linux-kernel - Re: Re : [PATCH] Compressed ia32 ELF file generation for loading by Gujin 1/3

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Message-ID: <m1lkjbtaso.fsf@ebiederm.dsl.xmission.com>
Date:	Tue, 06 Feb 2007 11:12:39 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Etienne Lorrain <etienne_lorrain@...oo.fr>
Cc:	"H. Peter Anvin" <hpa@...or.com>, vgoyal@...ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: Re : [PATCH] Compressed ia32 ELF file generation for loading by Gujin 1/3

Etienne Lorrain <etienne_lorrain@...oo.fr> writes:

> H. Peter Anvin wrote:
>> Actually, as far as I can see, he has re-invented having a real-mode 
>> code chunk which then gets run before the protected-mode kernel.  We 
>> already have that!
>
>   I did not claim to have invented anything there, this is just a quite
>  simple C code to execute instead of the current real mode assembly:
>  it is a rewrite with obvious advantages/disadvantages.
>  New features are more that this real-mode function can return an error
>  to the bootloader to tell something to the user, so the user can select
>  another kernel with the right processor, another video mode... with
>  clean error messages - not a crash dump because this assembly
>  instruction is not for that processor.

Having an error handling compatibility that is backwards compatible sounds
interesting.

>   I am still saying that the bootloader knows the root filesystem to
>  be used by the kernel it loads, and that ELF is a clean format to
>  store different sections to be loaded into memory at predefined
>  addresses.

Yes.  Although when you think sections instead of segments I'm a little
worried.

>  Also there isn't any more kernel size limit.

I think as HPA points out we have gotten past that a long time
ago with the bzImage format.

With the right delicacy, and preserving backwards compatibility
with existing bootloaders I think we can achieve things.

The big issue is that sometimes bootloaders are a little bit brittle.

Eric
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