linux-kernel - [PATCH] [7/98] i8k: Tell gcc that *regs gets clobbered

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Message-Id: <20110727003459.1BD952403FF@tassilo.jf.intel.com>
Date:	Tue, 26 Jul 2011 17:34:59 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	jim876@...all.nl, andi@...stfloor.org, schwab@...ux-m68k.org,
	torvalds@...ux-foundation.org, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	tim.bird@...sony.com, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] [7/98] i8k: Tell gcc that *regs gets clobbered

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Jim Bos <jim876@...all.nl>

[ upstream commit 6b4e81db2552bad04100e7d5ddeed7e848f53b48 ]

More recent GCC caused the i8k driver to stop working, on Slackware
compiler was upgraded from gcc-4.4.4 to gcc-4.5.1 after which it didn't
work anymore, meaning the driver didn't load or gave total nonsensical
output.

As it turned out the asm(..) statement forgot to mention it modifies the
*regs variable.

Credits to Andi Kleen and Andreas Schwab for providing the fix.

Signed-off-by: Jim Bos <jim876@...all.nl>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Andreas Schwab <schwab@...ux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Index: linux-2.6.35.y/drivers/char/i8k.c
===================================================================
--- linux-2.6.35.y.orig/drivers/char/i8k.c
+++ linux-2.6.35.y/drivers/char/i8k.c
@@ -141,7 +141,7 @@ static int i8k_smm(struct smm_regs *regs
 		"lahf\n\t"
 		"shrl $8,%%eax\n\t"
 		"andl $1,%%eax\n"
-		:"=a"(rc)
+		:"=a"(rc), "+m" (*regs)
 		:    "a"(regs)
 		:    "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory");
 #else
@@ -166,7 +166,8 @@ static int i8k_smm(struct smm_regs *regs
 	    "movl %%edx,0(%%eax)\n\t"
 	    "lahf\n\t"
 	    "shrl $8,%%eax\n\t"
-	    "andl $1,%%eax\n":"=a"(rc)
+	    "andl $1,%%eax\n"
+	    :"=a"(rc), "+m" (*regs)
 	    :    "a"(regs)
 	    :    "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory");
 #endif
--
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