i386: improve and correct inline asm memory constraints

Use "+m" rather than a combination of "=m" and "m" for improved clarity
and consistency.

This also fixes some inlines that incorrectly didn't tell the compiler
that they read the old value at all, potentially causing the compiler to
generate bogus code.  It appear that all of those potential bugs were
hidden by the use of extra "volatile" specifiers on the data structures
in question, though.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-i386/atomic.h

@@ -46,8 +46,8 @@ static __inline__ void atomic_add(int i, atomic_t *v)
 {
 	__asm__ __volatile__(
 		LOCK_PREFIX "addl %1,%0"
-		:"=m" (v->counter)
-		:"ir" (i), "m" (v->counter));
+		:"+m" (v->counter)
+		:"ir" (i));
 }
 
 /**
@@ -61,8 +61,8 @@ static __inline__ void atomic_sub(int i, atomic_t *v)
 {
 	__asm__ __volatile__(
 		LOCK_PREFIX "subl %1,%0"
-		:"=m" (v->counter)
-		:"ir" (i), "m" (v->counter));
+		:"+m" (v->counter)
+		:"ir" (i));
 }
 
 /**
@@ -80,8 +80,8 @@ static __inline__ int atomic_sub_and_test(int i, atomic_t *v)
 
 	__asm__ __volatile__(
 		LOCK_PREFIX "subl %2,%0; sete %1"
-		:"=m" (v->counter), "=qm" (c)
-		:"ir" (i), "m" (v->counter) : "memory");
+		:"+m" (v->counter), "=qm" (c)
+		:"ir" (i) : "memory");
 	return c;
 }
 
@@ -95,8 +95,7 @@ static __inline__ void atomic_inc(atomic_t *v)
 {
 	__asm__ __volatile__(
 		LOCK_PREFIX "incl %0"
-		:"=m" (v->counter)
-		:"m" (v->counter));
+		:"+m" (v->counter));
 }
 
 /**
@@ -109,8 +108,7 @@ static __inline__ void atomic_dec(atomic_t *v)
 {
 	__asm__ __volatile__(
 		LOCK_PREFIX "decl %0"
-		:"=m" (v->counter)
-		:"m" (v->counter));
+		:"+m" (v->counter));
 }
 
 /**
@@ -127,8 +125,8 @@ static __inline__ int atomic_dec_and_test(atomic_t *v)
 
 	__asm__ __volatile__(
 		LOCK_PREFIX "decl %0; sete %1"
-		:"=m" (v->counter), "=qm" (c)
-		:"m" (v->counter) : "memory");
+		:"+m" (v->counter), "=qm" (c)
+		: : "memory");
 	return c != 0;
 }
 
@@ -146,8 +144,8 @@ static __inline__ int atomic_inc_and_test(atomic_t *v)
 
 	__asm__ __volatile__(
 		LOCK_PREFIX "incl %0; sete %1"
-		:"=m" (v->counter), "=qm" (c)
-		:"m" (v->counter) : "memory");
+		:"+m" (v->counter), "=qm" (c)
+		: : "memory");
 	return c != 0;
 }
 
@@ -166,8 +164,8 @@ static __inline__ int atomic_add_negative(int i, atomic_t *v)
 
 	__asm__ __volatile__(
 		LOCK_PREFIX "addl %2,%0; sets %1"
-		:"=m" (v->counter), "=qm" (c)
-		:"ir" (i), "m" (v->counter) : "memory");
+		:"+m" (v->counter), "=qm" (c)
+		:"ir" (i) : "memory");
 	return c;
 }
 

include/asm-i386/futex.h

@@ -20,8 +20,8 @@
 	.align	8\n\
 	.long	1b,3b\n\
 	.previous"						\
-	: "=r" (oldval), "=r" (ret), "=m" (*uaddr)		\
-	: "i" (-EFAULT), "m" (*uaddr), "0" (oparg), "1" (0))
+	: "=r" (oldval), "=r" (ret), "+m" (*uaddr)		\
+	: "i" (-EFAULT), "0" (oparg), "1" (0))
 
 #define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
   __asm__ __volatile (						\
@@ -38,9 +38,9 @@
 	.align	8\n\
 	.long	1b,4b,2b,4b\n\
 	.previous"						\
-	: "=&a" (oldval), "=&r" (ret), "=m" (*uaddr),		\
+	: "=&a" (oldval), "=&r" (ret), "+m" (*uaddr),		\
 	  "=&r" (tem)						\
-	: "r" (oparg), "i" (-EFAULT), "m" (*uaddr), "1" (0))
+	: "r" (oparg), "i" (-EFAULT), "1" (0))
 
 static inline int
 futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
@@ -123,7 +123,7 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 		"	.long   1b,3b				\n"
 		"	.previous				\n"
 
-		: "=a" (oldval), "=m" (*uaddr)
+		: "=a" (oldval), "+m" (*uaddr)
 		: "i" (-EFAULT), "r" (newval), "0" (oldval)
 		: "memory"
 	);

include/asm-i386/local.h

@@ -17,32 +17,30 @@ static __inline__ void local_inc(local_t *v)
 {
 	__asm__ __volatile__(
 		"incl %0"
-		:"=m" (v->counter)
-		:"m" (v->counter));
+		:"+m" (v->counter));
 }
 
 static __inline__ void local_dec(local_t *v)
 {
 	__asm__ __volatile__(
 		"decl %0"
-		:"=m" (v->counter)
-		:"m" (v->counter));
+		:"+m" (v->counter));
 }
 
 static __inline__ void local_add(long i, local_t *v)
 {
 	__asm__ __volatile__(
 		"addl %1,%0"
-		:"=m" (v->counter)
-		:"ir" (i), "m" (v->counter));
+		:"+m" (v->counter)
+		:"ir" (i));
 }
 
 static __inline__ void local_sub(long i, local_t *v)
 {
 	__asm__ __volatile__(
 		"subl %1,%0"
-		:"=m" (v->counter)
-		:"ir" (i), "m" (v->counter));
+		:"+m" (v->counter)
+		:"ir" (i));
 }
 
 /* On x86, these are no better than the atomic variants. */

include/asm-i386/posix_types.h

@@ -51,12 +51,12 @@ typedef struct {
 #undef	__FD_SET
 #define __FD_SET(fd,fdsetp) \
 		__asm__ __volatile__("btsl %1,%0": \
-			"=m" (*(__kernel_fd_set *) (fdsetp)):"r" ((int) (fd)))
+			"+m" (*(__kernel_fd_set *) (fdsetp)):"r" ((int) (fd)))
 
 #undef	__FD_CLR
 #define __FD_CLR(fd,fdsetp) \
 		__asm__ __volatile__("btrl %1,%0": \
-			"=m" (*(__kernel_fd_set *) (fdsetp)):"r" ((int) (fd)))
+			"+m" (*(__kernel_fd_set *) (fdsetp)):"r" ((int) (fd)))
 
 #undef	__FD_ISSET
 #define __FD_ISSET(fd,fdsetp) (__extension__ ({ \

include/asm-i386/rwlock.h

@@ -37,7 +37,7 @@
 			"popl %%eax\n\t" \
 			"1:\n", \
 			"subl $1,%0\n\t", \
-			"=m" (*(volatile int *)rw) : : "memory")
+			"+m" (*(volatile int *)rw) : : "memory")
 
 #define __build_read_lock(rw, helper)	do { \
 						if (__builtin_constant_p(rw)) \
@@ -63,7 +63,7 @@
 			"popl %%eax\n\t" \
 			"1:\n", \
 			"subl $" RW_LOCK_BIAS_STR ",%0\n\t", \
-			"=m" (*(volatile int *)rw) : : "memory")
+			"+m" (*(volatile int *)rw) : : "memory")
 
 #define __build_write_lock(rw, helper)	do { \
 						if (__builtin_constant_p(rw)) \

include/asm-i386/rwsem.h

@@ -111,8 +111,8 @@ LOCK_PREFIX	"  incl      (%%eax)\n\t" /* adds 0x00000001, returns the old value
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending down_read\n\t"
-		: "=m"(sem->count)
-		: "a"(sem), "m"(sem->count)
+		: "+m" (sem->count)
+		: "a" (sem)
 		: "memory", "cc");
 }
 
@@ -133,8 +133,8 @@ LOCK_PREFIX	"  cmpxchgl  %2,%0\n\t"
 		"  jnz	     1b\n\t"
 		"2:\n\t"
 		"# ending __down_read_trylock\n\t"
-		: "+m"(sem->count), "=&a"(result), "=&r"(tmp)
-		: "i"(RWSEM_ACTIVE_READ_BIAS)
+		: "+m" (sem->count), "=&a" (result), "=&r" (tmp)
+		: "i" (RWSEM_ACTIVE_READ_BIAS)
 		: "memory", "cc");
 	return result>=0 ? 1 : 0;
 }
@@ -161,8 +161,8 @@ LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending down_write"
-		: "=m"(sem->count), "=d"(tmp)
-		: "a"(sem), "1"(tmp), "m"(sem->count)
+		: "+m" (sem->count), "=d" (tmp)
+		: "a" (sem), "1" (tmp)
 		: "memory", "cc");
 }
 
@@ -205,8 +205,8 @@ LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtracts 1, returns the old valu
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending __up_read\n"
-		: "=m"(sem->count), "=d"(tmp)
-		: "a"(sem), "1"(tmp), "m"(sem->count)
+		: "+m" (sem->count), "=d" (tmp)
+		: "a" (sem), "1" (tmp)
 		: "memory", "cc");
 }
 
@@ -231,8 +231,8 @@ LOCK_PREFIX	"  xaddl     %%edx,(%%eax)\n\t" /* tries to transition 0xffff0001 ->
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending __up_write\n"
-		: "=m"(sem->count)
-		: "a"(sem), "i"(-RWSEM_ACTIVE_WRITE_BIAS), "m"(sem->count)
+		: "+m" (sem->count)
+		: "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS)
 		: "memory", "cc", "edx");
 }
 
@@ -256,8 +256,8 @@ LOCK_PREFIX	"  addl      %2,(%%eax)\n\t" /* transitions 0xZZZZ0001 -> 0xYYYY0001
 		"  jmp       1b\n"
 		LOCK_SECTION_END
 		"# ending __downgrade_write\n"
-		: "=m"(sem->count)
-		: "a"(sem), "i"(-RWSEM_WAITING_BIAS), "m"(sem->count)
+		: "+m" (sem->count)
+		: "a" (sem), "i" (-RWSEM_WAITING_BIAS)
 		: "memory", "cc");
 }
 
@@ -268,8 +268,8 @@ static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
 {
 	__asm__ __volatile__(
 LOCK_PREFIX	"addl %1,%0"
-		: "=m"(sem->count)
-		: "ir"(delta), "m"(sem->count));
+		: "+m" (sem->count)
+		: "ir" (delta));
 }
 
 /*
@@ -280,10 +280,9 @@ static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
 	int tmp = delta;
 
 	__asm__ __volatile__(
-LOCK_PREFIX	"xadd %0,(%2)"
-		: "+r"(tmp), "=m"(sem->count)
-		: "r"(sem), "m"(sem->count)
-		: "memory");
+LOCK_PREFIX	"xadd %0,%1"
+		: "+r" (tmp), "+m" (sem->count)
+		: : "memory");
 
 	return tmp+delta;
 }

include/asm-i386/semaphore.h

@@ -107,7 +107,7 @@ static inline void down(struct semaphore * sem)
 		"call __down_failed\n\t"
 		"jmp 1b\n"
 		LOCK_SECTION_END
-		:"=m" (sem->count)
+		:"+m" (sem->count)
 		:
 		:"memory","ax");
 }
@@ -132,7 +132,7 @@ static inline int down_interruptible(struct semaphore * sem)
 		"call __down_failed_interruptible\n\t"
 		"jmp 1b\n"
 		LOCK_SECTION_END
-		:"=a" (result), "=m" (sem->count)
+		:"=a" (result), "+m" (sem->count)
 		:
 		:"memory");
 	return result;
@@ -157,7 +157,7 @@ static inline int down_trylock(struct semaphore * sem)
 		"call __down_failed_trylock\n\t"
 		"jmp 1b\n"
 		LOCK_SECTION_END
-		:"=a" (result), "=m" (sem->count)
+		:"=a" (result), "+m" (sem->count)
 		:
 		:"memory");
 	return result;
@@ -182,7 +182,7 @@ static inline void up(struct semaphore * sem)
 		"jmp 1b\n"
 		LOCK_SECTION_END
 		".subsection 0\n"
-		:"=m" (sem->count)
+		:"+m" (sem->count)
 		:
 		:"memory","ax");
 }

include/asm-i386/spinlock.h

@@ -65,7 +65,7 @@ static inline void __raw_spin_lock(raw_spinlock_t *lock)
 	alternative_smp(
 		__raw_spin_lock_string,
 		__raw_spin_lock_string_up,
-		"=m" (lock->slock) : : "memory");
+		"+m" (lock->slock) : : "memory");
 }
 
 /*
@@ -79,7 +79,7 @@ static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long fla
 	alternative_smp(
 		__raw_spin_lock_string_flags,
 		__raw_spin_lock_string_up,
-		"=m" (lock->slock) : "r" (flags) : "memory");
+		"+m" (lock->slock) : "r" (flags) : "memory");
 }
 #endif
 
@@ -88,7 +88,7 @@ static inline int __raw_spin_trylock(raw_spinlock_t *lock)
 	char oldval;
 	__asm__ __volatile__(
 		"xchgb %b0,%1"
-		:"=q" (oldval), "=m" (lock->slock)
+		:"=q" (oldval), "+m" (lock->slock)
 		:"0" (0) : "memory");
 	return oldval > 0;
 }
@@ -104,7 +104,7 @@ static inline int __raw_spin_trylock(raw_spinlock_t *lock)
 
 #define __raw_spin_unlock_string \
 	"movb $1,%0" \
-		:"=m" (lock->slock) : : "memory"
+		:"+m" (lock->slock) : : "memory"
 
 
 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
@@ -118,7 +118,7 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 
 #define __raw_spin_unlock_string \
 	"xchgb %b0, %1" \
-		:"=q" (oldval), "=m" (lock->slock) \
+		:"=q" (oldval), "+m" (lock->slock) \
 		:"0" (oldval) : "memory"
 
 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
@@ -199,13 +199,13 @@ static inline int __raw_write_trylock(raw_rwlock_t *lock)
 
 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 {
-	asm volatile(LOCK_PREFIX "incl %0" :"=m" (rw->lock) : : "memory");
+	asm volatile(LOCK_PREFIX "incl %0" :"+m" (rw->lock) : : "memory");
 }
 
 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 {
 	asm volatile(LOCK_PREFIX "addl $" RW_LOCK_BIAS_STR ", %0"
-				 : "=m" (rw->lock) : : "memory");
+				 : "+m" (rw->lock) : : "memory");
 }
 
 #endif /* __ASM_SPINLOCK_H */