Re: breakpoint for avr?

["Theodore A. Roth" <troth@openavr.org>]

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On Wed, 14 May 2003, Andrew Cagney wrote:

:) Theodore,
:)
:) Just noticed that the AVR target doesn't provide the BREAKPOINT_FROM_PC
:) method.
:)
:) Up until now the architecture vector providing a default
:) breakpoint_from_pc (it would internal error for the AVR case). I
:) suspect, up until now, this hasn't been a problem because the AVR was
:) always remote.
:)
:) Anyway, I've just posted a patch to always require breakpoint-from-pc
:) and this is causing the AVR grief.
:)
:) So, is there a breakpoint instruction, or should GDB allow targets that
:) have no breakpoint at all?

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):

(gdb) b main
Breakpoint 1 at 0x104: file tst.c, line 34.
(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.

Ted Roth

(Wondering if I should have posted this to gdb-patches instead. ;-)

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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,