linux-kernel - Re: [PATCH 1/2] Use structs instead of hardcoded offsets in x86 boot decompressor.

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Date:	Fri, 23 May 2008 23:17:01 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rik van Riel <riel@...hat.com>
CC:	Kristian Høgsberg <krh@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] Use structs instead of hardcoded offsets in x86 boot
 decompressor.

Rik van Riel wrote:
> 
> People who wonder why these pointers never get initialized: they
> point to the zeropage, which of course lives at address zero.
> 
> /* The so-called "zeropage" */
> struct boot_params {
> 	struct screen_info screen_info;                 /* 0x000 */
>         struct apm_bios_info apm_bios_info;             /* 0x040 */
>         __u8  _pad2[12];                                /* 0x054 */
>         struct ist_info ist_info;                       /* 0x060 */
> 	...
> 

Uhm... except it doesn't live at address zero, at all.

It's called "zeropage" because we used to recycle it into 
empty_zero_page, a long long time ago.

The bootparms structure is pointed to by %esi being passed from the 
setup code to the decompressor to the kernel.

	-hpa
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