Merge tag 'trace-v4.15-rc9' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "With the new ORC unwinder, ftrace stack tracing became disfunctional.

  One was that ORC didn't know how to handle the ftrace callbacks in
  general (which Josh fixed).

  The other was that ORC would just bail if it hit a dynamically
  allocated trampoline. Which means all ftrace stack tracing that
  happens from the function tracer would produce no results (that
  includes killing the max stack size tracer). I added a check to the
  ORC unwinder to see if the trampoline belonged to ftrace, and if it
  did, use the orc entry of the static trampoline that was used to
  create the dynamic one (it would be identical).

  Finally, I noticed that the skip values of the stack tracing were out
  of whack. I went through and fixed them up"

* tag 'trace-v4.15-rc9' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Update stack trace skipping for ORC unwinder
  ftrace, orc, x86: Handle ftrace dynamically allocated trampolines
  x86/ftrace: Fix ORC unwinding from ftrace handlers

4 files changed, 84 insertions, 41 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ccdf3664e4a9..554b517c61a0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1119,15 +1119,11 @@ static struct ftrace_ops global_ops = {
 };
 
 /*
- * This is used by __kernel_text_address() to return true if the
- * address is on a dynamically allocated trampoline that would
- * not return true for either core_kernel_text() or
- * is_module_text_address().
+ * Used by the stack undwinder to know about dynamic ftrace trampolines.
  */
-bool is_ftrace_trampoline(unsigned long addr)
+struct ftrace_ops *ftrace_ops_trampoline(unsigned long addr)
 {
-	struct ftrace_ops *op;
-	bool ret = false;
+	struct ftrace_ops *op = NULL;
 
 	/*
 	 * Some of the ops may be dynamically allocated,
@@ -1144,15 +1140,24 @@ bool is_ftrace_trampoline(unsigned long addr)
 		if (op->trampoline && op->trampoline_size)
 			if (addr >= op->trampoline &&
 			    addr < op->trampoline + op->trampoline_size) {
-				ret = true;
-				goto out;
+				preempt_enable_notrace();
+				return op;
 			}
 	} while_for_each_ftrace_op(op);
-
- out:
 	preempt_enable_notrace();
 
-	return ret;
+	return NULL;
+}
+
+/*
+ * This is used by __kernel_text_address() to return true if the
+ * address is on a dynamically allocated trampoline that would
+ * not return true for either core_kernel_text() or
+ * is_module_text_address().
+ */
+bool is_ftrace_trampoline(unsigned long addr)
+{
+	return ftrace_ops_trampoline(addr) != NULL;
 }
 
 struct ftrace_page {
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2a8d8a294345..8e3f20a18a06 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2374,6 +2374,15 @@ void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
 }
 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,
@@ -2383,16 +2392,12 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr,
 	__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);
 }
 
@@ -2579,11 +2584,13 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
 	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
@@ -2711,11 +2718,10 @@ 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);
 }
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index f2ac9d44f6c4..87411482a46f 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1123,13 +1123,22 @@ static __init int register_trigger_snapshot_cmd(void) { return 0; }
 #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)
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 27f7ad12c4b1..b611cd36e22d 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -154,6 +154,24 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
 	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)
@@ -180,15 +198,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
 	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);
@@ -367,14 +377,27 @@ ftrace_traceoff(unsigned long ip, unsigned long parent_ip,
 	tracer_tracing_off(tr);
 }
 
+#ifdef CONFIG_UNWINDER_ORC
 /*
- * Skip 4:
+ * Skip 3:
+ *
+ *   function_trace_probe_call()
+ *   ftrace_ops_assist_func()
+ *   ftrace_call()
+ */
+#define FTRACE_STACK_SKIP 3
+#else
+/*
+ * 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)
 {
@@ -384,7 +407,7 @@ static __always_inline void trace_stack(struct trace_array *tr)
 	local_save_flags(flags);
 	pc = preempt_count();
 
-	__trace_stack(tr, flags, STACK_SKIP, pc);
+	__trace_stack(tr, flags, FTRACE_STACK_SKIP, pc);
 }
 
 static void