From 2d0c3a0ab8cb33ff01afc784f0660e3a7c71586a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 27 Jul 2010 17:01:49 -0700 Subject: [PATCH] x86: Add memory modify constraints to xchg() and cmpxchg() commit 113fc5a6e8c2288619ff7e8187a6f556b7e0d372 upstream. xchg() and cmpxchg() modify their memory operands, not merely read them. For some versions of gcc the "memory" clobber has apparently dealt with the situation, but not for all. Originally-by: Linus Torvalds Signed-off-by: H. Peter Anvin Cc: Glauber Costa Cc: Avi Kivity Cc: Peter Palfrader Cc: Greg KH Cc: Alan Cox Cc: Zachary Amsden Cc: Marcelo Tosatti LKML-Reference: <4C4F7277.8050306@zytor.com> Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/cmpxchg_32.h | 68 +++++++++++++++---------------- arch/x86/include/asm/cmpxchg_64.h | 40 +++++++++--------- 2 files changed, 54 insertions(+), 54 deletions(-) diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h index ffb9bb6b6c37..a6d360e147ff 100644 --- a/arch/x86/include/asm/cmpxchg_32.h +++ b/arch/x86/include/asm/cmpxchg_32.h @@ -27,20 +27,20 @@ struct __xchg_dummy { switch (size) { \ case 1: \ asm volatile("xchgb %b0,%1" \ - : "=q" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=q" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ case 2: \ asm volatile("xchgw %w0,%1" \ - : "=r" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=r" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ case 4: \ asm volatile("xchgl %0,%1" \ - : "=r" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=r" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ default: \ @@ -70,14 +70,14 @@ static inline void __set_64bit(unsigned long long *ptr, unsigned int low, unsigned int high) { asm volatile("\n1:\t" - "movl (%0), %%eax\n\t" - "movl 4(%0), %%edx\n\t" - LOCK_PREFIX "cmpxchg8b (%0)\n\t" + "movl (%1), %%eax\n\t" + "movl 4(%1), %%edx\n\t" + LOCK_PREFIX "cmpxchg8b (%1)\n\t" "jnz 1b" - : /* no outputs */ - : "D"(ptr), - "b"(low), - "c"(high) + : "=m" (*ptr) + : "D" (ptr), + "b" (low), + "c" (high) : "ax", "dx", "memory"); } @@ -121,21 +121,21 @@ extern void __cmpxchg_wrong_size(void); __typeof__(*(ptr)) __new = (new); \ switch (size) { \ case 1: \ - asm volatile(lock "cmpxchgb %b1,%2" \ - : "=a"(__ret) \ - : "q"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgb %b2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "q" (__new), "0" (__old) \ : "memory"); \ break; \ case 2: \ - asm volatile(lock "cmpxchgw %w1,%2" \ - : "=a"(__ret) \ - : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgw %w2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "r" (__new), "0" (__old) \ : "memory"); \ break; \ case 4: \ - asm volatile(lock "cmpxchgl %1,%2" \ - : "=a"(__ret) \ - : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgl %2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "r" (__new), "0" (__old) \ : "memory"); \ break; \ default: \ @@ -180,12 +180,12 @@ static inline unsigned long long __cmpxchg64(volatile void *ptr, unsigned long long new) { unsigned long long prev; - asm volatile(LOCK_PREFIX "cmpxchg8b %3" - : "=A"(prev) - : "b"((unsigned long)new), - "c"((unsigned long)(new >> 32)), - "m"(*__xg(ptr)), - "0"(old) + asm volatile(LOCK_PREFIX "cmpxchg8b %1" + : "=A" (prev), + "+m" (*__xg(ptr)) + : "b" ((unsigned long)new), + "c" ((unsigned long)(new >> 32)), + "0" (old) : "memory"); return prev; } @@ -195,12 +195,12 @@ static inline unsigned long long __cmpxchg64_local(volatile void *ptr, unsigned long long new) { unsigned long long prev; - asm volatile("cmpxchg8b %3" - : "=A"(prev) - : "b"((unsigned long)new), - "c"((unsigned long)(new >> 32)), - "m"(*__xg(ptr)), - "0"(old) + asm volatile("cmpxchg8b %1" + : "=A" (prev), + "+m" (*__xg(ptr)) + : "b" ((unsigned long)new), + "c" ((unsigned long)(new >> 32)), + "0" (old) : "memory"); return prev; } diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h index 485ae415faec..b92f147339f3 100644 --- a/arch/x86/include/asm/cmpxchg_64.h +++ b/arch/x86/include/asm/cmpxchg_64.h @@ -26,26 +26,26 @@ extern void __cmpxchg_wrong_size(void); switch (size) { \ case 1: \ asm volatile("xchgb %b0,%1" \ - : "=q" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=q" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ case 2: \ asm volatile("xchgw %w0,%1" \ - : "=r" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=r" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ case 4: \ asm volatile("xchgl %k0,%1" \ - : "=r" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=r" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ case 8: \ asm volatile("xchgq %0,%1" \ - : "=r" (__x) \ - : "m" (*__xg(ptr)), "0" (__x) \ + : "=r" (__x), "+m" (*__xg(ptr)) \ + : "0" (__x) \ : "memory"); \ break; \ default: \ @@ -71,27 +71,27 @@ extern void __cmpxchg_wrong_size(void); __typeof__(*(ptr)) __new = (new); \ switch (size) { \ case 1: \ - asm volatile(lock "cmpxchgb %b1,%2" \ - : "=a"(__ret) \ - : "q"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgb %b2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "q" (__new), "0" (__old) \ : "memory"); \ break; \ case 2: \ - asm volatile(lock "cmpxchgw %w1,%2" \ - : "=a"(__ret) \ - : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgw %w2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "r" (__new), "0" (__old) \ : "memory"); \ break; \ case 4: \ - asm volatile(lock "cmpxchgl %k1,%2" \ - : "=a"(__ret) \ - : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgl %k2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "r" (__new), "0" (__old) \ : "memory"); \ break; \ case 8: \ - asm volatile(lock "cmpxchgq %1,%2" \ - : "=a"(__ret) \ - : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \ + asm volatile(lock "cmpxchgq %2,%1" \ + : "=a" (__ret), "+m" (*__xg(ptr)) \ + : "r" (__new), "0" (__old) \ : "memory"); \ break; \ default: \ -- 2.39.5