linux-kernel - [PATCH bpf-next 1/3] bpf: Show precise rejected function when attaching to _

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Message-ID: <20250710162717.3808020-2-mannkafai@gmail.com>
Date: Fri, 11 Jul 2025 00:27:15 +0800
From: KaFai Wan <mannkafai@...il.com>
To: ast@...nel.org,
	daniel@...earbox.net,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
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	haoluo@...gle.com,
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	mykolal@...com,
	shuah@...nel.org,
	mannkafai@...il.com,
	laoar.shao@...il.com,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH bpf-next 1/3] bpf: Show precise rejected function when attaching to __noreturn functions

Show the precise rejected function name when attaching fexit/fmod_ret
to __noreturn functions.

$ ./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.

Signed-off-by: KaFai Wan <mannkafai@...il.com>
---
 kernel/bpf/verifier.c                               | 3 ++-
 tools/testing/selftests/bpf/progs/fexit_noreturns.c | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 53007182b46b..275d82fb1a1a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -23942,7 +23942,8 @@ 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 54654539f550..b1c33d958ae2 100644
--- 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;
-- 
2.43.0