lib/dynamic_debug.c: use kstrdup_const

Using kstrdup_const, thus reusing .rodata when possible, saves around 2 kB
of runtime memory on my laptop/.config combination.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Jason Baron <jbaron@akamai.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/dynamic_debug.c

@@ -42,7 +42,7 @@ extern struct _ddebug __stop___verbose[];
 
 struct ddebug_table {
 	struct list_head link;
-	char *mod_name;
+	const char *mod_name;
 	unsigned int num_ddebugs;
 	struct _ddebug *ddebugs;
 };
@@ -841,12 +841,12 @@ int ddebug_add_module(struct _ddebug *tab, unsigned int n,
 			     const char *name)
 {
 	struct ddebug_table *dt;
-	char *new_name;
+	const char *new_name;
 
 	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
 	if (dt == NULL)
 		return -ENOMEM;
-	new_name = kstrdup(name, GFP_KERNEL);
+	new_name = kstrdup_const(name, GFP_KERNEL);
 	if (new_name == NULL) {
 		kfree(dt);
 		return -ENOMEM;
@@ -907,7 +907,7 @@ 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(dt->mod_name);
+	kfree_const(dt->mod_name);
 	kfree(dt);
 }