sandbox: vm: add page splitting, merging, and allocation

sandbox/vm/page.c

@@ -145,3 +145,118 @@ vm_zone_t *vm_page_get_zone(vm_page_t *pg)
 	
 	return &node->pg_zones[pg->p_zone];
 }
+
+
+vm_page_t *vm_page_alloc(vm_page_order_t order, vm_flags_t flags)
+{
+	/* TODO prefer nodes closer to us */
+	vm_pg_data_t *node = vm_pg_data_get(0);
+	vm_zone_id_t zone_id = VM_ZONE_HIGHMEM;
+	if (flags & VM_GET_DMA) {
+		zone_id = VM_ZONE_DMA;
+	}
+
+	while (1) {
+		vm_zone_t *z = &node->pg_zones[zone_id];
+
+		vm_page_t *pg = vm_zone_alloc_page(z, order, flags);
+		if (pg) {
+			return pg;
+		}
+
+		if (zone_id == VM_ZONE_MIN) {
+			break;
+		}
+
+		zone_id--;
+	}
+	
+	return NULL;
+}
+
+void vm_page_free(vm_page_t *pg)
+{
+	vm_zone_t *z = vm_page_get_zone(pg);
+	if (!z) {
+		return;
+	}
+
+	vm_zone_free_page(z, pg);
+}
+
+int vm_page_split(vm_page_t *pg, vm_page_t **a, vm_page_t **b)
+{
+	if (pg->p_order == VM_PAGE_MIN_ORDER) {
+		return -1;
+	}
+
+	size_t nr_frames = vm_page_order_to_pages(pg->p_order);
+	for (size_t i = 0; i < nr_frames; i++) {
+		pg[i].p_order = pg->p_order - 1;
+	}
+
+	vm_page_t *buddy = vm_page_get_buddy(pg);
+
+	if (pg->p_order == VM_PAGE_MIN_ORDER) {
+		pg->p_flags &= ~(VM_PAGE_HUGE | VM_PAGE_HEAD);
+		buddy->p_flags &= ~(VM_PAGE_HUGE | VM_PAGE_HEAD);
+	} else {
+		pg->p_flags |= VM_PAGE_HEAD | VM_PAGE_HUGE;
+		buddy->p_flags |= VM_PAGE_HEAD | VM_PAGE_HUGE;
+	}
+
+	*a = pg;
+	*b = buddy;
+	
+	return 0;
+}
+
+vm_page_t *vm_page_merge(vm_page_t *a, vm_page_t *b)
+{
+	if (a->p_order != b->p_order) {
+		return NULL;
+	}
+
+	if (a->p_order == VM_PAGE_MAX_ORDER) {
+		return NULL;
+	}
+
+	if (vm_page_get_buddy(a) != b) {
+		return NULL;
+	}
+	
+	if (VM_PAGE_IS_RESERVED(a) && !VM_PAGE_IS_RESERVED(b)) {
+		return NULL;
+	}
+
+	if (!VM_PAGE_IS_RESERVED(a) && VM_PAGE_IS_RESERVED(b)) {
+		return NULL;
+	}
+
+	/* make sure that a comes before b */
+	if (a > b) {
+		vm_page_t *tmp = a;
+		a = b;
+		b = tmp;
+	}
+
+	a->p_order++;
+
+	size_t nr_frames = vm_page_order_to_pages(a->p_order);
+	for (size_t i = 0; i < nr_frames; i++) {
+		a[i].p_flags &= ~VM_PAGE_HEAD;
+		a[i].p_flags |= VM_PAGE_HUGE;
+		a[i].p_order = a->p_order;
+	}
+
+	a->p_flags |= VM_PAGE_HEAD;
+	
+	return 0;
+}
+
+vm_page_t *vm_page_get_buddy(vm_page_t *pg)
+{
+	phys_addr_t paddr = vm_page_get_paddr(pg);
+	paddr = paddr ^ vm_page_order_to_bytes(pg->p_order);
+	return vm_page_get(paddr);
+}