[syslinux] Crash with core32 (syslinux-3.81-pre12-68-g4a211f6)

[H. Peter Anvin]

Sebastian Herbszt wrote:
> I got a qemu crash and errors reported in bochs while trying to get
> latest core32
> branch working (pxelinux):
> 
> bochsout.txt:
> 
> 00540593725e[CPU0 ] write_virtual_checks(): no write access to seg
> 00540593814e[CPU0 ] fetch_raw_descriptor: GDT: index (3a27)744 > limit (2f)
> 00540593903e[CPU0 ] fetch_raw_descriptor: LDTR.valid=0
> ...
> 00540644544e[CPU0 ] fetch_raw_descriptor: LDTR.valid=0
> 00540644633e[CPU0 ] fetch_raw_descriptor: GDT: index (3137)626 > limit (2f)
> 00540644666e[CPU0 ] prefetch: EIP [00010000] > CS.limit [0000ffff]
> 

It Works For Me[TM] in KVM...

In Bochs, one can often set a simulation time breakpoint with the "sba"
command (the number at the front is the simulation time) and execute
until a little bit before the failure ... it makes it easier to see.

In both cases it looks like it's jumping through an invalid pointer.

	-hpa

P.S. Make sure you have the latest core32 branch... it was seriously
broken until my changes this morning.

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.