kern_pipe
error = kern_pipe(td, fildes, 0, NULL, NULL);
error = kern_pipe(td, fildes, flags, NULL, NULL);
error = kern_pipe(td, fildes, 0, NULL, NULL);
error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
int kern_pipe(struct thread *td, int fildes[2], int flags,