func osStackAlloc(s *mspan) {
	osStackRemap(s, _MAP_STACK)
}

func osStackFree(s *mspan) {
	// Undo MAP_STACK.
	osStackRemap(s, 0)
}

func osStackRemap(s *mspan, flags int32) {
	a, err := mmap(unsafe.Pointer(s.base()), s.npages*pageSize, _PROT_READ|_PROT_WRITE, _MAP_PRIVATE|_MAP_ANON|_MAP_FIXED|flags, -1, 0)
	if err != 0 || uintptr(a) != s.base() {

//sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
//sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)

//sysnb	Gettimeofday(tv *Timeval) (err error)

func setTimespec(sec, nsec int64) Timespec {

//sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
//sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)

type sigset_t struct {
	X__val [16]uint64
}

func setTimeval(sec, usec int64) Timeval {
	return Timeval{Sec: int32(sec), Usec: int32(usec)}
}

//sys	mmap2(addr uintptr, length uintptr, prot int, flags int, fd int, pageOffset uintptr) (xaddr uintptr, err error)

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

	if e != 0 {
		err = e
	}
	return
}

//sys	mmap2(addr uintptr, length uintptr, prot int, flags int, fd int, pageOffset uintptr) (xaddr uintptr, err error)

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

	if err != nil {
		return err
	}
	_, _, e := Syscall(SYS_STATFS64, uintptr(unsafe.Pointer(pathp)), unsafe.Sizeof(*buf), uintptr(unsafe.Pointer(buf)))
	if e != 0 {
		err = e
	}
	return
}

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

//sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
//sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)

//sys	futimesat(dirfd int, path string, times *[2]Timeval) (err error)
//sysnb	Gettimeofday(tv *Timeval) (err error)

	if err != nil {
		return err
	}
	_, _, e := Syscall(SYS_STATFS64, uintptr(unsafe.Pointer(pathp)), unsafe.Sizeof(*buf), uintptr(unsafe.Pointer(buf)))
	if e != 0 {
		err = e
	}
	return
}

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

//sys	Unlink(path string) (err error)
//sys	Unmount(path string, flags int) (err error)
//sys	write(fd int, p []byte) (n int, err error)
//sys	writev(fd int, iovecs []Iovec) (n uintptr, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flag int, fd int, pos int64) (ret uintptr, err error)
//sys	munmap(addr uintptr, length uintptr) (err error)
//sys	getfsstat(stat *Statfs_t, bufsize uintptr, flags int) (n int, err error)

//sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
//sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)

//sysnb	Gettimeofday(tv *Timeval) (err error)

func setTimespec(sec, nsec int64) Timespec {