Merge pull request #1453 from xiaobo55x:cpuid

PiperOrigin-RevId: 294257911

1 files changed, 1100 insertions, 0 deletions

diff --git a/pkg/cpuid/cpuid_x86.go b/pkg/cpuid/cpuid_x86.go
new file mode 100644
index 000000000..333ca0a04
--- /dev/null
+++ b/pkg/cpuid/cpuid_x86.go
@@ -0,0 +1,1100 @@
+// Copyright 2019 The gVisor Authors.
+//
+// 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.
+
+// +build i386 amd64
+
+package cpuid
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/log"
+)
+
+// Common references for CPUID leaves and bits:
+//
+// Intel:
+//   * Intel SDM Volume 2, Chapter 3.2 "CPUID" (more up-to-date)
+//   * Intel Application Note 485 (more detailed)
+//
+// AMD:
+//   * AMD64 APM Volume 3, Appendix 3 "Obtaining Processor Information ..."
+
+// block is a collection of 32 Feature bits.
+type block int
+
+const blockSize = 32
+
+// Feature bits are numbered according to "blocks". Each block is 32 bits, and
+// feature bits from the same source (cpuid leaf/level) are in the same block.
+func featureID(b block, bit int) Feature {
+	return Feature(32*int(b) + bit)
+}
+
+// Block 0 constants are all of the "basic" feature bits returned by a cpuid in
+// ecx with eax=1.
+const (
+	X86FeatureSSE3 Feature = iota
+	X86FeaturePCLMULDQ
+	X86FeatureDTES64
+	X86FeatureMONITOR
+	X86FeatureDSCPL
+	X86FeatureVMX
+	X86FeatureSMX
+	X86FeatureEST
+	X86FeatureTM2
+	X86FeatureSSSE3 // Not a typo, "supplemental" SSE3.
+	X86FeatureCNXTID
+	X86FeatureSDBG
+	X86FeatureFMA
+	X86FeatureCX16
+	X86FeatureXTPR
+	X86FeaturePDCM
+	_ // ecx bit 16 is reserved.
+	X86FeaturePCID
+	X86FeatureDCA
+	X86FeatureSSE4_1
+	X86FeatureSSE4_2
+	X86FeatureX2APIC
+	X86FeatureMOVBE
+	X86FeaturePOPCNT
+	X86FeatureTSCD
+	X86FeatureAES
+	X86FeatureXSAVE
+	X86FeatureOSXSAVE
+	X86FeatureAVX
+	X86FeatureF16C
+	X86FeatureRDRAND
+	_ // ecx bit 31 is reserved.
+)
+
+// Block 1 constants are all of the "basic" feature bits returned by a cpuid in
+// edx with eax=1.
+const (
+	X86FeatureFPU Feature = 32 + iota
+	X86FeatureVME
+	X86FeatureDE
+	X86FeaturePSE
+	X86FeatureTSC
+	X86FeatureMSR
+	X86FeaturePAE
+	X86FeatureMCE
+	X86FeatureCX8
+	X86FeatureAPIC
+	_ // edx bit 10 is reserved.
+	X86FeatureSEP
+	X86FeatureMTRR
+	X86FeaturePGE
+	X86FeatureMCA
+	X86FeatureCMOV
+	X86FeaturePAT
+	X86FeaturePSE36
+	X86FeaturePSN
+	X86FeatureCLFSH
+	_ // edx bit 20 is reserved.
+	X86FeatureDS
+	X86FeatureACPI
+	X86FeatureMMX
+	X86FeatureFXSR
+	X86FeatureSSE
+	X86FeatureSSE2
+	X86FeatureSS
+	X86FeatureHTT
+	X86FeatureTM
+	X86FeatureIA64
+	X86FeaturePBE
+)
+
+// Block 2 bits are the "structured extended" features returned in ebx for
+// eax=7, ecx=0.
+const (
+	X86FeatureFSGSBase Feature = 2*32 + iota
+	X86FeatureTSC_ADJUST
+	_ // ebx bit 2 is reserved.
+	X86FeatureBMI1
+	X86FeatureHLE
+	X86FeatureAVX2
+	X86FeatureFDP_EXCPTN_ONLY
+	X86FeatureSMEP
+	X86FeatureBMI2
+	X86FeatureERMS
+	X86FeatureINVPCID
+	X86FeatureRTM
+	X86FeatureCQM
+	X86FeatureFPCSDS
+	X86FeatureMPX
+	X86FeatureRDT
+	X86FeatureAVX512F
+	X86FeatureAVX512DQ
+	X86FeatureRDSEED
+	X86FeatureADX
+	X86FeatureSMAP
+	X86FeatureAVX512IFMA
+	X86FeaturePCOMMIT
+	X86FeatureCLFLUSHOPT
+	X86FeatureCLWB
+	X86FeatureIPT // Intel processor trace.
+	X86FeatureAVX512PF
+	X86FeatureAVX512ER
+	X86FeatureAVX512CD
+	X86FeatureSHA
+	X86FeatureAVX512BW
+	X86FeatureAVX512VL
+)
+
+// Block 3 bits are the "extended" features returned in ecx for eax=7, ecx=0.
+const (
+	X86FeaturePREFETCHWT1 Feature = 3*32 + iota
+	X86FeatureAVX512VBMI
+	X86FeatureUMIP
+	X86FeaturePKU
+	X86FeatureOSPKE
+	X86FeatureWAITPKG
+	X86FeatureAVX512_VBMI2
+	_ // ecx bit 7 is reserved
+	X86FeatureGFNI
+	X86FeatureVAES
+	X86FeatureVPCLMULQDQ
+	X86FeatureAVX512_VNNI
+	X86FeatureAVX512_BITALG
+	X86FeatureTME
+	X86FeatureAVX512_VPOPCNTDQ
+	_ // ecx bit 15 is reserved
+	X86FeatureLA57
+	// ecx bits 17-21 are reserved
+	_
+	_
+	_
+	_
+	_
+	X86FeatureRDPID
+	// ecx bits 23-24 are reserved
+	_
+	_
+	X86FeatureCLDEMOTE
+	_ // ecx bit 26 is reserved
+	X86FeatureMOVDIRI
+	X86FeatureMOVDIR64B
+)
+
+// Block 4 constants are for xsave capabilities in CPUID.(EAX=0DH,ECX=01H):EAX.
+// The CPUID leaf is available only if 'X86FeatureXSAVE' is present.
+const (
+	X86FeatureXSAVEOPT Feature = 4*32 + iota
+	X86FeatureXSAVEC
+	X86FeatureXGETBV1
+	X86FeatureXSAVES
+	// EAX[31:4] are reserved.
+)
+
+// Block 5 constants are the extended feature bits in
+// CPUID.(EAX=0x80000001):ECX.
+const (
+	X86FeatureLAHF64 Feature = 5*32 + iota
+	X86FeatureCMP_LEGACY
+	X86FeatureSVM
+	X86FeatureEXTAPIC
+	X86FeatureCR8_LEGACY
+	X86FeatureLZCNT
+	X86FeatureSSE4A
+	X86FeatureMISALIGNSSE
+	X86FeaturePREFETCHW
+	X86FeatureOSVW
+	X86FeatureIBS
+	X86FeatureXOP
+	X86FeatureSKINIT
+	X86FeatureWDT
+	_ // ecx bit 14 is reserved.
+	X86FeatureLWP
+	X86FeatureFMA4
+	X86FeatureTCE
+	_ // ecx bit 18 is reserved.
+	_ // ecx bit 19 is reserved.
+	_ // ecx bit 20 is reserved.
+	X86FeatureTBM
+	X86FeatureTOPOLOGY
+	X86FeaturePERFCTR_CORE
+	X86FeaturePERFCTR_NB
+	_ // ecx bit 25 is reserved.
+	X86FeatureBPEXT
+	X86FeaturePERFCTR_TSC
+	X86FeaturePERFCTR_LLC
+	X86FeatureMWAITX
+	// ECX[31:30] are reserved.
+)
+
+// Block 6 constants are the extended feature bits in
+// CPUID.(EAX=0x80000001):EDX.
+//
+// These are sparse, and so the bit positions are assigned manually.
+const (
+	// On AMD, EDX[24:23] | EDX[17:12] | EDX[9:0] are duplicate features
+	// also defined in block 1 (in identical bit positions). Those features
+	// are not listed here.
+	block6DuplicateMask = 0x183f3ff
+
+	X86FeatureSYSCALL  Feature = 6*32 + 11
+	X86FeatureNX       Feature = 6*32 + 20
+	X86FeatureMMXEXT   Feature = 6*32 + 22
+	X86FeatureFXSR_OPT Feature = 6*32 + 25
+	X86FeatureGBPAGES  Feature = 6*32 + 26
+	X86FeatureRDTSCP   Feature = 6*32 + 27
+	X86FeatureLM       Feature = 6*32 + 29
+	X86Feature3DNOWEXT Feature = 6*32 + 30
+	X86Feature3DNOW    Feature = 6*32 + 31
+)
+
+// linuxBlockOrder defines the order in which linux organizes the feature
+// blocks. Linux also tracks feature bits in 32-bit blocks, but in an order
+// which doesn't match well here, so for the /proc/cpuinfo generation we simply
+// re-map the blocks to Linux's ordering and then go through the bits in each
+// block.
+var linuxBlockOrder = []block{1, 6, 0, 5, 2, 4, 3}
+
+// To make emulation of /proc/cpuinfo easy, these names match the names of the
+// basic features in Linux defined in arch/x86/kernel/cpu/capflags.c.
+var x86FeatureStrings = map[Feature]string{
+	// Block 0.
+	X86FeatureSSE3:     "pni",
+	X86FeaturePCLMULDQ: "pclmulqdq",
+	X86FeatureDTES64:   "dtes64",
+	X86FeatureMONITOR:  "monitor",
+	X86FeatureDSCPL:    "ds_cpl",
+	X86FeatureVMX:      "vmx",
+	X86FeatureSMX:      "smx",
+	X86FeatureEST:      "est",
+	X86FeatureTM2:      "tm2",
+	X86FeatureSSSE3:    "ssse3",
+	X86FeatureCNXTID:   "cid",
+	X86FeatureSDBG:     "sdbg",
+	X86FeatureFMA:      "fma",
+	X86FeatureCX16:     "cx16",
+	X86FeatureXTPR:     "xtpr",
+	X86FeaturePDCM:     "pdcm",
+	X86FeaturePCID:     "pcid",
+	X86FeatureDCA:      "dca",
+	X86FeatureSSE4_1:   "sse4_1",
+	X86FeatureSSE4_2:   "sse4_2",
+	X86FeatureX2APIC:   "x2apic",
+	X86FeatureMOVBE:    "movbe",
+	X86FeaturePOPCNT:   "popcnt",
+	X86FeatureTSCD:     "tsc_deadline_timer",
+	X86FeatureAES:      "aes",
+	X86FeatureXSAVE:    "xsave",
+	X86FeatureAVX:      "avx",
+	X86FeatureF16C:     "f16c",
+	X86FeatureRDRAND:   "rdrand",
+
+	// Block 1.
+	X86FeatureFPU:   "fpu",
+	X86FeatureVME:   "vme",
+	X86FeatureDE:    "de",
+	X86FeaturePSE:   "pse",
+	X86FeatureTSC:   "tsc",
+	X86FeatureMSR:   "msr",
+	X86FeaturePAE:   "pae",
+	X86FeatureMCE:   "mce",
+	X86FeatureCX8:   "cx8",
+	X86FeatureAPIC:  "apic",
+	X86FeatureSEP:   "sep",
+	X86FeatureMTRR:  "mtrr",
+	X86FeaturePGE:   "pge",
+	X86FeatureMCA:   "mca",
+	X86FeatureCMOV:  "cmov",
+	X86FeaturePAT:   "pat",
+	X86FeaturePSE36: "pse36",
+	X86FeaturePSN:   "pn",
+	X86FeatureCLFSH: "clflush",
+	X86FeatureDS:    "dts",
+	X86FeatureACPI:  "acpi",
+	X86FeatureMMX:   "mmx",
+	X86FeatureFXSR:  "fxsr",
+	X86FeatureSSE:   "sse",
+	X86FeatureSSE2:  "sse2",
+	X86FeatureSS:    "ss",
+	X86FeatureHTT:   "ht",
+	X86FeatureTM:    "tm",
+	X86FeatureIA64:  "ia64",
+	X86FeaturePBE:   "pbe",
+
+	// Block 2.
+	X86FeatureFSGSBase:   "fsgsbase",
+	X86FeatureTSC_ADJUST: "tsc_adjust",
+	X86FeatureBMI1:       "bmi1",
+	X86FeatureHLE:        "hle",
+	X86FeatureAVX2:       "avx2",
+	X86FeatureSMEP:       "smep",
+	X86FeatureBMI2:       "bmi2",
+	X86FeatureERMS:       "erms",
+	X86FeatureINVPCID:    "invpcid",
+	X86FeatureRTM:        "rtm",
+	X86FeatureCQM:        "cqm",
+	X86FeatureMPX:        "mpx",
+	X86FeatureRDT:        "rdt_a",
+	X86FeatureAVX512F:    "avx512f",
+	X86FeatureAVX512DQ:   "avx512dq",
+	X86FeatureRDSEED:     "rdseed",
+	X86FeatureADX:        "adx",
+	X86FeatureSMAP:       "smap",
+	X86FeatureCLWB:       "clwb",
+	X86FeatureAVX512PF:   "avx512pf",
+	X86FeatureAVX512ER:   "avx512er",
+	X86FeatureAVX512CD:   "avx512cd",
+	X86FeatureSHA:        "sha_ni",
+	X86FeatureAVX512BW:   "avx512bw",
+	X86FeatureAVX512VL:   "avx512vl",
+
+	// Block 3.
+	X86FeatureAVX512VBMI:       "avx512vbmi",
+	X86FeatureUMIP:             "umip",
+	X86FeaturePKU:              "pku",
+	X86FeatureOSPKE:            "ospke",
+	X86FeatureWAITPKG:          "waitpkg",
+	X86FeatureAVX512_VBMI2:     "avx512_vbmi2",
+	X86FeatureGFNI:             "gfni",
+	X86FeatureVAES:             "vaes",
+	X86FeatureVPCLMULQDQ:       "vpclmulqdq",
+	X86FeatureAVX512_VNNI:      "avx512_vnni",
+	X86FeatureAVX512_BITALG:    "avx512_bitalg",
+	X86FeatureTME:              "tme",
+	X86FeatureAVX512_VPOPCNTDQ: "avx512_vpopcntdq",
+	X86FeatureLA57:             "la57",
+	X86FeatureRDPID:            "rdpid",
+	X86FeatureCLDEMOTE:         "cldemote",
+	X86FeatureMOVDIRI:          "movdiri",
+	X86FeatureMOVDIR64B:        "movdir64b",
+
+	// Block 4.
+	X86FeatureXSAVEOPT: "xsaveopt",
+	X86FeatureXSAVEC:   "xsavec",
+	X86FeatureXGETBV1:  "xgetbv1",
+	X86FeatureXSAVES:   "xsaves",
+
+	// Block 5.
+	X86FeatureLAHF64:       "lahf_lm", // LAHF/SAHF in long mode
+	X86FeatureCMP_LEGACY:   "cmp_legacy",
+	X86FeatureSVM:          "svm",
+	X86FeatureEXTAPIC:      "extapic",
+	X86FeatureCR8_LEGACY:   "cr8_legacy",
+	X86FeatureLZCNT:        "abm", // Advanced bit manipulation
+	X86FeatureSSE4A:        "sse4a",
+	X86FeatureMISALIGNSSE:  "misalignsse",
+	X86FeaturePREFETCHW:    "3dnowprefetch",
+	X86FeatureOSVW:         "osvw",
+	X86FeatureIBS:          "ibs",
+	X86FeatureXOP:          "xop",
+	X86FeatureSKINIT:       "skinit",
+	X86FeatureWDT:          "wdt",
+	X86FeatureLWP:          "lwp",
+	X86FeatureFMA4:         "fma4",
+	X86FeatureTCE:          "tce",
+	X86FeatureTBM:          "tbm",
+	X86FeatureTOPOLOGY:     "topoext",
+	X86FeaturePERFCTR_CORE: "perfctr_core",
+	X86FeaturePERFCTR_NB:   "perfctr_nb",
+	X86FeatureBPEXT:        "bpext",
+	X86FeaturePERFCTR_TSC:  "ptsc",
+	X86FeaturePERFCTR_LLC:  "perfctr_llc",
+	X86FeatureMWAITX:       "mwaitx",
+
+	// Block 6.
+	X86FeatureSYSCALL:  "syscall",
+	X86FeatureNX:       "nx",
+	X86FeatureMMXEXT:   "mmxext",
+	X86FeatureFXSR_OPT: "fxsr_opt",
+	X86FeatureGBPAGES:  "pdpe1gb",
+	X86FeatureRDTSCP:   "rdtscp",
+	X86FeatureLM:       "lm",
+	X86Feature3DNOWEXT: "3dnowext",
+	X86Feature3DNOW:    "3dnow",
+}
+
+// These flags are parse only---they can be used for setting / unsetting the
+// flags, but will not get printed out in /proc/cpuinfo.
+var x86FeatureParseOnlyStrings = map[Feature]string{
+	// Block 0.
+	X86FeatureOSXSAVE: "osxsave",
+
+	// Block 2.
+	X86FeatureFDP_EXCPTN_ONLY: "fdp_excptn_only",
+	X86FeatureFPCSDS:          "fpcsds",
+	X86FeatureIPT:             "pt",
+	X86FeatureCLFLUSHOPT:      "clfushopt",
+
+	// Block 3.
+	X86FeaturePREFETCHWT1: "prefetchwt1",
+}
+
+// intelCacheDescriptors describe the caches and TLBs on the system. They are
+// returned in the registers for eax=2. Intel only.
+type intelCacheDescriptor uint8
+
+// Valid cache/TLB descriptors. All descriptors can be found in Intel SDM Vol.
+// 2, Ch. 3.2, "CPUID", Table 3-12 "Encoding of CPUID Leaf 2 Descriptors".
+const (
+	intelNullDescriptor    intelCacheDescriptor = 0
+	intelNoTLBDescriptor   intelCacheDescriptor = 0xfe
+	intelNoCacheDescriptor intelCacheDescriptor = 0xff
+
+	// Most descriptors omitted for brevity as they are currently unused.
+)
+
+// CacheType describes the type of a cache, as returned in eax[4:0] for eax=4.
+type CacheType uint8
+
+const (
+	// cacheNull indicates that there are no more entries.
+	cacheNull CacheType = iota
+
+	// CacheData is a data cache.
+	CacheData
+
+	// CacheInstruction is an instruction cache.
+	CacheInstruction
+
+	// CacheUnified is a unified instruction and data cache.
+	CacheUnified
+)
+
+// Cache describes the parameters of a single cache on the system.
+//
+// +stateify savable
+type Cache struct {
+	// Level is the hierarchical level of this cache (L1, L2, etc).
+	Level uint32
+
+	// Type is the type of cache.
+	Type CacheType
+
+	// FullyAssociative indicates that entries may be placed in any block.
+	FullyAssociative bool
+
+	// Partitions is the number of physical partitions in the cache.
+	Partitions uint32
+
+	// Ways is the number of ways of associativity in the cache.
+	Ways uint32
+
+	// Sets is the number of sets in the cache.
+	Sets uint32
+
+	// InvalidateHierarchical indicates that WBINVD/INVD from threads
+	// sharing this cache acts upon lower level caches for threads sharing
+	// this cache.
+	InvalidateHierarchical bool
+
+	// Inclusive indicates that this cache is inclusive of lower cache
+	// levels.
+	Inclusive bool
+
+	// DirectMapped indicates that this cache is directly mapped from
+	// address, rather than using a hash function.
+	DirectMapped bool
+}
+
+// Just a way to wrap cpuid function numbers.
+type cpuidFunction uint32
+
+// The constants below are the lower or "standard" cpuid functions, ordered as
+// defined by the hardware.
+const (
+	vendorID                      cpuidFunction = iota // Returns vendor ID and largest standard function.
+	featureInfo                                        // Returns basic feature bits and processor signature.
+	intelCacheDescriptors                              // Returns list of cache descriptors. Intel only.
+	intelSerialNumber                                  // Returns processor serial number (obsolete on new hardware). Intel only.
+	intelDeterministicCacheParams                      // Returns deterministic cache information. Intel only.
+	monitorMwaitParams                                 // Returns information about monitor/mwait instructions.
+	powerParams                                        // Returns information about power management and thermal sensors.
+	extendedFeatureInfo                                // Returns extended feature bits.
+	_                                                  // Function 0x8 is reserved.
+	intelDCAParams                                     // Returns direct cache access information. Intel only.
+	intelPMCInfo                                       // Returns information about performance monitoring features. Intel only.
+	intelX2APICInfo                                    // Returns core/logical processor topology. Intel only.
+	_                                                  // Function 0xc is reserved.
+	xSaveInfo                                          // Returns information about extended state management.
+)
+
+// The "extended" functions start at 0x80000000.
+const (
+	extendedFunctionInfo cpuidFunction = 0x80000000 + iota // Returns highest available extended function in eax.
+	extendedFeatures                                       // Returns some extended feature bits in edx and ecx.
+)
+
+// These are the extended floating point state features. They are used to
+// enumerate floating point features in XCR0, XSTATE_BV, etc.
+const (
+	XSAVEFeatureX87         = 1 << 0
+	XSAVEFeatureSSE         = 1 << 1
+	XSAVEFeatureAVX         = 1 << 2
+	XSAVEFeatureBNDREGS     = 1 << 3
+	XSAVEFeatureBNDCSR      = 1 << 4
+	XSAVEFeatureAVX512op    = 1 << 5
+	XSAVEFeatureAVX512zmm0  = 1 << 6
+	XSAVEFeatureAVX512zmm16 = 1 << 7
+	XSAVEFeaturePKRU        = 1 << 9
+)
+
+var cpuFreqMHz float64
+
+// x86FeaturesFromString includes features from x86FeatureStrings and
+// x86FeatureParseOnlyStrings.
+var x86FeaturesFromString = make(map[string]Feature)
+
+// FeatureFromString returns the Feature associated with the given feature
+// string plus a bool to indicate if it could find the feature.
+func FeatureFromString(s string) (Feature, bool) {
+	f, b := x86FeaturesFromString[s]
+	return f, b
+}
+
+// String implements fmt.Stringer.
+func (f Feature) String() string {
+	if s := f.flagString(false); s != "" {
+		return s
+	}
+
+	block := int(f) / 32
+	bit := int(f) % 32
+	return fmt.Sprintf("<cpuflag %d; block %d bit %d>", f, block, bit)
+}
+
+func (f Feature) flagString(cpuinfoOnly bool) string {
+	if s, ok := x86FeatureStrings[f]; ok {
+		return s
+	}
+	if !cpuinfoOnly {
+		return x86FeatureParseOnlyStrings[f]
+	}
+	return ""
+}
+
+// FeatureSet is a set of Features for a CPU.
+//
+// +stateify savable
+type FeatureSet struct {
+	// Set is the set of features that are enabled in this FeatureSet.
+	Set map[Feature]bool
+
+	// VendorID is the 12-char string returned in ebx:edx:ecx for eax=0.
+	VendorID string
+
+	// ExtendedFamily is part of the processor signature.
+	ExtendedFamily uint8
+
+	// ExtendedModel is part of the processor signature.
+	ExtendedModel uint8
+
+	// ProcessorType is part of the processor signature.
+	ProcessorType uint8
+
+	// Family is part of the processor signature.
+	Family uint8
+
+	// Model is part of the processor signature.
+	Model uint8
+
+	// SteppingID is part of the processor signature.
+	SteppingID uint8
+
+	// Caches describes the caches on the CPU.
+	Caches []Cache
+
+	// CacheLine is the size of a cache line in bytes.
+	//
+	// All caches use the same line size. This is not enforced in the CPUID
+	// encoding, but is true on all known x86 processors.
+	CacheLine uint32
+}
+
+// FlagsString prints out supported CPU flags. If cpuinfoOnly is true, it is
+// equivalent to the "flags" field in /proc/cpuinfo.
+func (fs *FeatureSet) FlagsString(cpuinfoOnly bool) string {
+	var s []string
+	for _, b := range linuxBlockOrder {
+		for i := 0; i < blockSize; i++ {
+			if f := featureID(b, i); fs.Set[f] {
+				if fstr := f.flagString(cpuinfoOnly); fstr != "" {
+					s = append(s, fstr)
+				}
+			}
+		}
+	}
+	return strings.Join(s, " ")
+}
+
+// WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
+// a minimal /proc/cpuinfo, it is missing some fields like "microcode" that are
+// not always printed in Linux. The bogomips field is simply made up.
+func (fs FeatureSet) WriteCPUInfoTo(cpu uint, b *bytes.Buffer) {
+	fmt.Fprintf(b, "processor\t: %d\n", cpu)
+	fmt.Fprintf(b, "vendor_id\t: %s\n", fs.VendorID)
+	fmt.Fprintf(b, "cpu family\t: %d\n", ((fs.ExtendedFamily<<4)&0xff)|fs.Family)
+	fmt.Fprintf(b, "model\t\t: %d\n", ((fs.ExtendedModel<<4)&0xff)|fs.Model)
+	fmt.Fprintf(b, "model name\t: %s\n", "unknown") // Unknown for now.
+	fmt.Fprintf(b, "stepping\t: %s\n", "unknown")   // Unknown for now.
+	fmt.Fprintf(b, "cpu MHz\t\t: %.3f\n", cpuFreqMHz)
+	fmt.Fprintln(b, "fpu\t\t: yes")
+	fmt.Fprintln(b, "fpu_exception\t: yes")
+	fmt.Fprintf(b, "cpuid level\t: %d\n", uint32(xSaveInfo)) // Same as ax in vendorID.
+	fmt.Fprintln(b, "wp\t\t: yes")
+	fmt.Fprintf(b, "flags\t\t: %s\n", fs.FlagsString(true))
+	fmt.Fprintf(b, "bogomips\t: %.02f\n", cpuFreqMHz) // It's bogus anyway.
+	fmt.Fprintf(b, "clflush size\t: %d\n", fs.CacheLine)
+	fmt.Fprintf(b, "cache_alignment\t: %d\n", fs.CacheLine)
+	fmt.Fprintf(b, "address sizes\t: %d bits physical, %d bits virtual\n", 46, 48)
+	fmt.Fprintln(b, "power management:") // This is always here, but can be blank.
+	fmt.Fprintln(b, "")                  // The /proc/cpuinfo file ends with an extra newline.
+}
+
+const (
+	amdVendorID   = "AuthenticAMD"
+	intelVendorID = "GenuineIntel"
+)
+
+// AMD returns true if fs describes an AMD CPU.
+func (fs *FeatureSet) AMD() bool {
+	return fs.VendorID == amdVendorID
+}
+
+// Intel returns true if fs describes an Intel CPU.
+func (fs *FeatureSet) Intel() bool {
+	return fs.VendorID == intelVendorID
+}
+
+// ErrIncompatible is returned by FeatureSet.HostCompatible if fs is not a
+// subset of the host feature set.
+type ErrIncompatible struct {
+	message string
+}
+
+// Error implements error.
+func (e ErrIncompatible) Error() string {
+	return e.message
+}
+
+// CheckHostCompatible returns nil if fs is a subset of the host feature set.
+func (fs *FeatureSet) CheckHostCompatible() error {
+	hfs := HostFeatureSet()
+
+	if diff := fs.Subtract(hfs); diff != nil {
+		return ErrIncompatible{fmt.Sprintf("CPU feature set %v incompatible with host feature set %v (missing: %v)", fs.FlagsString(false), hfs.FlagsString(false), diff)}
+	}
+
+	// The size of a cache line must match, as it is critical to correctly
+	// utilizing CLFLUSH. Other cache properties are allowed to change, as
+	// they are not important to correctness.
+	if fs.CacheLine != hfs.CacheLine {
+		return ErrIncompatible{fmt.Sprintf("CPU cache line size %d incompatible with host cache line size %d", fs.CacheLine, hfs.CacheLine)}
+	}
+
+	return nil
+}
+
+// Helper to convert 3 regs into 12-byte vendor ID.
+func vendorIDFromRegs(bx, cx, dx uint32) string {
+	bytes := make([]byte, 0, 12)
+	for i := uint(0); i < 4; i++ {
+		b := byte(bx >> (i * 8))
+		bytes = append(bytes, b)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		b := byte(dx >> (i * 8))
+		bytes = append(bytes, b)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		b := byte(cx >> (i * 8))
+		bytes = append(bytes, b)
+	}
+	return string(bytes)
+}
+
+// ExtendedStateSize returns the number of bytes needed to save the "extended
+// state" for this processor and the boundary it must be aligned to. Extended
+// state includes floating point registers, and other cpu state that's not
+// associated with the normal task context.
+//
+// Note: We can save some space here with an optimization where we use a
+// smaller chunk of memory depending on features that are actually enabled.
+// Currently we just use the largest possible size for simplicity (which is
+// about 2.5K worst case, with avx512).
+func (fs *FeatureSet) ExtendedStateSize() (size, align uint) {
+	if fs.UseXsave() {
+		// Leaf 0 of xsaveinfo function returns the size for currently
+		// enabled xsave features in ebx, the maximum size if all valid
+		// features are saved with xsave in ecx, and valid XCR0 bits in
+		// edx:eax.
+		_, _, maxSize, _ := HostID(uint32(xSaveInfo), 0)
+		return uint(maxSize), 64
+	}
+
+	// If we don't support xsave, we fall back to fxsave, which requires
+	// 512 bytes aligned to 16 bytes.
+	return 512, 16
+}
+
+// ValidXCR0Mask returns the bits that may be set to 1 in control register
+// XCR0.
+func (fs *FeatureSet) ValidXCR0Mask() uint64 {
+	if !fs.UseXsave() {
+		return 0
+	}
+	eax, _, _, edx := HostID(uint32(xSaveInfo), 0)
+	return uint64(edx)<<32 | uint64(eax)
+}
+
+// vendorIDRegs returns the 3 register values used to construct the 12-byte
+// vendor ID string for eax=0.
+func (fs *FeatureSet) vendorIDRegs() (bx, dx, cx uint32) {
+	for i := uint(0); i < 4; i++ {
+		bx |= uint32(fs.VendorID[i]) << (i * 8)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		dx |= uint32(fs.VendorID[i+4]) << (i * 8)
+	}
+
+	for i := uint(0); i < 4; i++ {
+		cx |= uint32(fs.VendorID[i+8]) << (i * 8)
+	}
+	return
+}
+
+// signature returns the signature dword that's returned in eax when eax=1.
+func (fs *FeatureSet) signature() uint32 {
+	var s uint32
+	s |= uint32(fs.SteppingID & 0xf)
+	s |= uint32(fs.Model&0xf) << 4
+	s |= uint32(fs.Family&0xf) << 8
+	s |= uint32(fs.ProcessorType&0x3) << 12
+	s |= uint32(fs.ExtendedModel&0xf) << 16
+	s |= uint32(fs.ExtendedFamily&0xff) << 20
+	return s
+}
+
+// Helper to deconstruct signature dword.
+func signatureSplit(v uint32) (ef, em, pt, f, m, sid uint8) {
+	sid = uint8(v & 0xf)
+	m = uint8(v>>4) & 0xf
+	f = uint8(v>>8) & 0xf
+	pt = uint8(v>>12) & 0x3
+	em = uint8(v>>16) & 0xf
+	ef = uint8(v >> 20)
+	return
+}
+
+// Helper to convert blockwise feature bit masks into a set of features. Masks
+// must be provided in order for each block, without skipping them. If a block
+// does not matter for this feature set, 0 is specified.
+func setFromBlockMasks(blocks ...uint32) map[Feature]bool {
+	s := make(map[Feature]bool)
+	for b, blockMask := range blocks {
+		for i := 0; i < blockSize; i++ {
+			if blockMask&1 != 0 {
+				s[featureID(block(b), i)] = true
+			}
+			blockMask >>= 1
+		}
+	}
+	return s
+}
+
+// blockMask returns the 32-bit mask associated with a block of features.
+func (fs *FeatureSet) blockMask(b block) uint32 {
+	var mask uint32
+	for i := 0; i < blockSize; i++ {
+		if fs.Set[featureID(b, i)] {
+			mask |= 1 << uint(i)
+		}
+	}
+	return mask
+}
+
+// Remove removes a Feature from a FeatureSet. It ignores features
+// that are not in the FeatureSet.
+func (fs *FeatureSet) Remove(feature Feature) {
+	delete(fs.Set, feature)
+}
+
+// Add adds a Feature to a FeatureSet. It ignores duplicate features.
+func (fs *FeatureSet) Add(feature Feature) {
+	fs.Set[feature] = true
+}
+
+// HasFeature tests whether or not a feature is in the given feature set.
+func (fs *FeatureSet) HasFeature(feature Feature) bool {
+	return fs.Set[feature]
+}
+
+// Subtract returns the features present in fs that are not present in other.
+// If all features in fs are present in other, Subtract returns nil.
+func (fs *FeatureSet) Subtract(other *FeatureSet) (diff map[Feature]bool) {
+	for f := range fs.Set {
+		if !other.Set[f] {
+			if diff == nil {
+				diff = make(map[Feature]bool)
+			}
+			diff[f] = true
+		}
+	}
+
+	return
+}
+
+// EmulateID emulates a cpuid instruction based on the feature set.
+func (fs *FeatureSet) EmulateID(origAx, origCx uint32) (ax, bx, cx, dx uint32) {
+	switch cpuidFunction(origAx) {
+	case vendorID:
+		ax = uint32(xSaveInfo) // 0xd (xSaveInfo) is the highest function we support.
+		bx, dx, cx = fs.vendorIDRegs()
+	case featureInfo:
+		// CLFLUSH line size is encoded in quadwords. Other fields in bx unsupported.
+		bx = (fs.CacheLine / 8) << 8
+		cx = fs.blockMask(block(0))
+		dx = fs.blockMask(block(1))
+		ax = fs.signature()
+	case intelCacheDescriptors:
+		if !fs.Intel() {
+			// Reserved on non-Intel.
+			return 0, 0, 0, 0
+		}
+
+		// "The least-significant byte in register EAX (register AL)
+		// will always return 01H. Software should ignore this value
+		// and not interpret it as an informational descriptor." - SDM
+		//
+		// We only support reporting cache parameters via
+		// intelDeterministicCacheParams; report as much here.
+		//
+		// We do not support exposing TLB information at all.
+		ax = 1 | (uint32(intelNoCacheDescriptor) << 8)
+	case intelDeterministicCacheParams:
+		if !fs.Intel() {
+			// Reserved on non-Intel.
+			return 0, 0, 0, 0
+		}
+
+		// cx is the index of the cache to describe.
+		if int(origCx) >= len(fs.Caches) {
+			return uint32(cacheNull), 0, 0, 0
+		}
+		c := fs.Caches[origCx]
+
+		ax = uint32(c.Type)
+		ax |= c.Level << 5
+		ax |= 1 << 8 // Always claim the cache is "self-initializing".
+		if c.FullyAssociative {
+			ax |= 1 << 9
+		}
+		// Processor topology not supported.
+
+		bx = fs.CacheLine - 1
+		bx |= (c.Partitions - 1) << 12
+		bx |= (c.Ways - 1) << 22
+
+		cx = c.Sets - 1
+
+		if !c.InvalidateHierarchical {
+			dx |= 1
+		}
+		if c.Inclusive {
+			dx |= 1 << 1
+		}
+		if !c.DirectMapped {
+			dx |= 1 << 2
+		}
+	case xSaveInfo:
+		if !fs.UseXsave() {
+			return 0, 0, 0, 0
+		}
+		return HostID(uint32(xSaveInfo), origCx)
+	case extendedFeatureInfo:
+		if origCx != 0 {
+			break // Only leaf 0 is supported.
+		}
+		bx = fs.blockMask(block(2))
+		cx = fs.blockMask(block(3))
+	case extendedFunctionInfo:
+		// We only support showing the extended features.
+		ax = uint32(extendedFeatures)
+		cx = 0
+	case extendedFeatures:
+		cx = fs.blockMask(block(5))
+		dx = fs.blockMask(block(6))
+		if fs.AMD() {
+			// AMD duplicates some block 1 features in block 6.
+			dx |= fs.blockMask(block(1)) & block6DuplicateMask
+		}
+	}
+
+	return
+}
+
+// UseXsave returns the choice of fp state saving instruction.
+func (fs *FeatureSet) UseXsave() bool {
+	return fs.HasFeature(X86FeatureXSAVE) && fs.HasFeature(X86FeatureOSXSAVE)
+}
+
+// UseXsaveopt returns true if 'fs' supports the "xsaveopt" instruction.
+func (fs *FeatureSet) UseXsaveopt() bool {
+	return fs.UseXsave() && fs.HasFeature(X86FeatureXSAVEOPT)
+}
+
+// HostID executes a native CPUID instruction.
+func HostID(axArg, cxArg uint32) (ax, bx, cx, dx uint32)
+
+// HostFeatureSet uses cpuid to get host values and construct a feature set
+// that matches that of the host machine. Note that there are several places
+// where there appear to be some unnecessary assignments between register names
+// (ax, bx, cx, or dx) and featureBlockN variables. This is to explicitly show
+// where the different feature blocks come from, to make the code easier to
+// inspect and read.
+func HostFeatureSet() *FeatureSet {
+	// eax=0 gets max supported feature and vendor ID.
+	_, bx, cx, dx := HostID(0, 0)
+	vendorID := vendorIDFromRegs(bx, cx, dx)
+
+	// eax=1 gets basic features in ecx:edx.
+	ax, bx, cx, dx := HostID(1, 0)
+	featureBlock0 := cx
+	featureBlock1 := dx
+	ef, em, pt, f, m, sid := signatureSplit(ax)
+	cacheLine := 8 * (bx >> 8) & 0xff
+
+	// eax=4, ecx=i gets details about cache index i. Only supported on Intel.
+	var caches []Cache
+	if vendorID == intelVendorID {
+		// ecx selects the cache index until a null type is returned.
+		for i := uint32(0); ; i++ {
+			ax, bx, cx, dx := HostID(4, i)
+			t := CacheType(ax & 0xf)
+			if t == cacheNull {
+				break
+			}
+
+			lineSize := (bx & 0xfff) + 1
+			if lineSize != cacheLine {
+				panic(fmt.Sprintf("Mismatched cache line size: %d vs %d", lineSize, cacheLine))
+			}
+
+			caches = append(caches, Cache{
+				Type:                   t,
+				Level:                  (ax >> 5) & 0x7,
+				FullyAssociative:       ((ax >> 9) & 1) == 1,
+				Partitions:             ((bx >> 12) & 0x3ff) + 1,
+				Ways:                   ((bx >> 22) & 0x3ff) + 1,
+				Sets:                   cx + 1,
+				InvalidateHierarchical: (dx & 1) == 0,
+				Inclusive:              ((dx >> 1) & 1) == 1,
+				DirectMapped:           ((dx >> 2) & 1) == 0,
+			})
+		}
+	}
+
+	// eax=7, ecx=0 gets extended features in ecx:ebx.
+	_, bx, cx, _ = HostID(7, 0)
+	featureBlock2 := bx
+	featureBlock3 := cx
+
+	// Leaf 0xd is supported only if CPUID.1:ECX.XSAVE[bit 26] is set.
+	var featureBlock4 uint32
+	if (featureBlock0 & (1 << 26)) != 0 {
+		featureBlock4, _, _, _ = HostID(uint32(xSaveInfo), 1)
+	}
+
+	// eax=0x80000000 gets supported extended levels. We use this to
+	// determine if there are any non-zero block 4 or block 6 bits to find.
+	var featureBlock5, featureBlock6 uint32
+	if ax, _, _, _ := HostID(uint32(extendedFunctionInfo), 0); ax >= uint32(extendedFeatures) {
+		// eax=0x80000001 gets AMD added feature bits.
+		_, _, cx, dx = HostID(uint32(extendedFeatures), 0)
+		featureBlock5 = cx
+		// Ignore features duplicated from block 1 on AMD. These bits
+		// are reserved on Intel.
+		featureBlock6 = dx &^ block6DuplicateMask
+	}
+
+	set := setFromBlockMasks(featureBlock0, featureBlock1, featureBlock2, featureBlock3, featureBlock4, featureBlock5, featureBlock6)
+	return &FeatureSet{
+		Set:            set,
+		VendorID:       vendorID,
+		ExtendedFamily: ef,
+		ExtendedModel:  em,
+		ProcessorType:  pt,
+		Family:         f,
+		Model:          m,
+		SteppingID:     sid,
+		CacheLine:      cacheLine,
+		Caches:         caches,
+	}
+}
+
+// Reads max cpu frequency from host /proc/cpuinfo. Must run before
+// whitelisting. This value is used to create the fake /proc/cpuinfo from a
+// FeatureSet.
+func initCPUFreq() {
+	cpuinfob, err := ioutil.ReadFile("/proc/cpuinfo")
+	if err != nil {
+		// Leave it as 0... The standalone VDSO bails out in the same
+		// way.
+		log.Warningf("Could not read /proc/cpuinfo: %v", err)
+		return
+	}
+	cpuinfo := string(cpuinfob)
+
+	// We get the value straight from host /proc/cpuinfo. On machines with
+	// frequency scaling enabled, this will only get the current value
+	// which will likely be inaccurate. This is fine on machines with
+	// frequency scaling disabled.
+	for _, line := range strings.Split(cpuinfo, "\n") {
+		if strings.Contains(line, "cpu MHz") {
+			splitMHz := strings.Split(line, ":")
+			if len(splitMHz) < 2 {
+				log.Warningf("Could not read /proc/cpuinfo: malformed cpu MHz line")
+				return
+			}
+
+			// If there was a problem, leave cpuFreqMHz as 0.
+			var err error
+			cpuFreqMHz, err = strconv.ParseFloat(strings.TrimSpace(splitMHz[1]), 64)
+			if err != nil {
+				log.Warningf("Could not parse cpu MHz value %v: %v", splitMHz[1], err)
+				cpuFreqMHz = 0
+				return
+			}
+			return
+		}
+	}
+	log.Warningf("Could not parse /proc/cpuinfo, it is empty or does not contain cpu MHz")
+}
+
+func initFeaturesFromString() {
+	for f, s := range x86FeatureStrings {
+		x86FeaturesFromString[s] = f
+	}
+	for f, s := range x86FeatureParseOnlyStrings {
+		x86FeaturesFromString[s] = f
+	}
+}
+
+func init() {
+	// initCpuFreq must be run before whitelists are enabled.
+	initCPUFreq()
+	initFeaturesFromString()
+}