vm: add vm-object to represent non-contiguous physical memory allocations

vm-object can be used to demand-allocate non-contiguous physical memory, and
will provide an api for userspace programs to do the same. unless a vm-object
is created in-place (i.e. to represent a specific area of physical memory),
its memory pages are only allocated when the object is mapped AND someone
attempts to access the memory.

include/mango/vm-object.h

@@ -0,0 +1,68 @@
+#ifndef MANGO_VM_OBJECT_H_
+#define MANGO_VM_OBJECT_H_
+
+#include <mango/locks.h>
+#include <mango/object.h>
+
+#define VM_OBJECT_NAME_MAX 64
+
+enum vm_object_flags {
+	/* the memory behind this vm-object wasn't allocated by us, and
+	 * therefore shouldn't be freed by us */
+	VMO_IN_PLACE = 0x01u,
+};
+
+struct vm_object {
+	struct object vo_base;
+
+	char vo_name[VM_OBJECT_NAME_MAX];
+	enum vm_object_flags vo_flags;
+
+	/* queue of struct vm_region_mapping */
+	struct queue vo_mappings;
+
+	/* memory protection flags. mappings of this vm_object can only use
+	 * a subset of the flags set in this mask. */
+	enum vm_prot vo_prot;
+
+	/* btree of vm_pages that have been allocated to this vm_object.
+	 * vm_page->p_vmo_offset and the size of each page is the bst key. */
+	struct btree vo_pages;
+	/* total length of the vm_object in bytes. */
+	size_t vo_size;
+};
+
+extern kern_status_t vm_object_type_init(void);
+
+/* create a vm_object with the specified length in bytes and protection flags.
+ * the length will be automatically rounded up to the nearest vm_object page
+ * order size. the actual page frames themselves won't be allocated until
+ * they are mapped and accessed. */
+extern struct vm_object *vm_object_create(
+	const char *name,
+	size_t len,
+	enum vm_prot prot);
+
+/* create a vm_object that represents the specified range of physical memory.
+ * the length will be automatically rounded up to the nearest vm_object page
+ * order size.
+ * NOTE this function assumes that the physical memory has already been
+ * reserved, and is not in use by any other kernel component. */
+extern struct vm_object *vm_object_create_in_place(
+	const char *name,
+	phys_addr_t base,
+	size_t len,
+	enum vm_prot prot);
+
+extern struct vm_page *vm_object_get_page(
+	const struct vm_object *vo,
+	off_t offset);
+
+extern struct vm_page *vm_object_alloc_page(
+	struct vm_object *vo,
+	off_t offset,
+	enum vm_page_order size);
+
+DEFINE_OBJECT_LOCK_FUNCTION(vm_object, vo_base)
+
+#endif

vm/bootstrap.c

@@ -3,6 +3,7 @@
 #include <mango/memblock.h>
 #include <mango/printk.h>
 #include <mango/status.h>
+#include <mango/vm-object.h>
 #include <mango/vm.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -39,6 +40,7 @@ kern_status_t vm_bootstrap(
 	}
 
 	kmalloc_init();
+	vm_object_type_init();
 	return KERN_OK;
 }
 

vm/vm-object.c

@@ -0,0 +1,213 @@
+#include <mango/printk.h>
+#include <mango/vm-object.h>
+
+#define VM_OBJECT_CAST(p)                                                      \
+	OBJECT_C_CAST(struct vm_object, vo_base, &vm_object_type, p)
+
+static struct object_type vm_object_type = {
+	.ob_name = "vm-object",
+	.ob_size = sizeof(struct vm_object),
+	.ob_header_offset = offsetof(struct vm_object, vo_base),
+};
+
+static const enum vm_page_order GLOBAL_PAGE_ORDER = VM_PAGE_4K;
+
+static void put_page(
+	struct vm_object *vmo,
+	struct vm_page *new_page,
+	off_t offset)
+{
+	struct btree_node *cur = vmo->vo_pages.b_root;
+	new_page->p_vmo_offset = offset;
+
+	if (!cur) {
+		vmo->vo_pages.b_root = &new_page->p_bnode;
+		btree_insert_fixup(&vmo->vo_pages, &new_page->p_bnode);
+		return;
+	}
+
+	while (cur) {
+		struct vm_page *cur_page
+			= BTREE_CONTAINER(struct vm_page, p_bnode, cur);
+		struct btree_node *next = NULL;
+
+		off_t base = cur_page->p_vmo_offset;
+		off_t limit = base + vm_page_get_size_bytes(cur_page);
+		if (offset < base) {
+			next = btree_left(cur);
+		} else if (offset >= limit) {
+			next = btree_right(cur);
+		} else {
+			return;
+		}
+
+		if (next) {
+			cur = next;
+			continue;
+		}
+
+		if (offset < base) {
+			btree_put_left(cur, &new_page->p_bnode);
+		} else {
+			btree_put_right(cur, &new_page->p_bnode);
+		}
+
+		btree_insert_fixup(&vmo->vo_pages, &new_page->p_bnode);
+		return;
+	}
+}
+
+kern_status_t vm_object_type_init(void)
+{
+	return object_type_register(&vm_object_type);
+}
+
+enum vm_page_order vm_object_global_page_order(void)
+{
+	return GLOBAL_PAGE_ORDER;
+}
+
+struct vm_object *vm_object_create(
+	const char *name,
+	size_t len,
+	enum vm_prot prot)
+{
+	size_t page_bytes = VM_PAGE_SIZE;
+	uintptr_t page_mask = page_bytes - 1;
+
+	if (len & page_mask) {
+		len &= ~page_mask;
+		len += page_bytes;
+	}
+
+	struct object *obj = object_create(&vm_object_type);
+	if (!obj) {
+		return NULL;
+	}
+
+	struct vm_object *out = VM_OBJECT_CAST(obj);
+
+	out->vo_size = len;
+	out->vo_prot = prot;
+
+	if (name) {
+		strncpy(out->vo_name, name, sizeof out->vo_name);
+		out->vo_name[sizeof out->vo_name - 1] = '\0';
+	}
+
+	return out;
+}
+
+extern struct vm_object *vm_object_create_in_place(
+	const char *name,
+	phys_addr_t base,
+	size_t len,
+	enum vm_prot prot)
+{
+	struct vm_object *vmo = vm_object_create(name, len, prot);
+	if (!vmo) {
+		return NULL;
+	}
+
+	for (phys_addr_t i = base, offset = 0; i < base + vmo->vo_size;
+	     i += VM_PAGE_SIZE, offset += VM_PAGE_SIZE) {
+		struct vm_page *pg = vm_page_get(i);
+		if (!pg) {
+			printk("vm-object: invalid physical address %08llx", i);
+			object_unref(&vmo->vo_base);
+			return NULL;
+		}
+
+		put_page(vmo, pg, offset);
+	}
+
+	vmo->vo_flags |= VMO_IN_PLACE;
+
+	return vmo;
+}
+
+extern struct vm_page *vm_object_get_page(
+	const struct vm_object *vo,
+	off_t offset)
+{
+	struct btree_node *cur = vo->vo_pages.b_root;
+	while (cur) {
+		struct vm_page *page
+			= BTREE_CONTAINER(struct vm_page, p_bnode, cur);
+		struct btree_node *next = NULL;
+
+		off_t base = page->p_vmo_offset;
+		off_t limit = base + vm_page_get_size_bytes(page);
+		if (offset < base) {
+			next = btree_left(cur);
+		} else if (offset >= limit) {
+			next = btree_right(cur);
+		} else {
+			return page;
+		}
+
+		cur = next;
+	}
+
+	return NULL;
+}
+
+extern struct vm_page *vm_object_alloc_page(
+	struct vm_object *vo,
+	off_t offset,
+	enum vm_page_order size)
+{
+	struct vm_page *page = NULL;
+	struct btree_node *cur = vo->vo_pages.b_root;
+	if (!cur) {
+		page = vm_page_alloc(VM_PAGE_4K, VM_NORMAL);
+		if (!page) {
+			return NULL;
+		}
+
+		page->p_vmo_offset = offset;
+		vo->vo_pages.b_root = &page->p_bnode;
+		btree_insert_fixup(&vo->vo_pages, &page->p_bnode);
+		return page;
+	}
+
+	while (cur) {
+		struct vm_page *page
+			= BTREE_CONTAINER(struct vm_page, p_bnode, cur);
+		struct btree_node *next = NULL;
+
+		off_t base = page->p_vmo_offset;
+		off_t limit = base + vm_page_get_size_bytes(page);
+		if (offset < base) {
+			next = btree_left(cur);
+		} else if (offset >= limit) {
+			next = btree_right(cur);
+		} else {
+			return page;
+		}
+
+		if (next) {
+			cur = next;
+			continue;
+		}
+
+		page = vm_page_alloc(VM_PAGE_4K, VM_NORMAL);
+		if (!page) {
+			return NULL;
+		}
+
+		page->p_vmo_offset = offset;
+
+		if (offset < base) {
+			btree_put_left(cur, &page->p_bnode);
+		} else {
+			btree_put_right(cur, &page->p_bnode);
+		}
+
+		btree_insert_fixup(&vo->vo_pages, &page->p_bnode);
+
+		return page;
+	}
+
+	return NULL;
+}