selftests/btf: add initial BTF dedup tests

This patch sets up a new kind of tests (BTF dedup tests) and tests few aspects of
BTF dedup algorithm. More complete set of tests will come in follow up patches.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/btf.c

@@ -237,6 +237,11 @@ static int btf_parse_type_sec(struct btf *btf)
 	return 0;
 }
 
+__u32 btf__get_nr_types(const struct btf *btf)
+{
+	return btf->nr_types;
+}
+
 const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
 {
 	if (type_id > btf->nr_types)
@@ -427,6 +432,13 @@ int btf__fd(const struct btf *btf)
 	return btf->fd;
 }
 
+void btf__get_strings(const struct btf *btf, const char **strings,
+		      __u32 *str_len)
+{
+	*strings = btf->strings;
+	*str_len = btf->hdr->str_len;
+}
+
 const char *btf__name_by_offset(const struct btf *btf, __u32 offset)
 {
 	if (offset < btf->hdr->str_len)

tools/lib/bpf/btf.h

@@ -59,11 +59,14 @@ LIBBPF_API void btf__free(struct btf *btf);
 LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size);
 LIBBPF_API __s32 btf__find_by_name(const struct btf *btf,
 				   const char *type_name);
+LIBBPF_API __u32 btf__get_nr_types(const struct btf *btf);
 LIBBPF_API const struct btf_type *btf__type_by_id(const struct btf *btf,
 						  __u32 id);
 LIBBPF_API __s64 btf__resolve_size(const struct btf *btf, __u32 type_id);
 LIBBPF_API int btf__resolve_type(const struct btf *btf, __u32 type_id);
 LIBBPF_API int btf__fd(const struct btf *btf);
+LIBBPF_API void btf__get_strings(const struct btf *btf, const char **strings,
+				 __u32 *str_len);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
 LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, char *map_name,

tools/lib/bpf/libbpf.map

@@ -135,6 +135,8 @@ LIBBPF_0.0.2 {
 		bpf_get_link_xdp_id;
 		btf__dedup;
 		btf__get_map_kv_tids;
+		btf__get_nr_types;
+		btf__get_strings;
 		btf_ext__free;
 		btf_ext__func_info_rec_size;
 		btf_ext__line_info_rec_size;