gdb-4.17; MS-DOS x m68k: stub problem

["Luc Le Huerou-Kerisel" <l dot le_huerou_kerisel at edixia dot fr>]

Hello,

I use GCC + GDB from object software, host MS-DOS, in
a cross 68k version (www.objsw.com\68k-gdb.zip downloaded on 07/22/99).
I try to use this gdb (68k-gdb.exe) for remote debug on a 68020 target
through a serial link.
I use the "stub" method to use remote debug (lsrc180.zip,
mvme-stub.c + mvme135-asm.s from libsrc\1.80\libgloss\m68k), and I can't
get rid off some breakpoint problems (every other command seems to
work well).
I set a breakpoint, and then issue a "continue" command.
GDB patches the code whith a "trap #1"=0x4e41 and issue a "c" command
to the stub.
When I reach the breakpoint, gdb indicates a PC of breakpoint+2;
There are two different behaviors when I continue from this point :
1) the instruction breaked is a 2-bytes instruction and
execution resume from the next instruction. The instruction breaked
is not executed.
2) the instruction breaked is more than a 2-bytes instruction and,
on the next "step" or "continue" command, target tries to execute
from the third byte of the breaked instruction. This produce an illegal
instruction trap.

I had to modify the mvme135-asm.s for the stub to work
(
bad code for vector setup :
  movel SYM(_catchException),reg
  replaced with
  movel &SYM(_catchException),reg
)
This indicates that this file is not used "as is" and need a patch anyway.

Do I use the wrong files for the stub method ? target are 68020, 68040 and
68060.
Is there a patch for the stub I use, or special commands on gdb to deal
whith those breakpoint problems ?
Is there a different method (like gdbserver) ? I did not find enough
information to implement gdbserver/68k/serial com.

Thank you for your help,

Luc LE HUEROU-KERISEL
EDIXIA
eMail: l.le_huerou_kerisel@edixia.fr