vm_map_lookup_clip_start
rv = vm_map_lookup_clip_start(map, start, &entry, &prev_entry);
rv = vm_map_lookup_clip_start(map, start, &start_entry, &prev_entry);
rv = vm_map_lookup_clip_start(map, start, &entry, &scratch_entry);
rv = vm_map_lookup_clip_start(map, saved_start,