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From:   Marco Elver <elver@google.com>
Date:   Thu, 10 Dec 2020 11:35:11 +0100
Message-ID: <CANpmjNOdJZUm1apuEHZz_KYJTEoRU6FVxMwZUrMar021hTd5Cg@mail.gmail.com>
Subject: Re: [PATCH] genksyms: Ignore module scoped _Static_assert()
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Joe Perches <joe@perches.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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On Fri, 4 Dec 2020 at 11:21, Marco Elver <elver@google.com> wrote:
> On Tue, 1 Dec 2020 at 21:00, Nick Desaulniers <ndesaulniers@google.com> wrote:
> > On Tue, Dec 1, 2020 at 7:21 AM Marco Elver <elver@google.com> wrote:
> > > The C11 _Static_assert() keyword may be used at module scope, and we
> > > need to teach genksyms about it to not abort with an error. We currently
> > > have a growing number of static_assert() (but also direct usage of
> > > _Static_assert()) users at module scope:
> > >
> > >         git grep -E '^_Static_assert\(|^static_assert\(' | grep -v '^tools' | wc -l
> > >         135
> > >
> > > More recently, when enabling CONFIG_MODVERSIONS with CONFIG_KCSAN, we
> > > observe a number of warnings:
> > >
> > >         WARNING: modpost: EXPORT symbol "<..all kcsan symbols..>" [vmlinux] [...]
> > >
> > > When running a preprocessed source through 'genksyms -w' a number of
> > > syntax errors point at usage of static_assert()s. In the case of
> > > kernel/kcsan/encoding.h, new static_assert()s had been introduced which
> > > used expressions that appear to cause genksyms to not even be able to
> > > recover from the syntax error gracefully (as it appears was the case
> > > previously).
> > >
> > > Therefore, make genksyms ignore all _Static_assert() and the contained
> > > expression. With the fix, usage of _Static_assert() no longer cause
> > > "syntax error" all over the kernel, and the above modpost warnings for
> > > KCSAN are gone, too.
> > >
> > > Signed-off-by: Marco Elver <elver@google.com>
> >
> > Ah, genksyms...if only there were a library that we could use to parse
> > C code...:P
> > Acked-by: Nick Desaulniers <ndesaulniers@google.com>
>
> Which tree would this go into?
>
> It'd be good if this problem could be fixed for 5.11.

[+Cc everyone returned by 'get_maintainers.pl scripts/genksyms']

It looks like there's no clear MAINTAINER for this. :-/
It'd still be good to fix this for 5.11.

Thanks,
-- Marco