1 // Copyright 2022 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 //go:build linux && arm64
6 7 package cpu
8 9 import (
10 "errors"
11 "io"
12 "os"
13 "bytes"
14 )
15 16 func readLinuxProcCPUInfo() error {
17 f, err := os.Open("/proc/cpuinfo")
18 if err != nil {
19 return err
20 }
21 defer f.Close()
22 23 var buf [1 << 10]byte // enough for first CPU
24 n, err := io.ReadFull(f, buf[:])
25 if err != nil && err != io.ErrUnexpectedEOF {
26 return err
27 }
28 in := []byte(buf[:n])
29 const features = "\nFeatures : "
30 i := bytes.Index(in, features)
31 if i == -1 {
32 return errors.New("no CPU features found")
33 }
34 in = in[i+len(features):]
35 if i := bytes.Index(in, "\n"); i != -1 {
36 in = in[:i]
37 }
38 m := map[string]*bool{}
39 40 initOptions() // need it early here; it's harmless to call twice
41 for _, o := range options {
42 m[o.Name] = o.Feature
43 }
44 // The EVTSTRM field has alias "evstrm" in Go, but Linux calls it "evtstrm".
45 m["evtstrm"] = &ARM64.HasEVTSTRM
46 47 for _, f := range bytes.Fields(in) {
48 if p, ok := m[f]; ok {
49 *p = true
50 }
51 }
52 return nil
53 }
54