1 files changed, 58 insertions, 0 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index f7212ec643e2..0cbe38a844fa 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -284,6 +284,64 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
         return ret;
 }
 
+/**
+ * ftrace_graph_ret_addr - convert a potentially modified stack return address
+ *                         to its original value
+ *
+ * This function can be called by stack unwinding code to convert a found stack
+ * return address ('ret') to its original value, in case the function graph
+ * tracer has modified it to be 'return_to_handler'.  If the address hasn't
+ * been modified, the unchanged value of 'ret' is returned.
+ *
+ * 'idx' is a state variable which should be initialized by the caller to zero
+ * before the first call.
+ *
+ * 'retp' is a pointer to the return address on the stack.  It's ignored if
+ * the arch doesn't have HAVE_FUNCTION_GRAPH_RET_ADDR_PTR defined.
+ */
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+                                    unsigned long ret, unsigned long *retp)
+{
+        int index = task->curr_ret_stack;
+        int i;
+
+        if (ret != (unsigned long)return_to_handler)
+                return ret;
+
+        if (index < -1)
+                index += FTRACE_NOTRACE_DEPTH;
+
+        if (index < 0)
+                return ret;
+
+        for (i = 0; i <= index; i++)
+                if (task->ret_stack[i].retp == retp)
+                        return task->ret_stack[i].ret;
+
+        return ret;
+}
+#else /* !HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+                                    unsigned long ret, unsigned long *retp)
+{
+        int task_idx;
+
+        if (ret != (unsigned long)return_to_handler)
+                return ret;
+
+        task_idx = task->curr_ret_stack;
+
+        if (!task->ret_stack || task_idx < *idx)
+                return ret;
+
+        task_idx -= *idx;
+        (*idx)++;
+
+        return task->ret_stack[task_idx].ret;
+}
+#endif /* HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
+
 int __trace_graph_entry(struct trace_array *tr,
                                 struct ftrace_graph_ent *trace,
                                 unsigned long flags,