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

Klaus S. Madsen
2008-02-28T19:24:34Z

On Thu, Feb 28, 2008 at 09:52:57 -0800, H. Peter Anvin wrote:
> Klaus S. Madsen wrote:
> >
> >Hope this helps.
> >
>
> What this seems to indicate is a segfault inside VM mode that causes it
> to exit to deliver the SIGSEGV, so without more information, such as
> signal context, there isn't much to know about it.
>
> It looks like the fault happens inside the VESA BIOS, specifically VBE
> function 3:
>
> --------V-104F03-----------------------------
> INT 10 - VESA SuperVGA BIOS - GET CURRENT VIDEO MODE
> AX = 4F03h
> Return: AL = 4Fh if function supported
> AH = status
> 00h successful
> BX = video mode (see #00083,#00084)
> bit 13: VBE/AF v1.0P accelerated video mode
> bit 14: linear frame buffer enabled (VBE v2.0+)
> bit 15: don't clear video memory
> 01h failed
> SeeAlso: AH=0Fh,AX=4E04h,AX=4F02h
>
> ... which normally would be a trivial function which only reads a couple
> of status words out of internal state and returns.
>
> ****
>
> 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?

--
Kind regards
Klaus S. Madsen