[PATCH] AUX_DEVICE_INFO is one byte long, use 'movb'

[PATCH] AUX_DEVICE_INFO is one byte long, use 'movb'

[Diego Calleja]

Bugzilla #6552 says:

"In arch/i386/boot/setup.S, movw is used instead of movb for PS/2 mouse
information, although it is unsigned char. This does not harm, because
the jmp instruction overwritten by movw is used before executing movw,
and never be used again"

I've no idea if this is a real bug or how it gets fixed, so I'm submitting
it for review instead of letting it die of boredom in bugzilla. Aditionally
to i386, I've changed x86-64, which mirrors the same code.

Credits to Yoshinori K. Okuji, who found the problem and suggested a fix.


Signed-off-by: Diego Calleja <diegocg@gmail.com>


Index: 2.6/arch/i386/boot/setup.S
===================================================================
--- 2.6.orig/arch/i386/boot/setup.S	2006-08-01 01:04:34.000000000 +0200
+++ 2.6/arch/i386/boot/setup.S	2006-08-01 01:04:49.000000000 +0200
@@ -494,12 +494,12 @@
 	movw	%cs, %ax			# aka SETUPSEG
 	subw	$DELTA_INITSEG, %ax		# aka INITSEG
 	movw	%ax, %ds
-	movw	$0, (0x1ff)			# default is no pointing device
+	movb	$0, (0x1ff)			# default is no pointing device
 	int	$0x11				# int 0x11: equipment list
 	testb	$0x04, %al			# check if mouse installed
 	jz	no_psmouse
 
-	movw	$0xAA, (0x1ff)			# device present
+	movb	$0xAA, (0x1ff)			# device present
 no_psmouse:
 
 #if defined(CONFIG_X86_SPEEDSTEP_SMI) || defined(CONFIG_X86_SPEEDSTEP_SMI_MODULE)
Index: 2.6/arch/x86_64/boot/setup.S
===================================================================
--- 2.6.orig/arch/x86_64/boot/setup.S	2006-08-01 01:04:39.000000000 +0200
+++ 2.6/arch/x86_64/boot/setup.S	2006-08-01 01:05:26.000000000 +0200
@@ -526,12 +526,12 @@
 	movw	%cs, %ax			# aka SETUPSEG
 	subw	$DELTA_INITSEG, %ax		# aka INITSEG
 	movw	%ax, %ds
-	movw	$0, (0x1ff)			# default is no pointing device
+	movb	$0, (0x1ff)			# default is no pointing device
 	int	$0x11				# int 0x11: equipment list
 	testb	$0x04, %al			# check if mouse installed
 	jz	no_psmouse
 
-	movw	$0xAA, (0x1ff)			# device present
+	movb	$0xAA, (0x1ff)			# device present
 no_psmouse:
 
 #include "../../i386/boot/edd.S"

Re: [PATCH] AUX_DEVICE_INFO is one byte long, use 'movb'

[Andi Kleen]

On Tuesday 01 August 2006 01:47, Diego Calleja wrote:
> Bugzilla #6552 says:
> 
> "In arch/i386/boot/setup.S, movw is used instead of movb for PS/2 mouse
> information, although it is unsigned char. This does not harm, because
> the jmp instruction overwritten by movw is used before executing movw,
> and never be used again"
> 
> I've no idea if this is a real bug or how it gets fixed, so I'm submitting
> it for review instead of letting it die of boredom in bugzilla. Aditionally
> to i386, I've changed x86-64, which mirrors the same code.
> 
> Credits to Yoshinori K. Okuji, who found the problem and suggested a fix.

Queued thanks.

-Andi