linux-kernel - Re: [PATCH bpf-next v5 2/3] bpf: Add show_fdinfo for uprobe

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Message-ID: <3cdf1037-7e2d-4cc8-8298-10feee43deac@linux.dev>
Date: Tue, 24 Jun 2025 16:42:06 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: kpsingh@...nel.org, mattbobrowski@...gle.com, song@...nel.org,
 jolsa@...nel.org, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 martin.lau@...ux.dev, eddyz87@...il.com, yonghong.song@...ux.dev,
 john.fastabend@...il.com, sdf@...ichev.me, haoluo@...gle.com,
 rostedt@...dmis.org, mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
 bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v5 2/3] bpf: Add show_fdinfo for uprobe_multi

在 2025/6/24 06:14, Andrii Nakryiko 写道:
> On Mon, Jun 23, 2025 at 6:45 AM Tao Chen <chen.dylane@...ux.dev> wrote:
>>
>> Show uprobe_multi link info with fdinfo, the info as follows:
>>
>> link_type:      uprobe_multi
>> link_id:        10
>> prog_tag:       7db356c03e61a4d4
>> prog_id:        42
>> uprobe_cnt:     3
>> pid:    0
>> path:   /home/dylane/bpf/tools/testing/selftests/bpf/test_progs
>> offset           ref_ctr_offset   cookie
>> 0xa69f13         0x0              2
>> 0xa69f1e         0x0              3
>> 0xa69f29         0x0              1
>>
>> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
>> ---
>>   kernel/trace/bpf_trace.c | 44 ++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 44 insertions(+)
>>
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index 8ecb1a9f85d..90209dda819 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -3171,10 +3171,54 @@ static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link,
>>          return err;
>>   }
>>
>> +#ifdef CONFIG_PROC_FS
>> +static void bpf_uprobe_multi_show_fdinfo(const struct bpf_link *link,
>> +                                        struct seq_file *seq)
>> +{
>> +       struct bpf_uprobe_multi_link *umulti_link;
>> +       char *p, *buf;
>> +
>> +       umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
>> +
>> +       buf = kmalloc(PATH_MAX, GFP_KERNEL);
>> +       if (!buf)
>> +               return;
>> +
>> +       p = d_path(&umulti_link->path, buf, PATH_MAX);
>> +       if (IS_ERR(p)) {
>> +               kfree(buf);
>> +               return;
>> +       }
>> +
>> +       seq_printf(seq,
>> +                  "uprobe_cnt:\t%u\n"
>> +                  "pid:\t%u\n"
>> +                  "path:\t%s\n",
>> +                  umulti_link->cnt,
>> +                  umulti_link->task ? task_pid_nr_ns(umulti_link->task,
>> +                          task_active_pid_ns(current)) : 0,
> 
> nit: either keep stuff like this on single line, or if it's too long
> or awkward, add a local variable. Formatting it like this is very hard
> to follow and looks pretty ugly...
> 

will fix it in v6, thanks.

>> +                  p);
>> +
>> +       seq_printf(seq, "%-16s %-16s %-16s\n", "offset", "ref_ctr_offset", "cookie");
>> +       for (int i = 0; i < umulti_link->cnt; i++) {
>> +               seq_printf(seq,
>> +                          "%#-16llx %#-16lx %-16llu\n",
>> +                          umulti_link->uprobes[i].offset,
>> +                          umulti_link->uprobes[i].ref_ctr_offset,
>> +                          umulti_link->uprobes[i].cookie);
>> +       }
>> +
>> +       kfree(buf);
>> +}
>> +#endif
>> +
>>   static const struct bpf_link_ops bpf_uprobe_multi_link_lops = {
>>          .release = bpf_uprobe_multi_link_release,
>>          .dealloc_deferred = bpf_uprobe_multi_link_dealloc,
>>          .fill_link_info = bpf_uprobe_multi_link_fill_link_info,
>> +#ifdef CONFIG_PROC_FS
>> +       .show_fdinfo = bpf_uprobe_multi_show_fdinfo,
>> +#endif
>>   };
>>
>>   static int uprobe_prog_run(struct bpf_uprobe *uprobe,
>> --
>> 2.48.1
>>


-- 
Best Regards
Tao Chen