vector_cmd
void (**vector_cmd)(u_long, char *);
*oldpvec->vector_cmd = oldmon_w_cmd;
*romVectorPtr->vector_cmd = sunmon_vcmd;
*romVectorPtr->vector_cmd = sunmon_vcmd;
sunmon_vcmd = *rvec->vector_cmd;
*rvec->vector_cmd = v_handler;