blob: 2d6f68bdd9e50eea9c62ce8d3ff7bfd4adf0f647 [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
import "internal/cpu"
var randomNumber uint32
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:
// arm64 doesn't have a 'cpuid' instruction equivalent and relies on
// HWCAP/HWCAP2 bits for hardware capabilities.
hwcap := uint(val)
if GOOS == "android" {
// The Samsung S9+ kernel reports support for atomics, but not all cores
// actually support them, resulting in SIGILL. See issue #28431.
// TODO(elias.naur): Only disable the optimization on bad chipsets.
const hwcap_ATOMICS = 1 << 8
hwcap &= ^uint(hwcap_ATOMICS)
cpu.HWCap = hwcap
case _AT_HWCAP2:
cpu.HWCap2 = uint(val)
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)