The Tor Browser: security/sandbox/chromium/base/atomicops_internals_x86

security/sandbox/chromium/base/atomicops_internals_x86_gcc.h@b8a032363ba2 (annotated)

security/sandbox/chromium/base/atomicops_internals_x86_gcc.h

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 // This file is an internal atomic implementation, use base/atomicops.h instead.
 #ifndef BASE_ATOMICOPS_INTERNALS_X86_GCC_H_
 #define BASE_ATOMICOPS_INTERNALS_X86_GCC_H_
 #include "base/base_export.h"
 // This struct is not part of the public API of this module; clients may not
 // use it.  (However, it's exported via BASE_EXPORT because clients implicitly
 // do use it at link time by inlining these functions.)
 // Features of this x86.  Values may not be correct before main() is run,
 // but are set conservatively.
 struct AtomicOps_x86CPUFeatureStruct {
   bool has_amd_lock_mb_bug; // Processor has AMD memory-barrier bug; do lfence
                             // after acquire compare-and-swap.
   bool has_sse2;            // Processor has SSE2.
 };
 BASE_EXPORT extern struct AtomicOps_x86CPUFeatureStruct
     AtomicOps_Internalx86CPUFeatures;
 #define ATOMICOPS_COMPILER_BARRIER() __asm__ __volatile__("" : : : "memory")
 namespace base {
 namespace subtle {
 // 32-bit low-level operations on any platform.
 inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
                                          Atomic32 old_value,
                                          Atomic32 new_value) {
   Atomic32 prev;
   __asm__ __volatile__("lock; cmpxchgl %1,%2"
                        : "=a" (prev)
                        : "q" (new_value), "m" (*ptr), "0" (old_value)
                        : "memory");
   return prev;
 }
 inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
                                          Atomic32 new_value) {
   __asm__ __volatile__("xchgl %1,%0"  // The lock prefix is implicit for xchg.
                        : "=r" (new_value)
                        : "m" (*ptr), "0" (new_value)
                        : "memory");
   return new_value;  // Now it's the previous value.
 }
 inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
                                           Atomic32 increment) {
   Atomic32 temp = increment;
   __asm__ __volatile__("lock; xaddl %0,%1"
                        : "+r" (temp), "+m" (*ptr)
                        : : "memory");
   // temp now holds the old value of *ptr
   return temp + increment;
 }
 inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
                                         Atomic32 increment) {
   Atomic32 temp = increment;
   __asm__ __volatile__("lock; xaddl %0,%1"
                        : "+r" (temp), "+m" (*ptr)
                        : : "memory");
   // temp now holds the old value of *ptr
   if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
     __asm__ __volatile__("lfence" : : : "memory");
   }
   return temp + increment;
 }
 inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
                                        Atomic32 old_value,
                                        Atomic32 new_value) {
   Atomic32 x = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
   if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
     __asm__ __volatile__("lfence" : : : "memory");
   }
   return x;
 }
 inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
                                        Atomic32 old_value,
                                        Atomic32 new_value) {
   return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
 }
 inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
   *ptr = value;
 }
 #if defined(__x86_64__)
 // 64-bit implementations of memory barrier can be simpler, because it
 // "mfence" is guaranteed to exist.
 inline void MemoryBarrier() {
   __asm__ __volatile__("mfence" : : : "memory");
 }
 inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
   *ptr = value;
   MemoryBarrier();
 }
 #else
 inline void MemoryBarrier() {
   if (AtomicOps_Internalx86CPUFeatures.has_sse2) {
     __asm__ __volatile__("mfence" : : : "memory");
   } else { // mfence is faster but not present on PIII
     Atomic32 x = 0;
     NoBarrier_AtomicExchange(&x, 0);  // acts as a barrier on PIII
   }
 }
 inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
   if (AtomicOps_Internalx86CPUFeatures.has_sse2) {
     *ptr = value;
     __asm__ __volatile__("mfence" : : : "memory");
   } else {
     NoBarrier_AtomicExchange(ptr, value);
                           // acts as a barrier on PIII
   }
 }
 #endif
 inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
   ATOMICOPS_COMPILER_BARRIER();
   *ptr = value; // An x86 store acts as a release barrier.
   // See comments in Atomic64 version of Release_Store(), below.
 }
 inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
   return *ptr;
 }
 inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
   Atomic32 value = *ptr; // An x86 load acts as a acquire barrier.
   // See comments in Atomic64 version of Release_Store(), below.
   ATOMICOPS_COMPILER_BARRIER();
   return value;
 }
 inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
   MemoryBarrier();
   return *ptr;
 }
 #if defined(__x86_64__)
 // 64-bit low-level operations on 64-bit platform.
 inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
                                          Atomic64 old_value,
                                          Atomic64 new_value) {
   Atomic64 prev;
   __asm__ __volatile__("lock; cmpxchgq %1,%2"
                        : "=a" (prev)
                        : "q" (new_value), "m" (*ptr), "0" (old_value)
                        : "memory");
   return prev;
 }
 inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
                                          Atomic64 new_value) {
   __asm__ __volatile__("xchgq %1,%0"  // The lock prefix is implicit for xchg.
                        : "=r" (new_value)
                        : "m" (*ptr), "0" (new_value)
                        : "memory");
   return new_value;  // Now it's the previous value.
 }
 inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
                                           Atomic64 increment) {
   Atomic64 temp = increment;
   __asm__ __volatile__("lock; xaddq %0,%1"
                        : "+r" (temp), "+m" (*ptr)
                        : : "memory");
   // temp now contains the previous value of *ptr
   return temp + increment;
 }
 inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
                                         Atomic64 increment) {
   Atomic64 temp = increment;
   __asm__ __volatile__("lock; xaddq %0,%1"
                        : "+r" (temp), "+m" (*ptr)
                        : : "memory");
   // temp now contains the previous value of *ptr
   if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
     __asm__ __volatile__("lfence" : : : "memory");
   }
   return temp + increment;
 }
 inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
   *ptr = value;
 }
 inline void Acquire_Store(volatile Atomic64* ptr, Atomic64 value) {
   *ptr = value;
   MemoryBarrier();
 }
 inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
   ATOMICOPS_COMPILER_BARRIER();
   *ptr = value; // An x86 store acts as a release barrier
                 // for current AMD/Intel chips as of Jan 2008.
                 // See also Acquire_Load(), below.
   // When new chips come out, check:
   //  IA-32 Intel Architecture Software Developer's Manual, Volume 3:
   //  System Programming Guide, Chatper 7: Multiple-processor management,
   //  Section 7.2, Memory Ordering.
   // Last seen at:
   //   http://developer.intel.com/design/pentium4/manuals/index_new.htm
   //
   // x86 stores/loads fail to act as barriers for a few instructions (clflush
   // maskmovdqu maskmovq movntdq movnti movntpd movntps movntq) but these are
   // not generated by the compiler, and are rare.  Users of these instructions
   // need to know about cache behaviour in any case since all of these involve
   // either flushing cache lines or non-temporal cache hints.
 }
 inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
   return *ptr;
 }
 inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
   Atomic64 value = *ptr; // An x86 load acts as a acquire barrier,
                          // for current AMD/Intel chips as of Jan 2008.
                          // See also Release_Store(), above.
   ATOMICOPS_COMPILER_BARRIER();
   return value;
 }
 inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
   MemoryBarrier();
   return *ptr;
 }
 inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
                                        Atomic64 old_value,
                                        Atomic64 new_value) {
   Atomic64 x = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
   if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
     __asm__ __volatile__("lfence" : : : "memory");
   }
   return x;
 }
 inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
                                        Atomic64 old_value,
                                        Atomic64 new_value) {
   return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
 }
 #endif  // defined(__x86_64__)
 } // namespace base::subtle
 } // namespace base
 #undef ATOMICOPS_COMPILER_BARRIER
 #endif  // BASE_ATOMICOPS_INTERNALS_X86_GCC_H_

The Tor Browser / annotate

security/sandbox/chromium/base/atomicops_internals_x86_gcc.h@b8a032363ba2 (annotated)

security/sandbox/chromium/base/atomicops_internals_x86_gcc.h