vm: region: refactor to use offsets rather than absolute addresses

include/mango/vm-region.h

@@ -5,9 +5,9 @@
 #include <mango/pmap.h>
 #include <mango/vm.h>
 
-#define VM_REGION_NAME_MAX        64
+#define VM_REGION_NAME_MAX   64
 
-#define VM_REGION_ANY_MAP_ADDRESS ((virt_addr_t) - 1)
+#define VM_REGION_ANY_OFFSET ((off_t) - 1)
 
 struct vm_region;
 struct vm_object;
@@ -22,8 +22,8 @@ struct vm_region_entry {
 	struct btree_node e_node;
 	struct vm_region_entry *e_parent;
 	enum vm_region_entry_type e_type;
-	/* absolute virtual address of the entry */
-	virt_addr_t e_base_address;
+	/* offset in bytes of this entry within its immediate parent. */
+	off_t e_offset;
 	/* size of the entry in bytes */
 	size_t e_size;
 };
@@ -66,59 +66,48 @@ struct vm_region {
 
 extern kern_status_t vm_region_type_init(void);
 
+/* create a new vm-region, optionally within a parent region.
+ * `offset` is the byte offset within the parent region where the new region
+ * should start.
+ * if no parent is specified, `offset` is the absolute virtual address of the
+ * start of the region.
+ * in both cases, `len` is the length of the new region in bytes. */
 extern kern_status_t vm_region_create(
 	struct vm_region *parent,
 	const char *name,
-	virt_addr_t base,
+	off_t offset,
 	size_t len,
 	enum vm_prot prot,
 	struct vm_region **out);
 
-/* find the child region that has jurisdiction over the specified virtual
- * address. returns the lowest-nested region that covers the specified virtual
- * address. */
-extern struct vm_region *vm_region_find_child(
-	struct vm_region *region,
-	virt_addr_t addr);
-
-/* find the child region that has jurisdiction over the specified virtual
- * address area. returns the lowest-nested region that covers the specified
- * virtual address area. the area must be fully contained within a region, with
- * no partial overlaps. if an area is covered by multiple regions, or is only
- * partially within a region, returns NULL. */
-extern struct vm_region *vm_region_find_child_for_area(
-	struct vm_region *region,
-	virt_addr_t addr,
-	size_t len);
-extern struct vm_region_mapping *vm_region_find_mapping(
-	struct vm_region *region,
-	virt_addr_t addr);
-
+/* map a vm-object into a vm-region.
+ * [region_offset,length] must fall within exactly one region, and cannot span
+ * multiple sibling regions.
+ * if [region_offset,length] falls within a child region, the map operation
+ * will be transparently redirected to the relevant region.
+ * `prot` must be allowed both by the region into which the mapping is being
+ * created AND the vm-object being mapped. */
 extern kern_status_t vm_region_map_object(
 	struct vm_region *region,
-	virt_addr_t map_address,
+	off_t region_offset,
 	struct vm_object *object,
 	off_t object_offset,
 	size_t length,
 	enum vm_prot prot,
 	virt_addr_t *out);
 
-/* returns true if the memory area defined by [base, base+len] contains:
- *  - no child regions
- *  - no vm_object mappings
- * if any child regions or mappings exist in the memory area, returns false.
- * if the memory area exceeds the bounds of the region, returns false.
- */
-extern bool vm_region_is_area_free(
-	const struct vm_region *region,
-	virt_addr_t base,
-	size_t len);
-
+/* find the mapping corresponding to the given virtual address, and page-in the
+ * necessary vm_page to allow the memory access to succeed. if the relevant
+ * vm-object page hasn't been allocated yet, it will be allocated here. */
 extern kern_status_t vm_region_demand_map(
 	struct vm_region *region,
 	virt_addr_t addr,
 	enum pmap_fault_flags flags);
 
+/* get the absolute base virtual address of a region within its
+ * parent/ancestors. */
+extern virt_addr_t vm_region_get_base_address(const struct vm_region *region);
+
 extern void vm_region_dump(struct vm_region *region, int depth);
 
 DEFINE_OBJECT_LOCK_FUNCTION(vm_region, vr_base)