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/address-space.c

@@ -706,6 +706,7 @@ kern_status_t address_space_map(
 	struct vm_object *object,
 	off_t object_offset,
 	size_t length,
+	vm_flags_t flags,
 	vm_prot_t prot,
 	virt_addr_t *out)
 {
@@ -763,6 +764,7 @@ kern_status_t address_space_map(
 	area->vma_space = root;
 	area->vma_object = object;
 	area->vma_prot = prot;
+	area->vma_flags = flags;
 	area->vma_object_offset = object_offset;
 	area->vma_base = map_address;
 	area->vma_limit = map_address + length - 1;
@@ -1215,6 +1217,7 @@ static struct vm_area *area_duplicate(struct vm_area *area)
 	}
 
 	out->vma_prot = area->vma_prot;
+	out->vma_flags = area->vma_flags;
 	out->vma_object_offset = area->vma_object_offset;
 	out->vma_base = area->vma_base;
 	out->vma_limit = area->vma_limit;
@@ -1281,7 +1284,8 @@ static kern_status_t prepare_duplicate_areas(
 		struct vm_object *src_vmo = tmp_area->vma_object;
 		vm_object_lock(src_vmo);
 
-		struct vm_object *dest_vmo = NULL;
+		struct vm_object *dest_vmo_link = NULL;
+		struct vm_object *dest_vmo_cow = NULL;
 		struct queue_entry *cur_entry
 			= queue_first(&src_vmo->vo_mappings);
 
@@ -1312,6 +1316,13 @@ static kern_status_t prepare_duplicate_areas(
 				continue;
 			}
 
+			struct vm_object *dest_vmo = NULL;
+			if (src_area->vma_flags & VM_SHARED) {
+				dest_vmo = dest_vmo_link;
+			} else {
+				dest_vmo = dest_vmo_cow;
+			}
+
 			if (!dest_vmo) {
 				tracek("[%zx-%zx %x] creating COW duplicate of "
 				       "vmo %p",
@@ -1319,7 +1330,18 @@ static kern_status_t prepare_duplicate_areas(
 				       src_area->vma_limit,
 				       src_area->vma_prot,
 				       src_vmo);
-				dest_vmo = vm_object_duplicate_cow(src_vmo);
+
+				if (src_area->vma_flags & VM_SHARED) {
+					dest_vmo_link = src_vmo;
+					object_ref(&dest_vmo_link->vo_base);
+
+					dest_vmo = dest_vmo_link;
+				} else {
+					dest_vmo_cow = vm_object_duplicate_cow(
+						src_vmo);
+					dest_vmo = dest_vmo_cow;
+				}
+
 				tracek("[%zx-%zx %x] created COW duplicate of "
 				       "vmo %p -> %p",
 				       src_area->vma_base,
@@ -1329,11 +1351,20 @@ static kern_status_t prepare_duplicate_areas(
 				       dest_vmo);
 			}
 
+			object_ref(&dest_vmo->vo_base);
 			dest_area->vma_object = dest_vmo;
 			update_area_pte_cow(src, dest, src_area);
 			cur_entry = queue_next(cur_entry);
 		}
 
+		if (dest_vmo_link) {
+			object_unref(&dest_vmo_link->vo_base);
+		}
+
+		if (dest_vmo_cow) {
+			object_unref(&dest_vmo_cow->vo_base);
+		}
+
 		vm_object_unlock(src_vmo);
 
 		cur_node = btree_next(cur_node);

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);
 

vm/vm-object.c

@@ -290,8 +290,7 @@ struct vm_object *vm_object_duplicate_cow(struct vm_object *vmo)
 	memcpy(out->vo_name, vmo->vo_name, sizeof out->vo_name);
 	out->vo_flags = vmo->vo_flags | VMO_LAZY_ATTACH;
 	out->vo_ctrl = vmo->vo_ctrl;
-	out->vo_key = 0;
-	out->vo_src_key = vmo->vo_key;
+	out->vo_key = vmo->vo_key;
 	out->vo_prot = vmo->vo_prot;
 	out->vo_size = vmo->vo_size;
 	memcpy(out->vo_name, vmo->vo_name, sizeof vmo->vo_name);