cpu: support ARM feature detection on Linux

Updates golang/go#33508

Change-Id: I9ea01090f5b4ac95c1a14881c305461bd4a7b5dd
Reviewed-on: https://go-review.googlesource.com/c/sys/+/190525
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>

cpu/cpu.go

@@ -78,6 +78,42 @@ var ARM64 struct {
 	_           CacheLinePad
 }
 
+// ARM contains the supported CPU features of the current ARM (32-bit) platform.
+// All feature flags are false if:
+//   1. the current platform is not arm, or
+//   2. the current operating system is not Linux.
+var ARM struct {
+	_           CacheLinePad
+	HasSWP      bool // SWP instruction support
+	HasHALF     bool // Half-word load and store support
+	HasTHUMB    bool // ARM Thumb instruction set
+	Has26BIT    bool // Address space limited to 26-bits
+	HasFASTMUL  bool // 32-bit operand, 64-bit result multiplication support
+	HasFPA      bool // Floating point arithmetic support
+	HasVFP      bool // Vector floating point support
+	HasEDSP     bool // DSP Extensions support
+	HasJAVA     bool // Java instruction set
+	HasIWMMXT   bool // Intel Wireless MMX technology support
+	HasCRUNCH   bool // MaverickCrunch context switching and handling
+	HasTHUMBEE  bool // Thumb EE instruction set
+	HasNEON     bool // NEON instruction set
+	HasVFPv3    bool // Vector floating point version 3 support
+	HasVFPv3D16 bool // Vector floating point version 3 D8-D15
+	HasTLS      bool // Thread local storage support
+	HasVFPv4    bool // Vector floating point version 4 support
+	HasIDIVA    bool // Integer divide instruction support in ARM mode
+	HasIDIVT    bool // Integer divide instruction support in Thumb mode
+	HasVFPD32   bool // Vector floating point version 3 D15-D31
+	HasLPAE     bool // Large Physical Address Extensions
+	HasEVTSTRM  bool // Event stream support
+	HasAES      bool // AES hardware implementation
+	HasPMULL    bool // Polynomial multiplication instruction set
+	HasSHA1     bool // SHA1 hardware implementation
+	HasSHA2     bool // SHA2 hardware implementation
+	HasCRC32    bool // CRC32 hardware implementation
+	_           CacheLinePad
+}
+
 // PPC64 contains the supported CPU features of the current ppc64/ppc64le platforms.
 // If the current platform is not ppc64/ppc64le then all feature flags are false.
 //

cpu/cpu_arm.go

@@ -6,4 +6,35 @@ package cpu
 
 const cacheLineSize = 32
 
-func doinit() {}
+// HWCAP/HWCAP2 bits.
+// These are specific to Linux.
+const (
+	hwcap_SWP       = 1 << 0
+	hwcap_HALF      = 1 << 1
+	hwcap_THUMB     = 1 << 2
+	hwcap_26BIT     = 1 << 3
+	hwcap_FAST_MULT = 1 << 4
+	hwcap_FPA       = 1 << 5
+	hwcap_VFP       = 1 << 6
+	hwcap_EDSP      = 1 << 7
+	hwcap_JAVA      = 1 << 8
+	hwcap_IWMMXT    = 1 << 9
+	hwcap_CRUNCH    = 1 << 10
+	hwcap_THUMBEE   = 1 << 11
+	hwcap_NEON      = 1 << 12
+	hwcap_VFPv3     = 1 << 13
+	hwcap_VFPv3D16  = 1 << 14
+	hwcap_TLS       = 1 << 15
+	hwcap_VFPv4     = 1 << 16
+	hwcap_IDIVA     = 1 << 17
+	hwcap_IDIVT     = 1 << 18
+	hwcap_VFPD32    = 1 << 19
+	hwcap_LPAE      = 1 << 20
+	hwcap_EVTSTRM   = 1 << 21
+
+	hwcap2_AES   = 1 << 0
+	hwcap2_PMULL = 1 << 1
+	hwcap2_SHA1  = 1 << 2
+	hwcap2_SHA2  = 1 << 3
+	hwcap2_CRC32 = 1 << 4
+)

cpu/cpu_linux_arm.go

@@ -0,0 +1,39 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cpu
+
+func doinit() {
+	ARM.HasSWP = isSet(hwCap, hwcap_SWP)
+	ARM.HasHALF = isSet(hwCap, hwcap_HALF)
+	ARM.HasTHUMB = isSet(hwCap, hwcap_THUMB)
+	ARM.Has26BIT = isSet(hwCap, hwcap_26BIT)
+	ARM.HasFASTMUL = isSet(hwCap, hwcap_FAST_MULT)
+	ARM.HasFPA = isSet(hwCap, hwcap_FPA)
+	ARM.HasVFP = isSet(hwCap, hwcap_VFP)
+	ARM.HasEDSP = isSet(hwCap, hwcap_EDSP)
+	ARM.HasJAVA = isSet(hwCap, hwcap_JAVA)
+	ARM.HasIWMMXT = isSet(hwCap, hwcap_IWMMXT)
+	ARM.HasCRUNCH = isSet(hwCap, hwcap_CRUNCH)
+	ARM.HasTHUMBEE = isSet(hwCap, hwcap_THUMBEE)
+	ARM.HasNEON = isSet(hwCap, hwcap_NEON)
+	ARM.HasVFPv3 = isSet(hwCap, hwcap_VFPv3)
+	ARM.HasVFPv3D16 = isSet(hwCap, hwcap_VFPv3D16)
+	ARM.HasTLS = isSet(hwCap, hwcap_TLS)
+	ARM.HasVFPv4 = isSet(hwCap, hwcap_VFPv4)
+	ARM.HasIDIVA = isSet(hwCap, hwcap_IDIVA)
+	ARM.HasIDIVT = isSet(hwCap, hwcap_IDIVT)
+	ARM.HasVFPD32 = isSet(hwCap, hwcap_VFPD32)
+	ARM.HasLPAE = isSet(hwCap, hwcap_LPAE)
+	ARM.HasEVTSTRM = isSet(hwCap, hwcap_EVTSTRM)
+	ARM.HasAES = isSet(hwCap2, hwcap2_AES)
+	ARM.HasPMULL = isSet(hwCap2, hwcap2_PMULL)
+	ARM.HasSHA1 = isSet(hwCap2, hwcap2_SHA1)
+	ARM.HasSHA2 = isSet(hwCap2, hwcap2_SHA2)
+	ARM.HasCRC32 = isSet(hwCap2, hwcap2_CRC32)
+}
+
+func isSet(hwc uint, value uint) bool {
+	return hwc&value != 0
+}