linux-kernel - Re: [PATCH 1/3] module: deal with alignment issues in built-in module versions

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Message-ID: <20110217173136.GA28486@dtor-ws.eng.vmware.com>
Date:	Thu, 17 Feb 2011 09:31:36 -0800
From:	Dmitry Torokhov <dtor@...are.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Linux/m68k <linux-m68k@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 1/3] module: deal with alignment issues in built-in
 module versions

On Thu, Feb 17, 2011 at 09:24:58AM -0800, Linus Torvalds wrote:
> On Mon, Feb 7, 2011 at 4:02 PM, Dmitry Torokhov <dtor@...are.com> wrote:
> >
> > Moreover, as DaveM said, we can't reliably put structures into
> > independent objects, put them into a special section, and then expect
> > array access over them (via the section boundaries) after linking the
> > objects together to just "work" due to variable alignment choices in
> > different situations.
> 
> Why not?
> 
> That's what we normally do. Just align the "__modver", and you should
> be all good. What's the problem?

>From what I understand __attribute__ ((aligned(x))) only guarantees
minimum alignment, not exact (gapless) alignment. GCC seems to lay out
pointers in the section without gaps on all arches that we have.

Thanks.

-- 
Dmitry

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