1// Copyright 2018 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
5package cpu
6
7import (
8	"strings"
9	"syscall"
10)
11
12// HWCAP/HWCAP2 bits. These are exposed by Linux.
13const (
14	hwcap_FP       = 1 << 0
15	hwcap_ASIMD    = 1 << 1
16	hwcap_EVTSTRM  = 1 << 2
17	hwcap_AES      = 1 << 3
18	hwcap_PMULL    = 1 << 4
19	hwcap_SHA1     = 1 << 5
20	hwcap_SHA2     = 1 << 6
21	hwcap_CRC32    = 1 << 7
22	hwcap_ATOMICS  = 1 << 8
23	hwcap_FPHP     = 1 << 9
24	hwcap_ASIMDHP  = 1 << 10
25	hwcap_CPUID    = 1 << 11
26	hwcap_ASIMDRDM = 1 << 12
27	hwcap_JSCVT    = 1 << 13
28	hwcap_FCMA     = 1 << 14
29	hwcap_LRCPC    = 1 << 15
30	hwcap_DCPOP    = 1 << 16
31	hwcap_SHA3     = 1 << 17
32	hwcap_SM3      = 1 << 18
33	hwcap_SM4      = 1 << 19
34	hwcap_ASIMDDP  = 1 << 20
35	hwcap_SHA512   = 1 << 21
36	hwcap_SVE      = 1 << 22
37	hwcap_ASIMDFHM = 1 << 23
38
39	hwcap2_SVE2 = 1 << 1
40)
41
42// linuxKernelCanEmulateCPUID reports whether we're running
43// on Linux 4.11+. Ideally we'd like to ask the question about
44// whether the current kernel contains
45// https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=77c97b4ee21290f5f083173d957843b615abbff2
46// but the version number will have to do.
47func linuxKernelCanEmulateCPUID() bool {
48	var un syscall.Utsname
49	syscall.Uname(&un)
50	var sb strings.Builder
51	for _, b := range un.Release[:] {
52		if b == 0 {
53			break
54		}
55		sb.WriteByte(byte(b))
56	}
57	major, minor, _, ok := parseRelease(sb.String())
58	return ok && (major > 4 || major == 4 && minor >= 11)
59}
60
61func doinit() {
62	if err := readHWCAP(); err != nil {
63		// We failed to read /proc/self/auxv. This can happen if the binary has
64		// been given extra capabilities(7) with /bin/setcap.
65		//
66		// When this happens, we have two options. If the Linux kernel is new
67		// enough (4.11+), we can read the arm64 registers directly which'll
68		// trap into the kernel and then return back to userspace.
69		//
70		// But on older kernels, such as Linux 4.4.180 as used on many Synology
71		// devices, calling readARM64Registers (specifically getisar0) will
72		// cause a SIGILL and we'll die. So for older kernels, parse /proc/cpuinfo
73		// instead.
74		//
75		// See golang/go#57336.
76		if linuxKernelCanEmulateCPUID() {
77			readARM64Registers()
78		} else {
79			readLinuxProcCPUInfo()
80		}
81		return
82	}
83
84	// HWCAP feature bits
85	ARM64.HasFP = isSet(hwCap, hwcap_FP)
86	ARM64.HasASIMD = isSet(hwCap, hwcap_ASIMD)
87	ARM64.HasEVTSTRM = isSet(hwCap, hwcap_EVTSTRM)
88	ARM64.HasAES = isSet(hwCap, hwcap_AES)
89	ARM64.HasPMULL = isSet(hwCap, hwcap_PMULL)
90	ARM64.HasSHA1 = isSet(hwCap, hwcap_SHA1)
91	ARM64.HasSHA2 = isSet(hwCap, hwcap_SHA2)
92	ARM64.HasCRC32 = isSet(hwCap, hwcap_CRC32)
93	ARM64.HasATOMICS = isSet(hwCap, hwcap_ATOMICS)
94	ARM64.HasFPHP = isSet(hwCap, hwcap_FPHP)
95	ARM64.HasASIMDHP = isSet(hwCap, hwcap_ASIMDHP)
96	ARM64.HasCPUID = isSet(hwCap, hwcap_CPUID)
97	ARM64.HasASIMDRDM = isSet(hwCap, hwcap_ASIMDRDM)
98	ARM64.HasJSCVT = isSet(hwCap, hwcap_JSCVT)
99	ARM64.HasFCMA = isSet(hwCap, hwcap_FCMA)
100	ARM64.HasLRCPC = isSet(hwCap, hwcap_LRCPC)
101	ARM64.HasDCPOP = isSet(hwCap, hwcap_DCPOP)
102	ARM64.HasSHA3 = isSet(hwCap, hwcap_SHA3)
103	ARM64.HasSM3 = isSet(hwCap, hwcap_SM3)
104	ARM64.HasSM4 = isSet(hwCap, hwcap_SM4)
105	ARM64.HasASIMDDP = isSet(hwCap, hwcap_ASIMDDP)
106	ARM64.HasSHA512 = isSet(hwCap, hwcap_SHA512)
107	ARM64.HasSVE = isSet(hwCap, hwcap_SVE)
108	ARM64.HasASIMDFHM = isSet(hwCap, hwcap_ASIMDFHM)
109
110	// HWCAP2 feature bits
111	ARM64.HasSVE2 = isSet(hwCap2, hwcap2_SVE2)
112}
113
114func isSet(hwc uint, value uint) bool {
115	return hwc&value != 0
116}
117