[syslinux] interested in others' pre-7 NBP experience

[H. Peter Anvin]

McMahon, Chris wrote:
> Dirk Haus wrote: 
> 
> 
>>What would be the syntax to call other NBPs vom
>>pxelinux (and has someone already tried it with 3Com`s
>>Boot Image Editor "imgedit" bootstraps)? I haven`t
>>found a single word about this feature in the pre-7
>>tarball.
> 
> 
> 	Mr. Haus, I would very much like to know about your experience
> invoking another NBP from PXELINUX.  
> 	I'm trying and failing to invoke the FreeBSD "pxeboot" program from
> PXELINUX pre-7.  Here's what we know: 
> 	Both PXELINUX and pxeboot work properly when invoked from a normal
> PXE client using either PXE version 2.0 or version 2.1.  
> 	But invoking pxeboot.0 from PXELINUX causes a stack dump from
> pxeboot, and so far we haven't been able to discover the cause of the stack
> dump.  
> 	I'm trying to get more information from the pxeboot side, but it
> would be very interesting if we could discover the difference between how a
> normal PXE client invokes an NBP and how PXELINUX invokes an NBP.   
> 	Regardless of what happens, I'm very interested in your experience
> invoking another NBP from PXELINUX.  	
> 	And of course if I can help you, feel free to ask...
> 	-Chris    
> 

The more info we can get, the better!

PXELINUX tries very hard to preserve the state it was invoked with and 
invoke the subordinate NBP the same way.

Obviously, the PXE stack has been used in between, but PXELINUX will 
call "UDP CLOSE" before it finishes, which *should* put it back in its 
initial state.

All registers and the stack variables is preserved for the new NBP.  (It 
was in fact a bug in this area which I fixed in -pre7.)

	-hpa