Gdb Over Serial

[gregory.menke at gsfc.nasa.gov]

James Yates writes:

 > Has Anyone run rtems with GDB over a serial connection.  I am
 > currently porting RTEMS to a new SH2 platform and at the moment do
 > not have networking running.  I have my own bootloader which runs
 > from on-chip rom, provided that the checksum matches, it then
 > copies the contents of an external flash chip to ram, modifies the
 > VBR and jumps to the address contained in the first location of the
 > vector table. This bootloader also has a mode where it runs a
 > gdb_stub allowing software to be downloaded directly to ram via gdb
 > and run from there.
 > 
 >   I remember that when I first set up the gdb_stub, any application
 >   that ran from ram via the debugger would have to copy some of the
 >   vector table entries from rom into ram, basically so that the
 >   stub vectors weren't replaced. Will I have to do a similar thing
 >   here? Is there anything special about the vector table or can I
 >   copy the vector table entries as is?
 > 
 > I am close to getting rtems fully working on this platform and will
 > then be able to contribute back an SH2 7145 cpu port back into the
 > tree.
 > 
 > 	Many Thanks in advance.
 > 


Its known to work on the MIPS Mongoose- it should be portable to other
MIPS bsp's as well- I think bsp's for a number of other architectures
also support it.  

The particular setup process is quite dependant on the cpu, but
generally, the idea is to point whatever vector is responsible for
single stepping or breaks to the gdb stub routine, this is normally
done in bsp startup and afterwards left alone.

I don't think copying around vector tables is the right sort of thing
to be doing- perhaps you're trying to set it up too early in the RTEMS
boot process?

Gregm