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 <stdint.h>
#include <string.h>

#include <string>
#include <string_view>
#include <utility>

#include "base/containers/span.h"
#include "base/containers/span_writer.h"
#include "base/memory/protected_memory.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 <algorithm>

#include "base/files/file_util.h"
#include "base/numerics/checked_math.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
#endif

#if defined(ARCH_CPU_X86_FAMILY)
#if defined(COMPILER_MSVC)
#include <immintrin.h>  // For _xgetbv()
#include <intrin.h>
#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() {
  Initialize();
}

CPU::CPU(CPU&&) = default;

namespace {

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

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

// Requests extended feature information via |ecx|.
void __cpuidex(int cpu_info[4], int eax, int ecx) {
  // SAFETY: `cpu_info` has length 4 and therefore all accesses below are valid.
  UNSAFE_BUFFERS(
      __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"(eax), "c"(ecx)));
}

void __cpuid(int cpu_info[4], int info_type) {
  __cpuidex(cpu_info, info_type, /*ecx=*/0);
}

#else

// Requests extended feature information via |ecx|.
void __cpuidex(int cpu_info[4], int eax, int ecx) {
  // SAFETY: `cpu_info` has length 4 and therefore all accesses below are valid.
  UNSAFE_BUFFERS(__asm__ volatile("cpuid\n"
                                  : "=a"(cpu_info[0]), "=b"(cpu_info[1]),
                                    "=c"(cpu_info[2]), "=d"(cpu_info[3])
                                  : "a"(eax), "c"(ecx)));
}

void __cpuid(int cpu_info[4], int info_type) {
  __cpuidex(cpu_info, info_type, /*ecx=*/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

DEFINE_PROTECTED_DATA base::ProtectedMemory<CPU> g_cpu_instance;

}  // namespace

void CPU::Initialize() {
#if defined(ARCH_CPU_X86_FAMILY)
  int cpu_info[4] = {-1, 0, 0, 0};

  // __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 copying these three array elements to |cpu_vendor_|.
  __cpuid(cpu_info, 0);
  int num_ids = cpu_info[0];
  std::swap(cpu_info[2], cpu_info[3]);
  {
    SpanWriter writer{span(cpu_vendor_)};
    writer.Write(as_chars(span(cpu_info)).last<kVendorNameSize>());
    writer.Write('\0');
  }

  // Interpret CPU feature information.
  if (num_ids > 0) {
    int cpu_info7[4] = {};
    int cpu_einfo7[4] = {};
    __cpuid(cpu_info, 1);
    if (num_ids >= 7) {
      __cpuid(cpu_info7, 7);
      if (cpu_info7[0] >= 1) {
        __cpuidex(cpu_einfo7, 7, 1);
      }
    }
    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;
    if (has_avx_) {
      has_avx2_ = (cpu_info7[1] & 0x00000020) != 0;
      has_avx_vnni_ = (cpu_einfo7[0] & 0x00000010) != 0;
      // Check AVX-512 state, bits 5-7.
      if ((xgetbv(0) & 0xe0) == 0xe0) {
        has_avx512_f_ = (cpu_info7[1] & 0x00010000) != 0;
        has_avx512_bw_ = (cpu_info7[1] & 0x40000000) != 0;
        has_avx512_vnni_ = (cpu_info7[2] & 0x00000800) != 0;
      }
    }

    has_pku_ = (cpu_info7[2] & 0x00000010) != 0;
    has_pclmul_ = (cpu_info[2] & 0x00000002) != 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) == kBrandNameSize,
                "cpu_brand_ has wrong size");

  if (max_parameter >= kParameterEnd) {
    SpanWriter writer{span(cpu_brand_)};
    for (uint32_t parameter = kParameterStart; parameter <= kParameterEnd;
         ++parameter) {
      __cpuid(cpu_info, static_cast<int>(parameter));
      writer.Write(as_chars(span(cpu_info)));
    }
    writer.Write('\0');
  }

  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 defined(ARCH_CPU_ARM64) && \
    (BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS))
  // 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;
#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_avx512_vnni()) {
    return AVX512_VNNI;
  }
  if (has_avx512_bw()) {
    return AVX512BW;
  }
  if (has_avx512_f()) {
    return AVX512F;
  }
  if (has_avx_vnni()) {
    return AVX_VNNI;
  }
  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 ProtectedMemoryInitializer cpu_initializer(g_cpu_instance, CPU());

  return *g_cpu_instance;
}

}  // namespace base