base/cpu.cc

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/cpu.h"

#include <inttypes.h>
#include <limits.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

#include <algorithm>
#include <sstream>
#include <utility>

#include "base/no_destructor.h"
#include "build/build_config.h"

#if defined(ARCH_CPU_ARM_FAMILY) && \
    (BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS))
#include <asm/hwcap.h>
#include <sys/auxv.h>

#include "base/files/file_util.h"
#include "base/numerics/checked_math.h"
#include "base/ranges/algorithm.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"

// Temporary definitions until a new hwcap.h is pulled in everywhere.
// https://crbug.com/1265965
#ifndef HWCAP2_MTE
#define HWCAP2_MTE (1 << 18)
#define HWCAP2_BTI (1 << 17)
#endif

struct ProcCpuInfo {
  std::string brand;
  uint8_t implementer = 0;
  uint32_t part_number = 0;
};
#endif

#if defined(ARCH_CPU_X86_FAMILY)
#if defined(COMPILER_MSVC)
#include <intrin.h>
#include <immintrin.h>  // For _xgetbv()
#endif
#endif

namespace base {

#if defined(ARCH_CPU_X86_FAMILY)
namespace internal {

X86ModelInfo ComputeX86FamilyAndModel(const std::string& vendor,
                                      int signature) {
  X86ModelInfo results;
  results.family = (signature >> 8) & 0xf;
  results.model = (signature >> 4) & 0xf;
  results.ext_family = 0;
  results.ext_model = 0;

  // The "Intel 64 and IA-32 Architectures Developer's Manual: Vol. 2A"
  // specifies the Extended Model is defined only when the Base Family is
  // 06h or 0Fh.
  // The "AMD CPUID Specification" specifies that the Extended Model is
  // defined only when Base Family is 0Fh.
  // Both manuals define the display model as
  // {ExtendedModel[3:0],BaseModel[3:0]} in that case.
  if (results.family == 0xf ||
      (results.family == 0x6 && vendor == "GenuineIntel")) {
    results.ext_model = (signature >> 16) & 0xf;
    results.model += results.ext_model << 4;
  }
  // Both the "Intel 64 and IA-32 Architectures Developer's Manual: Vol. 2A"
  // and the "AMD CPUID Specification" specify that the Extended Family is
  // defined only when the Base Family is 0Fh.
  // Both manuals define the display family as {0000b,BaseFamily[3:0]} +
  // ExtendedFamily[7:0] in that case.
  if (results.family == 0xf) {
    results.ext_family = (signature >> 20) & 0xff;
    results.family += results.ext_family;
  }

  return results;
}

}  // namespace internal
#endif  // defined(ARCH_CPU_X86_FAMILY)

CPU::CPU(bool require_branding) {
  Initialize(require_branding);
}
CPU::CPU() : CPU(true) {}
CPU::CPU(CPU&&) = default;

namespace {

#if defined(ARCH_CPU_X86_FAMILY)
#if !defined(COMPILER_MSVC)

#if defined(__pic__) && defined(__i386__)

void __cpuid(int cpu_info[4], int info_type) {
  __asm__ volatile(
      "mov %%ebx, %%edi\n"
      "cpuid\n"
      "xchg %%edi, %%ebx\n"
      : "=a"(cpu_info[0]), "=D"(cpu_info[1]), "=c"(cpu_info[2]),
        "=d"(cpu_info[3])
      : "a"(info_type), "c"(0));
}

#else

void __cpuid(int cpu_info[4], int info_type) {
  __asm__ volatile("cpuid\n"
                   : "=a"(cpu_info[0]), "=b"(cpu_info[1]), "=c"(cpu_info[2]),
                     "=d"(cpu_info[3])
                   : "a"(info_type), "c"(0));
}

#endif
#endif  // !defined(COMPILER_MSVC)

// xgetbv returns the value of an Intel Extended Control Register (XCR).
// Currently only XCR0 is defined by Intel so |xcr| should always be zero.
uint64_t xgetbv(uint32_t xcr) {
#if defined(COMPILER_MSVC)
  return _xgetbv(xcr);
#else
  uint32_t eax, edx;

  __asm__ volatile (
    "xgetbv" : "=a"(eax), "=d"(edx) : "c"(xcr));
  return (static_cast<uint64_t>(edx) << 32) | eax;
#endif  // defined(COMPILER_MSVC)
}

#endif  // ARCH_CPU_X86_FAMILY

#if defined(ARCH_CPU_ARM_FAMILY) && \
    (BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS))
StringPairs::const_iterator FindFirstProcCpuKey(const StringPairs& pairs,
                                                StringPiece key) {
  return ranges::find_if(pairs, [key](const StringPairs::value_type& pair) {
    return TrimWhitespaceASCII(pair.first, base::TRIM_ALL) == key;
  });
}

// Parses information about the ARM processor. Note that depending on the CPU
// package, processor configuration, and/or kernel version, this may only
// report information about the processor on which this thread is running. This
// can happen on heterogeneous-processor SoCs like Snapdragon 808, which has 4
// Cortex-A53 and 2 Cortex-A57. Unfortunately there is not a universally
// reliable way to examine the CPU part information for all cores.
const ProcCpuInfo& ParseProcCpu() {
  static const NoDestructor<ProcCpuInfo> info([]() {
    // This function finds the value from /proc/cpuinfo under the key "model
    // name" or "Processor". "model name" is used in Linux 3.8 and later (3.7
    // and later for arm64) and is shown once per CPU. "Processor" is used in
    // earler versions and is shown only once at the top of /proc/cpuinfo
    // regardless of the number CPUs.
    const char kModelNamePrefix[] = "model name";
    const char kProcessorPrefix[] = "Processor";

    std::string cpuinfo;
    ReadFileToString(FilePath("/proc/cpuinfo"), &cpuinfo);
    DCHECK(!cpuinfo.empty());

    ProcCpuInfo info;

    StringPairs pairs;
    if (!SplitStringIntoKeyValuePairs(cpuinfo, ':', '\n', &pairs)) {
      NOTREACHED();
      return info;
    }

    auto model_name = FindFirstProcCpuKey(pairs, kModelNamePrefix);
    if (model_name == pairs.end())
      model_name = FindFirstProcCpuKey(pairs, kProcessorPrefix);
    if (model_name != pairs.end()) {
      info.brand =
          std::string(TrimWhitespaceASCII(model_name->second, TRIM_ALL));
    }

    auto implementer_string = FindFirstProcCpuKey(pairs, "CPU implementer");
    if (implementer_string != pairs.end()) {
      // HexStringToUInt() handles the leading whitespace on the value.
      uint32_t implementer;
      HexStringToUInt(implementer_string->second, &implementer);
      if (!CheckedNumeric<uint32_t>(implementer)
               .AssignIfValid(&info.implementer)) {
        info.implementer = 0;
      }
    }

    auto part_number_string = FindFirstProcCpuKey(pairs, "CPU part");
    if (part_number_string != pairs.end())
      HexStringToUInt(part_number_string->second, &info.part_number);

    return info;
  }());

  return *info;
}
#endif  // defined(ARCH_CPU_ARM_FAMILY) && (BUILDFLAG(IS_ANDROID) ||
        // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS))

}  // namespace

void CPU::Initialize(bool require_branding) {
#if defined(ARCH_CPU_X86_FAMILY)
  int cpu_info[4] = {-1};
  // This array is used to temporarily hold the vendor name and then the brand
  // name. Thus it has to be big enough for both use cases. There are
  // static_asserts below for each of the use cases to make sure this array is
  // big enough.
  char cpu_string[sizeof(cpu_info) * 3 + 1];

  // __cpuid with an InfoType argument of 0 returns the number of
  // valid Ids in CPUInfo[0] and the CPU identification string in
  // the other three array elements. The CPU identification string is
  // not in linear order. The code below arranges the information
  // in a human readable form. The human readable order is CPUInfo[1] |
  // CPUInfo[3] | CPUInfo[2]. CPUInfo[2] and CPUInfo[3] are swapped
  // before using memcpy() to copy these three array elements to |cpu_string|.
  __cpuid(cpu_info, 0);
  int num_ids = cpu_info[0];
  std::swap(cpu_info[2], cpu_info[3]);
  static constexpr size_t kVendorNameSize = 3 * sizeof(cpu_info[1]);
  static_assert(kVendorNameSize < std::size(cpu_string),
                "cpu_string too small");
  memcpy(cpu_string, &cpu_info[1], kVendorNameSize);
  cpu_string[kVendorNameSize] = '\0';
  cpu_vendor_ = cpu_string;

  // Interpret CPU feature information.
  if (num_ids > 0) {
    int cpu_info7[4] = {0};
    __cpuid(cpu_info, 1);
    if (num_ids >= 7) {
      __cpuid(cpu_info7, 7);
    }
    signature_ = cpu_info[0];
    stepping_ = cpu_info[0] & 0xf;
    type_ = (cpu_info[0] >> 12) & 0x3;
    internal::X86ModelInfo results =
        internal::ComputeX86FamilyAndModel(cpu_vendor_, signature_);
    family_ = results.family;
    model_ = results.model;
    ext_family_ = results.ext_family;
    ext_model_ = results.ext_model;
    has_mmx_ =   (cpu_info[3] & 0x00800000) != 0;
    has_sse_ =   (cpu_info[3] & 0x02000000) != 0;
    has_sse2_ =  (cpu_info[3] & 0x04000000) != 0;
    has_sse3_ =  (cpu_info[2] & 0x00000001) != 0;
    has_ssse3_ = (cpu_info[2] & 0x00000200) != 0;
    has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
    has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
    has_popcnt_ = (cpu_info[2] & 0x00800000) != 0;

    // "Hypervisor Present Bit: Bit 31 of ECX of CPUID leaf 0x1."
    // See https://lwn.net/Articles/301888/
    // This is checking for any hypervisor. Hypervisors may choose not to
    // announce themselves. Hypervisors trap CPUID and sometimes return
    // different results to underlying hardware.
    is_running_in_vm_ = (static_cast<uint32_t>(cpu_info[2]) & 0x80000000) != 0;

    // AVX instructions will generate an illegal instruction exception unless
    //   a) they are supported by the CPU,
    //   b) XSAVE is supported by the CPU and
    //   c) XSAVE is enabled by the kernel.
    // See http://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled
    //
    // In addition, we have observed some crashes with the xgetbv instruction
    // even after following Intel's example code. (See crbug.com/375968.)
    // Because of that, we also test the XSAVE bit because its description in
    // the CPUID documentation suggests that it signals xgetbv support.
    has_avx_ =
        (cpu_info[2] & 0x10000000) != 0 &&
        (cpu_info[2] & 0x04000000) != 0 /* XSAVE */ &&
        (cpu_info[2] & 0x08000000) != 0 /* OSXSAVE */ &&
        (xgetbv(0) & 6) == 6 /* XSAVE enabled by kernel */;
    has_aesni_ = (cpu_info[2] & 0x02000000) != 0;
    has_fma3_ = (cpu_info[2] & 0x00001000) != 0;
    has_avx2_ = has_avx_ && (cpu_info7[1] & 0x00000020) != 0;

    has_pku_ = (cpu_info7[2] & 0x00000010) != 0;
  }

  // Get the brand string of the cpu.
  __cpuid(cpu_info, static_cast<int>(0x80000000));
  const uint32_t max_parameter = static_cast<uint32_t>(cpu_info[0]);

  static constexpr uint32_t kParameterStart = 0x80000002;
  static constexpr uint32_t kParameterEnd = 0x80000004;
  static constexpr uint32_t kParameterSize =
      kParameterEnd - kParameterStart + 1;
  static_assert(kParameterSize * sizeof(cpu_info) + 1 == std::size(cpu_string),
                "cpu_string has wrong size");

  if (max_parameter >= kParameterEnd) {
    size_t i = 0;
    for (uint32_t parameter = kParameterStart; parameter <= kParameterEnd;
         ++parameter) {
      __cpuid(cpu_info, static_cast<int>(parameter));
      memcpy(&cpu_string[i], cpu_info, sizeof(cpu_info));
      i += sizeof(cpu_info);
    }
    cpu_string[i] = '\0';
    cpu_brand_ = cpu_string;
  }

  static constexpr uint32_t kParameterContainingNonStopTimeStampCounter =
      0x80000007;
  if (max_parameter >= kParameterContainingNonStopTimeStampCounter) {
    __cpuid(cpu_info,
            static_cast<int>(kParameterContainingNonStopTimeStampCounter));
    has_non_stop_time_stamp_counter_ = (cpu_info[3] & (1 << 8)) != 0;
  }

  if (!has_non_stop_time_stamp_counter_ && is_running_in_vm_) {
    int cpu_info_hv[4] = {};
    __cpuid(cpu_info_hv, 0x40000000);
    if (cpu_info_hv[1] == 0x7263694D &&  // Micr
        cpu_info_hv[2] == 0x666F736F &&  // osof
        cpu_info_hv[3] == 0x76482074) {  // t Hv
      // If CPUID says we have a variant TSC and a hypervisor has identified
      // itself and the hypervisor says it is Microsoft Hyper-V, then treat
      // TSC as invariant.
      //
      // Microsoft Hyper-V hypervisor reports variant TSC as there are some
      // scenarios (eg. VM live migration) where the TSC is variant, but for
      // our purposes we can treat it as invariant.
      has_non_stop_time_stamp_counter_ = true;
    }
  }
#elif defined(ARCH_CPU_ARM_FAMILY)
#if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
  if (require_branding) {
    const ProcCpuInfo& info = ParseProcCpu();
    cpu_brand_ = info.brand;
    implementer_ = info.implementer;
    part_number_ = info.part_number;
  }

#if defined(ARCH_CPU_ARM64)
  // Check for Armv8.5-A BTI/MTE support, exposed via HWCAP2
  unsigned long hwcap2 = getauxval(AT_HWCAP2);
  has_mte_ = hwcap2 & HWCAP2_MTE;
  has_bti_ = hwcap2 & HWCAP2_BTI;
#endif

#elif BUILDFLAG(IS_WIN)
  // Windows makes high-resolution thread timing information available in
  // user-space.
  has_non_stop_time_stamp_counter_ = true;
#endif
#endif
}

#if defined(ARCH_CPU_X86_FAMILY)
CPU::IntelMicroArchitecture CPU::GetIntelMicroArchitecture() const {
  if (has_avx2()) return AVX2;
  if (has_fma3()) return FMA3;
  if (has_avx()) return AVX;
  if (has_sse42()) return SSE42;
  if (has_sse41()) return SSE41;
  if (has_ssse3()) return SSSE3;
  if (has_sse3()) return SSE3;
  if (has_sse2()) return SSE2;
  if (has_sse()) return SSE;
  return PENTIUM;
}
#endif

const CPU& CPU::GetInstanceNoAllocation() {
  static const base::NoDestructor<const CPU> cpu(CPU(false));

  return *cpu;
}

}  // namespace base