Date: Wed, 14 Sep 2005 17:44:25 +0200
From: Andi Kleen <ak@suse.de>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Daniel Jacobowitz <dan@debian.org>,
       "Markus F.X.J. Oberhumer" <markus@oberhumer.com>,
       linux-kernel@vger.kernel.org, Andi Kleen <ak@suse.de>
Subject: Re: [PATCH] i386: fix stack alignment for signal handlers
Message-ID: <20050914154425.GM11338@wotan.suse.de>
References: <43273CB3.7090200@oberhumer.com> <Pine.LNX.4.58.0509131542510.26803@g5.osdl.org> <4327611D.7@oberhumer.com> <Pine.LNX.4.58.0509131649060.26803@g5.osdl.org> <20050914142204.GA19731@nevyn.them.org> <Pine.LNX.4.58.0509140753260.26803@g5.osdl.org>
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On Wed, Sep 14, 2005 at 07:55:53AM -0700, Linus Torvalds wrote:
> 
> 
> On Wed, 14 Sep 2005, Daniel Jacobowitz wrote:
> > 
> > The comment for the relevant bits of the GCC configuration says it won't
> > assume this for x86, but I believe that comment is out of date. I think
> > it'll assume 16-byte alignment on entrance to non-main() functions.
> 
> Well, that's kind of the point. We _do_ have the stack aligned on
> entrance, but it looks like gcc wants it _non-aligned_. It seems to want
> it offset by the "return address push" - ie it seems to expect that it was
> aligned before the "call", but entry into the next function will thus
> _never_ be aligned.
> 
> So the kernel actually seems to have it _too_ aligned right now. 

Yes it's wrong. I would recommend to apply Markus' patch for i386
and x86-64.

-Andi
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