-#define KCODE_MAX_SIZE MEM_4MB
-#define KHEAP_START (KERNEL_MM_BASE + KCODE_MAX_SIZE)
-#define KHEAP_SIZE_MB 256
+#define USER_START 0x400000
+
+#define KSTACK_SIZE MEM_1MB
+#define KSTACK_START (USER_START - KSTACK_SIZE)
+#define KSTACK_TOP ((USER_START - 1) & ~0xf)