sys/kern/tty_pty.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 <sys/param.h>
  34 #include <sys/conf.h>
  35 #include <sys/eventhandler.h>
  36 #include <sys/fcntl.h>
  37 #include <sys/kernel.h>
  38 #include <sys/proc.h>
  39 #include <sys/sysctl.h>
  40 #include <sys/systm.h>
  41 #include <sys/tty.h>
  42
  43 /*
  44  * This driver implements a BSD-style compatibility naming scheme for
  45  * the pts(4) driver. We just call into pts(4) to create the actual PTY.
  46  * To make sure we don't use the same PTY multiple times, we abuse
  47  * si_drv1 inside the cdev to mark whether the PTY is in use.
  48  */
  49
  50 static unsigned int pty_warningcnt = 10;
  51 SYSCTL_UINT(_kern, OID_AUTO, tty_pty_warningcnt, CTLFLAG_RW,
  52         &pty_warningcnt, 0,
  53         "Warnings that will be triggered upon PTY allocation");
  54
  55 static int
  56 ptydev_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
  57 {
  58         int u, error;
  59         char name[] = "ttyXX";
  60
  61         if (!atomic_cmpset_ptr((uintptr_t *)&dev->si_drv1, 0, 1))
  62                 return (EBUSY);
  63
  64         /* Generate device name and create PTY. */
  65         u = dev2unit(dev);
  66         name[3] = u >> 8;
  67         name[4] = u;
  68
  69         error = pts_alloc_external(fflags & (FREAD|FWRITE), td, fp, dev, name);
  70         if (error != 0) {
  71                 destroy_dev_sched(dev);
  72                 return (error);
  73         }
  74
  75         /* Raise a warning when a legacy PTY has been allocated. */
  76         if (pty_warningcnt > 0) {
  77                 pty_warningcnt--;
  78                 printf("pid %d (%s) is using legacy pty devices%s\n",
  79                     td->td_proc->p_pid, td->td_name,
  80                     pty_warningcnt ? "" : " - not logging anymore");
  81         }
  82
  83         return (0);
  84 }
  85
  86 static struct cdevsw ptydev_cdevsw = {
  87         .d_version      = D_VERSION,
  88         .d_fdopen       = ptydev_fdopen,
  89         .d_name         = "ptydev",
  90 };
  91
  92 static void
  93 pty_clone(void *arg, struct ucred *cr, char *name, int namelen,
  94     struct cdev **dev)
  95 {
  96         int u;
  97
  98         /* Cloning is already satisfied. */
  99         if (*dev != NULL)
 100                 return;
 101
 102         /* Only catch /dev/ptyXX. */
 103         if (namelen != 5 || bcmp(name, "pty", 3) != 0)
 104                 return;
 105
 106         /* Only catch /dev/pty[l-sL-S]X. */
 107         if (!(name[3] >= 'l' && name[3] <= 's') &&
 108             !(name[3] >= 'L' && name[3] <= 'S'))
 109                 return;
 110
 111         /* Only catch /dev/pty[l-sL-S][0-9a-v]. */
 112         if (!(name[4] >= '0' && name[4] <= '9') &&
 113             !(name[4] >= 'a' && name[4] <= 'v'))
 114                 return;
 115
 116         /* Create the controller device node. */
 117         u = (unsigned int)name[3] << 8 | name[4];
 118         *dev = make_dev_credf(MAKEDEV_REF, &ptydev_cdevsw, u,
 119             NULL, UID_ROOT, GID_WHEEL, 0666, name);
 120 }
 121
 122 static void
 123 pty_init(void *unused)
 124 {
 125
 126         EVENTHANDLER_REGISTER(dev_clone, pty_clone, 0, 1000);
 127 }
 128
 129 SYSINIT(pty, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, pty_init, NULL);