Re: Remote Debugging on IXDP425

[Ian Lance Taylor <ian@wasabisystems.com>]

"Stephen A. Witt" <sawitt@electra.rsc.raytheon.com> writes:

> I'm trying to get remote debugging using gdbserver on an IXDP425 target
> board. I've built a cross gdb-6.0 that executes on an i386 with the target
> set to arm-unknown-linux-gnu. The 'arm-unknown-linux-gnu-gdb' on my
> development machine does connect and talk to the gdbserver running on the
> target. I can start the program from gdb but breakpoints that I set don't
> break the program. I turned on remote debugging (set debug remote 1) and
> get the following:
> 
> (gdb) b main
> Sending packet: $m87a0,1#ca...Ack
> Packet received: e5
> Sending packet: $m87a0,1#ca...Ack
> Packet received: e5
> Breakpoint 1 at 0x87a0
> (gdb) c
> Continuing.
> Sending packet: $Z0,8ec0,1#43...Ack
> Packet received:
> Packet Z0 (software-breakpoint) is NOT supported
> Sending packet: $m8ec0,1#fa...Ack
> Packet received: 00
> Sending packet: $X8ec0,0:#1e...Ack
> Packet received:
> binary downloading NOT suppported by target
> Sending packet: $M8ec0,1:cc#da...Ack
> Packet received: OK
> Sending packet: $m87a0,1#ca...Ack
> Packet received: e5
> Sending packet: $M87a0,1:cc#aa...Ack
> Packet received: OK
> Sending packet: $Hc0#db...Ack
> Packet received: OK
> Sending packet: $c#63...Ack
> 
> 
> So the software-breakpoint NOT supported would seem to be my problem. Any
> information about how I fix this?

That isn't the problem by itself.  If the remote target doesn't
support `Z0', then gdb will try to set a breakpoint by writing
directly to memory.  That's what you see it doing with the `m' request
(read memory) followed by the 'X' request (binary download, which is
also not supported), followed by the 'M' request (write memory).  The
sequence above winds up writing the byte 0xcc to address 0x8ec0.
Similarly, it writes the byte 0xcc to the address 0x87a0.

So this is all fine.  At least, it would be fine if a one-byte 0xcc
were an ARM breakpoint instruction.  Unfortunately, 0xcc is an i386
breakpoint instruction.  So I would say that you are running a gdb
configured for an i386 target and connecting to a gdbserver running on
an ARM.  Don't do that.

Ian