[PATCH] sim: microblaze: breakpoint inst check + a couple of questions

Andrea Corallo via gdb-patches
2017-06-03T11:00:51Z

I have couple of questions related to microblaze debugging and its simulator:

When gdb add a breakpoint writes to memory the following word 0xb9cc0060, this is defined in gdb/microblaze-tdep.h:120

/* MICROBLAZE_BREAKPOINT defines the breakpoint that should be used.
Only used for native debugging. */
#define MICROBLAZE_BREAKPOINT {0xb9, 0xcc, 0x00, 0x60}

This brki instruction cause the cpu to jump to 0x60
I guess this is because there is supposed to start a monitor program in some configuration correct?
Because the simulator is not expecting any monitor program wouldn't be more appropriate to use hardware breakpoints instead?

The other question is: the simulator is checking against the presence of a brk instruction but not brki making gdb not stopping on the breakpoint just inserted.
Would make sense to check against both as in the following patch?

sim/microblaze/ChangeLog:
2017-06-01 Andrea Corallo <andrea_corallo@yahoo.it>

* interp.c (sim_engine_run): check also for breakpoint instruction brki.
---
sim/microblaze/interp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sim/microblaze/interp.c b/sim/microblaze/interp.c
index 75fc98b..d094a69 100644
--- a/sim/microblaze/interp.c
+++ b/sim/microblaze/interp.c
@@ -161,7 +161,7 @@ sim_engine_run (SIM_DESC sd,
oldpc = PC;
delay_slot_enable = 0;
branch_taken = 0;
- if (op == microblaze_brk)
+ if (op == microblaze_brk || op == brki)
sim_engine_halt (sd, NULL, NULL, NULL_CIA, sim_stopped, SIM_SIGTRAP);