linux-kernel - [PATCH] [25/99] i8k: Avoid lahf in 64-bit code

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Message-Id: <20110727214823.BF1732403FF@tassilo.jf.intel.com>
Date:	Wed, 27 Jul 2011 14:48:23 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	kronos.it@...il.com, jrickman@...migos.us, w5pny@...l.net,
	dz@...ian.org, khali@...ux-fr.org, gregkh@...e.de,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org,
	stable@...nel.org, tim.bird@...sony.com
Subject: [PATCH] [25/99] i8k: Avoid lahf in 64-bit code

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

------------------
From: Luca Tettamanti <kronos.it@...il.com>

commit bc1f419c76a2d6450413ce4349f4e4a07be011d5 upstream.

i8k uses lahf to read the flag register in 64-bit code; early x86-64
CPUs, however, lack this instruction and we get an invalid opcode
exception at runtime.
Use pushf to load the flag register into the stack instead.

Signed-off-by: Luca Tettamanti <kronos.it@...il.com>
Reported-by: Jeff Rickman <jrickman@...migos.us>
Tested-by: Jeff Rickman <jrickman@...migos.us>
Tested-by: Harry G McGavran Jr <w5pny@...l.net>
Cc: Massimo Dal Zotto <dz@...ian.org>
Signed-off-by: Jean Delvare <khali@...ux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 drivers/char/i8k.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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
@@ -138,8 +138,8 @@ static int i8k_smm(struct smm_regs *regs
 		"movl %%edi,20(%%rax)\n\t"
 		"popq %%rdx\n\t"
 		"movl %%edx,0(%%rax)\n\t"
-		"lahf\n\t"
-		"shrl $8,%%eax\n\t"
+		"pushfq\n\t"
+		"popq %%rax\n\t"
 		"andl $1,%%eax\n"
 		:"=a"(rc)
 		:    "a"(regs)
--
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