linux-kernel - [PATCH v7 17/23] locking/lockdep: Verify whether lock objects are small enough to be used as class keys

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Date:   Thu, 14 Feb 2019 15:00:52 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     peterz@...radead.org
Cc:     mingo@...hat.com, will.deacon@....com, tj@...nel.org,
        longman@...hat.com, johannes.berg@...el.com,
        linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
        Johannes Berg <johannes@...solutions.net>
Subject: [PATCH v7 17/23] locking/lockdep: Verify whether lock objects are small enough to be used as class keys

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Johannes Berg <johannes@...solutions.net>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 kernel/locking/lockdep.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index f5df97812dfa..93216e195b4f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -758,6 +758,17 @@ static bool assign_lock_key(struct lockdep_map *lock)
 {
 	unsigned long can_addr, addr = (unsigned long)lock;
 
+#ifdef __KERNEL__
+	/*
+	 * lockdep_free_key_range() assumes that struct lock_class_key
+	 * objects do not overlap. Since we use the address of lock
+	 * objects as class key for static objects, check whether the
+	 * size of lock_class_key objects does not exceed the size of
+	 * the smallest lock object.
+	 */
+	BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
+#endif
+
 	if (__is_kernel_percpu_address(addr, &can_addr))
 		lock->key = (void *)can_addr;
 	else if (__is_module_percpu_address(addr, &can_addr))
-- 
2.21.0.rc0.258.g878e2cd30e-goog