Problems implementing (netboot) tagged image support in grub

[Hans-Peter Jansen]

Hi,

since I received no answers on my previous post, I'm currently trying to 
fix the problem myself. After digging through sources and specs, I 
started hacking grub and test in a vmware session, loading an etherboot 
lance.fd0 floppy image, which loads the patched nbgrub and a 
corresponding configuration from the server. Loading a Linux kernel 
works as expected.

I enhanced stage2/boot.c to detect the tagged image magic and to decode 
the contained segments.

Moving the first 512 bytes from MULTIBOOT_SEARCH to 0x10000 succeeded.
Moving the first segment (3584 bytes, also completely contained in 
buffer) to 0x10400 failed so far with a vmware tripple fault error, no 
matter if I use
        grub_memmove(RAW_ADDR(cur_addr), data, i)
or a self written copy loop. Crash happens repeatable at 0x10b01.
 
Does somebody has an idea, what's the problem to use this memory around 
0x10b00? Is there any grub memory layout documentation available?

Again, any enlightenment is highly appreciated.

TIA,
Pete