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Date: Fri, 06 Oct 2006 11:54:35 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: vgoyal@in.ibm.com
CC: "Eric W. Biederman" <ebiederm@xmission.com>, Andrew Morton <akpm@osdl.org>,
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Subject: Re: [PATCH 12/12] i386 boot: Add an ELF header to bzImage
References: <20061003170032.GA30036@in.ibm.com> <20061003172511.GL3164@in.ibm.com> <20061003201340.afa7bfce.akpm@osdl.org> <m1vemzbe4c.fsf@ebiederm.dsl.xmission.com> <20061004214403.e7d9f23b.akpm@osdl.org> <m1ejtnb893.fsf@ebiederm.dsl.xmission.com> <20061004233137.97451b73.akpm@osdl.org> <m14pui4w7t.fsf@ebiederm.dsl.xmission.com> <20061005235909.75178c09.akpm@osdl.org> <m1bqop38nw.fsf@ebiederm.dsl.xmission.com> <20061006183846.GF19756@in.ibm.com>
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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