linux-kernel - [PATCH 4.19 106/139] parisc: function_graph: Simplify with function_graph

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Date:   Tue,  4 Dec 2018 11:49:47 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
        stable@...nel.org, Masami Hiramatsu <mhiramat@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.19 106/139] parisc: function_graph: Simplify with function_graph_enter()

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

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

From: Steven Rostedt (VMware) <rostedt@...dmis.org>

commit a87532c78d291265efadc4b20a8c7a70cd59ea29 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 parisc 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: "James E.J. Bottomley" <jejb@...isc-linux.org>
Cc: Helge Deller <deller@....de>
Cc: linux-parisc@...r.kernel.org
Cc: stable@...nel.org
Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/parisc/kernel/ftrace.c |   17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

--- a/arch/parisc/kernel/ftrace.c
+++ b/arch/parisc/kernel/ftrace.c
@@ -30,7 +30,6 @@ static void __hot prepare_ftrace_return(
 					unsigned long self_addr)
 {
 	unsigned long old;
-	struct ftrace_graph_ent trace;
 	extern int parisc_return_to_handler;

 	if (unlikely(ftrace_graph_is_dead()))
@@ -41,19 +40,9 @@ static void __hot prepare_ftrace_return(

 	old = *parent;

-	trace.func = self_addr;
-	trace.depth = current->curr_ret_stack + 1;
-
-	/* Only trace if the calling function expects to */
-	if (!ftrace_graph_entry(&trace))
-		return;
-
-        if (ftrace_push_return_trace(old, self_addr, &trace.depth,
-				     0, NULL) == -EBUSY)
-                return;
-
-	/* activate parisc_return_to_handler() as return point */
-	*parent = (unsigned long) &parisc_return_to_handler;
+	if (!function_graph_enter(old, self_addr, 0, NULL))
+		/* activate parisc_return_to_handler() as return point */
+		*parent = (unsigned long) &parisc_return_to_handler;
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */