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d46980995b
Go runtime currently only populates hwcap for ppc64 and arm64. While the interpretation of hwcap is platform specific the hwcap information is generally available on linux. Changing the runtime variable name to cpu_hwcap for cpu.hwcap makes it consistent with the general naming of runtime variables that are linked to other packages. Change-Id: I1e1f932a73ed624a219b9298faafbb6355e47ada Reviewed-on: https://go-review.googlesource.com/94757 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Martin Möhrmann <moehrmann@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org>
45 lines
1.2 KiB
Go
45 lines
1.2 KiB
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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// +build arm64
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package runtime
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// For go:linkname
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import _ "unsafe"
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var randomNumber uint32
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// arm64 doesn't have a 'cpuid' instruction equivalent and relies on
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// HWCAP/HWCAP2 bits for hardware capabilities.
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//go:linkname cpu_hwcap internal/cpu.hwcap
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var cpu_hwcap uint
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//go:linkname cpu_hwcap2 internal/cpu.hwcap2
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var cpu_hwcap2 uint
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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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cpu_hwcap = uint(val)
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case _AT_HWCAP2:
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cpu_hwcap2 = uint(val)
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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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