[Attempted PATCH PXE]: Take 1 dies on gdb access

[RChan]

Below is an attempted PXE startup patch based on floppy startup
for pc/redboot. I hope to contribute the patch when it's working.
The patch works fine to the redboot prompt and redboot commands.
The machine reboots when gdb tries to load a program.

Anything obviously wrong with this patch?

What the patch does

1.  Re-use the floppy startup code; i.e. duplicate most of the files, change
load address from 0x00003000 to 0x00007C00
2. Avoid relocation to 0x00003000; leave everything at 0x00007C00
(I also tried another version that copied the NBP down to 0x3000 in case 
there
was some funky page alignment / free base mem issue - didn't help)
3. Skip sector loading and jump straight to protected mode setup code
4. NBP does not unload PXE UNDI (but this shouldn't be necessary right?)

What works:
1. Arriving at Redboot prompt and simple redboot commands.
2. Using memory dump I checked that the whole redboot.pxe file is loaded
correctly from 0x7C00 onwards.

What fails:
1. The moment gdb tries to load a program the system reboots.
2. Tried with RAM startup programs linked at 0x000108000 and 
0x000208000; both
cause reboots.

On the test machine:
Redboot floppy works
Redboot GRUB works
Redboot floppy image booted by PXELINUX/pxelinux.0/memdisk/ works - so 
methnks PXE loading
should work - the main difference is that pxelinux.0 does actually 
unload the PXE stack
before jumping to memdisk.

Any ideas? Thanks.

Cheers
Richard Chan


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