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From:   Kees Cook <keescook@chromium.org>
Date:   Thu, 23 Aug 2018 01:32:34 -0700
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Subject: Re: [PATCH] include/linux/compiler*.h: make compiler-*.h mutually exclusive
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Dominique Martinet <asmadeus@codewreck.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Joe Perches <joe@perches.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Arnd Bergmann <arnd@arndb.de>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will.deacon@arm.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Peter Anvin <hpa@zytor.com>
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On Wed, Aug 22, 2018 at 6:02 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Aug 22, 2018 at 5:25 PM Dominique Martinet
> <asmadeus@codewreck.org> wrote:
>>
>> Overall looks good to me, just pointing at the same error I wrote in my
>> other mail here -- I saw that by the time I was done writing this this
>> patch got taken but that alone will probably warrant a follow-up :/
>
> I've fixed that manually, but when I tried to test it I just hit the
>
>   arch/x86/Makefile:179: *** Compiler lacks asm-goto support..  Stop.
>
> error.
>
> Do you have some experimental clang build with asm goto support? What
> version? Or is it just that you're building ARM, not x86?

FWIW, when I do Clang test builds lately[1], I've been using:

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CC=clang

(Note this requires a cross-compiled binutils installed in the PATH
with as aarch64-linux-gnu-*, which is where Debian and Ubuntu put
them.)

-Kees

[1] for today's defconfig build to finish, I had to:

./scripts/config -d CONFIG_ARM64_LSE_ATOMICS
(I think my binutils are old)

and comment out the BUILD_BUG_ON() in net/core/filter.c from 2dbb9b9e6df67
(which looks like it needs some attention since gcc has no problem with this)

-- 
Kees Cook
Pixel Security