[PATCH 4.19 103/139] powerpc/function_graph: Simplify with function_graph_enter()

[Greg Kroah-Hartman]

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

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

From: Steven Rostedt (VMware) <rostedt at goodmis.org>

commit fe60522ec60082a1dd735691b82c64f65d4ad15e 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 powerpc 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: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: linuxppc-dev at lists.ozlabs.org
Cc: stable at kernel.org
Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
Reviewed-by: Masami Hiramatsu <mhiramat at kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt at goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

---
 arch/powerpc/kernel/trace/ftrace.c |   15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -697,7 +697,6 @@ int ftrace_disable_ftrace_graph_caller(v
  */
 unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 {
-	struct ftrace_graph_ent trace;
 	unsigned long return_hooker;
 
 	if (unlikely(ftrace_graph_is_dead()))
@@ -708,18 +707,8 @@ unsigned long prepare_ftrace_return(unsi
 
 	return_hooker = ppc_function_entry(return_to_handler);
 
-	trace.func = ip;
-	trace.depth = current->curr_ret_stack + 1;
-
-	/* Only trace if the calling function expects to */
-	if (!ftrace_graph_entry(&trace))
-		goto out;
-
-	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
-				     NULL) == -EBUSY)
-		goto out;
-
-	parent = return_hooker;
+	if (!function_graph_enter(parent, ip, 0, NULL))
+		parent = return_hooker;
 out:
 	return parent;
 }