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path: root/vendor/golang.org/x/sys/cpu/cpu_linux.go
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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//+build !amd64,!amd64p32,!386

package cpu

import (
    "encoding/binary"
    "io/ioutil"
    "runtime"
)

const (
    _AT_HWCAP  = 16
    _AT_HWCAP2 = 26

    procAuxv = "/proc/self/auxv"

    uintSize uint = 32 << (^uint(0) >> 63)
)

// For those platforms don't have a 'cpuid' equivalent we use HWCAP/HWCAP2
// These are initialized in cpu_$GOARCH.go
// and should not be changed after they are initialized.
var HWCap uint
var HWCap2 uint

func init() {
    buf, err := ioutil.ReadFile(procAuxv)
    if err != nil {
        panic("read proc auxv failed: " + err.Error())
    }

    pb := int(uintSize / 8)

    for i := 0; i < len(buf)-pb*2; i += pb * 2 {
        var tag, val uint
        switch uintSize {
        case 32:
            tag = uint(binary.LittleEndian.Uint32(buf[i:]))
            val = uint(binary.LittleEndian.Uint32(buf[i+pb:]))
        case 64:
            if runtime.GOARCH == "ppc64" {
                tag = uint(binary.BigEndian.Uint64(buf[i:]))
                val = uint(binary.BigEndian.Uint64(buf[i+pb:]))
            } else {
                tag = uint(binary.LittleEndian.Uint64(buf[i:]))
                val = uint(binary.LittleEndian.Uint64(buf[i+pb:]))
            }
        }
        switch tag {
        case _AT_HWCAP:
            HWCap = val
        case _AT_HWCAP2:
            HWCap2 = val
        }
    }
    doinit()
}