linux-kernel - Re: [Xen-devel] Re: [PATCH] xen: Disable stack protector for irq helper

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Date:	Mon, 12 Oct 2009 15:20:14 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Bastian Blank <bastian@...di.eu.org>, Ingo Molnar <mingo@...e.hu>,
	Ingo Molnar <mingo@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Stable Kernel <stable@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] Re: [PATCH] xen: Disable stack protector for irq
 helper

On 10/12/09 14:12, Bastian Blank wrote:
> On Mon, Oct 12, 2009 at 10:52:08PM +0200, Ingo Molnar wrote:
>   
>> ping - any update about this fix? Since it fixes a real crash it would 
>> be nice to fix this for .32.
>>     
> It works nicely.
>
> But IMHO this whole infrastructure should go for now, at least until gcc
> is able to produce functions with this call convention on its own. Or it
> needs to be restricted to only assembler functions. The other users of
> this may only work because the stack protector is already disabled for
> arch/x86/xen/mmu.o.
>   

No, the infrastructure is fine and completely compliant with the ABI
(which doesn't change with stackprotector).  But there were a couple of
interrupt-related calls which didn't use the infrastructure properly,
and failed to preserve edx properly; we'd gotten away with it until now
because the called functions were very simple and didn't end up using
edx - until stackprotector.

The fix is to use the infrastructure consistently.

I'll put together a suitable patch.

    J
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