linux-kernel - RE: Resume Issues :Exec of NX page, Synaptics Botchup

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Date:	Sun, 22 May 2011 19:49:18 -0700
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Parag Warudkar <parag.lkml@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>, Dmitry Torokhov <dtor@...l.ru>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: Resume Issues :Exec of NX page, Synaptics Botchup

> On Monday, May 23, 2011, Parag Warudkar wrote:
> >
> > On Sun, 22 May 2011, Linus Torvalds wrote:
> >
> > >
> > > Hmm. The "Code: " line is just full of complete garbage, so I think
> > > the real issue is that you really are trying to execute data.
> > >
> > > And that in turn seems to be because "setup_disablecpuid()" has
> > > actually been free'd, because it is marked as __init.
> > >
> > > Which is fine at the initial bootup, but not so fine at resume
> time,
> > > since it was free'd long long ago by then.
> > >
> > > And it definitely shouldn' t be called at resume time. There's
> > > something wrong there. That call trace is odd:
> > >
> > >   Call Trace:
> > >    [<ffffffff8148a119>] ? identify_cpu+0xd8/0x2d8
> > >    [<ffffffff8148a32d>] identify_secondary_cpu+0x14/0x1b
> > >    [<ffffffff8148bf0f>] smp_store_cpu_info+0x3c/0x3e
> > >    [<ffffffff8148c2ef>] start_secondary+0xf7/0x1d2
> > >
> > > because none of those should be calling "setup_disablecpuid()" at
> all.
> > >
> > > Hmm. In fact, RIP is "setup_disablecpuid+0x40/0x40", ie it is one
> past
> > > the _end_ of setup_disablecpuid.
> > >
> > > I suspect that is actually "setup_smep()" that got called, an dthat
> > > there was some garbage data in there that caused it to jump back a
> > > bit.
> > >
> > > Does the attached patch fix it?
> > >
> >
> > Now I get a different call trace for the same NX error. (And
> Synaptics is
> > completely dead this time - not attributable to the patch, it was
> dumb
> > luck perhaps that it wored last time.)
> 
> Any chance to try with commit de5397ad5b9ad22e2401c4dacdf1bb3b19c05679
> (x86, cpu: Enable/disable Supervisor Mode Execution Protection)
> reverted?
> 
> Rafael

de5397ad5b9ad22e2401c4dacdf1bb3b19c05679 shouldn't affect a system unless the CPU has SMEP feature which is unlikely available out there.

You can check if your CPU has "smep" feature in /proc/cpuinfo. Unlikely you will see the feature on your machine. Then the commit shouldn't cause the problem.

You can unconditionally disable SMEP by kernel option "nosmep".

Thanks.

-Fenghua
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