sys/uvm/uvm_map.c

3505 			panic("uvm_share: encountered a submap (illegal)");
3590 	/* gain reference to object backing the map (can't be a submap). */
3854 			panic("fork: encountered a submap during fork "
3963  * uvm_map_submap: punch down part of a map into a submap
3972  * => to remove a submap, use uvm_unmap() on the main map
3973  *	and then uvm_map_deallocate() the submap.
3975  * => submap must have been init'd and have a zero reference count.
3980     struct vm_map *submap)
4002 		entry->object.sub_map = submap;
4004 		uvm_map_reference(submap);