--- mmap-orig.c	2020-08-06 10:27:00.844340199 -0700
+++ mmap-mod.c	2020-08-06 10:33:36.733107851 -0700
@@ -11,7 +11,12 @@
 
 static const char *filename = "lkmc_mmap";
 
-enum { BUFFER_SIZE = 4 };
+#ifndef PAGE_SIZE       //should be defined in kernel
+#define PAGE_SIZE       4096
+#endif
+#define BUFFER_PAGES    64
+#define PAGES_ORDER     6   //2^6 = 64 pages
+#define BUFFER_SIZE     (PAGE_SIZE * BUFFER_PAGES)
 
 struct mmap_info {
 	char *data;
@@ -32,7 +37,7 @@
 	pr_info("vm_fault\n");
 	info = (struct mmap_info *)vmf->vma->vm_private_data;
 	if (info->data) {
-		page = virt_to_page(info->data);
+		page = virt_to_page(info->data + (PAGE_SIZE * vmf->pgoff));
 		get_page(page);
 		vmf->page = page;
 	}
@@ -69,8 +74,14 @@
 	pr_info("open\n");
 	info = kmalloc(sizeof(struct mmap_info), GFP_KERNEL);
 	pr_info("virt_to_phys = 0x%llx\n", (unsigned long long)virt_to_phys((void *)info));
-	info->data = (char *)get_zeroed_page(GFP_KERNEL);
-	memcpy(info->data, "asdf", BUFFER_SIZE);
+	info->data = (char *)__get_free_pages(GFP_KERNEL, PAGES_ORDER);
+    if(info->data == NULL)
+    {
+        pr_err("Unable to allocate framebuffer!\n");
+        return -ENOMEM;
+    }
+    memset(info->data, 0, PAGE_SIZE << PAGES_ORDER);    //zero the buffer
+	memcpy(info->data, "asdf", 4);
 	filp->private_data = info;
 	return 0;
 }
@@ -105,10 +116,13 @@
 static int release(struct inode *inode, struct file *filp)
 {
 	struct mmap_info *info;
+    struct page *page;
 
 	pr_info("release\n");
 	info = filp->private_data;
-	free_page((unsigned long)info->data);
+    page = virt_to_page(info->data);
+    put_page(page);
+	free_pages((unsigned long)info->data, PAGES_ORDER);
 	kfree(info);
 	filp->private_data = NULL;
 	return 0;