[PATCH 4.19 101/139] x86/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@xxxxxxxxxxx>

commit 07f7175b43827640d1e69c9eded89aa089a234b4 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 x86 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: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
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/x86/kernel/ftrace.c |   15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -994,7 +994,6 @@ void prepare_ftrace_return(unsigned long
 {
 	unsigned long old;
 	int faulted;
-	struct ftrace_graph_ent trace;
 	unsigned long return_hooker = (unsigned long)
 				&return_to_handler;
 
@@ -1046,19 +1045,7 @@ void prepare_ftrace_return(unsigned long
 		return;
 	}
 
-	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, parent))
 		*parent = old;
-		return;
-	}
-
-	if (ftrace_push_return_trace(old, self_addr, &trace.depth,
-				     frame_pointer, parent) == -EBUSY) {
-		*parent = old;
-		return;
-	}
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */