tracing: Allow for modules to convert their enums to values

Update the infrastructure such that modules that declare TRACE_DEFINE_ENUM()
will have those enums converted into their values in the tracepoint
print fmt strings.

Link: http://lkml.kernel.org/r/87vbhjp74q.fsf@rustcorp.com.au

Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 49 insertions, 5 deletions

diff --git a/kernel/module.c b/kernel/module.c
index b3d634ed06c9..d8f8ab271c2b 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2753,6 +2753,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
         mod->trace_events = section_objs(info, "_ftrace_events",
                                          sizeof(*mod->trace_events),
                                          &mod->num_trace_events);
+        mod->trace_enums = section_objs(info, "_ftrace_enum_map",
+                                        sizeof(*mod->trace_enums),
+                                        &mod->num_trace_enums);
 #endif
 #ifdef CONFIG_TRACING
         mod->trace_bprintk_fmt_start = section_objs(info, "__trace_printk_fmt",
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ebf49649534c..28e6654e640d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3908,11 +3908,9 @@ static const struct file_operations tracing_saved_cmdlines_size_fops = {
         .write          = tracing_saved_cmdlines_size_write,
 };
 
-static void
-trace_insert_enum_map(struct trace_enum_map **start, struct trace_enum_map **stop)
+static void trace_insert_enum_map(struct trace_enum_map **start, int len)
 {
         struct trace_enum_map **map;
-        int len = stop - start;
 
         if (len <= 0)
                 return;
@@ -6561,9 +6559,48 @@ extern struct trace_enum_map *__stop_ftrace_enum_maps[];
 
 static void __init trace_enum_init(void)
 {
-        trace_insert_enum_map(__start_ftrace_enum_maps, __stop_ftrace_enum_maps);
+        int len;
+
+        len = __stop_ftrace_enum_maps - __start_ftrace_enum_maps;
+        trace_insert_enum_map(__start_ftrace_enum_maps, len);
+}
+
+#ifdef CONFIG_MODULES
+static void trace_module_add_enums(struct module *mod)
+{
+        if (!mod->num_trace_enums)
+                return;
+
+        /*
+         * Modules with bad taint do not have events created, do
+         * not bother with enums either.
+         */
+        if (trace_module_has_bad_taint(mod))
+                return;
+
+        trace_insert_enum_map(mod->trace_enums, mod->num_trace_enums);
+}
+
+static int trace_module_notify(struct notifier_block *self,
+                               unsigned long val, void *data)
+{
+        struct module *mod = data;
+
+        switch (val) {
+        case MODULE_STATE_COMING:
+                trace_module_add_enums(mod);
+                break;
+        }
+
+        return 0;
 }
 
+static struct notifier_block trace_module_nb = {
+        .notifier_call = trace_module_notify,
+        .priority = 0,
+};
+#endif
+
 static __init int tracer_init_debugfs(void)
 {
         struct dentry *d_tracer;
@@ -6590,6 +6627,10 @@ static __init int tracer_init_debugfs(void)
 
         trace_enum_init();
 
+#ifdef CONFIG_MODULES
+        register_module_notifier(&trace_module_nb);
+#endif
+
 #ifdef CONFIG_DYNAMIC_FTRACE
         trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
                         &ftrace_update_tot_cnt, &tracing_dyn_info_fops);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index fc58c50fbf01..a576bbe75577 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2034,7 +2034,7 @@ static int trace_module_notify(struct notifier_block *self,
 
 static struct notifier_block trace_module_nb = {
         .notifier_call = trace_module_notify,
-        .priority = 0,
+        .priority = 1, /* higher than trace.c module notify */
 };
 #endif /* CONFIG_MODULES */