[PATCH 4.19 099/139] ARM: function_graph: Simplify with function_graph_enter()

From: Greg Kroah-Hartman
Date: Tue Dec 04 2018 - 06:27:46 EST


4.19-stable review patch. If anyone has any objections, please let me know.

------------------

From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

commit f1f5b14afd7cce39e6a9b25c685e1ea34c231096 upstream.

The function_graph_enter() function does the work of calling the function
graph hook function and the management of the shadow stack, simplifying the
work done in the architecture dependent prepare_ftrace_return().

Have ARM use the new code, and remove the shadow stack management as well as
having to set up the trace structure.

This is needed to prepare for a fix of a design bug on how the curr_ret_stack
is used.

Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxx
Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/arm/kernel/ftrace.c | 17 +----------------
1 file changed, 1 insertion(+), 16 deletions(-)

--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -227,9 +227,7 @@ void prepare_ftrace_return(unsigned long
unsigned long frame_pointer)
{
unsigned long return_hooker = (unsigned long) &return_to_handler;
- struct ftrace_graph_ent trace;
unsigned long old;
- int err;

if (unlikely(atomic_read(&current->tracing_graph_pause)))
return;
@@ -237,21 +235,8 @@ void prepare_ftrace_return(unsigned long
old = *parent;
*parent = return_hooker;

- trace.func = self_addr;
- trace.depth = current->curr_ret_stack + 1;
-
- /* Only trace if the calling function expects to */
- if (!ftrace_graph_entry(&trace)) {
+ if (function_graph_enter(old, self_addr, frame_pointer, NULL))
*parent = old;
- return;
- }
-
- err = ftrace_push_return_trace(old, self_addr, &trace.depth,
- frame_pointer, NULL);
- if (err == -EBUSY) {
- *parent = old;
- return;
- }
}

#ifdef CONFIG_DYNAMIC_FTRACE