PPC Bug Only
Call Stack
op_helper.c : do_tw()
op_helper.c : do_raise_exception_err()
op_helper.c : cpu_loop_exit()
op_helper.c : longjmp()
???
helper.c : do_interrupt()
Normally when an exception gets to do_interrupt(), env->nip is set to the
instruction after the one causing the exception.
However, a trap instruction arrives at the do_interrupt() with the
env->nip set at the instruction that caused the exception.
This causes an the SRR0 to get set incorrectly to one instruction back
when calling the exception handler.
I'm still learning the code so I'm still trying to figure out the right
fix since
its possible that more exceptions are affected. I've already verified that
forcing the env->nip forward for just the trap case
fixes the execution.
>From the middle of helper.c : do_interrupt()
....
case EXCP_TRAP:
....
goto store_current;
....
>From the bottom of helper.c : do_interrupt()
....
store_current:
/* save current instruction location */
*srr_0 = (env->nip - 4) & 0xFFFFFFFFULL;
break;
store_next:
/* save next instruction location */
*srr_0 = env->nip & 0xFFFFFFFFULL;
break;
....
I discovered this because I'm trying to get a vxworks debugger working
when the os is running.
Ohh ya, I've got a VxWorks 6.3 kernel up and running on PPC QEMU. 8-)
Custom BSP and all.
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