xref: /src/sys/kern/tty_pty.c

/*	$NetBSD: tty_pty.c,v 1.92 2006/08/03 22:03:18 christos Exp $	*/

/*
 * Copyright (c) 1982, 1986, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)tty_pty.c	8.4 (Berkeley) 2/20/95
 */

/*
 * Pseudo-teletype Driver
 * (Actually two drivers, requiring two entries in 'cdevsw')
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tty_pty.c,v 1.92 2006/08/03 22:03:18 christos Exp $");

#include "opt_compat_sunos.h"
#include "opt_ptm.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/proc.h>
#include <sys/tty.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/uio.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/signalvar.h>
#include <sys/uio.h>
#include <sys/filedesc.h>
#include <sys/conf.h>
#include <sys/poll.h>
#include <sys/malloc.h>
#include <sys/pty.h>
#include <sys/kauth.h>

#define	DEFAULT_NPTYS		16	/* default number of initial ptys */
#define DEFAULT_MAXPTYS		992	/* default maximum number of ptys */

#define BUFSIZ 100		/* Chunk size iomoved to/from user */

struct	pt_softc {
	struct	tty *pt_tty;
	int	pt_flags;
	struct	selinfo pt_selr, pt_selw;
	u_char	pt_send;
	u_char	pt_ucntl;
};

static struct pt_softc **pt_softc = NULL;	/* pty array */
static int maxptys = DEFAULT_MAXPTYS;	/* maximum number of ptys (sysctable) */
struct simplelock pt_softc_mutex = SIMPLELOCK_INITIALIZER;
int npty = 0;			/* for pstat -t */

#define	PF_PKT		0x08		/* packet mode */
#define	PF_STOPPED	0x10		/* user told stopped */
#define	PF_REMOTE	0x20		/* remote and flow controlled input */
#define	PF_NOSTOP	0x40
#define PF_UCNTL	0x80		/* user control mode */

void	ptyattach(int);
void	ptcwakeup(struct tty *, int);
void	ptsstart(struct tty *);
int	pty_maxptys(int, int);

static struct pt_softc **ptyarralloc(int);

dev_type_open(ptcopen);
dev_type_close(ptcclose);
dev_type_read(ptcread);
dev_type_write(ptcwrite);
dev_type_poll(ptcpoll);
dev_type_kqfilter(ptckqfilter);

dev_type_open(ptsopen);
dev_type_close(ptsclose);
dev_type_read(ptsread);
dev_type_write(ptswrite);
dev_type_stop(ptsstop);
dev_type_poll(ptspoll);

dev_type_ioctl(ptyioctl);
dev_type_tty(ptytty);

const struct cdevsw ptc_cdevsw = {
	ptcopen, ptcclose, ptcread, ptcwrite, ptyioctl,
	nullstop, ptytty, ptcpoll, nommap, ptckqfilter, D_TTY
};

const struct cdevsw pts_cdevsw = {
	ptsopen, ptsclose, ptsread, ptswrite, ptyioctl,
	ptsstop, ptytty, ptspoll, nommap, ttykqfilter, D_TTY
};

#if defined(pmax)
const struct cdevsw ptc_ultrix_cdevsw = {
	ptcopen, ptcclose, ptcread, ptcwrite, ptyioctl,
	nullstop, ptytty, ptcpoll, nommap, ptckqfilter, D_TTY
};

const struct cdevsw pts_ultrix_cdevsw = {
	ptsopen, ptsclose, ptsread, ptswrite, ptyioctl,
	ptsstop, ptytty, ptspoll, nommap, ttykqfilter, D_TTY
};
#endif /* defined(pmax) */

/*
 * Check if a pty is free to use.
 */
int
pty_isfree(int minor, int lock)
{
	struct pt_softc *pt = pt_softc[minor];
	if (lock)
		simple_lock(&pt_softc_mutex);
	minor = pt == NULL || pt->pt_tty == NULL ||
	    pt->pt_tty->t_oproc == NULL;
	if (lock)
		simple_unlock(&pt_softc_mutex);
	return minor;
}

/*
 * Allocate and zero array of nelem elements.
 */
static struct pt_softc **
ptyarralloc(nelem)
	int nelem;
{
	struct pt_softc **pt;
	nelem += 10;
	pt = malloc(nelem * sizeof *pt, M_DEVBUF, M_WAITOK | M_ZERO);
	return pt;
}

/*
 * Check if the minor is correct and ensure necessary structures
 * are properly allocated.
 */
int
pty_check(int ptn)
{
	struct pt_softc *pti;

	if (ptn >= npty) {
		struct pt_softc **newpt, **oldpt;
		int newnpty;

		/* check if the requested pty can be granted */
		if (ptn >= maxptys) {
	    limit_reached:
			tablefull("pty", "increase kern.maxptys");
			return (ENXIO);
		}

		/* Allocate a larger pty array */
		for (newnpty = npty; newnpty <= ptn;)
			newnpty *= 2;
		if (newnpty > maxptys)
			newnpty = maxptys;
		newpt = ptyarralloc(newnpty);

		/*
		 * Now grab the pty array mutex - we need to ensure
		 * that the pty array is consistent while copying it's
		 * content to newly allocated, larger space; we also
		 * need to be safe against pty_maxptys().
		 */
		simple_lock(&pt_softc_mutex);

		if (newnpty >= maxptys) {
			/* limit cut away beneath us... */
			newnpty = maxptys;
			if (ptn >= newnpty) {
				simple_unlock(&pt_softc_mutex);
				free(newpt, M_DEVBUF);
				goto limit_reached;
			}
		}

		/*
		 * If the pty array was not enlarged while we were waiting
		 * for mutex, copy current contents of pt_softc[] to newly
		 * allocated array and start using the new bigger array.
		 */
		if (newnpty > npty) {
			memcpy(newpt, pt_softc, npty*sizeof(struct pt_softc *));
			oldpt = pt_softc;
			pt_softc = newpt;
			npty = newnpty;
		} else {
			/* was enlarged when waited for lock, free new space */
			oldpt = newpt;
		}

		simple_unlock(&pt_softc_mutex);
		free(oldpt, M_DEVBUF);
	}

	/*
	 * If the entry is not yet allocated, allocate one. The mutex is
	 * needed so that the state of pt_softc[] array is consistant
	 * in case it has been lengthened above.
	 */
	if (!pt_softc[ptn]) {
		MALLOC(pti, struct pt_softc *, sizeof(struct pt_softc),
			M_DEVBUF, M_WAITOK);
		memset(pti, 0, sizeof(struct pt_softc));

	 	pti->pt_tty = ttymalloc();

		simple_lock(&pt_softc_mutex);

		/*
		 * Check the entry again - it might have been
		 * added while we were waiting for mutex.
		 */
		if (!pt_softc[ptn]) {
			tty_attach(pti->pt_tty);
			pt_softc[ptn] = pti;
		} else {
			ttyfree(pti->pt_tty);
			free(pti, M_DEVBUF);
		}

		simple_unlock(&pt_softc_mutex);
	}

	return (0);
}

/*
 * Set maxpty in thread-safe way. Returns 0 in case of error, otherwise
 * new value of maxptys.
 */
int
pty_maxptys(newmax, set)
	int newmax, set;
{
	if (!set)
		return (maxptys);

	/*
	 * We have to grab the pt_softc lock, so that we would pick correct
	 * value of npty (might be modified in pty_check()).
	 */
	simple_lock(&pt_softc_mutex);

	/*
	 * The value cannot be set to value lower than the highest pty
	 * number ever allocated.
	 */
	if (newmax >= npty)
		maxptys = newmax;
	else
		newmax = 0;

	simple_unlock(&pt_softc_mutex);

	return newmax;
}

/*
 * Establish n (or default if n is 1) ptys in the system.
 */
void
ptyattach(n)
	int n;
{
	/* maybe should allow 0 => none? */
	if (n <= 1)
		n = DEFAULT_NPTYS;
	pt_softc = ptyarralloc(n);
	npty = n;
#ifndef NO_DEV_PTM
	ptmattach(1);
#endif
}

/*ARGSUSED*/
int
ptsopen(dev, flag, devtype, l)
	dev_t dev;
	int flag, devtype;
	struct lwp *l;
{
	struct pt_softc *pti;
	struct tty *tp;
	int error;
	int ptn = minor(dev);
	int s;

	if ((error = pty_check(ptn)) != 0)
		return (error);

	pti = pt_softc[ptn];
	tp = pti->pt_tty;

	if (!ISSET(tp->t_state, TS_ISOPEN)) {
		ttychars(tp);		/* Set up default chars */
		tp->t_iflag = TTYDEF_IFLAG;
		tp->t_oflag = TTYDEF_OFLAG;
		tp->t_lflag = TTYDEF_LFLAG;
		tp->t_cflag = TTYDEF_CFLAG;
		tp->t_ispeed = tp->t_ospeed = TTYDEF_SPEED;
		ttsetwater(tp);		/* would be done in xxparam() */
	} else if (ISSET(tp->t_state, TS_XCLUDE) &&
	    kauth_cred_geteuid(l->l_cred) != 0)
		return (EBUSY);
	if (tp->t_oproc)			/* Ctrlr still around. */
		SET(tp->t_state, TS_CARR_ON);

	if (!ISSET(flag, O_NONBLOCK)) {
		s = spltty();
		TTY_LOCK(tp);
		while (!ISSET(tp->t_state, TS_CARR_ON)) {
			tp->t_wopen++;
			error = ttysleep(tp, &tp->t_rawq, TTIPRI | PCATCH,
			    ttopen, 0);
			tp->t_wopen--;
			if (error) {
				TTY_UNLOCK(tp);
				splx(s);
				return (error);
			}
		}
		TTY_UNLOCK(tp);
		splx(s);
	}
	error = (*tp->t_linesw->l_open)(dev, tp);
	ptcwakeup(tp, FREAD|FWRITE);
	return (error);
}

int
ptsclose(dev, flag, mode, l)
	dev_t dev;
	int flag, mode;
	struct lwp *l;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	int error;

	error = (*tp->t_linesw->l_close)(tp, flag);
	error |= ttyclose(tp);
	ptcwakeup(tp, FREAD|FWRITE);
	return (error);
}

int
ptsread(dev, uio, flag)
	dev_t dev;
	struct uio *uio;
	int flag;
{
	struct proc *p = curproc;
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	int error = 0;
	int cc;
	int s;

again:
	if (pti->pt_flags & PF_REMOTE) {
		while (isbackground(p, tp)) {
			if (sigismasked(p, SIGTTIN) ||
			    p->p_pgrp->pg_jobc == 0 ||
			    p->p_flag & P_PPWAIT)
				return (EIO);
			pgsignal(p->p_pgrp, SIGTTIN, 1);
			s = spltty();
			TTY_LOCK(tp);
			error = ttysleep(tp, (caddr_t)&lbolt,
					 TTIPRI | PCATCH | PNORELOCK, ttybg, 0);
			splx(s);
			if (error)
				return (error);
		}
		s = spltty();
		TTY_LOCK(tp);
		if (tp->t_canq.c_cc == 0) {
			if (flag & IO_NDELAY) {
				TTY_UNLOCK(tp);
				splx(s);
				return (EWOULDBLOCK);
			}
			error = ttysleep(tp, (caddr_t)&tp->t_canq,
					 TTIPRI | PCATCH | PNORELOCK, ttyin, 0);
			splx(s);
			if (error)
				return (error);
			goto again;
		}
		while(error == 0 && tp->t_canq.c_cc > 1 && uio->uio_resid > 0) {
			TTY_UNLOCK(tp);
			splx(s);
			error = ureadc(getc(&tp->t_canq), uio);
			s = spltty();
			TTY_LOCK(tp);
			/* Re-check terminal state here? */
		}
		if (tp->t_canq.c_cc == 1)
			(void) getc(&tp->t_canq);
		cc = tp->t_canq.c_cc;
		TTY_UNLOCK(tp);
		splx(s);
		if (cc)
			return (error);
	} else
		if (tp->t_oproc)
			error = (*tp->t_linesw->l_read)(tp, uio, flag);
	ptcwakeup(tp, FWRITE);
	return (error);
}

/*
 * Write to pseudo-tty.
 * Wakeups of controlling tty will happen
 * indirectly, when tty driver calls ptsstart.
 */
int
ptswrite(dev, uio, flag)
	dev_t dev;
	struct uio *uio;
	int flag;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;

	if (tp->t_oproc == 0)
		return (EIO);
	return ((*tp->t_linesw->l_write)(tp, uio, flag));
}

/*
 * Poll pseudo-tty.
 */
int
ptspoll(dev, events, l)
	dev_t dev;
	int events;
	struct lwp *l;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;

	if (tp->t_oproc == 0)
		return (POLLHUP);

	return ((*tp->t_linesw->l_poll)(tp, events, l));
}

/*
 * Start output on pseudo-tty.
 * Wake up process polling or sleeping for input from controlling tty.
 * Called with tty slock held.
 */
void
ptsstart(tp)
	struct tty *tp;
{
	struct pt_softc *pti = pt_softc[minor(tp->t_dev)];

	if (ISSET(tp->t_state, TS_TTSTOP))
		return;
	if (pti->pt_flags & PF_STOPPED) {
		pti->pt_flags &= ~PF_STOPPED;
		pti->pt_send = TIOCPKT_START;
	}

	selnotify(&pti->pt_selr, NOTE_SUBMIT);
	wakeup((caddr_t)&tp->t_outq.c_cf);
}

/*
 * Stop output.
 * Called with tty slock held.
 */
void
ptsstop(tp, flush)
	struct tty *tp;
	int flush;
{
	struct pt_softc *pti = pt_softc[minor(tp->t_dev)];

	/* note: FLUSHREAD and FLUSHWRITE already ok */
	if (flush == 0) {
		flush = TIOCPKT_STOP;
		pti->pt_flags |= PF_STOPPED;
	} else
		pti->pt_flags &= ~PF_STOPPED;
	pti->pt_send |= flush;

	/* change of perspective */
	if (flush & FREAD) {
		selnotify(&pti->pt_selw, NOTE_SUBMIT);
		wakeup((caddr_t)&tp->t_rawq.c_cf);
	}
	if (flush & FWRITE) {
		selnotify(&pti->pt_selr, NOTE_SUBMIT);
		wakeup((caddr_t)&tp->t_outq.c_cf);
	}
}

void
ptcwakeup(tp, flag)
	struct tty *tp;
	int flag;
{
	struct pt_softc *pti = pt_softc[minor(tp->t_dev)];
	int s;

	s = spltty();
	TTY_LOCK(tp);
	if (flag & FREAD) {
		selnotify(&pti->pt_selr, NOTE_SUBMIT);
		wakeup((caddr_t)&tp->t_outq.c_cf);
	}
	if (flag & FWRITE) {
		selnotify(&pti->pt_selw, NOTE_SUBMIT);
		wakeup((caddr_t)&tp->t_rawq.c_cf);
	}
	TTY_UNLOCK(tp);
	splx(s);
}

/*ARGSUSED*/
int
ptcopen(dev, flag, devtype, l)
	dev_t dev;
	int flag, devtype;
	struct lwp *l;
{
	struct pt_softc *pti;
	struct tty *tp;
	int error;
	int ptn = minor(dev);
	int s;

	if ((error = pty_check(ptn)) != 0)
		return (error);

	pti = pt_softc[ptn];
	tp = pti->pt_tty;

	s = spltty();
	TTY_LOCK(tp);
	if (tp->t_oproc) {
		TTY_UNLOCK(tp);
		splx(s);
		return (EIO);
	}
	tp->t_oproc = ptsstart;
	TTY_UNLOCK(tp);
	splx(s);
	(void)(*tp->t_linesw->l_modem)(tp, 1);
	CLR(tp->t_lflag, EXTPROC);
	pti->pt_flags = 0;
	pti->pt_send = 0;
	pti->pt_ucntl = 0;
	return (0);
}

/*ARGSUSED*/
int
ptcclose(dev, flag, devtype, l)
	dev_t dev;
	int flag, devtype;
	struct lwp *l;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	int s;

	(void)(*tp->t_linesw->l_modem)(tp, 0);
	CLR(tp->t_state, TS_CARR_ON);
	s = spltty();
	TTY_LOCK(tp);
	tp->t_oproc = 0;		/* mark closed */
	TTY_UNLOCK(tp);
	splx(s);
	return (0);
}

int
ptcread(dev, uio, flag)
	dev_t dev;
	struct uio *uio;
	int flag;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	u_char bf[BUFSIZ];
	int error = 0, cc;
	int s;

	/*
	 * We want to block until the slave
	 * is open, and there's something to read;
	 * but if we lost the slave or we're NBIO,
	 * then return the appropriate error instead.
	 */
	s = spltty();
	TTY_LOCK(tp);
	for (;;) {
		if (ISSET(tp->t_state, TS_ISOPEN)) {
			if (pti->pt_flags & PF_PKT && pti->pt_send) {
				TTY_UNLOCK(tp);
				splx(s);
				error = ureadc((int)pti->pt_send, uio);
				if (error)
					return (error);
				/*
				 * Since we don't have the tty locked, there's
				 * a risk of messing up `t_termios'. This is
				 * relevant only if the tty got closed and then
				 * opened again while we were out uiomoving.
				 */
				if (pti->pt_send & TIOCPKT_IOCTL) {
					cc = min(uio->uio_resid,
						sizeof(tp->t_termios));
					uiomove((caddr_t) &tp->t_termios,
						cc, uio);
				}
				pti->pt_send = 0;
				return (0);
			}
			if (pti->pt_flags & PF_UCNTL && pti->pt_ucntl) {
				TTY_UNLOCK(tp);
				splx(s);
				error = ureadc((int)pti->pt_ucntl, uio);
				if (error)
					return (error);
				pti->pt_ucntl = 0;
				return (0);
			}
			if (tp->t_outq.c_cc && !ISSET(tp->t_state, TS_TTSTOP))
				break;
		}
		if (!ISSET(tp->t_state, TS_CARR_ON)) {
			error = 0;	/* EOF */
			goto out;
		}
		if (flag & IO_NDELAY) {
			error = EWOULDBLOCK;
			goto out;
		}
		error = ltsleep((caddr_t)&tp->t_outq.c_cf, TTIPRI | PCATCH,
				ttyin, 0, &tp->t_slock);
		if (error)
			goto out;
	}

	if (pti->pt_flags & (PF_PKT|PF_UCNTL)) {
		TTY_UNLOCK(tp);
		splx(s);
		error = ureadc(0, uio);
		s = spltty();
		TTY_LOCK(tp);
		if (error == 0 && !ISSET(tp->t_state, TS_ISOPEN))
			error = EIO;
	}
	while (uio->uio_resid > 0 && error == 0) {
		cc = q_to_b(&tp->t_outq, bf, min(uio->uio_resid, BUFSIZ));
		if (cc <= 0)
			break;
		TTY_UNLOCK(tp);
		splx(s);
		error = uiomove(bf, cc, uio);
		s = spltty();
		TTY_LOCK(tp);
		if (error == 0 && !ISSET(tp->t_state, TS_ISOPEN))
			error = EIO;
	}

	if (tp->t_outq.c_cc <= tp->t_lowat) {
		if (ISSET(tp->t_state, TS_ASLEEP)) {
			CLR(tp->t_state, TS_ASLEEP);
			wakeup((caddr_t)&tp->t_outq);
		}
		selnotify(&tp->t_wsel, NOTE_SUBMIT);
	}
out:
	TTY_UNLOCK(tp);
	splx(s);
	return (error);
}


int
ptcwrite(dev, uio, flag)
	dev_t dev;
	struct uio *uio;
	int flag;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	u_char *cp = NULL;
	int cc = 0;
	u_char locbuf[BUFSIZ];
	int cnt = 0;
	int error = 0;
	int s;

again:
	s = spltty();
	TTY_LOCK(tp);
	if (!ISSET(tp->t_state, TS_ISOPEN))
		goto block;
	if (pti->pt_flags & PF_REMOTE) {
		if (tp->t_canq.c_cc)
			goto block;
		while (uio->uio_resid > 0 && tp->t_canq.c_cc < TTYHOG - 1) {
			if (cc == 0) {
				cc = min(uio->uio_resid, BUFSIZ);
				cc = min(cc, TTYHOG - 1 - tp->t_canq.c_cc);
				cp = locbuf;
				TTY_UNLOCK(tp);
				splx(s);
				error = uiomove((caddr_t)cp, cc, uio);
				if (error)
					return (error);
				s = spltty();
				TTY_LOCK(tp);
				/* check again for safety */
				if (!ISSET(tp->t_state, TS_ISOPEN)) {
					uip->
					error = EIO;
					goto out;
				}
			}
			if (cc)
				(void) b_to_q(cp, cc, &tp->t_canq);
			cc = 0;
		}
		(void) putc(0, &tp->t_canq);
		ttwakeup(tp);
		wakeup((caddr_t)&tp->t_canq);
		error = 0;
		goto out;
	}
	while (uio->uio_resid > 0) {
		if (cc == 0) {
			cc = min(uio->uio_resid, BUFSIZ);
			cp = locbuf;
			TTY_UNLOCK(tp);
			splx(s);
			error = uiomove((caddr_t)cp, cc, uio);
			if (error)
				return (error);
			s = spltty();
			TTY_LOCK(tp);
			/* check again for safety */
			if (!ISSET(tp->t_state, TS_ISOPEN)) {
				/* adjust for data copied in but not written */
				uio->uio_resid += cc;
				error = EIO;
				goto out;
			}
		}
		while (cc > 0) {
			if ((tp->t_rawq.c_cc + tp->t_canq.c_cc) >= TTYHOG - 2 &&
			   (tp->t_canq.c_cc > 0 || !ISSET(tp->t_lflag, ICANON))) {
				wakeup((caddr_t)&tp->t_rawq);
				goto block;
			}
			/* XXX - should change l_rint to be called with lock
			 *	 see also tty.c:ttyinput_wlock()
			 */
			TTY_UNLOCK(tp);
			splx(s);
			(*tp->t_linesw->l_rint)(*cp++, tp);
			s = spltty();
			TTY_LOCK(tp);
			cnt++;
			cc--;
		}
		cc = 0;
	}
	error = 0;
	goto out;

block:
	/*
	 * Come here to wait for slave to open, for space
	 * in outq, or space in rawq.
	 */
	if (!ISSET(tp->t_state, TS_CARR_ON)) {
		/* adjust for data copied in but not written */
		uio->uio_resid += cc;
		error = EIO;
		goto out;
	}
	if (flag & IO_NDELAY) {
		/* adjust for data copied in but not written */
		uio->uio_resid += cc;
		error = cnt == 0 ? EWOULDBLOCK : 0;
		goto out;
	}
	error = ltsleep((caddr_t)&tp->t_rawq.c_cf, TTOPRI | PCATCH | PNORELOCK,
		       ttyout, 0, &tp->t_slock);
	splx(s);
	if (error) {
		/* adjust for data copied in but not written */
		uio->uio_resid += cc;
		return (error);
	}
	goto again;

out:
	TTY_UNLOCK(tp);
	splx(s);
	return (error);
}

int
ptcpoll(dev, events, l)
	dev_t dev;
	int events;
	struct lwp *l;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	int revents = 0;
	int s = splsoftclock();

	if (events & (POLLIN | POLLRDNORM))
		if (ISSET(tp->t_state, TS_ISOPEN) &&
		    ((tp->t_outq.c_cc > 0 && !ISSET(tp->t_state, TS_TTSTOP)) ||
		     ((pti->pt_flags & PF_PKT) && pti->pt_send) ||
		     ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl)))
			revents |= events & (POLLIN | POLLRDNORM);

	if (events & (POLLOUT | POLLWRNORM))
		if (ISSET(tp->t_state, TS_ISOPEN) &&
		    ((pti->pt_flags & PF_REMOTE) ?
		     (tp->t_canq.c_cc == 0) :
		     ((tp->t_rawq.c_cc + tp->t_canq.c_cc < TTYHOG-2) ||
		      (tp->t_canq.c_cc == 0 && ISSET(tp->t_lflag, ICANON)))))
			revents |= events & (POLLOUT | POLLWRNORM);

	if (events & POLLHUP)
		if (!ISSET(tp->t_state, TS_CARR_ON))
			revents |= POLLHUP;

	if (revents == 0) {
		if (events & (POLLIN | POLLHUP | POLLRDNORM))
			selrecord(l, &pti->pt_selr);

		if (events & (POLLOUT | POLLWRNORM))
			selrecord(l, &pti->pt_selw);
	}

	splx(s);
	return (revents);
}

static void
filt_ptcrdetach(struct knote *kn)
{
	struct pt_softc *pti;
	int		s;

	pti = kn->kn_hook;
	s = spltty();
	SLIST_REMOVE(&pti->pt_selr.sel_klist, kn, knote, kn_selnext);
	splx(s);
}

static int
filt_ptcread(struct knote *kn, long hint)
{
	struct pt_softc *pti;
	struct tty	*tp;
	int canread;

	pti = kn->kn_hook;
	tp = pti->pt_tty;

	canread = (ISSET(tp->t_state, TS_ISOPEN) &&
		    ((tp->t_outq.c_cc > 0 && !ISSET(tp->t_state, TS_TTSTOP)) ||
		     ((pti->pt_flags & PF_PKT) && pti->pt_send) ||
		     ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl)));

	if (canread) {
		/*
		 * c_cc is number of characters after output post-processing;
		 * the amount of data actually read(2) depends on
		 * setting of input flags for the terminal.
		 */
		kn->kn_data = tp->t_outq.c_cc;
		if (((pti->pt_flags & PF_PKT) && pti->pt_send) ||
		    ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl))
			kn->kn_data++;
	}

	return (canread);
}

static void
filt_ptcwdetach(struct knote *kn)
{
	struct pt_softc *pti;
	int		s;

	pti = kn->kn_hook;
	s = spltty();
	SLIST_REMOVE(&pti->pt_selw.sel_klist, kn, knote, kn_selnext);
	splx(s);
}

static int
filt_ptcwrite(struct knote *kn, long hint)
{
	struct pt_softc *pti;
	struct tty	*tp;
	int canwrite;
	int nwrite;

	pti = kn->kn_hook;
	tp = pti->pt_tty;

	canwrite = (ISSET(tp->t_state, TS_ISOPEN) &&
		    ((pti->pt_flags & PF_REMOTE) ?
		     (tp->t_canq.c_cc == 0) :
		     ((tp->t_rawq.c_cc + tp->t_canq.c_cc < TTYHOG-2) ||
		      (tp->t_canq.c_cc == 0 && ISSET(tp->t_lflag, ICANON)))));

	if (canwrite) {
		if (pti->pt_flags & PF_REMOTE)
			nwrite = tp->t_canq.c_cn;
		else {
			/* this is guaranteed to be > 0 due to above check */
			nwrite = tp->t_canq.c_cn
				- (tp->t_rawq.c_cc + tp->t_canq.c_cc);
		}
		kn->kn_data = nwrite;
	}

	return (canwrite);
}

static const struct filterops ptcread_filtops =
	{ 1, NULL, filt_ptcrdetach, filt_ptcread };
static const struct filterops ptcwrite_filtops =
	{ 1, NULL, filt_ptcwdetach, filt_ptcwrite };

int
ptckqfilter(dev_t dev, struct knote *kn)
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct klist	*klist;
	int		s;

	switch (kn->kn_filter) {
	case EVFILT_READ:
		klist = &pti->pt_selr.sel_klist;
		kn->kn_fop = &ptcread_filtops;
		break;
	case EVFILT_WRITE:
		klist = &pti->pt_selw.sel_klist;
		kn->kn_fop = &ptcwrite_filtops;
		break;
	default:
		return (1);
	}

	kn->kn_hook = pti;

	s = spltty();
	SLIST_INSERT_HEAD(klist, kn, kn_selnext);
	splx(s);

	return (0);
}

struct tty *
ptytty(dev)
	dev_t dev;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;

	return (tp);
}

/*ARGSUSED*/
int
ptyioctl(dev, cmd, data, flag, l)
	dev_t dev;
	u_long cmd;
	caddr_t data;
	int flag;
	struct lwp *l;
{
	struct pt_softc *pti = pt_softc[minor(dev)];
	struct tty *tp = pti->pt_tty;
	const struct cdevsw *cdev;
	u_char *cc = tp->t_cc;
	int stop, error, sig;
	int s;

	/*
	 * IF CONTROLLER STTY THEN MUST FLUSH TO PREVENT A HANG.
	 * ttywflush(tp) will hang if there are characters in the outq.
	 */
	if (cmd == TIOCEXT) {
		/*
		 * When the EXTPROC bit is being toggled, we need
		 * to send an TIOCPKT_IOCTL if the packet driver
		 * is turned on.
		 */
		if (*(int *)data) {
			if (pti->pt_flags & PF_PKT) {
				pti->pt_send |= TIOCPKT_IOCTL;
				ptcwakeup(tp, FREAD);
			}
			SET(tp->t_lflag, EXTPROC);
		} else {
			if (ISSET(tp->t_lflag, EXTPROC) &&
			    (pti->pt_flags & PF_PKT)) {
				pti->pt_send |= TIOCPKT_IOCTL;
				ptcwakeup(tp, FREAD);
			}
			CLR(tp->t_lflag, EXTPROC);
		}
		return(0);
	}

#ifndef NO_DEV_PTM
	/* Allow getting the name from either the master or the slave */
	if (cmd == TIOCPTSNAME)
		return pty_fill_ptmget(l, dev, -1, -1, data);
#endif

	cdev = cdevsw_lookup(dev);
	if (cdev != NULL && cdev->d_open == ptcopen)
		switch (cmd) {
#ifndef NO_DEV_PTM
		case TIOCGRANTPT:
			return pty_grant_slave(l, dev);
#endif

		case TIOCGPGRP:
			/*
			 * We avoid calling ttioctl on the controller since,
			 * in that case, tp must be the controlling terminal.
			 */
			*(int *)data = tp->t_pgrp ? tp->t_pgrp->pg_id : 0;
			return (0);

		case TIOCPKT:
			if (*(int *)data) {
				if (pti->pt_flags & PF_UCNTL)
					return (EINVAL);
				pti->pt_flags |= PF_PKT;
			} else
				pti->pt_flags &= ~PF_PKT;
			return (0);

		case TIOCUCNTL:
			if (*(int *)data) {
				if (pti->pt_flags & PF_PKT)
					return (EINVAL);
				pti->pt_flags |= PF_UCNTL;
			} else
				pti->pt_flags &= ~PF_UCNTL;
			return (0);

		case TIOCREMOTE:
			if (*(int *)data)
				pti->pt_flags |= PF_REMOTE;
			else
				pti->pt_flags &= ~PF_REMOTE;
			s = spltty();
			TTY_LOCK(tp);
			ttyflush(tp, FREAD|FWRITE);
			TTY_UNLOCK(tp);
			splx(s);
			return (0);

#ifdef COMPAT_OLDTTY
		case TIOCSETP:
		case TIOCSETN:
#endif
		case TIOCSETD:
		case TIOCSETA:
		case TIOCSETAW:
		case TIOCSETAF:
			TTY_LOCK(tp);
			ndflush(&tp->t_outq, tp->t_outq.c_cc);
			TTY_UNLOCK(tp);
			break;

		case TIOCSIG:
			sig = (int)(long)*(caddr_t *)data;
			if (sig <= 0 || sig >= NSIG)
				return (EINVAL);
			TTY_LOCK(tp);
			if (!ISSET(tp->t_lflag, NOFLSH))
				ttyflush(tp, FREAD|FWRITE);
			if ((sig == SIGINFO) &&
			    (!ISSET(tp->t_lflag, NOKERNINFO)))
				ttyinfo(tp, 1);
			TTY_UNLOCK(tp);
			pgsignal(tp->t_pgrp, sig, 1);
			return(0);
		}

	error = (*tp->t_linesw->l_ioctl)(tp, cmd, data, flag, l);
	if (error == EPASSTHROUGH)
		 error = ttioctl(tp, cmd, data, flag, l);
	if (error == EPASSTHROUGH) {
		if (pti->pt_flags & PF_UCNTL &&
		    (cmd & ~0xff) == UIOCCMD(0)) {
			if (cmd & 0xff) {
				pti->pt_ucntl = (u_char)cmd;
				ptcwakeup(tp, FREAD);
			}
			return (0);
		}
	}
	/*
	 * If external processing and packet mode send ioctl packet.
	 */
	if (ISSET(tp->t_lflag, EXTPROC) && (pti->pt_flags & PF_PKT)) {
		switch(cmd) {
		case TIOCSETA:
		case TIOCSETAW:
		case TIOCSETAF:
#ifdef COMPAT_OLDTTY
		case TIOCSETP:
		case TIOCSETN:
		case TIOCSETC:
		case TIOCSLTC:
		case TIOCLBIS:
		case TIOCLBIC:
		case TIOCLSET:
#endif
			pti->pt_send |= TIOCPKT_IOCTL;
			ptcwakeup(tp, FREAD);
		default:
			break;
		}
	}
	stop = ISSET(tp->t_iflag, IXON) && CCEQ(cc[VSTOP], CTRL('s'))
		&& CCEQ(cc[VSTART], CTRL('q'));
	if (pti->pt_flags & PF_NOSTOP) {
		if (stop) {
			pti->pt_send &= ~TIOCPKT_NOSTOP;
			pti->pt_send |= TIOCPKT_DOSTOP;
			pti->pt_flags &= ~PF_NOSTOP;
			ptcwakeup(tp, FREAD);
		}
	} else {
		if (!stop) {
			pti->pt_send &= ~TIOCPKT_DOSTOP;
			pti->pt_send |= TIOCPKT_NOSTOP;
			pti->pt_flags |= PF_NOSTOP;
			ptcwakeup(tp, FREAD);
		}
	}
	return (error);
}