1 files changed, 44 insertions, 0 deletions
diff --git a/boot/page.inc b/boot/page.inc
new file mode 100644
index 0000000..ec2a8ad
--- /dev/null
+++ b/boot/page.inc
@@ -0,0 +1,44 @@
+PAGE_SIZE = 0x1000
+
+PAGE_PRESENT = (1 shl 0)
+PAGE_WRITE   = (1 shl 1)
+
+macro page_table_init_real pml4_table* {
+	local page_table
+
+	; zero out page table
+	mov edi, pml4_table
+	push di
+	mov ecx, (PAGE_SIZE*4)/4
+	xor eax, eax
+	cld
+	rep stosd
+	pop di
+
+	virtual at di
+		label page_table
+		.PML4T rb PAGE_SIZE
+		.PDPT  rb PAGE_SIZE
+		.PDT   rb PAGE_SIZE
+		.PT    rb PAGE_SIZE
+		.sizeof = $ - page_table
+	end virtual
+
+	; create first entry
+	mov word [.PML4T], (pml4_table + .PDPT - page_table) or PAGE_PRESENT or PAGE_WRITE
+	mov word [.PDPT],  (pml4_table + .PDT  - page_table) or PAGE_PRESENT or PAGE_WRITE
+	mov word [.PDT],   (pml4_table + .PT   - page_table) or PAGE_PRESENT or PAGE_WRITE
+
+	; identity map pages
+	push di
+	mov di, (pml4_table + .PT - page_table)
+	mov ax, (PAGE_PRESENT or PAGE_WRITE)
+@@:
+	mov [di], eax
+	add eax, PAGE_SIZE
+	add di, 8
+	cmp di, pml4_table + .sizeof
+	jb @b
+
+	pop di
+}