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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>
hifive-unleashed-5.1
Steven Rostedt (VMware) 2018-12-07 12:25:52 -05:00
parent e4c07bf986
commit 45fe439bc3
1 changed files with 11 additions and 0 deletions
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11
kernel/trace/fgraph.c
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@ -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)
{