linux-kernel - Re: [tip:x86/urgent] x86-32: Make sure the stack is set up before we use it

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Message-ID: <4D4CED97.7060302@zytor.com>
Date:	Fri, 04 Feb 2011 22:26:31 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kees Cook <kees.cook@...onical.com>
CC:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	castet.matthieu@...e.fr, tglx@...utronix.de, hpa@...ux.intel.com
Subject: Re: [tip:x86/urgent] x86-32: Make sure the stack is set up before
 we use it

On 02/04/2011 09:37 PM, Kees Cook wrote:
> On Fri, Feb 04, 2011 at 08:37:37PM -0800, H. Peter Anvin wrote:
>> On 02/04/2011 06:19 PM, Kees Cook wrote:
>>> This works for me doing CPU hotplugging on ia32, but on x86_64 it hangs.
>>> (Both boot, though.)
>>
>> I can't reproduce the failure here, and it's hard to see how this patch
>> would make a significant change on 64 bits.  Could you try reverting
>> *only* the head_64.S hunk and try it on your platform again?
> 
> With the head_64.S hunk dropped, it runs fine. My highly fine-tuned
> test-case is:
> 
>   while :; do ls -la / -R >/dev/null 2>/dev/null; done &
>   while :; do echo 0 > /sys/devices/system/cpu/cpu1/online ; echo 1 > /sys/devices/system/cpu/cpu1/online ; done &
> 
> Looks good from this end. Thanks!
> 

OK, that bothers me, because it would seem that something is accessing
data it shouldn't, but ok, it fixes it for now.  I'll update it in -tip.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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