1 /* Copyright (c) 2007, Google Inc. 2 * All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions are 6 * met: 7 * 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above 11 * copyright notice, this list of conditions and the following disclaimer 12 * in the documentation and/or other materials provided with the 13 * distribution. 14 * * Neither the name of Google Inc. nor the names of its 15 * contributors may be used to endorse or promote products derived from 16 * this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 * 30 * --- 31 * This module gets enough CPU information to optimize the 32 * atomicops module on x86. 33 */ 34 35 #include "base/atomicops.h" 36 #include "base/basictypes.h" 37 #include "base/googleinit.h" 38 #include "base/logging.h" 39 #include <string.h> 40 41 // This file only makes sense with atomicops-internals-x86.h -- it 42 // depends on structs that are defined in that file. If atomicops.h 43 // doesn't sub-include that file, then we aren't needed, and shouldn't 44 // try to do anything. 45 #ifdef BASE_ATOMICOPS_INTERNALS_X86_H_ 46 47 // Inline cpuid instruction. In PIC compilations, %ebx contains the address 48 // of the global offset table. To avoid breaking such executables, this code 49 // must preserve that register's value across cpuid instructions. 50 #if defined(__i386__) 51 #define cpuid(a, b, c, d, inp) \ 52 asm ("mov %%ebx, %%edi\n" \ 53 "cpuid\n" \ 54 "xchg %%edi, %%ebx\n" \ 55 : "=a" (a), "=D" (b), "=c" (c), "=d" (d) : "a" (inp)) 56 #elif defined (__x86_64__) 57 #define cpuid(a, b, c, d, inp) \ 58 asm ("mov %%rbx, %%rdi\n" \ 59 "cpuid\n" \ 60 "xchg %%rdi, %%rbx\n" \ 61 : "=a" (a), "=D" (b), "=c" (c), "=d" (d) : "a" (inp)) 62 #endif 63 64 #if defined(cpuid) // initialize the struct only on x86 65 66 // Set the flags so that code will run correctly and conservatively 67 // until InitGoogle() is called. 68 struct AtomicOps_x86CPUFeatureStruct AtomicOps_Internalx86CPUFeatures = { 69 false, // bug can't exist before process spawns multiple threads 70 false, // no SSE2 71 false, // no cmpxchg16b 72 }; 73 74 // Initialize the AtomicOps_Internalx86CPUFeatures struct. 75 static void AtomicOps_Internalx86CPUFeaturesInit() { 76 uint32 eax; 77 uint32 ebx; 78 uint32 ecx; 79 uint32 edx; 80 81 // Get vendor string (issue CPUID with eax = 0) 82 cpuid(eax, ebx, ecx, edx, 0); 83 char vendor[13]; 84 memcpy(vendor, &ebx, 4); 85 memcpy(vendor + 4, &edx, 4); 86 memcpy(vendor + 8, &ecx, 4); 87 vendor[12] = 0; 88 89 // get feature flags in ecx/edx, and family/model in eax 90 cpuid(eax, ebx, ecx, edx, 1); 91 92 int family = (eax >> 8) & 0xf; // family and model fields 93 int model = (eax >> 4) & 0xf; 94 if (family == 0xf) { // use extended family and model fields 95 family += (eax >> 20) & 0xff; 96 model += ((eax >> 16) & 0xf) << 4; 97 } 98 99 // Opteron Rev E has a bug in which on very rare occasions a locked 100 // instruction doesn't act as a read-acquire barrier if followed by a 101 // non-locked read-modify-write instruction. Rev F has this bug in 102 // pre-release versions, but not in versions released to customers, 103 // so we test only for Rev E, which is family 15, model 32..63 inclusive. 104 if (strcmp(vendor, "AuthenticAMD") == 0 && // AMD 105 family == 15 && 106 32 <= model && model <= 63) { 107 AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = true; 108 } else { 109 AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = false; 110 } 111 112 // edx bit 26 is SSE2 which we use to tell use whether we can use mfence 113 AtomicOps_Internalx86CPUFeatures.has_sse2 = ((edx >> 26) & 1); 114 115 // ecx bit 13 indicates whether the cmpxchg16b instruction is supported 116 AtomicOps_Internalx86CPUFeatures.has_cmpxchg16b = ((ecx >> 13) & 1); 117 } 118 119 REGISTER_MODULE_INITIALIZER(atomicops_x86, { 120 AtomicOps_Internalx86CPUFeaturesInit(); 121 }); 122 123 #endif 124 125 #endif /* ifdef BASE_ATOMICOPS_INTERNALS_X86_H_ */ 126