cpu: implement CPU feature detection for openbsd/arm64
OpenBSD 7.1 onwards expose the aarch64 ISAR0 and ISAR1 registers via sysctl:
$ sysctl machdep
machdep.compatible=apple,j274
machdep.id_aa64isar0=153421459058925856
machdep.id_aa64isar1=1172796674562
Implement CPU feature detection for openbsd/arm64 based on this information.
Updates golang/go#31746
Change-Id: I6dc473d93ccff720582c05b75456de51269bc3e5
Reviewed-on: https://go-review.googlesource.com/c/sys/+/421799
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
diff --git a/cpu/cpu_arm64.go b/cpu/cpu_arm64.go
index 87dd5e3..bbaba18 100644
--- a/cpu/cpu_arm64.go
+++ b/cpu/cpu_arm64.go
@@ -41,13 +41,10 @@
switch runtime.GOOS {
case "freebsd":
readARM64Registers()
- case "linux", "netbsd":
+ case "linux", "netbsd", "openbsd":
doinit()
default:
- // Most platforms don't seem to allow reading these registers.
- //
- // OpenBSD:
- // See https://golang.org/issue/31746
+ // Many platforms don't seem to allow reading these registers.
setMinimalFeatures()
}
}
diff --git a/cpu/cpu_openbsd_arm64.go b/cpu/cpu_openbsd_arm64.go
new file mode 100644
index 0000000..85b64d5
--- /dev/null
+++ b/cpu/cpu_openbsd_arm64.go
@@ -0,0 +1,65 @@
+// Copyright 2022 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
+
+import (
+ "syscall"
+ "unsafe"
+)
+
+// Minimal copy of functionality from x/sys/unix so the cpu package can call
+// sysctl without depending on x/sys/unix.
+
+const (
+ // From OpenBSD's sys/sysctl.h.
+ _CTL_MACHDEP = 7
+
+ // From OpenBSD's machine/cpu.h.
+ _CPU_ID_AA64ISAR0 = 2
+ _CPU_ID_AA64ISAR1 = 3
+)
+
+// Implemented in the runtime package (runtime/sys_openbsd3.go)
+func syscall_syscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err syscall.Errno)
+
+//go:linkname syscall_syscall6 syscall.syscall6
+
+func sysctl(mib []uint32, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err error) {
+ _, _, errno := syscall_syscall6(libc_sysctl_trampoline_addr, uintptr(unsafe.Pointer(&mib[0])), uintptr(len(mib)), uintptr(unsafe.Pointer(old)), uintptr(unsafe.Pointer(oldlen)), uintptr(unsafe.Pointer(new)), uintptr(newlen))
+ if errno != 0 {
+ return errno
+ }
+ return nil
+}
+
+var libc_sysctl_trampoline_addr uintptr
+
+//go:cgo_import_dynamic libc_sysctl sysctl "libc.so"
+
+func sysctlUint64(mib []uint32) (uint64, bool) {
+ var out uint64
+ nout := unsafe.Sizeof(out)
+ if err := sysctl(mib, (*byte)(unsafe.Pointer(&out)), &nout, nil, 0); err != nil {
+ return 0, false
+ }
+ return out, true
+}
+
+func doinit() {
+ setMinimalFeatures()
+
+ // Get ID_AA64ISAR0 and ID_AA64ISAR1 from sysctl.
+ isar0, ok := sysctlUint64([]uint32{_CTL_MACHDEP, _CPU_ID_AA64ISAR0})
+ if !ok {
+ return
+ }
+ isar1, ok := sysctlUint64([]uint32{_CTL_MACHDEP, _CPU_ID_AA64ISAR1})
+ if !ok {
+ return
+ }
+ parseARM64SystemRegisters(isar0, isar1, 0)
+
+ Initialized = true
+}
diff --git a/cpu/cpu_openbsd_arm64.s b/cpu/cpu_openbsd_arm64.s
new file mode 100644
index 0000000..054ba05
--- /dev/null
+++ b/cpu/cpu_openbsd_arm64.s
@@ -0,0 +1,11 @@
+// Copyright 2022 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.
+
+#include "textflag.h"
+
+TEXT libc_sysctl_trampoline<>(SB),NOSPLIT,$0-0
+ JMP libc_sysctl(SB)
+
+GLOBL ·libc_sysctl_trampoline_addr(SB), RODATA, $8
+DATA ·libc_sysctl_trampoline_addr(SB)/8, $libc_sysctl_trampoline<>(SB)
diff --git a/cpu/cpu_other_arm64.go b/cpu/cpu_other_arm64.go
index f8c484f..f3cde12 100644
--- a/cpu/cpu_other_arm64.go
+++ b/cpu/cpu_other_arm64.go
@@ -2,8 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-//go:build !linux && !netbsd && arm64
-// +build !linux,!netbsd,arm64
+//go:build !linux && !netbsd && !openbsd && arm64
+// +build !linux,!netbsd,!openbsd,arm64
package cpu
