linux-kernel - [for-next][PATCH 04/18] arm64: function_graph: Simplify with function_graph

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Date:   Wed, 21 Nov 2018 19:28:05 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-arch@...r.kernel.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org, stable@...nel.org
Subject: [for-next][PATCH 04/18] arm64: function_graph: Simplify with function_graph_entry()

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

The function_graph_entry() 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 arm64 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: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: stable@...nel.org
Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 arch/arm64/kernel/ftrace.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 50986e388d2b..57e962290df3 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -216,8 +216,6 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 {
 	unsigned long return_hooker = (unsigned long)&return_to_handler;
 	unsigned long old;
-	struct ftrace_graph_ent trace;
-	int err;
 
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
@@ -229,18 +227,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 	 */
 	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;
-
-	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
-				       frame_pointer, NULL);
-	if (err == -EBUSY)
-		return;
-	else
+	if (!function_graph_enter(old, self_addr, frame_pointer, NULL))
 		*parent = return_hooker;
 }
 
-- 
2.19.1