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bpf: Add log for attaching tracing programs to functions in deny list

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Show the rejected function name when attaching tracing programs to
functions in deny list.

With this change, we know why tracing programs can't attach to functions
like __rcu_read_lock() from log.

$ ./fentry
libbpf: prog '__rcu_read_lock': BPF program load failed: -EINVAL
libbpf: prog '__rcu_read_lock': -- BEGIN PROG LOAD LOG --
Attaching tracing programs to function '__rcu_read_lock' 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/20250724151454.499040-3-kafai.wan@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
KaFai Wan
2025-07-24 23:14:52 +08:00
committed by Alexei Starovoitov
parent a5a6b29a70
commit 863aab3d4d
1 changed files with 2 additions and 0 deletions
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2
kernel/bpf/verifier.c
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@@ -23981,6 +23981,8 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
return ret;
} else if (prog->type == BPF_PROG_TYPE_TRACING &&
btf_id_set_contains(&btf_id_deny, btf_id)) {
verbose(env, "Attaching tracing programs to function '%s' is rejected.\n",
tgt_info.tgt_name);
return -EINVAL;
} else if ((prog->expected_attach_type == BPF_TRACE_FEXIT ||
prog->expected_attach_type == BPF_MODIFY_RETURN) &&