proto: struct thread *td, struct preadv_args *uap
parms: td, uap
errors:
  - ECONNRESET
  - EFAULT
  - EIO
  - EBUSY
  - EINTR
  - EINVAL
  - EAGAIN
  - EISDIR
  - EOPNOTSUPP
  - EOVERFLOW 
  - EFAULT
  - ESPIPE
profiles:
  - io
