blob: 28a0319f10736cb9c55152770842aa525174fd41 [file] [log] [blame]
// Copyright 2015 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 arm64
package runtime
// For go:linkname
import _ "unsafe"
var randomNumber uint32
// arm64 doesn't have a 'cpuid' instruction equivalent and relies on
// HWCAP/HWCAP2 bits for hardware capabilities.
//go:linkname cpu_hwcap internal/cpu.hwcap
var cpu_hwcap uint
//go:linkname cpu_hwcap2 internal/cpu.hwcap2
var cpu_hwcap2 uint
func archauxv(tag, val uintptr) {
switch tag {
case _AT_RANDOM:
// sysargs filled in startupRandomData, but that
// pointer may not be word aligned, so we must treat
// it as a byte array.
randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
case _AT_HWCAP:
cpu_hwcap = uint(val)
case _AT_HWCAP2:
cpu_hwcap2 = uint(val)
}
}
//go:nosplit
func cputicks() int64 {
// Currently cputicks() is used in blocking profiler and to seed fastrand().
// nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
// randomNumber provides better seeding of fastrand.
return nanotime() + int64(randomNumber)
}