SEGMENT_MASK
*kaddr = (char *)USER_ADDR + ((uintptr_t)uaddr & ~SEGMENT_MASK);
*kaddr = (char *)USER_ADDR + ((uintptr_t)uaddr & ~SEGMENT_MASK);
ASSYM(SEGMENT_MASK, SEGMENT_MASK);
(frame->dar & SEGMENT_MASK) == USER_ADDR) {