Commit a5a6b29a authored Jul 24, 2025 by KaFai Wan Committed by Alexei Starovoitov Jul 28, 2025

bpf: Show precise rejected function when attaching fexit/fmod_ret to __noreturn functions



With this change, we know the precise rejected function name when
attaching fexit/fmod_ret to __noreturn functions from log.

$ ./fexit
libbpf: prog 'fexit': BPF program load failed: -EINVAL
libbpf: prog 'fexit': -- BEGIN PROG LOAD LOG --
Attaching fexit/fmod_ret to __noreturn function 'do_exit' is rejected.

Suggested-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250724151454.499040-2-kafai.wan@linux.dev


Signed-off-by: Alexei Starovoitov <ast@kernel.org>

parent 5b4c54ac

kernel/bpf/verifier.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -23985,7 +23985,8 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
		} else if ((prog->expected_attach_type == BPF_TRACE_FEXIT \|\|
		prog->expected_attach_type == BPF_MODIFY_RETURN) &&
		btf_id_set_contains(&noreturn_deny, btf_id)) {
		verbose(env, "Attaching fexit/fmod_ret to __noreturn functions is rejected.\n");
		verbose(env, "Attaching fexit/fmod_ret to __noreturn function '%s' is rejected.\n",
		tgt_info.tgt_name);
		return -EINVAL;
		}

tools/testing/selftests/bpf/progs/fexit_noreturns.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -8,7 +8,7 @@
		char _license[] SEC("license") = "GPL";

		SEC("fexit/do_exit")
		__failure __msg("Attaching fexit/fmod_ret to __noreturn functions is rejected.")
		__failure __msg("Attaching fexit/fmod_ret to __noreturn function 'do_exit' is rejected.")
		int BPF_PROG(noreturns)
		{
		return 0;