perf bpf: Synthesize bpf events with bpf_program__get_prog_info_linear()

With bpf_program__get_prog_info_linear, we can simplify the logic that
synthesizes bpf events.

This patch doesn't change the behavior of the code.

Commiter notes:

Needed this (for all four variables), suggested by Song, to overcome
build failure on debian experimental cross building to MIPS 32-bit:

  -               u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
  +               u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(uintptr_t)(info->prog_tags);

  util/bpf-event.c: In function 'perf_event__synthesize_one_bpf_prog':
  util/bpf-event.c:143:35: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
                                     ^
  util/bpf-event.c:144:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     __u32 *prog_lens = (__u32 *)(info->jited_func_lens);
                        ^
  util/bpf-event.c:145:23: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     __u64 *prog_addrs = (__u64 *)(info->jited_ksyms);
                         ^
  util/bpf-event.c:146:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
     void *func_infos = (void *)(info->func_info);
                        ^
  cc1: all warnings being treated as errors

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: kernel-team@fb.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Fomichev <sdf@google.com>
Link: http://lkml.kernel.org/r/20190312053051.2690567-5-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
index ea012b7..e0cbe7f 100644 (file)
--- a/tools/perf/util/bpf-event.c
+++ b/tools/perf/util/bpf-event.c
@@ -3,7 +3,9 @@
 #include <stdlib.h>
 #include <bpf/bpf.h>
 #include <bpf/btf.h>
+#include <bpf/libbpf.h>
 #include <linux/btf.h>
+#include <linux/err.h>
 #include "bpf-event.h"
 #include "debug.h"
 #include "symbol.h"
@@ -49,99 +51,62 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_tool *tool,
 {
        struct ksymbol_event *ksymbol_event = &event->ksymbol_event;
        struct bpf_event *bpf_event = &event->bpf_event;
-       u32 sub_prog_cnt, i, func_info_rec_size = 0;
-       u8 (*prog_tags)[BPF_TAG_SIZE] = NULL;
-       struct bpf_prog_info info = { .type = 0, };
-       u32 info_len = sizeof(info);
-       void *func_infos = NULL;
-       u64 *prog_addrs = NULL;
+       struct bpf_prog_info_linear *info_linear;
+       struct bpf_prog_info *info;
        struct btf *btf = NULL;
-       u32 *prog_lens = NULL;
        bool has_btf = false;
-       char errbuf[512];
+       u32 sub_prog_cnt, i;
        int err = 0;
+       u64 arrays;
 
-       /* Call bpf_obj_get_info_by_fd() to get sizes of arrays */
-       err = bpf_obj_get_info_by_fd(fd, &info, &info_len);
+       arrays = 1UL << BPF_PROG_INFO_JITED_KSYMS;
+       arrays |= 1UL << BPF_PROG_INFO_JITED_FUNC_LENS;
+       arrays |= 1UL << BPF_PROG_INFO_FUNC_INFO;
+       arrays |= 1UL << BPF_PROG_INFO_PROG_TAGS;
 
-       if (err) {
-               pr_debug("%s: failed to get BPF program info: %s, aborting\n",
-                        __func__, str_error_r(errno, errbuf, sizeof(errbuf)));
+       info_linear = bpf_program__get_prog_info_linear(fd, arrays);
+       if (IS_ERR_OR_NULL(info_linear)) {
+               info_linear = NULL;
+               pr_debug("%s: failed to get BPF program info. aborting\n", __func__);
                return -1;
        }
-       if (info_len < offsetof(struct bpf_prog_info, prog_tags)) {
+
+       if (info_linear->info_len < offsetof(struct bpf_prog_info, prog_tags)) {
                pr_debug("%s: the kernel is too old, aborting\n", __func__);
                return -2;
        }
 
+       info = &info_linear->info;
+
        /* number of ksyms, func_lengths, and tags should match */
-       sub_prog_cnt = info.nr_jited_ksyms;
-       if (sub_prog_cnt != info.nr_prog_tags ||
-           sub_prog_cnt != info.nr_jited_func_lens)
+       sub_prog_cnt = info->nr_jited_ksyms;
+       if (sub_prog_cnt != info->nr_prog_tags ||
+           sub_prog_cnt != info->nr_jited_func_lens)
                return -1;
 
        /* check BTF func info support */
-       if (info.btf_id && info.nr_func_info && info.func_info_rec_size) {
+       if (info->btf_id && info->nr_func_info && info->func_info_rec_size) {
                /* btf func info number should be same as sub_prog_cnt */
-               if (sub_prog_cnt != info.nr_func_info) {
+               if (sub_prog_cnt != info->nr_func_info) {
                        pr_debug("%s: mismatch in BPF sub program count and BTF function info count, aborting\n", __func__);
-                       return -1;
-               }
-               if (btf__get_from_id(info.btf_id, &btf)) {
-                       pr_debug("%s: failed to get BTF of id %u, aborting\n", __func__, info.btf_id);
-                       return -1;
+                       err = -1;
+                       goto out;
                }
-               func_info_rec_size = info.func_info_rec_size;
-               func_infos = calloc(sub_prog_cnt, func_info_rec_size);
-               if (!func_infos) {
-                       pr_debug("%s: failed to allocate memory for func_infos, aborting\n", __func__);
-                       return -1;
+               if (btf__get_from_id(info->btf_id, &btf)) {
+                       pr_debug("%s: failed to get BTF of id %u, aborting\n", __func__, info->btf_id);
+                       err = -1;
+                       btf = NULL;
+                       goto out;
                }
                has_btf = true;
        }
 
-       /*
-        * We need address, length, and tag for each sub program.
-        * Allocate memory and call bpf_obj_get_info_by_fd() again
-        */
-       prog_addrs = calloc(sub_prog_cnt, sizeof(u64));
-       if (!prog_addrs) {
-               pr_debug("%s: failed to allocate memory for prog_addrs, aborting\n", __func__);
-               goto out;
-       }
-       prog_lens = calloc(sub_prog_cnt, sizeof(u32));
-       if (!prog_lens) {
-               pr_debug("%s: failed to allocate memory for prog_lens, aborting\n", __func__);
-               goto out;
-       }
-       prog_tags = calloc(sub_prog_cnt, BPF_TAG_SIZE);
-       if (!prog_tags) {
-               pr_debug("%s: failed to allocate memory for prog_tags, aborting\n", __func__);
-               goto out;
-       }
-
-       memset(&info, 0, sizeof(info));
-       info.nr_jited_ksyms = sub_prog_cnt;
-       info.nr_jited_func_lens = sub_prog_cnt;
-       info.nr_prog_tags = sub_prog_cnt;
-       info.jited_ksyms = ptr_to_u64(prog_addrs);
-       info.jited_func_lens = ptr_to_u64(prog_lens);
-       info.prog_tags = ptr_to_u64(prog_tags);
-       info_len = sizeof(info);
-       if (has_btf) {
-               info.nr_func_info = sub_prog_cnt;
-               info.func_info_rec_size = func_info_rec_size;
-               info.func_info = ptr_to_u64(func_infos);
-       }
-
-       err = bpf_obj_get_info_by_fd(fd, &info, &info_len);
-       if (err) {
-               pr_debug("%s: failed to get BPF program info, aborting\n", __func__);
-               goto out;
-       }
-
        /* Synthesize PERF_RECORD_KSYMBOL */
        for (i = 0; i < sub_prog_cnt; i++) {
+               u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(uintptr_t)(info->prog_tags);
+               __u32 *prog_lens  = (__u32 *)(uintptr_t)(info->jited_func_lens);
+               __u64 *prog_addrs = (__u64 *)(uintptr_t)(info->jited_ksyms);
+               void *func_infos  = (void *)(uintptr_t)(info->func_info);
                const struct bpf_func_info *finfo;
                const char *short_name = NULL;
                const struct btf_type *t;
@@ -163,13 +128,13 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_tool *tool,
                                         KSYM_NAME_LEN - name_len,
                                         prog_tags[i], BPF_TAG_SIZE);
                if (has_btf) {
-                       finfo = func_infos + i * info.func_info_rec_size;
+                       finfo = func_infos + i * info->func_info_rec_size;
                        t = btf__type_by_id(btf, finfo->type_id);
                        short_name = btf__name_by_offset(btf, t->name_off);
                } else if (i == 0 && sub_prog_cnt == 1) {
                        /* no subprog */
-                       if (info.name[0])
-                               short_name = info.name;
+                       if (info->name[0])
+                               short_name = info->name;
                } else
                        short_name = "F";
                if (short_name)
@@ -195,9 +160,9 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_tool *tool,
                        },
                        .type = PERF_BPF_EVENT_PROG_LOAD,
                        .flags = 0,
-                       .id = info.id,
+                       .id = info->id,
                };
-               memcpy(bpf_event->tag, prog_tags[i], BPF_TAG_SIZE);
+               memcpy(bpf_event->tag, info->tag, BPF_TAG_SIZE);
                memset((void *)event + event->header.size, 0, machine->id_hdr_size);
                event->header.size += machine->id_hdr_size;
                err = perf_tool__process_synth_event(tool, event,
@@ -205,10 +170,7 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_tool *tool,
        }
 
 out:
-       free(prog_tags);
-       free(prog_lens);
-       free(prog_addrs);
-       free(func_infos);
+       free(info_linear);
        free(btf);
        return err ? -1 : 0;
 }