ARM: function_graph: Simplify with function_graph_enter()

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 ARM 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: Russell King <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Cc: stable@kernel.org
Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 1 insertions, 16 deletions

diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 0142fcfcc3d3..bda949fd84e8 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -183,9 +183,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
                            unsigned long frame_pointer)
 {
         unsigned long return_hooker = (unsigned long) &return_to_handler;
-        struct ftrace_graph_ent trace;
         unsigned long old;
-        int err;
 
         if (unlikely(atomic_read(&current->tracing_graph_pause)))
                 return;
@@ -193,21 +191,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
         old = *parent;
         *parent = return_hooker;
 
-        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, NULL))
                 *parent = old;
-                return;
-        }
-
-        err = ftrace_push_return_trace(old, self_addr, &trace.depth,
-                                       frame_pointer, NULL);
-        if (err == -EBUSY) {
-                *parent = old;
-                return;
-        }
 }
 
 #ifdef CONFIG_DYNAMIC_FTRACE