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42c5f3993b
Change-Id: I954b0300554786b7026996a21acfec3b6f205e75 Reviewed-on: https://go-review.googlesource.com/41512 Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com> Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
34 lines
989 B
Go
34 lines
989 B
Go
// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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const (
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_ARM64_FEATURE_HAS_CRC32 = 0x80
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)
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var randomNumber uint32
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var supportCRC32 bool
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func archauxv(tag, val uintptr) {
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switch tag {
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case _AT_RANDOM:
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// sysargs filled in startupRandomData, but that
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// pointer may not be word aligned, so we must treat
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// it as a byte array.
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randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
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uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
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case _AT_HWCAP:
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supportCRC32 = val&_ARM64_FEATURE_HAS_CRC32 != 0
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}
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}
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//go:nosplit
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func cputicks() int64 {
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// Currently cputicks() is used in blocking profiler and to seed fastrand().
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// nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
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// randomNumber provides better seeding of fastrand.
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return nanotime() + int64(randomNumber)
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}
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