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56 lines
1.2 KiB
56 lines
1.2 KiB
// Copyright 2019 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 cpu |
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import ( |
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"io/ioutil" |
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) |
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const ( |
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_AT_HWCAP = 16 |
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_AT_HWCAP2 = 26 |
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procAuxv = "/proc/self/auxv" |
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uintSize = int(32 << (^uint(0) >> 63)) |
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) |
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// For those platforms don't have a 'cpuid' equivalent we use HWCAP/HWCAP2 |
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// These are initialized in cpu_$GOARCH.go |
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// and should not be changed after they are initialized. |
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var hwCap uint |
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var hwCap2 uint |
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func readHWCAP() error { |
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buf, err := ioutil.ReadFile(procAuxv) |
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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 err |
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} |
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bo := hostByteOrder() |
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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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hwCap2 = val |
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} |
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} |
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return nil |
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}
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