Re: [Bug 10732] REGRESSION: 2.6.26-rc2-git4: X server failed startonX61s laptop

From: Jeremy Fitzhardinge
Date: Mon May 19 2008 - 18:08:52 EST

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 ,;a=commit;h=1c12c4cf9411eb130b245fa8d0fbbaf989477c7b 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.

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