linux-kernel - Re: [PATCH] x86: cleanup boot-heap usage

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Date:	Tue, 8 Apr 2008 11:39:22 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Alexander van Heukelum" <heukelum@...lshack.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"Mike Travis" <travis@....com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, heukelum@...tmail.fm
Subject: Re: [PATCH] x86: cleanup boot-heap usage

On Tue, Apr 8, 2008 at 3:54 AM, Alexander van Heukelum
<heukelum@...lshack.com> wrote:
> The kernel decompressor wrapper uses memory located beyond the
>  end of the image. This might lead to hard to debug problems,
>  but even if it can be proven to be safe, it is at the very
>  least unclean. I don't see any advantages either, unless you
>  count it not being zeroed out as an advantage. This patch
>  moves the boot-heap area to the bss segment.
>
>  Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>
>
>  ---
>
>  On Tue, Apr 08, 2008 at 10:23:54AM +0200, Ingo Molnar wrote:
>  > * 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?
the compressed image is copied to end of buff ( with extra code size
for from relocated: in .text to _end)
and do the on possition decompressed. .text section is near end.

YH
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