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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index bd96ecd0e05c731c7b55306b693fec2f81cc3d06..c49c363f5bfdf5f74df2db6fa7d2e7a94572c600 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 29111da1d1006c1f7b57a939b54517d17f315520..2f737f536c27220166b016f3122a4582330197cc 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1354,6 +1354,16 @@ 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 d96ba22dabfaaf38b9510c604050e07648119aa3..23d8560dbc56348d6cf1ff851a9d00867d93c6f8 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);