linux-kernel - Re: [PATCH] x86/process: Silence KASAN warnings in get

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Date:	Wed, 7 Oct 2015 11:54:42 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>
CC:	Andi Kleen <ak@...ux.intel.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Wolfram Gloger <wmglo@...t.med.uni-muenchen.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86/process: Silence KASAN warnings in get_wchan()

On 10/06/2015 09:11 PM, Andy Lutomirski wrote:
> 
> But what's wrong with the GCC attribute mechanism?  Surely GCC ought
> to be able to generate the code, at least in the simple cases, and the
> attribute already exists.  The attribute and READ_ONCE_NOCHECK seem
> like the least messy in the C code.

The problem with 'no_sanitize_address' attribute is incompatibility with inlining. 
GCC can't inline function with that attribute into function without it.
And the contrary is also true - GCC can't inline function without attribute into function with such attribute.

Failure to inline always_inline function leads to build failure.
And under CONFIG_OPTIMIZE=n 'inline' means 'always_inline'.

include/linux/compiler-gcc.h:

#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
    !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
#define inline		inline		__attribute__((always_inline)) notrace





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