tracing: Do not add event files for modules that fail tracepoints

commit 45ab2813d40d88fc575e753c38478de242d03f88 upstream.

If a module fails to add its tracepoints due to module tainting, do not
create the module event infrastructure in the debugfs directory. As the events
will not work and worse yet, they will silently fail, making the user wonder
why the events they enable do not display anything.

Having a warning on module load and the events not visible to the users
will make the cause of the problem much clearer.

Link: http://lkml.kernel.org/r/20140227154923.265882695@goodmis.org
Fixes: 6d723736e472 "tracing/events: add support for modules to TRACE_EVENT"
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index df0a779c1bbdb7d04bed9f9acdde80d16abaf2ce..f3680aa895bca7b4702079be8e59b94c3065c268 100644 (file)
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -60,6 +60,12 @@ struct tp_module {
        unsigned int num_tracepoints;
        struct tracepoint * const *tracepoints_ptrs;
 };
+bool trace_module_has_bad_taint(struct module *mod);
+#else
+static inline bool trace_module_has_bad_taint(struct module *mod)
+{
+       return false;
+}
 #endif /* CONFIG_MODULES */
 
 struct tracepoint_iter {

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c212a7f934ec4841d8c9887ecf93f6a0b7526b27..875fed434e3b8a721bbdb2bc790a0a65d6138105 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1345,6 +1345,16 @@ static void trace_module_add_events(struct module *mod)
        struct ftrace_module_file_ops *file_ops = NULL;
        struct ftrace_event_call **call, **start, **end;
 
+       if (!mod->num_trace_events)
+               return;
+
+       /* Don't add infrastructure for mods without tracepoints */
+       if (trace_module_has_bad_taint(mod)) {
+               pr_err("%s: module has bad taint, not creating trace events\n",
+                      mod->name);
+               return;
+       }
+
        start = mod->trace_events;
        end = mod->trace_events + mod->num_trace_events;
 

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index f1539decd99d853d1a5c44fb3296072444aabf1a..41b25a0ed6168ba5df70038f1a0be0faba0a934d 100644 (file)
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -628,6 +628,11 @@ void tracepoint_iter_reset(struct tracepoint_iter *iter)
 EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
 
 #ifdef CONFIG_MODULES
+bool trace_module_has_bad_taint(struct module *mod)
+{
+       return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP));
+}
+
 static int tracepoint_module_coming(struct module *mod)
 {
        struct tp_module *tp_mod, *iter;
@@ -638,7 +643,7 @@ static int tracepoint_module_coming(struct module *mod)
         * module headers (for forced load), to make sure we don't cause a crash.
         * Staging and out-of-tree GPL modules are fine.
         */
-       if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)))
+       if (trace_module_has_bad_taint(mod))
                return 0;
        mutex_lock(&tracepoints_mutex);
        tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);