linux-kernel - Re: [PATCH] x86 boot: document for 32 bit boot protocol

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Date:	Tue, 23 Oct 2007 18:57:16 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Huang, Ying" <ying.huang@...el.com>
CC:	Andi Kleen <ak@...e.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86 boot: document for 32 bit boot protocol

Huang, Ying wrote:
> This patch documents the 32-bit boot protocol of x86. It has been used
> by Kexec and LinuxBIOS. This patch is based on the proposal of Peter
> Anvin.

> +At entry, the CPU must be in 32-bit protected mode with paging
> +disabled; a GDT must be loaded with the descriptors for selectors
> +__BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat
> +segment; __BOOS_CS must have execute/read permission, and __BOOT_DS
> +must have read/write permission; CS must be __BOOT_CS and DS, ES, SS
> +must be __BOOT_DS; interrupt must be disabled; %esi must hold the base
> +address of the struct boot_params; %ebp, %edi must be zero.

You missed the (ironically the only one currently existing) constraint 
that %ebx must be zero.

	-hpa
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