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Date: Tue, 14 Oct 2008 12:57:53 +1100
From: David Gibson <david@gibson.dropbear.id.au>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH] powerpc/boot: compare _start against ei.loadsize
	instead ei.memsize
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On Mon, Oct 13, 2008 at 11:15:26AM +0200, Sebastian Andrzej Siewior wrote:
> If the vmlinux binary in memory is larger than 4 MiB than it collides
> with the initial boot code which is linked at 4 MiB in case of cuBoot.
> If the the uncompressed image size (on disk size) is less than 4 MiB
> then it would fit. The difference between those two sizes is the bss
> section. In cuBoot we have the dtb embedded right after the data
> section so it is very likely that the reset of the bss section (in
> kernel's start up code) will overwrite the dtb blob. Therefore we
> reallocate the dtb. Something similar is allready done to the initrd.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

This patch looks sound to me.  It does strike me as only a stopgap
until we come up with some better way of managing the early memory,
preferably avoiding the magical fixed 4MiB (or whatever) offset.

Still, it looks safe - since it does check that the wrapper's malloc()
region can't collide with the kernel's BSS.  So, if this little slice
of extra BSS room is useful for the time being, I see no reason not to
apply the patch.

Acked-by: David Gibson <david@gibson.dropbear.id.au>

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson