bsd/kern/tty_tty.c

   1 /*
   2  * Copyright (c) 1997-2013 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*-
  29  * Copyright (c) 1982, 1986, 1991, 1993
  30  *      The Regents of the University of California.  All rights reserved.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  *
  60  *      @(#)tty_tty.c   8.2 (Berkeley) 9/23/93
  61  */
  62
  63 /*
  64  * Indirect driver for controlling tty.
  65  */
  66 #include <sys/param.h>
  67 #include <sys/systm.h>
  68 #include <sys/conf.h>
  69 #include <sys/ioctl.h>
  70 #include <sys/proc_internal.h>
  71 #include <sys/tty.h>
  72 #include <sys/vnode_internal.h>
  73 #include <sys/file_internal.h>
  74 #include <sys/kauth.h>
  75
  76 /* Forward declarations for cdevsw[] entry */
  77 /* XXX we should consider making these static */
  78 int cttyopen(dev_t dev, int flag, int mode, proc_t p);
  79 int cttyread(dev_t dev, struct uio *uio, int flag);
  80 int cttywrite(dev_t dev, struct uio *uio, int flag);
  81 int cttyioctl(dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p);
  82 int cttyselect(dev_t dev, int flag, void* wql, proc_t p);
  83 static vnode_t cttyvp(proc_t p);
  84
  85 int
  86 cttyopen(dev_t dev, int flag, __unused int mode, proc_t p)
  87 {
  88         vnode_t ttyvp = cttyvp(p);
  89         struct vfs_context context;
  90         int error = 0;
  91         int cttyflag, doclose = 0;
  92         struct session *sessp;
  93
  94         if (ttyvp == NULL) {
  95                 return ENXIO;
  96         }
  97
  98         context.vc_thread = current_thread();
  99         context.vc_ucred = kauth_cred_proc_ref(p);
 100
 101         sessp = proc_session(p);
 102         session_lock(sessp);
 103         cttyflag = sessp->s_flags & S_CTTYREF;
 104         session_unlock(sessp);
 105
 106         /*
 107          * A little hack--this device, used by many processes,
 108          * happens to do an open on another device, which can
 109          * cause unhappiness if the second-level open blocks indefinitely
 110          * (as could be the case if the master side has hung up).  Since
 111          * we know that this driver doesn't care about the serializing
 112          * opens and closes, we can drop the lock. To avoid opencount leak,
 113          * open the vnode only for the first time.
 114          */
 115         if (cttyflag == 0) {
 116                 devsw_unlock(dev, S_IFCHR);
 117                 error = VNOP_OPEN(ttyvp, flag, &context);
 118                 devsw_lock(dev, S_IFCHR);
 119
 120                 if (error) {
 121                         goto out;
 122                 }
 123
 124                 /*
 125                  * If S_CTTYREF is set, some other thread did an open
 126                  * and was able to set the flag, now perform a close, else
 127                  * set the flag.
 128                  */
 129                 session_lock(sessp);
 130                 if (cttyflag == (sessp->s_flags & S_CTTYREF)) {
 131                         sessp->s_flags |= S_CTTYREF;
 132                 } else {
 133                         doclose = 1;
 134                 }
 135                 session_unlock(sessp);
 136
 137                 /*
 138                  * We have to take a reference here to make sure a close
 139                  * gets called during revoke. Note that once a controlling
 140                  * tty gets opened by this driver, the only way close will
 141                  * get called is when the session leader , whose controlling
 142                  * tty is ttyvp, exits and vnode is revoked. We cannot
 143                  * redirect close from this driver because underlying controlling
 144                  * terminal might change and close may get redirected to a
 145                  * wrong vnode causing panic.
 146                  */
 147                 if (doclose) {
 148                         devsw_unlock(dev, S_IFCHR);
 149                         VNOP_CLOSE(ttyvp, flag, &context);
 150                         devsw_lock(dev, S_IFCHR);
 151                 } else {
 152                         error = vnode_ref(ttyvp);
 153                 }
 154         }
 155 out:
 156         session_rele(sessp);
 157
 158         vnode_put(ttyvp);
 159         kauth_cred_unref(&context.vc_ucred);
 160
 161         return error;
 162 }
 163
 164 int
 165 cttyread(__unused dev_t dev, struct uio *uio, int flag)
 166 {
 167         vnode_t ttyvp = cttyvp(current_proc());
 168         struct vfs_context context;
 169         int error;
 170
 171         if (ttyvp == NULL) {
 172                 return EIO;
 173         }
 174
 175         context.vc_thread = current_thread();
 176         context.vc_ucred = NOCRED;
 177
 178         error = VNOP_READ(ttyvp, uio, flag, &context);
 179         vnode_put(ttyvp);
 180
 181         return error;
 182 }
 183
 184 int
 185 cttywrite(__unused dev_t dev, struct uio *uio, int flag)
 186 {
 187         vnode_t ttyvp = cttyvp(current_proc());
 188         struct vfs_context context;
 189         int error;
 190
 191         if (ttyvp == NULL) {
 192                 return EIO;
 193         }
 194
 195         context.vc_thread = current_thread();
 196         context.vc_ucred = NOCRED;
 197
 198         error = VNOP_WRITE(ttyvp, uio, flag, &context);
 199         vnode_put(ttyvp);
 200
 201         return error;
 202 }
 203
 204 int
 205 cttyioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p)
 206 {
 207         vnode_t ttyvp = cttyvp(current_proc());
 208         struct vfs_context context;
 209         struct session *sessp;
 210         int error = 0;
 211
 212         if (ttyvp == NULL) {
 213                 return EIO;
 214         }
 215         if (cmd == TIOCSCTTY) {  /* don't allow controlling tty to be set    */
 216                 error = EINVAL; /* to controlling tty -- infinite recursion */
 217                 goto out;
 218         }
 219         if (cmd == TIOCNOTTY) {
 220                 sessp = proc_session(p);
 221                 if (!SESS_LEADER(p, sessp)) {
 222                         OSBitAndAtomic(~((uint32_t)P_CONTROLT), &p->p_flag);
 223                         if (sessp != SESSION_NULL) {
 224                                 session_rele(sessp);
 225                         }
 226                         error = 0;
 227                         goto out;
 228                 } else {
 229                         if (sessp != SESSION_NULL) {
 230                                 session_rele(sessp);
 231                         }
 232                         error = EINVAL;
 233                         goto out;
 234                 }
 235         }
 236         context.vc_thread = current_thread();
 237         context.vc_ucred = NOCRED;
 238
 239         error = VNOP_IOCTL(ttyvp, cmd, addr, flag, &context);
 240 out:
 241         vnode_put(ttyvp);
 242         return error;
 243 }
 244
 245 int
 246 cttyselect(__unused dev_t dev, int flag, void* wql, __unused proc_t p)
 247 {
 248         vnode_t ttyvp = cttyvp(current_proc());
 249         struct vfs_context context;
 250         int error;
 251
 252         context.vc_thread = current_thread();
 253         context.vc_ucred = NOCRED;
 254
 255         if (ttyvp == NULL) {
 256                 return 1;     /* try operation to get EOF/failure */
 257         }
 258         error = VNOP_SELECT(ttyvp, flag, FREAD | FWRITE, wql, &context);
 259         vnode_put(ttyvp);
 260         return error;
 261 }
 262
 263 /* This returns vnode with ioref */
 264 static vnode_t
 265 cttyvp(proc_t p)
 266 {
 267         vnode_t vp;
 268         int vid;
 269         struct session *sessp;
 270
 271         sessp = proc_session(p);
 272
 273         session_lock(sessp);
 274         vp = (p->p_flag & P_CONTROLT ? sessp->s_ttyvp : NULLVP);
 275         vid = sessp->s_ttyvid;
 276         session_unlock(sessp);
 277
 278         session_rele(sessp);
 279
 280         if (vp != NULLVP) {
 281                 /* cannot get an IO reference, return NULLVP */
 282                 if (vnode_getwithvid(vp, vid) != 0) {
 283                         vp = NULLVP;
 284                 }
 285         }
 286         return vp;
 287 }