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Date: Fri, 12 Feb 2016 18:10:37 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
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Subject: Re: [PATCH 00/33] Compile-time stack metadata validation
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 <56BDB5A8.9030006@suse.cz>
 <20160212144543.GA29004@treble.redhat.com>
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On Fri, Feb 12, 2016 at 08:45:43AM -0600, Josh Poimboeuf wrote:
> On Fri, Feb 12, 2016 at 11:36:24AM +0100, Jiri Slaby wrote:
> 
> This seems like a real frame pointer bug caused by the following line in
> arch/x86/include/asm/preempt.h:
> 
>   # define __preempt_schedule() asm ("call ___preempt_schedule")

The purpose there is that:

	preempt_enable();

turns into:

	decl	__percpu_prefix:__preempt_count
	jnz	1f:
	call	___preempt_schedule
1:

See arch/x86/include/asm/preempt.h:__preempt_count_dec_and_test()