linux-kernel - [34-longterm 035/179] i8k: Avoid lahf in 64-bit code

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Message-ID: <1337048075-6132-36-git-send-email-paul.gortmaker@windriver.com>
Date:	Mon, 14 May 2012 22:12:11 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	<stable@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: [34-longterm 035/179] i8k: Avoid lahf in 64-bit code

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

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

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: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/char/i8k.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
index 4365717..1e116ac 100644
--- a/drivers/char/i8k.c
+++ b/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)
-- 
1.7.9.6

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