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

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Date:   Tue, 3 Nov 2020 06:55:21 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Nathan Chancellor <natechancellor@...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 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 :-)


> +
>  /* Compiler specific definitions for Clang compiler */
>  
>  /* same as gcc, this was present in clang-2.6 so we can assume it works
> -- 
> 2.28.0.402.g5ffc5be6b7-goog
> 

/Jarkko