linux-kernel - Re: [PATCH bpf-next v2 1/2] bpf: Add show_fdinfo for uprobe

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Message-ID: <fdc58e38-8b54-4681-89e9-78f8941db1b0@linux.dev>
Date: Mon, 16 Jun 2025 16:39:35 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: Jiri Olsa <olsajiri@...il.com>
Cc: song@...nel.org, kpsingh@...nel.org, mattbobrowski@...gle.com,
 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 v2 1/2] bpf: Add show_fdinfo for uprobe_multi

在 2025/6/16 15:40, Jiri Olsa 写道:
> On Sun, Jun 15, 2025 at 11:05:13PM +0800, Tao Chen wrote:
>> Show uprobe_multi link info with fdinfo, the info as follows:
>>
>> link_type:	uprobe_multi
>> link_id:	9
>> prog_tag:	e729f789e34a8eca
>> prog_id:	58
>> type:	uprobe_multi
>> uprobe_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
> 
> hi,
> does this need to be 'tag: value' format ? bpftool uses:
> 
>          offset             ref_ctr_offset     cookies
>          0xe558             0x0                0x0
>          0x2574e            0x0                0x0
>          0x6c393            0x0                0x0
> 
> which might be more readable, or at least extra line after each uprobe?
> also using spaces instead of tabs  to align the values might help
> 
> same for kprobe_multi, otherwise looks lgtm
> 

That's a great suggestion, it does look more concise. I will change it 
in v3, thanks!

> thanks,
> jirka
> 
> 
>>
>> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
>> ---
>>   kernel/trace/bpf_trace.c | 48 ++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 48 insertions(+)
>>
>> Change list:
>>    v1 -> v2:
>>      - replace 'func_cnt' with 'uprobe_cnt'.(Andrii)
>>      - print func name is more readable and security for kprobe_multi.(Alexei)
>>    v1:
>>    https://lore.kernel.org/bpf/20250612115556.295103-1-chen.dylane@linux.dev
>>
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index 24b94870b50..9a8ca8a8e2b 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"
>> +		   "uprobe_cnt:\t%u\n"
>> +		   "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