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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 10 Sep 2018 14:14:13 +0200
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Subject: Re: [PATCH] include/linux/compiler-clang.h: define __naked
To:     Stefan Agner <stefan@agner.ch>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Will Deacon <will.deacon@arm.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        David Woodhouse <dwmw@amazon.co.uk>, paullawrence@google.com,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
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On Mon, Sep 10, 2018 at 8:05 AM Stefan Agner <stefan@agner.ch> wrote:
>
> ARM32 arch code uses the __naked attribute. This has previously been
> defined in include/linux/compiler-gcc.h, which is no longer included
> for Clang. Define __naked for Clang. Conservatively add all attributes
> previously used (and supported by Clang).
>
> This fixes compile errors when building ARM32 using Clang:
>   arch/arm/mach-exynos/mcpm-exynos.c:193:13: error: variable has incomplete type 'void'
>   static void __naked exynos_pm_power_up_setup(unsigned int affinity_level)
>               ^
>
> Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
> Signed-off-by: Stefan Agner <stefan@agner.ch>

> +/*
> + * ARM32 is currently the only user of __naked supported by Clang. Follow
> + * gcc: Do not trace naked functions and make sure they don't get inlined.
> + */
> +#define __naked __attribute__((naked)) noinline notrace
> +

Please see patches 5 and 6 of the series that Miguel posted:

https://lore.kernel.org/lkml/20180908212459.19736-6-miguel.ojeda.sandonis@gmail.com/

I suppose we want the patch to fix clang build as soon as possible though,
and follow up with the cleanup for the next merge window, right?

       Arnd