From d3d532d798c5720055ab02a10bf7829a33c3645a Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Tue, 4 Apr 2017 16:44:43 -0400
Subject: [PATCH] ftrace: Have unregister_ftrace_function_probe_func() return a
 value

Currently unregister_ftrace_function_probe_func() is a void function. It
does not give any feedback if an error occurred or no item was found to
remove and nothing was done.

Change it to return status and success if it removed something. Also update
the callers to return that feedback to the user.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c          | 14 +++++++++++---
 kernel/trace/trace.c           |  6 ++----
 kernel/trace/trace.h           |  2 +-
 kernel/trace/trace_events.c    |  3 +--
 kernel/trace/trace_functions.c |  6 ++----
 5 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5c8d8eea9e7c..cbae7fb1be15 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4102,7 +4102,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 	return count;
 }
 
-void
+int
 unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 {
 	struct ftrace_ops_hash old_hash_ops;
@@ -4131,7 +4131,7 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 
 		/* we do not support '!' for function probes */
 		if (WARN_ON(not))
-			return;
+			return -EINVAL;
 	}
 
 	mutex_lock(&trace_probe_ops.func_hash->regex_lock);
@@ -4140,9 +4140,9 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 	/* Probes only have filters */
 	old_hash_ops.notrace_hash = NULL;
 
+	ret = -ENOMEM;
 	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
 	if (!hash)
-		/* Hmm, should report this somehow */
 		goto out_unlock;
 
 	INIT_LIST_HEAD(&free_list);
@@ -4173,6 +4173,13 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 			list_add(&entry->free_list, &free_list);
 		}
 	}
+
+	/* Nothing found? */
+	if (list_empty(&free_list)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
 	mutex_lock(&ftrace_lock);
 	disabled = __disable_ftrace_function_probe();
 	/*
@@ -4198,6 +4205,7 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
  out_unlock:
 	mutex_unlock(&trace_probe_ops.func_hash->regex_lock);
 	free_ftrace_hash(hash);
+	return ret;
 }
 
 static LIST_HEAD(ftrace_commands);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7a4d578d8887..64a4418a5106 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6829,10 +6829,8 @@ ftrace_trace_snapshot_callback(struct ftrace_hash *hash,
 
 	ops = param ? &snapshot_count_probe_ops :  &snapshot_probe_ops;
 
-	if (glob[0] == '!') {
-		unregister_ftrace_function_probe_func(glob+1, ops);
-		return 0;
-	}
+	if (glob[0] == '!')
+		return unregister_ftrace_function_probe_func(glob+1, ops);
 
 	if (!param)
 		goto out_reg;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 86aa5a2222ba..31d80bff9ee6 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -963,7 +963,7 @@ void free_ftrace_func_mapper(struct ftrace_func_mapper *mapper,
 extern int
 register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 			      void *data);
-extern void
+extern int
 unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops);
 
 int register_ftrace_command(struct ftrace_func_command *cmd);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 37902107c44f..9e07a5b3869b 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2652,8 +2652,7 @@ event_enable_func(struct ftrace_hash *hash,
 		ops = param ? &event_disable_count_probe_ops : &event_disable_probe_ops;
 
 	if (glob[0] == '!') {
-		unregister_ftrace_function_probe_func(glob+1, ops);
-		ret = 0;
+		ret = unregister_ftrace_function_probe_func(glob+1, ops);
 		goto out;
 	}
 
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 56d0fe1e4ea1..dcb4d37ed4bd 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -586,10 +586,8 @@ ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
 	if (!enable)
 		return -EINVAL;
 
-	if (glob[0] == '!') {
-		unregister_ftrace_function_probe_func(glob+1, ops);
-		return 0;
-	}
+	if (glob[0] == '!')
+		return unregister_ftrace_function_probe_func(glob+1, ops);
 
 	if (!param)
 		goto out_reg;