Re: [Bug 10732] REGRESSION: 2.6.26-rc2-git4: X server failed start onX61s laptop

[Jeremy Fitzhardinge <jeremy@goop.org>]

Hugh Dickins wrote:
> On Sat, 17 May 2008, Theodore Tso wrote:
>   
>> On Sat, May 17, 2008 at 08:32:38PM +0200, Gabriel C wrote:
>>     
>>>> Which repository is commit 1c12c4cf in?
>>>>         
>>> It is in linus-git tree , http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1c12c4cf9411eb130b245fa8d0fbbaf989477c7b
>>>       
>> ...post 2.6.26-rc2-git3.  For Linux kernels 2.6.26-rc2-git4 and
>> newer, you need to revert this commit or the X Server shipped with
>> Ubuntu Gutsy will die horribly when run on an X61s laptop with the
>> Intel 965GM video chipset.
>>
>> So the question is what's the right fix to keep the kernel compatible
>> with the X server, besides just reverting the commit entirely?
>>     
>
> [PATCH] x86: fix mprotect's NX handling on PAE
>
> 2.6.26-rc3 with CONFIG_X86_PAE may leave the NX bit set when PROT_EXEC
> is intending to clear it, causing irqbalance and others to segfault,
> and X startup to fail.
>
> This comes from an assumption in 1c12c4cf9411eb130b245fa8d0fbbaf989477c7b
> mprotect: prevent alteration of the PAT bits, that PTE_MASK is what it's
> supposed to be: whereas it's been wrong forever with PAE, staying 32-bit
> where 64-bit is needed.
>
> Jeremy Fitzhardinge already has patches to fix that in Ingo's tree;
> but if they're not considered 2.6.26 material, or people want a quick
> two-liner to get working, here's a shorter hack to fix up pte_modify.
>   

 From what I can tell, my patches haven't caused any regressions, and so 
if they fix a real bug we could consider them for .26.

    J