cpu_openbsd_arm64.go

     1  // Copyright 2022 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  package cpu
     6  
     7  import (
     8  	"syscall"
     9  	"unsafe"
    10  )
    11  
    12  // Minimal copy of functionality from x/sys/unix so the cpu package can call
    13  // sysctl without depending on x/sys/unix.
    14  
    15  const (
    16  	// From OpenBSD's sys/sysctl.h.
    17  	_CTL_MACHDEP = 7
    18  
    19  	// From OpenBSD's machine/cpu.h.
    20  	_CPU_ID_AA64ISAR0 = 2
    21  	_CPU_ID_AA64ISAR1 = 3
    22  )
    23  
    24  // Implemented in the runtime package (runtime/sys_openbsd3.go)
    25  func syscall_syscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err syscall.Errno)
    26  
    27  //go:linkname syscall_syscall6 syscall.syscall6
    28  
    29  func sysctl(mib []uint32, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err error) {
    30  	_, _, 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))
    31  	if errno != 0 {
    32  		return errno
    33  	}
    34  	return nil
    35  }
    36  
    37  var libc_sysctl_trampoline_addr uintptr
    38  
    39  //go:cgo_import_dynamic libc_sysctl sysctl "libc.so"
    40  
    41  func sysctlUint64(mib []uint32) (uint64, bool) {
    42  	var out uint64
    43  	nout := unsafe.Sizeof(out)
    44  	if err := sysctl(mib, (*byte)(unsafe.Pointer(&out)), &nout, nil, 0); err != nil {
    45  		return 0, false
    46  	}
    47  	return out, true
    48  }
    49  
    50  func doinit() {
    51  	setMinimalFeatures()
    52  
    53  	// Get ID_AA64ISAR0 and ID_AA64ISAR1 from sysctl.
    54  	isar0, ok := sysctlUint64([]uint32{_CTL_MACHDEP, _CPU_ID_AA64ISAR0})
    55  	if !ok {
    56  		return
    57  	}
    58  	isar1, ok := sysctlUint64([]uint32{_CTL_MACHDEP, _CPU_ID_AA64ISAR1})
    59  	if !ok {
    60  		return
    61  	}
    62  	parseARM64SystemRegisters(isar0, isar1, 0)
    63  
    64  	Initialized = true
    65  }
    66
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