ARM: function_graph: Simplify with function_graph_enter()

BugLink: https://bugs.launchpad.net/bugs/1836968
commit f1f5b14afd7cce39e6a9b25c685e1ea34c231096 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 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 5617932a83dfaab416a05e429642b2d19b0a4438..ee673c09aa6c0357efb4ad510a48d9eb419668a0 100644 (file)
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -227,9 +227,7 @@ 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;
@@ -237,21 +235,8 @@ 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