x86: Generate cmpxchg build failures

Rework the x86 cmpxchg() implementation to generate build failures
when used on improper types.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1254771187.21044.22.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 86 insertions, 132 deletions

diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
index 82ceb788a98..5371174cf5d 100644
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -8,14 +8,50 @@
  *       you need to test for the feature in boot_cpu_data.
  */
 
-#define xchg(ptr, v)							\
-	((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), sizeof(*(ptr))))
+extern void __xchg_wrong_size(void);
+
+/*
+ * Note: no "lock" prefix even on SMP: xchg always implies lock anyway
+ * Note 2: xchg has side effect, so that attribute volatile is necessary,
+ *	  but generally the primitive is invalid, *ptr is output argument. --ANK
+ */
 
 struct __xchg_dummy {
 	unsigned long a[100];
 };
 #define __xg(x) ((struct __xchg_dummy *)(x))
 
+#define __xchg(x, ptr, size)						\
+({									\
+	__typeof(*(ptr)) __x = (x);					\
+	switch (size) {							\
+	case 1:								\
+		asm volatile("xchgb %b0,%1"				\
+			     : "=q" (__x)				\
+			     : "m" (*__xg(ptr)), "0" (__x)		\
+			     : "memory");				\
+		break;							\
+	case 2:								\
+		asm volatile("xchgw %w0,%1"				\
+			     : "=r" (__x)				\
+			     : "m" (*__xg(ptr)), "0" (__x)		\
+			     : "memory");				\
+		break;							\
+	case 4:								\
+		asm volatile("xchgl %0,%1"				\
+			     : "=r" (__x)				\
+			     : "m" (*__xg(ptr)), "0" (__x)		\
+			     : "memory");				\
+		break;							\
+	default:							\
+		__xchg_wrong_size();					\
+	}								\
+	__x;								\
+})
+
+#define xchg(ptr, v)							\
+	__xchg((v), (ptr), sizeof(*ptr))
+
 /*
  * The semantics of XCHGCMP8B are a bit strange, this is why
  * there is a loop and the loading of %%eax and %%edx has to
@@ -71,57 +107,63 @@ static inline void __set_64bit_var(unsigned long long *ptr,
 		       (unsigned int)((value) >> 32))			\
 	 : __set_64bit(ptr, ll_low((value)), ll_high((value))))
 
-/*
- * Note: no "lock" prefix even on SMP: xchg always implies lock anyway
- * Note 2: xchg has side effect, so that attribute volatile is necessary,
- *	  but generally the primitive is invalid, *ptr is output argument. --ANK
- */
-static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
-				   int size)
-{
-	switch (size) {
-	case 1:
-		asm volatile("xchgb %b0,%1"
-			     : "=q" (x)
-			     : "m" (*__xg(ptr)), "0" (x)
-			     : "memory");
-		break;
-	case 2:
-		asm volatile("xchgw %w0,%1"
-			     : "=r" (x)
-			     : "m" (*__xg(ptr)), "0" (x)
-			     : "memory");
-		break;
-	case 4:
-		asm volatile("xchgl %0,%1"
-			     : "=r" (x)
-			     : "m" (*__xg(ptr)), "0" (x)
-			     : "memory");
-		break;
-	}
-	return x;
-}
+extern void __cmpxchg_wrong_size(void);
 
 /*
  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
  * store NEW in MEM.  Return the initial value in MEM.  Success is
  * indicated by comparing RETURN with OLD.
  */
+#define __raw_cmpxchg(ptr, old, new, size, lock)			\
+({									\
+	__typeof__(*(ptr)) __ret;					\
+	__typeof__(*(ptr)) __old = (old);				\
+	__typeof__(*(ptr)) __new = (new);				\
+	switch (size) {							\
+	case 1:								\
+		asm volatile(lock "cmpxchgb %b1,%2"			\
+			     : "=a"(__ret)				\
+			     : "q"(__new), "m"(*__xg(ptr)), "0"(__old)	\
+			     : "memory");				\
+		break;							\
+	case 2:								\
+		asm volatile(lock "cmpxchgw %w1,%2"			\
+			     : "=a"(__ret)				\
+			     : "r"(__new), "m"(*__xg(ptr)), "0"(__old)	\
+			     : "memory");				\
+		break;							\
+	case 4:								\
+		asm volatile(lock "cmpxchgl %1,%2"			\
+			     : "=a"(__ret)				\
+			     : "r"(__new), "m"(*__xg(ptr)), "0"(__old)	\
+			     : "memory");				\
+		break;							\
+	default:							\
+		__cmpxchg_wrong_size();					\
+	}								\
+	__ret;								\
+})
+
+#define __cmpxchg(ptr, old, new, size)					\
+	__raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
+
+#define __sync_cmpxchg(ptr, old, new, size)				\
+	__raw_cmpxchg((ptr), (old), (new), (size), "lock; ")
+
+#define __cmpxchg_local(ptr, old, new, size)				\
+	__raw_cmpxchg((ptr), (old), (new), (size), "")
 
 #ifdef CONFIG_X86_CMPXCHG
 #define __HAVE_ARCH_CMPXCHG 1
-#define cmpxchg(ptr, o, n)						\
-	((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o),	\
-				       (unsigned long)(n),		\
-				       sizeof(*(ptr))))
-#define sync_cmpxchg(ptr, o, n)						\
-	((__typeof__(*(ptr)))__sync_cmpxchg((ptr), (unsigned long)(o),	\
-					    (unsigned long)(n),		\
-					    sizeof(*(ptr))))
-#define cmpxchg_local(ptr, o, n)					\
-	((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o),	\
-					     (unsigned long)(n),	\
-					     sizeof(*(ptr))))
+
+#define cmpxchg(ptr, old, new)						\
+	__cmpxchg((ptr), (old), (new), sizeof(*ptr))
+
+#define sync_cmpxchg(ptr, old, new)					\
+	__sync_cmpxchg((ptr), (old), (new), sizeof(*ptr))
+
+#define cmpxchg_local(ptr, old, new)					\
+	__cmpxchg_local((ptr), (old), (new), sizeof(*ptr))
 #endif
 
 #ifdef CONFIG_X86_CMPXCHG64
@@ -133,94 +175,6 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
 					       (unsigned long long)(n)))
 #endif
 
-static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
-				      unsigned long new, int size)
-{
-	unsigned long prev;
-	switch (size) {
-	case 1:
-		asm volatile(LOCK_PREFIX "cmpxchgb %b1,%2"
-			     : "=a"(prev)
-			     : "q"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	case 2:
-		asm volatile(LOCK_PREFIX "cmpxchgw %w1,%2"
-			     : "=a"(prev)
-			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	case 4:
-		asm volatile(LOCK_PREFIX "cmpxchgl %1,%2"
-			     : "=a"(prev)
-			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	}
-	return old;
-}
-
-/*
- * Always use locked operations when touching memory shared with a
- * hypervisor, since the system may be SMP even if the guest kernel
- * isn't.
- */
-static inline unsigned long __sync_cmpxchg(volatile void *ptr,
-					   unsigned long old,
-					   unsigned long new, int size)
-{
-	unsigned long prev;
-	switch (size) {
-	case 1:
-		asm volatile("lock; cmpxchgb %b1,%2"
-			     : "=a"(prev)
-			     : "q"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	case 2:
-		asm volatile("lock; cmpxchgw %w1,%2"
-			     : "=a"(prev)
-			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	case 4:
-		asm volatile("lock; cmpxchgl %1,%2"
-			     : "=a"(prev)
-			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	}
-	return old;
-}
-
-static inline unsigned long __cmpxchg_local(volatile void *ptr,
-					    unsigned long old,
-					    unsigned long new, int size)
-{
-	unsigned long prev;
-	switch (size) {
-	case 1:
-		asm volatile("cmpxchgb %b1,%2"
-			     : "=a"(prev)
-			     : "q"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	case 2:
-		asm volatile("cmpxchgw %w1,%2"
-			     : "=a"(prev)
-			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	case 4:
-		asm volatile("cmpxchgl %1,%2"
-			     : "=a"(prev)
-			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
-			     : "memory");
-		return prev;
-	}
-	return old;
-}
-
 static inline unsigned long long __cmpxchg64(volatile void *ptr,
 					     unsigned long long old,
 					     unsigned long long new)