[SeaBIOS] SeaVGABIOS crash on FC13 X11

Kevin O'Connor kevin at koconnor.net
Sun Mar 10 02:15:38 CET 2013

On Sun, Mar 10, 2013 at 01:09:35AM +0000, Julian Pidancet wrote:
> On Sun, Mar 10, 2013 at 12:09 AM, Kevin O'Connor <kevin at koconnor.net> wrote:
> >
> > Julian - I know you played with SeaVGABIOS and X11 a bit a year or so
> > ago.  Any thoughts on what is happening?
> >
> Hi Kevin,
> I have not really followed the latest developments on SeaBIOS, so I'm
> not sure I'll be very useful. But I can try to take a look at it.
> I seem to remember that qemu uses SeaVGABIOS now. If I try to compile
> a recent qemu and launch the fedora liveCD, will it exhibit the issue
> ?

Not much has changed in the SeaVGABIOS area.  I believe QEMU can build
SeaVGABIOS, but it is not the default vgabios.

> The last time I investigated on an issue with SeaVGABIOS and X11, it
> was because the 16bit code emulator of X11 wasn't handling properly
> certain prefixed instructions. I think we worked around the issue by
> post-processing the assembly output of the compilation to replace the
> problematic instructions with non-prefixed instructions.
> I also tried to send several times a patch on the Xorg mailing list to
> address that issue, but never managed to attract anyone's attention.
> It could be useful if someone volunteered to try sending them again.
> According to the backtrace you sent, the crash seems to be located in
> the libint10 module. The issue I worked on was in "x86emu". I'm not
> sure how these two parts relate to each other, but we could well be
> facing something very similar.
> The first think I would try, is to check in the vga bios assembly and
> make sure we're correctly replacing all of the "sensitive" prefixed
> x86 instructions. Some new form of one of these instruction may have
> made it's way in the VGA rom code.

Yeah - I thought the same thing and looked into that.  The assembler
translation is still being performed and I don't see anything that
looks suspicious.


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