linux-kernel - Re: [PATCH bpf-next v3 2/4] bpf: Add log for attaching tracing programs to functions in deny list

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Message-ID: <CALOAHbCtiBFZP8GF63g1HmKWko_35uj34+wx5K3QU95QDLaedg@mail.gmail.com>
Date: Wed, 23 Jul 2025 19:37:55 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: KaFai Wan <kafai.wan@...ux.dev>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com, 
	andrii@...nel.org, martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org, 
	yonghong.song@...ux.dev, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, mykolal@...com, shuah@...nel.org, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, leon.hwang@...ux.dev
Subject: Re: [PATCH bpf-next v3 2/4] bpf: Add log for attaching tracing
 programs to functions in deny list

On Tue, Jul 22, 2025 at 11:35 PM KaFai Wan <kafai.wan@...ux.dev> wrote:
>
> 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 migrate_disable() from log.
>
> $ ./fentry
> libbpf: prog 'migrate_disable': BPF program load failed: -EINVAL
> libbpf: prog 'migrate_disable': -- BEGIN PROG LOAD LOG --
> Attaching tracing programs to function 'migrate_disable' is rejected.
>
> Suggested-by: Leon Hwang <leon.hwang@...ux.dev>
> Signed-off-by: KaFai Wan <kafai.wan@...ux.dev>

Acked-by: Yafang Shao <laoar.shao@...il.com>

> ---
>  kernel/bpf/verifier.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 00d287814f12..c24c0d57e595 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -23942,6 +23942,8 @@ 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) &&
> --
> 2.43.0
>


-- 
Regards
Yafang