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Date: Wed, 10 Jan 2024 21:41:00 +0100
From: "Arnd Bergmann" <arnd@arndb.de>
To: "Thomas Voegtle" <tv@lio96.de>, linux-kernel@vger.kernel.org
Subject: Re: Build error kernel/cgroup/rstat.c on v6.7-1959-gaffc5af36bbb
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On Wed, Jan 10, 2024, at 20:50, Thomas Voegtle wrote:
> Hello,
>
> building v6.7-1959-gaffc5af36bbb I get this:
>
> ...
>    CALL    scripts/checksyscalls.sh
>    DESCEND objtool
>    INSTALL libsubcmd_headers
>    CC      kernel/cgroup/rstat.o
> kernel/cgroup/rstat.c:218:22: error: no previous prototype for
> =E2=80=98bpf_rstat_flush=E2=80=99 [-Werror=3Dmissing-prototypes]
>   __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
>                        ^~~~~~~~~~~~~~~
>
>
> git bisects points to:
>
> commit 0fcb70851fbfea1776ae62f67c503fef8f0292b9 (refs/bisect/bad)
> Author: Arnd Bergmann <arnd@arndb.de>
> Date:   Thu Nov 23 12:05:06 2023 +0100
>
>      Makefile.extrawarn: turn on missing-prototypes globally
>
>
> My config is attached.
> openSUSE Leap 15.5 x86_64 with gcc 7.5.0
>
>
> Is this already known?

There is a workaround in linux-next, see commit
15fb6f2b6c4c ("bpf: Add __bpf_hook_{start,end} macros")

I assume this will be merged soon.

     Arnd