powerpc/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 powerpc 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: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.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>

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 4bf051d..b65c8a3 100644 (file)
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -950,7 +950,6 @@ int ftrace_disable_ftrace_graph_caller(void)
  */
 unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 {
-       struct ftrace_graph_ent trace;
        unsigned long return_hooker;
 
        if (unlikely(ftrace_graph_is_dead()))
@@ -961,18 +960,8 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 
        return_hooker = ppc_function_entry(return_to_handler);
 
-       trace.func = ip;
-       trace.depth = current->curr_ret_stack + 1;
-
-       /* Only trace if the calling function expects to */
-       if (!ftrace_graph_entry(&trace))
-               goto out;
-
-       if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
-                                    NULL) == -EBUSY)
-               goto out;
-
-       parent = return_hooker;
+       if (!function_graph_enter(parent, ip, 0, NULL))
+               parent = return_hooker;
 out:
        return parent;
 }