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libbpf: Add btf__parse_raw() and generic btf__parse() APIs 

Add public APIs to parse BTF from raw data file (e.g.,
/sys/kernel/btf/vmlinux), as well as generic btf__parse(), which will try to
determine correct format, currently either raw or ELF.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200802013219.864880-2-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-08-01 18:32:17 -07:00 committed by Daniel Borkmann
parent 041549b7b2
commit 94a1fedd63
3 changed files with 83 additions and 38 deletions
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114
tools/lib/bpf/btf.c
View File

@ -562,6 +562,83 @@ done:
return btf;
}
struct btf *btf__parse_raw(const char *path)
{
void *data = NULL;
struct btf *btf;
FILE *f = NULL;
__u16 magic;
int err = 0;
long sz;
f = fopen(path, "rb");
if (!f) {
err = -errno;
goto err_out;
}
/* check BTF magic */
if (fread(&magic, 1, sizeof(magic), f) < sizeof(magic)) {
err = -EIO;
goto err_out;
}
if (magic != BTF_MAGIC) {
/* definitely not a raw BTF */
err = -EPROTO;
goto err_out;
}
/* get file size */
if (fseek(f, 0, SEEK_END)) {
err = -errno;
goto err_out;
}
sz = ftell(f);
if (sz < 0) {
err = -errno;
goto err_out;
}
/* rewind to the start */
if (fseek(f, 0, SEEK_SET)) {
err = -errno;
goto err_out;
}
/* pre-alloc memory and read all of BTF data */
data = malloc(sz);
if (!data) {
err = -ENOMEM;
goto err_out;
}
if (fread(data, 1, sz, f) < sz) {
err = -EIO;
goto err_out;
}
/* finally parse BTF data */
btf = btf__new(data, sz);
err_out:
free(data);
if (f)
fclose(f);
return err ? ERR_PTR(err) : btf;
}
struct btf *btf__parse(const char *path, struct btf_ext **btf_ext)
{
struct btf *btf;
if (btf_ext)
*btf_ext = NULL;
btf = btf__parse_raw(path);
if (!IS_ERR(btf) || PTR_ERR(btf) != -EPROTO)
return btf;
return btf__parse_elf(path, btf_ext);
}
static int compare_vsi_off(const void *_a, const void *_b)
{
const struct btf_var_secinfo *a = _a;
@ -2951,41 +3028,6 @@ 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.
@ -3021,7 +3063,7 @@ struct btf *libbpf_find_kernel_btf(void)
continue;
if (locations[i].raw_btf)
btf = btf_load_raw(path);
btf = btf__parse_raw(path);
else
btf = btf__parse_elf(path, NULL);

5
tools/lib/bpf/btf.h
View File

@ -64,8 +64,9 @@ struct btf_ext_header {
LIBBPF_API void btf__free(struct btf *btf);
LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
LIBBPF_API struct btf *btf__parse_elf(const char *path,
struct btf_ext **btf_ext);
LIBBPF_API struct btf *btf__parse(const char *path, struct btf_ext **btf_ext);
LIBBPF_API struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext);
LIBBPF_API struct btf *btf__parse_raw(const char *path);
LIBBPF_API int btf__finalize_data(struct bpf_object *obj, struct btf *btf);
LIBBPF_API int btf__load(struct btf *btf);
LIBBPF_API __s32 btf__find_by_name(const struct btf *btf,

2
tools/lib/bpf/libbpf.map
View File

@ -293,5 +293,7 @@ LIBBPF_0.1.0 {
bpf_program__is_sk_lookup;
bpf_program__set_autoload;
bpf_program__set_sk_lookup;
btf__parse;
btf__parse_raw;
btf__set_fd;
} LIBBPF_0.0.9;