linux-kernel - Re: [PATCH bpf-next 1/2] bpf: Add show_fdinfo for uprobe

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Message-ID: <6473772f-0de8-41f2-9ff7-b448287f5d84@linux.dev>
Date: Fri, 13 Jun 2025 10:28:05 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
 yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
 sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org,
 mattbobrowski@...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 1/2] bpf: Add show_fdinfo for uprobe_multi

在 2025/6/13 05:27, Andrii Nakryiko 写道:
> On Thu, Jun 12, 2025 at 4:56 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:        9
>> prog_tag:       e729f789e34a8eca
>> prog_id:        39
>> type:   uprobe_multi
>> func_cnt:       3
>> pid:    0
>> path:   /home/dylane/bpf/tools/testing/selftests/bpf/test_progs
>> offset: 0xa69ed7
>> ref_ctr_offset: 0x0
>> cookie: 3
>> offset: 0xa69ee2
>> ref_ctr_offset: 0x0
>> cookie: 1
>> offset: 0xa69eed
>> ref_ctr_offset: 0x0
>> cookie: 2
>>
>> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
>> ---
>>   kernel/trace/bpf_trace.c | 48 ++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 48 insertions(+)
>>
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index 24b94870b50..c4ad82b8fd8 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -3157,10 +3157,58 @@ 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,
>> +                  "type:\t%s\n"
>> +                  "func_cnt:\t%u\n"
> 
> it's not really *func* (e.g., for USDTs it's basically guaranteed to
> be somewhere inside the function, potentially in many places within
> the same function), I'd use generic "uprobe_{cnt,count}"
> 
>

will change it in v2, thanks for the advice.

>> +                  "pid:\t%u\n"
>> +                  "path:\t%s\n",
>> +                  umulti_link->flags == BPF_F_UPROBE_MULTI_RETURN ?
>> +                                        "uretprobe_multi" : "uprobe_multi",
>> +                  umulti_link->cnt,
>> +                  umulti_link->task ? task_pid_nr_ns(umulti_link->task,
>> +                          task_active_pid_ns(current)) : 0,
>> +                  p);
>> +
>> +       for (int i = 0; i < umulti_link->cnt; i++) {
>> +               seq_printf(seq,
>> +                          "offset:\t%#llx\n"
>> +                          "ref_ctr_offset:\t%#lx\n"
>> +                          "cookie:\t%llu\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