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

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Message-ID: <CAADnVQJcdVCKPu8aPPj5hZExNTFYAYTd5xkF=Ljfm__+ugirGg@mail.gmail.com>
Date: Thu, 19 Jun 2025 19:59:58 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Tao Chen <chen.dylane@...ux.dev>
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

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.