1 files changed, 113 insertions, 8 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 84427441824e..c73bc4334bee 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -143,6 +143,9 @@ static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
  * nr_lock_classes is the number of elements of lock_classes[] that is
  * in use.
  */
+#define KEYHASH_BITS		(MAX_LOCKDEP_KEYS_BITS - 1)
+#define KEYHASH_SIZE		(1UL << KEYHASH_BITS)
+static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
 unsigned long nr_lock_classes;
 #ifndef CONFIG_DEBUG_LOCKDEP
 static
@@ -641,7 +644,7 @@ static int very_verbose(struct lock_class *class)
  * Is this the address of a static object:
  */
 #ifdef __KERNEL__
-static int static_obj(void *obj)
+static int static_obj(const void *obj)
 {
 	unsigned long start = (unsigned long) &_stext,
 		      end   = (unsigned long) &_end,
@@ -975,6 +978,71 @@ static void init_data_structures_once(void)
 	}
 }
 
+static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
+{
+	unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
+
+	return lock_keys_hash + hash;
+}
+
+/* Register a dynamically allocated key. */
+void lockdep_register_key(struct lock_class_key *key)
+{
+	struct hlist_head *hash_head;
+	struct lock_class_key *k;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(static_obj(key)))
+		return;
+	hash_head = keyhashentry(key);
+
+	raw_local_irq_save(flags);
+	if (!graph_lock())
+		goto restore_irqs;
+	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
+		if (WARN_ON_ONCE(k == key))
+			goto out_unlock;
+	}
+	hlist_add_head_rcu(&key->hash_entry, hash_head);
+out_unlock:
+	graph_unlock();
+restore_irqs:
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lockdep_register_key);
+
+/* Check whether a key has been registered as a dynamic key. */
+static bool is_dynamic_key(const struct lock_class_key *key)
+{
+	struct hlist_head *hash_head;
+	struct lock_class_key *k;
+	bool found = false;
+
+	if (WARN_ON_ONCE(static_obj(key)))
+		return false;
+
+	/*
+	 * If lock debugging is disabled lock_keys_hash[] may contain
+	 * pointers to memory that has already been freed. Avoid triggering
+	 * a use-after-free in that case by returning early.
+	 */
+	if (!debug_locks)
+		return true;
+
+	hash_head = keyhashentry(key);
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
+		if (k == key) {
+			found = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return found;
+}
+
 /*
  * Register a lock's class in the hash-table, if the class is not present
  * yet. Otherwise we look it up. We cache the result in the lock object
@@ -996,7 +1064,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 	if (!lock->key) {
 		if (!assign_lock_key(lock))
 			return NULL;
-	} else if (!static_obj(lock->key)) {
+	} else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
 		return NULL;
 	}
 
@@ -3378,13 +3446,12 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name,
 	if (DEBUG_LOCKS_WARN_ON(!key))
 		return;
 	/*
-	 * Sanity check, the lock-class key must be persistent:
+	 * Sanity check, the lock-class key must either have been allocated
+	 * statically or must have been registered as a dynamic key.
 	 */
-	if (!static_obj(key)) {
-		printk("BUG: key %px not in .data!\n", key);
-		/*
-		 * What it says above ^^^^^, I suggest you read it.
-		 */
+	if (!static_obj(key) && !is_dynamic_key(key)) {
+		if (debug_locks)
+			printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
 		DEBUG_LOCKS_WARN_ON(1);
 		return;
 	}
@@ -4795,6 +4862,44 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 		lockdep_reset_lock_reg(lock);
 }
 
+/* Unregister a dynamically allocated key. */
+void lockdep_unregister_key(struct lock_class_key *key)
+{
+	struct hlist_head *hash_head = keyhashentry(key);
+	struct lock_class_key *k;
+	struct pending_free *pf;
+	unsigned long flags;
+	bool found = false;
+
+	might_sleep();
+
+	if (WARN_ON_ONCE(static_obj(key)))
+		return;
+
+	raw_local_irq_save(flags);
+	if (!graph_lock())
+		goto out_irq;
+
+	pf = get_pending_free();
+	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
+		if (k == key) {
+			hlist_del_rcu(&k->hash_entry);
+			found = true;
+			break;
+		}
+	}
+	WARN_ON_ONCE(!found);
+	__lockdep_free_key_range(pf, key, 1);
+	call_rcu_zapped(pf);
+	graph_unlock();
+out_irq:
+	raw_local_irq_restore(flags);
+
+	/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
+	synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(lockdep_unregister_key);
+
 void __init lockdep_init(void)
 {
 	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");