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

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Message-ID: <20080228194920.GJ17932@hjernemadsen.org>
Date:	Thu, 28 Feb 2008 20:49:20 +0100
From:	"Klaus S. Madsen" <ksm@...rnemadsen.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending

On Thu, Feb 28, 2008 at 11:31:13 -0800, H. Peter Anvin wrote:
> Klaus S. Madsen wrote:
> >>
> >>Typically, when the kernel reflects an error in VM86 mode it will update 
> >>the structure in memory (in your case, the vm86plus_struct) to reflect 
> >>the context.  Would it be possible for you to read it out?
> >Hmm. As far as I can tell, its actually using the vm86old system call?
> >That's at least what the comment in libx86 states.
> >
> >However the contents of struct vm86_struct after the segfault is:
> >
> >(gdb) print context.vm
> >$2 = {regs = {ebx = 0, ecx = 0, edx = 0, esi = 0, edi = 0, ebp = 0, 
> >    eax = 20227, __null_ds = 0, __null_es = 0, __null_fs = -1071579136, 
> >    __null_gs = 0, orig_eax = -1, eip = 6326, cs = 49152, __csh = 0, 
> >    eflags = 209410, esp = 4090, ss = 256, __ssh = 0, es = 0, __esh = 0, 
> >    ds = 64, __dsh = 0, fs = 0, __fsh = 0, gs = 0, __gsh = 0}, flags = 0, 
> >  screen_bitmap = 0, cpu_type = 0, int_revectored = {__map = {0, 0, 0,0, 
> >  0, 0, 0, 2147483648}}, int21_revectored = {__map = {0, 0, 0, 0, 0, 
> >      0, 0, 0}}}
> >
> >My version of glibc does not seem to have vm86old declared, so I haven't
> >tried to remove the assembly code.
> >
> >Should I try to change it to use vm86, instead of vm86old?
> >
> 
> Yes, that would probably be a good idea.  To some degree, I guess it 
> really has nothing to do with the more fundamental issue, but it's 
> somewhat odd.
Ok. I tried changing the code from the assembly to do:

vm86(VM86_ENTER, vm)

instead. vm the vm86plus_struct structure fill in exactly the same way
as vm86_struct.

The output from GDB after the segfault is exactly the same as
previously, and all the fields in vm86plus_info_struct is zero.

> I'll pick apart the state above looking for fishiness as soon as I get 
> back from lunch.
Great, thanks.

-- 
Kind regards
	Klaus S. Madsen
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