sys/kern/tty_tty.c

   1 /*-
   2  * (MPSAFE)
   3  *
   4  * Copyright (c) 1982, 1986, 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)tty_tty.c   8.2 (Berkeley) 9/23/93
  32  * $FreeBSD: src/sys/kern/tty_tty.c,v 1.30 1999/09/25 18:24:24 phk Exp $
  33  */
  34
  35 /*
  36  * Indirect driver for controlling tty.
  37  */
  38
  39 #include <sys/param.h>
  40 #include <sys/systm.h>
  41 #include <sys/conf.h>
  42 #include <sys/device.h>
  43 #include <sys/lock.h>
  44 #include <sys/fcntl.h>
  45 #include <sys/proc.h>
  46 #include <sys/ttycom.h>
  47 #include <sys/vnode.h>
  48 #include <sys/kernel.h>
  49 #include <sys/poll.h> /* XXX: poll args used in KQ filters */
  50 #include <sys/event.h>
  51
  52 static  d_open_t        cttyopen;
  53 static  d_close_t       cttyclose;
  54 static  d_read_t        cttyread;
  55 static  d_write_t       cttywrite;
  56 static  d_ioctl_t       cttyioctl;
  57 static  d_kqfilter_t    cttykqfilter;
  58
  59 static void cttyfilt_detach(struct knote *);
  60 static int cttyfilt_read(struct knote *, long);
  61 static int cttyfilt_write(struct knote *, long);
  62
  63 #define CDEV_MAJOR      1
  64 static struct dev_ops ctty_ops = {
  65         { "ctty", 0, D_TTY | D_MPSAFE },
  66         .d_open =       cttyopen,
  67         .d_close =      cttyclose,
  68         .d_read =       cttyread,
  69         .d_write =      cttywrite,
  70         .d_ioctl =      cttyioctl,
  71         .d_kqfilter =   cttykqfilter
  72 };
  73
  74 #define cttyvp(p) (((p)->p_flags & P_CONTROLT) ? \
  75                         (p)->p_session->s_ttyvp : NULL)
  76
  77 /*
  78  * This opens /dev/tty.  Because multiple opens of /dev/tty only
  79  * generate a single open to the actual tty, the file modes are
  80  * locked to FREAD|FWRITE.
  81  */
  82 static  int
  83 cttyopen(struct dev_open_args *ap)
  84 {
  85         struct proc *p = curproc;
  86         struct vnode *ttyvp;
  87         int error;
  88
  89         KKASSERT(p);
  90 retry:
  91         if ((ttyvp = cttyvp(p)) == NULL)
  92                 return (ENXIO);
  93         if (ttyvp->v_flag & VCTTYISOPEN)
  94                 return (0);
  95
  96         /*
  97          * Messy interlock, don't let the vnode go away while we try to
  98          * lock it and check for race after we might have blocked.
  99          *
 100          * WARNING! The device open (devfs_spec_open()) temporarily
 101          *          releases the vnode lock on ttyvp when issuing the
 102          *          dev_dopen(), which means that the VCTTYISOPEn flag
 103          *          can race during the VOP_OPEN().
 104          *
 105          *          If something does race we have to undo our potentially
 106          *          extra open.
 107          */
 108         vhold(ttyvp);
 109         vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY);
 110         if (ttyvp != cttyvp(p) || (ttyvp->v_flag & VCTTYISOPEN)) {
 111                 kprintf("Warning: cttyopen: race-1 avoided\n");
 112                 vn_unlock(ttyvp);
 113                 vdrop(ttyvp);
 114                 goto retry;
 115         }
 116         error = VOP_OPEN(ttyvp, FREAD|FWRITE, ap->a_cred, NULL);
 117         if (ttyvp != cttyvp(p) || (ttyvp->v_flag & VCTTYISOPEN)) {
 118                 kprintf("Warning: cttyopen: race-2 avoided\n");
 119                 if (error == 0)
 120                         VOP_CLOSE(ttyvp, FREAD|FWRITE, NULL);
 121                 vn_unlock(ttyvp);
 122                 vdrop(ttyvp);
 123                 goto retry;
 124         }
 125         if (error == 0)
 126                 vsetflags(ttyvp, VCTTYISOPEN);
 127         vn_unlock(ttyvp);
 128         vdrop(ttyvp);
 129         return(error);
 130 }
 131
 132 /*
 133  * This closes /dev/tty.  Because multiple opens of /dev/tty only
 134  * generate a single open to the actual tty, the file modes are
 135  * locked to FREAD|FWRITE.
 136  */
 137 static int
 138 cttyclose(struct dev_close_args *ap)
 139 {
 140         struct proc *p = curproc;
 141         struct vnode *ttyvp;
 142         int error;
 143
 144         KKASSERT(p);
 145 retry:
 146         /*
 147          * The tty may have been TIOCNOTTY'd, don't return an
 148          * error on close.  We just have nothing to do.
 149          */
 150         if ((ttyvp = cttyvp(p)) == NULL)
 151                 return(0);
 152         if (ttyvp->v_flag & VCTTYISOPEN) {
 153                 /*
 154                  * Avoid a nasty race if we block while getting the lock.
 155                  */
 156                 vref(ttyvp);
 157                 error = vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY |
 158                                        LK_FAILRECLAIM);
 159                 if (error) {
 160                         vrele(ttyvp);
 161                         goto retry;
 162                 }
 163                 if (ttyvp != cttyvp(p) || (ttyvp->v_flag & VCTTYISOPEN) == 0) {
 164                         kprintf("Warning: cttyclose: race avoided\n");
 165                         vn_unlock(ttyvp);
 166                         vrele(ttyvp);
 167                         goto retry;
 168                 }
 169                 vclrflags(ttyvp, VCTTYISOPEN);
 170                 error = VOP_CLOSE(ttyvp, FREAD|FWRITE, NULL);
 171                 vn_unlock(ttyvp);
 172                 vrele(ttyvp);
 173         } else {
 174                 error = 0;
 175         }
 176         return(error);
 177 }
 178
 179 /*
 180  * Read from the controlling terminal (/dev/tty).  The tty is refed as
 181  * of the cttyvp(), but the ref can get ripped out from under us if
 182  * the controlling terminal is revoked while we are blocked on the lock,
 183  * so use vget() instead of vn_lock().
 184  */
 185 static  int
 186 cttyread(struct dev_read_args *ap)
 187 {
 188         struct proc *p = curproc;
 189         struct vnode *ttyvp;
 190         int error;
 191
 192         KKASSERT(p);
 193         ttyvp = cttyvp(p);
 194         if (ttyvp == NULL)
 195                 return (EIO);
 196         if ((error = vget(ttyvp, LK_EXCLUSIVE | LK_RETRY)) == 0) {
 197                 error = VOP_READ(ttyvp, ap->a_uio, ap->a_ioflag, NOCRED);
 198                 vput(ttyvp);
 199         }
 200         return (error);
 201 }
 202
 203 /*
 204  * Read from the controlling terminal (/dev/tty).  The tty is refed as
 205  * of the cttyvp(), but the ref can get ripped out from under us if
 206  * the controlling terminal is revoked while we are blocked on the lock,
 207  * so use vget() instead of vn_lock().
 208  */
 209 static  int
 210 cttywrite(struct dev_write_args *ap)
 211 {
 212         struct proc *p = curproc;
 213         struct vnode *ttyvp;
 214         int error;
 215
 216         KKASSERT(p);
 217         ttyvp = cttyvp(p);
 218         if (ttyvp == NULL)
 219                 return (EIO);
 220         if ((error = vget(ttyvp, LK_EXCLUSIVE | LK_RETRY)) == 0) {
 221                 error = VOP_WRITE(ttyvp, ap->a_uio, ap->a_ioflag, NOCRED);
 222                 vput(ttyvp);
 223         }
 224         return (error);
 225 }
 226
 227 /*ARGSUSED*/
 228 static  int
 229 cttyioctl(struct dev_ioctl_args *ap)
 230 {
 231         struct vnode *ttyvp;
 232         struct proc *p = curproc;
 233
 234         KKASSERT(p);
 235         lwkt_gettoken(&p->p_token);
 236         ttyvp = cttyvp(p);
 237         if (ttyvp == NULL) {
 238                 lwkt_reltoken(&p->p_token);
 239                 return (EIO);
 240         }
 241         /*
 242          * Don't allow controlling tty to be set to the controlling tty
 243          * (infinite recursion).
 244          */
 245         if (ap->a_cmd == TIOCSCTTY) {
 246                 lwkt_reltoken(&p->p_token);
 247                 return EINVAL;
 248         }
 249         if (ap->a_cmd == TIOCNOTTY) {
 250                 if (!SESS_LEADER(p)) {
 251                         p->p_flags &= ~P_CONTROLT;
 252                         lwkt_reltoken(&p->p_token);
 253                         return (0);
 254                 } else {
 255                         lwkt_reltoken(&p->p_token);
 256                         return (EINVAL);
 257                 }
 258         }
 259         lwkt_reltoken(&p->p_token);
 260
 261         return (VOP_IOCTL(ttyvp, ap->a_cmd, ap->a_data, ap->a_fflag,
 262                           ap->a_cred, ap->a_sysmsg));
 263 }
 264
 265 static struct filterops cttyfiltops_read =
 266         { FILTEROP_ISFD | FILTEROP_MPSAFE, NULL,
 267           cttyfilt_detach, cttyfilt_read };
 268 static struct filterops cttyfiltops_write =
 269         { FILTEROP_ISFD | FILTEROP_MPSAFE, NULL,
 270           cttyfilt_detach, cttyfilt_write };
 271
 272 static int
 273 cttykqfilter(struct dev_kqfilter_args *ap)
 274 {
 275         cdev_t dev = ap->a_head.a_dev;
 276         struct proc *p = curproc;
 277         struct knote *kn = ap->a_kn;
 278         struct vnode *ttyvp;
 279
 280         KKASSERT(p);
 281         ttyvp = cttyvp(p);
 282
 283         if (ttyvp != NULL)
 284                 return (VOP_KQFILTER(ttyvp, kn));
 285
 286         ap->a_result = 0;
 287
 288         switch (kn->kn_filter) {
 289         case EVFILT_READ:
 290                 kn->kn_fop = &cttyfiltops_read;
 291                 kn->kn_hook = (caddr_t)dev;
 292                 break;
 293         case EVFILT_WRITE:
 294                 kn->kn_fop = &cttyfiltops_write;
 295                 kn->kn_hook = (caddr_t)dev;
 296                 break;
 297         default:
 298                 ap->a_result = EOPNOTSUPP;
 299                 return (0);
 300         }
 301
 302         return (0);
 303 }
 304
 305 static void
 306 cttyfilt_detach(struct knote *kn) {}
 307
 308 static int
 309 cttyfilt_read(struct knote *kn, long hint)
 310 {
 311         cdev_t dev = (cdev_t)kn->kn_hook;
 312
 313         if (seltrue(dev, POLLIN | POLLRDNORM))
 314                 return (1);
 315
 316         return (0);
 317 }
 318
 319 static int
 320 cttyfilt_write(struct knote *kn, long hint)
 321 {
 322         cdev_t dev = (cdev_t)kn->kn_hook;
 323
 324         if (seltrue(dev, POLLOUT | POLLWRNORM))
 325                 return (1);
 326
 327         return (0);
 328 }
 329
 330 static void
 331 ctty_drvinit(void *unused __unused)
 332 {
 333         make_dev(&ctty_ops, 0, 0, 0, 0666, "tty");
 334 }
 335
 336 SYSINIT(cttydev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR,
 337         ctty_drvinit, NULL);