1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/cpu.h"
6
7 #include <limits.h>
8 #include <stddef.h>
9 #include <stdint.h>
10 #include <string.h>
11
12 #include <algorithm>
13 #include <utility>
14
15 #include "base/macros.h"
16 #include "build/build_config.h"
17
18 #if defined(ARCH_CPU_ARM_FAMILY) && (defined(OS_ANDROID) || defined(OS_LINUX))
19 #include "base/files/file_util.h"
20 #endif
21
22 #if defined(ARCH_CPU_X86_FAMILY)
23 #if defined(COMPILER_MSVC)
24 #include <intrin.h>
25 #include <immintrin.h> // For _xgetbv()
26 #endif
27 #endif
28
29 namespace base {
30
CPU()31 CPU::CPU()
32 : signature_(0),
33 type_(0),
34 family_(0),
35 model_(0),
36 stepping_(0),
37 ext_model_(0),
38 ext_family_(0),
39 has_mmx_(false),
40 has_sse_(false),
41 has_sse2_(false),
42 has_sse3_(false),
43 has_ssse3_(false),
44 has_sse41_(false),
45 has_sse42_(false),
46 has_popcnt_(false),
47 has_avx_(false),
48 has_avx2_(false),
49 has_aesni_(false),
50 has_non_stop_time_stamp_counter_(false),
51 cpu_vendor_("unknown") {
52 Initialize();
53 }
54
55 namespace {
56
57 #if defined(ARCH_CPU_X86_FAMILY)
58 #if !defined(COMPILER_MSVC)
59
60 #if defined(__pic__) && defined(__i386__)
61
__cpuid(int cpu_info[4],int info_type)62 void __cpuid(int cpu_info[4], int info_type) {
63 __asm__ volatile(
64 "mov %%ebx, %%edi\n"
65 "cpuid\n"
66 "xchg %%edi, %%ebx\n"
67 : "=a"(cpu_info[0]), "=D"(cpu_info[1]), "=c"(cpu_info[2]),
68 "=d"(cpu_info[3])
69 : "a"(info_type), "c"(0));
70 }
71
72 #else
73
74 void __cpuid(int cpu_info[4], int info_type) {
75 __asm__ volatile("cpuid\n"
76 : "=a"(cpu_info[0]), "=b"(cpu_info[1]), "=c"(cpu_info[2]),
77 "=d"(cpu_info[3])
78 : "a"(info_type), "c"(0));
79 }
80
81 #endif
82
83 // _xgetbv returns the value of an Intel Extended Control Register (XCR).
84 // Currently only XCR0 is defined by Intel so |xcr| should always be zero.
_xgetbv(uint32_t xcr)85 uint64_t _xgetbv(uint32_t xcr) {
86 uint32_t eax, edx;
87
88 __asm__ volatile (
89 "xgetbv" : "=a"(eax), "=d"(edx) : "c"(xcr));
90 return (static_cast<uint64_t>(edx) << 32) | eax;
91 }
92
93 #endif // !defined(COMPILER_MSVC)
94 #endif // ARCH_CPU_X86_FAMILY
95
96 #if defined(ARCH_CPU_ARM_FAMILY) && (defined(OS_ANDROID) || defined(OS_LINUX))
CpuInfoBrand()97 std::string* CpuInfoBrand() {
98 static std::string* brand = []() {
99 // This function finds the value from /proc/cpuinfo under the key "model
100 // name" or "Processor". "model name" is used in Linux 3.8 and later (3.7
101 // and later for arm64) and is shown once per CPU. "Processor" is used in
102 // earler versions and is shown only once at the top of /proc/cpuinfo
103 // regardless of the number CPUs.
104 const char kModelNamePrefix[] = "model name\t: ";
105 const char kProcessorPrefix[] = "Processor\t: ";
106
107 std::string contents;
108 ReadFileToString(FilePath("/proc/cpuinfo"), &contents);
109 DCHECK(!contents.empty());
110
111 std::istringstream iss(contents);
112 std::string line;
113 while (std::getline(iss, line)) {
114 if (line.compare(0, strlen(kModelNamePrefix), kModelNamePrefix) == 0)
115 return new std::string(line.substr(strlen(kModelNamePrefix)));
116 if (line.compare(0, strlen(kProcessorPrefix), kProcessorPrefix) == 0)
117 return new std::string(line.substr(strlen(kProcessorPrefix)));
118 }
119
120 return new std::string();
121 }();
122
123 return brand;
124 }
125 #endif // defined(ARCH_CPU_ARM_FAMILY) && (defined(OS_ANDROID) ||
126 // defined(OS_LINUX))
127
128 } // namespace
129
Initialize()130 void CPU::Initialize() {
131 #if defined(ARCH_CPU_X86_FAMILY)
132 int cpu_info[4] = {-1};
133 // This array is used to temporarily hold the vendor name and then the brand
134 // name. Thus it has to be big enough for both use cases. There are
135 // static_asserts below for each of the use cases to make sure this array is
136 // big enough.
137 char cpu_string[sizeof(cpu_info) * 3 + 1];
138
139 // __cpuid with an InfoType argument of 0 returns the number of
140 // valid Ids in CPUInfo[0] and the CPU identification string in
141 // the other three array elements. The CPU identification string is
142 // not in linear order. The code below arranges the information
143 // in a human readable form. The human readable order is CPUInfo[1] |
144 // CPUInfo[3] | CPUInfo[2]. CPUInfo[2] and CPUInfo[3] are swapped
145 // before using memcpy() to copy these three array elements to |cpu_string|.
146 __cpuid(cpu_info, 0);
147 int num_ids = cpu_info[0];
148 std::swap(cpu_info[2], cpu_info[3]);
149 static constexpr size_t kVendorNameSize = 3 * sizeof(cpu_info[1]);
150 static_assert(kVendorNameSize < arraysize(cpu_string),
151 "cpu_string too small");
152 memcpy(cpu_string, &cpu_info[1], kVendorNameSize);
153 cpu_string[kVendorNameSize] = '\0';
154 cpu_vendor_ = cpu_string;
155
156 // Interpret CPU feature information.
157 if (num_ids > 0) {
158 int cpu_info7[4] = {0};
159 __cpuid(cpu_info, 1);
160 if (num_ids >= 7) {
161 __cpuid(cpu_info7, 7);
162 }
163 signature_ = cpu_info[0];
164 stepping_ = cpu_info[0] & 0xf;
165 model_ = ((cpu_info[0] >> 4) & 0xf) + ((cpu_info[0] >> 12) & 0xf0);
166 family_ = (cpu_info[0] >> 8) & 0xf;
167 type_ = (cpu_info[0] >> 12) & 0x3;
168 ext_model_ = (cpu_info[0] >> 16) & 0xf;
169 ext_family_ = (cpu_info[0] >> 20) & 0xff;
170 has_mmx_ = (cpu_info[3] & 0x00800000) != 0;
171 has_sse_ = (cpu_info[3] & 0x02000000) != 0;
172 has_sse2_ = (cpu_info[3] & 0x04000000) != 0;
173 has_sse3_ = (cpu_info[2] & 0x00000001) != 0;
174 has_ssse3_ = (cpu_info[2] & 0x00000200) != 0;
175 has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
176 has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
177 has_popcnt_ = (cpu_info[2] & 0x00800000) != 0;
178
179 // AVX instructions will generate an illegal instruction exception unless
180 // a) they are supported by the CPU,
181 // b) XSAVE is supported by the CPU and
182 // c) XSAVE is enabled by the kernel.
183 // See http://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled
184 //
185 // In addition, we have observed some crashes with the xgetbv instruction
186 // even after following Intel's example code. (See crbug.com/375968.)
187 // Because of that, we also test the XSAVE bit because its description in
188 // the CPUID documentation suggests that it signals xgetbv support.
189 has_avx_ =
190 (cpu_info[2] & 0x10000000) != 0 &&
191 (cpu_info[2] & 0x04000000) != 0 /* XSAVE */ &&
192 (cpu_info[2] & 0x08000000) != 0 /* OSXSAVE */ &&
193 (_xgetbv(0) & 6) == 6 /* XSAVE enabled by kernel */;
194 has_aesni_ = (cpu_info[2] & 0x02000000) != 0;
195 has_avx2_ = has_avx_ && (cpu_info7[1] & 0x00000020) != 0;
196 }
197
198 // Get the brand string of the cpu.
199 __cpuid(cpu_info, 0x80000000);
200 const int max_parameter = cpu_info[0];
201
202 static constexpr int kParameterStart = 0x80000002;
203 static constexpr int kParameterEnd = 0x80000004;
204 static constexpr int kParameterSize = kParameterEnd - kParameterStart + 1;
205 static_assert(kParameterSize * sizeof(cpu_info) + 1 == arraysize(cpu_string),
206 "cpu_string has wrong size");
207
208 if (max_parameter >= kParameterEnd) {
209 size_t i = 0;
210 for (int parameter = kParameterStart; parameter <= kParameterEnd;
211 ++parameter) {
212 __cpuid(cpu_info, parameter);
213 memcpy(&cpu_string[i], cpu_info, sizeof(cpu_info));
214 i += sizeof(cpu_info);
215 }
216 cpu_string[i] = '\0';
217 cpu_brand_ = cpu_string;
218 }
219
220 static constexpr int kParameterContainingNonStopTimeStampCounter = 0x80000007;
221 if (max_parameter >= kParameterContainingNonStopTimeStampCounter) {
222 __cpuid(cpu_info, kParameterContainingNonStopTimeStampCounter);
223 has_non_stop_time_stamp_counter_ = (cpu_info[3] & (1 << 8)) != 0;
224 }
225 #elif defined(ARCH_CPU_ARM_FAMILY) && (defined(OS_ANDROID) || defined(OS_LINUX))
226 cpu_brand_ = *CpuInfoBrand();
227 #endif
228 }
229
GetIntelMicroArchitecture() const230 CPU::IntelMicroArchitecture CPU::GetIntelMicroArchitecture() const {
231 if (has_avx2()) return AVX2;
232 if (has_avx()) return AVX;
233 if (has_sse42()) return SSE42;
234 if (has_sse41()) return SSE41;
235 if (has_ssse3()) return SSSE3;
236 if (has_sse3()) return SSE3;
237 if (has_sse2()) return SSE2;
238 if (has_sse()) return SSE;
239 return PENTIUM;
240 }
241
242 } // namespace base
243