linux-kernel - Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending

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Date:	Mon, 3 Mar 2008 13:17:35 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Klaus S. Madsen" <ksm@...rnemadsen.org>,
	Suspend-devel list <suspend-devel@...ts.sourceforge.net>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending

Hi!

> > > Klaus S. Madsen wrote:
> > >> open("/dev/mem", O_RDWR)                = 5
> > >> mmap2(NULL, 1282, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 5, 0) = 0
> > >> mmap2(0xa0000, 393216, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, 5, 0xa0) = 0xa0000
> > >                          ^^^^^^^^^^^^^^^^^^^^
> > >> close(5)                                = 0
> > >> ioperm(0, 0x400, 0x1)                   = 0
> > >> iopl(0x3)                               = 0
> > >> access("/sys/bus/pci", R_OK)            = 0
> > >> write(1, "Calling get_mode\n", 17)      = 17
> > >> vm86(0x1, 0xb7f14ccc, 0xb7f14830, 0xc000, 0x18b6 <unfinished ...>
> > >> --- SIGSEGV (Segmentation fault) @ 0 (0) ---
> > >> +++ killed by SIGSEGV (core dumped) +++
> > >
> > > This is the VGA BIOS being mapped, it's mapped PROT_READ|PROT_WRITE, but  
> > > no PROT_EXEC; if the kernel is NX-capable it *should* segfault trying to 
> > > execute out of this area, which is exactly what will happen when vm86 
> > > executes INT 10h.
> > >
> > > If we can find that mmap() in the s2ram source code and add PROT_EXEC 
> > > to it, it would be interesting.
> > 
> > Klaus, could you send your .config as well? Lets make sure that NX is 
> > even relevant in this context.
> Allright. The mmap in question is in the x86-common.c file in libx86,
> and adding PROT_EXEC to it solves the problem.

Ok, sw should probably fix that in s2ram... can you mail a patch to
me, and suspend-devel?

> I have attached my .config.
> 
> The only thing I don't understand is why this is suddenly a problem with
> 2.6.25, and not with 2.6.24? Is there a bug in 2.6.24 and previously
> that allows real-mode execution of non-executable pages?

It is strange indeed... Should it be traced as an regression?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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