github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/cpuid/cpuid.go (about)

     1  // Copyright 2019 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package cpuid provides basic functionality for creating and adjusting CPU
    16  // feature sets.
    17  //
    18  // To use FeatureSets, one should start with an existing FeatureSet (either a
    19  // known platform, or HostFeatureSet()) and then add, remove, and test for
    20  // features as desired.
    21  //
    22  // For example: on x86, test for hardware extended state saving, and if
    23  // we don't have it, don't expose AVX, which cannot be saved with fxsave.
    24  //
    25  //   if !HostFeatureSet().HasFeature(X86FeatureXSAVE) {
    26  //     exposedFeatures.Remove(X86FeatureAVX)
    27  //   }
    28  package cpuid
    29  
    30  // Feature is a unique identifier for a particular cpu feature. We just use an
    31  // int as a feature number on x86 and arm64.
    32  //
    33  // On x86, features are numbered according to "blocks". Each block is 32 bits, and
    34  // feature bits from the same source (cpuid leaf/level) are in the same block.
    35  //
    36  // On arm64, features are numbered according to the ELF HWCAP definition.
    37  // arch/arm64/include/uapi/asm/hwcap.h
    38  type Feature int
    39  
    40  // ErrIncompatible is returned by FeatureSet.HostCompatible if fs is not a
    41  // subset of the host feature set.
    42  type ErrIncompatible struct {
    43  	message string
    44  }
    45  
    46  // Error implements error.
    47  func (e ErrIncompatible) Error() string {
    48  	return e.message
    49  }