linux-kernel - Re: [PATCH] pop previous section in alternative.c

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Message-ID: <47FD5D42.5000603@zytor.com>
Date:	Wed, 09 Apr 2008 17:20:18 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>, akpm@...l.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Glauber de Oliveira Costa <gcosta@...hat.com>,
	Jan Beulich <jbeulich@...ell.com>, Andi Kleen <ak@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>, pinskia@....gnu.org
Subject: Re: [PATCH] pop previous section in alternative.c

Steven Rostedt wrote:
> On Wed, 9 Apr 2008, Steven Rostedt wrote:
> 
>> gcc expects all toplevel assembly to return to the original section type.
>> The code in alteranative.c does not do this. This caused some strange bugs
>> in sched-devel where code would end up in the .rodata section and when
>> the kernel sets the NX bit on all .rodata, the kernel would crash when
>> executing this code.
>>
>> This patch adds a .previous marker to return the code back to the
>> original section.
>>
> 
> Oh, and this would not be complete without giving Andrew Pinski complete
> credit for telling me it wasn't a gcc bug but a bug in the toplevel asm
> code in the kernel. ;-)
> 

In many ways it's kind of silly for this even to be in assembly, since 
all it is is a sequence of comma-separated byte values; I guess it was 
the easiest way to deal with it given the ".byte" prefix, but still...

	-hpa
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