linux-kernel - Re: [PATCH 1/2] [v2] bpf: hide unused bpf_patch_call

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Message-ID: <d809e25a-f109-14ff-420d-50dced7b4dfb@meta.com>
Date:   Wed, 24 May 2023 11:12:47 -0700
From:   Yonghong Song <yhs@...a.com>
To:     Arnd Bergmann <arnd@...db.de>, Arnd Bergmann <arnd@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] [v2] bpf: hide unused bpf_patch_call_args



On 5/24/23 6:23 AM, Arnd Bergmann wrote:
> On Wed, May 24, 2023, at 05:05, Yonghong Song wrote:
>> On 5/23/23 12:43 PM, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@...db.de>
>>>
>>> This function has no callers and no declaration when CONFIG_BPF_JIT_ALWAYS_ON
>>> is enabled:
>>>
>>> kernel/bpf/core.c:2075:6: error: no previous prototype for 'bpf_patch_call_args' [-Werror=missing-prototypes]
>>
>> If CONFIG_BPF_JIT_ALWAYS_ON is enabled, the definition of
>> bpf_patch_call_args should be invisible. Maybe I missed something.
>> Could you list *ALL& bpf related config options in your setup
>> so people can reproduce you above error messages?
> 
> Sorry, my mistake. I've reworded the changelog now to fix this:
> 
> | This function is only used when CONFIG_BPF_JIT_ALWAYS_ON is disabled,
> | but CONFIG_BPF_SYSCALL is enabled. When both are turned off, the
> | prototype is missing but the unused function is still compiled,
> | as seen from this W=1 warning:
> |
> | kernel/bpf/core.c:2075:6: error: no previous prototype for 'bpf_patch_call_args' [-Werror=missing-prototypes]
> |
> | Add a matching #ifdef for the definition to leave it out.
> 
> If this makes sense now, I'll send out a v3.

Yes, the above new commit message sounds good to me. Thanks.

> 
>        Arnd