linux-kernel - [PATCH 1/2] x86/paravirt: don't restore second return reg

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Message-ID: <4983FB03.9030001@goop.org>
Date:	Fri, 30 Jan 2009 23:17:23 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Xen-devel <xen-devel@...ts.xensource.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Zachary Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ravikiran Thirumalai <kiran@...lemp.com>
Subject: [PATCH 1/2] x86/paravirt: don't restore second return reg

Impact: bugfix

In the 32-bit calling convention, %eax:%edx is used to return 64-bit
values.  Don't save and restore %edx around wrapped functions, or they
can't return a full 64-bit result.

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

===================================================================
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -1522,8 +1522,8 @@
 #define PV_RESTORE_REGS "popl %edx; popl %ecx;"
 
 /* save and restore all caller-save registers, except return value */
-#define PV_SAVE_ALL_CALLER_REGS PV_SAVE_REGS
-#define PV_RESTORE_ALL_CALLER_REGS PV_RESTORE_REGS
+#define PV_SAVE_ALL_CALLER_REGS		"pushl %ecx;"
+#define PV_RESTORE_ALL_CALLER_REGS	"popl  %ecx;"
 
 #define PV_FLAGS_ARG "0"
 #define PV_EXTRA_CLOBBERS


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