[PATCH 3/3] Enforce "unsigned long flags;" when spinlocking

[Alexey Dobriyan]

Make it break or warn if you pass to spin_lock_irqsave() and friends
something different from "unsigned long flags;". Suprisingly large amount of
these was caught by recent commit c53421b18f205c5f97c604ae55c6a921f034b0f6 .

Idea is largely from FRV typechecking.

Note #1: checking with sparse is still needed, because a driver can save and
         pass around flags or something. So far patch is very intrusive.
Note #2: techically, we should break only if sizeof(flags) < sizeof(unsigned long),
         but hey, there is opportunity to escalate. Thus !=
Note #3: yes, would break every single buggy out-of-tree module.

Signed-off-by: Alexey "altruistic today" Dobriyan <adobriyan@xxxxxxxxx>
---

 include/linux/irqflags.h |   11 ++++++-
 include/linux/spinlock.h |   68 ++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 65 insertions(+), 14 deletions(-)

--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -49,11 +49,18 @@ #define local_irq_enable() \
 	do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
 #define local_irq_disable() \
 	do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0)
-#define local_irq_save(flags) \
-	do { raw_local_irq_save(flags); trace_hardirqs_off(); } while (0)
+#define local_irq_save(flags)						\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		raw_local_irq_save(flags);				\
+		trace_hardirqs_off();					\
+	} while (0)
 
 #define local_irq_restore(flags)				\
 	do {							\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
 		if (raw_irqs_disabled_flags(flags)) {		\
 			raw_local_irq_restore(flags);		\
 			trace_hardirqs_off();			\
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -183,13 +183,43 @@ #define write_lock(lock)		_write_lock(lo
 #define read_lock(lock)			_read_lock(lock)
 
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-#define spin_lock_irqsave(lock, flags)	flags = _spin_lock_irqsave(lock)
-#define read_lock_irqsave(lock, flags)	flags = _read_lock_irqsave(lock)
-#define write_lock_irqsave(lock, flags)	flags = _write_lock_irqsave(lock)
+#define spin_lock_irqsave(lock, flags)					\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		flags = _spin_lock_irqsave(lock);			\
+	} while (0);
+#define read_lock_irqsave(lock, flags)					\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		flags = _read_lock_irqsave(lock);			\
+	} while (0)
+#define write_lock_irqsave(lock, flags)					\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		flags = _write_lock_irqsave(lock);			\
+	} while (0)
 #else
-#define spin_lock_irqsave(lock, flags)	_spin_lock_irqsave(lock, flags)
-#define read_lock_irqsave(lock, flags)	_read_lock_irqsave(lock, flags)
-#define write_lock_irqsave(lock, flags)	_write_lock_irqsave(lock, flags)
+#define spin_lock_irqsave(lock, flags)					\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		_spin_lock_irqsave(lock, flags);			\
+	} while (0)
+#define read_lock_irqsave(lock, flags)					\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		_read_lock_irqsave(lock, flags);			\
+	} while (0)
+#define write_lock_irqsave(lock, flags)					\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		_write_lock_irqsave(lock, flags);			\
+	} while (0)
 #endif
 
 #define spin_lock_irq(lock)		_spin_lock_irq(lock)
@@ -224,22 +254,36 @@ # define write_unlock_irq(lock) \
     do { __raw_write_unlock(&(lock)->raw_lock); local_irq_enable(); } while (0)
 #endif
 
-#define spin_unlock_irqrestore(lock, flags) \
-					_spin_unlock_irqrestore(lock, flags)
+#define spin_unlock_irqrestore(lock, flags)				\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		_spin_unlock_irqrestore(lock, flags);			\
+	} while (0)
 #define spin_unlock_bh(lock)		_spin_unlock_bh(lock)
 
-#define read_unlock_irqrestore(lock, flags) \
-					_read_unlock_irqrestore(lock, flags)
+#define read_unlock_irqrestore(lock, flags)				\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		_read_unlock_irqrestore(lock, flags);			\
+	} while (0)
 #define read_unlock_bh(lock)		_read_unlock_bh(lock)
 
-#define write_unlock_irqrestore(lock, flags) \
-					_write_unlock_irqrestore(lock, flags)
+#define write_unlock_irqrestore(lock, flags)				\
+	do {								\
+		BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+		typecheck(unsigned long, flags);			\
+		_write_unlock_irqrestore(lock, flags);			\
+	} while (0)
 #define write_unlock_bh(lock)		_write_unlock_bh(lock)
 
 #define spin_trylock_bh(lock)	__cond_lock(lock, _spin_trylock_bh(lock))
 
 #define spin_trylock_irq(lock) \
 ({ \
+	BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long));	\
+	typecheck(unsigned long, flags);			\
 	local_irq_disable(); \
 	spin_trylock(lock) ? \
 	1 : ({ local_irq_enable(); 0;  }); \

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