PCREAD
*ctlp++ = PCREAD;
case PCREAD: /* read from the address space */
enum uio_rw rw = (cmd == PCREAD)? UIO_READ : UIO_WRITE;
{ PCREAD, sizeof (priovec_t), NULL, NULL },
case PCREAD: /* read from the address space */
{ PCREAD, sizeof (priovec32_t), NULL, NULL },