linux-kernel - Re: [PATCH bpf-next v4 2/2] bpf: Add show_fdinfo for kprobe

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Message-ID: <77b09f48-01d9-46f1-8a31-a1824c0eef8d@linux.dev>
Date: Fri, 20 Jun 2025 11:31:38 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Matt Bobrowski <mattbobrowski@...gle.com>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
 linux-trace-kernel <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 2/2] bpf: Add show_fdinfo for kprobe_multi

在 2025/6/20 10:59, Alexei Starovoitov 写道:
> On Thu, Jun 19, 2025 at 7:46 PM Tao Chen <chen.dylane@...ux.dev> wrote:
>>
>> 在 2025/6/20 01:17, Alexei Starovoitov 写道:
>>> On Wed, Jun 18, 2025 at 8:44 PM Tao Chen <chen.dylane@...ux.dev> wrote:
>>>>
>>>> Show kprobe_multi link info with fdinfo, the info as follows:
>>>>
>>>> link_type:      kprobe_multi
>>>> link_id:        1
>>>> prog_tag:       a15b7646cb7f3322
>>>> prog_id:        21
>>>> type:   kprobe_multi
>>>
>>> ..
>>>
>>>> +       seq_printf(seq,
>>>> +                  "type:\t%s\n"
>>>> +                  "kprobe_cnt:\t%u\n"
>>>> +                  "missed:\t%lu\n",
>>>> +                  kmulti_link->flags == BPF_F_KPROBE_MULTI_RETURN ? "kretprobe_multi" :
>>>> +                                        "kprobe_multi",
>>>
>>> why print the same info twice ?
>>> seq_printf(m, "link_type:\t%s\n", bpf_link_type_strs[type]);
>>> in bpf_link_show_fdinfo() already did it in a cleaner way.
>>>
>>
>> link_type only shows 'kprobe_multi', maybe we can show the format like:
> 
> Ohh. Especially so. It would be wrong and confusing to display:
> link_type:      kprobe_multi
> type: kretprobe_multi
> 
> Let's fix 'link_type' to display it properly.

What do you think show like this:

     link_type:      kprobe_multi
     link_id:        1
     prog_tag:       33be53a4fd673e1d
     prog_id:        21
     retprobe:       false
     kprobe_cnt:     8
     missed: 0
     cookie           func
     1                bpf_fentry_test1+0x0/0x20
     7                bpf_fentry_test2+0x0/0x20
     2                bpf_fentry_test3+0x0/0x20
     3                bpf_fentry_test4+0x0/0x20
     4                bpf_fentry_test5+0x0/0x20
     5                bpf_fentry_test6+0x0/0x20
     6                bpf_fentry_test7+0x0/0x20
     8                bpf_fentry_test8+0x0/0x10

-- 
Best Regards
Tao Chen