linux-kernel - [PATCH 4.19 104/139] sh/function_graph: Simplify with function_graph

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Date:   Tue,  4 Dec 2018 11:49:45 +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,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
        stable@...nel.org, Masami Hiramatsu <mhiramat@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.19 104/139] sh/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 bc715ee4dbc5db462c59b9cfba92d31b3274fe3a 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 superh 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: Yoshinori Sato <ysato@...rs.sourceforge.jp>
Cc: Rich Felker <dalias@...c.org>
Cc: linux-sh@...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/sh/kernel/ftrace.c |   16 ++--------------
 1 file changed, 2 insertions(+), 14 deletions(-)

--- a/arch/sh/kernel/ftrace.c
+++ b/arch/sh/kernel/ftrace.c
@@ -321,8 +321,7 @@ int ftrace_disable_ftrace_graph_caller(v
 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 {
 	unsigned long old;
-	int faulted, err;
-	struct ftrace_graph_ent trace;
+	int faulted;
 	unsigned long return_hooker = (unsigned long)&return_to_handler;
 
 	if (unlikely(ftrace_graph_is_dead()))
@@ -365,18 +364,7 @@ void prepare_ftrace_return(unsigned long
 		return;
 	}
 
-	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0, NULL);
-	if (err == -EBUSY) {
+	if (function_graph_enter(old, self_addr, 0, NULL))
 		__raw_writel(old, parent);
-		return;
-	}
-
-	trace.func = self_addr;
-
-	/* Only trace if the calling function expects to */
-	if (!ftrace_graph_entry(&trace)) {
-		current->curr_ret_stack--;
-		__raw_writel(old, parent);
-	}
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */