libbpf: Introduce bpf_{btf,link,map,prog}_get_info_by_fd()

These are type-safe wrappers around bpf_obj_get_info_by_fd(). They
found one problem in selftests, and are also useful for adding
Memory Sanitizer annotations.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230214231221.249277-2-iii@linux.ibm.com

tools/lib/bpf/bpf.c

@@ -1044,6 +1044,26 @@ int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len)
 	return libbpf_err_errno(err);
 }
 
+int bpf_prog_get_info_by_fd(int prog_fd, struct bpf_prog_info *info, __u32 *info_len)
+{
+	return bpf_obj_get_info_by_fd(prog_fd, info, info_len);
+}
+
+int bpf_map_get_info_by_fd(int map_fd, struct bpf_map_info *info, __u32 *info_len)
+{
+	return bpf_obj_get_info_by_fd(map_fd, info, info_len);
+}
+
+int bpf_btf_get_info_by_fd(int btf_fd, struct bpf_btf_info *info, __u32 *info_len)
+{
+	return bpf_obj_get_info_by_fd(btf_fd, info, info_len);
+}
+
+int bpf_link_get_info_by_fd(int link_fd, struct bpf_link_info *info, __u32 *info_len)
+{
+	return bpf_obj_get_info_by_fd(link_fd, info, info_len);
+}
+
 int bpf_raw_tracepoint_open(const char *name, int prog_fd)
 {
 	const size_t attr_sz = offsetofend(union bpf_attr, raw_tracepoint);

tools/lib/bpf/bpf.h

@@ -386,6 +386,15 @@ LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_link_get_fd_by_id_opts(__u32 id,
 				const struct bpf_get_fd_by_id_opts *opts);
 LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len);
+/* Type-safe variants of bpf_obj_get_info_by_fd(). The callers still needs to
+ * pass info_len, which should normally be
+ * sizeof(struct bpf_{prog,map,btf,link}_info), in order to be compatible with
+ * different libbpf and kernel versions.
+ */
+LIBBPF_API int bpf_prog_get_info_by_fd(int prog_fd, struct bpf_prog_info *info, __u32 *info_len);
+LIBBPF_API int bpf_map_get_info_by_fd(int map_fd, struct bpf_map_info *info, __u32 *info_len);
+LIBBPF_API int bpf_btf_get_info_by_fd(int btf_fd, struct bpf_btf_info *info, __u32 *info_len);
+LIBBPF_API int bpf_link_get_info_by_fd(int link_fd, struct bpf_link_info *info, __u32 *info_len);
 
 struct bpf_prog_query_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */

tools/lib/bpf/libbpf.map

@@ -384,4 +384,9 @@ LIBBPF_1.1.0 {
 } LIBBPF_1.0.0;
 
 LIBBPF_1.2.0 {
+	global:
+		bpf_btf_get_info_by_fd;
+		bpf_link_get_info_by_fd;
+		bpf_map_get_info_by_fd;
+		bpf_prog_get_info_by_fd;
 } LIBBPF_1.1.0;