GDT finally works

kernel/pmm/pmm.h

@@ -0,0 +1,20 @@
+#ifndef PMM_PMM_H_
+#define PMM_PMM_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include "spinlock.h"
+#include "bitmap/bitmap.h"
+
+typedef struct {
+  SpinLock spinlock;
+  BitMap self;
+} PhysMem;
+
+extern PhysMem PHYS_MEM;
+
+void pmm_init(void);
+void *pmm_alloc(size_t pages);
+void pmm_free(uintptr_t ptr, size_t pages);
+
+#endif // PMM_PMM_H_