pmm changes

src/include/kernel/pmm.h

@@ -10,5 +10,6 @@ void pmm_free(void*, size_t);
 void pmm_setused(void*, size_t);
 
 extern void* limine_hhdm_offset;
+extern void* pmm_usabletop;
 
 #endif

src/sys/mm/pmm.c

@@ -28,6 +28,7 @@ size_t* bitmap = 0;
 size_t usablememsize = 0;
 size_t totalmemsize  = 0;
 void* lastfree = PAGE_SIZE;
+void* pmm_usabletop;
 int lock = 0;
 
 static int getstate(void* addr){
@@ -236,4 +237,6 @@ void pmm_init(){
 
 	pmm_setused(bitmap, bitmappages);
 
+	pmm_usabletop = bitmaptop;
+
 }