linux-kernel - Re: [PATCH v3 1/7] compiler-clang: add build check for clang 10.0.1

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Message-ID: <20201103063814.GA647990@ubuntu-m3-large-x86>
Date:   Mon, 2 Nov 2020 23:38:14 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        clang-built-linux@...glegroups.com,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Will Deacon <will@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/7] compiler-clang: add build check for clang 10.0.1

On Tue, Nov 03, 2020 at 06:55:21AM +0200, Jarkko Sakkinen wrote:
> On Wed, Sep 02, 2020 at 03:59:05PM -0700, Nick Desaulniers wrote:
> > During Plumbers 2020, we voted to just support the latest release of
> > Clang for now.  Add a compile time check for this.
> > 
> > We plan to remove workarounds for older versions now, which will break
> > in subtle and not so subtle ways.
> > 
> > Suggested-by: Sedat Dilek <sedat.dilek@...il.com>
> > Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> > Suggested-by: Kees Cook <keescook@...omium.org>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Tested-by: Sedat Dilek <sedat.dilek@...il.com>
> > Reviewed-by: Kees Cook <keescook@...omium.org>
> > Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
> > Reviewed-by: Sedat Dilek <sedat.dilek@...il.com>
> > Acked-by: Marco Elver <elver@...gle.com>
> > Acked-by: Nathan Chancellor <natechancellor@...il.com>
> > Acked-by: Sedat Dilek <sedat.dilek@...il.com>
> > Link: https://github.com/ClangBuiltLinux/linux/issues/9
> > Link: https://github.com/ClangBuiltLinux/linux/issues/941
> > ---
> >  include/linux/compiler-clang.h | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> > index cee0c728d39a..230604e7f057 100644
> > --- a/include/linux/compiler-clang.h
> > +++ b/include/linux/compiler-clang.h
> > @@ -3,6 +3,14 @@
> >  #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
> >  #endif
> >  
> > +#define CLANG_VERSION (__clang_major__ * 10000	\
> > +		     + __clang_minor__ * 100	\
> > +		     + __clang_patchlevel__)
> > +
> > +#if CLANG_VERSION < 100001
> > +# error Sorry, your version of Clang is too old - please use 10.0.1 or newer.
> > +#endif
> 
> 
> I'm trying to compile a BPF enabled test kernel for a live system and I
> get this error even though I have much newer clang:
> 
> ➜  ~ (master) ✔ clang --version          
> Ubuntu clang version 11.0.0-2
> Target: x86_64-pc-linux-gnu
> Thread model: posix
> InstalledDir: /usr/bin
> 
> Tried to Google for troubleshooter tips but this patch is basically the
> only hit I get :-)

Do you have a .config and command to reproduce the error?

Cheers,
Nathan