vm: add vm-region to manage userspace virtual memory address spaces

vm-region supports creating nested regions of virtual memory, each with their
own memory protection restrictions.

vm-objects can be mapped into a vm-region, making the underlying memory
accessible. all mappings are lazy: page tables are not updated until the
mapped memory is accessed.

include/mango/vm-region.h

@@ -0,0 +1,126 @@
+#ifndef MANGO_VM_REGION_H_
+#define MANGO_VM_REGION_H_
+
+#include <mango/object.h>
+#include <mango/pmap.h>
+#include <mango/vm.h>
+
+#define VM_REGION_NAME_MAX        64
+
+#define VM_REGION_ANY_MAP_ADDRESS ((virt_addr_t) - 1)
+
+struct vm_region;
+struct vm_object;
+
+enum vm_region_entry_type {
+	VM_REGION_ENTRY_NONE = 0,
+	VM_REGION_ENTRY_REGION,
+	VM_REGION_ENTRY_MAPPING,
+};
+
+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;
+	/* size of the entry in bytes */
+	size_t e_size;
+};
+
+struct vm_region_mapping {
+	struct vm_region_entry m_entry;
+	struct vm_object *m_object;
+
+	/* used to link to  vm_object->vo_mappings */
+	struct queue_entry m_object_entry;
+
+	enum vm_prot m_prot;
+	/* offset in bytes to the start of the object data that was mapped */
+	off_t m_object_offset;
+};
+
+struct vm_region {
+	struct object vr_base;
+	struct vm_region_entry vr_entry;
+
+	char vr_name[VM_REGION_NAME_MAX];
+
+	/* btree of struct vm_region_entry.
+	 * sibling entries cannot overlap each other, and child entries must
+	 * be entirely contained within their immediate parent entry. */
+	struct btree vr_entries;
+
+	/* memory protection restriction mask.
+	 * any mapping in this region, or any of its children, cannot use
+	 * protection flags that are not set in this mask.
+	 * for example, if VM_PROT_EXEC is /not/ set here, no mapping
+	 * can be created in this region or any child region with VM_PROT_EXEC
+	 * set. */
+	enum vm_prot vr_prot;
+
+	/* the physical address space in which mappings in this region (and
+	 * its children) are created */
+	pmap_t vr_pmap;
+};
+
+extern kern_status_t vm_region_type_init(void);
+
+extern kern_status_t vm_region_create(
+	struct vm_region *parent,
+	const char *name,
+	virt_addr_t base,
+	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);
+
+extern kern_status_t vm_region_map_object(
+	struct vm_region *region,
+	virt_addr_t map_address,
+	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);
+
+extern kern_status_t vm_region_demand_map(
+	struct vm_region *region,
+	virt_addr_t addr,
+	enum pmap_fault_flags flags);
+
+extern void vm_region_dump(struct vm_region *region, int depth);
+
+DEFINE_OBJECT_LOCK_FUNCTION(vm_region, vr_base)
+
+#endif