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 }, 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, NULL, cttyfilt_detach, cttyfilt_read }; 267 static struct filterops cttyfiltops_write = 268 { FILTEROP_ISFD, NULL, cttyfilt_detach, cttyfilt_write }; 269 270 static int 271 cttykqfilter(struct dev_kqfilter_args *ap) 272 { 273 cdev_t dev = ap->a_head.a_dev; 274 struct proc *p = curproc; 275 struct knote *kn = ap->a_kn; 276 struct vnode *ttyvp; 277 278 KKASSERT(p); 279 ttyvp = cttyvp(p); 280 281 if (ttyvp != NULL) 282 return (VOP_KQFILTER(ttyvp, kn)); 283 284 ap->a_result = 0; 285 286 switch (kn->kn_filter) { 287 case EVFILT_READ: 288 kn->kn_fop = &cttyfiltops_read; 289 kn->kn_hook = (caddr_t)dev; 290 break; 291 case EVFILT_WRITE: 292 kn->kn_fop = &cttyfiltops_write; 293 kn->kn_hook = (caddr_t)dev; 294 break; 295 default: 296 ap->a_result = EOPNOTSUPP; 297 return (0); 298 } 299 300 return (0); 301 } 302 303 static void 304 cttyfilt_detach(struct knote *kn) {} 305 306 static int 307 cttyfilt_read(struct knote *kn, long hint) 308 { 309 cdev_t dev = (cdev_t)kn->kn_hook; 310 311 if (seltrue(dev, POLLIN | POLLRDNORM)) 312 return (1); 313 314 return (0); 315 } 316 317 static int 318 cttyfilt_write(struct knote *kn, long hint) 319 { 320 cdev_t dev = (cdev_t)kn->kn_hook; 321 322 if (seltrue(dev, POLLOUT | POLLWRNORM)) 323 return (1); 324 325 return (0); 326 } 327 328 static void 329 ctty_drvinit(void *unused __unused) 330 { 331 make_dev(&ctty_ops, 0, 0, 0, 0666, "tty"); 332 } 333 334 SYSINIT(cttydev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR, ctty_drvinit, 335 NULL); 336