Re: [PATCH] include/linux/compiler-clang.h: define __naked

From: Nick Desaulniers <ndesaulniers@google.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Stefan Agner <stefan@agner.ch>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	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>,
	dwmw@amazon.co.uk, Paul Lawrence <paullawrence@google.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Subject: Re: [PATCH] include/linux/compiler-clang.h: define __naked
Date: Mon, 10 Sep 2018 09:51:24 -0700	[thread overview]
Message-ID: <CAKwvOd=E6+QSoRqcMJ0o1_q8VSMO8Zoi75e+zhj2SRSTdfacJw@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a2cc741UqFSk+hXpC2s4S+A+0FuiM1yP=Z4rC18sJHq9g@mail.gmail.com>

On Mon, Sep 10, 2018 at 5:14 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> 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>

Cool, thanks for this patch! I'll admit I need to start testing more
architectures with Clang.

>
> > +/*
> > + * 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/

Yes, I'd prefer those 2 patches.

>
> 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?

Can we take Miguel's two patches from above in the ARM tree, since
this attribute is only used on ARM, IIUC?

-- 
Thanks,
~Nick Desaulniers