GDB stub questions

[Mitchell Fang <mitchell.fang@gmail.com>]

I have a question about the GDB stub. Where does the stub run? Is it
on the host machine, the target board, or the JTAG controller.

I'm working on a project to connect GDB to a PowerPC4xx board using a
JTAG controller. It's suppose to generic enough to support different
types of controller (USB, ethernet, PCI...etc). I have .dll's for the
controllers. I would like to avoid having another program running to
convert the GDB remote protocol to JTAG commands.

Is it possible to edit GDB so that it automatically uses the JTAG
controller's .dll's directly? I am currently thinking no. From what I
understand about GDB, I think that I need to use a stub since I'm
doing a debugging remotely.  I've been reading the GDB user manual
about implementing a remote stub but not really getting it.  But I
don't totally understand how a stub works and where it is suppose to
run so I'm kinda stuck.  My thinking is that the stub is suppose to
run on the target board.  But then how do you build/make the stub an
application so that it's able to run on the target board?  I think I'm
just missing the overall picture and I wanted to make sure that I
start off in the right direction.

 Any input would be appreciated.

 Thanks,
 Mitchell