cpu_linux_arm64.go

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package cpu
     6  
     7  import (
     8  	"strings"
     9  	"syscall"
    10  )
    11  
    12  // HWCAP/HWCAP2 bits. These are exposed by Linux.
    13  const (
    14  	hwcap_FP       = 1 << 0
    15  	hwcap_ASIMD    = 1 << 1
    16  	hwcap_EVTSTRM  = 1 << 2
    17  	hwcap_AES      = 1 << 3
    18  	hwcap_PMULL    = 1 << 4
    19  	hwcap_SHA1     = 1 << 5
    20  	hwcap_SHA2     = 1 << 6
    21  	hwcap_CRC32    = 1 << 7
    22  	hwcap_ATOMICS  = 1 << 8
    23  	hwcap_FPHP     = 1 << 9
    24  	hwcap_ASIMDHP  = 1 << 10
    25  	hwcap_CPUID    = 1 << 11
    26  	hwcap_ASIMDRDM = 1 << 12
    27  	hwcap_JSCVT    = 1 << 13
    28  	hwcap_FCMA     = 1 << 14
    29  	hwcap_LRCPC    = 1 << 15
    30  	hwcap_DCPOP    = 1 << 16
    31  	hwcap_SHA3     = 1 << 17
    32  	hwcap_SM3      = 1 << 18
    33  	hwcap_SM4      = 1 << 19
    34  	hwcap_ASIMDDP  = 1 << 20
    35  	hwcap_SHA512   = 1 << 21
    36  	hwcap_SVE      = 1 << 22
    37  	hwcap_ASIMDFHM = 1 << 23
    38  
    39  	hwcap2_SVE2 = 1 << 1
    40  )
    41  
    42  // linuxKernelCanEmulateCPUID reports whether we're running
    43  // on Linux 4.11+. Ideally we'd like to ask the question about
    44  // whether the current kernel contains
    45  // https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=77c97b4ee21290f5f083173d957843b615abbff2
    46  // but the version number will have to do.
    47  func linuxKernelCanEmulateCPUID() bool {
    48  	var un syscall.Utsname
    49  	syscall.Uname(&un)
    50  	var sb strings.Builder
    51  	for _, b := range un.Release[:] {
    52  		if b == 0 {
    53  			break
    54  		}
    55  		sb.WriteByte(byte(b))
    56  	}
    57  	major, minor, _, ok := parseRelease(sb.String())
    58  	return ok && (major > 4 || major == 4 && minor >= 11)
    59  }
    60  
    61  func doinit() {
    62  	if err := readHWCAP(); err != nil {
    63  		// We failed to read /proc/self/auxv. This can happen if the binary has
    64  		// been given extra capabilities(7) with /bin/setcap.
    65  		//
    66  		// When this happens, we have two options. If the Linux kernel is new
    67  		// enough (4.11+), we can read the arm64 registers directly which'll
    68  		// trap into the kernel and then return back to userspace.
    69  		//
    70  		// But on older kernels, such as Linux 4.4.180 as used on many Synology
    71  		// devices, calling readARM64Registers (specifically getisar0) will
    72  		// cause a SIGILL and we'll die. So for older kernels, parse /proc/cpuinfo
    73  		// instead.
    74  		//
    75  		// See golang/go#57336.
    76  		if linuxKernelCanEmulateCPUID() {
    77  			readARM64Registers()
    78  		} else {
    79  			readLinuxProcCPUInfo()
    80  		}
    81  		return
    82  	}
    83  
    84  	// HWCAP feature bits
    85  	ARM64.HasFP = isSet(hwCap, hwcap_FP)
    86  	ARM64.HasASIMD = isSet(hwCap, hwcap_ASIMD)
    87  	ARM64.HasEVTSTRM = isSet(hwCap, hwcap_EVTSTRM)
    88  	ARM64.HasAES = isSet(hwCap, hwcap_AES)
    89  	ARM64.HasPMULL = isSet(hwCap, hwcap_PMULL)
    90  	ARM64.HasSHA1 = isSet(hwCap, hwcap_SHA1)
    91  	ARM64.HasSHA2 = isSet(hwCap, hwcap_SHA2)
    92  	ARM64.HasCRC32 = isSet(hwCap, hwcap_CRC32)
    93  	ARM64.HasATOMICS = isSet(hwCap, hwcap_ATOMICS)
    94  	ARM64.HasFPHP = isSet(hwCap, hwcap_FPHP)
    95  	ARM64.HasASIMDHP = isSet(hwCap, hwcap_ASIMDHP)
    96  	ARM64.HasCPUID = isSet(hwCap, hwcap_CPUID)
    97  	ARM64.HasASIMDRDM = isSet(hwCap, hwcap_ASIMDRDM)
    98  	ARM64.HasJSCVT = isSet(hwCap, hwcap_JSCVT)
    99  	ARM64.HasFCMA = isSet(hwCap, hwcap_FCMA)
   100  	ARM64.HasLRCPC = isSet(hwCap, hwcap_LRCPC)
   101  	ARM64.HasDCPOP = isSet(hwCap, hwcap_DCPOP)
   102  	ARM64.HasSHA3 = isSet(hwCap, hwcap_SHA3)
   103  	ARM64.HasSM3 = isSet(hwCap, hwcap_SM3)
   104  	ARM64.HasSM4 = isSet(hwCap, hwcap_SM4)
   105  	ARM64.HasASIMDDP = isSet(hwCap, hwcap_ASIMDDP)
   106  	ARM64.HasSHA512 = isSet(hwCap, hwcap_SHA512)
   107  	ARM64.HasSVE = isSet(hwCap, hwcap_SVE)
   108  	ARM64.HasASIMDFHM = isSet(hwCap, hwcap_ASIMDFHM)
   109  
   110  	// HWCAP2 feature bits
   111  	ARM64.HasSVE2 = isSet(hwCap2, hwcap2_SVE2)
   112  }
   113  
   114  func isSet(hwc uint, value uint) bool {
   115  	return hwc&value != 0
   116  }
   117
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