+#ifndef arch_has_block_step
+/**
+ * arch_has_block_step - does this CPU support user-mode block-step?
+ *
+ * If this is defined, then there must be a function declaration or inline
+ * for user_enable_block_step(), and arch_has_single_step() must be defined
+ * too. arch_has_block_step() should evaluate to nonzero iff the machine
+ * supports step-until-branch for user mode. It can be a constant or it
+ * can test a CPU feature bit.
+ */
+#define arch_has_single_step() (0)
+<snip>
+/**
+ * user_enable_block_step - step until branch in user-mode task
+ * @task: either current or a task stopped in %TASK_TRACED
+ *
+ * This can only be called when arch_has_block_step() has returned nonzero,
+ * and will never be called when single-instruction stepping is being used.
+ * Set @task so that when it returns to user mode, it will trap after the
+ * next branch or trap taken.
+ */
+static inline void user_enable_block_step(struct task_struct *task)
+{
+ BUG(); /* This can never be called. */
+}
+#endif /* arch_has_block_step */
+