unix: update z/OS implementation of fcntl and mmap

- Add a wrapper function around fcntl to handle different operation
  types and new fcntl implementation that accepts uintptr as an arg.
- Add support for calling mmap/munmap with address pointers.
- Add accompanying tests for new functions.

Change-Id: If5e77aa4cf2cccfd431de4f3bd0c5014a761e167
GitHub-Last-Rev: 07e32a4ab797c7baffdb50f8407cf679cabf1dae
GitHub-Pull-Request: golang/sys#216
Reviewed-on: https://go-review.googlesource.com/c/sys/+/610296
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Bypass: Dmitri Shuralyov <dmitshur@golang.org>

unix/syscall_zos_s390x.go

@@ -768,6 +768,16 @@ func Munmap(b []byte) (err error) {
 	return mapper.Munmap(b)
 }
 
+func MmapPtr(fd int, offset int64, addr unsafe.Pointer, length uintptr, prot int, flags int) (ret unsafe.Pointer, err error) {
+	xaddr, err := mapper.mmap(uintptr(addr), length, prot, flags, fd, offset)
+	return unsafe.Pointer(xaddr), err
+}
+
+func MunmapPtr(addr unsafe.Pointer, length uintptr) (err error) {
+	return mapper.munmap(uintptr(addr), length)
+}
+
+
 //sys   Gethostname(buf []byte) (err error) = SYS___GETHOSTNAME_A
 //sysnb	Getgid() (gid int)
 //sysnb	Getpid() (pid int)
@@ -3115,3 +3125,34 @@ func legacy_Mkfifoat(dirfd int, path string, mode uint32) (err error) {
 //sys	Posix_openpt(oflag int) (fd int, err error) = SYS_POSIX_OPENPT
 //sys	Grantpt(fildes int) (rc int, err error) = SYS_GRANTPT
 //sys	Unlockpt(fildes int) (rc int, err error) = SYS_UNLOCKPT
+
+func fcntlAsIs(fd uintptr, cmd int, arg uintptr) (val int, err error) {
+	runtime.EnterSyscall()
+	r0, e2, e1 := CallLeFuncWithErr(GetZosLibVec()+SYS_FCNTL<<4, uintptr(fd), uintptr(cmd), arg)
+	runtime.ExitSyscall()
+	val = int(r0)
+	if int64(r0) == -1 {
+		err = errnoErr2(e1, e2)
+	}
+	return
+}
+
+func Fcntl(fd uintptr, cmd int, op interface{}) (ret int, err error) {
+	switch op.(type) {
+	case *Flock_t:
+		err = FcntlFlock(fd, cmd, op.(*Flock_t))
+		if err != nil {
+                    ret = -1
+		}
+		return
+	case int:
+		return FcntlInt(fd, cmd, op.(int))
+	case *F_cnvrt:
+		return fcntlAsIs(fd, cmd, uintptr(unsafe.Pointer(op.(*F_cnvrt))))
+	case unsafe.Pointer:
+		return fcntlAsIs(fd, cmd, uintptr(op.(unsafe.Pointer)))
+	default:
+		return -1, EINVAL
+	}
+	return
+}