linux-kernel - Re: [PATCH bpf-next v3] libbpf: Fix expected_attach

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Message-ID: <5310a4f2-3b45-4a3e-b05c-fcc5faba7c0e@gmail.com>
Date: Thu, 19 Sep 2024 21:45:58 +0800
From: Tao Chen <chen.dylane@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman
 <eddyz87@...il.com>, Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, 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>, bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v3] libbpf: Fix expected_attach_type set when
 kernel not support

在 2024/9/19 12:20, Andrii Nakryiko 写道:
> On Thu, Sep 19, 2024 at 4:05 AM Tao Chen <chen.dylane@...il.com> wrote:
>>
>> 在 2024/9/14 23:40, Tao Chen 写道:
>>> The commit "5902da6d8a52" set expected_attach_type again with
>>> field of bpf_program after libpf_prepare_prog_load, which makes
>>> expected_attach_type = 0 no sense when kenrel not support the
>>> attach_type feature, so fix it.
>>>
>>> Fixes: 5902da6d8a52 ("libbpf: Add uprobe multi link support to bpf_program__attach_usdt")
>>> Suggested-by: Jiri Olsa <jolsa@...nel.org>
>>> Signed-off-by: Tao Chen <chen.dylane@...il.com>
>>> ---
>>>    tools/lib/bpf/libbpf.c | 12 ++++++++----
>>>    1 file changed, 8 insertions(+), 4 deletions(-)
>>>
>>> Change list:
>>> - v2 -> v3:
>>>       - update BPF_TRACE_UPROBE_MULTI both in prog and opts suggedted by
>>>         Andrri
>>> - v1 -> v2:
>>>       - restore the original initialization way suggested by Jiri
>>>
>>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>>> index 219facd0e66e..a78e24ff354b 100644
>>> --- a/tools/lib/bpf/libbpf.c
>>> +++ b/tools/lib/bpf/libbpf.c
>>> @@ -7352,8 +7352,14 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog,
>>>                opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;
>>>
>>>        /* special check for usdt to use uprobe_multi link */
>>> -     if ((def & SEC_USDT) && kernel_supports(prog->obj, FEAT_UPROBE_MULTI_LINK))
>>> +     if ((def & SEC_USDT) && kernel_supports(prog->obj, FEAT_UPROBE_MULTI_LINK)) {
>>> +             /* for BPF_TRACE_KPROBE_MULTI, user might want to query exected_attach_type
>>> +              * in prog, and expected_attach_type we set in kenrel is from opts, so we
>>> +              * update both.
>>> +              */
>>>                prog->expected_attach_type = BPF_TRACE_UPROBE_MULTI;
>>> +             opts->expected_attach_type = BPF_TRACE_UPROBE_MULTI;
>>> +     }
>>>
>>>        if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
>>>                int btf_obj_fd = 0, btf_type_id = 0, err;
>>> @@ -7443,6 +7449,7 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
>>>        load_attr.attach_btf_id = prog->attach_btf_id;
>>>        load_attr.kern_version = kern_version;
>>>        load_attr.prog_ifindex = prog->prog_ifindex;
>>> +     load_attr.expected_attach_type = prog->expected_attach_type;
>>>
>>>        /* specify func_info/line_info only if kernel supports them */
>>>        if (obj->btf && btf__fd(obj->btf) >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) {
>>> @@ -7474,9 +7481,6 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
>>>                insns_cnt = prog->insns_cnt;
>>>        }
>>>
>>> -     /* allow prog_prepare_load_fn to change expected_attach_type */
>>> -     load_attr.expected_attach_type = prog->expected_attach_type;
>>> -
>>>        if (obj->gen_loader) {
>>>                bpf_gen__prog_load(obj->gen_loader, prog->type, prog->name,
>>>                                   license, insns, insns_cnt, &load_attr,
>>
>> Hi, guys, please review this patch again, the previous versions:
> 
> It looks good, but bpf-next is closed right now due to merge window.
> I'll apply when the tree is open again.

Hi，Andrii, thank you for your response! I’ll wait for the next window.

> 
>> v1:
>> https://lore.kernel.org/bpf/20240913121627.153898-1-chen.dylane@gmail.com/
>> v2:
>> https://lore.kernel.org/bpf/20240913164355.176021-1-chen.dylane@gmail.com/
>>
>> --
>> Best Regards
>> Dylane Chen


-- 
Best Regards
Dylane Chen