sys/kern/tty_pts.c

   1 /*-
   2  * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Portions of this software were developed under sponsorship from Snow
   6  * B.V., the Netherlands.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include <sys/cdefs.h>
  31 __FBSDID("$FreeBSD$");
  32
  33 #include "opt_tty.h"
  34
  35 /* Add compatibility bits for FreeBSD. */
  36 #define PTS_COMPAT
  37 #ifdef DEV_PTY
  38 /* Add /dev/ptyXX compat bits. */
  39 #define PTS_EXTERNAL
  40 #endif /* DEV_PTY */
  41 /* Add bits to make Linux binaries work. */
  42 #define PTS_LINUX
  43
  44 #include <sys/param.h>
  45 #include <sys/lock.h>
  46 #include <sys/condvar.h>
  47 #include <sys/conf.h>
  48 #include <sys/fcntl.h>
  49 #include <sys/file.h>
  50 #include <sys/filedesc.h>
  51 #include <sys/filio.h>
  52 #include <sys/kernel.h>
  53 #include <sys/malloc.h>
  54 #include <sys/poll.h>
  55 #include <sys/proc.h>
  56 #include <sys/resourcevar.h>
  57 #include <sys/serial.h>
  58 #include <sys/stat.h>
  59 #include <sys/syscall.h>
  60 #include <sys/syscallsubr.h>
  61 #include <sys/sysent.h>
  62 #include <sys/sysproto.h>
  63 #include <sys/systm.h>
  64 #include <sys/tty.h>
  65 #include <sys/ttycom.h>
  66
  67 #include <machine/stdarg.h>
  68
  69 static struct unrhdr *pts_pool;
  70 #define MAXPTSDEVS 999
  71
  72 static MALLOC_DEFINE(M_PTS, "pts", "pseudo tty device");
  73
  74 /*
  75  * Per-PTS structure.
  76  *
  77  * List of locks
  78  * (t)  locked by tty_lock()
  79  * (c)  const until freeing
  80  */
  81 struct pts_softc {
  82         int             pts_unit;       /* (c) Device unit number. */
  83         unsigned int    pts_flags;      /* (t) Device flags. */
  84 #define PTS_PKT         0x1     /* Packet mode. */
  85         char            pts_pkt;        /* (t) Unread packet mode data. */
  86
  87         struct cv       pts_inwait;     /* (t) Blocking write() on master. */
  88         struct selinfo  pts_inpoll;     /* (t) Select queue for write(). */
  89         struct cv       pts_outwait;    /* (t) Blocking read() on master. */
  90         struct selinfo  pts_outpoll;    /* (t) Select queue for read(). */
  91
  92 #ifdef PTS_EXTERNAL
  93         struct cdev     *pts_cdev;      /* (c) Master device node. */
  94 #endif /* PTS_EXTERNAL */
  95
  96         struct uidinfo  *pts_uidinfo;   /* (c) Resource limit. */
  97 };
  98
  99 /*
 100  * Controller-side file operations.
 101  */
 102
 103 static int
 104 ptsdev_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 105     int flags, struct thread *td)
 106 {
 107         struct tty *tp = fp->f_data;
 108         struct pts_softc *psc = tty_softc(tp);
 109         int error = 0;
 110         char pkt;
 111
 112         if (uio->uio_resid == 0)
 113                 return (0);
 114
 115         tty_lock(tp);
 116
 117         for (;;) {
 118                 /*
 119                  * Implement packet mode. When packet mode is turned on,
 120                  * the first byte contains a bitmask of events that
 121                  * occured (start, stop, flush, window size, etc).
 122                  */
 123                 if (psc->pts_flags & PTS_PKT && psc->pts_pkt) {
 124                         pkt = psc->pts_pkt;
 125                         psc->pts_pkt = 0;
 126                         tty_unlock(tp);
 127
 128                         error = ureadc(pkt, uio);
 129                         return (error);
 130                 }
 131
 132                 /*
 133                  * Transmit regular data.
 134                  *
 135                  * XXX: We shouldn't use ttydisc_getc_poll()! Even
 136                  * though in this implementation, there is likely going
 137                  * to be data, we should just call ttydisc_getc_uio()
 138                  * and use its return value to sleep.
 139                  */
 140                 if (ttydisc_getc_poll(tp)) {
 141                         if (psc->pts_flags & PTS_PKT) {
 142                                 /*
 143                                  * XXX: Small race. Fortunately PTY
 144                                  * consumers aren't multithreaded.
 145                                  */
 146
 147                                 tty_unlock(tp);
 148                                 error = ureadc(TIOCPKT_DATA, uio);
 149                                 if (error)
 150                                         return (error);
 151                                 tty_lock(tp);
 152                         }
 153
 154                         error = ttydisc_getc_uio(tp, uio);
 155                         break;
 156                 }
 157
 158                 /* Maybe the device isn't used anyway. */
 159                 if (tty_opened(tp) == 0)
 160                         break;
 161
 162                 /* Wait for more data. */
 163                 if (fp->f_flag & O_NONBLOCK) {
 164                         error = EWOULDBLOCK;
 165                         break;
 166                 }
 167                 error = cv_wait_sig(&psc->pts_outwait, tp->t_mtx);
 168                 if (error != 0)
 169                         break;
 170         }
 171
 172         tty_unlock(tp);
 173
 174         return (error);
 175 }
 176
 177 static int
 178 ptsdev_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 179     int flags, struct thread *td)
 180 {
 181         struct tty *tp = fp->f_data;
 182         struct pts_softc *psc = tty_softc(tp);
 183         char ib[256], *ibstart;
 184         size_t iblen, rintlen;
 185         int error = 0;
 186
 187         if (uio->uio_resid == 0)
 188                 return (0);
 189
 190         for (;;) {
 191                 ibstart = ib;
 192                 iblen = MIN(uio->uio_resid, sizeof ib);
 193                 error = uiomove(ib, iblen, uio);
 194
 195                 tty_lock(tp);
 196                 if (error != 0)
 197                         goto done;
 198
 199                 /*
 200                  * When possible, avoid the slow path. rint_bypass()
 201                  * copies all input to the input queue at once.
 202                  */
 203                 MPASS(iblen > 0);
 204                 do {
 205                         if (ttydisc_can_bypass(tp)) {
 206                                 /* Store data at once. */
 207                                 rintlen = ttydisc_rint_bypass(tp,
 208                                     ibstart, iblen);
 209                                 ibstart += rintlen;
 210                                 iblen -= rintlen;
 211
 212                                 if (iblen == 0) {
 213                                         /* All data written. */
 214                                         break;
 215                                 }
 216                         } else {
 217                                 error = ttydisc_rint(tp, *ibstart, 0);
 218                                 if (error == 0) {
 219                                         /* Character stored successfully. */
 220                                         ibstart++;
 221                                         iblen--;
 222                                         continue;
 223                                 }
 224                         }
 225
 226                         /* Maybe the device isn't used anyway. */
 227                         if (tty_opened(tp) == 0) {
 228                                 error = EIO;
 229                                 goto done;
 230                         }
 231
 232                         /* Wait for more data. */
 233                         if (fp->f_flag & O_NONBLOCK) {
 234                                 error = EWOULDBLOCK;
 235                                 goto done;
 236                         }
 237
 238                         /* Wake up users on the slave side. */
 239                         ttydisc_rint_done(tp);
 240                         error = cv_wait_sig(&psc->pts_inwait, tp->t_mtx);
 241                         if (error != 0)
 242                                 goto done;
 243                 } while (iblen > 0);
 244
 245                 if (uio->uio_resid == 0)
 246                         break;
 247                 tty_unlock(tp);
 248         }
 249
 250 done:   ttydisc_rint_done(tp);
 251         tty_unlock(tp);
 252         return (error);
 253 }
 254
 255 static int
 256 ptsdev_ioctl(struct file *fp, u_long cmd, void *data,
 257     struct ucred *active_cred, struct thread *td)
 258 {
 259         struct tty *tp = fp->f_data;
 260         struct pts_softc *psc = tty_softc(tp);
 261         int error = 0, sig;
 262
 263         switch (cmd) {
 264         case FIONBIO:
 265                 /* This device supports non-blocking operation. */
 266                 return (0);
 267         case FIODGNAME: {
 268                 struct fiodgname_arg *fgn;
 269                 const char *p;
 270                 int i;
 271
 272                 /* Reverse device name lookups, for ptsname() and ttyname(). */
 273                 fgn = data;
 274 #ifdef PTS_EXTERNAL
 275                 if (psc->pts_cdev != NULL)
 276                         p = devtoname(psc->pts_cdev);
 277                 else
 278 #endif /* PTS_EXTERNAL */
 279                         p = tty_devname(tp);
 280                 i = strlen(p) + 1;
 281                 if (i > fgn->len)
 282                         return (EINVAL);
 283                 return copyout(p, fgn->buf, i);
 284         }
 285
 286         /*
 287          * We need to implement TIOCGPGRP and TIOCGSID here again. When
 288          * called on the pseudo-terminal master, it should not check if
 289          * the terminal is the foreground terminal of the calling
 290          * process.
 291          *
 292          * TIOCGETA is also implemented here. Various Linux PTY routines
 293          * often call isatty(), which is implemented by tcgetattr().
 294          */
 295 #ifdef PTS_LINUX
 296         case TIOCGETA:
 297                 /* Obtain terminal flags through tcgetattr(). */
 298                 tty_lock(tp);
 299                 bcopy(&tp->t_termios, data, sizeof(struct termios));
 300                 tty_unlock(tp);
 301                 return (0);
 302 #endif /* PTS_LINUX */
 303         case TIOCSETAF:
 304         case TIOCSETAW:
 305                 /*
 306                  * We must make sure we turn tcsetattr() calls of TCSAFLUSH and
 307                  * TCSADRAIN into something different. If an application would
 308                  * call TCSAFLUSH or TCSADRAIN on the master descriptor, it may
 309                  * deadlock waiting for all data to be read.
 310                  */
 311                 cmd = TIOCSETA;
 312                 break;
 313 #if defined(PTS_COMPAT) || defined(PTS_LINUX)
 314         case TIOCGPTN:
 315                 /*
 316                  * Get the device unit number.
 317                  */
 318                 if (psc->pts_unit < 0)
 319                         return (ENOTTY);
 320                 *(unsigned int *)data = psc->pts_unit;
 321                 return (0);
 322 #endif /* PTS_COMPAT || PTS_LINUX */
 323         case TIOCGPGRP:
 324                 /* Get the foreground process group ID. */
 325                 tty_lock(tp);
 326                 if (tp->t_pgrp != NULL)
 327                         *(int *)data = tp->t_pgrp->pg_id;
 328                 else
 329                         *(int *)data = NO_PID;
 330                 tty_unlock(tp);
 331                 return (0);
 332         case TIOCGSID:
 333                 /* Get the session leader process ID. */
 334                 tty_lock(tp);
 335                 if (tp->t_session == NULL)
 336                         error = ENOTTY;
 337                 else
 338                         *(int *)data = tp->t_session->s_sid;
 339                 tty_unlock(tp);
 340                 return (error);
 341         case TIOCPTMASTER:
 342                 /* Yes, we are a pseudo-terminal master. */
 343                 return (0);
 344         case TIOCSIG:
 345                 /* Signal the foreground process group. */
 346                 sig = *(int *)data;
 347                 if (sig < 1 || sig >= NSIG)
 348                         return (EINVAL);
 349
 350                 tty_lock(tp);
 351                 tty_signal_pgrp(tp, sig);
 352                 tty_unlock(tp);
 353                 return (0);
 354         case TIOCPKT:
 355                 /* Enable/disable packet mode. */
 356                 tty_lock(tp);
 357                 if (*(int *)data)
 358                         psc->pts_flags |= PTS_PKT;
 359                 else
 360                         psc->pts_flags &= ~PTS_PKT;
 361                 tty_unlock(tp);
 362                 return (0);
 363         }
 364
 365         /* Just redirect this ioctl to the slave device. */
 366         tty_lock(tp);
 367         error = tty_ioctl(tp, cmd, data, td);
 368         tty_unlock(tp);
 369
 370         return (error);
 371 }
 372
 373 static int
 374 ptsdev_poll(struct file *fp, int events, struct ucred *active_cred,
 375     struct thread *td)
 376 {
 377         struct tty *tp = fp->f_data;
 378         struct pts_softc *psc = tty_softc(tp);
 379         int revents = 0;
 380
 381         tty_lock(tp);
 382
 383         if (tty_opened(tp) == 0) {
 384                 /* Slave device is not opened. */
 385                 tty_unlock(tp);
 386                 return (events &
 387                     (POLLHUP|POLLIN|POLLRDNORM|POLLOUT|POLLWRNORM));
 388         }
 389
 390         if (events & (POLLIN|POLLRDNORM)) {
 391                 /* See if we can getc something. */
 392                 if (ttydisc_getc_poll(tp) ||
 393                     (psc->pts_flags & PTS_PKT && psc->pts_pkt))
 394                         revents |= events & (POLLIN|POLLRDNORM);
 395         }
 396         if (events & (POLLOUT|POLLWRNORM)) {
 397                 /* See if we can rint something. */
 398                 if (ttydisc_rint_poll(tp))
 399                         revents |= events & (POLLOUT|POLLWRNORM);
 400         }
 401
 402         /*
 403          * No need to check for POLLHUP here. This device cannot be used
 404          * as a callout device, which means we always have a carrier,
 405          * because the master is.
 406          */
 407
 408         if (revents == 0) {
 409                 /*
 410                  * This code might look misleading, but the naming of
 411                  * poll events on this side is the opposite of the slave
 412                  * device.
 413                  */
 414                 if (events & (POLLIN|POLLRDNORM))
 415                         selrecord(td, &psc->pts_outpoll);
 416                 if (events & (POLLOUT|POLLWRNORM))
 417                         selrecord(td, &psc->pts_inpoll);
 418         }
 419
 420         tty_unlock(tp);
 421
 422         return (revents);
 423 }
 424
 425 static int
 426 ptsdev_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
 427     struct thread *td)
 428 {
 429         struct tty *tp = fp->f_data;
 430 #ifdef PTS_EXTERNAL
 431         struct pts_softc *psc = tty_softc(tp);
 432 #endif /* PTS_EXTERNAL */
 433
 434         /*
 435          * According to POSIX, we must implement an fstat(). This also
 436          * makes this implementation compatible with Linux binaries,
 437          * because Linux calls fstat() on the pseudo-terminal master to
 438          * obtain st_rdev.
 439          *
 440          * XXX: POSIX also mentions we must fill in st_dev, st_atime,
 441          * st_ctime and st_mtime, but how?
 442          */
 443
 444         bzero(sb, sizeof *sb);
 445 #ifdef PTS_EXTERNAL
 446         if (psc->pts_cdev != NULL)
 447                 sb->st_ino = sb->st_rdev = dev2udev(psc->pts_cdev);
 448         else
 449 #endif /* PTS_EXTERNAL */
 450                 sb->st_ino = sb->st_rdev = tty_udev(tp);
 451         sb->st_mode = S_IFCHR;
 452         sb->st_uid = tp->t_dev->si_cred->cr_ruid;
 453         sb->st_gid = GID_TTY;
 454
 455         return (0);
 456 }
 457
 458 static int
 459 ptsdev_close(struct file *fp, struct thread *td)
 460 {
 461         struct tty *tp = fp->f_data;
 462
 463         /* Deallocate TTY device. */
 464         tty_lock(tp);
 465         tty_rel_gone(tp);
 466
 467         return (0);
 468 }
 469
 470 static struct fileops ptsdev_ops = {
 471         .fo_read        = ptsdev_read,
 472         .fo_write       = ptsdev_write,
 473         .fo_ioctl       = ptsdev_ioctl,
 474         .fo_poll        = ptsdev_poll,
 475         .fo_stat        = ptsdev_stat,
 476         .fo_close       = ptsdev_close,
 477         .fo_flags       = DFLAG_PASSABLE,
 478 };
 479
 480 /*
 481  * Driver-side hooks.
 482  */
 483
 484 static void
 485 ptsdrv_outwakeup(struct tty *tp)
 486 {
 487         struct pts_softc *psc = tty_softc(tp);
 488
 489         cv_broadcast(&psc->pts_outwait);
 490         selwakeup(&psc->pts_outpoll);
 491 }
 492
 493 static void
 494 ptsdrv_inwakeup(struct tty *tp)
 495 {
 496         struct pts_softc *psc = tty_softc(tp);
 497
 498         cv_broadcast(&psc->pts_inwait);
 499         selwakeup(&psc->pts_inpoll);
 500 }
 501
 502 static void
 503 ptsdrv_close(struct tty *tp)
 504 {
 505
 506         /* Wake up any blocked readers/writers. */
 507         ptsdrv_outwakeup(tp);
 508         ptsdrv_inwakeup(tp);
 509 }
 510
 511 static void
 512 ptsdrv_pktnotify(struct tty *tp, char event)
 513 {
 514         struct pts_softc *psc = tty_softc(tp);
 515
 516         /*
 517          * Clear conflicting flags.
 518          */
 519
 520         switch (event) {
 521         case TIOCPKT_STOP:
 522                 psc->pts_pkt &= ~TIOCPKT_START;
 523                 break;
 524         case TIOCPKT_START:
 525                 psc->pts_pkt &= ~TIOCPKT_STOP;
 526                 break;
 527         case TIOCPKT_NOSTOP:
 528                 psc->pts_pkt &= ~TIOCPKT_DOSTOP;
 529                 break;
 530         case TIOCPKT_DOSTOP:
 531                 psc->pts_pkt &= ~TIOCPKT_NOSTOP;
 532                 break;
 533         }
 534
 535         psc->pts_pkt |= event;
 536         ptsdrv_outwakeup(tp);
 537 }
 538
 539 static void
 540 ptsdrv_free(void *softc)
 541 {
 542         struct pts_softc *psc = softc;
 543
 544         /* Make device number available again. */
 545         if (psc->pts_unit >= 0)
 546                 free_unr(pts_pool, psc->pts_unit);
 547
 548         chgptscnt(psc->pts_uidinfo, -1, 0);
 549         uifree(psc->pts_uidinfo);
 550
 551 #ifdef PTS_EXTERNAL
 552         /* Destroy master device as well. */
 553         if (psc->pts_cdev != NULL)
 554                 destroy_dev_sched(psc->pts_cdev);
 555 #endif /* PTS_EXTERNAL */
 556
 557         free(psc, M_PTS);
 558 }
 559
 560 static struct ttydevsw pts_class = {
 561         .tsw_flags      = TF_NOPREFIX,
 562         .tsw_outwakeup  = ptsdrv_outwakeup,
 563         .tsw_inwakeup   = ptsdrv_inwakeup,
 564         .tsw_close      = ptsdrv_close,
 565         .tsw_pktnotify  = ptsdrv_pktnotify,
 566         .tsw_free       = ptsdrv_free,
 567 };
 568
 569 static int
 570 pts_alloc(int fflags, struct thread *td, struct file *fp)
 571 {
 572         int unit, ok;
 573         struct tty *tp;
 574         struct pts_softc *psc;
 575         struct proc *p = td->td_proc;
 576         struct uidinfo *uid = td->td_ucred->cr_ruidinfo;
 577
 578         /* Resource limiting. */
 579         PROC_LOCK(p);
 580         ok = chgptscnt(uid, 1, lim_cur(p, RLIMIT_NPTS));
 581         PROC_UNLOCK(p);
 582         if (!ok)
 583                 return (EAGAIN);
 584
 585         /* Try to allocate a new pts unit number. */
 586         unit = alloc_unr(pts_pool);
 587         if (unit < 0) {
 588                 chgptscnt(uid, -1, 0);
 589                 return (EAGAIN);
 590         }
 591
 592         /* Allocate TTY and softc. */
 593         psc = malloc(sizeof(struct pts_softc), M_PTS, M_WAITOK|M_ZERO);
 594         cv_init(&psc->pts_inwait, "pts inwait");
 595         cv_init(&psc->pts_outwait, "pts outwait");
 596
 597         psc->pts_unit = unit;
 598         psc->pts_uidinfo = uid;
 599         uihold(uid);
 600
 601         tp = tty_alloc(&pts_class, psc, NULL);
 602
 603         /* Expose the slave device as well. */
 604         tty_makedev(tp, td->td_ucred, "pts/%u", psc->pts_unit);
 605
 606         finit(fp, fflags, DTYPE_PTS, tp, &ptsdev_ops);
 607
 608         return (0);
 609 }
 610
 611 #ifdef PTS_EXTERNAL
 612 int
 613 pts_alloc_external(int fflags, struct thread *td, struct file *fp,
 614     struct cdev *dev, const char *name)
 615 {
 616         int ok;
 617         struct tty *tp;
 618         struct pts_softc *psc;
 619         struct proc *p = td->td_proc;
 620         struct uidinfo *uid = td->td_ucred->cr_ruidinfo;
 621
 622         /* Resource limiting. */
 623         PROC_LOCK(p);
 624         ok = chgptscnt(uid, 1, lim_cur(p, RLIMIT_NPTS));
 625         PROC_UNLOCK(p);
 626         if (!ok)
 627                 return (EAGAIN);
 628
 629         /* Allocate TTY and softc. */
 630         psc = malloc(sizeof(struct pts_softc), M_PTS, M_WAITOK|M_ZERO);
 631         cv_init(&psc->pts_inwait, "pts inwait");
 632         cv_init(&psc->pts_outwait, "pts outwait");
 633
 634         psc->pts_unit = -1;
 635         psc->pts_cdev = dev;
 636         psc->pts_uidinfo = uid;
 637         uihold(uid);
 638
 639         tp = tty_alloc(&pts_class, psc, NULL);
 640
 641         /* Expose the slave device as well. */
 642         tty_makedev(tp, td->td_ucred, "%s", name);
 643
 644         finit(fp, fflags, DTYPE_PTS, tp, &ptsdev_ops);
 645
 646         return (0);
 647 }
 648 #endif /* PTS_EXTERNAL */
 649
 650 int
 651 posix_openpt(struct thread *td, struct posix_openpt_args *uap)
 652 {
 653         int error, fd;
 654         struct file *fp;
 655
 656         /*
 657          * POSIX states it's unspecified when other flags are passed. We
 658          * don't allow this.
 659          */
 660         if (uap->flags & ~(O_RDWR|O_NOCTTY))
 661                 return (EINVAL);
 662
 663         error = falloc(td, &fp, &fd);
 664         if (error)
 665                 return (error);
 666
 667         /* Allocate the actual pseudo-TTY. */
 668         error = pts_alloc(FFLAGS(uap->flags & O_ACCMODE), td, fp);
 669         if (error != 0) {
 670                 fdclose(td->td_proc->p_fd, fp, fd, td);
 671                 return (error);
 672         }
 673
 674         /* Pass it back to userspace. */
 675         td->td_retval[0] = fd;
 676         fdrop(fp, td);
 677
 678         return (0);
 679 }
 680
 681 #if defined(PTS_COMPAT) || defined(PTS_LINUX)
 682 static int
 683 ptmx_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
 684 {
 685         int error;
 686
 687         error = pts_alloc(fflags & (FREAD|FWRITE), td, fp);
 688         if (error != 0)
 689                 return (error);
 690
 691         return (0);
 692 }
 693
 694 static struct cdevsw ptmx_cdevsw = {
 695         .d_version      = D_VERSION,
 696         .d_fdopen       = ptmx_fdopen,
 697         .d_name         = "ptmx",
 698 };
 699 #endif /* PTS_COMPAT || PTS_LINUX */
 700
 701 static void
 702 pts_init(void *unused)
 703 {
 704
 705         pts_pool = new_unrhdr(0, MAXPTSDEVS, NULL);
 706 #if defined(PTS_COMPAT) || defined(PTS_LINUX)
 707         make_dev(&ptmx_cdevsw, 0, UID_ROOT, GID_WHEEL, 0666, "ptmx");
 708 #endif /* PTS_COMPAT || PTS_LINUX */
 709 }
 710
 711 SYSINIT(pts, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, pts_init, NULL);