Added basic paging.h & paging.c

kernel/src/paging.c

@@ -0,0 +1,27 @@
+#include <kernel.h>
+#include <string.h>
+#include <paging.h>
+
+// Invalidates the pagedir entry in the CPUs TLB cache
+static inline void invalidate(uint32_t vaddr) {
+	__asm__ volatile ("invlpg %0" : : "m"(vaddr));
+}
+
+int pag_init(void) {
+	// Unmap first MB
+	init_pagedir[0] = 0;
+	invalidate(0);
+
+	/*
+	 * Recursive table mapping
+	 * We map the last pagetab to the pagedir itself, so it acts
+	 * as a pagetab even though it's a pagedir. This maps it to
+	 * the virtual address 0xFFFFF000.
+	 */
+	init_pagedir[1023] = ((uint32_t)init_pagedir - 0xC0000000) |
+		PAGE_FLAG_PRESENT | PAGE_FLAG_WRITE;
+	invalidate(0xFFFFF000);
+
+	return 0;
+}
+