function_graph: Have profiler use new helper ftrace_graph_get_ret_stack()

The ret_stack processing is going to change, and that is going
to break anything that is accessing the ret_stack directly. One user is the
function graph profiler. By using the ftrace_graph_get_ret_stack() helper
function, the profiler can access the ret_stack entry without relying on the
implementation details of the stack itself.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 90fcefcaff2a..a3704ec8b599 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -232,6 +232,17 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 	return ret;
 }
 
+struct ftrace_ret_stack *
+ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
+{
+	idx = current->curr_ret_stack - idx;
+
+	if (idx >= 0 && idx <= task->curr_ret_stack)
+		return &current->ret_stack[idx];
+
+	return NULL;
+}
+
 /**
  * ftrace_graph_ret_addr - convert a potentially modified stack return address
  *			   to its original value