-#define USER_START 0x400000
-#define USTACK_SIZE 0x100000
-#define USTACK_TOP 0x9fffffff
-#define USTACK_END (USTACK_TOP - USTACK_SIZE + 1)
-#define UMMAP_AREA 0x4D000000
-
-#define SYS_TIMER_FREQUENCY_HZ 2048
+#define USTACK_SIZE MEM_4MB
+#define USTACK_TOP 0x9ffffff0
+#define USTACK_END (0x9fffffff - USTACK_SIZE + 1)
+#define UMMAP_START 0x4D000000
+#define UMMAP_END (USTACK_END - MEM_4MB)