kernel - Fix excessive call stack depth on stuck interrupt

[dragonfly.git] / sys / kern / tty_pty.c

/*
 * (MPSAFE)
 *
 * 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
 * $FreeBSD: src/sys/kern/tty_pty.c,v 1.74.2.4 2002/02/20 19:58:13 dillon Exp $
 */

/*
 * MPSAFE NOTE: 
 * Most functions here could use a separate lock to deal with concurrent
 * access to the 'pt's.
 *
 * Right now the tty_token must be held for all this.
 */

/*
 * Pseudo-teletype Driver
 * (Actually two drivers, requiring two dev_ops structures)
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/priv.h>
#include <sys/tty.h>
#include <sys/conf.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/signalvar.h>
#include <sys/malloc.h>
#include <sys/device.h>
#include <sys/thread2.h>
#include <sys/devfs.h>
#include <sys/stat.h>
#include <sys/sysctl.h>

MALLOC_DEFINE(M_PTY, "ptys", "pty data structures");

static void ptsstart (struct tty *tp);
static void ptsstop (struct tty *tp, int rw);
static void ptsunhold (struct tty *tp);
static void ptcwakeup (struct tty *tp, int flag);
static void ptyinit (int n);
static int  filt_ptcread (struct knote *kn, long hint);
static void filt_ptcrdetach (struct knote *kn);
static int  filt_ptcwrite (struct knote *kn, long hint);
static void filt_ptcwdetach (struct knote *kn);

static  d_open_t        ptsopen;
static  d_close_t       ptsclose;
static  d_read_t        ptsread;
static  d_write_t       ptswrite;
static  d_ioctl_t       ptyioctl;
static  d_open_t        ptcopen;
static  d_close_t       ptcclose;
static  d_read_t        ptcread;
static  d_write_t       ptcwrite;
static  d_kqfilter_t    ptckqfilter;

DEVFS_DEFINE_CLONE_BITMAP(pty);

static  d_clone_t       ptyclone;

static int      pty_debug_level = 0;

static struct dev_ops pts98_ops = {
        { "pts98", 0, D_TTY | D_MPSAFE },
        .d_open =       ptsopen,
        .d_close =      ptsclose,
        .d_read =       ptsread,
        .d_write =      ptswrite,
        .d_ioctl =      ptyioctl,
        .d_kqfilter =   ttykqfilter,
        .d_revoke =     ttyrevoke
};

static struct dev_ops ptc98_ops = {
        { "ptc98", 0, D_TTY | D_MASTER | D_MPSAFE },
        .d_open =       ptcopen,
        .d_close =      ptcclose,
        .d_read =       ptcread,
        .d_write =      ptcwrite,
        .d_ioctl =      ptyioctl,
        .d_kqfilter =   ptckqfilter,
        .d_revoke =     ttyrevoke
};

static struct dev_ops pts_ops = {
        { "pts", 0, D_TTY | D_MPSAFE },
        .d_open =       ptsopen,
        .d_close =      ptsclose,
        .d_read =       ptsread,
        .d_write =      ptswrite,
        .d_ioctl =      ptyioctl,
        .d_kqfilter =   ttykqfilter,
        .d_revoke =     ttyrevoke
};

#define CDEV_MAJOR_C    6
static struct dev_ops ptc_ops = {
        { "ptc", 0, D_TTY | D_MASTER | D_MPSAFE },
        .d_open =       ptcopen,
        .d_close =      ptcclose,
        .d_read =       ptcread,
        .d_write =      ptcwrite,
        .d_ioctl =      ptyioctl,
        .d_kqfilter =   ptckqfilter,
        .d_revoke =     ttyrevoke
};

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

struct  pt_ioctl {
        int     pt_flags;
        int     pt_refs;        /* Structural references interlock S/MOPEN */
        int     pt_uminor;
        struct  kqinfo pt_kqr, pt_kqw;
        u_char  pt_send;
        u_char  pt_ucntl;
        struct tty pt_tty;
        cdev_t  devs, devc;
        struct  prison *pt_prison;
};

/*
 * pt_flags ptc state
 */
#define PF_PKT          0x0008          /* packet mode */
#define PF_STOPPED      0x0010          /* user told stopped */
#define PF_REMOTE       0x0020          /* remote and flow controlled input */
#define PF_NOSTOP       0x0040
#define PF_UCNTL        0x0080          /* user control mode */

#define PF_PTCSTATEMASK 0x00FF

/*
 * pt_flags open state.  Note that PF_SCLOSED is used to activate
 * read EOF on the ptc so it is only set after the slave has been
 * opened and then closed, and cleared again if the slave is opened
 * again.
 */
#define PF_UNIX98       0x0100
#define PF_SOPEN        0x0200
#define PF_MOPEN        0x0400
#define PF_SCLOSED      0x0800
#define PF_TERMINATED   0x8000

/*
 * This function creates and initializes a pts/ptc pair
 *
 * pts == /dev/tty[pqrsPQRS][0123456789abcdefghijklmnopqrstuv]
 * ptc == /dev/pty[pqrsPQRS][0123456789abcdefghijklmnopqrstuv]
 *
 * XXX: define and add mapping of upper minor bits to allow more 
 *      than 256 ptys.
 */
static void
ptyinit(int n)
{
        cdev_t devs, devc;
        char *names = "pqrsPQRS";
        struct pt_ioctl *pt;

        /* For now we only map the lower 8 bits of the minor */
        if (n & ~0xff)
                return;

        pt = kmalloc(sizeof(*pt), M_PTY, M_WAITOK | M_ZERO);
        pt->devs = devs = make_dev(&pts_ops, n,
            0, 0, 0666, "tty%c%r", names[n / 32], n % 32);
        pt->devc = devc = make_dev(&ptc_ops, n,
            0, 0, 0666, "pty%c%r", names[n / 32], n % 32);

        pt->pt_tty.t_dev = devs;
        pt->pt_uminor = n;
        devs->si_drv1 = devc->si_drv1 = pt;
        devs->si_tty = devc->si_tty = &pt->pt_tty;
        devs->si_flags |= SI_OVERRIDE;  /* uid, gid, perms from dev */
        devc->si_flags |= SI_OVERRIDE;  /* uid, gid, perms from dev */
        ttyregister(&pt->pt_tty);
}

static int
ptyclone(struct dev_clone_args *ap)
{
        int unit;
        struct pt_ioctl *pt;

        /*
         * Limit the number of unix98 pty (slave) devices to 1000, as
         * the utmp(5) format only allows for 8 bytes for the tty,
         * "pts/XXX".
         * If this limit is reached, we don't clone and return error
         * to devfs.
         */
        unit = devfs_clone_bitmap_get(&DEVFS_CLONE_BITMAP(pty), 1000);

        if (unit < 0) {
                ap->a_dev = NULL;
                return 1;
        }

        pt = kmalloc(sizeof(*pt), M_PTY, M_WAITOK | M_ZERO);

        pt->devc = make_only_dev(&ptc98_ops, unit,
                                 ap->a_cred->cr_ruid,
                                 0, 0600, "ptm/%d", unit);
        pt->devs = make_dev(&pts98_ops, unit,
                            ap->a_cred->cr_ruid,
                            GID_TTY, 0620, "pts/%d", unit);
        ap->a_dev = pt->devc;

        pt->devs->si_flags |= SI_OVERRIDE;      /* uid, gid, perms from dev */
        pt->devc->si_flags |= SI_OVERRIDE;      /* uid, gid, perms from dev */

        pt->pt_tty.t_dev = pt->devs;
        pt->pt_flags |= PF_UNIX98;
        pt->pt_uminor = unit;
        pt->devs->si_drv1 = pt->devc->si_drv1 = pt;
        pt->devs->si_tty = pt->devc->si_tty = &pt->pt_tty;

        ttyregister(&pt->pt_tty);

        return 0;
}

/*
 * pti_hold() prevents the pti from being destroyed due to a termination
 * while a pt*open() is blocked.
 *
 * This function returns non-zero if we cannot hold due to a termination
 * interlock.
 *
 * NOTE: Must be called with tty_token held
 */
static int
pti_hold(struct pt_ioctl *pti)
{
        if (pti->pt_flags & PF_TERMINATED)
                return(ENXIO);
        ++pti->pt_refs;
        return(0);
}

/*
 * pti_done() releases the reference and checks to see if both sides have
 * been closed on a unix98 pty, allowing us to destroy the device and
 * release resources.
 *
 * We do not release resources on non-unix98 ptys.  Those are left
 * statically allocated.
 */
static void
pti_done(struct pt_ioctl *pti)
{
        lwkt_gettoken(&tty_token);
        if (--pti->pt_refs == 0) {
                cdev_t dev;
                int uminor_no;

                /*
                 * Only unix09 ptys are freed up
                 */
                if ((pti->pt_flags & PF_UNIX98) == 0) {
                        lwkt_reltoken(&tty_token);
                        return;
                }

                /*
                 * Interlock open attempts against termination by setting
                 * PF_TERMINATED.  This allows us to block while cleaning
                 * out the device infrastructure.
                 *
                 * Do not terminate the tty if it still has a session
                 * association (t_refs).
                 */
                if ((pti->pt_flags & (PF_SOPEN|PF_MOPEN)) == 0 &&
                    pti->pt_tty.t_refs == 0) {
                        pti->pt_flags |= PF_TERMINATED;
                        uminor_no = pti->pt_uminor;

                        if ((dev = pti->devs) != NULL) {
                                dev->si_drv1 = NULL;
                                pti->devs = NULL;
                                destroy_dev(dev);
                        }
                        if ((dev = pti->devc) != NULL) {
                                dev->si_drv1 = NULL;
                                pti->devc = NULL;
                                destroy_dev(dev);
                        }
                        ttyunregister(&pti->pt_tty);
                        devfs_clone_bitmap_put(&DEVFS_CLONE_BITMAP(pty),
                                               uminor_no);
                        kfree(pti, M_PTY);
                }
        }
        lwkt_reltoken(&tty_token);
}

/*ARGSUSED*/
static  int
ptsopen(struct dev_open_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp;
        int error;
        struct pt_ioctl *pti;

        /*
         * The pti will already be assigned by the clone code or
         * pre-created if a non-unix 98 pty.  If si_drv1 is NULL
         * we are somehow racing a unix98 termination.
         */
        if (dev->si_drv1 == NULL)
                return(ENXIO);
        pti = dev->si_drv1;

        lwkt_gettoken(&tty_token);
        if (pti_hold(pti)) {
                lwkt_reltoken(&tty_token);
                return(ENXIO);
        }

        tp = dev->si_tty;

        /*
         * Reinit most of the tty state if it isn't open.  Handle
         * exclusive access.
         */
        if ((tp->t_state & TS_ISOPEN) == 0) {
                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;
        } else if ((tp->t_state & TS_XCLUDE) &&
                   priv_check_cred(ap->a_cred, PRIV_ROOT, 0)) {
                pti_done(pti);
                lwkt_reltoken(&tty_token);
                return (EBUSY);
        } else if (pti->pt_prison != ap->a_cred->cr_prison) {
                pti_done(pti);
                lwkt_reltoken(&tty_token);
                return (EBUSY);
        }

        /*
         * If the ptc is already present this will connect us up.  It
         * is unclear if this is actually needed.
         *
         * If neither side is open be sure to clear any left over
         * ZOMBIE state before continuing.
         */
        if (tp->t_oproc)
                (void)(*linesw[tp->t_line].l_modem)(tp, 1);
        else if ((pti->pt_flags & PF_SOPEN) == 0)
                tp->t_state &= ~TS_ZOMBIE;

        /*
         * Wait for the carrier (ptc side)
         */
        while ((tp->t_state & TS_CARR_ON) == 0) {
                if (ap->a_oflags & FNONBLOCK)
                        break;
                error = ttysleep(tp, TSA_CARR_ON(tp), PCATCH, "ptsopn", 0);
                if (error) {
                        pti_done(pti);
                        lwkt_reltoken(&tty_token);
                        return (error);
                }
        }

        /*
         * Mark the tty open and mark the slave side as being open.
         */
        error = (*linesw[tp->t_line].l_open)(dev, tp);

        if (error == 0) {
                pti->pt_flags |= PF_SOPEN;
                pti->pt_flags &= ~PF_SCLOSED;
                ptcwakeup(tp, FREAD|FWRITE);
        }
        pti_done(pti);

        lwkt_reltoken(&tty_token);
        return (error);
}

static  int
ptsclose(struct dev_close_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp;
        struct pt_ioctl *pti = dev->si_drv1;
        int err;

        lwkt_gettoken(&tty_token);
        if (pti_hold(pti))
                panic("ptsclose on terminated pti");

        /*
         * Disconnect the slave side
         */
        tp = dev->si_tty;
        err = (*linesw[tp->t_line].l_close)(tp, ap->a_fflag);
        ptsstop(tp, FREAD|FWRITE);
        ttyclose(tp);                   /* clears t_state */

        /*
         * Mark the pts side closed and signal the ptc.  Do not mark the
         * tty a zombie... that is, allow the tty to be re-opened as long
         * as the ptc is still open.  The ptc will read() EOFs until the
         * pts side is reopened or the ptc is closed.
         *
         * xterm() depends on this behavior as it will revoke() the pts
         * and then reopen it after the (unnecessary old code) chmod.
         */
        pti->pt_flags &= ~PF_SOPEN;
        pti->pt_flags |= PF_SCLOSED;
        if (tp->t_oproc)
                ptcwakeup(tp, FREAD);
        pti_done(pti);
        lwkt_reltoken(&tty_token);
        return (err);
}

static  int
ptsread(struct dev_read_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct proc *p = curproc;
        struct tty *tp = dev->si_tty;
        struct pt_ioctl *pti = dev->si_drv1;
        struct lwp *lp;

        int error = 0;

        lp = curthread->td_lwp;

        lwkt_gettoken(&tty_token);
again:
        if (pti->pt_flags & PF_REMOTE) {
                while (isbackground(p, tp)) {
                        if (SIGISMEMBER(p->p_sigignore, SIGTTIN) ||
                            SIGISMEMBER(lp->lwp_sigmask, SIGTTIN) ||
                            p->p_pgrp->pg_jobc == 0 ||
                            (p->p_flags & P_PPWAIT)) {
                                lwkt_reltoken(&tty_token);
                                return (EIO);
                        }
                        pgsignal(p->p_pgrp, SIGTTIN, 1);
                        error = ttysleep(tp, &lbolt, PCATCH, "ptsbg", 0);
                        if (error) {
                                lwkt_reltoken(&tty_token);
                                return (error);
                        }
                }
                if (tp->t_canq.c_cc == 0) {
                        if (ap->a_ioflag & IO_NDELAY) {
                                lwkt_reltoken(&tty_token);
                                return (EWOULDBLOCK);
                        }
                        error = ttysleep(tp, TSA_PTS_READ(tp), PCATCH,
                                         "ptsin", 0);
                        if (error) {
                                lwkt_reltoken(&tty_token);
                                return (error);
                        }
                        goto again;
                }
                while (tp->t_canq.c_cc > 1 && ap->a_uio->uio_resid > 0)
                        if (ureadc(clist_getc(&tp->t_canq), ap->a_uio) < 0) {
                                error = EFAULT;
                                break;
                        }
                if (tp->t_canq.c_cc == 1)
                        clist_getc(&tp->t_canq);
                if (tp->t_canq.c_cc) {
                        lwkt_reltoken(&tty_token);
                        return (error);
                }
        } else
                if (tp->t_oproc)
                        error = (*linesw[tp->t_line].l_read)(tp, ap->a_uio, ap->a_ioflag);
        ptcwakeup(tp, FWRITE);
        lwkt_reltoken(&tty_token);
        return (error);
}

/*
 * Write to pseudo-tty.
 * Wakeups of controlling tty will happen
 * indirectly, when tty driver calls ptsstart.
 */
static  int
ptswrite(struct dev_write_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp;
        int ret;

        lwkt_gettoken(&tty_token);
        tp = dev->si_tty;
        if (tp->t_oproc == NULL) {
                lwkt_reltoken(&tty_token);
                return (EIO);
        }
        ret = ((*linesw[tp->t_line].l_write)(tp, ap->a_uio, ap->a_ioflag));
        lwkt_reltoken(&tty_token);
        return ret;
}

/*
 * Start output on pseudo-tty.
 * Wake up process selecting or sleeping for input from controlling tty.
 */
static void
ptsstart(struct tty *tp)
{
        lwkt_gettoken(&tty_token);
        struct pt_ioctl *pti = tp->t_dev->si_drv1;

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

/*
 * NOTE: Must be called with tty_token held
 */
static void
ptcwakeup(struct tty *tp, int flag)
{
        ASSERT_LWKT_TOKEN_HELD(&tty_token);

        if (flag & FREAD) {
                wakeup(TSA_PTC_READ(tp));
                KNOTE(&tp->t_rkq.ki_note, 0);
        }
        if (flag & FWRITE) {
                wakeup(TSA_PTC_WRITE(tp));
                KNOTE(&tp->t_wkq.ki_note, 0);
        }
}

static  int
ptcopen(struct dev_open_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp;
        struct pt_ioctl *pti;

        /*
         * The pti will already be assigned by the clone code or
         * pre-created if a non-unix 98 pty.  If si_drv1 is NULL
         * we are somehow racing a unix98 termination.
         */
        if (dev->si_drv1 == NULL)
                return(ENXIO);

        lwkt_gettoken(&tty_token);
        pti = dev->si_drv1;
        if (pti_hold(pti)) {
                lwkt_reltoken(&tty_token);
                return(ENXIO);
        }
        if (pti->pt_prison && pti->pt_prison != ap->a_cred->cr_prison) {
                pti_done(pti);
                lwkt_reltoken(&tty_token);
                return(EBUSY);
        }
        tp = dev->si_tty;
        if (tp->t_oproc) {
                pti_done(pti);
                lwkt_reltoken(&tty_token);
                return (EIO);
        }

        /*
         * If the slave side is not yet open clear any left over zombie
         * state before doing our modem control.
         */
        if ((pti->pt_flags & PF_SOPEN) == 0)
                tp->t_state &= ~TS_ZOMBIE;

        tp->t_oproc = ptsstart;
        tp->t_stop = ptsstop;
        tp->t_unhold = ptsunhold;

        /*
         * Carrier on!
         */
        (void)(*linesw[tp->t_line].l_modem)(tp, 1);

        tp->t_lflag &= ~EXTPROC;
        pti->pt_prison = ap->a_cred->cr_prison;
        pti->pt_flags &= ~PF_PTCSTATEMASK;
        pti->pt_send = 0;
        pti->pt_ucntl = 0;

        pti->devs->si_uid = ap->a_cred->cr_uid;
        pti->devs->si_gid = 0;
        pti->devs->si_perms = 0600;
        pti->devc->si_uid = ap->a_cred->cr_uid;
        pti->devc->si_gid = 0;
        pti->devc->si_perms = 0600;

        /*
         * Mark master side open.  This does not cause any events
         * on the slave side.
         */
        pti->pt_flags |= PF_MOPEN;
        pti_done(pti);

        lwkt_reltoken(&tty_token);
        return (0);
}

static  int
ptcclose(struct dev_close_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp;
        struct pt_ioctl *pti = dev->si_drv1;

        lwkt_gettoken(&tty_token);
        if (pti_hold(pti))
                panic("ptcclose on terminated pti");

        tp = dev->si_tty;
        (void)(*linesw[tp->t_line].l_modem)(tp, 0);

        /*
         * Mark the master side closed.  If the slave is still open
         * mark the tty ZOMBIE, preventing any new action until both
         * sides have closed.
         *
         * NOTE: The ttyflush() will wake up the slave once we've
         *       set appropriate flags.  The ZOMBIE flag will be
         *       cleared when the slave side is closed.
         */
        pti->pt_flags &= ~PF_MOPEN;
        if (pti->pt_flags & PF_SOPEN)
                tp->t_state |= TS_ZOMBIE;

        /*
         * Turn off the carrier and disconnect.  This will notify the slave
         * side.
         */
        if (tp->t_state & TS_ISOPEN) {
                tp->t_state &= ~(TS_CARR_ON | TS_CONNECTED);
                ttyflush(tp, FREAD | FWRITE);
        }
        tp->t_oproc = NULL;             /* mark closed */

        pti->pt_prison = NULL;
        pti->devs->si_uid = 0;
        pti->devs->si_gid = 0;
        pti->devs->si_perms = 0666;
        pti->devc->si_uid = 0;
        pti->devc->si_gid = 0;
        pti->devc->si_perms = 0666;

        pti_done(pti);

        lwkt_reltoken(&tty_token);
        return (0);
}

static  int
ptcread(struct dev_read_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp = dev->si_tty;
        struct pt_ioctl *pti = dev->si_drv1;
        char buf[BUFSIZ];
        int error = 0, cc;

        lwkt_gettoken(&tty_token);
        /*
         * 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.
         */
        for (;;) {
                if (tp->t_state&TS_ISOPEN) {
                        if ((pti->pt_flags & PF_PKT) && pti->pt_send) {
                                error = ureadc((int)pti->pt_send, ap->a_uio);
                                if (error) {
                                        lwkt_reltoken(&tty_token);
                                        return (error);
                                }
                                if (pti->pt_send & TIOCPKT_IOCTL) {
                                        cc = (int)szmin(ap->a_uio->uio_resid,
                                                        sizeof(tp->t_termios));
                                        uiomove((caddr_t)&tp->t_termios, cc,
                                                ap->a_uio);
                                }
                                pti->pt_send = 0;
                                lwkt_reltoken(&tty_token);
                                return (0);
                        }
                        if ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl) {
                                error = ureadc((int)pti->pt_ucntl, ap->a_uio);
                                if (error) {
                                        lwkt_reltoken(&tty_token);
                                        return (error);
                                }
                                pti->pt_ucntl = 0;
                                lwkt_reltoken(&tty_token);
                                return (0);
                        }
                        if (tp->t_outq.c_cc && (tp->t_state&TS_TTSTOP) == 0)
                                break;
                }
                if ((tp->t_state & TS_CONNECTED) == 0) {
                        lwkt_reltoken(&tty_token);
                        return (0);     /* EOF */
                }
                if (ap->a_ioflag & IO_NDELAY) {
                        lwkt_reltoken(&tty_token);
                        return (EWOULDBLOCK);
                }
                error = tsleep(TSA_PTC_READ(tp), PCATCH, "ptcin", 0);
                if (error) {
                        lwkt_reltoken(&tty_token);
                        return (error);
                }
        }
        if (pti->pt_flags & (PF_PKT|PF_UCNTL))
                error = ureadc(0, ap->a_uio);
        while (ap->a_uio->uio_resid > 0 && error == 0) {
                cc = q_to_b(&tp->t_outq, buf,
                            (int)szmin(ap->a_uio->uio_resid, BUFSIZ));
                if (cc <= 0)
                        break;
                error = uiomove(buf, (size_t)cc, ap->a_uio);
        }
        ttwwakeup(tp);
        lwkt_reltoken(&tty_token);
        return (error);
}

static  void
ptsstop(struct tty *tp, int flush)
{
        struct pt_ioctl *pti = tp->t_dev->si_drv1;
        int flag;

        lwkt_gettoken(&tty_token);
        /* note: FLUSHREAD and FLUSHWRITE already ok */
        if (pti) {
                if (flush == 0) {
                        flush = TIOCPKT_STOP;
                        pti->pt_flags |= PF_STOPPED;
                } else {
                        pti->pt_flags &= ~PF_STOPPED;
                }
                pti->pt_send |= flush;
                /* change of perspective */
        }
        flag = 0;
        if (flush & FREAD)
                flag |= FWRITE;
        if (flush & FWRITE)
                flag |= FREAD;
        ptcwakeup(tp, flag);

        lwkt_reltoken(&tty_token);
}

/*
 * ttyunhold() calls us instead of just decrementing tp->t_refs.  This
 * is needed because a session can hold onto a pts (half closed state)
 * even if there are no live file descriptors.  Without the callback
 * we can't clean up.
 */
static  void
ptsunhold(struct tty *tp)
{
        struct pt_ioctl *pti = tp->t_dev->si_drv1;

        lwkt_gettoken(&tty_token);
        pti_hold(pti);
        --tp->t_refs;
        pti_done(pti);
        lwkt_reltoken(&tty_token);
}

/*
 * kqueue ops for pseudo-terminals.
 */
static struct filterops ptcread_filtops =
        { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_ptcrdetach, filt_ptcread };
static struct filterops ptcwrite_filtops =
        { FILTEROP_ISFD|FILTEROP_MPSAFE, NULL, filt_ptcwdetach, filt_ptcwrite };

static  int
ptckqfilter(struct dev_kqfilter_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct knote *kn = ap->a_kn;
        struct tty *tp = dev->si_tty;
        struct klist *klist;

        ap->a_result = 0;
        switch (kn->kn_filter) {
        case EVFILT_READ:
                klist = &tp->t_rkq.ki_note;
                kn->kn_fop = &ptcread_filtops;
                break;
        case EVFILT_WRITE:
                klist = &tp->t_wkq.ki_note;
                kn->kn_fop = &ptcwrite_filtops;
                break;
        default:
                ap->a_result = EOPNOTSUPP;
                return (0);
        }

        kn->kn_hook = (caddr_t)dev;
        knote_insert(klist, kn);
        return (0);
}

static int
filt_ptcread (struct knote *kn, long hint)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;
        struct pt_ioctl *pti = ((cdev_t)kn->kn_hook)->si_drv1;

        lwkt_gettoken(&tty_token);
        if ((tp->t_state & TS_ZOMBIE) || (pti->pt_flags & PF_SCLOSED)) {
                lwkt_reltoken(&tty_token);
                kn->kn_flags |= (EV_EOF | EV_NODATA);
                return (1);
        }

        if ((tp->t_state & TS_ISOPEN) &&
            ((tp->t_outq.c_cc && (tp->t_state & TS_TTSTOP) == 0) ||
             ((pti->pt_flags & PF_PKT) && pti->pt_send) ||
             ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl))) {
                kn->kn_data = tp->t_outq.c_cc;
                lwkt_reltoken(&tty_token);
                return(1);
        } else {
                lwkt_reltoken(&tty_token);
                return(0);
        }
}

static int
filt_ptcwrite (struct knote *kn, long hint)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;
        struct pt_ioctl *pti = ((cdev_t)kn->kn_hook)->si_drv1;

        lwkt_gettoken(&tty_token);
        if (tp->t_state & TS_ZOMBIE) {
                lwkt_reltoken(&tty_token);
                kn->kn_flags |= (EV_EOF | EV_NODATA);
                return (1);
        }

        if (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 && (tp->t_lflag & ICANON))))) {
                kn->kn_data = tp->t_canq.c_cc + tp->t_rawq.c_cc;
                lwkt_reltoken(&tty_token);
                return(1);
        } else {
                lwkt_reltoken(&tty_token);
                return(0);
        }
        /* NOTREACHED */
}

static void
filt_ptcrdetach (struct knote *kn)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;

        knote_remove(&tp->t_rkq.ki_note, kn);
}

static void
filt_ptcwdetach (struct knote *kn)
{
        struct tty *tp = ((cdev_t)kn->kn_hook)->si_tty;

        knote_remove(&tp->t_wkq.ki_note, kn);
}

/*
 * I/O ops
 */
static  int
ptcwrite(struct dev_write_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp = dev->si_tty;
        u_char *cp = NULL;
        int cc = 0;
        u_char locbuf[BUFSIZ];
        int cnt = 0;
        struct pt_ioctl *pti = dev->si_drv1;
        int error = 0;

        lwkt_gettoken(&tty_token);
again:
        if ((tp->t_state&TS_ISOPEN) == 0)
                goto block;
        if (pti->pt_flags & PF_REMOTE) {
                if (tp->t_canq.c_cc)
                        goto block;
                while ((ap->a_uio->uio_resid > 0 || cc > 0) &&
                       tp->t_canq.c_cc < TTYHOG - 1) {
                        if (cc == 0) {
                                cc = (int)szmin(ap->a_uio->uio_resid, BUFSIZ);
                                cc = imin(cc, TTYHOG - 1 - tp->t_canq.c_cc);
                                cp = locbuf;
                                error = uiomove(cp, (size_t)cc, ap->a_uio);
                                if (error) {
                                        lwkt_reltoken(&tty_token);
                                        return (error);
                                }
                                /* check again for safety */
                                if ((tp->t_state & TS_ISOPEN) == 0) {
                                        /* adjust as usual */
                                        ap->a_uio->uio_resid += cc;
                                        lwkt_reltoken(&tty_token);
                                        return (EIO);
                                }
                        }
                        if (cc > 0) {
                                cc = b_to_q((char *)cp, cc, &tp->t_canq);
                                /*
                                 * XXX we don't guarantee that the canq size
                                 * is >= TTYHOG, so the above b_to_q() may
                                 * leave some bytes uncopied.  However, space
                                 * is guaranteed for the null terminator if
                                 * we don't fail here since (TTYHOG - 1) is
                                 * not a multiple of CBSIZE.
                                 */
                                if (cc > 0)
                                        break;
                        }
                }
                /* adjust for data copied in but not written */
                ap->a_uio->uio_resid += cc;
                clist_putc(0, &tp->t_canq);
                ttwakeup(tp);
                wakeup(TSA_PTS_READ(tp));
                lwkt_reltoken(&tty_token);
                return (0);
        }
        while (ap->a_uio->uio_resid > 0 || cc > 0) {
                if (cc == 0) {
                        cc = (int)szmin(ap->a_uio->uio_resid, BUFSIZ);
                        cp = locbuf;
                        error = uiomove(cp, (size_t)cc, ap->a_uio);
                        if (error) {
                                lwkt_reltoken(&tty_token);
                                return (error);
                        }
                        /* check again for safety */
                        if ((tp->t_state & TS_ISOPEN) == 0) {
                                /* adjust for data copied in but not written */
                                ap->a_uio->uio_resid += cc;
                                lwkt_reltoken(&tty_token);
                                return (EIO);
                        }
                }
                while (cc > 0) {
                        if ((tp->t_rawq.c_cc + tp->t_canq.c_cc) >= TTYHOG - 2 &&
                           (tp->t_canq.c_cc > 0 || !(tp->t_lflag&ICANON))) {
                                wakeup(TSA_HUP_OR_INPUT(tp));
                                goto block;
                        }
                        (*linesw[tp->t_line].l_rint)(*cp++, tp);
                        cnt++;
                        cc--;
                }
                cc = 0;
        }
        lwkt_reltoken(&tty_token);
        return (0);
block:
        /*
         * Come here to wait for slave to open, for space
         * in outq, or space in rawq, or an empty canq.
         */
        if ((tp->t_state & TS_CONNECTED) == 0) {
                /* adjust for data copied in but not written */
                ap->a_uio->uio_resid += cc;
                lwkt_reltoken(&tty_token);
                return (EIO);
        }
        if (ap->a_ioflag & IO_NDELAY) {
                /* adjust for data copied in but not written */
                ap->a_uio->uio_resid += cc;
                if (cnt == 0) {
                        lwkt_reltoken(&tty_token);
                        return (EWOULDBLOCK);
                }
                lwkt_reltoken(&tty_token);
                return (0);
        }
        error = tsleep(TSA_PTC_WRITE(tp), PCATCH, "ptcout", 0);
        if (error) {
                /* adjust for data copied in but not written */
                ap->a_uio->uio_resid += cc;
                lwkt_reltoken(&tty_token);
                return (error);
        }
        goto again;
}

/*ARGSUSED*/
static  int
ptyioctl(struct dev_ioctl_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct tty *tp = dev->si_tty;
        struct pt_ioctl *pti = dev->si_drv1;
        u_char *cc = tp->t_cc;
        int stop, error;

        lwkt_gettoken(&tty_token);
        if (dev_dflags(dev) & D_MASTER) {
                switch (ap->a_cmd) {

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

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

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

                case TIOCREMOTE:
                        if (*(int *)ap->a_data)
                                pti->pt_flags |= PF_REMOTE;
                        else
                                pti->pt_flags &= ~PF_REMOTE;
                        ttyflush(tp, FREAD|FWRITE);
                        lwkt_reltoken(&tty_token);
                        return (0);

                case TIOCISPTMASTER:
                        if ((pti->pt_flags & PF_UNIX98) &&
                            (pti->devc == dev)) {
                                lwkt_reltoken(&tty_token);
                                return (0);
                        } else {
                                lwkt_reltoken(&tty_token);
                                return (EINVAL);
                        }
                }

                /*
                 * The rest of the ioctls shouldn't be called until 
                 * the slave is open.
                 */
                if ((tp->t_state & TS_ISOPEN) == 0) {
                        lwkt_reltoken(&tty_token);
                        return (EAGAIN);
                }

                switch (ap->a_cmd) {
                case TIOCSETD:
                case TIOCSETA:
                case TIOCSETAW:
                case TIOCSETAF:
                        /*
                         * IF CONTROLLER STTY THEN MUST FLUSH TO PREVENT A HANG.
                         * ttywflush(tp) will hang if there are characters in
                         * the outq.
                         */
                        ndflush(&tp->t_outq, tp->t_outq.c_cc);
                        break;

                case TIOCSIG:
                        if (*(unsigned int *)ap->a_data >= NSIG ||
                            *(unsigned int *)ap->a_data == 0) {
                                lwkt_reltoken(&tty_token);
                                return(EINVAL);
                        }
                        if ((tp->t_lflag&NOFLSH) == 0)
                                ttyflush(tp, FREAD|FWRITE);
                        pgsignal(tp->t_pgrp, *(unsigned int *)ap->a_data, 1);
                        if ((*(unsigned int *)ap->a_data == SIGINFO) &&
                            ((tp->t_lflag&NOKERNINFO) == 0))
                                ttyinfo(tp);
                        lwkt_reltoken(&tty_token);
                        return(0);
                }
        }
        if (ap->a_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 *)ap->a_data) {
                        if (pti->pt_flags & PF_PKT) {
                                pti->pt_send |= TIOCPKT_IOCTL;
                                ptcwakeup(tp, FREAD);
                        }
                        tp->t_lflag |= EXTPROC;
                } else {
                        if ((tp->t_lflag & EXTPROC) &&
                            (pti->pt_flags & PF_PKT)) {
                                pti->pt_send |= TIOCPKT_IOCTL;
                                ptcwakeup(tp, FREAD);
                        }
                        tp->t_lflag &= ~EXTPROC;
                }
                lwkt_reltoken(&tty_token);
                return(0);
        }
        error = (*linesw[tp->t_line].l_ioctl)(tp, ap->a_cmd, ap->a_data,
                                              ap->a_fflag, ap->a_cred);
        if (error == ENOIOCTL)
                 error = ttioctl(tp, ap->a_cmd, ap->a_data, ap->a_fflag);
        if (error == ENOIOCTL) {
                if (pti->pt_flags & PF_UCNTL &&
                    (ap->a_cmd & ~0xff) == UIOCCMD(0)) {
                        if (ap->a_cmd & 0xff) {
                                pti->pt_ucntl = (u_char)ap->a_cmd;
                                ptcwakeup(tp, FREAD);
                        }
                        lwkt_reltoken(&tty_token);
                        return (0);
                }
                error = ENOTTY;
        }
        /*
         * If external processing and packet mode send ioctl packet.
         */
        if ((tp->t_lflag&EXTPROC) && (pti->pt_flags & PF_PKT)) {
                switch(ap->a_cmd) {
                case TIOCSETA:
                case TIOCSETAW:
                case TIOCSETAF:
                        pti->pt_send |= TIOCPKT_IOCTL;
                        ptcwakeup(tp, FREAD);
                default:
                        break;
                }
        }
        stop = (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);
                }
        }
        lwkt_reltoken(&tty_token);
        return (error);
}


static void ptc_drvinit (void *unused);

SYSCTL_INT(_kern, OID_AUTO, pty_debug, CTLFLAG_RW, &pty_debug_level,
                0, "Change pty debug level");

static void
ptc_drvinit(void *unused)
{
        int i;

        /*
         * Unix98 pty stuff.
         * Create the clonable base device.
         */
        make_autoclone_dev(&ptc_ops, &DEVFS_CLONE_BITMAP(pty), ptyclone,
            0, 0, 0666, "ptmx");

        for (i = 0; i < 256; i++) {
                ptyinit(i);
        }
}

SYSINIT(ptcdev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR_C, ptc_drvinit,
    NULL);