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libbpf: Add btf__new_empty() to create an empty BTF object

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Add an ability to create an empty BTF object from scratch. This is going to be
used by pahole for BTF encoding. And also by selftest for convenient creation
of BTF objects.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200926011357.2366158-7-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-09-25 18:13:54 -07:00 committed by Alexei Starovoitov
parent 919d2b1dbb
commit a871b04310
3 changed files with 32 additions and 0 deletions
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30
tools/lib/bpf/btf.c
View File

@ -565,6 +565,36 @@ void btf__free(struct btf *btf)
free(btf);
}
struct btf *btf__new_empty(void)
{
struct btf *btf;
btf = calloc(1, sizeof(*btf));
if (!btf)
return ERR_PTR(-ENOMEM);
btf->fd = -1;
btf->ptr_sz = sizeof(void *);
/* +1 for empty string at offset 0 */
btf->raw_size = sizeof(struct btf_header) + 1;
btf->raw_data = calloc(1, btf->raw_size);
if (!btf->raw_data) {
free(btf);
return ERR_PTR(-ENOMEM);
}
btf->hdr = btf->raw_data;
btf->hdr->hdr_len = sizeof(struct btf_header);
btf->hdr->magic = BTF_MAGIC;
btf->hdr->version = BTF_VERSION;
btf->types_data = btf->raw_data + btf->hdr->hdr_len;
btf->strs_data = btf->raw_data + btf->hdr->hdr_len;
btf->hdr->str_len = 1; /* empty string at offset 0 */
return btf;
}
struct btf *btf__new(const void *data, __u32 size)
{
struct btf *btf;

1
tools/lib/bpf/btf.h
View File

@ -27,6 +27,7 @@ struct bpf_object;
LIBBPF_API void btf__free(struct btf *btf);
LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
LIBBPF_API struct btf *btf__new_empty(void);
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);

1
tools/lib/bpf/libbpf.map
View File

@ -307,6 +307,7 @@ LIBBPF_0.2.0 {
bpf_program__section_name;
btf__add_str;
btf__find_str;
btf__new_empty;
perf_buffer__buffer_cnt;
perf_buffer__buffer_fd;
perf_buffer__epoll_fd;