linux-kernel - Re: [PATCH] x86: fix usage of bios intcall()

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Message-ID: <20090704021410.GA3050@localhost.localdomain>
Date:	Sat, 4 Jul 2009 11:14:13 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, tglx@...utronix.de, hpa@...or.com
Subject: Re: [PATCH] x86: fix usage of bios intcall()

Could someone review this patch?

On Wed, Jul 01, 2009 at 11:13:07AM +0900, Akinobu Mita wrote:
> Some intcall() misuses the input biosregs as output in
> cf06de7b9cdd3efee7a59dced1977b3c21d43732
> 
> This fixes the problem vga=ask boot option doesn't show enough modes.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> ---
>  arch/x86/boot/video-bios.c |    3 +--
>  arch/x86/boot/video-vesa.c |    4 ++--
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/boot/video-bios.c b/arch/x86/boot/video-bios.c
> index d660be4..49e0c18 100644
> --- a/arch/x86/boot/video-bios.c
> +++ b/arch/x86/boot/video-bios.c
> @@ -37,14 +37,13 @@ static int set_bios_mode(u8 mode)
>  	ireg.al = mode;		/* AH=0x00 Set Video Mode */
>  	intcall(0x10, &ireg, NULL);
>  
> -
>  	ireg.ah = 0x0f;		/* Get Current Video Mode */
>  	intcall(0x10, &ireg, &oreg);
>  
>  	do_restore = 1;		/* Assume video contents were lost */
>  
>  	/* Not all BIOSes are clean with the top bit */
> -	new_mode = ireg.al & 0x7f;
> +	new_mode = oreg.al & 0x7f;
>  
>  	if (new_mode == mode)
>  		return 0;	/* Mode change OK */
> diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
> index c700147..275dd17 100644
> --- a/arch/x86/boot/video-vesa.c
> +++ b/arch/x86/boot/video-vesa.c
> @@ -45,7 +45,7 @@ static int vesa_probe(void)
>  	ireg.di = (size_t)&vginfo;
>  	intcall(0x10, &ireg, &oreg);
>  
> -	if (ireg.ax != 0x004f ||
> +	if (oreg.ax != 0x004f ||
>  	    vginfo.signature != VESA_MAGIC ||
>  	    vginfo.version < 0x0102)
>  		return 0;	/* Not present */
> @@ -70,7 +70,7 @@ static int vesa_probe(void)
>  		ireg.di = (size_t)&vminfo;
>  		intcall(0x10, &ireg, &oreg);
>  
> -		if (ireg.ax != 0x004f)
> +		if (oreg.ax != 0x004f)
>  			continue;
>  
>  		if ((vminfo.mode_attr & 0x15) == 0x05) {
--
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