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// Copyright 2017 The Crashpad Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "snapshot/x86/cpuid_reader.h"
#include <stddef.h>
#include "build/build_config.h"
#include "snapshot/cpu_context.h"
#if BUILDFLAG(IS_WIN)
#include <immintrin.h>
#include <intrin.h>
#endif // BUILDFLAG(IS_WIN)
#if defined(ARCH_CPU_X86_FAMILY)
namespace crashpad {
namespace internal {
CpuidReader::CpuidReader()
: features_(0),
extended_features_(0),
vendor_(),
max_leaf_(0),
signature_(0) {
uint32_t cpuinfo[4];
Cpuid(cpuinfo, 0);
max_leaf_ = cpuinfo[0];
vendor_.append(reinterpret_cast<char*>(&cpuinfo[1]), 4);
vendor_.append(reinterpret_cast<char*>(&cpuinfo[3]), 4);
vendor_.append(reinterpret_cast<char*>(&cpuinfo[2]), 4);
Cpuid(cpuinfo, 1);
signature_ = cpuinfo[0];
features_ = (static_cast<uint64_t>(cpuinfo[2]) << 32) |
static_cast<uint64_t>(cpuinfo[3]);
Cpuid(cpuinfo, 0x80000001);
extended_features_ = (static_cast<uint64_t>(cpuinfo[2]) << 32) |
static_cast<uint64_t>(cpuinfo[3]);
}
CpuidReader::~CpuidReader() {}
uint32_t CpuidReader::Revision() const {
uint8_t stepping = signature_ & 0xf;
uint8_t model = (signature_ & 0xf0) >> 4;
uint8_t family = (signature_ & 0xf00) >> 8;
uint8_t extended_model = static_cast<uint8_t>((signature_ & 0xf0000) >> 16);
uint16_t extended_family = (signature_ & 0xff00000) >> 20;
// For families before 15, extended_family are simply reserved bits.
if (family < 15)
extended_family = 0;
// extended_model is only used for families 6 and 15.
if (family != 6 && family != 15)
extended_model = 0;
uint16_t adjusted_family = family + extended_family;
uint8_t adjusted_model = model + (extended_model << 4);
return (adjusted_family << 16) | (adjusted_model << 8) | stepping;
}
uint32_t CpuidReader::Leaf7Features() const {
if (max_leaf_ < 7) {
return 0;
}
uint32_t cpuinfo[4];
Cpuid(cpuinfo, 7);
return cpuinfo[1];
}
bool CpuidReader::SupportsDAZ() const {
// The correct way to check for denormals-as-zeros (DAZ) support is to examine
// mxcsr mask, which can be done with fxsave. See Intel Software Developer’s
// Manual, Volume 1: Basic Architecture (253665-051), 11.6.3 “Checking for the
// DAZ Flag in the MXCSR Register”. Note that since this function tests for
// DAZ support in the CPU, it checks the mxcsr mask. Testing mxcsr would
// indicate whether DAZ is actually enabled, which is a per-thread context
// concern.
// Test for fxsave support.
if (!(features_ & (UINT64_C(1) << 24))) {
return false;
}
#if defined(ARCH_CPU_X86)
using Fxsave = CPUContextX86::Fxsave;
#elif defined(ARCH_CPU_X86_64)
using Fxsave = CPUContextX86_64::Fxsave;
#endif
#if BUILDFLAG(IS_WIN)
__declspec(align(16)) Fxsave fxsave = {};
#else
Fxsave fxsave __attribute__((aligned(16))) = {};
#endif
static_assert(sizeof(fxsave) == 512, "fxsave size");
static_assert(offsetof(decltype(fxsave), mxcsr_mask) == 28,
"mxcsr_mask offset");
#if BUILDFLAG(IS_WIN)
_fxsave(&fxsave);
#else
asm("fxsave %0" : "=m"(fxsave));
#endif
// Test the DAZ bit.
return (fxsave.mxcsr_mask & (1 << 6)) != 0;
}
void CpuidReader::Cpuid(uint32_t cpuinfo[4], uint32_t leaf) const {
#if BUILDFLAG(IS_WIN)
__cpuid(reinterpret_cast<int*>(cpuinfo), leaf);
#else
asm("cpuid"
: "=a"(cpuinfo[0]), "=b"(cpuinfo[1]), "=c"(cpuinfo[2]), "=d"(cpuinfo[3])
: "a"(leaf), "b"(0), "c"(0), "d"(0));
#endif // BUILDFLAG(IS_WIN)
}
} // namespace internal
} // namespace crashpad
#endif // ARCH_CPU_X86_FAMILY