linux-kernel - Re: [PATCH bpf-next v6 1/3] bpf: Show precise link_type for {uprobe,kprobe}

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Message-ID: <983eacae-5b5d-4d26-a3e4-3c3eb808c5f2@linux.dev>
Date: Wed, 2 Jul 2025 10:14:58 +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>,
 John Fastabend <john.fastabend@...il.com>,
 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>,
 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 v6 1/3] bpf: Show precise link_type for
 {uprobe,kprobe}_multi fdinfo

在 2025/7/2 04:39, Alexei Starovoitov 写道:
> On Fri, Jun 27, 2025 at 1:23 AM Tao Chen <chen.dylane@...ux.dev> wrote:
>>
>> Alexei suggested, 'link_type' can be more precise and differentiate
>> for human in fdinfo. In fact BPF_LINK_TYPE_KPROBE_MULTI includes
>> kretprobe_multi type, the same as BPF_LINK_TYPE_UPROBE_MULTI, so we
>> can show it more concretely.
>>
>> link_type:      kprobe_multi
>> link_id:        1
>> prog_tag:       d2b307e915f0dd37
>> ...
>> link_type:      kretprobe_multi
>> link_id:        2
>> prog_tag:       ab9ea0545870781d
>> ...
>> link_type:      uprobe_multi
>> link_id:        9
>> prog_tag:       e729f789e34a8eca
>> ...
>> link_type:      uretprobe_multi
>> link_id:        10
>> prog_tag:       7db356c03e61a4d4
>>
>> As Andrii suggested attach_type can be recorded in bpf_link, there is
>> still a 6 byte hole in bpf_link, we can fill the hole with attach_type
>> soon.
>>
>> Co-authored-by: Jiri Olsa <jolsa@...nel.org>
>> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
>> ---
>>   include/linux/bpf.h      |  1 +
>>   kernel/bpf/syscall.c     |  9 ++++++++-
>>   kernel/trace/bpf_trace.c | 10 ++++------
>>   3 files changed, 13 insertions(+), 7 deletions(-)
>>
>> Change list:
>>    v5 -> v6:
>>      - Move flags into bpf_link to get retprobe info
>>        directly.(Alexei, Jiri)
>>    v5:
>>    https://lore.kernel.org/bpf/20250623134342.227347-1-chen.dylane@linux.dev
>>
>>    v4 -> v5:
>>      - Add patch1 to show precise link_type for
>>        {uprobe,kprobe}_multi.(Alexei)
>>      - patch2,3 just remove type field, which will be showed in
>>        link_type
>>    v4:
>>    https://lore.kernel.org/bpf/20250619034257.70520-1-chen.dylane@linux.dev
>>
>>    v3 -> v4:
>>      - use %pS to print func info.(Alexei)
>>    v3:
>>    https://lore.kernel.org/bpf/20250616130233.451439-1-chen.dylane@linux.dev
>>
>>    v2 -> v3:
>>      - show info in one line for multi events.(Jiri)
>>    v2:
>>    https://lore.kernel.org/bpf/20250615150514.418581-1-chen.dylane@linux.dev
>>
>>    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/include/linux/bpf.h b/include/linux/bpf.h
>> index 5b25d278409..3d8fecc9b17 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -1702,6 +1702,7 @@ struct bpf_link {
>>           * link's semantics is determined by target attach hook
>>           */
>>          bool sleepable;
>> +       u32 flags :8;
> 
> There is a 7-byte hole here.
> Let's use 'u32 flags' right now and optimize later if necessary.

Ok, will change it in v7.

-- 
Best Regards
Tao Chen