libbpf: Expose bpf_find_kernel_btf as a LIBBPF_API

This patch exposes bpf_find_kernel_btf() as a LIBBPF_API.
It will be used in 'bpftool map dump' in a following patch
to dump a map with btf_vmlinux_value_type_id set.

bpf_find_kernel_btf() is renamed to libbpf_find_kernel_btf()
and moved to btf.c.  As <linux/kernel.h> is included,
some of the max/min type casting needs to be fixed.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200115230031.1102305-1-kafai@fb.com

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index cfeb6a4..3d1c25f 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -8,6 +8,10 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
+#include <sys/utsname.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <linux/kernel.h>
 #include <linux/err.h>
 #include <linux/btf.h>
 #include <gelf.h>
@@ -20,8 +24,8 @@
 /* make sure libbpf doesn't use kernel-only integer typedefs */
 #pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
 
-#define BTF_MAX_NR_TYPES 0x7fffffff
-#define BTF_MAX_STR_OFFSET 0x7fffffff
+#define BTF_MAX_NR_TYPES 0x7fffffffU
+#define BTF_MAX_STR_OFFSET 0x7fffffffU
 
 static struct btf_type btf_void;
 
@@ -53,7 +57,7 @@ static int btf_add_type(struct btf *btf, struct btf_type *t)
                if (btf->types_size == BTF_MAX_NR_TYPES)
                        return -E2BIG;
 
-               expand_by = max(btf->types_size >> 2, 16);
+               expand_by = max(btf->types_size >> 2, 16U);
                new_size = min(BTF_MAX_NR_TYPES, btf->types_size + expand_by);
 
                new_types = realloc(btf->types, sizeof(*new_types) * new_size);
@@ -289,7 +293,7 @@ int btf__align_of(const struct btf *btf, __u32 id)
        switch (kind) {
        case BTF_KIND_INT:
        case BTF_KIND_ENUM:
-               return min(sizeof(void *), t->size);
+               return min(sizeof(void *), (size_t)t->size);
        case BTF_KIND_PTR:
                return sizeof(void *);
        case BTF_KIND_TYPEDEF:
@@ -1401,7 +1405,7 @@ static int btf_dedup_hypot_map_add(struct btf_dedup *d,
        if (d->hypot_cnt == d->hypot_cap) {
                __u32 *new_list;
 
-               d->hypot_cap += max(16, d->hypot_cap / 2);
+               d->hypot_cap += max((size_t)16, d->hypot_cap / 2);
                new_list = realloc(d->hypot_list, sizeof(__u32) * d->hypot_cap);
                if (!new_list)
                        return -ENOMEM;
@@ -1697,7 +1701,7 @@ static int btf_dedup_strings(struct btf_dedup *d)
                if (strs.cnt + 1 > strs.cap) {
                        struct btf_str_ptr *new_ptrs;
 
-                       strs.cap += max(strs.cnt / 2, 16);
+                       strs.cap += max(strs.cnt / 2, 16U);
                        new_ptrs = realloc(strs.ptrs,
                                           sizeof(strs.ptrs[0]) * strs.cap);
                        if (!new_ptrs) {
@@ -2931,3 +2935,89 @@ static int btf_dedup_remap_types(struct btf_dedup *d)
        }
        return 0;
 }
+
+static struct btf *btf_load_raw(const char *path)
+{
+       struct btf *btf;
+       size_t read_cnt;
+       struct stat st;
+       void *data;
+       FILE *f;
+
+       if (stat(path, &st))
+               return ERR_PTR(-errno);
+
+       data = malloc(st.st_size);
+       if (!data)
+               return ERR_PTR(-ENOMEM);
+
+       f = fopen(path, "rb");
+       if (!f) {
+               btf = ERR_PTR(-errno);
+               goto cleanup;
+       }
+
+       read_cnt = fread(data, 1, st.st_size, f);
+       fclose(f);
+       if (read_cnt < st.st_size) {
+               btf = ERR_PTR(-EBADF);
+               goto cleanup;
+       }
+
+       btf = btf__new(data, read_cnt);
+
+cleanup:
+       free(data);
+       return btf;
+}
+
+/*
+ * Probe few well-known locations for vmlinux kernel image and try to load BTF
+ * data out of it to use for target BTF.
+ */
+struct btf *libbpf_find_kernel_btf(void)
+{
+       struct {
+               const char *path_fmt;
+               bool raw_btf;
+       } locations[] = {
+               /* try canonical vmlinux BTF through sysfs first */
+               { "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
+               /* fall back to trying to find vmlinux ELF on disk otherwise */
+               { "/boot/vmlinux-%1$s" },
+               { "/lib/modules/%1$s/vmlinux-%1$s" },
+               { "/lib/modules/%1$s/build/vmlinux" },
+               { "/usr/lib/modules/%1$s/kernel/vmlinux" },
+               { "/usr/lib/debug/boot/vmlinux-%1$s" },
+               { "/usr/lib/debug/boot/vmlinux-%1$s.debug" },
+               { "/usr/lib/debug/lib/modules/%1$s/vmlinux" },
+       };
+       char path[PATH_MAX + 1];
+       struct utsname buf;
+       struct btf *btf;
+       int i;
+
+       uname(&buf);
+
+       for (i = 0; i < ARRAY_SIZE(locations); i++) {
+               snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release);
+
+               if (access(path, R_OK))
+                       continue;
+
+               if (locations[i].raw_btf)
+                       btf = btf_load_raw(path);
+               else
+                       btf = btf__parse_elf(path, NULL);
+
+               pr_debug("loading kernel BTF '%s': %ld\n",
+                        path, IS_ERR(btf) ? PTR_ERR(btf) : 0);
+               if (IS_ERR(btf))
+                       continue;
+
+               return btf;
+       }
+
+       pr_warn("failed to find valid kernel BTF\n");
+       return ERR_PTR(-ESRCH);
+}

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 8d73f7f..70c1b7e 100644 (file)
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -102,6 +102,8 @@ LIBBPF_API int btf_ext__reloc_line_info(const struct btf *btf,
 LIBBPF_API __u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext);
 LIBBPF_API __u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext);
 
+LIBBPF_API struct btf *libbpf_find_kernel_btf(void);
+
 struct btf_dedup_opts {
        unsigned int dedup_table_size;
        bool dont_resolve_fwds;

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2386888..3afaca9 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -73,7 +73,6 @@
 
 #define __printf(a, b) __attribute__((format(printf, a, b)))
 
-static struct btf *bpf_find_kernel_btf(void);
 static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
 static struct bpf_program *bpf_object__find_prog_by_idx(struct bpf_object *obj,
                                                        int idx);
@@ -848,7 +847,7 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
                        continue;
 
                if (!kern_btf) {
-                       kern_btf = bpf_find_kernel_btf();
+                       kern_btf = libbpf_find_kernel_btf();
                        if (IS_ERR(kern_btf))
                                return PTR_ERR(kern_btf);
                }
@@ -4300,92 +4299,6 @@ static int bpf_core_reloc_insn(struct bpf_program *prog,
        return 0;
 }
 
-static struct btf *btf_load_raw(const char *path)
-{
-       struct btf *btf;
-       size_t read_cnt;
-       struct stat st;
-       void *data;
-       FILE *f;
-
-       if (stat(path, &st))
-               return ERR_PTR(-errno);
-
-       data = malloc(st.st_size);
-       if (!data)
-               return ERR_PTR(-ENOMEM);
-
-       f = fopen(path, "rb");
-       if (!f) {
-               btf = ERR_PTR(-errno);
-               goto cleanup;
-       }
-
-       read_cnt = fread(data, 1, st.st_size, f);
-       fclose(f);
-       if (read_cnt < st.st_size) {
-               btf = ERR_PTR(-EBADF);
-               goto cleanup;
-       }
-
-       btf = btf__new(data, read_cnt);
-
-cleanup:
-       free(data);
-       return btf;
-}
-
-/*
- * Probe few well-known locations for vmlinux kernel image and try to load BTF
- * data out of it to use for target BTF.
- */
-static struct btf *bpf_find_kernel_btf(void)
-{
-       struct {
-               const char *path_fmt;
-               bool raw_btf;
-       } locations[] = {
-               /* try canonical vmlinux BTF through sysfs first */
-               { "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
-               /* fall back to trying to find vmlinux ELF on disk otherwise */
-               { "/boot/vmlinux-%1$s" },
-               { "/lib/modules/%1$s/vmlinux-%1$s" },
-               { "/lib/modules/%1$s/build/vmlinux" },
-               { "/usr/lib/modules/%1$s/kernel/vmlinux" },
-               { "/usr/lib/debug/boot/vmlinux-%1$s" },
-               { "/usr/lib/debug/boot/vmlinux-%1$s.debug" },
-               { "/usr/lib/debug/lib/modules/%1$s/vmlinux" },
-       };
-       char path[PATH_MAX + 1];
-       struct utsname buf;
-       struct btf *btf;
-       int i;
-
-       uname(&buf);
-
-       for (i = 0; i < ARRAY_SIZE(locations); i++) {
-               snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release);
-
-               if (access(path, R_OK))
-                       continue;
-
-               if (locations[i].raw_btf)
-                       btf = btf_load_raw(path);
-               else
-                       btf = btf__parse_elf(path, NULL);
-
-               pr_debug("loading kernel BTF '%s': %ld\n",
-                        path, IS_ERR(btf) ? PTR_ERR(btf) : 0);
-               if (IS_ERR(btf))
-                       continue;
-
-               return btf;
-       }
-
-       pr_warn("failed to find valid kernel BTF\n");
-       return ERR_PTR(-ESRCH);
-}
-
 /* Output spec definition in the format:
  * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
  * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
@@ -4620,7 +4533,7 @@ bpf_core_reloc_fields(struct bpf_object *obj, const char *targ_btf_path)
        if (targ_btf_path)
                targ_btf = btf__parse_elf(targ_btf_path, NULL);
        else
-               targ_btf = bpf_find_kernel_btf();
+               targ_btf = libbpf_find_kernel_btf();
        if (IS_ERR(targ_btf)) {
                pr_warn("failed to get target BTF: %ld\n", PTR_ERR(targ_btf));
                return PTR_ERR(targ_btf);
@@ -6595,7 +6508,7 @@ invalid_prog:
 int libbpf_find_vmlinux_btf_id(const char *name,
                               enum bpf_attach_type attach_type)
 {
-       struct btf *btf = bpf_find_kernel_btf();
+       struct btf *btf = libbpf_find_kernel_btf();
        char raw_tp_btf[128] = BTF_PREFIX;
        char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;
        const char *btf_name;

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 1902a0f..64ec71b 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -231,4 +231,5 @@ LIBBPF_0.0.7 {
                bpf_program__is_struct_ops;
                bpf_program__set_struct_ops;
                btf__align_of;
+               libbpf_find_kernel_btf;
 } LIBBPF_0.0.6;