vm: refactor page_array and functions into a separate source file

vm/flat.c

@@ -0,0 +1,58 @@
+#include <socks/vm.h>
+#include <socks/memblock.h>
+#include <socks/printk.h>
+
+/* array of pages, one for each physical page frame present in RAM */
+static vm_page_t *page_array = NULL;
+
+/* number of pages stored in page_array */
+static size_t page_array_count = 0;
+
+void vm_flat_init()
+{
+	printk("vm: using flat memory model");
+	size_t pmem_size = 0;
+
+	memblock_iter_t it;
+	for_each_free_mem_range (&it, 0x0, UINTPTR_MAX) {
+		if (pmem_size < it.it_limit + 1) {
+			pmem_size = it.it_limit + 1;
+		}
+	}
+
+	size_t nr_pages = pmem_size / VM_PAGE_SIZE;
+	if (pmem_size % VM_PAGE_SIZE) {
+		nr_pages++;
+	}
+
+	page_array = memblock_alloc(sizeof(vm_page_t) * nr_pages, 8);
+	page_array_count = nr_pages;
+
+	size_t nr_reserved = nr_pages;
+
+	for (size_t i = 0; i < nr_pages; i++) {
+		page_array[i].p_flags = VM_PAGE_RESERVED;
+	}
+
+	for_each_free_mem_range(&it, 0x0, UINTPTR_MAX) {
+		for (uintptr_t i = it.it_base; i < it.it_limit; i += VM_PAGE_SIZE) {
+			size_t pfn = i / VM_PAGE_SIZE;
+
+			page_array[pfn].p_flags = 0;
+			nr_reserved--;
+		}
+	}
+
+	printk("vm: page array has %zu pages, %zu reserved", nr_pages, nr_reserved);
+}
+
+vm_page_t *vm_page_get_flat(phys_addr_t addr)
+{
+	size_t pfn = addr / VM_PAGE_SIZE;
+	return pfn < page_array_count ? &page_array[pfn] : NULL;
+}
+
+size_t vm_page_get_pfn_flat(vm_page_t *pg)
+{
+	return ((uintptr_t)pg - (uintptr_t)page_array) / sizeof *pg;
+}