linux-kernel - Re: [PATCH 12/12] i386 boot: Add an ELF header to bzImage

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Date:	Thu, 05 Oct 2006 09:35:02 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andrew Morton <akpm@...l.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, vgoyal@...ibm.com,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Reloc Kernel List <fastboot@...ts.osdl.org>, ak@...e.de,
	horms@...ge.net.au, lace@...kratochvil.net, magnus.damm@...il.com,
	lwang@...hat.com, dzickus@...hat.com, maneesh@...ibm.com
Subject: Re: [PATCH 12/12] i386 boot: Add an ELF header to bzImage

"H. Peter Anvin" <hpa@...or.com> writes:

> Andrew Morton wrote:
>> On Thu, 05 Oct 2006 00:13:12 -0600
>> ebiederm@...ssion.com (Eric W. Biederman) wrote:
>>
>>> Do things work better if you don't specify a vga=xxx mode?
>> yes, without vga=0x263 it boots.
>
> vga= actually patches a specific offset in the boot sector.  We don't actually
> have 512 bytes, we have some 500-ish bytes plus a small patch area at the end.

>From video.S
It uses offset 0 in the boot sector.  We have 497 bytes that can be used,
before we call setup.S after that setup.S considers the entire bootsector
it's own.

/* Positions of various video parameters passed to the kernel */
/* (see also include/linux/tty.h) */
#define PARAM_CURSOR_POS	0x00
#define PARAM_VIDEO_PAGE	0x04
#define PARAM_VIDEO_MODE	0x06
#define PARAM_VIDEO_COLS	0x07
#define PARAM_VIDEO_EGA_BX	0x0a
#define PARAM_VIDEO_LINES	0x0e
#define PARAM_HAVE_VGA		0x0f
#define PARAM_FONT_POINTS	0x10

#define PARAM_LFB_WIDTH		0x12
#define PARAM_LFB_HEIGHT	0x14
#define PARAM_LFB_DEPTH		0x16
#define PARAM_LFB_BASE		0x18
#define PARAM_LFB_SIZE		0x1c
#define PARAM_LFB_LINELENGTH	0x24
#define PARAM_LFB_COLORS	0x26
#define PARAM_VESAPM_SEG	0x2e
#define PARAM_VESAPM_OFF	0x30
#define PARAM_LFB_PAGES		0x32
#define PARAM_VESA_ATTRIB	0x34
#define PARAM_CAPABILITIES	0x36

Eric
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