rem: return 0;
add: return B_OK;
context: unmap_tmap(vm_translation_map *map, addr_t start, addr_t end){	page_table_entry *entry;	start = ROUNDOWN(start, PAGE_SIZE);	end = ROUNDUP(end, PAGE_SIZE);	dprintf("vm_translation_map.unmap_tmap: start 0x%lx, end 0x%lx\n", start, end);	while (start < end) {		entry = lookup_pagetable_entry(map, start);		if (entry) {			// unmap this page			entry->valid = 0;			arch_cpu_global_TLB_invalidate();			map->map_count--;		}		start += B_PAGE_SIZE;	}	return 0;}