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
7package cpu
8
9import (
10	"errors"
11	"io"
12	"os"
13	"strings"
14)
15
16func 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 := string(buf[:n])
29	const features = "\nFeatures	: "
30	i := strings.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 := strings.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 strings.Fields(in) {
48		if p, ok := m[f]; ok {
49			*p = true
50		}
51	}
52	return nil
53}
54