The following instructions trigger this hap (by processor class):
MIPS: eret and deret
PowerPC (32): rfi and rfci
PowerPC (64): rfi, rfid and hrfid
SH: rte
SPARC: done and retry
x86/x86-64: The iret family.
The exception_number parameter is only valid for SPARC processors.
void (*)(lang_void *callback_data,
conf_object_t *trigger_obj,
int64 exception_number);