internal/cpu: add ARM64.HasSHA3

For #69536

Change-Id: If237226ba03e282443b4fc90484968c903198cb1
Reviewed-on: https://go-review.googlesource.com/c/go/+/616715
Reviewed-by: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>

src/internal/cpu/cpu.go

@@ -70,6 +70,7 @@ var ARM64 struct {
 	HasSHA1    bool
 	HasSHA2    bool
 	HasSHA512  bool
+	HasSHA3    bool
 	HasCRC32   bool
 	HasATOMICS bool
 	HasCPUID   bool

src/internal/cpu/cpu_arm64.go

@@ -16,6 +16,7 @@ func doinit() {
 		{Name: "sha1", Feature: &ARM64.HasSHA1},
 		{Name: "sha2", Feature: &ARM64.HasSHA2},
 		{Name: "sha512", Feature: &ARM64.HasSHA512},
+		{Name: "sha3", Feature: &ARM64.HasSHA3},
 		{Name: "crc32", Feature: &ARM64.HasCRC32},
 		{Name: "atomics", Feature: &ARM64.HasATOMICS},
 		{Name: "cpuid", Feature: &ARM64.HasCPUID},
@@ -38,6 +39,7 @@ func extractBits(data uint64, start, end uint) uint {
 
 func parseARM64SystemRegisters(isar0, pfr0 uint64) {
 	// ID_AA64ISAR0_EL1
+	// https://developer.arm.com/documentation/ddi0601/2025-03/AArch64-Registers/ID-AA64ISAR0-EL1--AArch64-Instruction-Set-Attribute-Register-0
 	switch extractBits(isar0, 4, 7) {
 	case 1:
 		ARM64.HasAES = true
@@ -69,6 +71,11 @@ func parseARM64SystemRegisters(isar0, pfr0 uint64) {
 		ARM64.HasATOMICS = true
 	}
 
+	switch extractBits(isar0, 32, 35) {
+	case 1:
+		ARM64.HasSHA3 = true
+	}
+
 	switch extractBits(pfr0, 48, 51) {
 	case 1:
 		ARM64.HasDIT = true

src/internal/cpu/cpu_arm64_darwin.go

@@ -9,15 +9,21 @@ package cpu
 import _ "unsafe" // for linkname
 
 func osInit() {
+	// macOS 12 moved these to the hw.optional.arm tree, but as of Go 1.24 we
+	// still support macOS 11. See [Determine Encryption Capabilities].
+	//
+	// [Determine Encryption Capabilities]: https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics#3918855
 	ARM64.HasATOMICS = sysctlEnabled([]byte("hw.optional.armv8_1_atomics\x00"))
 	ARM64.HasCRC32 = sysctlEnabled([]byte("hw.optional.armv8_crc32\x00"))
 	ARM64.HasSHA512 = sysctlEnabled([]byte("hw.optional.armv8_2_sha512\x00"))
+	ARM64.HasSHA3 = sysctlEnabled([]byte("hw.optional.armv8_2_sha3\x00"))
+
 	ARM64.HasDIT = sysctlEnabled([]byte("hw.optional.arm.FEAT_DIT\x00"))
 
-	// There are no hw.optional sysctl values for the below features on Mac OS 11.0
-	// to detect their supported state dynamically. Assume the CPU features that
-	// Apple Silicon M1 supports to be available as a minimal set of features
-	// to all Go programs running on darwin/arm64.
+	// There are no hw.optional sysctl values for the below features on macOS 11
+	// to detect their supported state dynamically (although they are available
+	// in the hw.optional.arm tree on macOS 12). Assume the CPU features that
+	// Apple Silicon M1 supports to be available on all future iterations.
 	ARM64.HasAES = true
 	ARM64.HasPMULL = true
 	ARM64.HasSHA1 = true

src/internal/cpu/cpu_arm64_hwcap.go

@@ -22,6 +22,7 @@ import _ "unsafe" // for linkname
 var HWCap uint
 
 // HWCAP bits. These are exposed by Linux.
+// See arch/arm64/include/uapi/asm/hwcap.h.
 const (
 	hwcap_AES     = 1 << 3
 	hwcap_PMULL   = 1 << 4
@@ -30,18 +31,21 @@ const (
 	hwcap_CRC32   = 1 << 7
 	hwcap_ATOMICS = 1 << 8
 	hwcap_CPUID   = 1 << 11
+	hwcap_SHA3    = 1 << 17
 	hwcap_SHA512  = 1 << 21
 	hwcap_DIT     = 1 << 24
 )
 
 func hwcapInit(os string) {
 	// HWCap was populated by the runtime from the auxiliary vector.
+	// See https://docs.kernel.org/arch/arm64/elf_hwcaps.html.
 	// Use HWCap information since reading aarch64 system registers
 	// is not supported in user space on older linux kernels.
 	ARM64.HasAES = isSet(HWCap, hwcap_AES)
 	ARM64.HasPMULL = isSet(HWCap, hwcap_PMULL)
 	ARM64.HasSHA1 = isSet(HWCap, hwcap_SHA1)
 	ARM64.HasSHA2 = isSet(HWCap, hwcap_SHA2)
+	ARM64.HasSHA3 = isSet(HWCap, hwcap_SHA3)
 	ARM64.HasCRC32 = isSet(HWCap, hwcap_CRC32)
 	ARM64.HasCPUID = isSet(HWCap, hwcap_CPUID)
 	ARM64.HasSHA512 = isSet(HWCap, hwcap_SHA512)