From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Tue, 23 Jan 2018 13:25:04 -0500
Subject: tracing: Update stack trace skipping for ORC unwinder
Git-commit: 2ee5b92a2598d9e403337185fdf88f661dee8616
Patch-mainline: v4.15
References: bnc#1058115

With the addition of ORC unwinder and FRAME POINTER unwinder, the stack
trace skipping requirements have changed.

I went through the tracing stack trace dumps with ORC and with frame
pointers and recalculated the proper values.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 kernel/trace/trace.c                |   34 ++++++++++++++----------
 kernel/trace/trace_events_trigger.c |   13 ++++++++-
 kernel/trace/trace_functions.c      |   49 ++++++++++++++++++++++++++----------
 3 files changed, 67 insertions(+), 29 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2276,6 +2276,15 @@ void trace_event_buffer_commit(struct tr
 }
 EXPORT_SYMBOL_GPL(trace_event_buffer_commit);
 
+/*
+ * Skip 3:
+ *
+ *   trace_buffer_unlock_commit_regs()
+ *   trace_event_buffer_commit()
+ *   trace_event_raw_event_xxx()
+*/
+# define STACK_SKIP 3
+
 void trace_buffer_unlock_commit_regs(struct trace_array *tr,
 				     struct ring_buffer *buffer,
 				     struct ring_buffer_event *event,
@@ -2285,16 +2294,12 @@ void trace_buffer_unlock_commit_regs(str
 	__buffer_unlock_commit(buffer, event);
 
 	/*
-	 * If regs is not set, then skip the following callers:
-	 *   trace_buffer_unlock_commit_regs
-	 *   event_trigger_unlock_commit
-	 *   trace_event_buffer_commit
-	 *   trace_event_raw_event_sched_switch
+	 * If regs is not set, then skip the necessary functions.
 	 * Note, we can still get here via blktrace, wakeup tracer
 	 * and mmiotrace, but that's ok if they lose a function or
-	 * two. They are that meaningful.
+	 * two. They are not that meaningful.
 	 */
-	ftrace_trace_stack(tr, buffer, flags, regs ? 0 : 4, pc, regs);
+	ftrace_trace_stack(tr, buffer, flags, regs ? 0 : STACK_SKIP, pc, regs);
 	ftrace_trace_userstack(buffer, flags, pc);
 }
 
@@ -2481,11 +2486,13 @@ static void __ftrace_trace_stack(struct
 	trace.skip		= skip;
 
 	/*
-	 * Add two, for this function and the call to save_stack_trace()
+	 * Add one, for this function and the call to save_stack_trace()
 	 * If regs is set, then these functions will not be in the way.
 	 */
+#ifndef CONFIG_UNWINDER_ORC
 	if (!regs)
-		trace.skip += 2;
+		trace.skip++;
+#endif
 
 	/*
 	 * Since events can happen in NMIs there's no safe way to
@@ -2613,11 +2620,10 @@ void trace_dump_stack(int skip)
 
 	local_save_flags(flags);
 
-	/*
-	 * Skip 3 more, seems to get us at the caller of
-	 * this function.
-	 */
-	skip += 3;
+#ifndef CONFIG_UNWINDER_ORC
+	/* Skip 1 to skip this function. */
+	skip++;
+#endif
 	__ftrace_trace_stack(global_trace.trace_buffer.buffer,
 			     flags, skip, preempt_count(), NULL);
 }
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1123,13 +1123,22 @@ static __init int register_trigger_snaps
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
 #ifdef CONFIG_STACKTRACE
+#ifdef CONFIG_UNWINDER_ORC
+/* Skip 2:
+ *   event_triggers_post_call()
+ *   trace_event_raw_event_xxx()
+ */
+# define STACK_SKIP 2
+#else
 /*
- * Skip 3:
+ * Skip 4:
  *   stacktrace_trigger()
  *   event_triggers_post_call()
+ *   trace_event_buffer_commit()
  *   trace_event_raw_event_xxx()
  */
-#define STACK_SKIP 3
+#define STACK_SKIP 4
+#endif
 
 static void
 stacktrace_trigger(struct event_trigger_data *data, void *rec)
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -153,6 +153,24 @@ function_trace_call(unsigned long ip, un
 	preempt_enable_notrace();
 }
 
+#ifdef CONFIG_UNWINDER_ORC
+/*
+ * Skip 2:
+ *
+ *   function_stack_trace_call()
+ *   ftrace_call()
+ */
+#define STACK_SKIP 2
+#else
+/*
+ * Skip 3:
+ *   __trace_stack()
+ *   function_stack_trace_call()
+ *   ftrace_call()
+ */
+#define STACK_SKIP 3
+#endif
+
 static void
 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
 			  struct ftrace_ops *op, struct pt_regs *pt_regs)
@@ -179,15 +197,7 @@ function_stack_trace_call(unsigned long
 	if (likely(disabled == 1)) {
 		pc = preempt_count();
 		trace_function(tr, ip, parent_ip, flags, pc);
-		/*
-		 * skip over 5 funcs:
-		 *    __ftrace_trace_stack,
-		 *    __trace_stack,
-		 *    function_stack_trace_call
-		 *    ftrace_list_func
-		 *    ftrace_call
-		 */
-		__trace_stack(tr, flags, 5, pc);
+		__trace_stack(tr, flags, STACK_SKIP, pc);
 	}
 
 	atomic_dec(&data->disabled);
@@ -366,14 +376,27 @@ ftrace_traceoff(unsigned long ip, unsign
 	tracer_tracing_off(tr);
 }
 
+#ifdef CONFIG_UNWINDER_ORC
+/*
+ * Skip 3:
+ *
+ *   function_trace_probe_call()
+ *   ftrace_ops_assist_func()
+ *   ftrace_call()
+ */
+#define FTRACE_STACK_SKIP 3
+#else
 /*
- * Skip 4:
+ * Skip 5:
+ *
+ *   __trace_stack()
  *   ftrace_stacktrace()
  *   function_trace_probe_call()
- *   ftrace_ops_list_func()
+ *   ftrace_ops_assist_func()
  *   ftrace_call()
  */
-#define STACK_SKIP 4
+#define FTRACE_STACK_SKIP 5
+#endif
 
 static __always_inline void trace_stack(struct trace_array *tr)
 {
@@ -383,7 +406,7 @@ static __always_inline void trace_stack(
 	local_save_flags(flags);
 	pc = preempt_count();
 
-	__trace_stack(tr, flags, STACK_SKIP, pc);
+	__trace_stack(tr, flags, FTRACE_STACK_SKIP, pc);
 }
 
 static void