From: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date: Fri, 7 Dec 2018 17:25:52 +0000 (-0500)
Subject: fgraph: Add comment to describe ftrace_graph_get_ret_stack
X-Git-Tag: v5.4-rc1~1850^2~25
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=45fe439bc3699851802062c05acf4cbac4d672bc;p=platform%2Fkernel%2Flinux-rpi.git

fgraph: Add comment to describe ftrace_graph_get_ret_stack

The ret_stack should not be accessed directly via the curr_ret_stack
variable on the task_struct. This is because the ret_stack is going to be
converted into a series of longs and not an array of ret_stack structures.
The way that a ret_stack should be retrieved is via the
ftrace_graph_get_ret_stack structure, but it needs to be documented on how
to use it.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index a3704ec..d4f04f0 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;
 }
 
+/**
+ * ftrace_graph_get_ret_stack - return the entry of the shadow stack
+ * @task: The task to read the shadow stack from
+ * @idx: Index down the shadow stack
+ *
+ * Return the ret_struct on the shadow stack of the @task at the
+ * call graph at @idx starting with zero. If @idx is zero, it
+ * will return the last saved ret_stack entry. If it is greater than
+ * zero, it will return the corresponding ret_stack for the depth
+ * of saved return addresses.
+ */
 struct ftrace_ret_stack *
 ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
 {