GDT finally works

kernel/hal/util.c

@@ -0,0 +1,9 @@
+#include <stdint.h>
+#include "hal.h"
+
+void hal_memset(void *mem, uint8_t v, uint32_t size) {
+  uint8_t *mem1 = mem;
+  for (uint32_t i = 0; i < size; i++) {
+    mem1[i] = v;
+  }
+}