tracing: Fix trace events build without modules

The new multi-buffers added a descriptor that kept track of module
events, and the directories they use, with struct ftace_module_file_ops.
This is used to add a ref count to keep modules from unloading while
their files are being accessed.

As the descriptor is only needed when CONFIG_MODULES is enabled, it
is only declared when the config is enabled. But that struct is
dereferenced in a few areas outside the #ifdef CONFIG_MODULES.

By adding some helper routines and moving code around a little,
events can be compiled again without modules.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 36 insertions, 19 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 63b4bdf84593..0f1307a29fcf 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1546,9 +1546,18 @@ struct ftrace_module_file_ops {
         struct file_operations          filter;
 };
 
-static struct ftrace_module_file_ops *find_ftrace_file_ops(struct module *mod)
+static struct ftrace_module_file_ops *
+find_ftrace_file_ops(struct ftrace_module_file_ops *file_ops, struct module *mod)
 {
-        struct ftrace_module_file_ops *file_ops;
+        /*
+         * As event_calls are added in groups by module,
+         * when we find one file_ops, we don't need to search for
+         * each call in that module, as the rest should be the
+         * same. Only search for a new one if the last one did
+         * not match.
+         */
+        if (file_ops && mod == file_ops->mod)
+                return file_ops;
 
         list_for_each_entry(file_ops, &ftrace_module_file_list, list) {
                 if (file_ops->mod == mod)
@@ -1664,16 +1673,35 @@ static int trace_module_notify(struct notifier_block *self,
 
         return 0;
 }
+
+static int
+__trace_add_new_mod_event(struct ftrace_event_call *call,
+                          struct trace_array *tr,
+                          struct ftrace_module_file_ops *file_ops)
+{
+        return __trace_add_new_event(call, tr,
+                                     &file_ops->id, &file_ops->enable,
+                                     &file_ops->filter, &file_ops->format);
+}
+
 #else
-static struct ftrace_module_file_ops *find_ftrace_file_ops(struct module *mod)
+static inline struct ftrace_module_file_ops *
+find_ftrace_file_ops(struct ftrace_module_file_ops *file_ops, struct module *mod)
 {
         return NULL;
 }
-static int trace_module_notify(struct notifier_block *self,
-                               unsigned long val, void *data)
+static inline int trace_module_notify(struct notifier_block *self,
+                                      unsigned long val, void *data)
 {
         return 0;
 }
+static inline int
+__trace_add_new_mod_event(struct ftrace_event_call *call,
+                          struct trace_array *tr,
+                          struct ftrace_module_file_ops *file_ops)
+{
+        return -ENODEV;
+}
 #endif /* CONFIG_MODULES */
 
 /* Create a new event directory structure for a trace directory. */
@@ -1692,20 +1720,11 @@ __trace_add_event_dirs(struct trace_array *tr)
                          * want the module to disappear when reading one
                          * of these files). The file_ops keep account of
                          * the module ref count.
-                         *
-                         * As event_calls are added in groups by module,
-                         * when we find one file_ops, we don't need to search for
-                         * each call in that module, as the rest should be the
-                         * same. Only search for a new one if the last one did
-                         * not match.
                          */
-                        if (!file_ops || call->mod != file_ops->mod)
-                                file_ops = find_ftrace_file_ops(call->mod);
+                        file_ops = find_ftrace_file_ops(file_ops, call->mod);
                         if (!file_ops)
                                 continue; /* Warn? */
-                        ret = __trace_add_new_event(call, tr,
-                                        &file_ops->id, &file_ops->enable,
-                                        &file_ops->filter, &file_ops->format);
+                        ret = __trace_add_new_mod_event(call, tr, file_ops);
                         if (ret < 0)
                                 pr_warning("Could not create directory for event %s\n",
                                            call->name);
@@ -1794,9 +1813,7 @@ __add_event_to_tracers(struct ftrace_event_call *call,
 
         list_for_each_entry(tr, &ftrace_trace_arrays, list) {
                 if (file_ops)
-                        __trace_add_new_event(call, tr,
-                                              &file_ops->id, &file_ops->enable,
-                                              &file_ops->filter, &file_ops->format);
+                        __trace_add_new_mod_event(call, tr, file_ops);
                 else
                         __trace_add_new_event(call, tr,
                                               &ftrace_event_id_fops,