Re: breakpoint for avr?

[Andrew Cagney <ac131313@redhat.com>]

> Ok, I added the BREAKPOINT_FROM_PC method for the avr and as I
> suspected it doesn't interfere with remote targets (unless I am over
> looking something):

Right.  If the remote target doesn't support the Z packet, GDB will use 
BREAKPOINT_FROM_PC and then insert breakpoints in memory.  Try
> (gdb) b main
> Breakpoint 1 at 0x104: file tst.c, line 34.

Do a:

(gdb) set remote Z-packet off

here.  You'll then see GDB doing memory writes.

> (gdb) c
> Continuing.
> Sending packet: $Z0,104,2#a9...Ack
> Packet received: OK
> Packet Z0 (software-breakpoint) is supported
> Sending packet: $Hc0#db...Ack
> Packet received:
> Sending packet: $c#63...Ack
> Packet received: T0520:02;21:ff10;22:04010000;
> Sending packet: $g#67...Ack
> Packet received: 00000000000000000000000000000000000100000000000000000001ff100a0102ff1004010000
> Sending packet: $mfc,8#9a...Ack
> Packet received: cfefd0e1debfcdbf
> Sending packet: $z0,104,2#c9...Ack
> Packet received: OK
> 
> Breakpoint 1, main () at tst.c:34
> (gdb)
> 
> 
> Andrew, does the attached patch help things with your patch? If so,
> I'll go ahead and commit it.

Yes, it will avoid the problem.  My patch is at:
http://sources.redhat.com/ml/gdb-patches/2003-05/msg00211.html

Andrew


> 2003-05-14  Theodore A. Roth  <troth@openavr.org>
> 
> 	* avr-tdep.c (avr_breakpoint_from_pc): New function.
> 	(avr_gdbarch_init): Set breakpoint_from_pc method.
> 
> Index: avr-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/avr-tdep.c,v
> retrieving revision 1.47
> diff -u -p -r1.47 avr-tdep.c
> --- avr-tdep.c	14 May 2003 20:09:14 -0000	1.47
> +++ avr-tdep.c	14 May 2003 21:47:19 -0000
> @@ -1091,6 +1091,18 @@ avr_push_arguments (int nargs, struct va
>    return sp;
>  }
>  
> +/* Not all avr devices support the BREAK insn. Those that don't should treat
> +   it as a NOP. Thus, it should be ok. Since the avr is currently a remote
> +   only target, this shouldn't be a problem (I hope). TRoth/2003-05-14  */
> +
> +const unsigned char *
> +avr_breakpoint_from_pc (CORE_ADDR * pcptr, int *lenptr)
> +{
> +    static unsigned char avr_break_insn [] = { 0x95, 0x98 };
> +    *lenptr = sizeof (avr_break_insn);
> +    return avr_break_insn;
> +}
> +
>  /* Initialize the gdbarch structure for the AVR's. */
>  
>  static struct gdbarch *
> @@ -1189,6 +1201,7 @@ avr_gdbarch_init (struct gdbarch_info in
>    set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
>  
>    set_gdbarch_decr_pc_after_break (gdbarch, 0);
> +  set_gdbarch_breakpoint_from_pc (gdbarch, avr_breakpoint_from_pc);
>  
>    set_gdbarch_function_start_offset (gdbarch, 0);
>    set_gdbarch_remote_translate_xfer_address (gdbarch,