dynamic_debug: don't duplicate modname in ddebug_add_module

For built-in modules, we're already reusing the passed-in string via
kstrdup_const().  But for actual modules (i.e.  when we're called from
dynamic_debug_setup in module.c), the passed-in string (which points at
the name[] array inside struct module) is also guaranteed to live at
least as long as the struct ddebug_table, since free_module() calls
ddebug_remove_module().

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Rasmus Villemoes <[email protected]>
Acked-by: Jason Baron <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: "Rafael J . Wysocki" <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

lib/dynamic_debug.c

@@ -847,17 +847,17 @@ int ddebug_add_module(struct _ddebug *tab, unsigned int n,
 			     const char *name)
 {
 	struct ddebug_table *dt;
-	const char *new_name;
 
 	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
 	if (dt == NULL)
 		return -ENOMEM;
-	new_name = kstrdup_const(name, GFP_KERNEL);
-	if (new_name == NULL) {
-		kfree(dt);
-		return -ENOMEM;
-	}
-	dt->mod_name = new_name;
+	/*
+	 * For built-in modules, name lives in .rodata and is
+	 * immortal. For loaded modules, name points at the name[]
+	 * member of struct module, which lives at least as long as
+	 * this struct ddebug_table.
+	 */
+	dt->mod_name = name;
 	dt->num_ddebugs = n;
 	dt->ddebugs = tab;
 
@@ -913,7 +913,6 @@ int ddebug_dyndbg_module_param_cb(char *param, char *val, const char *module)
 static void ddebug_table_free(struct ddebug_table *dt)
 {
 	list_del_init(&dt->link);
-	kfree_const(dt->mod_name);
 	kfree(dt);
 }