add System::free_pages()

src/core/System.cc

@@ -54,3 +54,8 @@ void * System::alloc_pages(int num)
             -1,
             0);
 }
+
+void System::free_pages(void * addr, int num)
+{
+    (void)munmap(addr, num << System::page_size_log);
+}

src/core/System.h

@@ -6,6 +6,7 @@ class System
 public:
     static bool init();
     static void * alloc_pages(int num);
+    static void free_pages(void * addr, int num);
 
     static unsigned long page_size;
     static unsigned int page_size_log;