podman

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// Copyright (c) 2020 Klaus Post, released under MIT License. See LICENSE file.
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// Copyright 2018 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 located
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// here https://github.com/golang/sys/blob/master/LICENSE
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package cpuid
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import (
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	"encoding/binary"
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	"io/ioutil"
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	"runtime"
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)
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// HWCAP bits.
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const (
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	hwcap_FP       = 1 << 0
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	hwcap_ASIMD    = 1 << 1
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	hwcap_EVTSTRM  = 1 << 2
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	hwcap_AES      = 1 << 3
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	hwcap_PMULL    = 1 << 4
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	hwcap_SHA1     = 1 << 5
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	hwcap_SHA2     = 1 << 6
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	hwcap_CRC32    = 1 << 7
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	hwcap_ATOMICS  = 1 << 8
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	hwcap_FPHP     = 1 << 9
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	hwcap_ASIMDHP  = 1 << 10
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	hwcap_CPUID    = 1 << 11
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	hwcap_ASIMDRDM = 1 << 12
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	hwcap_JSCVT    = 1 << 13
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	hwcap_FCMA     = 1 << 14
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	hwcap_LRCPC    = 1 << 15
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	hwcap_DCPOP    = 1 << 16
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	hwcap_SHA3     = 1 << 17
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	hwcap_SM3      = 1 << 18
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	hwcap_SM4      = 1 << 19
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	hwcap_ASIMDDP  = 1 << 20
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	hwcap_SHA512   = 1 << 21
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	hwcap_SVE      = 1 << 22
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	hwcap_ASIMDFHM = 1 << 23
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)
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func detectOS(c *CPUInfo) bool {
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	// For now assuming no hyperthreading is reasonable.
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	c.LogicalCores = runtime.NumCPU()
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	c.PhysicalCores = c.LogicalCores
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	c.ThreadsPerCore = 1
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	if hwcap == 0 {
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		// We did not get values from the runtime.
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		// Try reading /proc/self/auxv
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		// From https://github.com/golang/sys
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		const (
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			_AT_HWCAP  = 16
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			_AT_HWCAP2 = 26
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			uintSize = int(32 << (^uint(0) >> 63))
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		)
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		buf, err := ioutil.ReadFile("/proc/self/auxv")
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		if err != nil {
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			// e.g. on android /proc/self/auxv is not accessible, so silently
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			// ignore the error and leave Initialized = false. On some
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			// architectures (e.g. arm64) doinit() implements a fallback
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			// readout and will set Initialized = true again.
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			return false
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		}
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		bo := binary.LittleEndian
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		for len(buf) >= 2*(uintSize/8) {
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			var tag, val uint
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			switch uintSize {
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			case 32:
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				tag = uint(bo.Uint32(buf[0:]))
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				val = uint(bo.Uint32(buf[4:]))
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				buf = buf[8:]
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			case 64:
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				tag = uint(bo.Uint64(buf[0:]))
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				val = uint(bo.Uint64(buf[8:]))
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				buf = buf[16:]
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			}
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			switch tag {
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			case _AT_HWCAP:
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				hwcap = val
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			case _AT_HWCAP2:
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				// Not used
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			}
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		}
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		if hwcap == 0 {
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			return false
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		}
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	}
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	// HWCap was populated by the runtime from the auxiliary vector.
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	// Use HWCap information since reading aarch64 system registers
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	// is not supported in user space on older linux kernels.
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	c.featureSet.setIf(isSet(hwcap, hwcap_AES), AESARM)
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	c.featureSet.setIf(isSet(hwcap, hwcap_ASIMD), ASIMD)
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	c.featureSet.setIf(isSet(hwcap, hwcap_ASIMDDP), ASIMDDP)
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	c.featureSet.setIf(isSet(hwcap, hwcap_ASIMDHP), ASIMDHP)
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	c.featureSet.setIf(isSet(hwcap, hwcap_ASIMDRDM), ASIMDRDM)
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	c.featureSet.setIf(isSet(hwcap, hwcap_CPUID), ARMCPUID)
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	c.featureSet.setIf(isSet(hwcap, hwcap_CRC32), CRC32)
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	c.featureSet.setIf(isSet(hwcap, hwcap_DCPOP), DCPOP)
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	c.featureSet.setIf(isSet(hwcap, hwcap_EVTSTRM), EVTSTRM)
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	c.featureSet.setIf(isSet(hwcap, hwcap_FCMA), FCMA)
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	c.featureSet.setIf(isSet(hwcap, hwcap_FP), FP)
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	c.featureSet.setIf(isSet(hwcap, hwcap_FPHP), FPHP)
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	c.featureSet.setIf(isSet(hwcap, hwcap_JSCVT), JSCVT)
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	c.featureSet.setIf(isSet(hwcap, hwcap_LRCPC), LRCPC)
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	c.featureSet.setIf(isSet(hwcap, hwcap_PMULL), PMULL)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SHA1), SHA1)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SHA2), SHA2)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SHA3), SHA3)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SHA512), SHA512)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SM3), SM3)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SM4), SM4)
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	c.featureSet.setIf(isSet(hwcap, hwcap_SVE), SVE)
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	// The Samsung S9+ kernel reports support for atomics, but not all cores
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	// actually support them, resulting in SIGILL. See issue #28431.
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	// TODO(elias.naur): Only disable the optimization on bad chipsets on android.
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	c.featureSet.setIf(isSet(hwcap, hwcap_ATOMICS) && runtime.GOOS != "android", ATOMICS)
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	return true
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}
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func isSet(hwc uint, value uint) bool {
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	return hwc&value != 0
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}
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