linux-kernel - [PATCH 02 of 36] x86: add memory clobber to save/loadsegment

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Message-Id: <2289309bb2cdf23bf825.1214367538@localhost>
Date:	Wed, 25 Jun 2008 00:18:58 -0400
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	xen-devel <xen-devel@...ts.xensource.com>,
	Stephen Tweedie <sct@...hat.com>,
	Eduardo Habkost <ehabkost@...hat.com>,
	Mark McLoughlin <markmc@...hat.com>, x86@...nel.org
Subject: [PATCH 02 of 36] x86: add memory clobber to save/loadsegment

Add "memory" clobbers to savesegment and loadsegment, since they can
affect memory accesses and we never want the compiler to reorder them
with respect to memory references.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 include/asm-x86/system.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
--- a/include/asm-x86/system.h
+++ b/include/asm-x86/system.h
@@ -157,14 +157,14 @@
 		     "jmp 2b\n"			\
 		     ".previous\n"		\
 		     _ASM_EXTABLE(1b,3b)	\
-		     : :"r" (value), "r" (0))
+		     : :"r" (value), "r" (0) : "memory")
 
 
 /*
  * Save a segment register away
  */
 #define savesegment(seg, value)				\
-	asm volatile("mov %%" #seg ",%0":"=rm" (value))
+	asm("mov %%" #seg ",%0":"=rm" (value) : : "memory")
 
 static inline unsigned long get_limit(unsigned long segment)
 {


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