libbpf: Add getters for BTF.ext func and line info

Introducing new libbpf API getters for BTF.ext func and line info,
namely:
bpf_program__func_info
bpf_program__func_info_cnt
bpf_program__line_info
bpf_program__line_info_cnt

This change enables scenarios, when user needs to load bpf_program
directly using `bpf_prog_load`, instead of higher-level
`bpf_object__load`. Line and func info are required for checking BTF
info in verifier; verification may fail without these fields if, for
example, program calls `bpf_obj_new`.

Signed-off-by: Mykyta Yatsenko <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/lib/bpf/libbpf.c

···
 	return 0;
 }
 
+struct bpf_func_info *bpf_program__func_info(const struct bpf_program *prog)
+{
+	if (prog->func_info_rec_size != sizeof(struct bpf_func_info))
+		return libbpf_err_ptr(-EOPNOTSUPP);
+	return prog->func_info;
+}
+
+__u32 bpf_program__func_info_cnt(const struct bpf_program *prog)
+{
+	return prog->func_info_cnt;
+}
+
+struct bpf_line_info *bpf_program__line_info(const struct bpf_program *prog)
+{
+	if (prog->line_info_rec_size != sizeof(struct bpf_line_info))
+		return libbpf_err_ptr(-EOPNOTSUPP);
+	return prog->line_info;
+}
+
+__u32 bpf_program__line_info_cnt(const struct bpf_program *prog)
+{
+	return prog->line_info_cnt;
+}
+
 #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {			    \
 	.sec = (char *)sec_pfx,						    \
 	.prog_type = BPF_PROG_TYPE_##ptype,				    \

tools/lib/bpf/libbpf.h

···
 LIBBPF_API const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size);
 LIBBPF_API int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log_size);
 
+LIBBPF_API struct bpf_func_info *bpf_program__func_info(const struct bpf_program *prog);
+LIBBPF_API __u32 bpf_program__func_info_cnt(const struct bpf_program *prog);
+
+LIBBPF_API struct bpf_line_info *bpf_program__line_info(const struct bpf_program *prog);
+LIBBPF_API __u32 bpf_program__line_info_cnt(const struct bpf_program *prog);
+
 /**
  * @brief **bpf_program__set_attach_target()** sets BTF-based attach target
  * for supported BPF program types:

tools/lib/bpf/libbpf.map

···
 		bpf_linker__add_fd;
 		bpf_linker__new_fd;
 		bpf_object__prepare;
+		bpf_program__func_info;
+		bpf_program__func_info_cnt;
+		bpf_program__line_info;
+		bpf_program__line_info_cnt;
 		btf__add_decl_attr;
 		btf__add_type_attr;
 } LIBBPF_1.5.0;