1// Copyright 2020 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 arm64 && darwin && !ios
6
7package cpu
8
9import _ "unsafe" // for linkname
10
11func osInit() {
12	ARM64.HasATOMICS = sysctlEnabled([]byte("hw.optional.armv8_1_atomics\x00"))
13	ARM64.HasCRC32 = sysctlEnabled([]byte("hw.optional.armv8_crc32\x00"))
14	ARM64.HasSHA512 = sysctlEnabled([]byte("hw.optional.armv8_2_sha512\x00"))
15
16	// There are no hw.optional sysctl values for the below features on Mac OS 11.0
17	// to detect their supported state dynamically. Assume the CPU features that
18	// Apple Silicon M1 supports to be available as a minimal set of features
19	// to all Go programs running on darwin/arm64.
20	ARM64.HasAES = true
21	ARM64.HasPMULL = true
22	ARM64.HasSHA1 = true
23	ARM64.HasSHA2 = true
24}
25
26//go:noescape
27func getsysctlbyname(name []byte) (int32, int32)
28
29// sysctlEnabled should be an internal detail,
30// but widely used packages access it using linkname.
31// Notable members of the hall of shame include:
32//   - github.com/bytedance/gopkg
33//   - github.com/songzhibin97/gkit
34//
35// Do not remove or change the type signature.
36// See go.dev/issue/67401.
37//
38//go:linkname sysctlEnabled
39func sysctlEnabled(name []byte) bool {
40	ret, value := getsysctlbyname(name)
41	if ret < 0 {
42		return false
43	}
44	return value > 0
45}
46