unix: add support for freebsd/arm64

Updates golang/go#24715

DO NOT REVIEW
DO NOT SUBMIT

For now zerrors_freebsd_arm64.go and ztypes_freebsd_arm64.go are just
copie of the freebsd/amd64 version of the files. Regenerate once
bootstrapping a compiler works.

Change-Id: I90a7e3ea0c0b6ecab4033f2908331b7be164a236

unix/asm_freebsd_arm64.s

@@ -0,0 +1,29 @@
+// Copyright 2018 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.
+
+// +build !gccgo
+
+#include "textflag.h"
+
+//
+// System call support for ARM64, FreeBSD
+//
+
+// Just jump to package syscall's implementation for all these functions.
+// The runtime may know about them.
+
+TEXT	·Syscall(SB),NOSPLIT,$0-56
+	JMP	syscall·Syscall(SB)
+
+TEXT	·Syscall6(SB),NOSPLIT,$0-80
+	JMP	syscall·Syscall6(SB)
+
+TEXT	·Syscall9(SB),NOSPLIT,$0-104
+	JMP	syscall·Syscall9(SB)
+
+TEXT ·RawSyscall(SB),NOSPLIT,$0-56
+	JMP	syscall·RawSyscall(SB)
+
+TEXT	·RawSyscall6(SB),NOSPLIT,$0-80
+	JMP	syscall·RawSyscall6(SB)

unix/mkall.sh

@@ -115,6 +115,13 @@ freebsd_arm)
 	# API consistent across platforms.
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs -- -fsigned-char"
 	;;
+freebsd_arm64)
+	mkerrors="$mkerrors"
+	mksysnum="curl -s 'http://svn.freebsd.org/base/stable/11/sys/kern/syscalls.master' | ./mksysnum_freebsd.pl"
+	# Let the type of C char be signed to make the bare syscall
+	# API consistent between platforms.
+	mktypes="GOARCH=$GOARCH go tool cgo -godefs -- -fsigned-char"
+	;;
 linux_sparc64)
 	GOOSARCH_in=syscall_linux_sparc64.go
 	unistd_h=/usr/include/sparc64-linux-gnu/asm/unistd.h

unix/syscall_freebsd_arm64.go

@@ -0,0 +1,52 @@
+// Copyright 2018 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.
+
+// +build arm64,freebsd
+
+package unix
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func setTimespec(sec, nsec int64) Timespec {
+	return Timespec{Sec: sec, Nsec: nsec}
+}
+
+func setTimeval(sec, usec int64) Timeval {
+	return Timeval{Sec: sec, Usec: usec}
+}
+
+func SetKevent(k *Kevent_t, fd, mode, flags int) {
+	k.Ident = uint64(fd)
+	k.Filter = int16(mode)
+	k.Flags = uint16(flags)
+}
+
+func (iov *Iovec) SetLen(length int) {
+	iov.Len = uint64(length)
+}
+
+func (msghdr *Msghdr) SetControllen(length int) {
+	msghdr.Controllen = uint32(length)
+}
+
+func (cmsg *Cmsghdr) SetLen(length int) {
+	cmsg.Len = uint32(length)
+}
+
+func sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
+	var writtenOut uint64 = 0
+	_, _, e1 := Syscall9(SYS_SENDFILE, uintptr(infd), uintptr(outfd), uintptr(*offset), uintptr(count), 0, uintptr(unsafe.Pointer(&writtenOut)), 0, 0, 0)
+
+	written = int(writtenOut)
+
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+func Syscall9(num, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err syscall.Errno)