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

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Message-ID: <4526A66B.4030805@zytor.com>
Date:	Fri, 06 Oct 2006 11:54:35 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	vgoyal@...ibm.com
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...l.org>,
	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

Vivek Goyal wrote:
>>
> Hi Eric,
> 
> I have added cld in the regenerated patch below. 
> 

No, the cld needs to be earlier.  It turns out this isn't the first use 
of string instructions.

I think I am going to add DF=0 as a documented entry condition; it 
definitely seems all current Linux kernels require it.

> Also one more minor nit. stosb relies on being %es set properly. By the
> time control reaches loader_ok, i could not find %es being set explicitly
> hence I am assuming we are relying on bootloader to set it up for us. 
> 
> Maybe we can be little more paranoid and setup the %es before stosb. I
> have done this change too in the attached patch. Pleaese have a look.
> I know little about assembly code.

%es being set is part of the requirements list, although it *would* be 
better to not rely on any segment registers being set at all (only rely 
on %cs.)

	-hpa
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