tracing: Add DYNAMIC flag for dynamic events

To differentiate between static and dynamic events, add a new flag
DYNAMIC to the event flags that all dynamic events have set. This will
allow to differentiate when attaching to a dynamic event from a static
event.

Static events have a mod pointer that references the module they were
created in (or NULL for core kernel). This can be incremented when the
event has something attached to it. But there exists no such mechanism for
dynamic events. This is dangerous as the dynamic events may now disappear
without the "attachment" knowing that it no longer exists.

To enforce the dynamic flag, change dyn_event_add() to pass the event that
is being created such that it can set the DYNAMIC flag of the event. This
helps make sure that no location that creates a dynamic event misses
setting this flag.

Link: https://lore.kernel.org/linux-trace-devel/20210813004448.51c7de69ce432d338f4d226b@kernel.org/
Link: https://lkml.kernel.org/r/20210817035026.936958254@goodmis.org
Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index ad413b3..53c9dff 100644 (file)
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -310,6 +310,7 @@ enum {
        TRACE_EVENT_FL_NO_SET_FILTER_BIT,
        TRACE_EVENT_FL_IGNORE_ENABLE_BIT,
        TRACE_EVENT_FL_TRACEPOINT_BIT,
+       TRACE_EVENT_FL_DYNAMIC_BIT,
        TRACE_EVENT_FL_KPROBE_BIT,
        TRACE_EVENT_FL_UPROBE_BIT,
 };
@@ -321,6 +322,7 @@ enum {
  *  NO_SET_FILTER - Set when filter has error and is to be ignored
  *  IGNORE_ENABLE - For trace internal events, do not enable with debugfs file
  *  TRACEPOINT    - Event is a tracepoint
+ *  DYNAMIC       - Event is a dynamic event (created at run time)
  *  KPROBE        - Event is a kprobe
  *  UPROBE        - Event is a uprobe
  */
@@ -330,6 +332,7 @@ enum {
        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),
        TRACE_EVENT_FL_TRACEPOINT       = (1 << TRACE_EVENT_FL_TRACEPOINT_BIT),
+       TRACE_EVENT_FL_DYNAMIC          = (1 << TRACE_EVENT_FL_DYNAMIC_BIT),
        TRACE_EVENT_FL_KPROBE           = (1 << TRACE_EVENT_FL_KPROBE_BIT),
        TRACE_EVENT_FL_UPROBE           = (1 << TRACE_EVENT_FL_UPROBE_BIT),
 };

diff --git a/kernel/trace/trace_dynevent.h b/kernel/trace/trace_dynevent.h
index 7754936..936477a 100644 (file)
--- a/kernel/trace/trace_dynevent.h
+++ b/kernel/trace/trace_dynevent.h
@@ -76,13 +76,15 @@ int dyn_event_init(struct dyn_event *ev, struct dyn_event_operations *ops)
        return 0;
 }
 
-static inline int dyn_event_add(struct dyn_event *ev)
+static inline int dyn_event_add(struct dyn_event *ev,
+                               struct trace_event_call *call)
 {
        lockdep_assert_held(&event_mutex);
 
        if (!ev || !ev->ops)
                return -EINVAL;
 
+       call->flags |= TRACE_EVENT_FL_DYNAMIC;
        list_add_tail(&ev->list, &dyn_event_list);
        return 0;
 }

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 9315fc0..f4f5489 100644 (file)
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -1298,7 +1298,7 @@ static int __create_synth_event(const char *name, const char *raw_fields)
        }
        ret = register_synth_event(event);
        if (!ret)
-               dyn_event_add(&event->devent);
+               dyn_event_add(&event->devent, &event->call);
        else
                free_synth_event(event);
  out:

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ea6178c..bfef43b 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -618,7 +618,7 @@ static int append_trace_kprobe(struct trace_kprobe *tk, struct trace_kprobe *to)
        if (ret)
                trace_probe_unlink(&tk->tp);
        else
-               dyn_event_add(&tk->devent);
+               dyn_event_add(&tk->devent, trace_probe_event_call(&tk->tp));
 
        return ret;
 }
@@ -661,7 +661,7 @@ static int register_trace_kprobe(struct trace_kprobe *tk)
        if (ret < 0)
                unregister_kprobe_event(tk);
        else
-               dyn_event_add(&tk->devent);
+               dyn_event_add(&tk->devent, trace_probe_event_call(&tk->tp));
 
 end:
        mutex_unlock(&event_mutex);

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 9b50869..50eca53 100644 (file)
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -455,7 +455,7 @@ static int append_trace_uprobe(struct trace_uprobe *tu, struct trace_uprobe *to)
        /* Append to existing event */
        ret = trace_probe_append(&tu->tp, &to->tp);
        if (!ret)
-               dyn_event_add(&tu->devent);
+               dyn_event_add(&tu->devent, trace_probe_event_call(&tu->tp));
 
        return ret;
 }
@@ -518,7 +518,7 @@ static int register_trace_uprobe(struct trace_uprobe *tu)
                goto end;
        }
 
-       dyn_event_add(&tu->devent);
+       dyn_event_add(&tu->devent, trace_probe_event_call(&tu->tp));
 
 end:
        mutex_unlock(&event_mutex);