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>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e50d3d43be67f5e8e8a7ebbcad5a8f796e9ea15d..4bf7392fd2c3af2f277e3feb1d0a40c26ce0550d 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -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;
        }
 

diff --git a/tools/testing/selftests/bpf/progs/fexit_noreturns.c b/tools/testing/selftests/bpf/progs/fexit_noreturns.c
index 54654539f550cef75b8599ed43abe4347bea61da..b1c33d958ae2e3e3be93529e0ccf47127be696cf 100644 (file)
--- a/tools/testing/selftests/bpf/progs/fexit_noreturns.c
+++ b/tools/testing/selftests/bpf/progs/fexit_noreturns.c
@@ -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;