linux-kernel - Re: [PATCH] gcov: fix __ctors

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Message-ID: <4A4381F5.5010405@linux.vnet.ibm.com>
Date:	Thu, 25 Jun 2009 15:56:05 +0200
From:	Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gcov: fix __ctors_start alignment

Heiko Carstens wrote:
> From: Heiko Carstens <heiko.carstens@...ibm.com>
> 
> The ctors section for each object file is eight byte aligned (on 64 bit).
> However the __ctors_start symbol starts at an arbitrary address dependent
> on the size of the previous sections.
> Therefore the linker may add some zeroes after __ctors_start to make sure
> the ctors contents are properly aligned. However the extra zeroes at the
> beginning aren't expected by the code. When walking the functions pointers
> contained in there and extra zeroes are added this may result in random
> jumps.
> So make sure that the __ctors_start symbol is always aligned as well.

Ack. And good find! :) Also with this patch applied, the x86_64 boot 
problem reported by Ingo Molnar no longer occurs.

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