+
+#endif
+
+#ifdef ALIEN_STACK_GROWS_DOWNWARD
+
+#define ALIEN_STACK_HARD_GUARD_PAGE(th) \
+ ((os_vm_address_t)(th->alien_stack_start))
+#define ALIEN_STACK_GUARD_PAGE(th) \
+ (ALIEN_STACK_HARD_GUARD_PAGE(th) + os_vm_page_size)
+#define ALIEN_STACK_RETURN_GUARD_PAGE(th) \
+ (ALIEN_STACK_GUARD_PAGE(th) + os_vm_page_size)
+
+#elif ALIEN_STACK_GROWS_UPWARD
+
+#define ALIEN_STACK_HARD_GUARD_PAGE(th) \