linux-kernel - Re: [PATCH 1/2] boot: increase stack size for kernel boot loader decompressor

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Message-ID: <20080408082354.GA13940@elte.hu>
Date:	Tue, 8 Apr 2008 10:23:54 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Alexander van Heukelum <heukelum@...lshack.com>
Cc:	Mike Travis <travis@....com>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, heukelum@...tmail.fm,
	Yinghai Lu <yhlu.kernel@...il.com>
Subject: Re: [PATCH 1/2] boot: increase stack size for kernel boot loader
	decompressor


* Alexander van Heukelum <heukelum@...lshack.com> wrote:

> I did see that the malloc space that the inflate code is using is 
> taken from _after_ the end of the bss. I don't see how this is 
> protected from being used/overwritten. Changing the stack size changes 
> the memory layout a bit... maybe you were so unlucky to create a 
> vmlinux image that was just barely smaller than some threshold and 
> increasing the stack size made the decompression/relocation area be 
> located somewhere else?
> 
> Test patch follows.

that's a really interesting theory.

FWIIW, i've been booting allyesconfig bzImages for a long time (with 
only minimal amount of drivers disabled - mostly old ISA ones that 
assume the presence of the real hardware), and they boot and work fine 
on both 32-bit and 64-bit typical whitebox PCs. That means huge bzImages 
that decompresses into a ~41 MB kernel image. I'd expect that to be a 
rather severe test of the decompressor.

	Ingo
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