Commit 4cf23a3c authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

libbpf: Fix bpf_prog_load() log_buf logic for log_level 0 



To unify libbpf APIs behavior w.r.t. log_buf and log_level, fix
bpf_prog_load() to follow the same logic as bpf_btf_load() and
high-level bpf_object__load() API will follow in the subsequent patches:
  - if log_level is 0 and non-NULL log_buf is provided by a user, attempt
    load operation initially with no log_buf and log_level set;
  - if successful, we are done, return new FD;
  - on error, retry the load operation with log_level bumped to 1 and
    log_buf set; this way verbose logging will be requested only when we
    are sure that there is a failure, but will be fast in the
    common/expected success case.

Of course, user can still specify log_level > 0 from the very beginning
to force log collection.

Suggested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211209193840.1248570-2-andrii@kernel.org
parent ac55b3f0

tools/lib/bpf/bpf.c

+16 −13
Original line number Diff line number Diff line
@@ -303,10 +303,6 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type, 
	if (log_level && !log_buf)

		return libbpf_err(-EINVAL);



	attr.log_level = log_level;

	attr.log_buf = ptr_to_u64(log_buf);

	attr.log_size = log_size;



	func_info_rec_size = OPTS_GET(opts, func_info_rec_size, 0);

	func_info = OPTS_GET(opts, func_info, NULL);

	attr.func_info_rec_size = func_info_rec_size;
@@ -321,6 +317,12 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type, 


	attr.fd_array = ptr_to_u64(OPTS_GET(opts, fd_array, NULL));



	if (log_level) {

		attr.log_buf = ptr_to_u64(log_buf);

		attr.log_size = log_size;

		attr.log_level = log_level;

	}



	fd = sys_bpf_prog_load(&attr, sizeof(attr), attempts);

	if (fd >= 0)

		return fd;
@@ -366,16 +368,17 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type, 
			goto done;

	}



	if (log_level || !log_buf)

		goto done;



	/* Try again with log */

	log_buf[0] = 0;

	if (log_level == 0 && log_buf) {

		/* log_level == 0 with non-NULL log_buf requires retrying on error

		 * with log_level == 1 and log_buf/log_buf_size set, to get details of

		 * failure

		 */

		attr.log_buf = ptr_to_u64(log_buf);

		attr.log_size = log_size;

		attr.log_level = 1;



		fd = sys_bpf_prog_load(&attr, sizeof(attr), attempts);

	}

done:

	/* free() doesn't affect errno, so we don't need to restore it */

	free(finfo);