vm: implement private and shared address space mappings

whether a mapping is private or shared determines how the mapping is handled
when a task is duplicated.

vm/vm-controller.c

@@ -162,7 +162,7 @@ kern_status_t vm_controller_recv(
 		out->req_length = req->req_length;
 		break;
 	case VM_REQUEST_ATTACH:
-		out->req_src_vmo = req->req_object->vo_src_key;
+		out->req_src_vmo = req->req_object->vo_key;
 		break;
 	default:
 		break;
@@ -255,7 +255,6 @@ kern_status_t vm_controller_finish_attach(
 
 	vm_object_lock(vmo);
 	vmo->vo_key = new_key;
-	vmo->vo_src_key = 0;
 	vmo->vo_flags &= ~VMO_LAZY_ATTACH;
 	vm_object_unlock(vmo);