[syslinux] Returning to syslinux bootloader

[H. Peter Anvin]

Michael Brown wrote:
> 
> FWIW, I have experimented with returning to the gPXE bootloader from an MS-DOS 
> instance booted via iSCSI.  gPXE captures the INT18/INT19 vectors so that it 
> can continue cleanly in the case of a failed iSCSI boot.  It is possible to 
> abuse this in DOS by writing a reboot.com executable that just calls INT19.  
> It does kind of work, but it's not hugely reliable, because DOS will have 
> edited the interrupt vector table, etc. and so the machine is left in a 
> pretty unsafe state for booting a subsequent OS without a reset.
> 

If it was only the IRQ table it wouldn't be so bad -- it's only a
kilobyte to save and restore, after all.  However, MS-DOS screws with
BIOS state all over the place, in weird ways.

	-hpa

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