tracing: Do not enable function event with enable

With the adding of function tracing event to perf, it caused a
side effect that produces the following warning when enabling all
events in ftrace:

 # echo 1 > /sys/kernel/debug/tracing/events/enable

[console]
event trace: Could not enable event function

This is because when enabling all events via the debugfs system
it ignores events that do not have a ->reg() function assigned.
This was to skip over the ftrace internal events (as they are
not TRACE_EVENTs). But as the ftrace function event now has
a ->reg() function attached to it for use with perf, it is no
longer ignored.

Worse yet, this ->reg() function is being called when it should
not be. It returns an error and causes the above warning to
be printed.

By adding a new event_call flag (TRACE_EVENT_FL_IGNORE_ENABLE)
and have all ftrace internel event structures have it set,
setting the events/enable will no longe try to incorrectly enable
the function event and does not warn.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 5f3f3be5af09..176a939d1547 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -179,6 +179,7 @@ enum {
         TRACE_EVENT_FL_RECORDED_CMD_BIT,
         TRACE_EVENT_FL_CAP_ANY_BIT,
         TRACE_EVENT_FL_NO_SET_FILTER_BIT,
+        TRACE_EVENT_FL_IGNORE_ENABLE_BIT,
 };
 
 enum {
@@ -187,6 +188,7 @@ enum {
         TRACE_EVENT_FL_RECORDED_CMD     = (1 << TRACE_EVENT_FL_RECORDED_CMD_BIT),
         TRACE_EVENT_FL_CAP_ANY          = (1 << TRACE_EVENT_FL_CAP_ANY_BIT),
         TRACE_EVENT_FL_NO_SET_FILTER    = (1 << TRACE_EVENT_FL_NO_SET_FILTER_BIT),
+        TRACE_EVENT_FL_IGNORE_ENABLE    = (1 << TRACE_EVENT_FL_IGNORE_ENABLE_BIT),
 };
 
 struct ftrace_event_call {
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 079a93ae8a9d..29111da1d100 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -294,6 +294,9 @@ static int __ftrace_set_clr_event(const char *match, const char *sub,
                 if (!call->name || !call->class || !call->class->reg)
                         continue;
 
+                if (call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
+                        continue;
+
                 if (match &&
                     strcmp(match, call->name) != 0 &&
                     strcmp(match, call->class->system) != 0)
@@ -1164,7 +1167,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
                 return -1;
         }
 
-        if (call->class->reg)
+        if (call->class->reg && !(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
                 trace_create_file("enable", 0644, call->dir, call,
                                   enable);
 
diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
index 3dd15e8bc856..e039906b037d 100644
--- a/kernel/trace/trace_export.c
+++ b/kernel/trace/trace_export.c
@@ -180,6 +180,7 @@ struct ftrace_event_call __used event_##call = {			\
         .event.type             = etype,                                \
         .class                  = &event_class_ftrace_##call,           \
         .print_fmt              = print,                                \
+        .flags                  = TRACE_EVENT_FL_IGNORE_ENABLE,         \
 };                                                                      \
 struct ftrace_event_call __used                                         \
 __attribute__((section("_ftrace_events"))) *__event_##call = &event_##call;