linux-kernel - Re: [GIT PULL] x86 setup: correct booting on 486 (revised)

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Message-ID: <472FC401.9020202@zytor.com>
Date:	Mon, 05 Nov 2007 17:31:45 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Mikael Petterson <mikpe@...uu.se>
Subject: Re: [GIT PULL] x86 setup: correct booting on 486 (revised)

Jeremy Fitzhardinge wrote:
> 
> Another thing it would be nice to add is an elf-note-like notion so that
> the kernel can export arbitrary key/value data to the bootloader (ie,
> the converse of the bootloader->kernel value list).  Xen currently does
> this via ELF notes, but any semanically equivalent mechanism would do. 
> It's probably simpler than trying to work out how to mush bzimage and
> ELF together.
> 

I suspect all we need is an offset-pointer field pointing into the 
kernel image.  As far as the kernel build process is concerned, it 
becomes a section in the boot/compressed link script.  That offset then 
needs to get exported to the setup.elf link stage and there adjusted to 
become a file offset.

The ELF note format is sane enough, although it looks like it's not 
self-terminating, so we'd either need an offset and a length field, or 
adopt the convention that namesz = descsz = type = 0 terminates the 
block (I prefer the latter, myself.)  We also need the notes documented, 
obviously.

	-hpa

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