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/20190212214150.4807-6-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Jason Baron <jbaron@akamai.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index dbf2b45..8274c4e 100644 (file)
--- a/lib/dynamic_debug.c
+++ b/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);
 }