[syslinux] Extract ElTorio No Emulation image and boot from PXE ?

[H. Peter Anvin]

Darryl L. Miles wrote:
> Extract ElTorio No Emulation image and boot from PXE ?
> 
> Is this possible, can PXELINUX + MEMDISC intercept the BIOS calls and 
> pretend to the 3rd party No Emulation image to be loading the data from 
> a CD (but instead copy from memory).
> 
> The driver would be a Real Mode driver and use some part of memory above 
> 1Mb to store the data.
> 
> I would expect this to be risky, especially if the No Emulation image 
> writes over the same (above 1Mb) location.  However maybe it would be 
> possible to run the BIOS driver it in a debug/checking mode which 
> checksumed its working area and the image and checked it before each 
> access, beeping and rebooting if it detected a corruption.  Maybe some 
> parameters could be used to shift where above 1Mb the image it copied to.
> 
> It would also be sure nice to print out a list of access the No 
> Emulation image makes of the BIOS to retrieve data.
> 

It would definitely be possible (and not even all that hard) to write a 
"MEMISO" driver similar to MEMDISK which would do not just No Emulation 
but could probably do the full El Torito stack just fine.

There is just one small problem: just about every OS out there, 
including DOS, stops using El Torito after booting and looks for the 
hardware directly.  At that point, you'd have to have either a 
MEMISO-specific CD-ROM driver or an El Torito real mode CD-ROM driver, 
or you're stuck.

	-hpa