin_root_path;
        bool strict;
        int err = 0;

        strict = !OPTS_GET(opts, relaxed_maps, false);
        pin_root_path = OPTS_GET(opts, pin_root_path, NULL);

        err = bpf_object__init_user_btf_maps(obj, strict, pin_root_path);
        err = err ?: bpf_object__init_global_data_maps(obj);
        err = err ?: bpf_object__init_kconfig_map(obj);
        err = err ?: bpf_object_init_struct_ops(obj);

        return err;
}

static bool section_have_execinstr(struct bpf_object *obj, int idx)
{
        Elf64_Shdr *sh;

        sh = elf_sec_hdr(obj, elf_sec_by_idx(obj, idx));
        if (!sh)
                return false;

        return sh->sh_flags & SHF_EXECINSTR;
}

static bool btf_needs_sanitization(struct bpf_object *obj)
{
        bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
        bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
        bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
        bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
        bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
        bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
        bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);

        return !has_func || !has_datasec || !has_func_global || !has_float ||
               !has_decl_tag || !has_type_tag || !has_enum64;
}

static int bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
{
        bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
        bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
        bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
        bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
        bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
        bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
        bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
        int enum64_placeholder_id = 0;
        struct btf_type *t;
        int i, j, vlen;

        for (i = 1; i < btf__type_cnt(btf); i++) {
                t = (struct btf_type *)btf__type_by_id(btf, i);

                if ((!has_datasec && btf_is_var(t)) || (!has_decl_tag && btf_is_decl_tag(t))) {
                        /* replace VAR/DECL_TAG with INT */
                        t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
                        /*
                         * using size = 1 is the safest choice, 4 will be too
                         * big and cause kernel BTF validation failure if
                         * original variable took less than 4 bytes
                         */
                        t->size = 1;
                        *(int *)(t + 1) = BTF_INT_ENC(0, 0, 8);
                } else if (!has_datasec && btf_is_datasec(t)) {
                        /* replace DATASEC with STRUCT */
                        const struct btf_var_secinfo *v = btf_var_secinfos(t);
                        struct btf_member *m = btf_members(t);
                        struct btf_type *vt;
                        char *name;

                        name = (char *)btf__name_by_offset(btf, t->name_off);
                        while (*name) {
                                if (*name == '.')
                                        *name = '_';
                                name++;
                        }

                        vlen = btf_vlen(t);
                        t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, vlen);
                        for (j = 0; j < vlen; j++, v++, m++) {
                                /* order of field assignments is important */
                                m->offset = v->offset * 8;
                                m->type = v->type;
                                /* preserve variable name as member name */
                                vt = (void *)btf__type_by_id(btf, v->type);
                                m->name_off = vt->name_off;
                        }
                } else if (!has_func && btf_is_func_proto(t)) {
                        /* replace FUNC_PROTO with ENUM */
                        vlen = btf_vlen(t);
                        t->info = BTF_INFO_ENC(BTF_KIND_ENUM, 0, vlen);
                        t->size = sizeof(__u32); /* kernel enforced */
                } else if (!has_func && btf_is_func(t)) {
                        /* replace FUNC with TYPEDEF */
                        t->info = BTF_INFO_ENC(BTF_KIND_TYPEDEF, 0, 0);
                } else if (!has_func_global && btf_is_func(t)) {
                        /* replace BTF_FUNC_GLOBAL with BTF_FUNC_STATIC */
                        t->info = BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0);
                } else if (!has_float && btf_is_float(t)) {
                        /* replace FLOAT with an equally-sized empty STRUCT;
                         * since C compilers do not accept e.g. "float" as a
                         * valid struct name, make it anonymous
                         */
                        t->name_off = 0;
                        t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 0);
                } else if (!has_type_tag && btf_is_type_tag(t)) {
                        /* replace TYPE_TAG with a CONST */
                        t->name_off = 0;
                        t->info = BTF_INFO_ENC(BTF_KIND_CONST, 0, 0);
                } else if (!has_enum64 && btf_is_enum(t)) {
                        /* clear the kflag */
                        t->info = btf_type_info(btf_kind(t), btf_vlen(t), false);
                } else if (!has_enum64 && btf_is_enum64(t)) {
                        /* replace ENUM64 with a union */
                        struct btf_member *m;

                        if (enum64_placeholder_id == 0) {
                                enum64_placeholder_id = btf__add_int(btf, "enum64_placeholder", 1, 0);
                                if (enum64_placeholder_id < 0)
                                        return enum64_placeholder_id;

                                t = (struct btf_type *)btf__type_by_id(btf, i);
                        }

                        m = btf_members(t);
                        vlen = btf_vlen(t);
                        t->info = BTF_INFO_ENC(BTF_KIND_UNION, 0, vlen);
                        for (j = 0; j < vlen; j++, m++) {
                                m->type = enum64_placeholder_id;
                                m->offset = 0;
                        }
                }
        }

        return 0;
}

static bool libbpf_needs_btf(const struct bpf_object *obj)
{
        return obj->efile.btf_maps_shndx >= 0 ||
               obj->efile.st_ops_shndx >= 0 ||
               obj->efile.st_ops_link_shndx >= 0 ||
               obj->nr_extern > 0;
}

static bool kernel_needs_btf(const struct bpf_object *obj)
{
        return obj->efile.st_ops_shndx >= 0 || obj->efile.st_ops_link_shndx >= 0;
}

static int bpf_object__init_btf(struct bpf_object *obj,
                                Elf_Data *btf_data,
                                Elf_Data *btf_ext_data)
{
        int err = -ENOENT;

        if (btf_data) {
                obj->btf = btf__new(btf_data->d_buf, btf_data->d_size);
                err = libbpf_get_error(obj->btf);
                if (err) {
                        obj->btf = NULL;
                        pr_warn("Error loading ELF section %s: %d.\n", BTF_ELF_SEC, err);
                        goto out;
                }
                /* enforce 8-byte pointers for BPF-targeted BTFs */
                btf__set_pointer_size(obj->btf, 8);
        }
        if (btf_ext_data) {
                struct btf_ext_info *ext_segs[3];
                int seg_num, sec_num;

                if (!obj->btf) {
                        pr_debug("Ignore ELF section %s because its depending ELF section %s is not found.\n",
                                 BTF_EXT_ELF_SEC, BTF_ELF_SEC);
                        goto out;
                }
                obj->btf_ext = btf_ext__new(btf_ext_data->d_buf, btf_ext_data->d_size);
                err = libbpf_get_error(obj->btf_ext);
                if (err) {
                        pr_warn("Error loading ELF section %s: %d. Ignored and continue.\n",
                                BTF_EXT_ELF_SEC, err);
                        obj->btf_ext = NULL;
                        goto out;
                }

                /* setup .BTF.ext to ELF section mapping */
                ext_segs[0] = &obj->btf_ext->func_info;
                ext_segs[1] = &obj->btf_ext->line_info;
                ext_segs[2] = &obj->btf_ext->core_relo_info;
                for (seg_num = 0; seg_num < ARRAY_SIZE(ext_segs); seg_num++) {
                        struct btf_ext_info *seg = ext_segs[seg_num];
                        const struct btf_ext_info_sec *sec;
                        const char *sec_name;
                        Elf_Scn *scn;

                        if (seg->sec_cnt == 0)
                                continue;

                        seg->sec_idxs = calloc(seg->sec_cnt, sizeof(*seg->sec_idxs));
                        if (!seg->sec_idxs) {
                                err = -ENOMEM;
                                goto out;
                        }

                        sec_num = 0;
                        for_each_btf_ext_sec(seg, sec) {
                                /* preventively increment index to avoid doing
                                 * this before every continue below
                                 */
                                sec_num++;

                                sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
                                if (str_is_empty(sec_name))
                                        continue;
                                scn = elf_sec_by_name(obj, sec_name);
                                if (!scn)
                                        continue;

                                seg->sec_idxs[sec_num - 1] = elf_ndxscn(scn);
                        }
                }
        }
out:
        if (err && libbpf_needs_btf(obj)) {
                pr_warn("BTF is required, but is missing or corrupted.\n");
                return err;
        }
        return 0;
}

static int compare_vsi_off(const void *_a, const void *_b)
{
        const struct btf_var_secinfo *a = _a;
        const struct btf_var_secinfo *b = _b;

        return a->offset - b->offset;
}

static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
                             struct btf_type *t)
{
        __u32 size = 0, i, vars = btf_vlen(t);
        const char *sec_name = btf__name_by_offset(btf, t->name_off);
        struct btf_var_secinfo *vsi;
        bool fixup_offsets = false;
        int err;

        if (!sec_name) {
                pr_debug("No name found in string section for DATASEC kind.\n");
                return -ENOENT;
        }

        /* Extern-backing datasecs (.ksyms, .kconfig) have their size and
         * variable offsets set at the previous step. Further, not every
         * extern BTF VAR has corresponding ELF symbol preserved, so we skip
         * all fixups altogether for such sections and go straight to sorting
         * VARs within their DATASEC.
         */
        if (strcmp(sec_name, KCONFIG_SEC) == 0 || strcmp(sec_name, KSYMS_SEC) == 0)
                goto sort_vars;

        /* Clang leaves DATASEC size and VAR offsets as zeroes, so we need to
         * fix this up. But BPF static linker already fixes this up and fills
         * all the sizes and offsets during static linking. So this step has
         * to be optional. But the STV_HIDDEN handling is non-optional for any
         * non-extern DATASEC, so the variable fixup loop below handles both
         * functions at the same time, paying the cost of BTF VAR <-> ELF
         * symbol matching just once.
         */
        if (t->size == 0) {
                err = find_elf_sec_sz(obj, sec_name, &size);
                if (err || !size) {
                        pr_debug("sec '%s': failed to determine size from ELF: size %u, err %d\n",
                                 sec_name, size, err);
                        return -ENOENT;
                }

                t->size = size;
                fixup_offsets = true;
        }

        for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
                const struct btf_type *t_var;
                struct btf_var *var;
                const char *var_name;
                Elf64_Sym *sym;

                t_var = btf__type_by_id(btf, vsi->type);
                if (!t_var || !btf_is_var(t_var)) {
                        pr_debug("sec '%s': unexpected non-VAR type found\n", sec_name);
                        return -EINVAL;
                }

                var = btf_var(t_var);
                if (var->linkage == BTF_VAR_STATIC || var->linkage == BTF_VAR_GLOBAL_EXTERN)
                        continue;

                var_name = btf__name_by_offset(btf, t_var->name_off);
                if (!var_name) {
                        pr_debug("sec '%s': failed to find name of DATASEC's member #%d\n",
                                 sec_name, i);
                        return -ENOENT;
                }

                sym = find_elf_var_sym(obj, var_name);
                if (IS_ERR(sym)) {
                        pr_debug("sec '%s': failed to find ELF symbol for VAR '%s'\n",
                                 sec_name, var_name);
                        return -ENOENT;
                }

                if (fixup_offsets)
                        vsi->offset = sym->st_value;

                /* if variable is a global/weak symbol, but has restricted
                 * (STV_HIDDEN or STV_INTERNAL) visibility, mark its BTF VAR
                 * as static. This follows similar logic for functions (BPF
                 * subprogs) and influences libbpf's further decisions about
                 * whether to make global data BPF array maps as
                 * BPF_F_MMAPABLE.
                 */
                if (ELF64_ST_VISIBILITY(sym->st_other) == STV_HIDDEN
                    || ELF64_ST_VISIBILITY(sym->st_other) == STV_INTERNAL)
                        var->linkage = BTF_VAR_STATIC;
        }

sort_vars:
        qsort(btf_var_secinfos(t), vars, sizeof(*vsi), compare_vsi_off);
        return 0;
}

static int bpf_object_fixup_btf(struct bpf_object *obj)
{
        int i, n, err = 0;

        if (!obj->btf)
                return 0;

        n = btf__type_cnt(obj->btf);
        for (i = 1; i < n; i++) {
                struct btf_type *t = btf_type_by_id(obj->btf, i);

                /* Loader needs to fix up some of the things compiler
                 * couldn't get its hands on while emitting BTF. This
                 * is section size and global variable offset. We use
                 * the info from the ELF itself for this purpose.
                 */
                if (btf_is_datasec(t)) {
                        err = btf_fixup_datasec(obj, obj->btf, t);
                        if (err)
                                return err;
                }
        }

        return 0;
}

static bool prog_needs_vmlinux_btf(struct bpf_program *prog)
{
        if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
            prog->type == BPF_PROG_TYPE_LSM)
                return true;

        /* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
         * also need vmlinux BTF
         */
        if (prog->type == BPF_PROG_TYPE_TRACING && !prog->attach_prog_fd)
                return true;

        return false;
}

static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
{
        struct bpf_program *prog;
        int i;

        /* CO-RE relocations need kernel BTF, only when btf_custom_path
         * is not specified
         */
        if (obj->btf_ext && obj->btf_ext->core_relo_info.len && !obj->btf_custom_path)
                return true;

        /* Support for typed ksyms needs kernel BTF */
        for (i = 0; i < obj->nr_extern; i++) {
                const struct extern_desc *ext;

                ext = &obj->externs[i];
                if (ext->type == EXT_KSYM && ext->ksym.type_id)
                        return true;
        }

        bpf_object__for_each_program(prog, obj) {
                if (!prog->autoload)
                        continue;
                if (prog_needs_vmlinux_btf(prog))
                        return true;
        }

        return false;
}

static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
{
        int err;

        /* btf_vmlinux could be loaded earlier */
        if (obj->btf_vmlinux || obj->gen_loader)
                return 0;

        if (!force && !obj_needs_vmlinux_btf(obj))
                return 0;

        obj->btf_vmlinux = btf__load_vmlinux_btf();
        err = libbpf_get_error(obj->btf_vmlinux);
        if (err) {
                pr_warn("Error loading vmlinux BTF: %d\n", err);
                obj->btf_vmlinux = NULL;
                return err;
        }
        return 0;
}

static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
{
        struct btf *kern_btf = obj->btf;
        bool btf_mandatory, sanitize;
        int i, err = 0;

        if (!obj->btf)
                return 0;

        if (!kernel_supports(obj, FEAT_BTF)) {
                if (kernel_needs_btf(obj)) {
                        err = -EOPNOTSUPP;
                        goto report;
                }
                pr_debug("Kernel doesn't support BTF, skipping uploading it.\n");
                return 0;
        }

        /* Even though some subprogs are global/weak, user might prefer more
         * permissive BPF verification process that BPF verifier performs for
         * static functions, taking into account more context from the caller
         * functions. In such case, they need to mark such subprogs with
         * __attribute__((visibility("hidden"))) and libbpf will adjust
         * corresponding FUNC BTF type to be marked as static and trigger more
         * involved BPF verification process.
         */
        for (i = 0; i < obj->nr_programs; i++) {
                struct bpf_program *prog = &obj->programs[i];
                struct btf_type *t;
                const char *name;
                int j, n;

                if (!prog->mark_btf_static || !prog_is_subprog(obj, prog))
                        continue;

                n = btf__type_cnt(obj->btf);
                for (j = 1; j < n; j++) {
                        t = btf_type_by_id(obj->btf, j);
                        if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL)
                                continue;

                        name = btf__str_by_offset(obj->btf, t->name_off);
                        if (strcmp(name, prog->name) != 0)
                                continue;

                        t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0);
                        break;
                }
        }

        sanitize = btf_needs_sanitization(obj);
        if (sanitize) {
                const void *raw_data;
                __u32 sz;

                /* clone BTF to sanitize a copy and leave the original intact */
                raw_data = btf__raw_data(obj->btf, &sz);
                kern_btf = btf__new(raw_data, sz);
                err = libbpf_get_error(kern_btf);
                if (err)
                        return err;

                /* enforce 8-byte pointers for BPF-targeted BTFs */
                btf__set_pointer_size(obj->btf, 8);
                err = bpf_object__sanitize_btf(obj, kern_btf);
                if (err)
                        return err;
        }

        if (obj->gen_loader) {
                __u32 raw_size = 0;
                const void *raw_data = btf__raw_data(kern_btf, &raw_size);

                if (!raw_data)
                        return -ENOMEM;
                bpf_gen__load_btf(obj->gen_loader, raw_data, raw_size);
                /* Pretend to have valid FD to pass various fd >= 0 checks.
                 * This fd == 0 will not be used with any syscall and will be reset to -1 eventually.
                 */
                btf__set_fd(kern_btf, 0);
        } else {
                /* currently BPF_BTF_LOAD only supports log_level 1 */
                err = btf_load_into_kernel(kern_btf, obj->log_buf, obj->log_size,
                                           obj->log_level ? 1 : 0);
        }
        if (sanitize) {
                if (!err) {
                        /* move fd to libbpf's BTF */
                        btf__set_fd(obj->btf, btf__fd(kern_btf));
                        btf__set_fd(kern_btf, -1);
                }
                btf__free(kern_btf);
        }
report:
        if (err) {
                btf_mandatory = kernel_needs_btf(obj);
                pr_warn("Error loading .BTF into kernel: %d. %s\n", err,
                        btf_mandatory ? "BTF is mandatory, can't proceed."
                                      : "BTF is optional, ignoring.");
                if (!btf_mandatory)
                        err = 0;
        }
        return err;
}

static const char *elf_sym_str(const struct bpf_object *obj, size_t off)
{
        const char *name;

        name = elf_strptr(obj->efile.elf, obj->efile.strtabidx, off);
        if (!name) {
                pr_warn("elf: failed to get section name string at offset %zu from %s: %s\n",
                        off, obj->path, elf_errmsg(-1));
                return NULL;
        }

        return name;
}

static const char *elf_sec_str(const struct bpf_object *obj, size_t off)
{
        const char *name;

        name = elf_strptr(obj->efile.elf, obj->efile.shstrndx, off);
        if (!name) {
                pr_warn("elf: failed to get section name string at offset %zu from %s: %s\n",
                        off, obj->path, elf_errmsg(-1));
                return NULL;
        }

        return name;
}

static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx)
{
        Elf_Scn *scn;

        scn = elf_getscn(obj->efile.elf, idx);
        if (!scn) {
                pr_warn("elf: failed to get section(%zu) from %s: %s\n",
                        idx, obj->path, elf_errmsg(-1));
                return NULL;
        }
        return scn;
}

static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name)
{
        Elf_Scn *scn = NULL;
        Elf *elf = obj->efile.elf;
        const char *sec_name;

        while ((scn = elf_nextscn(elf, scn)) != NULL) {
                sec_name = elf_sec_name(obj, scn);
                if (!sec_name)
                        return NULL;

                if (strcmp(sec_name, name) != 0)
                        continue;

                return scn;
        }
        return NULL;
}

static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn)
{
        Elf64_Shdr *shdr;

        if (!scn)
                return NULL;

        shdr = elf64_getshdr(scn);
        if (!shdr) {
                pr_warn("elf: failed to get section(%zu) header from %s: %s\n",
                        elf_ndxscn(scn), obj->path, elf_errmsg(-1));
                return NULL;
        }

        return shdr;
}

static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn)
{
        const char *name;
        Elf64_Shdr *sh;

        if (!scn)
                return NULL;

        sh = elf_sec_hdr(obj, scn);
        if (!sh)
                return NULL;

        name = elf_sec_str(obj, sh->sh_name);
        if (!name) {
                pr_warn("elf: failed to get section(%zu) name from %s: %s\n",
                        elf_ndxscn(scn), obj->path, elf_errmsg(-1));
                return NULL;
        }

        return name;
}

static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn)
{
        Elf_Data *data;

        if (!scn)
                return NULL;

        data = elf_getdata(scn, 0);
        if (!data) {
                pr_warn("elf: failed to get section(%zu) %s data from %s: %s\n",
                        elf_ndxscn(scn), elf_sec_name(obj, scn) ?: "<?>",
                        obj->path, elf_errmsg(-1));
                return NULL;
        }

        return data;
}

static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx)
{
        if (idx >= obj->efile.symbols->d_size / sizeof(Elf64_Sym))
                return NULL;

        return (Elf64_Sym *)obj->efile.symbols->d_buf + idx;
}

static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx)
{
        if (idx >= data->d_size / sizeof(Elf64_Rel))
                return NULL;

        return (Elf64_Rel *)data->d_buf + idx;
}

static bool is_sec_name_dwarf(const char *name)
{
        /* approximation, but the actual list is too long */
        return str_has_pfx(name, ".debug_");
}

static bool ignore_elf_section(Elf64_Shdr *hdr, const char *name)
{
        /* no special handling of .strtab */
        if (hdr->sh_type == SHT_STRTAB)
                return true;

        /* ignore .llvm_addrsig section as well */
        if (hdr->sh_type == SHT_LLVM_ADDRSIG)
                return true;

        /* no subprograms will lead to an empty .text section, ignore it */
        if (hdr->sh_type == SHT_PROGBITS && hdr->sh_size == 0 &&
            strcmp(name, ".text") == 0)
                return true;

        /* DWARF sections */
        if (is_sec_name_dwarf(name))
                return true;

        if (str_has_pfx(name, ".rel")) {
                name += sizeof(".rel") - 1;
                /* DWARF section relocations */
                if (is_sec_name_dwarf(name))
                        return true;

                /* .BTF and .BTF.ext don't need relocations */
                if (strcmp(name, BTF_ELF_SEC) == 0 ||
                    strcmp(name, BTF_EXT_ELF_SEC) == 0)
                        return true;
        }

        return false;
}

static int cmp_progs(const void *_a, const void *_b)
{
        const struct bpf_program *a = _a;
        const struct bpf_program *b = _b;

        if (a->sec_idx != b->sec_idx)
                return a->sec_idx < b->sec_idx ? -1 : 1;

        /* sec_insn_off can't be the same within the section */
        return a->sec_insn_off < b->sec_insn_off ? -1 : 1;
}

static int bpf_object__elf_collect(struct bpf_object *obj)
{
        struct elf_sec_desc *sec_desc;
        Elf *elf = obj->efile.elf;
        Elf_Data *btf_ext_data = NULL;
        Elf_Data *btf_data = NULL;
        int idx = 0, err = 0;
        const char *name;
        Elf_Data *data;
        Elf_Scn *scn;
        Elf64_Shdr *sh;

        /* ELF section indices are 0-based, but sec #0 is special "invalid"
         * section. Since section count retrieved by elf_getshdrnum() does
         * include sec #0, it is already the necessary size of an array to keep
         * all the sections.
         */
        if (elf_getshdrnum(obj->efile.elf, &obj->efile.sec_cnt)) {
                pr_warn("elf: failed to get the number of sections for %s: %s\n",
                        obj->path, elf_errmsg(-1));
                return -LIBBPF_ERRNO__FORMAT;
        }
        obj->efile.secs = calloc(obj->efile.sec_cnt, sizeof(*obj->efile.secs));
        if (!obj->efile.secs)
                return -ENOMEM;

        /* a bunch of ELF parsing functionality depends on processing symbols,
         * so do the first pass and find the symbol table
         */
        scn = NULL;
        while ((scn = elf_nextscn(elf, scn)) != NULL) {
                sh = elf_sec_hdr(obj, scn);
                if (!sh)
                        return -LIBBPF_ERRNO__FORMAT;

                if (sh->sh_type == SHT_SYMTAB) {
                        if (obj->efile.symbols) {
                                pr_warn("elf: multiple symbol tables in %s\n", obj->path);
                                return -LIBBPF_ERRNO__FORMAT;
                        }

                        data = elf_sec_data(obj, scn);
                        if (!data)
                                return -LIBBPF_ERRNO__FORMAT;

                        idx = elf_ndxscn(scn);

                        obj->efile.symbols = data;
                        obj->efile.symbols_shndx = idx;
                        obj->efile.strtabidx = sh->sh_link;
                }
        }

        if (!obj->efile.symbols) {
                pr_warn("elf: couldn't find symbol table in %s, stripped object file?\n",
                        obj->path);
                return -ENOENT;
        }

        scn = NULL;
        while ((scn = elf_nextscn(elf, scn)) != NULL) {
                idx = elf_ndxscn(scn);
                sec_desc = &obj->efile.secs[idx];

                sh = elf_sec_hdr(obj, scn);
                if (!sh)
                        return -LIBBPF_ERRNO__FORMAT;

                name = elf_sec_str(obj, sh->sh_name);
                if (!name)
                        return -LIBBPF_ERRNO__FORMAT;

                if (ignore_elf_section(sh, name))
                        continue;

                data = elf_sec_data(obj, scn);
                if (!data)
                        return -LIBBPF_ERRNO__FORMAT;

                pr_debug("elf: section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
                         idx, name, (unsigned long)data->d_size,
                         (int)sh->sh_link, (unsigned long)sh->sh_flags,
                         (int)sh->sh_type);

                if (strcmp(name, "license") == 0) {
                        err = bpf_object__init_license(obj, data->d_buf, data->d_size);
                        if (err)
                                return err;
                } else if (strcmp(name, "version") == 0) {
                        err = bpf_object__init_kversion(obj, data->d_buf, data->d_size);
                        if (err)
                                return err;
                } else if (strcmp(name, "maps") == 0) {
                        pr_warn("elf: legacy map definitions in 'maps' section are not supported by libbpf v1.0+\n");
                        return -ENOTSUP;
                } else if (strcmp(name, MAPS_ELF_SEC) == 0) {
                        obj->efile.btf_maps_shndx = idx;
                } else if (strcmp(name, BTF_ELF_SEC) == 0) {
                        if (sh->sh_type != SHT_PROGBITS)
                                return -LIBBPF_ERRNO__FORMAT;
                        btf_data = data;
                } else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
                        if (sh->sh_type != SHT_PROGBITS)
                                return -LIBBPF_ERRNO__FORMAT;
                        btf_ext_data = data;
                } else if (sh->sh_type == SHT_SYMTAB) {
                        /* already processed during the first pass above */
                } else if (sh->sh_type == SHT_PROGBITS && data->d_size > 0) {
                        if (sh->sh_flags & SHF_EXECINSTR) {
                                if (strcmp(name, ".text") == 0)
                                        obj->efile.text_shndx = idx;
                                err = bpf_object__add_programs(obj, data, name, idx);
                                if (err)
                                        return err;
                        } else if (strcmp(name, DATA_SEC) == 0 ||
                                   str_has_pfx(name, DATA_SEC ".")) {
                                sec_desc->sec_type = SEC_DATA;
                                sec_desc->shdr = sh;
                                sec_desc->data = data;
                        } else if (strcmp(name, RODATA_SEC) == 0 ||
                                   str_has_pfx(name, RODATA_SEC ".")) {
                                sec_desc->sec_type = SEC_RODATA;
                                sec_desc->shdr = sh;
                                sec_desc->data = data;
                        } else if (strcmp(name, STRUCT_OPS_SEC) == 0) {
                                obj->efile.st_ops_data = data;
                                obj->efile.st_ops_shndx = idx;
                        } else if (strcmp(name, STRUCT_OPS_LINK_SEC) == 0) {
                                obj->efile.st_ops_link_data = data;
                                obj->efile.st_ops_link_shndx = idx;
                        } else {
                                pr_info("elf: skipping unrecognized data section(%d) %s\n",
                                        idx, name);
                        }
                } else if (sh->sh_type == SHT_REL) {
                        int targ_sec_idx = sh->sh_info; /* points to other section */

                        if (sh->sh_entsize != sizeof(Elf64_Rel) ||
                            targ_sec_idx >= obj->efile.sec_cnt)
                                return -LIBBPF_ERRNO__FORMAT;

                        /* Only do relo for section with exec instructions */
                        if (!section_have_execinstr(obj, targ_sec_idx) &&
                            strcmp(name, ".rel" STRUCT_OPS_SEC) &&
                            strcmp(name, ".rel" STRUCT_OPS_LINK_SEC) &&
                            strcmp(name, ".rel" MAPS_ELF_SEC)) {
                                pr_info("elf: skipping relo section(%d) %s for section(%d) %s\n",
                                        idx, name, targ_sec_idx,
                                        elf_sec_name(obj, elf_sec_by_idx(obj, targ_sec_idx)) ?: "<?>");
                                continue;
                        }

                        sec_desc->sec_type = SEC_RELO;
                        sec_desc->shdr = sh;
                        sec_desc->data = data;
                } else if (sh->sh_type == SHT_NOBITS && (strcmp(name, BSS_SEC) == 0 ||
                                                         str_has_pfx(name, BSS_SEC "."))) {
                        sec_desc->sec_type = SEC_BSS;
                        sec_desc->shdr = sh;
                        sec_desc->data = data;
                } else {
                        pr_info("elf: skipping section(%d) %s (size %zu)\n", idx, name,
                                (size_t)sh->sh_size);
                }
        }

        if (!obj->efile.strtabidx || obj->efile.strtabidx > idx) {
                pr_warn("elf: symbol strings section missing or invalid in %s\n", obj->path);
                return -LIBBPF_ERRNO__FORMAT;
        }

        /* sort BPF programs by section name and in-section instruction offset
         * for faster search
         */
        if (obj->nr_programs)
                qsort(obj->programs, obj->nr_programs, sizeof(*obj->programs), cmp_progs);

        return bpf_object__init_btf(obj, btf_data, btf_ext_data);
}

static bool sym_is_extern(const Elf64_Sym *sym)
{
        int bind = ELF64_ST_BIND(sym->st_info);
        /* externs are symbols w/ type=NOTYPE, bind=GLOBAL|WEAK, section=UND */
        return sym->st_shndx == SHN_UNDEF &&
               (bind == STB_GLOBAL || bind == STB_WEAK) &&
               ELF64_ST_TYPE(sym->st_info) == STT_NOTYPE;
}

static bool sym_is_subprog(const Elf64_Sym *sym, int text_shndx)
{
        int bind = ELF64_ST_BIND(sym->st_info);
        int type = ELF64_ST_TYPE(sym->st_info);

        /* in .text section */
        if (sym->st_shndx != text_shndx)
                return false;

        /* local function */
        if (bind == STB_LOCAL && type == STT_SECTION)
                return true;

        /* global function */
        return bind == STB_GLOBAL && type == STT_FUNC;
}

static int find_extern_btf_id(const struct btf *btf, const char *ext_name)
{
        const struct btf_type *t;
        const char *tname;
        int i, n;

        if (!btf)
                return -ESRCH;

        n = btf__type_cnt(btf);
        for (i = 1; i < n; i++) {
                t = btf__type_by_id(btf, i);

                if (!btf_is_var(t) && !btf_is_func(t))
                        continue;

                tname = btf__name_by_offset(btf, t->name_off);
                if (strcmp(tname, ext_name))
                        continue;

                if (btf_is_var(t) &&
                    btf_var(t)->linkage != BTF_VAR_GLOBAL_EXTERN)
                        return -EINVAL;

                if (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_EXTERN)
                        return -EINVAL;

                return i;
        }

        return -ENOENT;
}

static int find_extern_sec_btf_id(struct btf *btf, int ext_btf_id) {
        const struct btf_var_secinfo *vs;
        const struct btf_type *t;
        int i, j, n;

        if (!btf)
                return -ESRCH;

        n = btf__type_cnt(btf);
        for (i = 1; i < n; i++) {
                t = btf__type_by_id(btf, i);

                if (!btf_is_datasec(t))
                        continue;

                vs = btf_var_secinfos(t);
                for (j = 0; j < btf_vlen(t); j++, vs++) {
                        if (vs->type == ext_btf_id)
                                return i;
                }
        }

        return -ENOENT;
}

static enum kcfg_type find_kcfg_type(const struct btf *btf, int id,
                                     bool *is_signed)
{
        const struct btf_type *t;
        const char *name;

        t = skip_mods_and_typedefs(btf, id, NULL);
        name = btf__name_by_offset(btf, t->name_off);

        if (is_signed)
                *is_signed = false;
        switch (btf_kind(t)) {
        case BTF_KIND_INT: {
                int enc = btf_int_encoding(t);

                if (enc & BTF_INT_BOOL)
                        return t->size == 1 ? KCFG_BOOL : KCFG_UNKNOWN;
                if (is_signed)
                        *is_signed = enc & BTF_INT_SIGNED;
                if (t->size == 1)
                        return KCFG_CHAR;
                if (t->size < 1 || t->size > 8 || (t->size & (t->size - 1)))
                        return KCFG_UNKNOWN;
                return KCFG_INT;
        }
        case BTF_KIND_ENUM:
                if (t->size != 4)
                        return KCFG_UNKNOWN;
                if (strcmp(name, "libbpf_tristate"))
                        return KCFG_UNKNOWN;
                return KCFG_TRISTATE;
        case BTF_KIND_ENUM64:
                if (strcmp(name, "libbpf_tristate"))
                        return KCFG_UNKNOWN;
                return KCFG_TRISTATE;
        case BTF_KIND_ARRAY:
                if (btf_array(t)->nelems == 0)
                        return KCFG_UNKNOWN;
                if (find_kcfg_type(btf, btf_array(t)->type, NULL) != KCFG_CHAR)
                        return KCFG_UNKNOWN;
                return KCFG_CHAR_ARR;
        default:
                return KCFG_UNKNOWN;
        }
}

static int cmp_externs(const void *_a, const void *_b)
{
        const struct extern_desc *a = _a;
        const struct extern_desc *b = _b;

        if (a->type != b->type)
                return a->type < b->type ? -1 : 1;

        if (a->type == EXT_KCFG) {
                /* descending order by alignment requirements */
                if (a->kcfg.align != b->kcfg.align)
                        return a->kcfg.align > b->kcfg.align ? -1 : 1;
                /* ascending order by size, within same alignment class */
                if (a->kcfg.sz != b->kcfg.sz)
                        return a->kcfg.sz < b->kcfg.sz ? -1 : 1;
        }

        /* resolve ties by name */
        return strcmp(a->name, b->name);
}

static int find_int_btf_id(const struct btf *btf)
{
        const struct btf_type *t;
        int i, n;

        n = btf__type_cnt(btf);
        for (i = 1; i < n; i++) {
                t = btf__type_by_id(btf, i);

                if (btf_is_int(t) && btf_int_bits(t) == 32)
                        return i;
        }

        return 0;
}

static int add_dummy_ksym_var(struct btf *btf)
{
        int i, int_btf_id, sec_btf_id, dummy_var_btf_id;
        const struct btf_var_secinfo *vs;
        const struct btf_type *sec;

        if (!btf)
                return 0;

        sec_btf_id = btf__find_by_name_kind(btf, KSYMS_SEC,
                                            BTF_KIND_DATASEC);
        if (sec_btf_id < 0)
                return 0;

        sec = btf__type_by_id(btf, sec_btf_id);
        vs = btf_var_secinfos(sec);
        for (i = 0; i < btf_vlen(sec); i++, vs++) {
                const struct btf_type *vt;

                vt = btf__type_by_id(btf, vs->type);
                if (btf_is_func(vt))
                        break;
        }

        /* No func in ksyms sec.  No need to add dummy var. */
        if (i == btf_vlen(sec))
                return 0;

        int_btf_id = find_int_btf_id(btf);
        dummy_var_btf_id = btf__add_var(btf,
                                        "dummy_ksym",
                                        BTF_VAR_GLOBAL_ALLOCATED,
                                        int_btf_id);
        if (dummy_var_btf_id < 0)
                pr_warn("cannot create a dummy_ksym var\n");

        return dummy_var_btf_id;
}

static int bpf_object__collect_externs(struct bpf_object *obj)
{
        struct btf_type *sec, *kcfg_sec = NULL, *ksym_sec = NULL;
        const struct btf_type *t;
        struct extern_desc *ext;
        int i, n, off, dummy_var_btf_id;
        const char *ext_name, *sec_name;
        Elf_Scn *scn;
        Elf64_Shdr *sh;

        if (!obj->efile.symbols)
                return 0;

        scn = elf_sec_by_idx(obj, obj->efile.symbols_shndx);
        sh = elf_sec_hdr(obj, scn);
        if (!sh || sh->sh_entsize != sizeof(Elf64_Sym))
                return -LIBBPF_ERRNO__FORMAT;

        dummy_var_btf_id = add_dummy_ksym_var(obj->btf);
        if (dummy_var_btf_id < 0)
                return dummy_var_btf_id;

        n = sh->sh_size / sh->sh_entsize;
        pr_debug("looking for externs among %d symbols...\n", n);

        for (i = 0; i < n; i++) {
                Elf64_Sym *sym = elf_sym_by_idx(obj, i);

                if (!sym)
                        return -LIBBPF_ERRNO__FORMAT;
                if (!sym_is_extern(sym))
                        continue;
                ext_name = elf_sym_str(obj, sym->st_name);
                if (!ext_name || !ext_name[0])
                        continue;

                ext = obj->externs;
                ext = libbpf_reallocarray(ext, obj->nr_extern + 1, sizeof(*ext));
                if (!ext)
                        return -ENOMEM;
                obj->externs = ext;
                ext = &ext[obj->nr_extern];
                memset(ext, 0, sizeof(*ext));
                obj->nr_extern++;

                ext->btf_id = find_extern_btf_id(obj->btf, ext_name);
                if (ext->btf_id <= 0) {
                        pr_warn("failed to find BTF for extern '%s': %d\n",
                                ext_name, ext->btf_id);
                        return ext->btf_id;
                }
                t = btf__type_by_id(obj->btf, ext->btf_id);
                ext->name = btf__name_by_offset(obj->btf, t->name_off);
                ext->sym_idx = i;
                ext->is_weak = ELF64_ST_BIND(sym->st_info) == STB_WEAK;

                ext->sec_btf_id = find_extern_sec_btf_id(obj->btf, ext->btf_id);
                if (ext->sec_btf_id <= 0) {
                        pr_warn("failed to find BTF for extern '%s' [%d] section: %d\n",
                                ext_name, ext->btf_id, ext->sec_btf_id);
                        return ext->sec_btf_id;
                }
                sec = (void *)btf__type_by_id(obj->btf, ext->sec_btf_id);
                sec_name = btf__name_by_offset(obj->btf, sec->name_off);

                if (strcmp(sec_name, KCONFIG_SEC) == 0) {
                        if (btf_is_func(t)) {
                                pr_warn("extern function %s is unsupported under %s section\n",
                                        ext->name, KCONFIG_SEC);
                                return -ENOTSUP;
                        }
                        kcfg_sec = sec;
                        ext->type = EXT_KCFG;
                        ext->kcfg.sz = btf__resolve_size(obj->btf, t->type);
                        if (ext->kcfg.sz <= 0) {
                                pr_warn("failed to resolve size of extern (kcfg) '%s': %d\n",
                                        ext_name, ext->kcfg.sz);
                                return ext->kcfg.sz;
                        }
                        ext->kcfg.align = btf__align_of(obj->btf, t->type);
                        if (ext->kcfg.align <= 0) {
                                pr_warn("failed to determine alignment of extern (kcfg) '%s': %d\n",
                                        ext_name, ext->kcfg.align);
                                return -EINVAL;
                        }
                        ext->kcfg.type = find_kcfg_type(obj->btf, t->type,
                                                        &ext->kcfg.is_signed);
                        if (ext->kcfg.type == KCFG_UNKNOWN) {
                                pr_warn("extern (kcfg) '%s': type is unsupported\n", ext_name);
                                return -ENOTSUP;
                        }
                } else if (strcmp(sec_name, KSYMS_SEC) == 0) {
                        ksym_sec = sec;
                        ext->type = EXT_KSYM;
                        skip_mods_and_typedefs(obj->btf, t->type,
                                               &ext->ksym.type_id);
                } else {
                        pr_warn("unrecognized extern section '%s'\n", sec_name);
                        return -ENOTSUP;
                }
        }
        pr_debug("collected %d externs total\n", obj->nr_extern);

        if (!obj->nr_extern)
                return 0;

        /* sort externs by type, for kcfg ones also by (align, size, name) */
        qsort(obj->externs, obj->nr_extern, sizeof(*ext), cmp_externs);

        /* for .ksyms section, we need to turn all externs into allocated
         * variables in BTF to pass kernel verification; we do this by
         * pretending that each extern is a 8-byte variable
         */
        if (ksym_sec) {
                /* find existing 4-byte integer type in BTF to use for fake
                 * extern variables in DATASEC
                 */
                int int_btf_id = find_int_btf_id(obj->btf);
                /* For extern function, a dummy_var added earlier
                 * will be used to replace the vs->type and
                 * its name string will be used to refill
                 * the missing param's name.
                 */
                const struct btf_type *dummy_var;

                dummy_var = btf__type_by_id(obj->btf, dummy_var_btf_id);
                for (i = 0; i < obj->nr_extern; i++) {
                        ext = &obj->externs[i];
                        if (ext->type != EXT_KSYM)
                                continue;
                        pr_debug("extern (ksym) #%d: symbol %d, name %s\n",
                                 i, ext->sym_idx, ext->name);
                }

                sec = ksym_sec;
                n = btf_vlen(sec);
                for (i = 0, off = 0; i < n; i++, off += sizeof(int)) {
                        struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i;
                        struct btf_type *vt;

                        vt = (void *)btf__type_by_id(obj->btf, vs->type);
                        ext_name = btf__name_by_offset(obj->btf, vt->name_off);
                        ext = find_extern_by_name(obj, ext_name);
                        if (!ext) {
                                pr_warn("failed to find extern definition for BTF %s '%s'\n",
                                        btf_kind_str(vt), ext_name);
                                return -ESRCH;
                        }
                        if (btf_is_func(vt)) {
                                const struct btf_type *func_proto;
                                struct btf_param *param;
                                int j;

                                func_proto = btf__type_by_id(obj->btf,
                                                             vt->type);
                                param = btf_params(func_proto);
                                /* Reuse the dummy_var string if the
                                 * func proto does not have param name.
                                 */
                                for (j = 0; j < btf_vlen(func_proto); j++)
                                        if (param[j].type && !param[j].name_off)
                                                param[j].name_off =
                                                        dummy_var->name_off;
                                vs->type = dummy_var_btf_id;
                                vt->info &= ~0xffff;
                                vt->info |= BTF_FUNC_GLOBAL;
                        } else {
                                btf_var(vt)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
                                vt->type = int_btf_id;
                        }
                        vs->offset = off;
                        vs->size = sizeof(int);
                }
                sec->size = off;
        }

        if (kcfg_sec) {
                sec = kcfg_sec;
                /* for kcfg externs calculate their offsets within a .kconfig map */
                off = 0;
                for (i = 0; i < obj->nr_extern; i++) {
                        ext = &obj->externs[i];
                        if (ext->type != EXT_KCFG)
                                continue;

                        ext->kcfg.data_off = roundup(off, ext->kcfg.align);
                        off = ext->kcfg.data_off + ext->kcfg.sz;
                        pr_debug("extern (kcfg) #%d: symbol %d, off %u, name %s\n",
                                 i, ext->sym_idx, ext->kcfg.data_off, ext->name);
                }
                sec->size = off;
                n = btf_vlen(sec);
                for (i = 0; i < n; i++) {
                        struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i;

                        t = btf__type_by_id(obj->btf, vs->type);
                        ext_name = btf__name_by_offset(obj->btf, t->name_off);
                        ext = find_extern_by_name(obj, ext_name);
                        if (!ext) {
                                pr_warn("failed to find extern definition for BTF var '%s'\n",
                                        ext_name);
                                return -ESRCH;
                        }
                        btf_var(t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
                        vs->offset = ext->kcfg.data_off;
                }
        }
        return 0;
}

static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog)
{
        return prog->sec_idx == obj->efile.text_shndx && obj->nr_programs > 1;
}

struct bpf_program *
bpf_object__find_program_by_name(const struct bpf_object *obj,
                                 const char *name)
{
        struct bpf_program *prog;

        bpf_object__for_each_program(prog, obj) {
                if (prog_is_subprog(obj, prog))
                        continue;
                if (!strcmp(prog->name, name))
                        return prog;
        }
        return errno = ENOENT, NULL;
}

static bool bpf_object__shndx_is_data(const struct bpf_object *obj,
                                      int shndx)
{
        switch (obj->efile.secs[shndx].sec_type) {
        case SEC_BSS:
        case SEC_DATA:
        case SEC_RODATA:
                return true;
        default:
                return false;
        }
}

static bool bpf_object__shndx_is_maps(const struct bpf_object *obj,
                                      int shndx)
{
        return shndx == obj->efile.btf_maps_shndx;
}

static enum libbpf_map_type
bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx)
{
        if (shndx == obj->efile.symbols_shndx)
                return LIBBPF_MAP_KCONFIG;

        switch (obj->efile.secs[shndx].sec_type) {
        case SEC_BSS:
                return LIBBPF_MAP_BSS;
        case SEC_DATA:
                return LIBBPF_MAP_DATA;
        case SEC_RODATA:
                return LIBBPF_MAP_RODATA;
        default:
                return LIBBPF_MAP_UNSPEC;
        }
}

static int bpf_program__record_reloc(struct bpf_program *prog,
                                     struct reloc_desc *reloc_desc,
                                     __u32 insn_idx, const char *sym_name,
                                     const Elf64_Sym *sym, const Elf64_Rel *rel)
{
        struct bpf_insn *insn = &prog->insns[insn_idx];
        size_t map_idx, nr_maps = prog->obj->nr_maps;
        struct bpf_object *obj = prog->obj;
        __u32 shdr_idx = sym->st_shndx;
        enum libbpf_map_type type;
        const char *sym_sec_name;
        struct bpf_map *map;

        if (!is_call_insn(insn) && !is_ldimm64_insn(insn)) {
                pr_warn("prog '%s': invalid relo against '%s' for insns[%d].code 0x%x\n",
                        prog->name, sym_name, insn_idx, insn->code);
                return -LIBBPF_ERRNO__RELOC;
        }

        if (sym_is_extern(sym)) {
                int sym_idx = ELF64_R_SYM(rel->r_info);
                int i, n = obj->nr_extern;
                struct extern_desc *ext;

                for (i = 0; i < n; i++) {
                        ext = &obj->externs[i];
                        if (ext->sym_idx == sym_idx)
                                break;
                }
                if (i >= n) {
                        pr_warn("prog '%s': extern relo failed to find extern for '%s' (%d)\n",
                                prog->name, sym_name, sym_idx);
                        return -LIBBPF_ERRNO__RELOC;
                }
                pr_debug("prog '%s': found extern #%d '%s' (sym %d) for insn #%u\n",
                         prog->name, i, ext->name, ext->sym_idx, insn_idx);
                if (insn->code == (BPF_JMP | BPF_CALL))
                        reloc_desc->type = RELO_EXTERN_CALL;
                else
                        reloc_desc->type = RELO_EXTERN_LD64;
                reloc_desc->insn_idx = insn_idx;
                reloc_desc->ext_idx = i;
                return 0;
        }

        /* sub-program call relocation */
        if (is_call_insn(insn)) {
                if (insn->src_reg != BPF_PSEUDO_CALL) {
                        pr_warn("prog '%s': incorrect bpf_call opcode\n", prog->name);
                        return -LIBBPF_ERRNO__RELOC;
                }
                /* text_shndx can be 0, if no default "main" program exists */
                if (!shdr_idx || shdr_idx != obj->efile.text_shndx) {
                        sym_sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, shdr_idx));
                        pr_warn("prog '%s': bad call relo against '%s' in section '%s'\n",
                                prog->name, sym_name, sym_sec_name);
                        return -LIBBPF_ERRNO__RELOC;
                }
                if (sym->st_value % BPF_INSN_SZ) {
                        pr_warn("prog '%s': bad call relo against '%s' at offset %zu\n",
                                prog->name, sym_name, (size_t)sym->st_value);
                        return -LIBBPF_ERRNO__RELOC;
                }
                reloc_desc->type = RELO_CALL;
                reloc_desc->insn_idx = insn_idx;
                reloc_desc->sym_off = sym->st_value;
                return 0;
        }

        if (!shdr_idx || shdr_idx >= SHN_LORESERVE) {
                pr_warn("prog '%s': invalid relo against '%s' in special section 0x%x; forgot to initialize global var?..\n",
                        prog->name, sym_name, shdr_idx);
                return -LIBBPF_ERRNO__RELOC;
        }

        /* loading subprog addresses */
        if (sym_is_subprog(sym, obj->efile.text_shndx)) {
                /* global_func: sym->st_value = offset in the section, insn->imm = 0.
                 * local_func: sym->st_value = 0, insn->imm = offset in the section.
                 */
                if ((sym->st_value % BPF_INSN_SZ) || (insn->imm % BPF_INSN_SZ)) {
                        pr_warn("prog '%s': bad subprog addr relo against '%s' at offset %zu+%d\n",
                                prog->name, sym_name, (size_t)sym->st_value, insn->imm);
                        return -LIBBPF_ERRNO__RELOC;
                }

                reloc_desc->type = RELO_SUBPROG_ADDR;
                reloc_desc->insn_idx = insn_idx;
                reloc_desc->sym_off = sym->st_value;
                return 0;
        }

        type = bpf_object__section_to_libbpf_map_type(obj, shdr_idx);
        sym_sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, shdr_idx));

        /* generic map reference relocation */
        if (type == LIBBPF_MAP_UNSPEC) {
                if (!bpf_object__shndx_is_maps(obj, shdr_idx)) {
                        pr_warn("prog '%s': bad map relo against '%s' in section '%s'\n",
                                prog->name, sym_name, sym_sec_name);
                        return -LIBBPF_ERRNO__RELOC;
                }
                for (map_idx = 0; map_idx < nr_maps; map_idx++) {
                        map = &obj->maps[map_idx];
                        if (map->libbpf_type != type ||
                            map->sec_idx != sym->st_shndx ||
                            map->sec_offset != sym->st_value)
                                continue;
                        pr_debug("prog '%s': found map %zd (%s, sec %d, off %zu) for insn #%u\n",
                                 prog->name, map_idx, map->name, map->sec_idx,
                                 map->sec_offset, insn_idx);
                        break;
                }
                if (map_idx >= nr_maps) {
                        pr_warn("prog '%s': map relo failed to find map for section '%s', off %zu\n",
                                prog->name, sym_sec_name, (size_t)sym->st_value);
                        return -LIBBPF_ERRNO__RELOC;
                }
                reloc_desc->type = RELO_LD64;
                reloc_desc->insn_idx = insn_idx;
                reloc_desc->map_idx = map_idx;
                reloc_desc->sym_off = 0; /* sym->st_value determines map_idx */
                return 0;
        }

        /* global data map relocation */
        if (!bpf_object__shndx_is_data(obj, shdr_idx)) {
                pr_warn("prog '%s': bad data relo against section '%s'\n",
                        prog->name, sym_sec_name);
                return -LIBBPF_ERRNO__RELOC;
        }
        for (map_idx = 0; map_idx < nr_maps; map_idx++) {
                map = &obj->maps[map_idx];
                if (map->libbpf_type != type || map->sec_idx != sym->st_shndx)
                        continue;
                pr_debug("prog '%s': found data map %zd (%s, sec %d, off %zu) for insn %u\n",
                         prog->name, map_idx, map->name, map->sec_idx,
                         map->sec_offset, insn_idx);
                break;
        }
        if (map_idx >= nr_maps) {
                pr_warn("prog '%s': data relo failed to find map for section '%s'\n",
                        prog->name, sym_sec_name);
                return -LIBBPF_ERRNO__RELOC;
        }

        reloc_desc->type = RELO_DATA;
        reloc_desc->insn_idx = insn_idx;
        reloc_desc->map_idx = map_idx;
        reloc_desc->sym_off = sym->st_value;
        return 0;
}

static bool prog_contains_insn(const struct bpf_program *prog, size_t insn_idx)
{
        return insn_idx >= prog->sec_insn_off &&
               insn_idx < prog->sec_insn_off + prog->sec_insn_cnt;
}

static struct bpf_program *find_prog_by_sec_insn(const struct bpf_object *obj,
                                                 size_t sec_idx, size_t insn_idx)
{
        int l = 0, r = obj->nr_programs - 1, m;
        struct bpf_program *prog;

        if (!obj->nr_programs)
                return NULL;

        while (l < r) {
                m = l + (r - l + 1) / 2;
                prog = &obj->programs[m];

                if (prog->sec_idx < sec_idx ||
                    (prog->sec_idx == sec_idx && prog->sec_insn_off <= insn_idx))
                        l = m;
                else
                        r = m - 1;
        }
        /* matching program could be at index l, but it still might be the
         * wrong one, so we need to double check conditions for the last time
         */
        prog = &obj->programs[l];
        if (prog->sec_idx == sec_idx && prog_contains_insn(prog, insn_idx))
                return prog;
        return NULL;
}

static int
bpf_object__collect_prog_relos(struct bpf_object *obj, Elf64_Shdr *shdr, Elf_Data *data)
{
        const char *relo_sec_name, *sec_name;
        size_t sec_idx = shdr->sh_info, sym_idx;
        struct bpf_program *prog;
        struct reloc_desc *relos;
        int err, i, nrels;
        const char *sym_name;
        __u32 insn_idx;
        Elf_Scn *scn;
        Elf_Data *scn_data;
        Elf64_Sym *sym;
        Elf64_Rel *rel;

        if (sec_idx >= obj->efile.sec_cnt)
                return -EINVAL;

        scn = elf_sec_by_idx(obj, sec_idx);
        scn_data = elf_sec_data(obj, scn);

        relo_sec_name = elf_sec_str(obj, shdr->sh_name);
        sec_name = elf_sec_name(obj, scn);
        if (!relo_sec_name || !sec_name)
                return -EINVAL;

        pr_debug("sec '%s': collecting relocation for section(%zu) '%s'\n",
                 relo_sec_name, sec_idx, sec_name);
        nrels = shdr->sh_size / shdr->sh_entsize;

        for (i = 0; i < nrels; i++) {
                rel = elf_rel_by_idx(data, i);
                if (!rel) {
                        pr_warn("sec '%s': failed to get relo #%d\n", relo_sec_name, i);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                sym_idx = ELF64_R_SYM(rel->r_info);
                sym = elf_sym_by_idx(obj, sym_idx);
                if (!sym) {
                        pr_warn("sec '%s': symbol #%zu not found for relo #%d\n",
                                relo_sec_name, sym_idx, i);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                if (sym->st_shndx >= obj->efile.sec_cnt) {
                        pr_warn("sec '%s': corrupted symbol #%zu pointing to invalid section #%zu for relo #%d\n",
                                relo_sec_name, sym_idx, (size_t)sym->st_shndx, i);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                if (rel->r_offset % BPF_INSN_SZ || rel->r_offset >= scn_data->d_size) {
                        pr_warn("sec '%s': invalid offset 0x%zx for relo #%d\n",
                                relo_sec_name, (size_t)rel->r_offset, i);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                insn_idx = rel->r_offset / BPF_INSN_SZ;
                /* relocations against static functions are recorded as
                 * relocations against the section that contains a function;
                 * in such case, symbol will be STT_SECTION and sym.st_name
                 * will point to empty string (0), so fetch section name
                 * instead
                 */
                if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && sym->st_name == 0)
                        sym_name = elf_sec_name(obj, elf_sec_by_idx(obj, sym->st_shndx));
                else
                        sym_name = elf_sym_str(obj, sym->st_name);
                sym_name = sym_name ?: "<?";

                pr_debug("sec '%s': relo #%d: insn #%u against '%s'\n",
                         relo_sec_name, i, insn_idx, sym_name);

                prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx);
                if (!prog) {
                        pr_debug("sec '%s': relo #%d: couldn't find program in section '%s' for insn #%u, probably overridden weak function, skipping...\n",
                                relo_sec_name, i, sec_name, insn_idx);
                        continue;
                }

                relos = libbpf_reallocarray(prog->reloc_desc,
                                            prog->nr_reloc + 1, sizeof(*relos));
                if (!relos)
                        return -ENOMEM;
                prog->reloc_desc = relos;

                /* adjust insn_idx to local BPF program frame of reference */
                insn_idx -= prog->sec_insn_off;
                err = bpf_program__record_reloc(prog, &relos[prog->nr_reloc],
                                                insn_idx, sym_name, sym, rel);
                if (err)
                        return err;

                prog->nr_reloc++;
        }
        return 0;
}

static int map_fill_btf_type_info(struct bpf_object *obj, struct bpf_map *map)
{
        int id;

        if (!obj->btf)
                return -ENOENT;

        /* if it's BTF-defined map, we don't need to search for type IDs.
         * For struct_ops map, it does not need btf_key_type_id and
         * btf_value_type_id.
         */
        if (map->sec_idx == obj->efile.btf_maps_shndx || bpf_map__is_struct_ops(map))
                return 0;

        /*
         * LLVM annotates global data differently in BTF, that is,
         * only as '.data', '.bss' or '.rodata'.
         */
        if (!bpf_map__is_internal(map))
                return -ENOENT;

        id = btf__find_by_name(obj->btf, map->real_name);
        if (id < 0)
                return id;

        map->btf_key_type_id = 0;
        map->btf_value_type_id = id;
        return 0;
}

static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
{
        char file[PATH_MAX], buff[4096];
        FILE *fp;
        __u32 val;
        int err;

        snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
        memset(info, 0, sizeof(*info));

        fp = fopen(file, "r");
        if (!fp) {
                err = -errno;
                pr_warn("failed to open %s: %d. No procfs support?\n", file,
                        err);
                return err;
        }

        while (fgets(buff, sizeof(buff), fp)) {
                if (sscanf(buff, "map_type:\t%u", &val) == 1)
                        info->type = val;
                else if (sscanf(buff, "key_size:\t%u", &val) == 1)
                        info->key_size = val;
                else if (sscanf(buff, "value_size:\t%u", &val) == 1)
                        info->value_size = val;
                else if (sscanf(buff, "max_entries:\t%u", &val) == 1)
                        info->max_entries = val;
                else if (sscanf(buff, "map_flags:\t%i", &val) == 1)
                        info->map_flags = val;
        }

        fclose(fp);

        return 0;
}

bool bpf_map__autocreate(const struct bpf_map *map)
{
        return map->autocreate;
}

int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate)
{
        if (map->obj->loaded)
                return libbpf_err(-EBUSY);

        map->autocreate = autocreate;
        return 0;
}

int bpf_map__reuse_fd(struct bpf_map *map, int fd)
{
        struct bpf_map_info info;
        __u32 len = sizeof(info), name_len;
        int new_fd, err;
        char *new_name;

        memset(&info, 0, len);
        err = bpf_map_get_info_by_fd(fd, &info, &len);
        if (err && errno == EINVAL)
                err = bpf_get_map_info_from_fdinfo(fd, &info);
        if (err)
                return libbpf_err(err);

        name_len = strlen(info.name);
        if (name_len == BPF_OBJ_NAME_LEN - 1 && strncmp(map->name, info.name, name_len) == 0)
                new_name = strdup(map->name);
        else
                new_name = strdup(info.name);

        if (!new_name)
                return libbpf_err(-errno);

        new_fd = open("/", O_RDONLY | O_CLOEXEC);
        if (new_fd < 0) {
                err = -errno;
                goto err_free_new_name;
        }

        new_fd = dup3(fd, new_fd, O_CLOEXEC);
        if (new_fd < 0) {
                err = -errno;
                goto err_close_new_fd;
        }

        err = zclose(map->fd);
        if (err) {
                err = -errno;
                goto err_close_new_fd;
        }
        free(map->name);

        map->fd = new_fd;
        map->name = new_name;
        map->def.type = info.type;
        map->def.key_size = info.key_size;
        map->def.value_size = info.value_size;
        map->def.max_entries = info.max_entries;
        map->def.map_flags = info.map_flags;
        map->btf_key_type_id = info.btf_key_type_id;
        map->btf_value_type_id = info.btf_value_type_id;
        map->reused = true;
        map->map_extra = info.map_extra;

        return 0;

err_close_new_fd:
        close(new_fd);
err_free_new_name:
        free(new_name);
        return libbpf_err(err);
}

__u32 bpf_map__max_entries(const struct bpf_map *map)
{
        return map->def.max_entries;
}

struct bpf_map *bpf_map__inner_map(struct bpf_map *map)
{
        if (!bpf_map_type__is_map_in_map(map->def.type))
                return errno = EINVAL, NULL;

        return map->inner_map;
}

int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
{
        if (map->obj->loaded)
                return libbpf_err(-EBUSY);

        map->def.max_entries = max_entries;

        /* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
        if (map_is_ringbuf(map))
                map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);

        return 0;
}

static int
bpf_object__probe_loading(struct bpf_object *obj)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        struct bpf_insn insns[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
        int ret, insn_cnt = ARRAY_SIZE(insns);

        if (obj->gen_loader)
                return 0;

        ret = bump_rlimit_memlock();
        if (ret)
                pr_warn("Failed to bump RLIMIT_MEMLOCK (err = %d), you might need to do it explicitly!\n", ret);

        /* make sure basic loading works */
        ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
        if (ret < 0)
                ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
        if (ret < 0) {
                ret = errno;
                cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
                pr_warn("Error in %s():%s(%d). Couldn't load trivial BPF "
                        "program. Make sure your kernel supports BPF "
                        "(CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is "
                        "set to big enough value.\n", __func__, cp, ret);
                return -ret;
        }
        close(ret);

        return 0;
}

static int probe_fd(int fd)
{
        if (fd >= 0)
                close(fd);
        return fd >= 0;
}

static int probe_kern_prog_name(void)
{
        const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
        struct bpf_insn insns[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
        union bpf_attr attr;
        int ret;

        memset(&attr, 0, attr_sz);
        attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
        attr.license = ptr_to_u64("GPL");
        attr.insns = ptr_to_u64(insns);
        attr.insn_cnt = (__u32)ARRAY_SIZE(insns);
        libbpf_strlcpy(attr.prog_name, "libbpf_nametest", sizeof(attr.prog_name));

        /* make sure loading with name works */
        ret = sys_bpf_prog_load(&attr, attr_sz, PROG_LOAD_ATTEMPTS);
        return probe_fd(ret);
}

static int probe_kern_global_data(void)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        struct bpf_insn insns[] = {
                BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
                BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
        int ret, map, insn_cnt = ARRAY_SIZE(insns);

        map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, NULL);
        if (map < 0) {
                ret = -errno;
                cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
                pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
                        __func__, cp, -ret);
                return ret;
        }

        insns[0].imm = map;

        ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
        close(map);
        return probe_fd(ret);
}

static int probe_kern_btf(void)
{
        static const char strs[] = "\0int";
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_btf_func(void)
{
        static const char strs[] = "\0int\0x\0a";
        /* void x(int a) {} */
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
                /* FUNC_PROTO */                                /* [2] */
                BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
                BTF_PARAM_ENC(7, 1),
                /* FUNC x */                                    /* [3] */
                BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0), 2),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_btf_func_global(void)
{
        static const char strs[] = "\0int\0x\0a";
        /* static void x(int a) {} */
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
                /* FUNC_PROTO */                                /* [2] */
                BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
                BTF_PARAM_ENC(7, 1),
                /* FUNC x BTF_FUNC_GLOBAL */                    /* [3] */
                BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 2),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_btf_datasec(void)
{
        static const char strs[] = "\0x\0.data";
        /* static int a; */
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
                /* VAR x */                                     /* [2] */
                BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
                BTF_VAR_STATIC,
                /* DATASEC val */                               /* [3] */
                BTF_TYPE_ENC(3, BTF_INFO_ENC(BTF_KIND_DATASEC, 0, 1), 4),
                BTF_VAR_SECINFO_ENC(2, 0, 4),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_btf_float(void)
{
        static const char strs[] = "\0float";
        __u32 types[] = {
                /* float */
                BTF_TYPE_FLOAT_ENC(1, 4),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_btf_decl_tag(void)
{
        static const char strs[] = "\0tag";
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
                /* VAR x */                                     /* [2] */
                BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
                BTF_VAR_STATIC,
                /* attr */
                BTF_TYPE_DECL_TAG_ENC(1, 2, -1),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_btf_type_tag(void)
{
        static const char strs[] = "\0tag";
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),          /* [1] */
                /* attr */
                BTF_TYPE_TYPE_TAG_ENC(1, 1),                            /* [2] */
                /* ptr */
                BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 2),   /* [3] */
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_array_mmap(void)
{
        LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
        int fd;

        fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_mmap", sizeof(int), sizeof(int), 1, &opts);
        return probe_fd(fd);
}

static int probe_kern_exp_attach_type(void)
{
        LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE);
        struct bpf_insn insns[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
        int fd, insn_cnt = ARRAY_SIZE(insns);

        /* use any valid combination of program type and (optional)
         * non-zero expected attach type (i.e., not a BPF_CGROUP_INET_INGRESS)
         * to see if kernel supports expected_attach_type field for
         * BPF_PROG_LOAD command
         */
        fd = bpf_prog_load(BPF_PROG_TYPE_CGROUP_SOCK, NULL, "GPL", insns, insn_cnt, &opts);
        return probe_fd(fd);
}

static int probe_kern_probe_read_kernel(void)
{
        struct bpf_insn insns[] = {
                BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),   /* r1 = r10 (fp) */
                BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),  /* r1 += -8 */
                BPF_MOV64_IMM(BPF_REG_2, 8),            /* r2 = 8 */
                BPF_MOV64_IMM(BPF_REG_3, 0),            /* r3 = 0 */
                BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_probe_read_kernel),
                BPF_EXIT_INSN(),
        };
        int fd, insn_cnt = ARRAY_SIZE(insns);

        fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
        return probe_fd(fd);
}

static int probe_prog_bind_map(void)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        struct bpf_insn insns[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
        int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);

        map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, NULL);
        if (map < 0) {
                ret = -errno;
                cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
                pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
                        __func__, cp, -ret);
                return ret;
        }

        prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
        if (prog < 0) {
                close(map);
                return 0;
        }

        ret = bpf_prog_bind_map(prog, map, NULL);

        close(map);
        close(prog);

        return ret >= 0;
}

static int probe_module_btf(void)
{
        static const char strs[] = "\0int";
        __u32 types[] = {
                /* int */
                BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
        };
        struct bpf_btf_info info;
        __u32 len = sizeof(info);
        char name[16];
        int fd, err;

        fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs));
        if (fd < 0)
                return 0; /* BTF not supported at all */

        memset(&info, 0, sizeof(info));
        info.name = ptr_to_u64(name);
        info.name_len = sizeof(name);

        /* check that BPF_OBJ_GET_INFO_BY_FD supports specifying name pointer;
         * kernel's module BTF support coincides with support for
         * name/name_len fields in struct bpf_btf_info.
         */
        err = bpf_btf_get_info_by_fd(fd, &info, &len);
        close(fd);
        return !err;
}

static int probe_perf_link(void)
{
        struct bpf_insn insns[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
        int prog_fd, link_fd, err;

        prog_fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL",
                                insns, ARRAY_SIZE(insns), NULL);
        if (prog_fd < 0)
                return -errno;

        /* use invalid perf_event FD to get EBADF, if link is supported;
         * otherwise EINVAL should be returned
         */
        link_fd = bpf_link_create(prog_fd, -1, BPF_PERF_EVENT, NULL);
        err = -errno; /* close() can clobber errno */

        if (link_fd >= 0)
                close(link_fd);
        close(prog_fd);

        return link_fd < 0 && err == -EBADF;
}

static int probe_kern_bpf_cookie(void)
{
        struct bpf_insn insns[] = {
                BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_attach_cookie),
                BPF_EXIT_INSN(),
        };
        int ret, insn_cnt = ARRAY_SIZE(insns);

        ret = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL", insns, insn_cnt, NULL);
        return probe_fd(ret);
}

static int probe_kern_btf_enum64(void)
{
        static const char strs[] = "\0enum64";
        __u32 types[] = {
                BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_ENUM64, 0, 0), 8),
        };

        return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
                                             strs, sizeof(strs)));
}

static int probe_kern_syscall_wrapper(void);

enum kern_feature_result {
        FEAT_UNKNOWN = 0,
        FEAT_SUPPORTED = 1,
        FEAT_MISSING = 2,
};

typedef int (*feature_probe_fn)(void);

static struct kern_feature_desc {
        const char *desc;
        feature_probe_fn probe;
        enum kern_feature_result res;
} feature_probes[__FEAT_CNT] = {
        [FEAT_PROG_NAME] = {
                "BPF program name", probe_kern_prog_name,
        },
        [FEAT_GLOBAL_DATA] = {
                "global variables", probe_kern_global_data,
        },
        [FEAT_BTF] = {
                "minimal BTF", probe_kern_btf,
        },
        [FEAT_BTF_FUNC] = {
                "BTF functions", probe_kern_btf_func,
        },
        [FEAT_BTF_GLOBAL_FUNC] = {
                "BTF global function", probe_kern_btf_func_global,
        },
        [FEAT_BTF_DATASEC] = {
                "BTF data section and variable", probe_kern_btf_datasec,
        },
        [FEAT_ARRAY_MMAP] = {
                "ARRAY map mmap()", probe_kern_array_mmap,
        },
        [FEAT_EXP_ATTACH_TYPE] = {
                "BPF_PROG_LOAD expected_attach_type attribute",
                probe_kern_exp_attach_type,
        },
        [FEAT_PROBE_READ_KERN] = {
                "bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel,
        },
        [FEAT_PROG_BIND_MAP] = {
                "BPF_PROG_BIND_MAP support", probe_prog_bind_map,
        },
        [FEAT_MODULE_BTF] = {
                "module BTF support", probe_module_btf,
        },
        [FEAT_BTF_FLOAT] = {
                "BTF_KIND_FLOAT support", probe_kern_btf_float,
        },
        [FEAT_PERF_LINK] = {
                "BPF perf link support", probe_perf_link,
        },
        [FEAT_BTF_DECL_TAG] = {
                "BTF_KIND_DECL_TAG support", probe_kern_btf_decl_tag,
        },
        [FEAT_BTF_TYPE_TAG] = {
                "BTF_KIND_TYPE_TAG support", probe_kern_btf_type_tag,
        },
        [FEAT_MEMCG_ACCOUNT] = {
                "memcg-based memory accounting", probe_memcg_account,
        },
        [FEAT_BPF_COOKIE] = {
                "BPF cookie support", probe_kern_bpf_cookie,
        },
        [FEAT_BTF_ENUM64] = {
                "BTF_KIND_ENUM64 support", probe_kern_btf_enum64,
        },
        [FEAT_SYSCALL_WRAPPER] = {
                "Kernel using syscall wrapper", probe_kern_syscall_wrapper,
        },
};

bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
{
        struct kern_feature_desc *feat = &feature_probes[feat_id];
        int ret;

        if (obj && obj->gen_loader)
                /* To generate loader program assume the latest kernel
                 * to avoid doing extra prog_load, map_create syscalls.
                 */
                return true;

        if (READ_ONCE(feat->res) == FEAT_UNKNOWN) {
                ret = feat->probe();
                if (ret > 0) {
                        WRITE_ONCE(feat->res, FEAT_SUPPORTED);
                } else if (ret == 0) {
                        WRITE_ONCE(feat->res, FEAT_MISSING);
                } else {
                        pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
                        WRITE_ONCE(feat->res, FEAT_MISSING);
                }
        }

        return READ_ONCE(feat->res) == FEAT_SUPPORTED;
}

static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
{
        struct bpf_map_info map_info;
        char msg[STRERR_BUFSIZE];
        __u32 map_info_len = sizeof(map_info);
        int err;

        memset(&map_info, 0, map_info_len);
        err = bpf_map_get_info_by_fd(map_fd, &map_info, &map_info_len);
        if (err && errno == EINVAL)
                err = bpf_get_map_info_from_fdinfo(map_fd, &map_info);
        if (err) {
                pr_warn("failed to get map info for map FD %d: %s\n", map_fd,
                        libbpf_strerror_r(errno, msg, sizeof(msg)));
                return false;
        }

        return (map_info.type == map->def.type &&
                map_info.key_size == map->def.key_size &&
                map_info.value_size == map->def.value_size &&
                map_info.max_entries == map->def.max_entries &&
                map_info.map_flags == map->def.map_flags &&
                map_info.map_extra == map->map_extra);
}

static int
bpf_object__reuse_map(struct bpf_map *map)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        int err, pin_fd;

        pin_fd = bpf_obj_get(map->pin_path);
        if (pin_fd < 0) {
                err = -errno;
                if (err == -ENOENT) {
                        pr_debug("found no pinned map to reuse at '%s'\n",
                                 map->pin_path);
                        return 0;
                }

                cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
                pr_warn("couldn't retrieve pinned map '%s': %s\n",
                        map->pin_path, cp);
                return err;
        }

        if (!map_is_reuse_compat(map, pin_fd)) {
                pr_warn("couldn't reuse pinned map at '%s': parameter mismatch\n",
                        map->pin_path);
                close(pin_fd);
                return -EINVAL;
        }

        err = bpf_map__reuse_fd(map, pin_fd);
        close(pin_fd);
        if (err)
                return err;

        map->pinned = true;
        pr_debug("reused pinned map at '%s'\n", map->pin_path);

        return 0;
}

static int
bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
{
        enum libbpf_map_type map_type = map->libbpf_type;
        char *cp, errmsg[STRERR_BUFSIZE];
        int err, zero = 0;

        if (obj->gen_loader) {
                bpf_gen__map_update_elem(obj->gen_loader, map - obj->maps,
                                         map->mmaped, map->def.value_size);
                if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG)
                        bpf_gen__map_freeze(obj->gen_loader, map - obj->maps);
                return 0;
        }
        err = bpf_map_update_elem(map->fd, &zero, map->mmaped, 0);
        if (err) {
                err = -errno;
                cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
                pr_warn("Error setting initial map(%s) contents: %s\n",
                        map->name, cp);
                return err;
        }

        /* Freeze .rodata and .kconfig map as read-only from syscall side. */
        if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG) {
                err = bpf_map_freeze(map->fd);
                if (err) {
                        err = -errno;
                        cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
                        pr_warn("Error freezing map(%s) as read-only: %s\n",
                                map->name, cp);
                        return err;
                }
        }
        return 0;
}

static void bpf_map__destroy(struct bpf_map *map);

static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, bool is_inner)
{
        LIBBPF_OPTS(bpf_map_create_opts, create_attr);
        struct bpf_map_def *def = &map->def;
        const char *map_name = NULL;
        int err = 0;

        if (kernel_supports(obj, FEAT_PROG_NAME))
                map_name = map->name;
        create_attr.map_ifindex = map->map_ifindex;
        create_attr.map_flags = def->map_flags;
        create_attr.numa_node = map->numa_node;
        create_attr.map_extra = map->map_extra;

        if (bpf_map__is_struct_ops(map))
                create_attr.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;

        if (obj->btf && btf__fd(obj->btf) >= 0) {
                create_attr.btf_fd = btf__fd(obj->btf);
                create_attr.btf_key_type_id = map->btf_key_type_id;
                create_attr.btf_value_type_id = map->btf_value_type_id;
        }

        if (bpf_map_type__is_map_in_map(def->type)) {
                if (map->inner_map) {
                        err = bpf_object__create_map(obj, map->inner_map, true);
                        if (err) {
                                pr_warn("map '%s': failed to create inner map: %d\n",
                                        map->name, err);
                                return err;
                        }
                        map->inner_map_fd = bpf_map__fd(map->inner_map);
                }
                if (map->inner_map_fd >= 0)
                        create_attr.inner_map_fd = map->inner_map_fd;
        }

        switch (def->type) {
        case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
        case BPF_MAP_TYPE_CGROUP_ARRAY:
        case BPF_MAP_TYPE_STACK_TRACE:
        case BPF_MAP_TYPE_ARRAY_OF_MAPS:
        case BPF_MAP_TYPE_HASH_OF_MAPS:
        case BPF_MAP_TYPE_DEVMAP:
        case BPF_MAP_TYPE_DEVMAP_HASH:
        case BPF_MAP_TYPE_CPUMAP:
        case BPF_MAP_TYPE_XSKMAP:
        case BPF_MAP_TYPE_SOCKMAP:
        case BPF_MAP_TYPE_SOCKHASH:
        case BPF_MAP_TYPE_QUEUE:
        case BPF_MAP_TYPE_STACK:
                create_attr.btf_fd = 0;
                create_attr.btf_key_type_id = 0;
                create_attr.btf_value_type_id = 0;
                map->btf_key_type_id = 0;
                map->btf_value_type_id = 0;
        default:
                break;
        }

        if (obj->gen_loader) {
                bpf_gen__map_create(obj->gen_loader, def->type, map_name,
                                    def->key_size, def->value_size, def->max_entries,
                                    &create_attr, is_inner ? -1 : map - obj->maps);
                /* Pretend to have valid FD to pass various fd >= 0 checks.
                 * This fd == 0 will not be used with any syscall and will be reset to -1 eventually.
                 */
                map->fd = 0;
        } else {
                map->fd = bpf_map_create(def->type, map_name,
                                         def->key_size, def->value_size,
                                         def->max_entries, &create_attr);
        }
        if (map->fd < 0 && (create_attr.btf_key_type_id ||
                            create_attr.btf_value_type_id)) {
                char *cp, errmsg[STRERR_BUFSIZE];

                err = -errno;
                cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
                pr_warn("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
                        map->name, cp, err);
                create_attr.btf_fd = 0;
                create_attr.btf_key_type_id = 0;
                create_attr.btf_value_type_id = 0;
                map->btf_key_type_id = 0;
                map->btf_value_type_id = 0;
                map->fd = bpf_map_create(def->type, map_name,
                                         def->key_size, def->value_size,
                                         def->max_entries, &create_attr);
        }

        err = map->fd < 0 ? -errno : 0;

        if (bpf_map_type__is_map_in_map(def->type) && map->inner_map) {
                if (obj->gen_loader)
                        map->inner_map->fd = -1;
                bpf_map__destroy(map->inner_map);
                zfree(&map->inner_map);
        }

        return err;
}

static int init_map_in_map_slots(struct bpf_object *obj, struct bpf_map *map)
{
        const struct bpf_map *targ_map;
        unsigned int i;
        int fd, err = 0;

        for (i = 0; i < map->init_slots_sz; i++) {
                if (!map->init_slots[i])
                        continue;

                targ_map = map->init_slots[i];
                fd = bpf_map__fd(targ_map);

                if (obj->gen_loader) {
                        bpf_gen__populate_outer_map(obj->gen_loader,
                                                    map - obj->maps, i,
                                                    targ_map - obj->maps);
                } else {
                        err = bpf_map_update_elem(map->fd, &i, &fd, 0);
                }
                if (err) {
                        err = -errno;
                        pr_warn("map '%s': failed to initialize slot [%d] to map '%s' fd=%d: %d\n",
                                map->name, i, targ_map->name, fd, err);
                        return err;
                }
                pr_debug("map '%s': slot [%d] set to map '%s' fd=%d\n",
                         map->name, i, targ_map->name, fd);
        }

        zfree(&map->init_slots);
        map->init_slots_sz = 0;

        return 0;
}

static int init_prog_array_slots(struct bpf_object *obj, struct bpf_map *map)
{
        const struct bpf_program *targ_prog;
        unsigned int i;
        int fd, err;

        if (obj->gen_loader)
                return -ENOTSUP;

        for (i = 0; i < map->init_slots_sz; i++) {
                if (!map->init_slots[i])
                        continue;

                targ_prog = map->init_slots[i];
                fd = bpf_program__fd(targ_prog);

                err = bpf_map_update_elem(map->fd, &i, &fd, 0);
                if (err) {
                        err = -errno;
                        pr_warn("map '%s': failed to initialize slot [%d] to prog '%s' fd=%d: %d\n",
                                map->name, i, targ_prog->name, fd, err);
                        return err;
                }
                pr_debug("map '%s': slot [%d] set to prog '%s' fd=%d\n",
                         map->name, i, targ_prog->name, fd);
        }

        zfree(&map->init_slots);
        map->init_slots_sz = 0;

        return 0;
}

static int bpf_object_init_prog_arrays(struct bpf_object *obj)
{
        struct bpf_map *map;
        int i, err;

        for (i = 0; i < obj->nr_maps; i++) {
                map = &obj->maps[i];

                if (!map->init_slots_sz || map->def.type != BPF_MAP_TYPE_PROG_ARRAY)
                        continue;

                err = init_prog_array_slots(obj, map);
                if (err < 0) {
                        zclose(map->fd);
                        return err;
                }
        }
        return 0;
}

static int map_set_def_max_entries(struct bpf_map *map)
{
        if (map->def.type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && !map->def.max_entries) {
                int nr_cpus;

                nr_cpus = libbpf_num_possible_cpus();
                if (nr_cpus < 0) {
                        pr_warn("map '%s': failed to determine number of system CPUs: %d\n",
                                map->name, nr_cpus);
                        return nr_cpus;
                }
                pr_debug("map '%s': setting size to %d\n", map->name, nr_cpus);
                map->def.max_entries = nr_cpus;
        }

        return 0;
}

static int
bpf_object__create_maps(struct bpf_object *obj)
{
        struct bpf_map *map;
        char *cp, errmsg[STRERR_BUFSIZE];
        unsigned int i, j;
        int err;
        bool retried;

        for (i = 0; i < obj->nr_maps; i++) {
                map = &obj->maps[i];

                /* To support old kernels, we skip creating global data maps
                 * (.rodata, .data, .kconfig, etc); later on, during program
                 * loading, if we detect that at least one of the to-be-loaded
                 * programs is referencing any global data map, we'll error
                 * out with program name and relocation index logged.
                 * This approach allows to accommodate Clang emitting
                 * unnecessary .rodata.str1.1 sections for string literals,
                 * but also it allows to have CO-RE applications that use
                 * global variables in some of BPF programs, but not others.
                 * If those global variable-using programs are not loaded at
                 * runtime due to bpf_program__set_autoload(prog, false),
                 * bpf_object loading will succeed just fine even on old
                 * kernels.
                 */
                if (bpf_map__is_internal(map) && !kernel_supports(obj, FEAT_GLOBAL_DATA))
                        map->autocreate = false;

                if (!map->autocreate) {
                        pr_debug("map '%s': skipped auto-creating...\n", map->name);
                        continue;
                }

                err = map_set_def_max_entries(map);
                if (err)
                        goto err_out;

                retried = false;
retry:
                if (map->pin_path) {
                        err = bpf_object__reuse_map(map);
                        if (err) {
                                pr_warn("map '%s': error reusing pinned map\n",
                                        map->name);
                                goto err_out;
                        }
                        if (retried && map->fd < 0) {
                                pr_warn("map '%s': cannot find pinned map\n",
                                        map->name);
                                err = -ENOENT;
                                goto err_out;
                        }
                }

                if (map->fd >= 0) {
                        pr_debug("map '%s': skipping creation (preset fd=%d)\n",
                                 map->name, map->fd);
                } else {
                        err = bpf_object__create_map(obj, map, false);
                        if (err)
                                goto err_out;

                        pr_debug("map '%s': created successfully, fd=%d\n",
                                 map->name, map->fd);

                        if (bpf_map__is_internal(map)) {
                                err = bpf_object__populate_internal_map(obj, map);
                                if (err < 0) {
                                        zclose(map->fd);
                                        goto err_out;
                                }
                        }

                        if (map->init_slots_sz && map->def.type != BPF_MAP_TYPE_PROG_ARRAY) {
                                err = init_map_in_map_slots(obj, map);
                                if (err < 0) {
                                        zclose(map->fd);
                                        goto err_out;
                                }
                        }
                }

                if (map->pin_path && !map->pinned) {
                        err = bpf_map__pin(map, NULL);
                        if (err) {
                                zclose(map->fd);
                                if (!retried && err == -EEXIST) {
                                        retried = true;
                                        goto retry;
                                }
                                pr_warn("map '%s': failed to auto-pin at '%s': %d\n",
                                        map->name, map->pin_path, err);
                                goto err_out;
                        }
                }
        }

        return 0;

err_out:
        cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
        pr_warn("map '%s': failed to create: %s(%d)\n", map->name, cp, err);
        pr_perm_msg(err);
        for (j = 0; j < i; j++)
                zclose(obj->maps[j].fd);
        return err;
}

static bool bpf_core_is_flavor_sep(const char *s)
{
        /* check X___Y name pattern, where X and Y are not underscores */
        return s[0] != '_' &&                                 /* X */
               s[1] == '_' && s[2] == '_' && s[3] == '_' &&   /* ___ */
               s[4] != '_';                                   /* Y */
}

/* Given 'some_struct_name___with_flavor' return the length of a name prefix
 * before last triple underscore. Struct name part after last triple
 * underscore is ignored by BPF CO-RE relocation during relocation matching.
 */
size_t bpf_core_essential_name_len(const char *name)
{
        size_t n = strlen(name);
        int i;

        for (i = n - 5; i >= 0; i--) {
                if (bpf_core_is_flavor_sep(name + i))
                        return i + 1;
        }
        return n;
}

void bpf_core_free_cands(struct bpf_core_cand_list *cands)
{
        if (!cands)
                return;

        free(cands->cands);
        free(cands);
}

int bpf_core_add_cands(struct bpf_core_cand *local_cand,
                       size_t local_essent_len,
                       const struct btf *targ_btf,
                       const char *targ_btf_name,
                       int targ_start_id,
                       struct bpf_core_cand_list *cands)
{
        struct bpf_core_cand *new_cands, *cand;
        const struct btf_type *t, *local_t;
        const char *targ_name, *local_name;
        size_t targ_essent_len;
        int n, i;

        local_t = btf__type_by_id(local_cand->btf, local_cand->id);
        local_name = btf__str_by_offset(local_cand->btf, local_t->name_off);

        n = btf__type_cnt(targ_btf);
        for (i = targ_start_id; i < n; i++) {
                t = btf__type_by_id(targ_btf, i);
                if (!btf_kind_core_compat(t, local_t))
                        continue;

                targ_name = btf__name_by_offset(targ_btf, t->name_off);
                if (str_is_empty(targ_name))
                        continue;

                targ_essent_len = bpf_core_essential_name_len(targ_name);
                if (targ_essent_len != local_essent_len)
                        continue;

                if (strncmp(local_name, targ_name, local_essent_len) != 0)
                        continue;

                pr_debug("CO-RE relocating [%d] %s %s: found target candidate [%d] %s %s in [%s]\n",
                         local_cand->id, btf_kind_str(local_t),
                         local_name, i, btf_kind_str(t), targ_name,
                         targ_btf_name);
                new_cands = libbpf_reallocarray(cands->cands, cands->len + 1,
                                              sizeof(*cands->cands));
                if (!new_cands)
                        return -ENOMEM;

                cand = &new_cands[cands->len];
                cand->btf = targ_btf;
                cand->id = i;

                cands->cands = new_cands;
                cands->len++;
        }
        return 0;
}

static int load_module_btfs(struct bpf_object *obj)
{
        struct bpf_btf_info info;
        struct module_btf *mod_btf;
        struct btf *btf;
        char name[64];
        __u32 id = 0, len;
        int err, fd;

        if (obj->btf_modules_loaded)
                return 0;

        if (obj->gen_loader)
                return 0;

        /* don't do this again, even if we find no module BTFs */
        obj->btf_modules_loaded = true;

        /* kernel too old to support module BTFs */
        if (!kernel_supports(obj, FEAT_MODULE_BTF))
                return 0;

        while (true) {
                err = bpf_btf_get_next_id(id, &id);
                if (err && errno == ENOENT)
                        return 0;
                if (err) {
                        err = -errno;
                        pr_warn("failed to iterate BTF objects: %d\n", err);
                        return err;
                }

                fd = bpf_btf_get_fd_by_id(id);
                if (fd < 0) {
                        if (errno == ENOENT)
                                continue; /* expected race: BTF was unloaded */
                        err = -errno;
                        pr_warn("failed to get BTF object #%d FD: %d\n", id, err);
                        return err;
                }

                len = sizeof(info);
                memset(&info, 0, sizeof(info));
                info.name = ptr_to_u64(name);
                info.name_len = sizeof(name);

                err = bpf_btf_get_info_by_fd(fd, &info, &len);
                if (err) {
                        err = -errno;
                        pr_warn("failed to get BTF object #%d info: %d\n", id, err);
                        goto err_out;
                }

                /* ignore non-module BTFs */
                if (!info.kernel_btf || strcmp(name, "vmlinux") == 0) {
                        close(fd);
                        continue;
                }

                btf = btf_get_from_fd(fd, obj->btf_vmlinux);
                err = libbpf_get_error(btf);
                if (err) {
                        pr_warn("failed to load module [%s]'s BTF object #%d: %d\n",
                                name, id, err);
                        goto err_out;
                }

                err = libbpf_ensure_mem((void **)&obj->btf_modules, &obj->btf_module_cap,
                                        sizeof(*obj->btf_modules), obj->btf_module_cnt + 1);
                if (err)
                        goto err_out;

                mod_btf = &obj->btf_modules[obj->btf_module_cnt++];

                mod_btf->btf = btf;
                mod_btf->id = id;
                mod_btf->fd = fd;
                mod_btf->name = strdup(name);
                if (!mod_btf->name) {
                        err = -ENOMEM;
                        goto err_out;
                }
                continue;

err_out:
                close(fd);
                return err;
        }

        return 0;
}

static struct bpf_core_cand_list *
bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 local_type_id)
{
        struct bpf_core_cand local_cand = {};
        struct bpf_core_cand_list *cands;
        const struct btf *main_btf;
        const struct btf_type *local_t;
        const char *local_name;
        size_t local_essent_len;
        int err, i;

        local_cand.btf = local_btf;
        local_cand.id = local_type_id;
        local_t = btf__type_by_id(local_btf, local_type_id);
        if (!local_t)
                return ERR_PTR(-EINVAL);

        local_name = btf__name_by_offset(local_btf, local_t->name_off);
        if (str_is_empty(local_name))
                return ERR_PTR(-EINVAL);
        local_essent_len = bpf_core_essential_name_len(local_name);

        cands = calloc(1, sizeof(*cands));
        if (!cands)
                return ERR_PTR(-ENOMEM);

        /* Attempt to find target candidates in vmlinux BTF first */
        main_btf = obj->btf_vmlinux_override ?: obj->btf_vmlinux;
        err = bpf_core_add_cands(&local_cand, local_essent_len, main_btf, "vmlinux", 1, cands);
        if (err)
                goto err_out;

        /* if vmlinux BTF has any candidate, don't got for module BTFs */
        if (cands->len)
                return cands;

        /* if vmlinux BTF was overridden, don't attempt to load module BTFs */
        if (obj->btf_vmlinux_override)
                return cands;

        /* now look through module BTFs, trying to still find candidates */
        err = load_module_btfs(obj);
        if (err)
                goto err_out;

        for (i = 0; i < obj->btf_module_cnt; i++) {
                err = bpf_core_add_cands(&local_cand, local_essent_len,
                                         obj->btf_modules[i].btf,
                                         obj->btf_modules[i].name,
                                         btf__type_cnt(obj->btf_vmlinux),
                                         cands);
                if (err)
                        goto err_out;
        }

        return cands;
err_out:
        bpf_core_free_cands(cands);
        return ERR_PTR(err);
}

/* Check local and target types for compatibility. This check is used for
 * type-based CO-RE relocations and follow slightly different rules than
 * field-based relocations. This function assumes that root types were already
 * checked for name match. Beyond that initial root-level name check, names
 * are completely ignored. Compatibility rules are as follows:
 *   - any two STRUCTs/UNIONs/FWDs/ENUMs/INTs are considered compatible, but
 *     kind should match for local and target types (i.e., STRUCT is not
 *     compatible with UNION);
 *   - for ENUMs, the size is ignored;
 *   - for INT, size and signedness are ignored;
 *   - for ARRAY, dimensionality is ignored, element types are checked for
 *     compatibility recursively;
 *   - CONST/VOLATILE/RESTRICT modifiers are ignored;
 *   - TYPEDEFs/PTRs are compatible if types they pointing to are compatible;
 *   - FUNC_PROTOs are compatible if they have compatible signature: same
 *     number of input args and compatible return and argument types.
 * These rules are not set in stone and probably will be adjusted as we get
 * more experience with using BPF CO-RE relocations.
 */
int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
                              const struct btf *targ_btf, __u32 targ_id)
{
        return __bpf_core_types_are_compat(local_btf, local_id, targ_btf, targ_id, 32);
}

int bpf_core_types_match(const struct btf *local_btf, __u32 local_id,
                         const struct btf *targ_btf, __u32 targ_id)
{
        return __bpf_core_types_match(local_btf, local_id, targ_btf, targ_id, false, 32);
}

static size_t bpf_core_hash_fn(const long key, void *ctx)
{
        return key;
}

static bool bpf_core_equal_fn(const long k1, const long k2, void *ctx)
{
        return k1 == k2;
}

static int record_relo_core(struct bpf_program *prog,
                            const struct bpf_core_relo *core_relo, int insn_idx)
{
        struct reloc_desc *relos, *relo;

        relos = libbpf_reallocarray(prog->reloc_desc,
                                    prog->nr_reloc + 1, sizeof(*relos));
        if (!relos)
                return -ENOMEM;
        relo = &relos[prog->nr_reloc];
        relo->type = RELO_CORE;
        relo->insn_idx = insn_idx;
        relo->core_relo = core_relo;
        prog->reloc_desc = relos;
        prog->nr_reloc++;
        return 0;
}

static const struct bpf_core_relo *find_relo_core(struct bpf_program *prog, int insn_idx)
{
        struct reloc_desc *relo;
        int i;

        for (i = 0; i < prog->nr_reloc; i++) {
                relo = &prog->reloc_desc[i];
                if (relo->type != RELO_CORE || relo->insn_idx != insn_idx)
                        continue;

                return relo->core_relo;
        }

        return NULL;
}

static int bpf_core_resolve_relo(struct bpf_program *prog,
                                 const struct bpf_core_relo *relo,
                                 int relo_idx,
                                 const struct btf *local_btf,
                                 struct hashmap *cand_cache,
                                 struct bpf_core_relo_res *targ_res)
{
        struct bpf_core_spec specs_scratch[3] = {};
        struct bpf_core_cand_list *cands = NULL;
        const char *prog_name = prog->name;
        const struct btf_type *local_type;
        const char *local_name;
        __u32 local_id = relo->type_id;
        int err;

        local_type = btf__type_by_id(local_btf, local_id);
        if (!local_type)
                return -EINVAL;

        local_name = btf__name_by_offset(local_btf, local_type->name_off);
        if (!local_name)
                return -EINVAL;

        if (relo->kind != BPF_CORE_TYPE_ID_LOCAL &&
            !hashmap__find(cand_cache, local_id, &cands)) {
                cands = bpf_core_find_cands(prog->obj, local_btf, local_id);
                if (IS_ERR(cands)) {
                        pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld\n",
                                prog_name, relo_idx, local_id, btf_kind_str(local_type),
                                local_name, PTR_ERR(cands));
                        return PTR_ERR(cands);
                }
                err = hashmap__set(cand_cache, local_id, cands, NULL, NULL);
                if (err) {
                        bpf_core_free_cands(cands);
                        return err;
                }
        }

        return bpf_core_calc_relo_insn(prog_name, relo, relo_idx, local_btf, cands, specs_scratch,
                                       targ_res);
}

static int
bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
{
        const struct btf_ext_info_sec *sec;
        struct bpf_core_relo_res targ_res;
        const struct bpf_core_relo *rec;
        const struct btf_ext_info *seg;
        struct hashmap_entry *entry;
        struct hashmap *cand_cache = NULL;
        struct bpf_program *prog;
        struct bpf_insn *insn;
        const char *sec_name;
        int i, err = 0, insn_idx, sec_idx, sec_num;

        if (obj->btf_ext->core_relo_info.len == 0)
                return 0;

        if (targ_btf_path) {
                obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL);
                err = libbpf_get_error(obj->btf_vmlinux_override);
                if (err) {
                        pr_warn("failed to parse target BTF: %d\n", err);
                        return err;
                }
        }

        cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
        if (IS_ERR(cand_cache)) {
                err = PTR_ERR(cand_cache);
                goto out;
        }

        seg = &obj->btf_ext->core_relo_info;
        sec_num = 0;
        for_each_btf_ext_sec(seg, sec) {
                sec_idx = seg->sec_idxs[sec_num];
                sec_num++;

                sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
                if (str_is_empty(sec_name)) {
                        err = -EINVAL;
                        goto out;
                }

                pr_debug("sec '%s': found %d CO-RE relocations\n", sec_name, sec->num_info);

                for_each_btf_ext_rec(seg, sec, i, rec) {
                        if (rec->insn_off % BPF_INSN_SZ)
                                return -EINVAL;
                        insn_idx = rec->insn_off / BPF_INSN_SZ;
                        prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx);
                        if (!prog) {
                                /* When __weak subprog is "overridden" by another instance
                                 * of the subprog from a different object file, linker still
                                 * appends all the .BTF.ext info that used to belong to that
                                 * eliminated subprogram.
                                 * This is similar to what x86-64 linker does for relocations.
                                 * So just ignore such relocations just like we ignore
                                 * subprog instructions when discovering subprograms.
                                 */
                                pr_debug("sec '%s': skipping CO-RE relocation #%d for insn #%d belonging to eliminated weak subprogram\n",
                                         sec_name, i, insn_idx);
                                continue;
                        }
                        /* no need to apply CO-RE relocation if the program is
                         * not going to be loaded
                         */
                        if (!prog->autoload)
                                continue;

                        /* adjust insn_idx from section frame of reference to the local
                         * program's frame of reference; (sub-)program code is not yet
                         * relocated, so it's enough to just subtract in-section offset
                         */
                        insn_idx = insn_idx - prog->sec_insn_off;
                        if (insn_idx >= prog->insns_cnt)
                                return -EINVAL;
                        insn = &prog->insns[insn_idx];

                        err = record_relo_core(prog, rec, insn_idx);
                        if (err) {
                                pr_warn("prog '%s': relo #%d: failed to record relocation: %d\n",
                                        prog->name, i, err);
                                goto out;
                        }

                        if (prog->obj->gen_loader)
                                continue;

                        err = bpf_core_resolve_relo(prog, rec, i, obj->btf, cand_cache, &targ_res);
                        if (err) {
                                pr_warn("prog '%s': relo #%d: failed to relocate: %d\n",
                                        prog->name, i, err);
                                goto out;
                        }

                        err = bpf_core_patch_insn(prog->name, insn, insn_idx, rec, i, &targ_res);
                        if (err) {
                                pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n",
                                        prog->name, i, insn_idx, err);
                                goto out;
                        }
                }
        }

out:
        /* obj->btf_vmlinux and module BTFs are freed after object load */
        btf__free(obj->btf_vmlinux_override);
        obj->btf_vmlinux_override = NULL;

        if (!IS_ERR_OR_NULL(cand_cache)) {
                hashmap__for_each_entry(cand_cache, entry, i) {
                        bpf_core_free_cands(entry->pvalue);
                }
                hashmap__free(cand_cache);
        }
        return err;
}

/* base map load ldimm64 special constant, used also for log fixup logic */
#define POISON_LDIMM64_MAP_BASE 2001000000
#define POISON_LDIMM64_MAP_PFX "200100"

static void poison_map_ldimm64(struct bpf_program *prog, int relo_idx,
                               int insn_idx, struct bpf_insn *insn,
                               int map_idx, const struct bpf_map *map)
{
        int i;

        pr_debug("prog '%s': relo #%d: poisoning insn #%d that loads map #%d '%s'\n",
                 prog->name, relo_idx, insn_idx, map_idx, map->name);

        /* we turn single ldimm64 into two identical invalid calls */
        for (i = 0; i < 2; i++) {
                insn->code = BPF_JMP | BPF_CALL;
                insn->dst_reg = 0;
                insn->src_reg = 0;
                insn->off = 0;
                /* if this instruction is reachable (not a dead code),
                 * verifier will complain with something like:
                 * invalid func unknown#2001000123
                 * where lower 123 is map index into obj->maps[] array
                 */
                insn->imm = POISON_LDIMM64_MAP_BASE + map_idx;

                insn++;
        }
}

/* unresolved kfunc call special constant, used also for log fixup logic */
#define POISON_CALL_KFUNC_BASE 2002000000
#define POISON_CALL_KFUNC_PFX "2002"

static void poison_kfunc_call(struct bpf_program *prog, int relo_idx,
                              int insn_idx, struct bpf_insn *insn,
                              int ext_idx, const struct extern_desc *ext)
{
        pr_debug("prog '%s': relo #%d: poisoning insn #%d that calls kfunc '%s'\n",
                 prog->name, relo_idx, insn_idx, ext->name);

        /* we turn kfunc call into invalid helper call with identifiable constant */
        insn->code = BPF_JMP | BPF_CALL;
        insn->dst_reg = 0;
        insn->src_reg = 0;
        insn->off = 0;
        /* if this instruction is reachable (not a dead code),
         * verifier will complain with something like:
         * invalid func unknown#2001000123
         * where lower 123 is extern index into obj->externs[] array
         */
        insn->imm = POISON_CALL_KFUNC_BASE + ext_idx;
}

/* Relocate data references within program code:
 *  - map references;
 *  - global variable references;
 *  - extern references.
 */
static int
bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
{
        int i;

        for (i = 0; i < prog->nr_reloc; i++) {
                struct reloc_desc *relo = &prog->reloc_desc[i];
                struct bpf_insn *insn = &prog->insns[relo->insn_idx];
                const struct bpf_map *map;
                struct extern_desc *ext;

                switch (relo->type) {
                case RELO_LD64:
                        map = &obj->maps[relo->map_idx];
                        if (obj->gen_loader) {
                                insn[0].src_reg = BPF_PSEUDO_MAP_IDX;
                                insn[0].imm = relo->map_idx;
                        } else if (map->autocreate) {
                                insn[0].src_reg = BPF_PSEUDO_MAP_FD;
                                insn[0].imm = map->fd;
                        } else {
                                poison_map_ldimm64(prog, i, relo->insn_idx, insn,
                                                   relo->map_idx, map);
                        }
                        break;
                case RELO_DATA:
                        map = &obj->maps[relo->map_idx];
                        insn[1].imm = insn[0].imm + relo->sym_off;
                        if (obj->gen_loader) {
                                insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
                                insn[0].imm = relo->map_idx;
                        } else if (map->autocreate) {
                                insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
                                insn[0].imm = map->fd;
                        } else {
                                poison_map_ldimm64(prog, i, relo->insn_idx, insn,
                                                   relo->map_idx, map);
                        }
                        break;
                case RELO_EXTERN_LD64:
                        ext = &obj->externs[relo->ext_idx];
                        if (ext->type == EXT_KCFG) {
                                if (obj->gen_loader) {
                                        insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
                                        insn[0].imm = obj->kconfig_map_idx;
                                } else {
                                        insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
                                        insn[0].imm = obj->maps[obj->kconfig_map_idx].fd;
                                }
                                insn[1].imm = ext->kcfg.data_off;
                        } else /* EXT_KSYM */ {
                                if (ext->ksym.type_id && ext->is_set) { /* typed ksyms */
                                        insn[0].src_reg = BPF_PSEUDO_BTF_ID;
                                        insn[0].imm = ext->ksym.kernel_btf_id;
                                        insn[1].imm = ext->ksym.kernel_btf_obj_fd;
                                } else { /* typeless ksyms or unresolved typed ksyms */
                                        insn[0].imm = (__u32)ext->ksym.addr;
                                        insn[1].imm = ext->ksym.addr >> 32;
                                }
                        }
                        break;
                case RELO_EXTERN_CALL:
                        ext = &obj->externs[relo->ext_idx];
                        insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
                        if (ext->is_set) {
                                insn[0].imm = ext->ksym.kernel_btf_id;
                                insn[0].off = ext->ksym.btf_fd_idx;
                        } else { /* unresolved weak kfunc call */
                                poison_kfunc_call(prog, i, relo->insn_idx, insn,
                                                  relo->ext_idx, ext);
                        }
                        break;
                case RELO_SUBPROG_ADDR:
                        if (insn[0].src_reg != BPF_PSEUDO_FUNC) {
                                pr_warn("prog '%s': relo #%d: bad insn\n",
                                        prog->name, i);
                                return -EINVAL;
                        }
                        /* handled already */
                        break;
                case RELO_CALL:
                        /* handled already */
                        break;
                case RELO_CORE:
                        /* will be handled by bpf_program_record_relos() */
                        break;
                default:
                        pr_warn("prog '%s': relo #%d: bad relo type %d\n",
                                prog->name, i, relo->type);
                        return -EINVAL;
                }
        }

        return 0;
}

static int adjust_prog_btf_ext_info(const struct bpf_object *obj,
                                    const struct bpf_program *prog,
                                    const struct btf_ext_info *ext_info,
                                    void **prog_info, __u32 *prog_rec_cnt,
                                    __u32 *prog_rec_sz)
{
        void *copy_start = NULL, *copy_end = NULL;
        void *rec, *rec_end, *new_prog_info;
        const struct btf_ext_info_sec *sec;
        size_t old_sz, new_sz;
        int i, sec_num, sec_idx, off_adj;

        sec_num = 0;
        for_each_btf_ext_sec(ext_info, sec) {
                sec_idx = ext_info->sec_idxs[sec_num];
                sec_num++;
                if (prog->sec_idx != sec_idx)
                        continue;

                for_each_btf_ext_rec(ext_info, sec, i, rec) {
                        __u32 insn_off = *(__u32 *)rec / BPF_INSN_SZ;

                        if (insn_off < prog->sec_insn_off)
                                continue;
                        if (insn_off >= prog->sec_insn_off + prog->sec_insn_cnt)
                                break;

                        if (!copy_start)
                                copy_start = rec;
                        copy_end = rec + ext_info->rec_size;
                }

                if (!copy_start)
                        return -ENOENT;

                /* append func/line info of a given (sub-)program to the main
                 * program func/line info
                 */
                old_sz = (size_t)(*prog_rec_cnt) * ext_info->rec_size;
                new_sz = old_sz + (copy_end - copy_start);
                new_prog_info = realloc(*prog_info, new_sz);
                if (!new_prog_info)
                        return -ENOMEM;
                *prog_info = new_prog_info;
                *prog_rec_cnt = new_sz / ext_info->rec_size;
                memcpy(new_prog_info + old_sz, copy_start, copy_end - copy_start);

                /* Kernel instruction offsets are in units of 8-byte
                 * instructions, while .BTF.ext instruction offsets generated
                 * by Clang are in units of bytes. So convert Clang offsets
                 * into kernel offsets and adjust offset according to program
                 * relocated position.
                 */
                off_adj = prog->sub_insn_off - prog->sec_insn_off;
                rec = new_prog_info + old_sz;
                rec_end = new_prog_info + new_sz;
                for (; rec < rec_end; rec += ext_info->rec_size) {
                        __u32 *insn_off = rec;

                        *insn_off = *insn_off / BPF_INSN_SZ + off_adj;
                }
                *prog_rec_sz = ext_info->rec_size;
                return 0;
        }

        return -ENOENT;
}

static int
reloc_prog_func_and_line_info(const struct bpf_object *obj,
                              struct bpf_program *main_prog,
                              const struct bpf_program *prog)
{
        int err;

        /* no .BTF.ext relocation if .BTF.ext is missing or kernel doesn't
         * supprot func/line info
         */
        if (!obj->btf_ext || !kernel_supports(obj, FEAT_BTF_FUNC))
                return 0;

        /* only attempt func info relocation if main program's func_info
         * relocation was successful
         */
        if (main_prog != prog && !main_prog->func_info)
                goto line_info;

        err = adjust_prog_btf_ext_info(obj, prog, &obj->btf_ext->func_info,
                                       &main_prog->func_info,
                                       &main_prog->func_info_cnt,
                                       &main_prog->func_info_rec_size);
        if (err) {
                if (err != -ENOENT) {
                        pr_warn("prog '%s': error relocating .BTF.ext function info: %d\n",
                                prog->name, err);
                        return err;
                }
                if (main_prog->func_info) {
                        /*
                         * Some info has already been found but has problem
                         * in the last btf_ext reloc. Must have to error out.
                         */
                        pr_warn("prog '%s': missing .BTF.ext function info.\n", prog->name);
                        return err;
                }
                /* Have problem loading the very first info. Ignore the rest. */
                pr_warn("prog '%s': missing .BTF.ext function info for the main program, skipping all of .BTF.ext func info.\n",
                        prog->name);
        }

line_info:
        /* don't relocate line info if main program's relocation failed */
        if (main_prog != prog && !main_prog->line_info)
                return 0;

        err = adjust_prog_btf_ext_info(obj, prog, &obj->btf_ext->line_info,
                                       &main_prog->line_info,
                                       &main_prog->line_info_cnt,
                                       &main_prog->line_info_rec_size);
        if (err) {
                if (err != -ENOENT) {
                        pr_warn("prog '%s': error relocating .BTF.ext line info: %d\n",
                                prog->name, err);
                        return err;
                }
                if (main_prog->line_info) {
                        /*
                         * Some info has already been found but has problem
                         * in the last btf_ext reloc. Must have to error out.
                         */
                        pr_warn("prog '%s': missing .BTF.ext line info.\n", prog->name);
                        return err;
                }
                /* Have problem loading the very first info. Ignore the rest. */
                pr_warn("prog '%s': missing .BTF.ext line info for the main program, skipping all of .BTF.ext line info.\n",
                        prog->name);
        }
        return 0;
}

static int cmp_relo_by_insn_idx(const void *key, const void *elem)
{
        size_t insn_idx = *(const size_t *)key;
        const struct reloc_desc *relo = elem;

        if (insn_idx == relo->insn_idx)
                return 0;
        return insn_idx < relo->insn_idx ? -1 : 1;
}

static struct reloc_desc *find_prog_insn_relo(const struct bpf_program *prog, size_t insn_idx)
{
        if (!prog->nr_reloc)
                return NULL;
        return bsearch(&insn_idx, prog->reloc_desc, prog->nr_reloc,
                       sizeof(*prog->reloc_desc), cmp_relo_by_insn_idx);
}

static int append_subprog_relos(struct bpf_program *main_prog, struct bpf_program *subprog)
{
        int new_cnt = main_prog->nr_reloc + subprog->nr_reloc;
        struct reloc_desc *relos;
        int i;

        if (main_prog == subprog)
                return 0;
        relos = libbpf_reallocarray(main_prog->reloc_desc, new_cnt, sizeof(*relos));
        if (!relos)
                return -ENOMEM;
        if (subprog->nr_reloc)
                memcpy(relos + main_prog->nr_reloc, subprog->reloc_desc,
                       sizeof(*relos) * subprog->nr_reloc);

        for (i = main_prog->nr_reloc; i < new_cnt; i++)
                relos[i].insn_idx += subprog->sub_insn_off;
        /* After insn_idx adjustment the 'relos' array is still sorted
         * by insn_idx and doesn't break bsearch.
         */
        main_prog->reloc_desc = relos;
        main_prog->nr_reloc = new_cnt;
        return 0;
}

static int
bpf_object__reloc_code(struct bpf_object *obj, struct bpf_program *main_prog,
                       struct bpf_program *prog)
{
        size_t sub_insn_idx, insn_idx, new_cnt;
        struct bpf_program *subprog;
        struct bpf_insn *insns, *insn;
        struct reloc_desc *relo;
        int err;

        err = reloc_prog_func_and_line_info(obj, main_prog, prog);
        if (err)
                return err;

        for (insn_idx = 0; insn_idx < prog->sec_insn_cnt; insn_idx++) {
                insn = &main_prog->insns[prog->sub_insn_off + insn_idx];
                if (!insn_is_subprog_call(insn) && !insn_is_pseudo_func(insn))
                        continue;

                relo = find_prog_insn_relo(prog, insn_idx);
                if (relo && relo->type == RELO_EXTERN_CALL)
                        /* kfunc relocations will be handled later
                         * in bpf_object__relocate_data()
                         */
                        continue;
                if (relo && relo->type != RELO_CALL && relo->type != RELO_SUBPROG_ADDR) {
                        pr_warn("prog '%s': unexpected relo for insn #%zu, type %d\n",
                                prog->name, insn_idx, relo->type);
                        return -LIBBPF_ERRNO__RELOC;
                }
                if (relo) {
                        /* sub-program instruction index is a combination of
                         * an offset of a symbol pointed to by relocation and
                         * call instruction's imm field; for global functions,
                         * call always has imm = -1, but for static functions
                         * relocation is against STT_SECTION and insn->imm
                         * points to a start of a static function
                         *
                         * for subprog addr relocation, the relo->sym_off + insn->imm is
                         * the byte offset in the corresponding section.
                         */
                        if (relo->type == RELO_CALL)
                                sub_insn_idx = relo->sym_off / BPF_INSN_SZ + insn->imm + 1;
                        else
                                sub_insn_idx = (relo->sym_off + insn->imm) / BPF_INSN_SZ;
                } else if (insn_is_pseudo_func(insn)) {
                        /*
                         * RELO_SUBPROG_ADDR relo is always emitted even if both
                         * functions are in the same section, so it shouldn't reach here.
                         */
                        pr_warn("prog '%s': missing subprog addr relo for insn #%zu\n",
                                prog->name, insn_idx);
                        return -LIBBPF_ERRNO__RELOC;
                } else {
                        /* if subprogram call is to a static function within
                         * the same ELF section, there won't be any relocation
                         * emitted, but it also means there is no additional
                         * offset necessary, insns->imm is relative to
                         * instruction's original position within the section
                         */
                        sub_insn_idx = prog->sec_insn_off + insn_idx + insn->imm + 1;
                }

                /* we enforce that sub-programs should be in .text section */
                subprog = find_prog_by_sec_insn(obj, obj->efile.text_shndx, sub_insn_idx);
                if (!subprog) {
                        pr_warn("prog '%s': no .text section found yet sub-program call exists\n",
                                prog->name);
                        return -LIBBPF_ERRNO__RELOC;
                }

                /* if it's the first call instruction calling into this
                 * subprogram (meaning this subprog hasn't been processed
                 * yet) within the context of current main program:
                 *   - append it at the end of main program's instructions blog;
                 *   - process is recursively, while current program is put on hold;
                 *   - if that subprogram calls some other not yet processes
                 *   subprogram, same thing will happen recursively until
                 *   there are no more unprocesses subprograms left to append
                 *   and relocate.
                 */
                if (subprog->sub_insn_off == 0) {
                        subprog->sub_insn_off = main_prog->insns_cnt;

                        new_cnt = main_prog->insns_cnt + subprog->insns_cnt;
                        insns = libbpf_reallocarray(main_prog->insns, new_cnt, sizeof(*insns));
                        if (!insns) {
                                pr_warn("prog '%s': failed to realloc prog code\n", main_prog->name);
                                return -ENOMEM;
                        }
                        main_prog->insns = insns;
                        main_prog->insns_cnt = new_cnt;

                        memcpy(main_prog->insns + subprog->sub_insn_off, subprog->insns,
                               subprog->insns_cnt * sizeof(*insns));

                        pr_debug("prog '%s': added %zu insns from sub-prog '%s'\n",
                                 main_prog->name, subprog->insns_cnt, subprog->name);

                        /* The subprog insns are now appended. Append its relos too. */
                        err = append_subprog_relos(main_prog, subprog);
                        if (err)
                                return err;
                        err = bpf_object__reloc_code(obj, main_prog, subprog);
                        if (err)
                                return err;
                }

                /* main_prog->insns memory could have been re-allocated, so
                 * calculate pointer again
                 */
                insn = &main_prog->insns[prog->sub_insn_off + insn_idx];
                /* calculate correct instruction position within current main
                 * prog; each main prog can have a different set of
                 * subprograms appended (potentially in different order as
                 * well), so position of any subprog can be different for
                 * different main programs
                 */
                insn->imm = subprog->sub_insn_off - (prog->sub_insn_off + insn_idx) - 1;

                pr_debug("prog '%s': insn #%zu relocated, imm %d points to subprog '%s' (now at %zu offset)\n",
                         prog->name, insn_idx, insn->imm, subprog->name, subprog->sub_insn_off);
        }

        return 0;
}

/*
 * Relocate sub-program calls.
 *
 * Algorithm operates as follows. Each entry-point BPF program (referred to as
 * main prog) is processed separately. For each subprog (non-entry functions,
 * that can be called from either entry progs or other subprogs) gets their
 * sub_insn_off reset to zero. This serves as indicator that this subprogram
 * hasn't been yet appended and relocated within current main prog. Once its
 * relocated, sub_insn_off will point at the position within current main prog
 * where given subprog was appended. This will further be used to relocate all
 * the call instructions jumping into this subprog.
 *
 * We start with main program and process all call instructions. If the call
 * is into a subprog that hasn't been processed (i.e., subprog->sub_insn_off
 * is zero), subprog instructions are appended at the end of main program's
 * instruction array. Then main program is "put on hold" while we recursively
 * process newly appended subprogram. If that subprogram calls into another
 * subprogram that hasn't been appended, new subprogram is appended again to
 * the *main* prog's instructions (subprog's instructions are always left
 * untouched, as they need to be in unmodified state for subsequent main progs
 * and subprog instructions are always sent only as part of a main prog) and
 * the process continues recursively. Once all the subprogs called from a main
 * prog or any of its subprogs are appended (and relocated), all their
 * positions within finalized instructions array are known, so it's easy to
 * rewrite call instructions with correct relative offsets, corresponding to
 * desired target subprog.
 *
 * Its important to realize that some subprogs might not be called from some
 * main prog and any of its called/used subprogs. Those will keep their
 * subprog->sub_insn_off as zero at all times and won't be appended to current
 * main prog and won't be relocated within the context of current main prog.
 * They might still be used from other main progs later.
 *
 * Visually this process can be shown as below. Suppose we have two main
 * programs mainA and mainB and BPF object contains three subprogs: subA,
 * subB, and subC. mainA calls only subA, mainB calls only subC, but subA and
 * subC both call subB:
 *
 *        +--------+ +-------+
 *        |        v v       |
 *     +--+---+ +--+-+-+ +---+--+
 *     | subA | | subB | | subC |
 *     +--+---+ +------+ +---+--+
 *        ^                  ^
 *        |                  |
 *    +---+-------+   +------+----+
 *    |   mainA   |   |   mainB   |
 *    +-----------+   +-----------+
 *
 * We'll start relocating mainA, will find subA, append it and start
 * processing sub A recursively:
 *
 *    +-----------+------+
 *    |   mainA   | subA |
 *    +-----------+------+
 *
 * At this point we notice that subB is used from subA, so we append it and
 * relocate (there are no further subcalls from subB):
 *
 *    +-----------+------+------+
 *    |   mainA   | subA | subB |
 *    +-----------+------+------+
 *
 * At this point, we relocate subA calls, then go one level up and finish with
 * relocatin mainA calls. mainA is done.
 *
 * For mainB process is similar but results in different order. We start with
 * mainB and skip subA and subB, as mainB never calls them (at least
 * directly), but we see subC is needed, so we append and start processing it:
 *
 *    +-----------+------+
 *    |   mainB   | subC |
 *    +-----------+------+
 * Now we see subC needs subB, so we go back to it, append and relocate it:
 *
 *    +-----------+------+------+
 *    |   mainB   | subC | subB |
 *    +-----------+------+------+
 *
 * At this point we unwind recursion, relocate calls in subC, then in mainB.
 */
static int
bpf_object__relocate_calls(struct bpf_object *obj, struct bpf_program *prog)
{
        struct bpf_program *subprog;
        int i, err;

        /* mark all subprogs as not relocated (yet) within the context of
         * current main program
         */
        for (i = 0; i < obj->nr_programs; i++) {
                subprog = &obj->programs[i];
                if (!prog_is_subprog(obj, subprog))
                        continue;

                subprog->sub_insn_off = 0;
        }

        err = bpf_object__reloc_code(obj, prog, prog);
        if (err)
                return err;

        return 0;
}

static void
bpf_object__free_relocs(struct bpf_object *obj)
{
        struct bpf_program *prog;
        int i;

        /* free up relocation descriptors */
        for (i = 0; i < obj->nr_programs; i++) {
                prog = &obj->programs[i];
                zfree(&prog->reloc_desc);
                prog->nr_reloc = 0;
        }
}

static int cmp_relocs(const void *_a, const void *_b)
{
        const struct reloc_desc *a = _a;
        const struct reloc_desc *b = _b;

        if (a->insn_idx != b->insn_idx)
                return a->insn_idx < b->insn_idx ? -1 : 1;

        /* no two relocations should have the same insn_idx, but ... */
        if (a->type != b->type)
                return a->type < b->type ? -1 : 1;

        return 0;
}

static void bpf_object__sort_relos(struct bpf_object *obj)
{
        int i;

        for (i = 0; i < obj->nr_programs; i++) {
                struct bpf_program *p = &obj->programs[i];

                if (!p->nr_reloc)
                        continue;

                qsort(p->reloc_desc, p->nr_reloc, sizeof(*p->reloc_desc), cmp_relocs);
        }
}

static int
bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
{
        struct bpf_program *prog;
        size_t i, j;
        int err;

        if (obj->btf_ext) {
                err = bpf_object__relocate_core(obj, targ_btf_path);
                if (err) {
                        pr_warn("failed to perform CO-RE relocations: %d\n",
                                err);
                        return err;
                }
                bpf_object__sort_relos(obj);
        }

        /* Before relocating calls pre-process relocations and mark
         * few ld_imm64 instructions that points to subprogs.
         * Otherwise bpf_object__reloc_code() later would have to consider
         * all ld_imm64 insns as relocation candidates. That would
         * reduce relocation speed, since amount of find_prog_insn_relo()
         * would increase and most of them will fail to find a relo.
         */
        for (i = 0; i < obj->nr_programs; i++) {
                prog = &obj->programs[i];
                for (j = 0; j < prog->nr_reloc; j++) {
                        struct reloc_desc *relo = &prog->reloc_desc[j];
                        struct bpf_insn *insn = &prog->insns[relo->insn_idx];

                        /* mark the insn, so it's recognized by insn_is_pseudo_func() */
                        if (relo->type == RELO_SUBPROG_ADDR)
                                insn[0].src_reg = BPF_PSEUDO_FUNC;
                }
        }

        /* relocate subprogram calls and append used subprograms to main
         * programs; each copy of subprogram code needs to be relocated
         * differently for each main program, because its code location might
         * have changed.
         * Append subprog relos to main programs to allow data relos to be
         * processed after text is completely relocated.
         */
        for (i = 0; i < obj->nr_programs; i++) {
                prog = &obj->programs[i];
                /* sub-program's sub-calls are relocated within the context of
                 * its main program only
                 */
                if (prog_is_subprog(obj, prog))
                        continue;
                if (!prog->autoload)
                        continue;

                err = bpf_object__relocate_calls(obj, prog);
                if (err) {
                        pr_warn("prog '%s': failed to relocate calls: %d\n",
                                prog->name, err);
                        return err;
                }
        }
        /* Process data relos for main programs */
        for (i = 0; i < obj->nr_programs; i++) {
                prog = &obj->programs[i];
                if (prog_is_subprog(obj, prog))
                        continue;
                if (!prog->autoload)
                        continue;
                err = bpf_object__relocate_data(obj, prog);
                if (err) {
                        pr_warn("prog '%s': failed to relocate data references: %d\n",
                                prog->name, err);
                        return err;
                }
        }

        return 0;
}

static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
                                            Elf64_Shdr *shdr, Elf_Data *data);

static int bpf_object__collect_map_relos(struct bpf_object *obj,
                                         Elf64_Shdr *shdr, Elf_Data *data)
{
        const int bpf_ptr_sz = 8, host_ptr_sz = sizeof(void *);
        int i, j, nrels, new_sz;
        const struct btf_var_secinfo *vi = NULL;
        const struct btf_type *sec, *var, *def;
        struct bpf_map *map = NULL, *targ_map = NULL;
        struct bpf_program *targ_prog = NULL;
        bool is_prog_array, is_map_in_map;
        const struct btf_member *member;
        const char *name, *mname, *type;
        unsigned int moff;
        Elf64_Sym *sym;
        Elf64_Rel *rel;
        void *tmp;

        if (!obj->efile.btf_maps_sec_btf_id || !obj->btf)
                return -EINVAL;
        sec = btf__type_by_id(obj->btf, obj->efile.btf_maps_sec_btf_id);
        if (!sec)
                return -EINVAL;

        nrels = shdr->sh_size / shdr->sh_entsize;
        for (i = 0; i < nrels; i++) {
                rel = elf_rel_by_idx(data, i);
                if (!rel) {
                        pr_warn(".maps relo #%d: failed to get ELF relo\n", i);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                sym = elf_sym_by_idx(obj, ELF64_R_SYM(rel->r_info));
                if (!sym) {
                        pr_warn(".maps relo #%d: symbol %zx not found\n",
                                i, (size_t)ELF64_R_SYM(rel->r_info));
                        return -LIBBPF_ERRNO__FORMAT;
                }
                name = elf_sym_str(obj, sym->st_name) ?: "<?>";

                pr_debug(".maps relo #%d: for %zd value %zd rel->r_offset %zu name %d ('%s')\n",
                         i, (ssize_t)(rel->r_info >> 32), (size_t)sym->st_value,
                         (size_t)rel->r_offset, sym->st_name, name);

                for (j = 0; j < obj->nr_maps; j++) {
                        map = &obj->maps[j];
                        if (map->sec_idx != obj->efile.btf_maps_shndx)
                                continue;

                        vi = btf_var_secinfos(sec) + map->btf_var_idx;
                        if (vi->offset <= rel->r_offset &&
                            rel->r_offset + bpf_ptr_sz <= vi->offset + vi->size)
                                break;
                }
                if (j == obj->nr_maps) {
                        pr_warn(".maps relo #%d: cannot find map '%s' at rel->r_offset %zu\n",
                                i, name, (size_t)rel->r_offset);
                        return -EINVAL;
                }

                is_map_in_map = bpf_map_type__is_map_in_map(map->def.type);
                is_prog_array = map->def.type == BPF_MAP_TYPE_PROG_ARRAY;
                type = is_map_in_map ? "map" : "prog";
                if (is_map_in_map) {
                        if (sym->st_shndx != obj->efile.btf_maps_shndx) {
                                pr_warn(".maps relo #%d: '%s' isn't a BTF-defined map\n",
                                        i, name);
                                return -LIBBPF_ERRNO__RELOC;
                        }
                        if (map->def.type == BPF_MAP_TYPE_HASH_OF_MAPS &&
                            map->def.key_size != sizeof(int)) {
                                pr_warn(".maps relo #%d: hash-of-maps '%s' should have key size %zu.\n",
                                        i, map->name, sizeof(int));
                                return -EINVAL;
                        }
                        targ_map = bpf_object__find_map_by_name(obj, name);
                        if (!targ_map) {
                                pr_warn(".maps relo #%d: '%s' isn't a valid map reference\n",
                                        i, name);
                                return -ESRCH;
                        }
                } else if (is_prog_array) {
                        targ_prog = bpf_object__find_program_by_name(obj, name);
                        if (!targ_prog) {
                                pr_warn(".maps relo #%d: '%s' isn't a valid program reference\n",
                                        i, name);
                                return -ESRCH;
                        }
                        if (targ_prog->sec_idx != sym->st_shndx ||
                            targ_prog->sec_insn_off * 8 != sym->st_value ||
                            prog_is_subprog(obj, targ_prog)) {
                                pr_warn(".maps relo #%d: '%s' isn't an entry-point program\n",
                                        i, name);
                                return -LIBBPF_ERRNO__RELOC;
                        }
                } else {
                        return -EINVAL;
                }

                var = btf__type_by_id(obj->btf, vi->type);
                def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
                if (btf_vlen(def) == 0)
                        return -EINVAL;
                member = btf_members(def) + btf_vlen(def) - 1;
                mname = btf__name_by_offset(obj->btf, member->name_off);
                if (strcmp(mname, "values"))
                        return -EINVAL;

                moff = btf_member_bit_offset(def, btf_vlen(def) - 1) / 8;
                if (rel->r_offset - vi->offset < moff)
                        return -EINVAL;

                moff = rel->r_offset - vi->offset - moff;
                /* here we use BPF pointer size, which is always 64 bit, as we
                 * are parsing ELF that was built for BPF target
                 */
                if (moff % bpf_ptr_sz)
                        return -EINVAL;
                moff /= bpf_ptr_sz;
                if (moff >= map->init_slots_sz) {
                        new_sz = moff + 1;
                        tmp = libbpf_reallocarray(map->init_slots, new_sz, host_ptr_sz);
                        if (!tmp)
                                return -ENOMEM;
                        map->init_slots = tmp;
                        memset(map->init_slots + map->init_slots_sz, 0,
                               (new_sz - map->init_slots_sz) * host_ptr_sz);
                        map->init_slots_sz = new_sz;
                }
                map->init_slots[moff] = is_map_in_map ? (void *)targ_map : (void *)targ_prog;

                pr_debug(".maps relo #%d: map '%s' slot [%d] points to %s '%s'\n",
                         i, map->name, moff, type, name);
        }

        return 0;
}

static int bpf_object__collect_relos(struct bpf_object *obj)
{
        int i, err;

        for (i = 0; i < obj->efile.sec_cnt; i++) {
                struct elf_sec_desc *sec_desc = &obj->efile.secs[i];
                Elf64_Shdr *shdr;
                Elf_Data *data;
                int idx;

                if (sec_desc->sec_type != SEC_RELO)
                        continue;

                shdr = sec_desc->shdr;
                data = sec_desc->data;
                idx = shdr->sh_info;

                if (shdr->sh_type != SHT_REL) {
                        pr_warn("internal error at %d\n", __LINE__);
                        return -LIBBPF_ERRNO__INTERNAL;
                }

                if (idx == obj->efile.st_ops_shndx || idx == obj->efile.st_ops_link_shndx)
                        err = bpf_object__collect_st_ops_relos(obj, shdr, data);
                else if (idx == obj->efile.btf_maps_shndx)
                        err = bpf_object__collect_map_relos(obj, shdr, data);
                else
                        err = bpf_object__collect_prog_relos(obj, shdr, data);
                if (err)
                        return err;
        }

        bpf_object__sort_relos(obj);
        return 0;
}

static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id)
{
        if (BPF_CLASS(insn->code) == BPF_JMP &&
            BPF_OP(insn->code) == BPF_CALL &&
            BPF_SRC(insn->code) == BPF_K &&
            insn->src_reg == 0 &&
            insn->dst_reg == 0) {
                    *func_id = insn->imm;
                    return true;
        }
        return false;
}

static int bpf_object__sanitize_prog(struct bpf_object *obj, struct bpf_program *prog)
{
        struct bpf_insn *insn = prog->insns;
        enum bpf_func_id func_id;
        int i;

        if (obj->gen_loader)
                return 0;

        for (i = 0; i < prog->insns_cnt; i++, insn++) {
                if (!insn_is_helper_call(insn, &func_id))
                        continue;

                /* on kernels that don't yet support
                 * bpf_probe_read_{kernel,user}[_str] helpers, fall back
                 * to bpf_probe_read() which works well for old kernels
                 */
                switch (func_id) {
                case BPF_FUNC_probe_read_kernel:
                case BPF_FUNC_probe_read_user:
                        if (!kernel_supports(obj, FEAT_PROBE_READ_KERN))
                                insn->imm = BPF_FUNC_probe_read;
                        break;
                case BPF_FUNC_probe_read_kernel_str:
                case BPF_FUNC_probe_read_user_str:
                        if (!kernel_supports(obj, FEAT_PROBE_READ_KERN))
                                insn->imm = BPF_FUNC_probe_read_str;
                        break;
                default:
                        break;
                }
        }
        return 0;
}

static int libbpf_find_attach_btf_id(struct bpf_program *prog, const char *attach_name,
                                     int *btf_obj_fd, int *btf_type_id);

/* this is called as prog->sec_def->prog_prepare_load_fn for libbpf-supported sec_defs */
static int libbpf_prepare_prog_load(struct bpf_program *prog,
                                    struct bpf_prog_load_opts *opts, long cookie)
{
        enum sec_def_flags def = cookie;

        /* old kernels might not support specifying expected_attach_type */
        if ((def & SEC_EXP_ATTACH_OPT) && !kernel_supports(prog->obj, FEAT_EXP_ATTACH_TYPE))
                opts->expected_attach_type = 0;

        if (def & SEC_SLEEPABLE)
                opts->prog_flags |= BPF_F_SLEEPABLE;

        if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_FRAGS))
                opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;

        if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
                int btf_obj_fd = 0, btf_type_id = 0, err;
                const char *attach_name;

                attach_name = strchr(prog->sec_name, '/');
                if (!attach_name) {
                        /* if BPF program is annotated with just SEC("fentry")
                         * (or similar) without declaratively specifying
                         * target, then it is expected that target will be
                         * specified with bpf_program__set_attach_target() at
                         * runtime before BPF object load step. If not, then
                         * there is nothing to load into the kernel as BPF
                         * verifier won't be able to validate BPF program
                         * correctness anyways.
                         */
                        pr_warn("prog '%s': no BTF-based attach target is specified, use bpf_program__set_attach_target()\n",
                                prog->name);
                        return -EINVAL;
                }
                attach_name++; /* skip over / */

                err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);
                if (err)
                        return err;

                /* cache resolved BTF FD and BTF type ID in the prog */
                prog->attach_btf_obj_fd = btf_obj_fd;
                prog->attach_btf_id = btf_type_id;

                /* but by now libbpf common logic is not utilizing
                 * prog->atach_btf_obj_fd/prog->attach_btf_id anymore because
                 * this callback is called after opts were populated by
                 * libbpf, so this callback has to update opts explicitly here
                 */
                opts->attach_btf_obj_fd = btf_obj_fd;
                opts->attach_btf_id = btf_type_id;
        }
        return 0;
}

static void fixup_verifier_log(struct bpf_program *prog, char *buf, size_t buf_sz);

static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog,
                                struct bpf_insn *insns, int insns_cnt,
                                const char *license, __u32 kern_version, int *prog_fd)
{
        LIBBPF_OPTS(bpf_prog_load_opts, load_attr);
        const char *prog_name = NULL;
        char *cp, errmsg[STRERR_BUFSIZE];
        size_t log_buf_size = 0;
        char *log_buf = NULL, *tmp;
        int btf_fd, ret, err;
        bool own_log_buf = true;
        __u32 log_level = prog->log_level;

        if (prog->type == BPF_PROG_TYPE_UNSPEC) {
                /*
                 * The program type must be set.  Most likely we couldn't find a proper
                 * section definition at load time, and thus we didn't infer the type.
                 */
                pr_warn("prog '%s': missing BPF prog type, check ELF section name '%s'\n",
                        prog->name, prog->sec_name);
                return -EINVAL;
        }

        if (!insns || !insns_cnt)
                return -EINVAL;

        load_attr.expected_attach_type = prog->expected_attach_type;
        if (kernel_supports(obj, FEAT_PROG_NAME))
                prog_name = prog->name;
        load_attr.attach_prog_fd = prog->attach_prog_fd;
        load_attr.attach_btf_obj_fd = prog->attach_btf_obj_fd;
        load_attr.attach_btf_id = prog->attach_btf_id;
        load_attr.kern_version = kern_version;
        load_attr.prog_ifindex = prog->prog_ifindex;

        /* specify func_info/line_info only if kernel supports them */
        btf_fd = bpf_object__btf_fd(obj);
        if (btf_fd >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) {
                load_attr.prog_btf_fd = btf_fd;
                load_attr.func_info = prog->func_info;
                load_attr.func_info_rec_size = prog->func_info_rec_size;
                load_attr.func_info_cnt = prog->func_info_cnt;
                load_attr.line_info = prog->line_info;
                load_attr.line_info_rec_size = prog->line_info_rec_size;
                load_attr.line_info_cnt = prog->line_info_cnt;
        }
        load_attr.log_level = log_level;
        load_attr.prog_flags = prog->prog_flags;
        load_attr.fd_array = obj->fd_array;

        /* adjust load_attr if sec_def provides custom preload callback */
        if (prog->sec_def && prog->sec_def->prog_prepare_load_fn) {
                err = prog->sec_def->prog_prepare_load_fn(prog, &load_attr, prog->sec_def->cookie);
                if (err < 0) {
                        pr_warn("prog '%s': failed to prepare load attributes: %d\n",
                                prog->name, err);
                        return err;
                }
                insns = prog->insns;
                insns_cnt = prog->insns_cnt;
        }

        if (obj->gen_loader) {
                bpf_gen__prog_load(obj->gen_loader, prog->type, prog->name,
                                   license, insns, insns_cnt, &load_attr,
                                   prog - obj->programs);
                *prog_fd = -1;
                return 0;
        }

retry_load:
        /* if log_level is zero, we don't request logs initially even if
         * custom log_buf is specified; if the program load fails, then we'll
         * bump log_level to 1 and use either custom log_buf or we'll allocate
         * our own and retry the load to get details on what failed
         */
        if (log_level) {
                if (prog->log_buf) {
                        log_buf = prog->log_buf;
                        log_buf_size = prog->log_size;
                        own_log_buf = false;
                } else if (obj->log_buf) {
                        log_buf = obj->log_buf;
                        log_buf_size = obj->log_size;
                        own_log_buf = false;
                } else {
                        log_buf_size = max((size_t)BPF_LOG_BUF_SIZE, log_buf_size * 2);
                        tmp = realloc(log_buf, log_buf_size);
                        if (!tmp) {
                                ret = -ENOMEM;
                                goto out;
                        }
                        log_buf = tmp;
                        log_buf[0] = '\0';
                        own_log_buf = true;
                }
        }

        load_attr.log_buf = log_buf;
        load_attr.log_size = log_buf_size;
        load_attr.log_level = log_level;

        ret = bpf_prog_load(prog->type, prog_name, license, insns, insns_cnt, &load_attr);
        if (ret >= 0) {
                if (log_level && own_log_buf) {
                        pr_debug("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
                                 prog->name, log_buf);
                }

                if (obj->has_rodata && kernel_supports(obj, FEAT_PROG_BIND_MAP)) {
                        struct bpf_map *map;
                        int i;

                        for (i = 0; i < obj->nr_maps; i++) {
                                map = &prog->obj->maps[i];
                                if (map->libbpf_type != LIBBPF_MAP_RODATA)
                                        continue;

                                if (bpf_prog_bind_map(ret, bpf_map__fd(map), NULL)) {
                                        cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
                                        pr_warn("prog '%s': failed to bind map '%s': %s\n",
                                                prog->name, map->real_name, cp);
                                        /* Don't fail hard if can't bind rodata. */
                                }
                        }
                }

                *prog_fd = ret;
                ret = 0;
                goto out;
        }

        if (log_level == 0) {
                log_level = 1;
                goto retry_load;
        }
        /* On ENOSPC, increase log buffer size and retry, unless custom
         * log_buf is specified.
         * Be careful to not overflow u32, though. Kernel's log buf size limit
         * isn't part of UAPI so it can always be bumped to full 4GB. So don't
         * multiply by 2 unless we are sure we'll fit within 32 bits.
         * Currently, we'll get -EINVAL when we reach (UINT_MAX >> 2).
         */
        if (own_log_buf && errno == ENOSPC && log_buf_size <= UINT_MAX / 2)
                goto retry_load;

        ret = -errno;

        /* post-process verifier log to improve error descriptions */
        fixup_verifier_log(prog, log_buf, log_buf_size);

        cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
        pr_warn("prog '%s': BPF program load failed: %s\n", prog->name, cp);
        pr_perm_msg(ret);

        if (own_log_buf && log_buf && log_buf[0] != '\0') {
                pr_warn("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
                        prog->name, log_buf);
        }

out:
        if (own_log_buf)
                free(log_buf);
        return ret;
}

static char *find_prev_line(char *buf, char *cur)
{
        char *p;

        if (cur == buf) /* end of a log buf */
                return NULL;

        p = cur - 1;
        while (p - 1 >= buf && *(p - 1) != '\n')
                p--;

        return p;
}

static void patch_log(char *buf, size_t buf_sz, size_t log_sz,
                      char *orig, size_t orig_sz, const char *patch)
{
        /* size of the remaining log content to the right from the to-be-replaced part */
        size_t rem_sz = (buf + log_sz) - (orig + orig_sz);
        size_t patch_sz = strlen(patch);

        if (patch_sz != orig_sz) {
                /* If patch line(s) are longer than original piece of verifier log,
                 * shift log contents by (patch_sz - orig_sz) bytes to the right
                 * starting from after to-be-replaced part of the log.
                 *
                 * If patch line(s) are shorter than original piece of verifier log,
                 * shift log contents by (orig_sz - patch_sz) bytes to the left
                 * starting from after to-be-replaced part of the log
                 *
                 * We need to be careful about not overflowing available
                 * buf_sz capacity. If that's the case, we'll truncate the end
                 * of the original log, as necessary.
                 */
                if (patch_sz > orig_sz) {
                        if (orig + patch_sz >= buf + buf_sz) {
                                /* patch is big enough to cover remaining space completely */
                                patch_sz -= (orig + patch_sz) - (buf + buf_sz) + 1;
                                rem_sz = 0;
                        } else if (patch_sz - orig_sz > buf_sz - log_sz) {
                                /* patch causes part of remaining log to be truncated */
                                rem_sz -= (patch_sz - orig_sz) - (buf_sz - log_sz);
                        }
                }
                /* shift remaining log to the right by calculated amount */
                memmove(orig + patch_sz, orig + orig_sz, rem_sz);
        }

        memcpy(orig, patch, patch_sz);
}

static void fixup_log_failed_core_relo(struct bpf_program *prog,
                                       char *buf, size_t buf_sz, size_t log_sz,
                                       char *line1, char *line2, char *line3)
{
        /* Expected log for failed and not properly guarded CO-RE relocation:
         * line1 -> 123: (85) call unknown#195896080
         * line2 -> invalid func unknown#195896080
         * line3 -> <anything else or end of buffer>
         *
         * "123" is the index of the instruction that was poisoned. We extract
         * instruction index to find corresponding CO-RE relocation and
         * replace this part of the log with more relevant information about
         * failed CO-RE relocation.
         */
        const struct bpf_core_relo *relo;
        struct bpf_core_spec spec;
        char patch[512], spec_buf[256];
        int insn_idx, err, spec_len;

        if (sscanf(line1, "%d: (%*d) call unknown#195896080\n", &insn_idx) != 1)
                return;

        relo = find_relo_core(prog, insn_idx);
        if (!relo)
                return;

        err = bpf_core_parse_spec(prog->name, prog->obj->btf, relo, &spec);
        if (err)
                return;

        spec_len = bpf_core_format_spec(spec_buf, sizeof(spec_buf), &spec);
        snprintf(patch, sizeof(patch),
                 "%d: <invalid CO-RE relocation>\n"
                 "failed to resolve CO-RE relocation %s%s\n",
                 insn_idx, spec_buf, spec_len >= sizeof(spec_buf) ? "..." : "");

        patch_log(buf, buf_sz, log_sz, line1, line3 - line1, patch);
}

static void fixup_log_missing_map_load(struct bpf_program *prog,
                                       char *buf, size_t buf_sz, size_t log_sz,
                                       char *line1, char *line2, char *line3)
{
        /* Expected log for failed and not properly guarded map reference:
         * line1 -> 123: (85) call unknown#2001000345
         * line2 -> invalid func unknown#2001000345
         * line3 -> <anything else or end of buffer>
         *
         * "123" is the index of the instruction that was poisoned.
         * "345" in "2001000345" is a map index in obj->maps to fetch map name.
         */
        struct bpf_object *obj = prog->obj;
        const struct bpf_map *map;
        int insn_idx, map_idx;
        char patch[128];

        if (sscanf(line1, "%d: (%*d) call unknown#%d\n", &insn_idx, &map_idx) != 2)
                return;

        map_idx -= POISON_LDIMM64_MAP_BASE;
        if (map_idx < 0 || map_idx >= obj->nr_maps)
                return;
        map = &obj->maps[map_idx];

        snprintf(patch, sizeof(patch),
                 "%d: <invalid BPF map reference>\n"
                 "BPF map '%s' is referenced but wasn't created\n",
                 insn_idx, map->name);

        patch_log(buf, buf_sz, log_sz, line1, line3 - line1, patch);
}

static void fixup_log_missing_kfunc_call(struct bpf_program *prog,
                                         char *buf, size_t buf_sz, size_t log_sz,
                                         char *line1, char *line2, char *line3)
{
        /* Expected log for failed and not properly guarded kfunc call:
         * line1 -> 123: (85) call unknown#2002000345
         * line2 -> invalid func unknown#2002000345
         * line3 -> <anything else or end of buffer>
         *
         * "123" is the index of the instruction that was poisoned.
         * "345" in "2002000345" is an extern index in obj->externs to fetch kfunc name.
         */
        struct bpf_object *obj = prog->obj;
        const struct extern_desc *ext;
        int insn_idx, ext_idx;
        char patch[128];

        if (sscanf(line1, "%d: (%*d) call unknown#%d\n", &insn_idx, &ext_idx) != 2)
                return;

        ext_idx -= POISON_CALL_KFUNC_BASE;
        if (ext_idx < 0 || ext_idx >= obj->nr_extern)
                return;
        ext = &obj->externs[ext_idx];

        snprintf(patch, sizeof(patch),
                 "%d: <invalid kfunc call>\n"
                 "kfunc '%s' is referenced but wasn't resolved\n",
                 insn_idx, ext->name);

        patch_log(buf, buf_sz, log_sz, line1, line3 - line1, patch);
}

static void fixup_verifier_log(struct bpf_program *prog, char *buf, size_t buf_sz)
{
        /* look for familiar error patterns in last N lines of the log */
        const size_t max_last_line_cnt = 10;
        char *prev_line, *cur_line, *next_line;
        size_t log_sz;
        int i;

        if (!buf)
                return;

        log_sz = strlen(buf) + 1;
        next_line = buf + log_sz - 1;

        for (i = 0; i < max_last_line_cnt; i++, next_line = cur_line) {
                cur_line = find_prev_line(buf, next_line);
                if (!cur_line)
                        return;

                if (str_has_pfx(cur_line, "invalid func unknown#195896080\n")) {
                        prev_line = find_prev_line(buf, cur_line);
                        if (!prev_line)
                                continue;

                        /* failed CO-RE relocation case */
                        fixup_log_failed_core_relo(prog, buf, buf_sz, log_sz,
                                                   prev_line, cur_line, next_line);
                        return;
                } else if (str_has_pfx(cur_line, "invalid func unknown#"POISON_LDIMM64_MAP_PFX)) {
                        prev_line = find_prev_line(buf, cur_line);
                        if (!prev_line)
                                continue;

                        /* reference to uncreated BPF map */
                        fixup_log_missing_map_load(prog, buf, buf_sz, log_sz,
                                                   prev_line, cur_line, next_line);
                        return;
                } else if (str_has_pfx(cur_line, "invalid func unknown#"POISON_CALL_KFUNC_PFX)) {
                        prev_line = find_prev_line(buf, cur_line);
                        if (!prev_line)
                                continue;

                        /* reference to unresolved kfunc */
                        fixup_log_missing_kfunc_call(prog, buf, buf_sz, log_sz,
                                                     prev_line, cur_line, next_line);
                        return;
                }
        }
}

static int bpf_program_record_relos(struct bpf_program *prog)
{
        struct bpf_object *obj = prog->obj;
        int i;

        for (i = 0; i < prog->nr_reloc; i++) {
                struct reloc_desc *relo = &prog->reloc_desc[i];
                struct extern_desc *ext = &obj->externs[relo->ext_idx];
                int kind;

                switch (relo->type) {
                case RELO_EXTERN_LD64:
                        if (ext->type != EXT_KSYM)
                                continue;
                        kind = btf_is_var(btf__type_by_id(obj->btf, ext->btf_id)) ?
                                BTF_KIND_VAR : BTF_KIND_FUNC;
                        bpf_gen__record_extern(obj->gen_loader, ext->name,
                                               ext->is_weak, !ext->ksym.type_id,
                                               true, kind, relo->insn_idx);
                        break;
                case RELO_EXTERN_CALL:
                        bpf_gen__record_extern(obj->gen_loader, ext->name,
                                               ext->is_weak, false, false, BTF_KIND_FUNC,
                                               relo->insn_idx);
                        break;
                case RELO_CORE: {
                        struct bpf_core_relo cr = {
                                .insn_off = relo->insn_idx * 8,
                                .type_id = relo->core_relo->type_id,
                                .access_str_off = relo->core_relo->access_str_off,
                                .kind = relo->core_relo->kind,
                        };

                        bpf_gen__record_relo_core(obj->gen_loader, &cr);
                        break;
                }
                default:
                        continue;
                }
        }
        return 0;
}

static int
bpf_object__load_progs(struct bpf_object *obj, int log_level)
{
        struct bpf_program *prog;
        size_t i;
        int err;

        for (i = 0; i < obj->nr_programs; i++) {
                prog = &obj->programs[i];
                err = bpf_object__sanitize_prog(obj, prog);
                if (err)
                        return err;
        }

        for (i = 0; i < obj->nr_programs; i++) {
                prog = &obj->programs[i];
                if (prog_is_subprog(obj, prog))
                        continue;
                if (!prog->autoload) {
                        pr_debug("prog '%s': skipped loading\n", prog->name);
                        continue;
                }
                prog->log_level |= log_level;

                if (obj->gen_loader)
                        bpf_program_record_relos(prog);

                err = bpf_object_load_prog(obj, prog, prog->insns, prog->insns_cnt,
                                           obj->license, obj->kern_version, &prog->fd);
                if (err) {
                        pr_warn("prog '%s': failed to load: %d\n", prog->name, err);
                        return err;
                }
        }

        bpf_object__free_relocs(obj);
        return 0;
}

static const struct bpf_sec_def *find_sec_def(const char *sec_name);

static int bpf_object_init_progs(struct bpf_object *obj, const struct bpf_object_open_opts *opts)
{
        struct bpf_program *prog;
        int err;

        bpf_object__for_each_program(prog, obj) {
                prog->sec_def = find_sec_def(prog->sec_name);
                if (!prog->sec_def) {
                        /* couldn't guess, but user might manually specify */
                        pr_debug("prog '%s': unrecognized ELF section name '%s'\n",
                                prog->name, prog->sec_name);
                        continue;
                }

                prog->type = prog->sec_def->prog_type;
                prog->expected_attach_type = prog->sec_def->expected_attach_type;

                /* sec_def can have custom callback which should be called
                 * after bpf_program is initialized to adjust its properties
                 */
                if (prog->sec_def->prog_setup_fn) {
                        err = prog->sec_def->prog_setup_fn(prog, prog->sec_def->cookie);
                        if (err < 0) {
                                pr_warn("prog '%s': failed to initialize: %d\n",
                                        prog->name, err);
                                return err;
                        }
                }
        }

        return 0;
}

static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf, size_t obj_buf_sz,
                                          const struct bpf_object_open_opts *opts)
{
        const char *obj_name, *kconfig, *btf_tmp_path;
        struct bpf_object *obj;
        char tmp_name[64];
        int err;
        char *log_buf;
        size_t log_size;
        __u32 log_level;

        if (elf_version(EV_CURRENT) == EV_NONE) {
                pr_warn("failed to init libelf for %s\n",
                        path ? : "(mem buf)");
                return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
        }

        if (!OPTS_VALID(opts, bpf_object_open_opts))
                return ERR_PTR(-EINVAL);

        obj_name = OPTS_GET(opts, object_name, NULL);
        if (obj_buf) {
                if (!obj_name) {
                        snprintf(tmp_name, sizeof(tmp_name), "%lx-%lx",
                                 (unsigned long)obj_buf,
                                 (unsigned long)obj_buf_sz);
                        obj_name = tmp_name;
                }
                path = obj_name;
                pr_debug("loading object '%s' from buffer\n", obj_name);
        }

        log_buf = OPTS_GET(opts, kernel_log_buf, NULL);
        log_size = OPTS_GET(opts, kernel_log_size, 0);
        log_level = OPTS_GET(opts, kernel_log_level, 0);
        if (log_size > UINT_MAX)
                return ERR_PTR(-EINVAL);
        if (log_size && !log_buf)
                return ERR_PTR(-EINVAL);

        obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name);
        if (IS_ERR(obj))
                return obj;

        obj->log_buf = log_buf;
        obj->log_size = log_size;
        obj->log_level = log_level;

        btf_tmp_path = OPTS_GET(opts, btf_custom_path, NULL);
        if (btf_tmp_path) {
                if (strlen(btf_tmp_path) >= PATH_MAX) {
                        err = -ENAMETOOLONG;
                        goto out;
                }
                obj->btf_custom_path = strdup(btf_tmp_path);
                if (!obj->btf_custom_path) {
                        err = -ENOMEM;
                        goto out;
                }
        }

        kconfig = OPTS_GET(opts, kconfig, NULL);
        if (kconfig) {
                obj->kconfig = strdup(kconfig);
                if (!obj->kconfig) {
                        err = -ENOMEM;
                        goto out;
                }
        }

        err = bpf_object__elf_init(obj);
        err = err ? : bpf_object__check_endianness(obj);
        err = err ? : bpf_object__elf_collect(obj);
        err = err ? : bpf_object__collect_externs(obj);
        err = err ? : bpf_object_fixup_btf(obj);
        err = err ? : bpf_object__init_maps(obj, opts);
        err = err ? : bpf_object_init_progs(obj, opts);
        err = err ? : bpf_object__collect_relos(obj);
        if (err)
                goto out;

        bpf_object__elf_finish(obj);

        return obj;
out:
        bpf_object__close(obj);
        return ERR_PTR(err);
}

struct bpf_object *
bpf_object__open_file(const char *path, const struct bpf_object_open_opts *opts)
{
        if (!path)
                return libbpf_err_ptr(-EINVAL);

        pr_debug("loading %s\n", path);

        return libbpf_ptr(bpf_object_open(path, NULL, 0, opts));
}

struct bpf_object *bpf_object__open(const char *path)
{
        return bpf_object__open_file(path, NULL);
}

struct bpf_object *
bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
                     const struct bpf_object_open_opts *opts)
{
        if (!obj_buf || obj_buf_sz == 0)
                return libbpf_err_ptr(-EINVAL);

        return libbpf_ptr(bpf_object_open(NULL, obj_buf, obj_buf_sz, opts));
}

static int bpf_object_unload(struct bpf_object *obj)
{
        size_t i;

        if (!obj)
                return libbpf_err(-EINVAL);

        for (i = 0; i < obj->nr_maps; i++) {
                zclose(obj->maps[i].fd);
                if (obj->maps[i].st_ops)
                        zfree(&obj->maps[i].st_ops->kern_vdata);
        }

        for (i = 0; i < obj->nr_programs; i++)
                bpf_program__unload(&obj->programs[i]);

        return 0;
}

static int bpf_object__sanitize_maps(struct bpf_object *obj)
{
        struct bpf_map *m;

        bpf_object__for_each_map(m, obj) {
                if (!bpf_map__is_internal(m))
                        continue;
                if (!kernel_supports(obj, FEAT_ARRAY_MMAP))
                        m->def.map_flags &= ~BPF_F_MMAPABLE;
        }

        return 0;
}

int libbpf_kallsyms_parse(kallsyms_cb_t cb, void *ctx)
{
        char sym_type, sym_name[500];
        unsigned long long sym_addr;
        int ret, err = 0;
        FILE *f;

        f = fopen("/proc/kallsyms", "r");
        if (!f) {
                err = -errno;
                pr_warn("failed to open /proc/kallsyms: %d\n", err);
                return err;
        }

        while (true) {
                ret = fscanf(f, "%llx %c %499s%*[^\n]\n",
                             &sym_addr, &sym_type, sym_name);
                if (ret == EOF && feof(f))
                        break;
                if (ret != 3) {
                        pr_warn("failed to read kallsyms entry: %d\n", ret);
                        err = -EINVAL;
                        break;
                }

                err = cb(sym_addr, sym_type, sym_name, ctx);
                if (err)
                        break;
        }

        fclose(f);
        return err;
}

static int kallsyms_cb(unsigned long long sym_addr, char sym_type,
                       const char *sym_name, void *ctx)
{
        struct bpf_object *obj = ctx;
        const struct btf_type *t;
        struct extern_desc *ext;

        ext = find_extern_by_name(obj, sym_name);
        if (!ext || ext->type != EXT_KSYM)
                return 0;

        t = btf__type_by_id(obj->btf, ext->btf_id);
        if (!btf_is_var(t))
                return 0;

        if (ext->is_set && ext->ksym.addr != sym_addr) {
                pr_warn("extern (ksym) '%s': resolution is ambiguous: 0x%llx or 0x%llx\n",
                        sym_name, ext->ksym.addr, sym_addr);
                return -EINVAL;
        }
        if (!ext->is_set) {
                ext->is_set = true;
                ext->ksym.addr = sym_addr;
                pr_debug("extern (ksym) '%s': set to 0x%llx\n", sym_name, sym_addr);
        }
        return 0;
}

static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
{
        return libbpf_kallsyms_parse(kallsyms_cb, obj);
}

static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
                            __u16 kind, struct btf **res_btf,
                            struct module_btf **res_mod_btf)
{
        struct module_btf *mod_btf;
        struct btf *btf;
        int i, id, err;

        btf = obj->btf_vmlinux;
        mod_btf = NULL;
        id = btf__find_by_name_kind(btf, ksym_name, kind);

        if (id == -ENOENT) {
                err = load_module_btfs(obj);
                if (err)
                        return err;

                for (i = 0; i < obj->btf_module_cnt; i++) {
                        /* we assume module_btf's BTF FD is always >0 */
                        mod_btf = &obj->btf_modules[i];
                        btf = mod_btf->btf;
                        id = btf__find_by_name_kind_own(btf, ksym_name, kind);
                        if (id != -ENOENT)
                                break;
                }
        }
        if (id <= 0)
                return -ESRCH;

        *res_btf = btf;
        *res_mod_btf = mod_btf;
        return id;
}

static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
                                               struct extern_desc *ext)
{
        const struct btf_type *targ_var, *targ_type;
        __u32 targ_type_id, local_type_id;
        struct module_btf *mod_btf = NULL;
        const char *targ_var_name;
        struct btf *btf = NULL;
        int id, err;

        id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &mod_btf);
        if (id < 0) {
                if (id == -ESRCH && ext->is_weak)
                        return 0;
                pr_warn("extern (var ksym) '%s': not found in kernel BTF\n",
                        ext->name);
                return id;
        }

        /* find local type_id */
        local_type_id = ext->ksym.type_id;

        /* find target type_id */
        targ_var = btf__type_by_id(btf, id);
        targ_var_name = btf__name_by_offset(btf, targ_var->name_off);
        targ_type = skip_mods_and_typedefs(btf, targ_var->type, &targ_type_id);

        err = bpf_core_types_are_compat(obj->btf, local_type_id,
                                        btf, targ_type_id);
        if (err <= 0) {
                const struct btf_type *local_type;
                const char *targ_name, *local_name;

                local_type = btf__type_by_id(obj->btf, local_type_id);
                local_name = btf__name_by_offset(obj->btf, local_type->name_off);
                targ_name = btf__name_by_offset(btf, targ_type->name_off);

                pr_warn("extern (var ksym) '%s': incompatible types, expected [%d] %s %s, but kernel has [%d] %s %s\n",
                        ext->name, local_type_id,
                        btf_kind_str(local_type), local_name, targ_type_id,
                        btf_kind_str(targ_type), targ_name);
                return -EINVAL;
        }

        ext->is_set = true;
        ext->ksym.kernel_btf_obj_fd = mod_btf ? mod_btf->fd : 0;
        ext->ksym.kernel_btf_id = id;
        pr_debug("extern (var ksym) '%s': resolved to [%d] %s %s\n",
                 ext->name, id, btf_kind_str(targ_var), targ_var_name);

        return 0;
}

static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
                                                struct extern_desc *ext)
{
        int local_func_proto_id, kfunc_proto_id, kfunc_id;
        struct module_btf *mod_btf = NULL;
        const struct btf_type *kern_func;
        struct btf *kern_btf = NULL;
        int ret;

        local_func_proto_id = ext->ksym.type_id;

        kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, &kern_btf, &mod_btf);
        if (kfunc_id < 0) {
                if (kfunc_id == -ESRCH && ext->is_weak)
                        return 0;
                pr_warn("extern (func ksym) '%s': not found in kernel or module BTFs\n",
                        ext->name);
                return kfunc_id;
        }

        kern_func = btf__type_by_id(kern_btf, kfunc_id);
        kfunc_proto_id = kern_func->type;

        ret = bpf_core_types_are_compat(obj->btf, local_func_proto_id,
                                        kern_btf, kfunc_proto_id);
        if (ret <= 0) {
                pr_warn("extern (func ksym) '%s': func_proto [%d] incompatible with %s [%d]\n",
                        ext->name, local_func_proto_id,
                        mod_btf ? mod_btf->name : "vmlinux", kfunc_proto_id);
                return -EINVAL;
        }

        /* set index for module BTF fd in fd_array, if unset */
        if (mod_btf && !mod_btf->fd_array_idx) {
                /* insn->off is s16 */
                if (obj->fd_array_cnt == INT16_MAX) {
                        pr_warn("extern (func ksym) '%s': module BTF fd index %d too big to fit in bpf_insn offset\n",
                                ext->name, mod_btf->fd_array_idx);
                        return -E2BIG;
                }
                /* Cannot use index 0 for module BTF fd */
                if (!obj->fd_array_cnt)
                        obj->fd_array_cnt = 1;

                ret = libbpf_ensure_mem((void **)&obj->fd_array, &obj->fd_array_cap, sizeof(int),
                                        obj->fd_array_cnt + 1);
                if (ret)
                        return ret;
                mod_btf->fd_array_idx = obj->fd_array_cnt;
                /* we assume module BTF FD is always >0 */
                obj->fd_array[obj->fd_array_cnt++] = mod_btf->fd;
        }

        ext->is_set = true;
        ext->ksym.kernel_btf_id = kfunc_id;
        ext->ksym.btf_fd_idx = mod_btf ? mod_btf->fd_array_idx : 0;
        /* Also set kernel_btf_obj_fd to make sure that bpf_object__relocate_data()
         * populates FD into ld_imm64 insn when it's used to point to kfunc.
         * {kernel_btf_id, btf_fd_idx} -> fixup bpf_call.
         * {kernel_btf_id, kernel_btf_obj_fd} -> fixup ld_imm64.
         */
        ext->ksym.kernel_btf_obj_fd = mod_btf ? mod_btf->fd : 0;
        pr_debug("extern (func ksym) '%s': resolved to %s [%d]\n",
                 ext->name, mod_btf ? mod_btf->name : "vmlinux", kfunc_id);

        return 0;
}

static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
{
        const struct btf_type *t;
        struct extern_desc *ext;
        int i, err;

        for (i = 0; i < obj->nr_extern; i++) {
                ext = &obj->externs[i];
                if (ext->type != EXT_KSYM || !ext->ksym.type_id)
                        continue;

                if (obj->gen_loader) {
                        ext->is_set = true;
                        ext->ksym.kernel_btf_obj_fd = 0;
                        ext->ksym.kernel_btf_id = 0;
                        continue;
                }
                t = btf__type_by_id(obj->btf, ext->btf_id);
                if (btf_is_var(t))
                        err = bpf_object__resolve_ksym_var_btf_id(obj, ext);
                else
                        err = bpf_object__resolve_ksym_func_btf_id(obj, ext);
                if (err)
                        return err;
        }
        return 0;
}

static int bpf_object__resolve_externs(struct bpf_object *obj,
                                       const char *extra_kconfig)
{
        bool need_config = false, need_kallsyms = false;
        bool need_vmlinux_btf = false;
        struct extern_desc *ext;
        void *kcfg_data = NULL;
        int err, i;

        if (obj->nr_extern == 0)
                return 0;

        if (obj->kconfig_map_idx >= 0)
                kcfg_data = obj->maps[obj->kconfig_map_idx].mmaped;

        for (i = 0; i < obj->nr_extern; i++) {
                ext = &obj->externs[i];

                if (ext->type == EXT_KSYM) {
                        if (ext->ksym.type_id)
                                need_vmlinux_btf = true;
                        else
                                need_kallsyms = true;
                        continue;
                } else if (ext->type == EXT_KCFG) {
                        void *ext_ptr = kcfg_data + ext->kcfg.data_off;
                        __u64 value = 0;

                        /* Kconfig externs need actual /proc/config.gz */
                        if (str_has_pfx(ext->name, "CONFIG_")) {
                                need_config = true;
                                continue;
                        }

                        /* Virtual kcfg externs are customly handled by libbpf */
                        if (strcmp(ext->name, "LINUX_KERNEL_VERSION") == 0) {
                                value = get_kernel_version();
                                if (!value) {
                                        pr_warn("extern (kcfg) '%s': failed to get kernel version\n", ext->name);
                                        return -EINVAL;
                                }
                        } else if (strcmp(ext->name, "LINUX_HAS_BPF_COOKIE") == 0) {
                                value = kernel_supports(obj, FEAT_BPF_COOKIE);
                        } else if (strcmp(ext->name, "LINUX_HAS_SYSCALL_WRAPPER") == 0) {
                                value = kernel_supports(obj, FEAT_SYSCALL_WRAPPER);
                        } else if (!str_has_pfx(ext->name, "LINUX_") || !ext->is_weak) {
                                /* Currently libbpf supports only CONFIG_ and LINUX_ prefixed
                                 * __kconfig externs, where LINUX_ ones are virtual and filled out
                                 * customly by libbpf (their values don't come from Kconfig).
                                 * If LINUX_xxx variable is not recognized by libbpf, but is marked
                                 * __weak, it defaults to zero value, just like for CONFIG_xxx
                                 * externs.
                                 */
                                pr_warn("extern (kcfg) '%s': unrecognized virtual extern\n", ext->name);
                                return -EINVAL;
                        }

                        err = set_kcfg_value_num(ext, ext_ptr, value);
                        if (err)
                                return err;
                        pr_debug("extern (kcfg) '%s': set to 0x%llx\n",
                                 ext->name, (long long)value);
                } else {
                        pr_warn("extern '%s': unrecognized extern kind\n", ext->name);
                        return -EINVAL;
                }
        }
        if (need_config && extra_kconfig) {
                err = bpf_object__read_kconfig_mem(obj, extra_kconfig, kcfg_data);
                if (err)
                        return -EINVAL;
                need_config = false;
                for (i = 0; i < obj->nr_extern; i++) {
                        ext = &obj->externs[i];
                        if (ext->type == EXT_KCFG && !ext->is_set) {
                                need_config = true;
                                break;
                        }
                }
        }
        if (need_config) {
                err = bpf_object__read_kconfig_file(obj, kcfg_data);
                if (err)
                        return -EINVAL;
        }
        if (need_kallsyms) {
                err = bpf_object__read_kallsyms_file(obj);
                if (err)
                        return -EINVAL;
        }
        if (need_vmlinux_btf) {
                err = bpf_object__resolve_ksyms_btf_id(obj);
                if (err)
                        return -EINVAL;
        }
        for (i = 0; i < obj->nr_extern; i++) {
                ext = &obj->externs[i];

                if (!ext->is_set && !ext->is_weak) {
                        pr_warn("extern '%s' (strong): not resolved\n", ext->name);
                        return -ESRCH;
                } else if (!ext->is_set) {
                        pr_debug("extern '%s' (weak): not resolved, defaulting to zero\n",
                                 ext->name);
                }
        }

        return 0;
}

static void bpf_map_prepare_vdata(const struct bpf_map *map)
{
        struct bpf_struct_ops *st_ops;
        __u32 i;

        st_ops = map->st_ops;
        for (i = 0; i < btf_vlen(st_ops->type); i++) {
                struct bpf_program *prog = st_ops->progs[i];
                void *kern_data;
                int prog_fd;

                if (!prog)
                        continue;

                prog_fd = bpf_program__fd(prog);
                kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i];
                *(unsigned long *)kern_data = prog_fd;
        }
}

static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
{
        int i;

        for (i = 0; i < obj->nr_maps; i++)
                if (bpf_map__is_struct_ops(&obj->maps[i]))
                        bpf_map_prepare_vdata(&obj->maps[i]);

        return 0;
}

static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path)
{
        int err, i;

        if (!obj)
                return libbpf_err(-EINVAL);

        if (obj->loaded) {
                pr_warn("object '%s': load can't be attempted twice\n", obj->name);
                return libbpf_err(-EINVAL);
        }

        if (obj->gen_loader)
                bpf_gen__init(obj->gen_loader, extra_log_level, obj->nr_programs, obj->nr_maps);

        err = bpf_object__probe_loading(obj);
        err = err ? : bpf_object__load_vmlinux_btf(obj, false);
        err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
        err = err ? : bpf_object__sanitize_and_load_btf(obj);
        err = err ? : bpf_object__sanitize_maps(obj);
        err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
        err = err ? : bpf_object__create_maps(obj);
        err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : target_btf_path);
        err = err ? : bpf_object__load_progs(obj, extra_log_level);
        err = err ? : bpf_object_init_prog_arrays(obj);
        err = err ? : bpf_object_prepare_struct_ops(obj);

        if (obj->gen_loader) {
                /* reset FDs */
                if (obj->btf)
                        btf__set_fd(obj->btf, -1);
                for (i = 0; i < obj->nr_maps; i++)
                        obj->maps[i].fd = -1;
                if (!err)
                        err = bpf_gen__finish(obj->gen_loader, obj->nr_programs, obj->nr_maps);
        }

        /* clean up fd_array */
        zfree(&obj->fd_array);

        /* clean up module BTFs */
        for (i = 0; i < obj->btf_module_cnt; i++) {
                close(obj->btf_modules[i].fd);
                btf__free(obj->btf_modules[i].btf);
                free(obj->btf_modules[i].name);
        }
        free(obj->btf_modules);

        /* clean up vmlinux BTF */
        btf__free(obj->btf_vmlinux);
        obj->btf_vmlinux = NULL;

        obj->loaded = true; /* doesn't matter if successfully or not */

        if (err)
                goto out;

        return 0;
out:
        /* unpin any maps that were auto-pinned during load */
        for (i = 0; i < obj->nr_maps; i++)
                if (obj->maps[i].pinned && !obj->maps[i].reused)
                        bpf_map__unpin(&obj->maps[i], NULL);

        bpf_object_unload(obj);
        pr_warn("failed to load object '%s'\n", obj->path);
        return libbpf_err(err);
}

int bpf_object__load(struct bpf_object *obj)
{
        return bpf_object_load(obj, 0, NULL);
}

static int make_parent_dir(const char *path)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        char *dname, *dir;
        int err = 0;

        dname = strdup(path);
        if (dname == NULL)
                return -ENOMEM;

        dir = dirname(dname);
        if (mkdir(dir, 0700) && errno != EEXIST)
                err = -errno;

        free(dname);
        if (err) {
                cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
                pr_warn("failed to mkdir %s: %s\n", path, cp);
        }
        return err;
}

static int check_path(const char *path)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        struct statfs st_fs;
        char *dname, *dir;
        int err = 0;

        if (path == NULL)
                return -EINVAL;

        dname = strdup(path);
        if (dname == NULL)
                return -ENOMEM;

        dir = dirname(dname);
        if (statfs(dir, &st_fs)) {
                cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
                pr_warn("failed to statfs %s: %s\n", dir, cp);
                err = -errno;
        }
        free(dname);

        if (!err && st_fs.f_type != BPF_FS_MAGIC) {
                pr_warn("specified path %s is not on BPF FS\n", path);
                err = -EINVAL;
        }

        return err;
}

int bpf_program__pin(struct bpf_program *prog, const char *path)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        int err;

        if (prog->fd < 0) {
                pr_warn("prog '%s': can't pin program that wasn't loaded\n", prog->name);
                return libbpf_err(-EINVAL);
        }

        err = make_parent_dir(path);
        if (err)
                return libbpf_err(err);

        err = check_path(path);
        if (err)
                return libbpf_err(err);

        if (bpf_obj_pin(prog->fd, path)) {
                err = -errno;
                cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
                pr_warn("prog '%s': failed to pin at '%s': %s\n", prog->name, path, cp);
                return libbpf_err(err);
        }

        pr_debug("prog '%s': pinned at '%s'\n", prog->name, path);
        return 0;
}

int bpf_program__unpin(struct bpf_program *prog, const char *path)
{
        int err;

        if (prog->fd < 0) {
                pr_warn("prog '%s': can't unpin program that wasn't loaded\n", prog->name);
                return libbpf_err(-EINVAL);
        }

        err = check_path(path);
        if (err)
                return libbpf_err(err);

        err = unlink(path);
        if (err)
                return libbpf_err(-errno);

        pr_debug("prog '%s': unpinned from '%s'\n", prog->name, path);
        return 0;
}

int bpf_map__pin(struct bpf_map *map, const char *path)
{
        char *cp, errmsg[STRERR_BUFSIZE];
        int err;

        if (map == NULL) {
                pr_warn("invalid map pointer\n");
                return libbpf_err(-EINVAL);
        }

        if (map->pin_path) {
                if (path && strcmp(path, map->pin_path)) {
                        pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
                                bpf_map__name(map), map->pin_path, path);
                        return libbpf_err(-EINVAL);
                } else if (map->pinned) {
                        pr_debug("map '%s' already pinned at '%s'; not re-pinning\n",
                                 bpf_map__name(map), map->pin_path);
                        return 0;
                }
        } else {
                if (!path) {
                        pr_warn("missing a path to pin map '%s' at\n",
                                bpf_map__name(map));
                        return libbpf_err(-EINVAL);
                } else if (map->pinned) {
                        pr_warn("map '%s' already pinned\n", bpf_map__name(map));
                        return libbpf_err(-EEXIST);
                }

                map->pin_path = strdup(path);
                if (!map->pin_path) {
                        err = -errno;
                        goto out_err;
                }
        }

        err = make_parent_dir(map->pin_path);
        if (err)
                return libbpf_err(err);

        err = check_path(map->pin_path);
        if (err)
                return libbpf_err(err);

        if (bpf_obj_pin(map->fd, map->pin_path)) {
                err = -errno;
                goto out_err;
        }

        map->pinned = true;
        pr_debug("pinned map '%s'\n", map->pin_path);

        return 0;

out_err:
        cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
        pr_warn("failed to pin map: %s\n", cp);
        return libbpf_err(err);
}

int bpf_map__unpin(struct bpf_map *map, const char *path)
{
        int err;

        if (map == NULL) {
                pr_warn("invalid map pointer\n");
                return libbpf_err(-EINVAL);
        }

        if (map->pin_path) {
                if (path && strcmp(path, map->pin_path)) {
                        pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
                                bpf_map__name(map), map->pin_path, path);
                        return libbpf_err(-EINVAL);
                }
                path = map->pin_path;
        } else if (!path) {
                pr_warn("no path to unpin map '%s' from\n",
                        bpf_map__name(map));
                return libbpf_err(-EINVAL);
        }

        err = check_path(path);
        if (err)
                return libbpf_err(err);

        err = unlink(path);
        if (err != 0)
                return libbpf_err(-errno);

        map->pinned = false;
        pr_debug("unpinned map '%s' from '%s'\n", bpf_map__name(map), path);

        return 0;
}

int bpf_map__set_pin_path(struct bpf_map *map, const char *path)
{
        char *new = NULL;

        if (path) {
                new = strdup(path);
                if (!new)
                        return libbpf_err(-errno);
        }

        free(map->pin_path);
        map->pin_path = new;
        return 0;
}

__alias(bpf_map__pin_path)
const char *bpf_map__get_pin_path(const struct bpf_map *map);

const char *bpf_map__pin_path(const struct bpf_map *map)
{
        return map->pin_path;
}

bool bpf_map__is_pinned(const struct bpf_map *map)
{
        return map->pinned;
}

static void sanitize_pin_path(char *s)
{
        /* bpffs disallows periods in path names */
        while (*s) {
                if (*s == '.')
                        *s = '_';
                s++;
        }
}

int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
{
        struct bpf_map *map;
        int err;

        if (!obj)
                return libbpf_err(-ENOENT);

        if (!obj->loaded) {
                pr_warn("object not yet loaded; load it first\n");
                return libbpf_err(-ENOENT);
        }

        bpf_object__for_each_map(map, obj) {
                char *pin_path = NULL;
                char buf[PATH_MAX];

                if (!map->autocreate)
                        continue;

                if (path) {
                        err = pathname_concat(buf, sizeof(buf), path, bpf_map__name(map));
                        if (err)
                                goto err_unpin_maps;
                        sanitize_pin_path(buf);
                        pin_path = buf;
                } else if (!map->pin_path) {
                        continue;
                }

                err = bpf_map__pin(map, pin_path);
                if (err)
                        goto err_unpin_maps;
        }

        return 0;

err_unpin_maps:
        while ((map = bpf_object__prev_map(obj, map))) {
                if (!map->pin_path)
                        continue;

                bpf_map__unpin(map, NULL);
        }

        return libbpf_err(err);
}

int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
{
        struct bpf_map *map;
        int err;

        if (!obj)
                return libbpf_err(-ENOENT);

        bpf_object__for_each_map(map, obj) {
                char *pin_path = NULL;
                char buf[PATH_MAX];

                if (path) {
                        err = pathname_concat(buf, sizeof(buf), path, bpf_map__name(map));
                        if (err)
                                return libbpf_err(err);
                        sanitize_pin_path(buf);
                        pin_path = buf;
                } else if (!map->pin_path) {
                        continue;
                }

                err = bpf_map__unpin(map, pin_path);
                if (err)
                        return libbpf_err(err);
        }

        return 0;
}

int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
{
        struct bpf_program *prog;
        char buf[PATH_MAX];
        int err;

        if (!obj)
                return libbpf_err(-ENOENT);

        if (!obj->loaded) {
                pr_warn("object not yet loaded; load it first\n");
                return libbpf_err(-ENOENT);
        }

        bpf_object__for_each_program(prog, obj) {
                err = pathname_concat(buf, sizeof(buf), path, prog->name);
                if (err)
                        goto err_unpin_programs;

                err = bpf_program__pin(prog, buf);
                if (err)
                        goto err_unpin_programs;
        }

        return 0;

err_unpin_programs:
        while ((prog = bpf_object__prev_program(obj, prog))) {
                if (pathname_concat(buf, sizeof(buf), path, prog->name))
                        continue;

                bpf_program__unpin(prog, buf);
        }

        return libbpf_err(err);
}

int bpf_object__unpin_programs(struct bpf_object *obj, const char *path)
{
        struct bpf_program *prog;
        int err;

        if (!obj)
                return libbpf_err(-ENOENT);

        bpf_object__for_each_program(prog, obj) {
                char buf[PATH_MAX];

                err = pathname_concat(buf, sizeof(buf), path, prog->name);
                if (err)
                        return libbpf_err(err);

                err = bpf_program__unpin(prog, buf);
                if (err)
                        return libbpf_err(err);
        }

        return 0;
}

int bpf_object__pin(struct bpf_object *obj, const char *path)
{
        int err;

        err = bpf_object__pin_maps(obj, path);
        if (err)
                return libbpf_err(err);

        err = bpf_object__pin_programs(obj, path);
        if (err) {
                bpf_object__unpin_maps(obj, path);
                return libbpf_err(err);
        }

        return 0;
}

static void bpf_map__destroy(struct bpf_map *map)
{
        if (map->inner_map) {
                bpf_map__destroy(map->inner_map);
                zfree(&map->inner_map);
        }

        zfree(&map->init_slots);
        map->init_slots_sz = 0;

        if (map->mmaped) {
                munmap(map->mmaped, bpf_map_mmap_sz(map));
                map->mmaped = NULL;
        }

        if (map->st_ops) {
                zfree(&map->st_ops->data);
                zfree(&map->st_ops->progs);
                zfree(&map->st_ops->kern_func_off);
                zfree(&map->st_ops);
        }

        zfree(&map->name);
        zfree(&map->real_name);
        zfree(&map->pin_path);

        if (map->fd >= 0)
                zclose(map->fd);
}

void bpf_object__close(struct bpf_object *obj)
{
        size_t i;

        if (IS_ERR_OR_NULL(obj))
                return;

        usdt_manager_free(obj->usdt_man);
        obj->usdt_man = NULL;

        bpf_gen__free(obj->gen_loader);
        bpf_object__elf_finish(obj);
        bpf_object_unload(obj);
        btf__free(obj->btf);
        btf_ext__free(obj->btf_ext);

        for (i = 0; i < obj->nr_maps; i++)
                bpf_map__destroy(&obj->maps[i]);

        zfree(&obj->btf_custom_path);
        zfree(&obj->kconfig);
        zfree(&obj->externs);
        obj->nr_extern = 0;

        zfree(&obj->maps);
        obj->nr_maps = 0;

        if (obj->programs && obj->nr_programs) {
                for (i = 0; i < obj->nr_programs; i++)
                        bpf_program__exit(&obj->programs[i]);
        }
        zfree(&obj->programs);

        free(obj);
}

const char *bpf_object__name(const struct bpf_object *obj)
{
        return obj ? obj->name : libbpf_err_ptr(-EINVAL);
}

unsigned int bpf_object__kversion(const struct bpf_object *obj)
{
        return obj ? obj->kern_version : 0;
}

struct btf *bpf_object__btf(const struct bpf_object *obj)
{
        return obj ? obj->btf : NULL;
}

int bpf_object__btf_fd(const struct bpf_object *obj)
{
        return obj->btf ? btf__fd(obj->btf) : -1;
}

int bpf_object__set_kversion(struct bpf_object *obj, __u32 kern_version)
{
        if (obj->loaded)
                return libbpf_err(-EINVAL);

        obj->kern_version = kern_version;

        return 0;
}

int bpf_object__gen_loader(struct bpf_object *obj, struct gen_loader_opts *opts)
{
        struct bpf_gen *gen;

        if (!opts)
                return -EFAULT;
        if (!OPTS_VALID(opts, gen_loader_opts))
                return -EINVAL;
        gen = calloc(sizeof(*gen), 1);
        if (!gen)
                return -ENOMEM;
        gen->opts = opts;
        obj->gen_loader = gen;
        return 0;
}

static struct bpf_program *
__bpf_program__iter(const struct bpf_program *p, const struct bpf_object *obj,
                    bool forward)
{
        size_t nr_programs = obj->nr_programs;
        ssize_t idx;

        if (!nr_programs)
                return NULL;

        if (!p)
                /* Iter from the beginning */
                return forward ? &obj->programs[0] :
                        &obj->programs[nr_programs - 1];

        if (p->obj != obj) {
                pr_warn("error: program handler doesn't match object\n");
                return errno = EINVAL, NULL;
        }

        idx = (p - obj->programs) + (forward ? 1 : -1);
        if (idx >= obj->nr_programs || idx < 0)
                return NULL;
        return &obj->programs[idx];
}

struct bpf_program *
bpf_object__next_program(const struct bpf_object *obj, struct bpf_program *prev)
{
        struct bpf_program *prog = prev;

        do {
                prog = __bpf_program__iter(prog, obj, true);
        } while (prog && prog_is_subprog(obj, prog));

        return prog;
}

struct bpf_program *
bpf_object__prev_program(const struct bpf_object *obj, struct bpf_program *next)
{
        struct bpf_program *prog = next;

        do {
                prog = __bpf_program__iter(prog, obj, false);
        } while (prog && prog_is_subprog(obj, prog));

        return prog;
}

void bpf_program__set_ifindex(struct bpf_program *prog, __u32 ifindex)
{
        prog->prog_ifindex = ifindex;
}

const char *bpf_program__name(const struct bpf_program *prog)
{
        return prog->name;
}

const char *bpf_program__section_name(const struct bpf_program *prog)
{
        return prog->sec_name;
}

bool bpf_program__autoload(const struct bpf_program *prog)
{
        return prog->autoload;
}

int bpf_program__set_autoload(struct bpf_program *prog, bool autoload)
{
        if (prog->obj->loaded)
                return libbpf_err(-EINVAL);

        prog->autoload = autoload;
        return 0;
}

bool bpf_program__autoattach(const struct bpf_program *prog)
{
        return prog->autoattach;
}

void bpf_program__set_autoattach(struct bpf_program *prog, bool autoattach)
{
        prog->autoattach = autoattach;
}

const struct bpf_insn *bpf_program__insns(const struct bpf_program *prog)
{
        return prog->insns;
}

size_t bpf_program__insn_cnt(const struct bpf_program *prog)
{
        return prog->insns_cnt;
}

int bpf_program__set_insns(struct bpf_program *prog,
                           struct bpf_insn *new_insns, size_t new_insn_cnt)
{
        struct bpf_insn *insns;

        if (prog->obj->loaded)
                return -EBUSY;

        insns = libbpf_reallocarray(prog->insns, new_insn_cnt, sizeof(*insns));
        if (!insns) {
                pr_warn("prog '%s': failed to realloc prog code\n", prog->name);
                return -ENOMEM;
        }
        memcpy(insns, new_insns, new_insn_cnt * sizeof(*insns));

        prog->insns = insns;
        prog->insns_cnt = new_insn_cnt;
        return 0;
}

int bpf_program__fd(const struct bpf_program *prog)
{
        if (!prog)
                return libbpf_err(-EINVAL);

        if (prog->fd < 0)
                return libbpf_err(-ENOENT);

        return prog->fd;
}

__alias(bpf_program__type)
enum bpf_prog_type bpf_program__get_type(const struct bpf_program *prog);

enum bpf_prog_type bpf_program__type(const struct bpf_program *prog)
{
        return prog->type;
}

int bpf_program__set_type(struct bpf_program *prog, enum bpf_prog_type type)
{
        if (prog->obj->loaded)
                return libbpf_err(-EBUSY);

        prog->type = type;
        prog->sec_def = NULL;
        return 0;
}

__alias(bpf_program__expected_attach_type)
enum bpf_attach_type bpf_program__get_expected_attach_type(const struct bpf_program *prog);

enum bpf_attach_type bpf_program__expected_attach_type(const struct bpf_program *prog)
{
        return prog->expected_attach_type;
}

int bpf_program__set_expected_attach_type(struct bpf_program *prog,
                                           enum bpf_attach_type type)
{
        if (prog->obj->loaded)
                return libbpf_err(-EBUSY);

        prog->expected_attach_type = type;
        return 0;
}

__u32 bpf_program__flags(const struct bpf_program *prog)
{
        return prog->prog_flags;
}

int bpf_program__set_flags(struct bpf_program *prog, __u32 flags)
{
        if (prog->obj->loaded)
                return libbpf_err(-EBUSY);

        prog->prog_flags = flags;
        return 0;
}

__u32 bpf_program__log_level(const struct bpf_program *prog)
{
        return prog->log_level;
}

int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level)
{
        if (prog->obj->loaded)
                return libbpf_err(-EBUSY);

        prog->log_level = log_level;
        return 0;
}

const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size)
{
        *log_size = prog->log_size;
        return prog->log_buf;
}

int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log_size)
{
        if (log_size && !log_buf)
                return -EINVAL;
        if (prog->log_size > UINT_MAX)
                return -EINVAL;
        if (prog->obj->loaded)
                return -EBUSY;

        prog->log_buf = log_buf;
        prog->log_size = log_size;
        return 0;
}

#define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {                        \
        .sec = (char *)sec_pfx,                                             \
        .prog_type = BPF_PROG_TYPE_##ptype,                                 \
        .expected_attach_type = atype,                                      \
        .cookie = (long)(flags),                                            \
        .prog_prepare_load_fn = libbpf_prepare_prog_load,                   \
        __VA_ARGS__                                                         \
}

static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_ksyscall(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_usdt(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);

static const struct bpf_sec_def section_defs[] = {
        SEC_DEF("socket",               SOCKET_FILTER, 0, SEC_NONE),
        SEC_DEF("sk_reuseport/migrate", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, SEC_ATTACHABLE),
        SEC_DEF("sk_reuseport",         SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT, SEC_ATTACHABLE),
        SEC_DEF("kprobe+",              KPROBE, 0, SEC_NONE, attach_kprobe),
        SEC_DEF("uprobe+",              KPROBE, 0, SEC_NONE, attach_uprobe),
        SEC_DEF("uprobe.s+",            KPROBE, 0, SEC_SLEEPABLE, attach_uprobe),
        SEC_DEF("kretprobe+",           KPROBE, 0, SEC_NONE, attach_kprobe),
        SEC_DEF("uretprobe+",           KPROBE, 0, SEC_NONE, attach_uprobe),
        SEC_DEF("uretprobe.s+",         KPROBE, 0, SEC_SLEEPABLE, attach_uprobe),
        SEC_DEF("kprobe.multi+",        KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
        SEC_DEF("kretprobe.multi+",     KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
        SEC_DEF("ksyscall+",            KPROBE, 0, SEC_NONE, attach_ksyscall),
        SEC_DEF("kretsyscall+",         KPROBE, 0, SEC_NONE, attach_ksyscall),
        SEC_DEF("usdt+",                KPROBE, 0, SEC_NONE, attach_usdt),
        SEC_DEF("tc",                   SCHED_CLS, 0, SEC_NONE),
        SEC_DEF("classifier",           SCHED_CLS, 0, SEC_NONE),
        SEC_DEF("action",               SCHED_ACT, 0, SEC_NONE),
        SEC_DEF("tracepoint+",          TRACEPOINT, 0, SEC_NONE, attach_tp),
        SEC_DEF("tp+",                  TRACEPOINT, 0, SEC_NONE, attach_tp),
        SEC_DEF("raw_tracepoint+",      RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
        SEC_DEF("raw_tp+",              RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
        SEC_DEF("raw_tracepoint.w+",    RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
        SEC_DEF("raw_tp.w+",            RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
        SEC_DEF("tp_btf+",              TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("fentry+",              TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("fmod_ret+",            TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("fexit+",               TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("fentry.s+",            TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
        SEC_DEF("fmod_ret.s+",          TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
        SEC_DEF("fexit.s+",             TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
        SEC_DEF("freplace+",            EXT, 0, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("lsm+",                 LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
        SEC_DEF("lsm.s+",               LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
        SEC_DEF("lsm_cgroup+",          LSM, BPF_LSM_CGROUP, SEC_ATTACH_BTF),
        SEC_DEF("iter+",                TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),
        SEC_DEF("iter.s+",              TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_iter),
        SEC_DEF("syscall",              SYSCALL, 0, SEC_SLEEPABLE),
        SEC_DEF("xdp.frags/devmap",     XDP, BPF_XDP_DEVMAP, SEC_XDP_FRAGS),
        SEC_DEF("xdp/devmap",           XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),
        SEC_DEF("xdp.frags/cpumap",     XDP, BPF_XDP_CPUMAP, SEC_XDP_FRAGS),
        SEC_DEF("xdp/cpumap",           XDP, BPF_XDP_CPUMAP, SEC_ATTACHABLE),
        SEC_DEF("xdp.frags",            XDP, BPF_XDP, SEC_XDP_FRAGS),
        SEC_DEF("xdp",                  XDP, BPF_XDP, SEC_ATTACHABLE_OPT),
        SEC_DEF("perf_event",           PERF_EVENT, 0, SEC_NONE),
        SEC_DEF("lwt_in",               LWT_IN, 0, SEC_NONE),
        SEC_DEF("lwt_out",              LWT_OUT, 0, SEC_NONE),
        SEC_DEF("lwt_xmit",             LWT_XMIT, 0, SEC_NONE),
        SEC_DEF("lwt_seg6local",        LWT_SEG6LOCAL, 0, SEC_NONE),
        SEC_DEF("sockops",              SOCK_OPS, BPF_CGROUP_SOCK_OPS, SEC_ATTACHABLE_OPT),
        SEC_DEF("sk_skb/stream_parser", SK_SKB, BPF_SK_SKB_STREAM_PARSER, SEC_ATTACHABLE_OPT),
        SEC_DEF("sk_skb/stream_verdict",SK_SKB, BPF_SK_SKB_STREAM_VERDICT, SEC_ATTACHABLE_OPT),
        SEC_DEF("sk_skb",               SK_SKB, 0, SEC_NONE),
        SEC_DEF("sk_msg",               SK_MSG, BPF_SK_MSG_VERDICT, SEC_ATTACHABLE_OPT),
        SEC_DEF("lirc_mode2",           LIRC_MODE2, BPF_LIRC_MODE2, SEC_ATTACHABLE_OPT),
        SEC_DEF("flow_dissector",       FLOW_DISSECTOR, BPF_FLOW_DISSECTOR, SEC_ATTACHABLE_OPT),
        SEC_DEF("cgroup_skb/ingress",   CGROUP_SKB, BPF_CGROUP_INET_INGRESS, SEC_ATTACHABLE_OPT),
        SEC_DEF("cgroup_skb/egress",    CGROUP_SKB, BPF_CGROUP_INET_EGRESS, SEC_ATTACHABLE_OPT),
        SEC_DEF("cgroup/skb",           CGROUP_SKB, 0, SEC_NONE),
        SEC_DEF("cgroup/sock_create",   CGROUP_SOCK, BPF_CGROUP_INET_SOCK_CREATE, SEC_ATTACHABLE),
        SEC_DEF("cgroup/sock_release",  CGROUP_SOCK, BPF_CGROUP_INET_SOCK_RELEASE, SEC_ATTACHABLE),
        SEC_DEF("cgroup/sock",          CGROUP_SOCK, BPF_CGROUP_INET_SOCK_CREATE, SEC_ATTACHABLE_OPT),
        SEC_DEF("cgroup/post_bind4",    CGROUP_SOCK, BPF_CGROUP_INET4_POST_BIND, SEC_ATTACHABLE),
        SEC_DEF("cgroup/post_bind6",    CGROUP_SOCK, BPF_CGROUP_INET6_POST_BIND, SEC_ATTACHABLE),
        SEC_DEF("cgroup/bind4",         CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_BIND, SEC_ATTACHABLE),
        SEC_DEF("cgroup/bind6",         CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_BIND, SEC_ATTACHABLE),
        SEC_DEF("cgroup/connect4",      CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_CONNECT, SEC_ATTACHABLE),
        SEC_DEF("cgroup/connect6",      CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_CONNECT, SEC_ATTACHABLE),
        SEC_DEF("cgroup/sendmsg4",      CGROUP_SOCK_ADDR, BPF_CGROUP_UDP4_SENDMSG, SEC_ATTACHABLE),
        SEC_DEF("cgroup/sendmsg6",      CGROUP_SOCK_ADDR, BPF_CGROUP_UDP6_SENDMSG, SEC_ATTACHABLE),
        SEC_DEF("cgroup/recvmsg4",      CGROUP_SOCK_ADDR, BPF_CGROUP_UDP4_RECVMSG, SEC_ATTACHABLE),
        SEC_DEF("cgroup/recvmsg6",      CGROUP_SOCK_ADDR, BPF_CGROUP_UDP6_RECVMSG, SEC_ATTACHABLE),
        SEC_DEF("cgroup/getpeername4",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_GETPEERNAME, SEC_ATTACHABLE),
        SEC_DEF("cgroup/getpeername6",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_GETPEERNAME, SEC_ATTACHABLE),
        SEC_DEF("cgroup/getsockname4",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET4_GETSOCKNAME, SEC_ATTACHABLE),
        SEC_DEF("cgroup/getsockname6",  CGROUP_SOCK_ADDR, BPF_CGROUP_INET6_GETSOCKNAME, SEC_ATTACHABLE),
        SEC_DEF("cgroup/sysctl",        CGROUP_SYSCTL, BPF_CGROUP_SYSCTL, SEC_ATTACHABLE),
        SEC_DEF("cgroup/getsockopt",    CGROUP_SOCKOPT, BPF_CGROUP_GETSOCKOPT, SEC_ATTACHABLE),
        SEC_DEF("cgroup/setsockopt",    CGROUP_SOCKOPT, BPF_CGROUP_SETSOCKOPT, SEC_ATTACHABLE),
        SEC_DEF("cgroup/dev",           CGROUP_DEVICE, BPF_CGROUP_DEVICE, SEC_ATTACHABLE_OPT),
        SEC_DEF("struct_ops+",          STRUCT_OPS, 0, SEC_NONE),
        SEC_DEF("struct_ops.s+",        STRUCT_OPS, 0, SEC_SLEEPABLE),
        SEC_DEF("sk_lookup",            SK_LOOKUP, BPF_SK_LOOKUP, SEC_ATTACHABLE),
        SEC_DEF("netfilter",            NETFILTER, 0, SEC_NONE),
};

static size_t custom_sec_def_cnt;
static struct bpf_sec_def *custom_sec_defs;
static struct bpf_sec_def custom_fallback_def;
static bool has_custom_fallback_def;

static int last_custom_sec_def_handler_id;

int libbpf_register_prog_handler(const char *sec,
                                 enum bpf_prog_type prog_type,
                                 enum bpf_attach_type exp_attach_type,
                                 const struct libbpf_prog_handler_opts *opts)
{
        struct bpf_sec_def *sec_def;

        if (!OPTS_VALID(opts, libbpf_prog_handler_opts))
                return libbpf_err(-EINVAL);

        if (last_custom_sec_def_handler_id == INT_MAX) /* prevent overflow */
                return libbpf_err(-E2BIG);

        if (sec) {
                sec_def = libbpf_reallocarray(custom_sec_defs, custom_sec_def_cnt + 1,
                                              sizeof(*sec_def));
                if (!sec_def)
                        return libbpf_err(-ENOMEM);

                custom_sec_defs = sec_def;
                sec_def = &custom_sec_defs[custom_sec_def_cnt];
        } else {
                if (has_custom_fallback_def)
                        return libbpf_err(-EBUSY);

                sec_def = &custom_fallback_def;
        }

        sec_def->sec = sec ? strdup(sec) : NULL;
        if (sec && !sec_def->sec)
                return libbpf_err(-ENOMEM);

        sec_def->prog_type = prog_type;
        sec_def->expected_attach_type = exp_attach_type;
        sec_def->cookie = OPTS_GET(opts, cookie, 0);

        sec_def->prog_setup_fn = OPTS_GET(opts, prog_setup_fn, NULL);
        sec_def->prog_prepare_load_fn = OPTS_GET(opts, prog_prepare_load_fn, NULL);
        sec_def->prog_attach_fn = OPTS_GET(opts, prog_attach_fn, NULL);

        sec_def->handler_id = ++last_custom_sec_def_handler_id;

        if (sec)
                custom_sec_def_cnt++;
        else
                has_custom_fallback_def = true;

        return sec_def->handler_id;
}

int libbpf_unregister_prog_handler(int handler_id)
{
        struct bpf_sec_def *sec_defs;
        int i;

        if (handler_id <= 0)
                return libbpf_err(-EINVAL);

        if (has_custom_fallback_def && custom_fallback_def.handler_id == handler_id) {
                memset(&custom_fallback_def, 0, sizeof(custom_fallback_def));
                has_custom_fallback_def = false;
                return 0;
        }

        for (i = 0; i < custom_sec_def_cnt; i++) {
                if (custom_sec_defs[i].handler_id == handler_id)
                        break;
        }

        if (i == custom_sec_def_cnt)
                return libbpf_err(-ENOENT);

        free(custom_sec_defs[i].sec);
        for (i = i + 1; i < custom_sec_def_cnt; i++)
                custom_sec_defs[i - 1] = custom_sec_defs[i];
        custom_sec_def_cnt--;

        /* try to shrink the array, but it's ok if we couldn't */
        sec_defs = libbpf_reallocarray(custom_sec_defs, custom_sec_def_cnt, sizeof(*sec_defs));
        if (sec_defs)
                custom_sec_defs = sec_defs;

        return 0;
}

static bool sec_def_matches(const struct bpf_sec_def *sec_def, const char *sec_name)
{
        size_t len = strlen(sec_def->sec);

        /* "type/" always has to have proper SEC("type/extras") form */
        if (sec_def->sec[len - 1] == '/') {
                if (str_has_pfx(sec_name, sec_def->sec))
                        return true;
                return false;
        }

        /* "type+" means it can be either exact SEC("type") or
         * well-formed SEC("type/extras") with proper '/' separator
         */
        if (sec_def->sec[len - 1] == '+') {
                len--;
                /* not even a prefix */
                if (strncmp(sec_name, sec_def->sec, len) != 0)
                        return false;
                /* exact match or has '/' separator */
                if (sec_name[len] == '\0' || sec_name[len] == '/')
                        return true;
                return false;
        }

        return strcmp(sec_name, sec_def->sec) == 0;
}

static const struct bpf_sec_def *find_sec_def(const char *sec_name)
{
        const struct bpf_sec_def *sec_def;
        int i, n;

        n = custom_sec_def_cnt;
        for (i = 0; i < n; i++) {
                sec_def = &custom_sec_defs[i];
                if (sec_def_matches(sec_def, sec_name))
                        return sec_def;
        }

        n = ARRAY_SIZE(section_defs);
        for (i = 0; i < n; i++) {
                sec_def = &section_defs[i];
                if (sec_def_matches(sec_def, sec_name))
                        return sec_def;
        }

        if (has_custom_fallback_def)
                return &custom_fallback_def;

        return NULL;
}

#define MAX_TYPE_NAME_SIZE 32

static char *libbpf_get_type_names(bool attach_type)
{
        int i, len = ARRAY_SIZE(section_defs) * MAX_TYPE_NAME_SIZE;
        char *buf;

        buf = malloc(len);
        if (!buf)
                return NULL;

        buf[0] = '\0';
        /* Forge string buf with all available names */
        for (i = 0; i < ARRAY_SIZE(section_defs); i++) {
                const struct bpf_sec_def *sec_def = &section_defs[i];

                if (attach_type) {
                        if (sec_def->prog_prepare_load_fn != libbpf_prepare_prog_load)
                                continue;

                        if (!(sec_def->cookie & SEC_ATTACHABLE))
                                continue;
                }

                if (strlen(buf) + strlen(section_defs[i].sec) + 2 > len) {
                        free(buf);
                        return NULL;
                }
                strcat(buf, " ");
                strcat(buf, section_defs[i].sec);
        }

        return buf;
}

int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
                             enum bpf_attach_type *expected_attach_type)
{
        const struct bpf_sec_def *sec_def;
        char *type_names;

        if (!name)
                return libbpf_err(-EINVAL);

        sec_def = find_sec_def(name);
        if (sec_def) {
                *prog_type = sec_def->prog_type;
                *expected_attach_type = sec_def->expected_attach_type;
                return 0;
        }

        pr_debug("failed to guess program type from ELF section '%s'\n", name);
        type_names = libbpf_get_type_names(false);
        if (type_names != NULL) {
                pr_debug("supported section(type) names are:%s\n", type_names);
                free(type_names);
        }

        return libbpf_err(-ESRCH);
}

const char *libbpf_bpf_attach_type_str(enum bpf_attach_type t)
{
        if (t < 0 || t >= ARRAY_SIZE(attach_type_name))
                return NULL;

        return attach_type_name[t];
}

const char *libbpf_bpf_link_type_str(enum bpf_link_type t)
{
        if (t < 0 || t >= ARRAY_SIZE(link_type_name))
                return NULL;

        return link_type_name[t];
}

const char *libbpf_bpf_map_type_str(enum bpf_map_type t)
{
        if (t < 0 || t >= ARRAY_SIZE(map_type_name))
                return NULL;

        return map_type_name[t];
}

const char *libbpf_bpf_prog_type_str(enum bpf_prog_type t)
{
        if (t < 0 || t >= ARRAY_SIZE(prog_type_name))
                return NULL;

        return prog_type_name[t];
}

static struct bpf_map *find_struct_ops_map_by_offset(struct bpf_object *obj,
                                                     int sec_idx,
                                                     size_t offset)
{
        struct bpf_map *map;
        size_t i;

        for (i = 0; i < obj->nr_maps; i++) {
                map = &obj->maps[i];
                if (!bpf_map__is_struct_ops(map))
                        continue;
                if (map->sec_idx == sec_idx &&
                    map->sec_offset <= offset &&
                    offset - map->sec_offset < map->def.value_size)
                        return map;
        }

        return NULL;
}

/* Collect the reloc from ELF and populate the st_ops->progs[] */
static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
                                            Elf64_Shdr *shdr, Elf_Data *data)
{
        const struct btf_member *member;
        struct bpf_struct_ops *st_ops;
        struct bpf_program *prog;
        unsigned int shdr_idx;
        const struct btf *btf;
        struct bpf_map *map;
        unsigned int moff, insn_idx;
        const char *name;
        __u32 member_idx;
        Elf64_Sym *sym;
        Elf64_Rel *rel;
        int i, nrels;

        btf = obj->btf;
        nrels = shdr->sh_size / shdr->sh_entsize;
        for (i = 0; i < nrels; i++) {
                rel = elf_rel_by_idx(data, i);
                if (!rel) {
                        pr_warn("struct_ops reloc: failed to get %d reloc\n", i);
                        return -LIBBPF_ERRNO__FORMAT;
                }

                sym = elf_sym_by_idx(obj, ELF64_R_SYM(rel->r_info));
                if (!sym) {
                        pr_warn("struct_ops reloc: symbol %zx not found\n",
                                (size_t)ELF64_R_SYM(rel->r_info));
                        return -LIBBPF_ERRNO__FORMAT;
                }

                name = elf_sym_str(obj, sym->st_name) ?: "<?>";
                map = find_struct_ops_map_by_offset(obj, shdr->sh_info, rel->r_offset);
                if (!map) {
                        pr_warn("struct_ops reloc: cannot find map at rel->r_offset %zu\n",
                                (size_t)rel->r_offset);
                        return -EINVAL;
                }

                moff = rel->r_offset - map->sec_offset;
                shdr_idx = sym->st_shndx;
                st_ops = map->st_ops;
                pr_debug("struct_ops reloc %s: for %lld value %lld shdr_idx %u rel->r_offset %zu map->sec_offset %zu name %d (\'%s\')\n",
                         map->name,
                         (long long)(rel->r_info >> 32),
                         (long long)sym->st_value,
                         shdr_idx, (size_t)rel->r_offset,
                         map->sec_offset, sym->st_name, name);

                if (shdr_idx >= SHN_LORESERVE) {
                        pr_warn("struct_ops reloc %s: rel->r_offset %zu shdr_idx %u unsupported non-static function\n",
                                map->name, (size_t)rel->r_offset, shdr_idx);
                        return -LIBBPF_ERRNO__RELOC;
                }
                if (sym->st_value % BPF_INSN_SZ) {
                        pr_warn("struct_ops reloc %s: invalid target program offset %llu\n",
                                map->name, (unsigned long long)sym->st_value);
                        return -LIBBPF_ERRNO__FORMAT;
                }
                insn_idx = sym->st_value / BPF_INSN_SZ;

                member = find_member_by_offset(st_ops->type, moff * 8);
                if (!member) {
                        pr_warn("struct_ops reloc %s: cannot find member at moff %u\n",
                                map->name, moff);
                        return -EINVAL;
                }
                member_idx = member - btf_members(st_ops->type);
                name = btf__name_by_offset(btf, member->name_off);

                if (!resolve_func_ptr(btf, member->type, NULL)) {
                        pr_warn("struct_ops reloc %s: cannot relocate non func ptr %s\n",
                                map->name, name);
                        return -EINVAL;
                }

                prog = find_prog_by_sec_insn(obj, shdr_idx, insn_idx);
                if (!prog) {
                        pr_warn("struct_ops reloc %s: cannot find prog at shdr_idx %u to relocate func ptr %s\n",
                                map->name, shdr_idx, name);
                        return -EINVAL;
                }

                /* prevent the use of BPF prog with invalid type */
                if (prog->type != BPF_PROG_TYPE_STRUCT_OPS) {
                        pr_warn("struct_ops reloc %s: prog %s is not struct_ops BPF program\n",
                                map->name, prog->name);
                        return -EINVAL;
                }

                /* if we haven't yet processed this BPF program, record proper
                 * attach_btf_id and member_idx
                 */
                if (!prog->attach_btf_id) {
                        prog->attach_btf_id = st_ops->type_id;
                        prog->expected_attach_type = member_idx;
                }

                /* struct_ops BPF prog can be re-used between multiple
                 * .struct_ops & .struct_ops.link as long as it's the
                 * same struct_ops struct definition and the same
                 * function pointer field
                 */
                if (prog->attach_btf_id != st_ops->type_id ||
                    prog->expected_attach_type != member_idx) {
                        pr_warn("struct_ops reloc %s: cannot use prog %s in sec %s with type %u attach_btf_id %u expected_attach_type %u for func ptr %s\n",
                                map->name, prog->name, prog->sec_name, prog->type,
                                prog->attach_btf_id, prog->expected_attach_type, name);
                        return -EINVAL;
                }

                st_ops->progs[member_idx] = prog;
        }

        return 0;
}

#define BTF_TRACE_PREFIX "btf_trace_"
#define BTF_LSM_PREFIX "bpf_lsm_"
#define BTF_ITER_PREFIX "bpf_iter_"
#define BTF_MAX_NAME_SIZE 128

void btf_get_kernel_prefix_kind(enum bpf_attach_type attach_type,
                                const char **prefix, int *kind)
{
        switch (attach_type) {
        case BPF_TRACE_RAW_TP:
                *prefix = BTF_TRACE_PREFIX;
                *kind = BTF_KIND_TYPEDEF;
                break;
        case BPF_LSM_MAC:
        case BPF_LSM_CGROUP:
                *prefix = BTF_LSM_PREFIX;
                *kind = BTF_KIND_FUNC;
                break;
        case BPF_TRACE_ITER:
                *prefix = BTF_ITER_PREFIX;
                *kind = BTF_KIND_FUNC;
                break;
        default:
                *prefix = "";
                *kind = BTF_KIND_FUNC;
        }
}

static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
                                   const char *name, __u32 kind)
{
        char btf_type_name[BTF_MAX_NAME_SIZE];
        int ret;

        ret = snprintf(btf_type_name, sizeof(btf_type_name),
                       "%s%s", prefix, name);
        /* snprintf returns the number of characters written excluding the
         * terminating null. So, if >= BTF_MAX_NAME_SIZE are written, it
         * indicates truncation.
         */
        if (ret < 0 || ret >= sizeof(btf_type_name))
                return -ENAMETOOLONG;
        return btf__find_by_name_kind(btf, btf_type_name, kind);
}

static inline int find_attach_btf_id(struct btf *btf, const char *name,
                                     enum bpf_attach_type attach_type)
{
        const char *prefix;
        int kind;

        btf_get_kernel_prefix_kind(attach_type, &prefix, &kind);
        return find_btf_by_prefix_kind(btf, prefix, name, kind);
}

int libbpf_find_vmlinux_btf_id(const char *name,
                               enum bpf_attach_type attach_type)
{
        struct btf *btf;
        int err;

        btf = btf__load_vmlinux_btf();
        err = libbpf_get_error(btf);
        if (err) {
                pr_warn("vmlinux BTF is not found\n");
                return libbpf_err(err);
        }

        err = find_attach_btf_id(btf, name, attach_type);
        if (err <= 0)
                pr_warn("%s is not found in vmlinux BTF\n", name);

        btf__free(btf);
        return libbpf_err(err);
}

static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
{
        struct bpf_prog_info info;
        __u32 info_len = sizeof(info);
        struct btf *btf;
        int err;

        memset(&info, 0, info_len);
        err = bpf_prog_get_info_by_fd(attach_prog_fd, &info, &info_len);
        if (err) {
                pr_warn("failed bpf_prog_get_info_by_fd for FD %d: %d\n",
                        attach_prog_fd, err);
                return err;
        }

        err = -EINVAL;
        if (!info.btf_id) {
                pr_warn("The target program doesn't have BTF\n");
                goto out;
        }
        btf = btf__load_from_kernel_by_id(info.btf_id);
        err = libbpf_get_error(btf);
        if (err) {
                pr_warn("Failed to get BTF %d of the program: %d\n", info.btf_id, err);
                goto out;
        }
        err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
        btf__free(btf);
        if (err <= 0) {
                pr_warn("%s is not found in prog's BTF\n", name);
                goto out;
        }
out:
        return err;
}

static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
                              enum bpf_attach_type attach_type,
                              int *btf_obj_fd, int *btf_type_id)
{
        int ret, i;

        ret = find_attach_btf_id(obj->btf_vmlinux, attach_name, attach_type);
        if (ret > 0) {
                *btf_obj_fd = 0; /* vmlinux BTF */
                *btf_type_id = ret;
                return 0;
        }
        if (ret != -ENOENT)
                return ret;

        ret = load_module_btfs(obj);
        if (ret)
                return ret;

        for (i = 0; i < obj->btf_module_cnt; i++) {
                const struct module_btf *mod = &obj->btf_modules[i];

                ret = find_attach_btf_id(mod->btf, attach_name, attach_type);
                if (ret > 0) {
                        *btf_obj_fd = mod->fd;
                        *btf_type_id = ret;
                        return 0;
                }
                if (ret == -ENOENT)
                        continue;

                return ret;
        }

        return -ESRCH;
}

static int libbpf_find_attach_btf_id(struct bpf_program *prog, const char *attach_name,
                                     int *btf_obj_fd, int *btf_type_id)
{
        enum bpf_attach_type attach_type = prog->expected_attach_type;
        __u32 attach_prog_fd = prog->attach_prog_fd;
        int err = 0;

        /* BPF program's BTF ID */
        if (prog->type == BPF_PROG_TYPE_EXT || attach_prog_fd) {
                if (!attach_prog_fd) {
                        pr_warn("prog '%s': attach program FD is not set\n", prog->name);
                        return -EINVAL;
                }
                err = libbpf_find_prog_btf_id(attach_name, attach_prog_fd);
                if (err < 0) {
                        pr_warn("prog '%s': failed to find BPF program (FD %d) BTF ID for '%s': %d\n",
                                 prog->name, attach_prog_fd, attach_name, err);
                        return err;
                }
                *btf_obj_fd = 0;
                *btf_type_id = err;
                return 0;
        }

        /* kernel/module BTF ID */
        if (prog->obj->gen_loader) {
                bpf_gen__record_attach_target(prog->obj->gen_loader, attach_name, attach_type);
                *btf_obj_fd = 0;
                *btf_type_id = 1;
        } else {
                err = find_kernel_btf_id(prog->obj, attach_name, attach_type, btf_obj_fd, btf_type_id);
        }
        if (err) {
                pr_warn("prog '%s': failed to find kernel BTF type ID of '%s': %d\n",
                        prog->name, attach_name, err);
                return err;
        }
        return 0;
}

int libbpf_attach_type_by_name(const char *name,
                               enum bpf_attach_type *attach_type)
{
        char *type_names;
        const struct bpf_sec_def *sec_def;

        if (!name)
                return libbpf_err(-EINVAL);

        sec_def = find_sec_def(name);
        if (!sec_def) {
                pr_debug("failed to guess attach type based on ELF section name '%s'\n", name);
                type_names = libbpf_get_type_names(true);
                if (type_names != NULL) {
                        pr_debug("attachable section(type) names are:%s\n", type_names);
                        free(type_names);
                }

                return libbpf_err(-EINVAL);
        }

        if (sec_def->prog_prepare_load_fn != libbpf_prepare_prog_load)
                return libbpf_err(-EINVAL);
        if (!(sec_def->cookie & SEC_ATTACHABLE))
                return libbpf_err(-EINVAL);

        *attach_type = sec_def->expected_attach_type;
        return 0;
}

int bpf_map__fd(const struct bpf_map *map)
{
        return map ? map->fd : libbpf_err(-EINVAL);
}

static bool map_uses_real_name(const struct bpf_map *map)
{
        /* Since libbpf started to support custom .data.* and .rodata.* maps,
         * their user-visible name differs from kernel-visible name. Users see
         * such map's corresponding ELF section name as a map name.
         * This check distinguishes .data/.rodata from .data.* and .rodata.*
         * maps to know which name has to be returned to the user.
         */
        if (map->libbpf_type == LIBBPF_MAP_DATA && strcmp(map->real_name, DATA_SEC) != 0)
                return true;
        if (map->libbpf_type == LIBBPF_MAP_RODATA && strcmp(map->real_name, RODATA_SEC) != 0)
                return true;
        return false;
}

const char *bpf_map__name(const struct bpf_map *map)
{
        if (!map)
                return NULL;

        if (map_uses_real_name(map))
                return map->real_name;

        return map->name;
}

enum bpf_map_type bpf_map__type(const struct bpf_map *map)
{
        return map->def.type;
}

int bpf_map__set_type(struct bpf_map *map, enum bpf_map_type type)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->def.type = type;
        return 0;
}

__u32 bpf_map__map_flags(const struct bpf_map *map)
{
        return map->def.map_flags;
}

int bpf_map__set_map_flags(struct bpf_map *map, __u32 flags)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->def.map_flags = flags;
        return 0;
}

__u64 bpf_map__map_extra(const struct bpf_map *map)
{
        return map->map_extra;
}

int bpf_map__set_map_extra(struct bpf_map *map, __u64 map_extra)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->map_extra = map_extra;
        return 0;
}

__u32 bpf_map__numa_node(const struct bpf_map *map)
{
        return map->numa_node;
}

int bpf_map__set_numa_node(struct bpf_map *map, __u32 numa_node)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->numa_node = numa_node;
        return 0;
}

__u32 bpf_map__key_size(const struct bpf_map *map)
{
        return map->def.key_size;
}

int bpf_map__set_key_size(struct bpf_map *map, __u32 size)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->def.key_size = size;
        return 0;
}

__u32 bpf_map__value_size(const struct bpf_map *map)
{
        return map->def.value_size;
}

int bpf_map__set_value_size(struct bpf_map *map, __u32 size)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->def.value_size = size;
        return 0;
}

__u32 bpf_map__btf_key_type_id(const struct bpf_map *map)
{
        return map ? map->btf_key_type_id : 0;
}

__u32 bpf_map__btf_value_type_id(const struct bpf_map *map)
{
        return map ? map->btf_value_type_id : 0;
}

int bpf_map__set_initial_value(struct bpf_map *map,
                               const void *data, size_t size)
{
        if (!map->mmaped || map->libbpf_type == LIBBPF_MAP_KCONFIG ||
            size != map->def.value_size || map->fd >= 0)
                return libbpf_err(-EINVAL);

        memcpy(map->mmaped, data, size);
        return 0;
}

const void *bpf_map__initial_value(struct bpf_map *map, size_t *psize)
{
        if (!map->mmaped)
                return NULL;
        *psize = map->def.value_size;
        return map->mmaped;
}

bool bpf_map__is_internal(const struct bpf_map *map)
{
        return map->libbpf_type != LIBBPF_MAP_UNSPEC;
}

__u32 bpf_map__ifindex(const struct bpf_map *map)
{
        return map->map_ifindex;
}

int bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex)
{
        if (map->fd >= 0)
                return libbpf_err(-EBUSY);
        map->map_ifindex = ifindex;
        return 0;
}

int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd)
{
        if (!bpf_map_type__is_map_in_map(map->def.type)) {
                pr_warn("error: unsupported map type\n");
                return libbpf_err(-EINVAL);
        }
        if (map->inner_map_fd != -1) {
                pr_warn("error: inner_map_fd already specified\n");
                return libbpf_err(-EINVAL);
        }
        if (map->inner_map) {
                bpf_map__destroy(map->inner_map);
                zfree(&map->inner_map);
        }
        map->inner_map_fd = fd;
        return 0;
}

static struct bpf_map *
__bpf_map__iter(const struct bpf_map *m, const struct bpf_object *obj, int i)
{
        ssize_t idx;
        struct bpf_map *s, *e;

        if (!obj || !obj->maps)
                return errno = EINVAL, NULL;

        s = obj->maps;
        e = obj->maps + obj->nr_maps;

        if ((m < s) || (m >= e)) {
                pr_warn("error in %s: map handler doesn't belong to object\n",
                         __func__);
                return errno = EINVAL, NULL;
        }

        idx = (m - obj->maps) + i;
        if (idx >= obj->nr_maps || idx < 0)
                return NULL;
        return &obj->maps[idx];
}

struct bpf_map *
bpf_object__next_map(const struct bpf_object *obj, const struct bpf_map *prev)
{
        if (prev == NULL)
                return obj->maps;

        return __bpf_map__iter(prev, obj, 1);
}

struct bpf_map *
bpf_object__prev_map(const struct bpf_object *obj, const struct bpf_map *next)
{
        if (next == NULL) {
                if (!obj->nr_maps)
                        return NULL;
                return obj->maps + obj->nr_maps - 1;
        }

        return __bpf_map__iter(next, obj, -1);
}

struct bpf_map *
bpf_object__find_map_by_name(const struct bpf_object *obj, const char *name)
{
        struct bpf_map *pos;

        bpf_object__for_each_map(pos, obj) {
                /* if it's a special internal map name (which always starts
                 * with dot) then check if that special name matches the
                 * real map name (ELF section name)
                 */
                if (name[0] == '.') {
                        if (pos->real_name && strcmp(pos->real_name, name) == 0)
                                return pos;
                        continue;
                }
                /* otherwise map name has to be an exact match */
                if (map_uses_real_name(pos)) {
                        if (strcmp(pos->real_name, name) == 0)
                                return pos;
                        continue;
                }
                if (strcmp(pos->name, name) == 0)
                        return pos;
        }
        return errno = ENOENT, NULL;
}

int
bpf_object__find_map_fd_by_name(const struct bpf_object *obj, const char *name)
{
        return bpf_map__fd(bpf_object__find_map_by_name(obj, name));
}

static int validate_map_op(const struct bpf_map *map, size_t key_sz,
                           size_t value_sz, bool check_value_sz)
{
        if (map->fd <= 0)
                return -ENOENT;

        if (map->def.key_size != key_sz) {
                pr_warn("map '%s': unexpected key size %zu provided, expected %u\n",
                        map->name, key_sz, map->def.key_size);
                return -EINVAL;
        }

        if (!check_value_sz)
                return 0;

        switch (map->def.type) {
        case BPF_MAP_TYPE_PERCPU_ARRAY:
        case BPF_MAP_TYPE_PERCPU_HASH:
        case BPF_MAP_TYPE_LRU_PERCPU_HASH:
        case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE: {
                int num_cpu = libbpf_num_possible_cpus();
                size_t elem_sz = roundup(map->def.value_size, 8);

                if (value_sz != num_cpu * elem_sz) {
                        pr_warn("map '%s': unexpected value size %zu provided for per-CPU map, expected %d * %zu = %zd\n",
                                map->name, value_sz, num_cpu, elem_sz, num_cpu * elem_sz);
                        return -EINVAL;
                }
                break;
        }
        default:
                if (map->def.value_size != value_sz) {
                        pr_warn("map '%s': unexpected value size %zu provided, expected %u\n",
                                map->name, value_sz, map->def.value_size);
                        return -EINVAL;
                }
                break;
        }
        return 0;
}

int bpf_map__lookup_elem(const struct bpf_map *map,
                         const void *key, size_t key_sz,
                         void *value, size_t value_sz, __u64 flags)
{
        int err;

        err = validate_map_op(map, key_sz, value_sz, true);
        if (err)
                return libbpf_err(err);

        return bpf_map_lookup_elem_flags(map->fd, key, value, flags);
}

int bpf_map__update_elem(const struct bpf_map *map,
                         const void *key, size_t key_sz,
                         const void *value, size_t value_sz, __u64 flags)
{
        int err;

        err = validate_map_op(map, key_sz, value_sz, true);
        if (err)
                return libbpf_err(err);

        return bpf_map_update_elem(map->fd, key, value, flags);
}

int bpf_map__delete_elem(const struct bpf_map *map,
                         const void *key, size_t key_sz, __u64 flags)
{
        int err;

        err = validate_map_op(map, key_sz, 0, false /* check_value_sz */);
        if (err)
                return libbpf_err(err);

        return bpf_map_delete_elem_flags(map->fd, key, flags);
}

int bpf_map__lookup_and_delete_elem(const struct bpf_map *map,
                                    const void *key, size_t key_sz,
                                    void *value, size_t value_sz, __u64 flags)
{
        int err;

        err = validate_map_op(map, key_sz, value_sz, true);
        if (err)
                return libbpf_err(err);

        return bpf_map_lookup_and_delete_elem_flags(map->fd, key, value, flags);
}

int bpf_map__get_next_key(const struct bpf_map *map,
                          const void *cur_key, void *next_key, size_t key_sz)
{
        int err;

        err = validate_map_op(map, key_sz, 0, false /* check_value_sz */);
        if (err)
                return libbpf_err(err);

        return bpf_map_get_next_key(map->fd, cur_key, next_key);
}

long libbpf_get_error(const void *ptr)
{
        if (!IS_ERR_OR_NULL(ptr))
                return 0;

        if (IS_ERR(ptr))
                errno = -PTR_ERR(ptr);

        /* If ptr == NULL, then errno should be already set by the failing
         * API, because libbpf never returns NULL on success and it now always
         * sets errno on error. So no extra errno handling for ptr == NULL
         * case.
         */
        return -errno;
}

/* Replace link's underlying BPF program with the new one */
int bpf_link__update_program(struct bpf_link *link, struct bpf_program *prog)
{
        int ret;

        ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog), NULL);
        return libbpf_err_errno(ret);
}

/* Release "ownership" of underlying BPF resource (typically, BPF program
 * attached to some BPF hook, e.g., tracepoint, kprobe, etc). Disconnected
 * link, when destructed through bpf_link__destroy() call won't attempt to
 * detach/unregisted that BPF resource. This is useful in situations where,
 * say, attached BPF program has to outlive userspace program that attached it
 * in the system. Depending on type of BPF program, though, there might be
 * additional steps (like pinning BPF program in BPF FS) necessary to ensure
 * exit of userspace program doesn't trigger automatic detachment and clean up
 * inside the kernel.
 */
void bpf_link__disconnect(struct bpf_link *link)
{
        link->disconnected = true;
}

int bpf_link__destroy(struct bpf_link *link)
{
        int err = 0;

        if (IS_ERR_OR_NULL(link))
                return 0;

        if (!link->disconnected && link->detach)
                err = link->detach(link);
        if (link->pin_path)
                free(link->pin_path);
        if (link->dealloc)
                link->dealloc(link);
        else
                free(link);

        return libbpf_err(err);
}

int bpf_link__fd(const struct bpf_link *link)
{
        return link->fd;
}

const char *bpf_link__pin_path(const struct bpf_link *link)
{
        return link->pin_path;
}

static int bpf_link__detach_fd(struct bpf_link *link)
{
        return libbpf_err_errno(close(link->fd));
}

struct bpf_link *bpf_link__open(const char *path)
{
        struct bpf_link *link;
        int fd;

        fd = bpf_obj_get(path);
        if (fd < 0) {
                fd = -errno;
                pr_warn("failed to open link at %s: %d\n", path, fd);
                return libbpf_err_ptr(fd);
        }

        link = calloc(1, sizeof(*link));
        if (!link) {
                close(fd);
                return libbpf_err_ptr(-ENOMEM);
        }
        link->detach = &bpf_link__detach_fd;
        link->fd = fd;

        link->pin_path = strdup(path);
        if (!link->pin_path) {
                bpf_link__destroy(link);
                return libbpf_err_ptr(-ENOMEM);
        }

        return link;
}

int bpf_link__detach(struct bpf_link *link)
{
        return bpf_link_detach(link->fd) ? -errno : 0;
}

int bpf_link__pin(struct bpf_link *link, const char *path)
{
        int err;

        if (link->pin_path)
                return libbpf_err(-EBUSY);
        err = make_parent_dir(path);
        if (err)
                return libbpf_err(err);
        err = check_path(path);
        if (err)
                return libbpf_err(err);

        link->pin_path = strdup(path);
        if (!link->pin_path)
                return libbpf_err(-ENOMEM);

        if (bpf_obj_pin(link->fd, link->pin_path)) {
                err = -errno;
                zfree(&link->pin_path);
                return libbpf_err(err);
        }

        pr_debug("link fd=%d: pinned at %s\n", link->fd, link->pin_path);
        return 0;
}

int bpf_link__unpin(struct bpf_link *link)
{
        int err;

        if (!link->pin_path)
                return libbpf_err(-EINVAL);

        err = unlink(link->pin_path);
        if (err != 0)
                return -errno;

        pr_debug("link fd=%d: unpinned from %s\n", link->fd, link->pin_path);
        zfree(&link->pin_path);
        return 0;
}

struct bpf_link_perf {
        struct bpf_link link;
        int perf_event_fd;
        /* legacy kprobe support: keep track of probe identifier and type */
        char *legacy_probe_name;
        bool legacy_is_kprobe;
        bool legacy_is_retprobe;
};

static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe);
static int remove_uprobe_event_legacy(const char *probe_name, bool retprobe);

static int bpf_link_perf_detach(struct bpf_link *link)
{
        struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
        int err = 0;

        if (ioctl(perf_link->perf_event_fd, PERF_EVENT_IOC_DISABLE, 0) < 0)
                err = -errno;

        if (perf_link->perf_event_fd != link->fd)
                close(perf_link->perf_event_fd);
        close(link->fd);

        /* legacy uprobe/kprobe needs to be removed after perf event fd closure */
        if (perf_link->legacy_probe_name) {
                if (perf_link->legacy_is_kprobe) {
                        err = remove_kprobe_event_legacy(perf_link->legacy_probe_name,
                                                         perf_link->legacy_is_retprobe);
                } else {
                        err = remove_uprobe_event_legacy(perf_link->legacy_probe_name,
                                                         perf_link->legacy_is_retprobe);
                }
        }

        return err;
}

static void bpf_link_perf_dealloc(struct bpf_link *link)
{
        struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);

        free(perf_link->legacy_probe_name);
        free(perf_link);
}

struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *prog, int pfd,
                                                     const struct bpf_perf_event_opts *opts)
{
        char errmsg[STRERR_BUFSIZE];
        struct bpf_link_perf *link;
        int prog_fd, link_fd = -1, err;
        bool force_ioctl_attach;

        if (!OPTS_VALID(opts, bpf_perf_event_opts))
                return libbpf_err_ptr(-EINVAL);

        if (pfd < 0) {
                pr_warn("prog '%s': invalid perf event FD %d\n",
                        prog->name, pfd);
                return libbpf_err_ptr(-EINVAL);
        }
        prog_fd = bpf_program__fd(prog);
        if (prog_fd < 0) {
                pr_warn("prog '%s': can't attach BPF program w/o FD (did you load it?)\n",
                        prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        link = calloc(1, sizeof(*link));
        if (!link)
                return libbpf_err_ptr(-ENOMEM);
        link->link.detach = &bpf_link_perf_detach;
        link->link.dealloc = &bpf_link_perf_dealloc;
        link->perf_event_fd = pfd;

        force_ioctl_attach = OPTS_GET(opts, force_ioctl_attach, false);
        if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !force_ioctl_attach) {
                DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
                        .perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));

                link_fd = bpf_link_create(prog_fd, pfd, BPF_PERF_EVENT, &link_opts);
                if (link_fd < 0) {
                        err = -errno;
                        pr_warn("prog '%s': failed to create BPF link for perf_event FD %d: %d (%s)\n",
                                prog->name, pfd,
                                err, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                        goto err_out;
                }
                link->link.fd = link_fd;
        } else {
                if (OPTS_GET(opts, bpf_cookie, 0)) {
                        pr_warn("prog '%s': user context value is not supported\n", prog->name);
                        err = -EOPNOTSUPP;
                        goto err_out;
                }

                if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) {
                        err = -errno;
                        pr_warn("prog '%s': failed to attach to perf_event FD %d: %s\n",
                                prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                        if (err == -EPROTO)
                                pr_warn("prog '%s': try add PERF_SAMPLE_CALLCHAIN to or remove exclude_callchain_[kernel|user] from pfd %d\n",
                                        prog->name, pfd);
                        goto err_out;
                }
                link->link.fd = pfd;
        }
        if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
                err = -errno;
                pr_warn("prog '%s': failed to enable perf_event FD %d: %s\n",
                        prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_out;
        }

        return &link->link;
err_out:
        if (link_fd >= 0)
                close(link_fd);
        free(link);
        return libbpf_err_ptr(err);
}

struct bpf_link *bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd)
{
        return bpf_program__attach_perf_event_opts(prog, pfd, NULL);
}

/*
 * this function is expected to parse integer in the range of [0, 2^31-1] from
 * given file using scanf format string fmt. If actual parsed value is
 * negative, the result might be indistinguishable from error
 */
static int parse_uint_from_file(const char *file, const char *fmt)
{
        char buf[STRERR_BUFSIZE];
        int err, ret;
        FILE *f;

        f = fopen(file, "r");
        if (!f) {
                err = -errno;
                pr_debug("failed to open '%s': %s\n", file,
                         libbpf_strerror_r(err, buf, sizeof(buf)));
                return err;
        }
        err = fscanf(f, fmt, &ret);
        if (err != 1) {
                err = err == EOF ? -EIO : -errno;
                pr_debug("failed to parse '%s': %s\n", file,
                        libbpf_strerror_r(err, buf, sizeof(buf)));
                fclose(f);
                return err;
        }
        fclose(f);
        return ret;
}

static int determine_kprobe_perf_type(void)
{
        const char *file = "/sys/bus/event_source/devices/kprobe/type";

        return parse_uint_from_file(file, "%d\n");
}

static int determine_uprobe_perf_type(void)
{
        const char *file = "/sys/bus/event_source/devices/uprobe/type";

        return parse_uint_from_file(file, "%d\n");
}

static int determine_kprobe_retprobe_bit(void)
{
        const char *file = "/sys/bus/event_source/devices/kprobe/format/retprobe";

        return parse_uint_from_file(file, "config:%d\n");
}

static int determine_uprobe_retprobe_bit(void)
{
        const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";

        return parse_uint_from_file(file, "config:%d\n");
}

#define PERF_UPROBE_REF_CTR_OFFSET_BITS 32
#define PERF_UPROBE_REF_CTR_OFFSET_SHIFT 32

static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
                                 uint64_t offset, int pid, size_t ref_ctr_off)
{
        const size_t attr_sz = sizeof(struct perf_event_attr);
        struct perf_event_attr attr;
        char errmsg[STRERR_BUFSIZE];
        int type, pfd;

        if ((__u64)ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
                return -EINVAL;

        memset(&attr, 0, attr_sz);

        type = uprobe ? determine_uprobe_perf_type()
                      : determine_kprobe_perf_type();
        if (type < 0) {
                pr_warn("failed to determine %s perf type: %s\n",
                        uprobe ? "uprobe" : "kprobe",
                        libbpf_strerror_r(type, errmsg, sizeof(errmsg)));
                return type;
        }
        if (retprobe) {
                int bit = uprobe ? determine_uprobe_retprobe_bit()
                                 : determine_kprobe_retprobe_bit();

                if (bit < 0) {
                        pr_warn("failed to determine %s retprobe bit: %s\n",
                                uprobe ? "uprobe" : "kprobe",
                                libbpf_strerror_r(bit, errmsg, sizeof(errmsg)));
                        return bit;
                }
                attr.config |= 1 << bit;
        }
        attr.size = attr_sz;
        attr.type = type;
        attr.config |= (__u64)ref_ctr_off << PERF_UPROBE_REF_CTR_OFFSET_SHIFT;
        attr.config1 = ptr_to_u64(name); /* kprobe_func or uprobe_path */
        attr.config2 = offset;           /* kprobe_addr or probe_offset */

        /* pid filter is meaningful only for uprobes */
        pfd = syscall(__NR_perf_event_open, &attr,
                      pid < 0 ? -1 : pid /* pid */,
                      pid == -1 ? 0 : -1 /* cpu */,
                      -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
        return pfd >= 0 ? pfd : -errno;
}

static int append_to_file(const char *file, const char *fmt, ...)
{
        int fd, n, err = 0;
        va_list ap;
        char buf[1024];

        va_start(ap, fmt);
        n = vsnprintf(buf, sizeof(buf), fmt, ap);
        va_end(ap);

        if (n < 0 || n >= sizeof(buf))
                return -EINVAL;

        fd = open(file, O_WRONLY | O_APPEND | O_CLOEXEC, 0);
        if (fd < 0)
                return -errno;

        if (write(fd, buf, n) < 0)
                err = -errno;

        close(fd);
        return err;
}

#define DEBUGFS "/sys/kernel/debug/tracing"
#define TRACEFS "/sys/kernel/tracing"

static bool use_debugfs(void)
{
        static int has_debugfs = -1;

        if (has_debugfs < 0)
                has_debugfs = faccessat(AT_FDCWD, DEBUGFS, F_OK, AT_EACCESS) == 0;

        return has_debugfs == 1;
}

static const char *tracefs_path(void)
{
        return use_debugfs() ? DEBUGFS : TRACEFS;
}

static const char *tracefs_kprobe_events(void)
{
        return use_debugfs() ? DEBUGFS"/kprobe_events" : TRACEFS"/kprobe_events";
}

static const char *tracefs_uprobe_events(void)
{
        return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
}

static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
                                         const char *kfunc_name, size_t offset)
{
        static int index = 0;
        int i;

        snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
                 __sync_fetch_and_add(&index, 1));

        /* sanitize binary_path in the probe name */
        for (i = 0; buf[i]; i++) {
                if (!isalnum(buf[i]))
                        buf[i] = '_';
        }
}

static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,
                                   const char *kfunc_name, size_t offset)
{
        return append_to_file(tracefs_kprobe_events(), "%c:%s/%s %s+0x%zx",
                              retprobe ? 'r' : 'p',
                              retprobe ? "kretprobes" : "kprobes",
                              probe_name, kfunc_name, offset);
}

static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe)
{
        return append_to_file(tracefs_kprobe_events(), "-:%s/%s",
                              retprobe ? "kretprobes" : "kprobes", probe_name);
}

static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retprobe)
{
        char file[256];

        snprintf(file, sizeof(file), "%s/events/%s/%s/id",
                 tracefs_path(), retprobe ? "kretprobes" : "kprobes", probe_name);

        return parse_uint_from_file(file, "%d\n");
}

static int perf_event_kprobe_open_legacy(const char *probe_name, bool retprobe,
                                         const char *kfunc_name, size_t offset, int pid)
{
        const size_t attr_sz = sizeof(struct perf_event_attr);
        struct perf_event_attr attr;
        char errmsg[STRERR_BUFSIZE];
        int type, pfd, err;

        err = add_kprobe_event_legacy(probe_name, retprobe, kfunc_name, offset);
        if (err < 0) {
                pr_warn("failed to add legacy kprobe event for '%s+0x%zx': %s\n",
                        kfunc_name, offset,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                return err;
        }
        type = determine_kprobe_perf_type_legacy(probe_name, retprobe);
        if (type < 0) {
                err = type;
                pr_warn("failed to determine legacy kprobe event id for '%s+0x%zx': %s\n",
                        kfunc_name, offset,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_clean_legacy;
        }

        memset(&attr, 0, attr_sz);
        attr.size = attr_sz;
        attr.config = type;
        attr.type = PERF_TYPE_TRACEPOINT;

        pfd = syscall(__NR_perf_event_open, &attr,
                      pid < 0 ? -1 : pid, /* pid */
                      pid == -1 ? 0 : -1, /* cpu */
                      -1 /* group_fd */,  PERF_FLAG_FD_CLOEXEC);
        if (pfd < 0) {
                err = -errno;
                pr_warn("legacy kprobe perf_event_open() failed: %s\n",
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_clean_legacy;
        }
        return pfd;

err_clean_legacy:
        /* Clear the newly added legacy kprobe_event */
        remove_kprobe_event_legacy(probe_name, retprobe);
        return err;
}

static const char *arch_specific_syscall_pfx(void)
{
#if defined(__x86_64__)
        return "x64";
#elif defined(__i386__)
        return "ia32";
#elif defined(__s390x__)
        return "s390x";
#elif defined(__s390__)
        return "s390";
#elif defined(__arm__)
        return "arm";
#elif defined(__aarch64__)
        return "arm64";
#elif defined(__mips__)
        return "mips";
#elif defined(__riscv)
        return "riscv";
#elif defined(__powerpc__)
        return "powerpc";
#elif defined(__powerpc64__)
        return "powerpc64";
#else
        return NULL;
#endif
}

static int probe_kern_syscall_wrapper(void)
{
        char syscall_name[64];
        const char *ksys_pfx;

        ksys_pfx = arch_specific_syscall_pfx();
        if (!ksys_pfx)
                return 0;

        snprintf(syscall_name, sizeof(syscall_name), "__%s_sys_bpf", ksys_pfx);

        if (determine_kprobe_perf_type() >= 0) {
                int pfd;

                pfd = perf_event_open_probe(false, false, syscall_name, 0, getpid(), 0);
                if (pfd >= 0)
                        close(pfd);

                return pfd >= 0 ? 1 : 0;
        } else { /* legacy mode */
                char probe_name[128];

                gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
                if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
                        return 0;

                (void)remove_kprobe_event_legacy(probe_name, false);
                return 1;
        }
}

struct bpf_link *
bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
                                const char *func_name,
                                const struct bpf_kprobe_opts *opts)
{
        DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
        enum probe_attach_mode attach_mode;
        char errmsg[STRERR_BUFSIZE];
        char *legacy_probe = NULL;
        struct bpf_link *link;
        size_t offset;
        bool retprobe, legacy;
        int pfd, err;

        if (!OPTS_VALID(opts, bpf_kprobe_opts))
                return libbpf_err_ptr(-EINVAL);

        attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
        retprobe = OPTS_GET(opts, retprobe, false);
        offset = OPTS_GET(opts, offset, 0);
        pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);

        legacy = determine_kprobe_perf_type() < 0;
        switch (attach_mode) {
        case PROBE_ATTACH_MODE_LEGACY:
                legacy = true;
                pe_opts.force_ioctl_attach = true;
                break;
        case PROBE_ATTACH_MODE_PERF:
                if (legacy)
                        return libbpf_err_ptr(-ENOTSUP);
                pe_opts.force_ioctl_attach = true;
                break;
        case PROBE_ATTACH_MODE_LINK:
                if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
                        return libbpf_err_ptr(-ENOTSUP);
                break;
        case PROBE_ATTACH_MODE_DEFAULT:
                break;
        default:
                return libbpf_err_ptr(-EINVAL);
        }

        if (!legacy) {
                pfd = perf_event_open_probe(false /* uprobe */, retprobe,
                                            func_name, offset,
                                            -1 /* pid */, 0 /* ref_ctr_off */);
        } else {
                char probe_name[256];

                gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
                                             func_name, offset);

                legacy_probe = strdup(probe_name);
                if (!legacy_probe)
                        return libbpf_err_ptr(-ENOMEM);

                pfd = perf_event_kprobe_open_legacy(legacy_probe, retprobe, func_name,
                                                    offset, -1 /* pid */);
        }
        if (pfd < 0) {
                err = -errno;
                pr_warn("prog '%s': failed to create %s '%s+0x%zx' perf event: %s\n",
                        prog->name, retprobe ? "kretprobe" : "kprobe",
                        func_name, offset,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_out;
        }
        link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
        err = libbpf_get_error(link);
        if (err) {
                close(pfd);
                pr_warn("prog '%s': failed to attach to %s '%s+0x%zx': %s\n",
                        prog->name, retprobe ? "kretprobe" : "kprobe",
                        func_name, offset,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_clean_legacy;
        }
        if (legacy) {
                struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);

                perf_link->legacy_probe_name = legacy_probe;
                perf_link->legacy_is_kprobe = true;
                perf_link->legacy_is_retprobe = retprobe;
        }

        return link;

err_clean_legacy:
        if (legacy)
                remove_kprobe_event_legacy(legacy_probe, retprobe);
err_out:
        free(legacy_probe);
        return libbpf_err_ptr(err);
}

struct bpf_link *bpf_program__attach_kprobe(const struct bpf_program *prog,
                                            bool retprobe,
                                            const char *func_name)
{
        DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts,
                .retprobe = retprobe,
        );

        return bpf_program__attach_kprobe_opts(prog, func_name, &opts);
}

struct bpf_link *bpf_program__attach_ksyscall(const struct bpf_program *prog,
                                              const char *syscall_name,
                                              const struct bpf_ksyscall_opts *opts)
{
        LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts);
        char func_name[128];

        if (!OPTS_VALID(opts, bpf_ksyscall_opts))
                return libbpf_err_ptr(-EINVAL);

        if (kernel_supports(prog->obj, FEAT_SYSCALL_WRAPPER)) {
                /* arch_specific_syscall_pfx() should never return NULL here
                 * because it is guarded by kernel_supports(). However, since
                 * compiler does not know that we have an explicit conditional
                 * as well.
                 */
                snprintf(func_name, sizeof(func_name), "__%s_sys_%s",
                         arch_specific_syscall_pfx() ? : "", syscall_name);
        } else {
                snprintf(func_name, sizeof(func_name), "__se_sys_%s", syscall_name);
        }

        kprobe_opts.retprobe = OPTS_GET(opts, retprobe, false);
        kprobe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);

        return bpf_program__attach_kprobe_opts(prog, func_name, &kprobe_opts);
}

/* Adapted from perf/util/string.c */
static bool glob_match(const char *str, const char *pat)
{
        while (*str && *pat && *pat != '*') {
                if (*pat == '?') {      /* Matches any single character */
                        str++;
                        pat++;
                        continue;
                }
                if (*str != *pat)
                        return false;
                str++;
                pat++;
        }
        /* Check wild card */
        if (*pat == '*') {
                while (*pat == '*')
                        pat++;
                if (!*pat) /* Tail wild card matches all */
                        return true;
                while (*str)
                        if (glob_match(str++, pat))
                                return true;
        }
        return !*str && !*pat;
}

struct kprobe_multi_resolve {
        const char *pattern;
        unsigned long *addrs;
        size_t cap;
        size_t cnt;
};

static int
resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
                        const char *sym_name, void *ctx)
{
        struct kprobe_multi_resolve *res = ctx;
        int err;

        if (!glob_match(sym_name, res->pattern))
                return 0;

        err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
                                res->cnt + 1);
        if (err)
                return err;

        res->addrs[res->cnt++] = (unsigned long) sym_addr;
        return 0;
}

struct bpf_link *
bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
                                      const char *pattern,
                                      const struct bpf_kprobe_multi_opts *opts)
{
        LIBBPF_OPTS(bpf_link_create_opts, lopts);
        struct kprobe_multi_resolve res = {
                .pattern = pattern,
        };
        struct bpf_link *link = NULL;
        char errmsg[STRERR_BUFSIZE];
        const unsigned long *addrs;
        int err, link_fd, prog_fd;
        const __u64 *cookies;
        const char **syms;
        bool retprobe;
        size_t cnt;

        if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
                return libbpf_err_ptr(-EINVAL);

        syms    = OPTS_GET(opts, syms, false);
        addrs   = OPTS_GET(opts, addrs, false);
        cnt     = OPTS_GET(opts, cnt, false);
        cookies = OPTS_GET(opts, cookies, false);

        if (!pattern && !addrs && !syms)
                return libbpf_err_ptr(-EINVAL);
        if (pattern && (addrs || syms || cookies || cnt))
                return libbpf_err_ptr(-EINVAL);
        if (!pattern && !cnt)
                return libbpf_err_ptr(-EINVAL);
        if (addrs && syms)
                return libbpf_err_ptr(-EINVAL);

        if (pattern) {
                err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
                if (err)
                        goto error;
                if (!res.cnt) {
                        err = -ENOENT;
                        goto error;
                }
                addrs = res.addrs;
                cnt = res.cnt;
        }

        retprobe = OPTS_GET(opts, retprobe, false);

        lopts.kprobe_multi.syms = syms;
        lopts.kprobe_multi.addrs = addrs;
        lopts.kprobe_multi.cookies = cookies;
        lopts.kprobe_multi.cnt = cnt;
        lopts.kprobe_multi.flags = retprobe ? BPF_F_KPROBE_MULTI_RETURN : 0;

        link = calloc(1, sizeof(*link));
        if (!link) {
                err = -ENOMEM;
                goto error;
        }
        link->detach = &bpf_link__detach_fd;

        prog_fd = bpf_program__fd(prog);
        link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_KPROBE_MULTI, &lopts);
        if (link_fd < 0) {
                err = -errno;
                pr_warn("prog '%s': failed to attach: %s\n",
                        prog->name, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto error;
        }
        link->fd = link_fd;
        free(res.addrs);
        return link;

error:
        free(link);
        free(res.addrs);
        return libbpf_err_ptr(err);
}

static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts);
        unsigned long offset = 0;
        const char *func_name;
        char *func;
        int n;

        *link = NULL;

        /* no auto-attach for SEC("kprobe") and SEC("kretprobe") */
        if (strcmp(prog->sec_name, "kprobe") == 0 || strcmp(prog->sec_name, "kretprobe") == 0)
                return 0;

        opts.retprobe = str_has_pfx(prog->sec_name, "kretprobe/");
        if (opts.retprobe)
                func_name = prog->sec_name + sizeof("kretprobe/") - 1;
        else
                func_name = prog->sec_name + sizeof("kprobe/") - 1;

        n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);
        if (n < 1) {
                pr_warn("kprobe name is invalid: %s\n", func_name);
                return -EINVAL;
        }
        if (opts.retprobe && offset != 0) {
                free(func);
                pr_warn("kretprobes do not support offset specification\n");
                return -EINVAL;
        }

        opts.offset = offset;
        *link = bpf_program__attach_kprobe_opts(prog, func, &opts);
        free(func);
        return libbpf_get_error(*link);
}

static int attach_ksyscall(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        LIBBPF_OPTS(bpf_ksyscall_opts, opts);
        const char *syscall_name;

        *link = NULL;

        /* no auto-attach for SEC("ksyscall") and SEC("kretsyscall") */
        if (strcmp(prog->sec_name, "ksyscall") == 0 || strcmp(prog->sec_name, "kretsyscall") == 0)
                return 0;

        opts.retprobe = str_has_pfx(prog->sec_name, "kretsyscall/");
        if (opts.retprobe)
                syscall_name = prog->sec_name + sizeof("kretsyscall/") - 1;
        else
                syscall_name = prog->sec_name + sizeof("ksyscall/") - 1;

        *link = bpf_program__attach_ksyscall(prog, syscall_name, &opts);
        return *link ? 0 : -errno;
}

static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
        const char *spec;
        char *pattern;
        int n;

        *link = NULL;

        /* no auto-attach for SEC("kprobe.multi") and SEC("kretprobe.multi") */
        if (strcmp(prog->sec_name, "kprobe.multi") == 0 ||
            strcmp(prog->sec_name, "kretprobe.multi") == 0)
                return 0;

        opts.retprobe = str_has_pfx(prog->sec_name, "kretprobe.multi/");
        if (opts.retprobe)
                spec = prog->sec_name + sizeof("kretprobe.multi/") - 1;
        else
                spec = prog->sec_name + sizeof("kprobe.multi/") - 1;

        n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern);
        if (n < 1) {
                pr_warn("kprobe multi pattern is invalid: %s\n", pattern);
                return -EINVAL;
        }

        *link = bpf_program__attach_kprobe_multi_opts(prog, pattern, &opts);
        free(pattern);
        return libbpf_get_error(*link);
}

static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
                                         const char *binary_path, uint64_t offset)
{
        int i;

        snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);

        /* sanitize binary_path in the probe name */
        for (i = 0; buf[i]; i++) {
                if (!isalnum(buf[i]))
                        buf[i] = '_';
        }
}

static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
                                          const char *binary_path, size_t offset)
{
        return append_to_file(tracefs_uprobe_events(), "%c:%s/%s %s:0x%zx",
                              retprobe ? 'r' : 'p',
                              retprobe ? "uretprobes" : "uprobes",
                              probe_name, binary_path, offset);
}

static inline int remove_uprobe_event_legacy(const char *probe_name, bool retprobe)
{
        return append_to_file(tracefs_uprobe_events(), "-:%s/%s",
                              retprobe ? "uretprobes" : "uprobes", probe_name);
}

static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retprobe)
{
        char file[512];

        snprintf(file, sizeof(file), "%s/events/%s/%s/id",
                 tracefs_path(), retprobe ? "uretprobes" : "uprobes", probe_name);

        return parse_uint_from_file(file, "%d\n");
}

static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe,
                                         const char *binary_path, size_t offset, int pid)
{
        const size_t attr_sz = sizeof(struct perf_event_attr);
        struct perf_event_attr attr;
        int type, pfd, err;

        err = add_uprobe_event_legacy(probe_name, retprobe, binary_path, offset);
        if (err < 0) {
                pr_warn("failed to add legacy uprobe event for %s:0x%zx: %d\n",
                        binary_path, (size_t)offset, err);
                return err;
        }
        type = determine_uprobe_perf_type_legacy(probe_name, retprobe);
        if (type < 0) {
                err = type;
                pr_warn("failed to determine legacy uprobe event id for %s:0x%zx: %d\n",
                        binary_path, offset, err);
                goto err_clean_legacy;
        }

        memset(&attr, 0, attr_sz);
        attr.size = attr_sz;
        attr.config = type;
        attr.type = PERF_TYPE_TRACEPOINT;

        pfd = syscall(__NR_perf_event_open, &attr,
                      pid < 0 ? -1 : pid, /* pid */
                      pid == -1 ? 0 : -1, /* cpu */
                      -1 /* group_fd */,  PERF_FLAG_FD_CLOEXEC);
        if (pfd < 0) {
                err = -errno;
                pr_warn("legacy uprobe perf_event_open() failed: %d\n", err);
                goto err_clean_legacy;
        }
        return pfd;

err_clean_legacy:
        /* Clear the newly added legacy uprobe_event */
        remove_uprobe_event_legacy(probe_name, retprobe);
        return err;
}

/* Return next ELF section of sh_type after scn, or first of that type if scn is NULL. */
static Elf_Scn *elf_find_next_scn_by_type(Elf *elf, int sh_type, Elf_Scn *scn)
{
        while ((scn = elf_nextscn(elf, scn)) != NULL) {
                GElf_Shdr sh;

                if (!gelf_getshdr(scn, &sh))
                        continue;
                if (sh.sh_type == sh_type)
                        return scn;
        }
        return NULL;
}

/* Find offset of function name in the provided ELF object. "binary_path" is
 * the path to the ELF binary represented by "elf", and only used for error
 * reporting matters. "name" matches symbol name or name@@LIB for library
 * functions.
 */
static long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
{
        int i, sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
        bool is_shared_lib, is_name_qualified;
        long ret = -ENOENT;
        size_t name_len;
        GElf_Ehdr ehdr;

        if (!gelf_getehdr(elf, &ehdr)) {
                pr_warn("elf: failed to get ehdr from %s: %s\n", binary_path, elf_errmsg(-1));
                ret = -LIBBPF_ERRNO__FORMAT;
                goto out;
        }
        /* for shared lib case, we do not need to calculate relative offset */
        is_shared_lib = ehdr.e_type == ET_DYN;

        name_len = strlen(name);
        /* Does name specify "@@LIB"? */
        is_name_qualified = strstr(name, "@@") != NULL;

        /* Search SHT_DYNSYM, SHT_SYMTAB for symbol. This search order is used because if
         * a binary is stripped, it may only have SHT_DYNSYM, and a fully-statically
         * linked binary may not have SHT_DYMSYM, so absence of a section should not be
         * reported as a warning/error.
         */
        for (i = 0; i < ARRAY_SIZE(sh_types); i++) {
                size_t nr_syms, strtabidx, idx;
                Elf_Data *symbols = NULL;
                Elf_Scn *scn = NULL;
                int last_bind = -1;
                const char *sname;
                GElf_Shdr sh;

                scn = elf_find_next_scn_by_type(elf, sh_types[i], NULL);
                if (!scn) {
                        pr_debug("elf: failed to find symbol table ELF sections in '%s'\n",
                                 binary_path);
                        continue;
                }
                if (!gelf_getshdr(scn, &sh))
                        continue;
                strtabidx = sh.sh_link;
                symbols = elf_getdata(scn, 0);
                if (!symbols) {
                        pr_warn("elf: failed to get symbols for symtab section in '%s': %s\n",
                                binary_path, elf_errmsg(-1));
                        ret = -LIBBPF_ERRNO__FORMAT;
                        goto out;
                }
                nr_syms = symbols->d_size / sh.sh_entsize;

                for (idx = 0; idx < nr_syms; idx++) {
                        int curr_bind;
                        GElf_Sym sym;
                        Elf_Scn *sym_scn;
                        GElf_Shdr sym_sh;

                        if (!gelf_getsym(symbols, idx, &sym))
                                continue;

                        if (GELF_ST_TYPE(sym.st_info) != STT_FUNC)
                                continue;

                        sname = elf_strptr(elf, strtabidx, sym.st_name);
                        if (!sname)
                                continue;

                        curr_bind = GELF_ST_BIND(sym.st_info);

                        /* User can specify func, func@@LIB or func@@LIB_VERSION. */
                        if (strncmp(sname, name, name_len) != 0)
                                continue;
                        /* ...but we don't want a search for "foo" to match 'foo2" also, so any
                         * additional characters in sname should be of the form "@@LIB".
                         */
                        if (!is_name_qualified && sname[name_len] != '\0' && sname[name_len] != '@')
                                continue;

                        if (ret >= 0) {
                                /* handle multiple matches */
                                if (last_bind != STB_WEAK && curr_bind != STB_WEAK) {
                                        /* Only accept one non-weak bind. */
                                        pr_warn("elf: ambiguous match for '%s', '%s' in '%s'\n",
                                                sname, name, binary_path);
                                        ret = -LIBBPF_ERRNO__FORMAT;
                                        goto out;
                                } else if (curr_bind == STB_WEAK) {
                                        /* already have a non-weak bind, and
                                         * this is a weak bind, so ignore.
                                         */
                                        continue;
                                }
                        }

                        /* Transform symbol's virtual address (absolute for
                         * binaries and relative for shared libs) into file
                         * offset, which is what kernel is expecting for
                         * uprobe/uretprobe attachment.
                         * See Documentation/trace/uprobetracer.rst for more
                         * details.
                         * This is done by looking up symbol's containing
                         * section's header and using it's virtual address
                         * (sh_addr) and corresponding file offset (sh_offset)
                         * to transform sym.st_value (virtual address) into
                         * desired final file offset.
                         */
                        sym_scn = elf_getscn(elf, sym.st_shndx);
                        if (!sym_scn)
                                continue;
                        if (!gelf_getshdr(sym_scn, &sym_sh))
                                continue;

                        ret = sym.st_value - sym_sh.sh_addr + sym_sh.sh_offset;
                        last_bind = curr_bind;
                }
                if (ret > 0)
                        break;
        }

        if (ret > 0) {
                pr_debug("elf: symbol address match for '%s' in '%s': 0x%lx\n", name, binary_path,
                         ret);
        } else {
                if (ret == 0) {
                        pr_warn("elf: '%s' is 0 in symtab for '%s': %s\n", name, binary_path,
                                is_shared_lib ? "should not be 0 in a shared library" :
                                                "try using shared library path instead");
                        ret = -ENOENT;
                } else {
                        pr_warn("elf: failed to find symbol '%s' in '%s'\n", name, binary_path);
                }
        }
out:
        return ret;
}

/* Find offset of function name in ELF object specified by path. "name" matches
 * symbol name or name@@LIB for library functions.
 */
static long elf_find_func_offset_from_file(const char *binary_path, const char *name)
{
        char errmsg[STRERR_BUFSIZE];
        long ret = -ENOENT;
        Elf *elf;
        int fd;

        fd = open(binary_path, O_RDONLY | O_CLOEXEC);
        if (fd < 0) {
                ret = -errno;
                pr_warn("failed to open %s: %s\n", binary_path,
                        libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));
                return ret;
        }
        elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
        if (!elf) {
                pr_warn("elf: could not read elf from %s: %s\n", binary_path, elf_errmsg(-1));
                close(fd);
                return -LIBBPF_ERRNO__FORMAT;
        }

        ret = elf_find_func_offset(elf, binary_path, name);
        elf_end(elf);
        close(fd);
        return ret;
}

/* Find offset of function name in archive specified by path. Currently
 * supported are .zip files that do not compress their contents, as used on
 * Android in the form of APKs, for example. "file_name" is the name of the ELF
 * file inside the archive. "func_name" matches symbol name or name@@LIB for
 * library functions.
 *
 * An overview of the APK format specifically provided here:
 * https://en.wikipedia.org/w/index.php?title=Apk_(file_format)&oldid=1139099120#Package_contents
 */
static long elf_find_func_offset_from_archive(const char *archive_path, const char *file_name,
                                              const char *func_name)
{
        struct zip_archive *archive;
        struct zip_entry entry;
        long ret;
        Elf *elf;

        archive = zip_archive_open(archive_path);
        if (IS_ERR(archive)) {
                ret = PTR_ERR(archive);
                pr_warn("zip: failed to open %s: %ld\n", archive_path, ret);
                return ret;
        }

        ret = zip_archive_find_entry(archive, file_name, &entry);
        if (ret) {
                pr_warn("zip: could not find archive member %s in %s: %ld\n", file_name,
                        archive_path, ret);
                goto out;
        }
        pr_debug("zip: found entry for %s in %s at 0x%lx\n", file_name, archive_path,
                 (unsigned long)entry.data_offset);

        if (entry.compression) {
                pr_warn("zip: entry %s of %s is compressed and cannot be handled\n", file_name,
                        archive_path);
                ret = -LIBBPF_ERRNO__FORMAT;
                goto out;
        }

        elf = elf_memory((void *)entry.data, entry.data_length);
        if (!elf) {
                pr_warn("elf: could not read elf file %s from %s: %s\n", file_name, archive_path,
                        elf_errmsg(-1));
                ret = -LIBBPF_ERRNO__LIBELF;
                goto out;
        }

        ret = elf_find_func_offset(elf, file_name, func_name);
        if (ret > 0) {
                pr_debug("elf: symbol address match for %s of %s in %s: 0x%x + 0x%lx = 0x%lx\n",
                         func_name, file_name, archive_path, entry.data_offset, ret,
                         ret + entry.data_offset);
                ret += entry.data_offset;
        }
        elf_end(elf);

out:
        zip_archive_close(archive);
        return ret;
}

static const char *arch_specific_lib_paths(void)
{
        /*
         * Based on https://packages.debian.org/sid/libc6.
         *
         * Assume that the traced program is built for the same architecture
         * as libbpf, which should cover the vast majority of cases.
         */
#if defined(__x86_64__)
        return "/lib/x86_64-linux-gnu";
#elif defined(__i386__)
        return "/lib/i386-linux-gnu";
#elif defined(__s390x__)
        return "/lib/s390x-linux-gnu";
#elif defined(__s390__)
        return "/lib/s390-linux-gnu";
#elif defined(__arm__) && defined(__SOFTFP__)
        return "/lib/arm-linux-gnueabi";
#elif defined(__arm__) && !defined(__SOFTFP__)
        return "/lib/arm-linux-gnueabihf";
#elif defined(__aarch64__)
        return "/lib/aarch64-linux-gnu";
#elif defined(__mips__) && defined(__MIPSEL__) && _MIPS_SZLONG == 64
        return "/lib/mips64el-linux-gnuabi64";
#elif defined(__mips__) && defined(__MIPSEL__) && _MIPS_SZLONG == 32
        return "/lib/mipsel-linux-gnu";
#elif defined(__powerpc64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
        return "/lib/powerpc64le-linux-gnu";
#elif defined(__sparc__) && defined(__arch64__)
        return "/lib/sparc64-linux-gnu";
#elif defined(__riscv) && __riscv_xlen == 64
        return "/lib/riscv64-linux-gnu";
#else
        return NULL;
#endif
}

/* Get full path to program/shared library. */
static int resolve_full_path(const char *file, char *result, size_t result_sz)
{
        const char *search_paths[3] = {};
        int i, perm;

        if (str_has_sfx(file, ".so") || strstr(file, ".so.")) {
                search_paths[0] = getenv("LD_LIBRARY_PATH");
                search_paths[1] = "/usr/lib64:/usr/lib";
                search_paths[2] = arch_specific_lib_paths();
                perm = R_OK;
        } else {
                search_paths[0] = getenv("PATH");
                search_paths[1] = "/usr/bin:/usr/sbin";
                perm = R_OK | X_OK;
        }

        for (i = 0; i < ARRAY_SIZE(search_paths); i++) {
                const char *s;

                if (!search_paths[i])
                        continue;
                for (s = search_paths[i]; s != NULL; s = strchr(s, ':')) {
                        char *next_path;
                        int seg_len;

                        if (s[0] == ':')
                                s++;
                        next_path = strchr(s, ':');
                        seg_len = next_path ? next_path - s : strlen(s);
                        if (!seg_len)
                                continue;
                        snprintf(result, result_sz, "%.*s/%s", seg_len, s, file);
                        /* ensure it has required permissions */
                        if (faccessat(AT_FDCWD, result, perm, AT_EACCESS) < 0)
                                continue;
                        pr_debug("resolved '%s' to '%s'\n", file, result);
                        return 0;
                }
        }
        return -ENOENT;
}

LIBBPF_API struct bpf_link *
bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
                                const char *binary_path, size_t func_offset,
                                const struct bpf_uprobe_opts *opts)
{
        const char *archive_path = NULL, *archive_sep = NULL;
        char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
        DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
        enum probe_attach_mode attach_mode;
        char full_path[PATH_MAX];
        struct bpf_link *link;
        size_t ref_ctr_off;
        int pfd, err;
        bool retprobe, legacy;
        const char *func_name;

        if (!OPTS_VALID(opts, bpf_uprobe_opts))
                return libbpf_err_ptr(-EINVAL);

        attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
        retprobe = OPTS_GET(opts, retprobe, false);
        ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
        pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);

        if (!binary_path)
                return libbpf_err_ptr(-EINVAL);

        /* Check if "binary_path" refers to an archive. */
        archive_sep = strstr(binary_path, "!/");
        if (archive_sep) {
                full_path[0] = '\0';
                libbpf_strlcpy(full_path, binary_path,
                               min(sizeof(full_path), (size_t)(archive_sep - binary_path + 1)));
                archive_path = full_path;
                binary_path = archive_sep + 2;
        } else if (!strchr(binary_path, '/')) {
                err = resolve_full_path(binary_path, full_path, sizeof(full_path));
                if (err) {
                        pr_warn("prog '%s': failed to resolve full path for '%s': %d\n",
                                prog->name, binary_path, err);
                        return libbpf_err_ptr(err);
                }
                binary_path = full_path;
        }
        func_name = OPTS_GET(opts, func_name, NULL);
        if (func_name) {
                long sym_off;

                if (archive_path) {
                        sym_off = elf_find_func_offset_from_archive(archive_path, binary_path,
                                                                    func_name);
                        binary_path = archive_path;
                } else {
                        sym_off = elf_find_func_offset_from_file(binary_path, func_name);
                }
                if (sym_off < 0)
                        return libbpf_err_ptr(sym_off);
                func_offset += sym_off;
        }

        legacy = determine_uprobe_perf_type() < 0;
        switch (attach_mode) {
        case PROBE_ATTACH_MODE_LEGACY:
                legacy = true;
                pe_opts.force_ioctl_attach = true;
                break;
        case PROBE_ATTACH_MODE_PERF:
                if (legacy)
                        return libbpf_err_ptr(-ENOTSUP);
                pe_opts.force_ioctl_attach = true;
                break;
        case PROBE_ATTACH_MODE_LINK:
                if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
                        return libbpf_err_ptr(-ENOTSUP);
                break;
        case PROBE_ATTACH_MODE_DEFAULT:
                break;
        default:
                return libbpf_err_ptr(-EINVAL);
        }

        if (!legacy) {
                pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
                                            func_offset, pid, ref_ctr_off);
        } else {
                char probe_name[PATH_MAX + 64];

                if (ref_ctr_off)
                        return libbpf_err_ptr(-EINVAL);

                gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
                                             binary_path, func_offset);

                legacy_probe = strdup(probe_name);
                if (!legacy_probe)
                        return libbpf_err_ptr(-ENOMEM);

                pfd = perf_event_uprobe_open_legacy(legacy_probe, retprobe,
                                                    binary_path, func_offset, pid);
        }
        if (pfd < 0) {
                err = -errno;
                pr_warn("prog '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
                        prog->name, retprobe ? "uretprobe" : "uprobe",
                        binary_path, func_offset,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_out;
        }

        link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
        err = libbpf_get_error(link);
        if (err) {
                close(pfd);
                pr_warn("prog '%s': failed to attach to %s '%s:0x%zx': %s\n",
                        prog->name, retprobe ? "uretprobe" : "uprobe",
                        binary_path, func_offset,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                goto err_clean_legacy;
        }
        if (legacy) {
                struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);

                perf_link->legacy_probe_name = legacy_probe;
                perf_link->legacy_is_kprobe = false;
                perf_link->legacy_is_retprobe = retprobe;
        }
        return link;

err_clean_legacy:
        if (legacy)
                remove_uprobe_event_legacy(legacy_probe, retprobe);
err_out:
        free(legacy_probe);
        return libbpf_err_ptr(err);
}

/* Format of u[ret]probe section definition supporting auto-attach:
 * u[ret]probe/binary:function[+offset]
 *
 * binary can be an absolute/relative path or a filename; the latter is resolved to a
 * full binary path via bpf_program__attach_uprobe_opts.
 *
 * Specifying uprobe+ ensures we carry out strict matching; either "uprobe" must be
 * specified (and auto-attach is not possible) or the above format is specified for
 * auto-attach.
 */
static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);
        char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;
        int n, ret = -EINVAL;
        long offset = 0;

        *link = NULL;

        n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.]+%li",
                   &probe_type, &binary_path, &func_name, &offset);
        switch (n) {
        case 1:
                /* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */
                ret = 0;
                break;
        case 2:
                pr_warn("prog '%s': section '%s' missing ':function[+offset]' specification\n",
                        prog->name, prog->sec_name);
                break;
        case 3:
        case 4:
                opts.retprobe = strcmp(probe_type, "uretprobe") == 0 ||
                                strcmp(probe_type, "uretprobe.s") == 0;
                if (opts.retprobe && offset != 0) {
                        pr_warn("prog '%s': uretprobes do not support offset specification\n",
                                prog->name);
                        break;
                }
                opts.func_name = func_name;
                *link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);
                ret = libbpf_get_error(*link);
                break;
        default:
                pr_warn("prog '%s': invalid format of section definition '%s'\n", prog->name,
                        prog->sec_name);
                break;
        }
        free(probe_type);
        free(binary_path);
        free(func_name);

        return ret;
}

struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
                                            bool retprobe, pid_t pid,
                                            const char *binary_path,
                                            size_t func_offset)
{
        DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts, .retprobe = retprobe);

        return bpf_program__attach_uprobe_opts(prog, pid, binary_path, func_offset, &opts);
}

struct bpf_link *bpf_program__attach_usdt(const struct bpf_program *prog,
                                          pid_t pid, const char *binary_path,
                                          const char *usdt_provider, const char *usdt_name,
                                          const struct bpf_usdt_opts *opts)
{
        char resolved_path[512];
        struct bpf_object *obj = prog->obj;
        struct bpf_link *link;
        __u64 usdt_cookie;
        int err;

        if (!OPTS_VALID(opts, bpf_uprobe_opts))
                return libbpf_err_ptr(-EINVAL);

        if (bpf_program__fd(prog) < 0) {
                pr_warn("prog '%s': can't attach BPF program w/o FD (did you load it?)\n",
                        prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        if (!binary_path)
                return libbpf_err_ptr(-EINVAL);

        if (!strchr(binary_path, '/')) {
                err = resolve_full_path(binary_path, resolved_path, sizeof(resolved_path));
                if (err) {
                        pr_warn("prog '%s': failed to resolve full path for '%s': %d\n",
                                prog->name, binary_path, err);
                        return libbpf_err_ptr(err);
                }
                binary_path = resolved_path;
        }

        /* USDT manager is instantiated lazily on first USDT attach. It will
         * be destroyed together with BPF object in bpf_object__close().
         */
        if (IS_ERR(obj->usdt_man))
                return libbpf_ptr(obj->usdt_man);
        if (!obj->usdt_man) {
                obj->usdt_man = usdt_manager_new(obj);
                if (IS_ERR(obj->usdt_man))
                        return libbpf_ptr(obj->usdt_man);
        }

        usdt_cookie = OPTS_GET(opts, usdt_cookie, 0);
        link = usdt_manager_attach_usdt(obj->usdt_man, prog, pid, binary_path,
                                        usdt_provider, usdt_name, usdt_cookie);
        err = libbpf_get_error(link);
        if (err)
                return libbpf_err_ptr(err);
        return link;
}

static int attach_usdt(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        char *path = NULL, *provider = NULL, *name = NULL;
        const char *sec_name;
        int n, err;

        sec_name = bpf_program__section_name(prog);
        if (strcmp(sec_name, "usdt") == 0) {
                /* no auto-attach for just SEC("usdt") */
                *link = NULL;
                return 0;
        }

        n = sscanf(sec_name, "usdt/%m[^:]:%m[^:]:%m[^:]", &path, &provider, &name);
        if (n != 3) {
                pr_warn("invalid section '%s', expected SEC(\"usdt/<path>:<provider>:<name>\")\n",
                        sec_name);
                err = -EINVAL;
        } else {
                *link = bpf_program__attach_usdt(prog, -1 /* any process */, path,
                                                 provider, name, NULL);
                err = libbpf_get_error(*link);
        }
        free(path);
        free(provider);
        free(name);
        return err;
}

static int determine_tracepoint_id(const char *tp_category,
                                   const char *tp_name)
{
        char file[PATH_MAX];
        int ret;

        ret = snprintf(file, sizeof(file), "%s/events/%s/%s/id",
                       tracefs_path(), tp_category, tp_name);
        if (ret < 0)
                return -errno;
        if (ret >= sizeof(file)) {
                pr_debug("tracepoint %s/%s path is too long\n",
                         tp_category, tp_name);
                return -E2BIG;
        }
        return parse_uint_from_file(file, "%d\n");
}

static int perf_event_open_tracepoint(const char *tp_category,
                                      const char *tp_name)
{
        const size_t attr_sz = sizeof(struct perf_event_attr);
        struct perf_event_attr attr;
        char errmsg[STRERR_BUFSIZE];
        int tp_id, pfd, err;

        tp_id = determine_tracepoint_id(tp_category, tp_name);
        if (tp_id < 0) {
                pr_warn("failed to determine tracepoint '%s/%s' perf event ID: %s\n",
                        tp_category, tp_name,
                        libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
                return tp_id;
        }

        memset(&attr, 0, attr_sz);
        attr.type = PERF_TYPE_TRACEPOINT;
        attr.size = attr_sz;
        attr.config = tp_id;

        pfd = syscall(__NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
                      -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
        if (pfd < 0) {
                err = -errno;
                pr_warn("tracepoint '%s/%s' perf_event_open() failed: %s\n",
                        tp_category, tp_name,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                return err;
        }
        return pfd;
}

struct bpf_link *bpf_program__attach_tracepoint_opts(const struct bpf_program *prog,
                                                     const char *tp_category,
                                                     const char *tp_name,
                                                     const struct bpf_tracepoint_opts *opts)
{
        DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
        char errmsg[STRERR_BUFSIZE];
        struct bpf_link *link;
        int pfd, err;

        if (!OPTS_VALID(opts, bpf_tracepoint_opts))
                return libbpf_err_ptr(-EINVAL);

        pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);

        pfd = perf_event_open_tracepoint(tp_category, tp_name);
        if (pfd < 0) {
                pr_warn("prog '%s': failed to create tracepoint '%s/%s' perf event: %s\n",
                        prog->name, tp_category, tp_name,
                        libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
                return libbpf_err_ptr(pfd);
        }
        link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
        err = libbpf_get_error(link);
        if (err) {
                close(pfd);
                pr_warn("prog '%s': failed to attach to tracepoint '%s/%s': %s\n",
                        prog->name, tp_category, tp_name,
                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
                return libbpf_err_ptr(err);
        }
        return link;
}

struct bpf_link *bpf_program__attach_tracepoint(const struct bpf_program *prog,
                                                const char *tp_category,
                                                const char *tp_name)
{
        return bpf_program__attach_tracepoint_opts(prog, tp_category, tp_name, NULL);
}

static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        char *sec_name, *tp_cat, *tp_name;

        *link = NULL;

        /* no auto-attach for SEC("tp") or SEC("tracepoint") */
        if (strcmp(prog->sec_name, "tp") == 0 || strcmp(prog->sec_name, "tracepoint") == 0)
                return 0;

        sec_name = strdup(prog->sec_name);
        if (!sec_name)
                return -ENOMEM;

        /* extract "tp/<category>/<name>" or "tracepoint/<category>/<name>" */
        if (str_has_pfx(prog->sec_name, "tp/"))
                tp_cat = sec_name + sizeof("tp/") - 1;
        else
                tp_cat = sec_name + sizeof("tracepoint/") - 1;
        tp_name = strchr(tp_cat, '/');
        if (!tp_name) {
                free(sec_name);
                return -EINVAL;
        }
        *tp_name = '\0';
        tp_name++;

        *link = bpf_program__attach_tracepoint(prog, tp_cat, tp_name);
        free(sec_name);
        return libbpf_get_error(*link);
}

struct bpf_link *bpf_program__attach_raw_tracepoint(const struct bpf_program *prog,
                                                    const char *tp_name)
{
        char errmsg[STRERR_BUFSIZE];
        struct bpf_link *link;
        int prog_fd, pfd;

        prog_fd = bpf_program__fd(prog);
        if (prog_fd < 0) {
                pr_warn("prog '%s': can't attach before loaded\n", prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        link = calloc(1, sizeof(*link));
        if (!link)
                return libbpf_err_ptr(-ENOMEM);
        link->detach = &bpf_link__detach_fd;

        pfd = bpf_raw_tracepoint_open(tp_name, prog_fd);
        if (pfd < 0) {
                pfd = -errno;
                free(link);
                pr_warn("prog '%s': failed to attach to raw tracepoint '%s': %s\n",
                        prog->name, tp_name, libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
                return libbpf_err_ptr(pfd);
        }
        link->fd = pfd;
        return link;
}

static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        static const char *const prefixes[] = {
                "raw_tp",
                "raw_tracepoint",
                "raw_tp.w",
                "raw_tracepoint.w",
        };
        size_t i;
        const char *tp_name = NULL;

        *link = NULL;

        for (i = 0; i < ARRAY_SIZE(prefixes); i++) {
                size_t pfx_len;

                if (!str_has_pfx(prog->sec_name, prefixes[i]))
                        continue;

                pfx_len = strlen(prefixes[i]);
                /* no auto-attach case of, e.g., SEC("raw_tp") */
                if (prog->sec_name[pfx_len] == '\0')
                        return 0;

                if (prog->sec_name[pfx_len] != '/')
                        continue;

                tp_name = prog->sec_name + pfx_len + 1;
                break;
        }

        if (!tp_name) {
                pr_warn("prog '%s': invalid section name '%s'\n",
                        prog->name, prog->sec_name);
                return -EINVAL;
        }

        *link = bpf_program__attach_raw_tracepoint(prog, tp_name);
        return libbpf_get_error(*link);
}

/* Common logic for all BPF program types that attach to a btf_id */
static struct bpf_link *bpf_program__attach_btf_id(const struct bpf_program *prog,
                                                   const struct bpf_trace_opts *opts)
{
        LIBBPF_OPTS(bpf_link_create_opts, link_opts);
        char errmsg[STRERR_BUFSIZE];
        struct bpf_link *link;
        int prog_fd, pfd;

        if (!OPTS_VALID(opts, bpf_trace_opts))
                return libbpf_err_ptr(-EINVAL);

        prog_fd = bpf_program__fd(prog);
        if (prog_fd < 0) {
                pr_warn("prog '%s': can't attach before loaded\n", prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        link = calloc(1, sizeof(*link));
        if (!link)
                return libbpf_err_ptr(-ENOMEM);
        link->detach = &bpf_link__detach_fd;

        /* libbpf is smart enough to redirect to BPF_RAW_TRACEPOINT_OPEN on old kernels */
        link_opts.tracing.cookie = OPTS_GET(opts, cookie, 0);
        pfd = bpf_link_create(prog_fd, 0, bpf_program__expected_attach_type(prog), &link_opts);
        if (pfd < 0) {
                pfd = -errno;
                free(link);
                pr_warn("prog '%s': failed to attach: %s\n",
                        prog->name, libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
                return libbpf_err_ptr(pfd);
        }
        link->fd = pfd;
        return link;
}

struct bpf_link *bpf_program__attach_trace(const struct bpf_program *prog)
{
        return bpf_program__attach_btf_id(prog, NULL);
}

struct bpf_link *bpf_program__attach_trace_opts(const struct bpf_program *prog,
                                                const struct bpf_trace_opts *opts)
{
        return bpf_program__attach_btf_id(prog, opts);
}

struct bpf_link *bpf_program__attach_lsm(const struct bpf_program *prog)
{
        return bpf_program__attach_btf_id(prog, NULL);
}

static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        *link = bpf_program__attach_trace(prog);
        return libbpf_get_error(*link);
}

static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        *link = bpf_program__attach_lsm(prog);
        return libbpf_get_error(*link);
}

static struct bpf_link *
bpf_program__attach_fd(const struct bpf_program *prog, int target_fd, int btf_id,
                       const char *target_name)
{
        DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts,
                            .target_btf_id = btf_id);
        enum bpf_attach_type attach_type;
        char errmsg[STRERR_BUFSIZE];
        struct bpf_link *link;
        int prog_fd, link_fd;

        prog_fd = bpf_program__fd(prog);
        if (prog_fd < 0) {
                pr_warn("prog '%s': can't attach before loaded\n", prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        link = calloc(1, sizeof(*link));
        if (!link)
                return libbpf_err_ptr(-ENOMEM);
        link->detach = &bpf_link__detach_fd;

        attach_type = bpf_program__expected_attach_type(prog);
        link_fd = bpf_link_create(prog_fd, target_fd, attach_type, &opts);
        if (link_fd < 0) {
                link_fd = -errno;
                free(link);
                pr_warn("prog '%s': failed to attach to %s: %s\n",
                        prog->name, target_name,
                        libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg)));
                return libbpf_err_ptr(link_fd);
        }
        link->fd = link_fd;
        return link;
}

struct bpf_link *
bpf_program__attach_cgroup(const struct bpf_program *prog, int cgroup_fd)
{
        return bpf_program__attach_fd(prog, cgroup_fd, 0, "cgroup");
}

struct bpf_link *
bpf_program__attach_netns(const struct bpf_program *prog, int netns_fd)
{
        return bpf_program__attach_fd(prog, netns_fd, 0, "netns");
}

struct bpf_link *bpf_program__attach_xdp(const struct bpf_program *prog, int ifindex)
{
        /* target_fd/target_ifindex use the same field in LINK_CREATE */
        return bpf_program__attach_fd(prog, ifindex, 0, "xdp");
}

struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
                                              int target_fd,
                                              const char *attach_func_name)
{
        int btf_id;

        if (!!target_fd != !!attach_func_name) {
                pr_warn("prog '%s': supply none or both of target_fd and attach_func_name\n",
                        prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        if (prog->type != BPF_PROG_TYPE_EXT) {
                pr_warn("prog '%s': only BPF_PROG_TYPE_EXT can attach as freplace",
                        prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        if (target_fd) {
                btf_id = libbpf_find_prog_btf_id(attach_func_name, target_fd);
                if (btf_id < 0)
                        return libbpf_err_ptr(btf_id);

                return bpf_program__attach_fd(prog, target_fd, btf_id, "freplace");
        } else {
                /* no target, so use raw_tracepoint_open for compatibility
                 * with old kernels
                 */
                return bpf_program__attach_trace(prog);
        }
}

struct bpf_link *
bpf_program__attach_iter(const struct bpf_program *prog,
                         const struct bpf_iter_attach_opts *opts)
{
        DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_create_opts);
        char errmsg[STRERR_BUFSIZE];
        struct bpf_link *link;
        int prog_fd, link_fd;
        __u32 target_fd = 0;

        if (!OPTS_VALID(opts, bpf_iter_attach_opts))
                return libbpf_err_ptr(-EINVAL);

        link_create_opts.iter_info = OPTS_GET(opts, link_info, (void *)0);
        link_create_opts.iter_info_len = OPTS_GET(opts, link_info_len, 0);

        prog_fd = bpf_program__fd(prog);
        if (prog_fd < 0) {
                pr_warn("prog '%s': can't attach before loaded\n", prog->name);
                return libbpf_err_ptr(-EINVAL);
        }

        link = calloc(1, sizeof(*link));
        if (!link)
                return libbpf_err_ptr(-ENOMEM);
        link->detach = &bpf_link__detach_fd;

        link_fd = bpf_link_create(prog_fd, target_fd, BPF_TRACE_ITER,
                                  &link_create_opts);
        if (link_fd < 0) {
                link_fd = -errno;
                free(link);
                pr_warn("prog '%s': failed to attach to iterator: %s\n",
                        prog->name, libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg)));
                return libbpf_err_ptr(link_fd);
        }
        link->fd = link_fd;
        return link;
}

static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
        *link = bpf_program__attach_iter(prog, NULL);
        return libbpf_get_error(*link);
}

struct bpf_link *bpf_program__attach(const struct bpf_program *prog)
{
        struct bpf_link *link = NULL;
        int err;

        if (!prog->sec_def || !prog->sec_def->prog_attach_fn)
                return libbpf_err_ptr(-EOPNOTSUPP);

        err = prog->sec_def->prog_attach_fn(prog, prog->sec_def->cookie, &link);
        if (err)
                return libbpf_err_ptr(err);

        /* When calling bpf_program__attach() explicitly, auto-attach support
         * is expected to work, so NULL returned link is considered an error.
         * This is different for skeleton's attach, see comment in
         * bpf_object__attach_skeleton().
         */
        if (!link)
                return libbpf_err_ptr(-EOPNOTSUPP);

        return link;
}

struct bpf_link_struct_ops {
        struct bpf_link link;
        int map_fd;
};

static int bpf_link__detach_struct_ops(struct bpf_link *link)
{
        struct bpf_link_struct_ops *st_link;
        __u32 zero = 0;

        st_link = container_of(link, struct bpf_link_struct_ops, link);

        if (st_link->map_fd < 0)
                /* w/o a real link */
                return bpf_map_delete_elem(link->fd, &zero);

        return close(link->fd);
}

struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
{
        struct bpf_link_struct_ops *link;
        __u32 zero = 0;
        int err, fd;

        if (!bpf_map__is_struct_ops(map) || map->fd == -1)
                return libbpf_err_ptr(-EINVAL);

        link = calloc(1, sizeof(*link));
        if (!link)
                return libbpf_err_ptr(-EINVAL);

        /* kern_vdata should be prepared during the loading phase. */
        err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0);
        /* It can be EBUSY if the map has been used to create or
         * update a link before.  We don't allow updating the value of
         * a struct_ops once it is set.  That ensures that the value
         * never changed.  So, it is safe to skip EBUSY.
         */
        if (err && (!(map->def.map_flags & BPF_F_LINK) || err != -EBUSY)) {
                free(link);
                return libbpf_err_ptr(err);
        }

        link->link.detach = bpf_link__detach_struct_ops;

        if (!(map->def.map_flags & BPF_F_LINK)) {
                /* w/o a real link */
                link->link.fd = map->fd;
                link->map_fd = -1;
                return &link->link;
        }

        fd = bpf_link_create(map->fd, 0, BPF_STRUCT_OPS, NULL);
        if (fd < 0) {
                free(link);
                return libbpf_err_ptr(fd);
        }

        link->link.fd = fd;
        link->map_fd = map->fd;

        return &link->link;
}

/*
 * Swap the back struct_ops of a link with a new struct_ops map.
 */
int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map)
{
        struct bpf_link_struct_ops *st_ops_link;
        __u32 zero = 0;
        int err;

        if (!bpf_map__is_struct_ops(map) || map->fd < 0)
                return -EINVAL;

        st_ops_link = container_of(link, struct bpf_link_struct_ops, link);
        /* Ensure the type of a link is correct */
        if (st_ops_link->map_fd < 0)
                return -EINVAL;

        err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0);
        /* It can be EBUSY if the map has been used to create or
         * update a link before.  We don't allow updating the value of
         * a struct_ops once it is set.  That ensures that the value
         * never changed.  So, it is safe to skip EBUSY.
         */
        if (err && err != -EBUSY)
                return err;

        err = bpf_link_update(link->fd, map->fd, NULL);
        if (err < 0)
                return err;

        st_ops_link->map_fd = map->fd;

        return 0;
}

typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr,
                                                          void *private_data);

static enum bpf_perf_event_ret
perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
                       void **copy_mem, size_t *copy_size,
                       bpf_perf_event_print_t fn, void *private_data)
{
        struct perf_event_mmap_page *header = mmap_mem;
        __u64 data_head = ring_buffer_read_head(header);
        __u64 data_tail = header->data_tail;
        void *base = ((__u8 *)header) + page_size;
        int ret = LIBBPF_PERF_EVENT_CONT;
        struct perf_event_header *ehdr;
        size_t ehdr_size;

        while (data_head != data_tail) {
                ehdr = base + (data_tail & (mmap_size - 1));
                ehdr_size = ehdr->size;

                if (((void *)ehdr) + ehdr_size > base + mmap_size) {
                        void *copy_start = ehdr;
                        size_t len_first = base + mmap_size - copy_start;
                        size_t len_secnd = ehdr_size - len_first;

                        if (*copy_size < ehdr_size) {
                                free(*copy_mem);
                                *copy_mem = malloc(ehdr_size);
                                if (!*copy_mem) {
                                        *copy_size = 0;
                                        ret = LIBBPF_PERF_EVENT_ERROR;
                                        break;
                                }
                                *copy_size = ehdr_size;
                        }

                        memcpy(*copy_mem, copy_start, len_first);
                        memcpy(*copy_mem + len_first, base, len_secnd);
                        ehdr = *copy_mem;
                }

                ret = fn(ehdr, private_data);
                data_tail += ehdr_size;
                if (ret != LIBBPF_PERF_EVENT_CONT)
                        break;
        }

        ring_buffer_write_tail(header, data_tail);
        return libbpf_err(ret);
}

struct perf_buffer;

struct perf_buffer_params {
        struct perf_event_attr *attr;
        /* if event_cb is specified, it takes precendence */
        perf_buffer_event_fn event_cb;
        /* sample_cb and lost_cb are higher-level common-case callbacks */
        perf_buffer_sample_fn sample_cb;
        perf_buffer_lost_fn lost_cb;
        void *ctx;
        int cpu_cnt;
        int *cpus;
        int *map_keys;
};

struct perf_cpu_buf {
        struct perf_buffer *pb;
        void *base; /* mmap()'ed memory */
        void *buf; /* for reconstructing segmented data */
        size_t buf_size;
        int fd;
        int cpu;
        int map_key;
};

struct perf_buffer {
        perf_buffer_event_fn event_cb;
        perf_buffer_sample_fn sample_cb;
        perf_buffer_lost_fn lost_cb;
        void *ctx; /* passed into callbacks */

        size_t page_size;
        size_t mmap_size;
        struct perf_cpu_buf **cpu_bufs;
        struct epoll_event *events;
        int cpu_cnt; /* number of allocated CPU buffers */
        int epoll_fd; /* perf event FD */
        int map_fd; /* BPF_MAP_TYPE_PERF_EVENT_ARRAY BPF map FD */
};

static void perf_buffer__free_cpu_buf(struct perf_buffer *pb,
                                      struct perf_cpu_buf *cpu_buf)
{
        if (!cpu_buf)
                return;
        if (cpu_buf->base &&
            munmap(cpu_buf->base, pb->mmap_size + pb->page_size))
                pr_warn("failed to munmap cpu_buf #%d\n", cpu_buf->cpu);
        if (cpu_buf->fd >= 0) {
                ioctl(cpu_buf->fd, PERF_EVENT_IOC_DISABLE, 0);
                close(cpu_buf->fd);
        }
        free(cpu_buf->buf);
        free(cpu_buf);
}

void perf_buffer__free(struct perf_buffer *pb)
{
        int i;

        if (IS_ERR_OR_NULL(pb))
                return;
        if (pb->cpu_bufs) {
                for (i = 0; i < pb->cpu_cnt; i++) {
                        struct perf_cpu_buf *cpu_buf = pb->cpu_bufs[i];

                        if (!cpu_buf)
                                continue;

                        bpf_map_delete_elem(pb->map_fd, &cpu_buf->map_key);
                        perf_buffer__free_cpu_buf(pb, cpu_buf);
                }
                free(pb->cpu_bufs);
        }
        if (pb->epoll_fd >= 0)
                close(pb->epoll_fd);
        free(pb->events);
        free(pb);
}

static struct perf_cpu_buf *
perf_buffer__open_cpu_buf(struct perf_buffer *pb, struct perf_event_attr *attr,
                          int cpu, int map_key)
{
        struct perf_cpu_buf *cpu_buf;
        char msg[STRERR_BUFSIZE];
        int err;

        cpu_buf = calloc(1, sizeof(*cpu_buf));
        if (!cpu_buf)
                return ERR_PTR(-ENOMEM);

        cpu_buf->pb = pb;
        cpu_buf->cpu = cpu;
        cpu_buf->map_key = map_key;

        cpu_buf->fd = syscall(__NR_perf_event_open, attr, -1 /* pid */, cpu,
                              -1, PERF_FLAG_FD_CLOEXEC);
        if (cpu_buf->fd < 0) {
                err = -errno;
                pr_warn("failed to open perf buffer event on cpu #%d: %s\n",
                        cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
                goto error;
        }

        cpu_buf->base = mmap(NULL, pb->mmap_size + pb->page_size,
                             PROT_READ | PROT_WRITE, MAP_SHARED,
                             cpu_buf->fd, 0);
        if (cpu_buf->base == MAP_FAILED) {
                cpu_buf->base = NULL;
                err = -errno;
                pr_warn("failed to mmap perf buffer on cpu #%d: %s\n",
                        cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
                goto error;
        }

        if (ioctl(cpu_buf->fd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
                err = -errno;
                pr_warn("failed to enable perf buffer event on cpu #%d: %s\n",
                        cpu, libbpf_strerror_r(err, msg, sizeof(msg)));
                goto error;
        }

        return cpu_buf;

error:
        perf_buffer__free_cpu_buf(pb, cpu_buf);
        return (struct perf_cpu_buf *)ERR_PTR(err);
}

static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
                                              struct perf_buffer_params *p);

struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
                                     perf_buffer_sample_fn sample_cb,
                                     perf_buffer_lost_fn lost_cb,
                                     void *ctx,
                                     const struct perf_buffer_opts *opts)
{
        const size_t attr_sz = sizeof(struct perf_event_attr);
        struct perf_buffer_params p = {};
        struct perf_event_attr attr;
        __u32 sample_period;

        if (!OPTS_VALID(opts, perf_buffer_opts))
                return libbpf_err_ptr(-EINVAL);

        sample_period = OPTS_GET(opts, sample_period, 1);
        if (!sample_period)
                sample_period = 1;

        memset(&attr, 0, attr_sz);
        attr.size = attr_sz;
        attr.config = PERF_COUNT_SW_BPF_OUTPUT;
        attr.type = PERF_TYPE_SOFTWARE;
        attr.sample_type = PERF_SAMPLE_RAW;
        attr.sample_period = sample_period;
        attr.wakeup_events = sample_period;

        p.attr = &attr;
        p.sample_cb = sample_cb;
        p.lost_cb = lost_cb;
        p.ctx = ctx;

        return libbpf_ptr(__perf_buffer__new(map_fd, page_cnt, &p));
}

struct perf_buffer *perf_buffer__new_raw(int map_fd, size_t page_cnt,
                                         struct perf_event_attr *attr,
                                         perf_buffer_event_fn event_cb, void *ctx,
                                         const struct perf_buffer_raw_opts *opts)
{
        struct perf_buffer_params p = {};

        if (!attr)
                return libbpf_err_ptr(-EINVAL);

        if (!OPTS_VALID(opts, perf_buffer_raw_opts))
                return libbpf_err_ptr(-EINVAL);

        p.attr = attr;
        p.event_cb = event_cb;
        p.ctx = ctx;
        p.cpu_cnt = OPTS_GET(opts, cpu_cnt, 0);
        p.cpus = OPTS_GET(opts, cpus, NULL);
        p.map_keys = OPTS_GET(opts, map_keys, NULL);

        return libbpf_ptr(__perf_buffer__new(map_fd, page_cnt, &p));
}

static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
                                              struct perf_buffer_params *p)
{
        const char *online_cpus_file = "/sys/devices/system/cpu/online";
        struct bpf_map_info map;
        char msg[STRERR_BUFSIZE];
        struct perf_buffer *pb;
        bool *online = NULL;
        __u32 map_info_len;
        int err, i, j, n;

        if (page_cnt == 0 || (page_cnt & (page_cnt - 1))) {
                pr_warn("page count should be power of two, but is %zu\n",
                        page_cnt);
                return ERR_PTR(-EINVAL);
        }

        /* best-effort sanity checks */
        memset(&map, 0, sizeof(map));
        map_info_len = sizeof(map);
        err = bpf_map_get_info_by_fd(map_fd, &map, &map_info_len);
        if (err) {
                err = -errno;
                /* if BPF_OBJ_GET_INFO_BY_FD is supported, will return
                 * -EBADFD, -EFAULT, or -E2BIG on real error
                 */
                if (err != -EINVAL) {
                        pr_warn("failed to get map info for map FD %d: %s\n",
                                map_fd, libbpf_strerror_r(err, msg, sizeof(msg)));
                        return ERR_PTR(err);
                }
                pr_debug("failed to get map info for FD %d; API not supported? Ignoring...\n",
                         map_fd);
        } else {
                if (map.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) {
                        pr_warn("map '%s' should be BPF_MAP_TYPE_PERF_EVENT_ARRAY\n",
                                map.name);
                        return ERR_PTR(-EINVAL);
                }
        }

        pb = calloc(1, sizeof(*pb));
        if (!pb)
                return ERR_PTR(-ENOMEM);

        pb->event_cb = p->event_cb;
        pb->sample_cb = p->sample_cb;
        pb->lost_cb = p->lost_cb;
        pb->ctx = p->ctx;

        pb->page_size = getpagesize();
        pb->mmap_size = pb->page_size * page_cnt;
        pb->map_fd = map_fd;

        pb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
        if (pb->epoll_fd < 0) {
                err = -errno;
                pr_warn("failed to create epoll instance: %s\n",
                        libbpf_strerror_r(err, msg, sizeof(msg)));
                goto error;
        }

        if (p->cpu_cnt > 0) {
                pb->cpu_cnt = p->cpu_cnt;
        } else {
                pb->cpu_cnt = libbpf_num_possible_cpus();
                if (pb->cpu_cnt < 0) {
                        err = pb->cpu_cnt;
                        goto error;
                }
                if (map.max_entries && map.max_entries < pb->cpu_cnt)
                        pb->cpu_cnt = map.max_entries;
        }

        pb->events = calloc(pb->cpu_cnt, sizeof(*pb->events));
        if (!pb->events) {
                err = -ENOMEM;
                pr_warn("failed to allocate events: out of memory\n");
                goto error;
        }
        pb->cpu_bufs = calloc(pb->cpu_cnt, sizeof(*pb->cpu_bufs));
        if (!pb->cpu_bufs) {
                err = -ENOMEM;
                pr_warn("failed to allocate buffers: out of memory\n");
                goto error;
        }

        err = parse_cpu_mask_file(online_cpus_file, &online, &n);
        if (err) {
                pr_warn("failed to get online CPU mask: %d\n", err);
                goto error;
        }

        for (i = 0, j = 0; i < pb->cpu_cnt; i++) {
                struct perf_cpu_buf *cpu_buf;
                int cpu, map_key;

                cpu = p->cpu_cnt > 0 ? p->cpus[i] : i;
                map_key = p->cpu_cnt > 0 ? p->map_keys[i] : i;

                /* in case user didn't explicitly requested particular CPUs to
                 * be attached to, skip offline/not present CPUs
                 */
                if (p->cpu_cnt <= 0 && (cpu >= n || !online[cpu]))
                        continue;

                cpu_buf = perf_buffer__open_cpu_buf(pb, p->attr, cpu, map_key);
                if (IS_ERR(cpu_buf)) {
                        err = PTR_ERR(cpu_buf);
                        goto error;
                }

                pb->cpu_bufs[j] = cpu_buf;

                err = bpf_map_update_elem(pb->map_fd, &map_key,
                                          &cpu_buf->fd, 0);
                if (err) {
                        err = -errno;
                        pr_warn("failed to set cpu #%d, key %d -> perf FD %d: %s\n",
                                cpu, map_key, cpu_buf->fd,
                                libbpf_strerror_r(err, msg, sizeof(msg)));
                        goto error;
                }

                pb->events[j].events = EPOLLIN;
                pb->events[j].data.ptr = cpu_buf;
                if (epoll_ctl(pb->epoll_fd, EPOLL_CTL_ADD, cpu_buf->fd,
                              &pb->events[j]) < 0) {
                        err = -errno;
                        pr_warn("failed to epoll_ctl cpu #%d perf FD %d: %s\n",
                                cpu, cpu_buf->fd,
                                libbpf_strerror_r(err, msg, sizeof(msg)));
                        goto error;
                }
                j++;
        }
        pb->cpu_cnt = j;
        free(online);

        return pb;

error:
        free(online);
        if (pb)
                perf_buffer__free(pb);
        return ERR_PTR(err);
}

struct perf_sample_raw {
        struct perf_event_header header;
        uint32_t size;
        char data[];
};

struct perf_sample_lost {
        struct perf_event_header header;
        uint64_t id;
        uint64_t lost;
        uint64_t sample_id;
};

static enum bpf_perf_event_ret
perf_buffer__process_record(struct perf_event_header *e, void *ctx)
{
        struct perf_cpu_buf *cpu_buf = ctx;
        struct perf_buffer *pb = cpu_buf->pb;
        void *data = e;

        /* user wants full control over parsing perf event */
        if (pb->event_cb)
                return pb->event_cb(pb->ctx, cpu_buf->cpu, e);

        switch (e->type) {
        case PERF_RECORD_SAMPLE: {
                struct perf_sample_raw *s = data;

                if (pb->sample_cb)
                        pb->sample_cb(pb->ctx, cpu_buf->cpu, s->data, s->size);
                break;
        }
        case PERF_RECORD_LOST: {
                struct perf_sample_lost *s = data;

                if (pb->lost_cb)
                        pb->lost_cb(pb->ctx, cpu_buf->cpu, s->lost);
                break;
        }
        default:
                pr_warn("unknown perf sample type %d\n", e->type);
                return LIBBPF_PERF_EVENT_ERROR;
        }
        return LIBBPF_PERF_EVENT_CONT;
}

static int perf_buffer__process_records(struct perf_buffer *pb,
                                        struct perf_cpu_buf *cpu_buf)
{
        enum bpf_perf_event_ret ret;

        ret = perf_event_read_simple(cpu_buf->base, pb->mmap_size,
                                     pb->page_size, &cpu_buf->buf,
                                     &cpu_buf->buf_size,
                                     perf_buffer__process_record, cpu_buf);
        if (ret != LIBBPF_PERF_EVENT_CONT)
                return ret;
        return 0;
}

int perf_buffer__epoll_fd(const struct perf_buffer *pb)
{
        return pb->epoll_fd;
}

int perf_buffer__poll(struct perf_buffer *pb, int timeout_ms)
{
        int i, cnt, err;

        cnt = epoll_wait(pb->epoll_fd, pb->events, pb->cpu_cnt, timeout_ms);
        if (cnt < 0)
                return -errno;

        for (i = 0; i < cnt; i++) {
                struct perf_cpu_buf *cpu_buf = pb->events[i].data.ptr;

                err = perf_buffer__process_records(pb, cpu_buf);
                if (err) {
                        pr_warn("error while processing records: %d\n", err);
                        return libbpf_err(err);
                }
        }
        return cnt;
}

/* Return number of PERF_EVENT_ARRAY map slots set up by this perf_buffer
 * manager.
 */
size_t perf_buffer__buffer_cnt(const struct perf_buffer *pb)
{
        return pb->cpu_cnt;
}

/*
 * Return perf_event FD of a ring buffer in *buf_idx* slot of
 * PERF_EVENT_ARRAY BPF map. This FD can be polled for new data using
 * select()/poll()/epoll() Linux syscalls.
 */
int perf_buffer__buffer_fd(const struct perf_buffer *pb, size_t buf_idx)
{
        struct perf_cpu_buf *cpu_buf;

        if (buf_idx >= pb->cpu_cnt)
                return libbpf_err(-EINVAL);

        cpu_buf = pb->cpu_bufs[buf_idx];
        if (!cpu_buf)
                return libbpf_err(-ENOENT);

        return cpu_buf->fd;
}

int perf_buffer__buffer(struct perf_buffer *pb, int buf_idx, void **buf, size_t *buf_size)
{
        struct perf_cpu_buf *cpu_buf;

        if (buf_idx >= pb->cpu_cnt)
                return libbpf_err(-EINVAL);

        cpu_buf = pb->cpu_bufs[buf_idx];
        if (!cpu_buf)
                return libbpf_err(-ENOENT);

        *buf = cpu_buf->base;
        *buf_size = pb->mmap_size;
        return 0;
}

/*
 * Consume data from perf ring buffer corresponding to slot *buf_idx* in
 * PERF_EVENT_ARRAY BPF map without waiting/polling. If there is no data to
 * consume, do nothing and return success.
 * Returns:
 *   - 0 on success;
 *   - <0 on failure.
 */
int perf_buffer__consume_buffer(struct perf_buffer *pb, size_t buf_idx)
{
        struct perf_cpu_buf *cpu_buf;

        if (buf_idx >= pb->cpu_cnt)
                return libbpf_err(-EINVAL);

        cpu_buf = pb->cpu_bufs[buf_idx];
        if (!cpu_buf)
                return libbpf_err(-ENOENT);

        return perf_buffer__process_records(pb, cpu_buf);
}

int perf_buffer__consume(struct perf_buffer *pb)
{
        int i, err;

        for (i = 0; i < pb->cpu_cnt; i++) {
                struct perf_cpu_buf *cpu_buf = pb->cpu_bufs[i];

                if (!cpu_buf)
                        continue;

                err = perf_buffer__process_records(pb, cpu_buf);
                if (err) {
                        pr_warn("perf_buffer: failed to process records in buffer #%d: %d\n", i, err);
                        return libbpf_err(err);
                }
        }
        return 0;
}

int bpf_program__set_attach_target(struct bpf_program *prog,
                                   int attach_prog_fd,
                                   const char *attach_func_name)
{
        int btf_obj_fd = 0, btf_id = 0, err;

        if (!prog || attach_prog_fd < 0)
                return libbpf_err(-EINVAL);

        if (prog->obj->loaded)
                return libbpf_err(-EINVAL);

        if (attach_prog_fd && !attach_func_name) {
                /* remember attach_prog_fd and let bpf_program__load() find
                 * BTF ID during the program load
                 */
                prog->attach_prog_fd = attach_prog_fd;
                return 0;
        }

        if (attach_prog_fd) {
                btf_id = libbpf_find_prog_btf_id(attach_func_name,
                                                 attach_prog_fd);
                if (btf_id < 0)
                        return libbpf_err(btf_id);
        } else {
                if (!attach_func_name)
                        return libbpf_err(-EINVAL);

                /* load btf_vmlinux, if not yet */
                err = bpf_object__load_vmlinux_btf(prog->obj, true);
                if (err)
                        return libbpf_err(err);
                err = find_kernel_btf_id(prog->obj, attach_func_name,
                                         prog->expected_attach_type,
                                         &btf_obj_fd, &btf_id);
                if (err)
                        return libbpf_err(err);
        }

        prog->attach_btf_id = btf_id;
        prog->attach_btf_obj_fd = btf_obj_fd;
        prog->attach_prog_fd = attach_prog_fd;
        return 0;
}

int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
{
        int err = 0, n, len, start, end = -1;
        bool *tmp;

        *mask = NULL;
        *mask_sz = 0;

        /* Each sub string separated by ',' has format \d+-\d+ or \d+ */
        while (*s) {
                if (*s == ',' || *s == '\n') {
                        s++;
                        continue;
                }
                n = sscanf(s, "%d%n-%d%n", &start, &len, &end, &len);
                if (n <= 0 || n > 2) {
                        pr_warn("Failed to get CPU range %s: %d\n", s, n);
                        err = -EINVAL;
                        goto cleanup;
                } else if (n == 1) {
                        end = start;
                }
                if (start < 0 || start > end) {
                        pr_warn("Invalid CPU range [%d,%d] in %s\n",
                                start, end, s);
                        err = -EINVAL;
                        goto cleanup;
                }
                tmp = realloc(*mask, end + 1);
                if (!tmp) {
                        err = -ENOMEM;
                        goto cleanup;
                }
                *mask = tmp;
                memset(tmp + *mask_sz, 0, start - *mask_sz);
                memset(tmp + start, 1, end - start + 1);
                *mask_sz = end + 1;
                s += len;
        }
        if (!*mask_sz) {
                pr_warn("Empty CPU range\n");
                return -EINVAL;
        }
        return 0;
cleanup:
        free(*mask);
        *mask = NULL;
        return err;
}

int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz)
{
        int fd, err = 0, len;
        char buf[128];

        fd = open(fcpu, O_RDONLY | O_CLOEXEC);
        if (fd < 0) {
                err = -errno;
                pr_warn("Failed to open cpu mask file %s: %d\n", fcpu, err);
                return err;
        }
        len = read(fd, buf, sizeof(buf));
        close(fd);
        if (len <= 0) {
                err = len ? -errno : -EINVAL;
                pr_warn("Failed to read cpu mask from %s: %d\n", fcpu, err);
                return err;
        }
        if (len >= sizeof(buf)) {
                pr_warn("CPU mask is too big in file %s\n", fcpu);
                return -E2BIG;
        }
        buf[len] = '\0';

        return parse_cpu_mask_str(buf, mask, mask_sz);
}

int libbpf_num_possible_cpus(void)
{
        static const char *fcpu = "/sys/devices/system/cpu/possible";
        static int cpus;
        int err, n, i, tmp_cpus;
        bool *mask;

        tmp_cpus = READ_ONCE(cpus);
        if (tmp_cpus > 0)
                return tmp_cpus;

        err = parse_cpu_mask_file(fcpu, &mask, &n);
        if (err)
                return libbpf_err(err);

        tmp_cpus = 0;
        for (i = 0; i < n; i++) {
                if (mask[i])
                        tmp_cpus++;
        }
        free(mask);

        WRITE_ONCE(cpus, tmp_cpus);
        return tmp_cpus;
}

static int populate_skeleton_maps(const struct bpf_object *obj,
                                  struct bpf_map_skeleton *maps,
                                  size_t map_cnt)
{
        int i;

        for (i = 0; i < map_cnt; i++) {
                struct bpf_map **map = maps[i].map;
                const char *name = maps[i].name;
                void **mmaped = maps[i].mmaped;

                *map = bpf_object__find_map_by_name(obj, name);
                if (!*map) {
                        pr_warn("failed to find skeleton map '%s'\n", name);
                        return -ESRCH;
                }

                /* externs shouldn't be pre-setup from user code */
                if (mmaped && (*map)->libbpf_type != LIBBPF_MAP_KCONFIG)
                        *mmaped = (*map)->mmaped;
        }
        return 0;
}

static int populate_skeleton_progs(const struct bpf_object *obj,
                                   struct bpf_prog_skeleton *progs,
                                   size_t prog_cnt)
{
        int i;

        for (i = 0; i < prog_cnt; i++) {
                struct bpf_program **prog = progs[i].prog;
                const char *name = progs[i].name;

                *prog = bpf_object__find_program_by_name(obj, name);
                if (!*prog) {
                        pr_warn("failed to find skeleton program '%s'\n", name);
                        return -ESRCH;
                }
        }
        return 0;
}

int bpf_object__open_skeleton(struct bpf_object_skeleton *s,
                              const struct bpf_object_open_opts *opts)
{
        DECLARE_LIBBPF_OPTS(bpf_object_open_opts, skel_opts,
                .object_name = s->name,
        );
        struct bpf_object *obj;
        int err;

        /* Attempt to preserve opts->object_name, unless overriden by user
         * explicitly. Overwriting object name for skeletons is discouraged,
         * as it breaks global data maps, because they contain object name
         * prefix as their own map name prefix. When skeleton is generated,
         * bpftool is making an assumption that this name will stay the same.
         */
        if (opts) {
                memcpy(&skel_opts, opts, sizeof(*opts));
                if (!opts->object_name)
                        skel_opts.object_name = s->name;
        }

        obj = bpf_object__open_mem(s->data, s->data_sz, &skel_opts);
        err = libbpf_get_error(obj);
        if (err) {
                pr_warn("failed to initialize skeleton BPF object '%s': %d\n",
                        s->name, err);
                return libbpf_err(err);
        }

        *s->obj = obj;
        err = populate_skeleton_maps(obj, s->maps, s->map_cnt);
        if (err) {
                pr_warn("failed to populate skeleton maps for '%s': %d\n", s->name, err);
                return libbpf_err(err);
        }

        err = populate_skeleton_progs(obj, s->progs, s->prog_cnt);
        if (err) {
                pr_warn("failed to populate skeleton progs for '%s': %d\n", s->name, err);
                return libbpf_err(err);
        }

        return 0;
}

int bpf_object__open_subskeleton(struct bpf_object_subskeleton *s)
{
        int err, len, var_idx, i;
        const char *var_name;
        const struct bpf_map *map;
        struct btf *btf;
        __u32 map_type_id;
        const struct btf_type *map_type, *var_type;
        const struct bpf_var_skeleton *var_skel;
        struct btf_var_secinfo *var;

        if (!s->obj)
                return libbpf_err(-EINVAL);

        btf = bpf_object__btf(s->obj);
        if (!btf) {
                pr_warn("subskeletons require BTF at runtime (object %s)\n",
                        bpf_object__name(s->obj));
                return libbpf_err(-errno);
        }

        err = populate_skeleton_maps(s->obj, s->maps, s->map_cnt);
        if (err) {
                pr_warn("failed to populate subskeleton maps: %d\n", err);
                return libbpf_err(err);
        }

        err = populate_skeleton_progs(s->obj, s->progs, s->prog_cnt);
        if (err) {
                pr_warn("failed to populate subskeleton maps: %d\n", err);
                return libbpf_err(err);
        }

        for (var_idx = 0; var_idx < s->var_cnt; var_idx++) {
                var_skel = &s->vars[var_idx];
                map = *var_skel->map;
                map_type_id = bpf_map__btf_value_type_id(map);
                map_type = btf__type_by_id(btf, map_type_id);

                if (!btf_is_datasec(map_type)) {
                        pr_warn("type for map '%1$s' is not a datasec: %2$s",
                                bpf_map__name(map),
                                __btf_kind_str(btf_kind(map_type)));
                        return libbpf_err(-EINVAL);
                }

                len = btf_vlen(map_type);
                var = btf_var_secinfos(map_type);
                for (i = 0; i < len; i++, var++) {
                        var_type = btf__type_by_id(btf, var->type);
                        var_name = btf__name_by_offset(btf, var_type->name_off);
                        if (strcmp(var_name, var_skel->name) == 0) {
                                *var_skel->addr = map->mmaped + var->offset;
                                break;
                        }
                }
        }
        return 0;
}

void bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s)
{
        if (!s)
                return;
        free(s->maps);
        free(s->progs);
        free(s->vars);
        free(s);
}

int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
{
        int i, err;

        err = bpf_object__load(*s->obj);
        if (err) {
                pr_warn("failed to load BPF skeleton '%s': %d\n", s->name, err);
                return libbpf_err(err);
        }

        for (i = 0; i < s->map_cnt; i++) {
                struct bpf_map *map = *s->maps[i].map;
                size_t mmap_sz = bpf_map_mmap_sz(map);
                int prot, map_fd = bpf_map__fd(map);
                void **mmaped = s->maps[i].mmaped;

                if (!mmaped)
                        continue;

                if (!(map->def.map_flags & BPF_F_MMAPABLE)) {
                        *mmaped = NULL;
                        continue;
                }

                if (map->def.map_flags & BPF_F_RDONLY_PROG)
                        prot = PROT_READ;
                else
                        prot = PROT_READ | PROT_WRITE;

                /* Remap anonymous mmap()-ed "map initialization image" as
                 * a BPF map-backed mmap()-ed memory, but preserving the same
                 * memory address. This will cause kernel to change process'
                 * page table to point to a different piece of kernel memory,
                 * but from userspace point of view memory address (and its
                 * contents, being identical at this point) will stay the
                 * same. This mapping will be released by bpf_object__close()
                 * as per normal clean up procedure, so we don't need to worry
                 * about it from skeleton's clean up perspective.
                 */
                *mmaped = mmap(map->mmaped, mmap_sz, prot,
                                MAP_SHARED | MAP_FIXED, map_fd, 0);
                if (*mmaped == MAP_FAILED) {
                        err = -errno;
                        *mmaped = NULL;
                        pr_warn("failed to re-mmap() map '%s': %d\n",
                                 bpf_map__name(map), err);
                        return libbpf_err(err);
                }
        }

        return 0;
}

int bpf_object__attach_skeleton(struct bpf_object_skeleton *s)
{
        int i, err;

        for (i = 0; i < s->prog_cnt; i++) {
                struct bpf_program *prog = *s->progs[i].prog;
                struct bpf_link **link = s->progs[i].link;

                if (!prog->autoload || !prog->autoattach)
                        continue;

                /* auto-attaching not supported for this program */
                if (!prog->sec_def || !prog->sec_def->prog_attach_fn)
                        continue;

                /* if user already set the link manually, don't attempt auto-attach */
                if (*link)
                        continue;

                err = prog->sec_def->prog_attach_fn(prog, prog->sec_def->cookie, link);
                if (err) {
                        pr_warn("prog '%s': failed to auto-attach: %d\n",
                                bpf_program__name(prog), err);
                        return libbpf_err(err);
                }

                /* It's possible that for some SEC() definitions auto-attach
                 * is supported in some cases (e.g., if definition completely
                 * specifies target information), but is not in other cases.
                 * SEC("uprobe") is one such case. If user specified target
                 * binary and function name, such BPF program can be
                 * auto-attached. But if not, it shouldn't trigger skeleton's
                 * attach to fail. It should just be skipped.
                 * attach_fn signals such case with returning 0 (no error) and
                 * setting link to NULL.
                 */
        }

        return 0;
}

void bpf_object__detach_skeleton(struct bpf_object_skeleton *s)
{
        int i;

        for (i = 0; i < s->prog_cnt; i++) {
                struct bpf_link **link = s->progs[i].link;

                bpf_link__destroy(*link);
                *link = NULL;
        }
}

void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s)
{
        if (!s)
                return;

        if (s->progs)
                bpf_object__detach_skeleton(s);
        if (s->obj)
                bpf_object__close(*s->obj);
        free(s->maps);
        free(s->progs);
        free(s);
}