blob: 986a34135e45c7788702c849da385382afdb5b55 [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.
package runtime
const (
_ARM64_FEATURE_HAS_CRC32 = 0x80
)
var randomNumber uint32
var supportCRC32 bool
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:
supportCRC32 = val&_ARM64_FEATURE_HAS_CRC32 != 0
}
}
//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)
}