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 vn_unlock(ttyvp); 112 vdrop(ttyvp); 113 goto retry; 114 } 115 error = VOP_OPEN(ttyvp, FREAD|FWRITE, ap->a_cred, NULL); 116 117 /* 118 * Race against ctty close or change. This case has been validated 119 * and occurs every so often during synth builds. 120 */ 121 if (ttyvp != cttyvp(p) || (ttyvp->v_flag & VCTTYISOPEN)) { 122 if (error == 0) 123 VOP_CLOSE(ttyvp, FREAD|FWRITE, NULL); 124 vn_unlock(ttyvp); 125 vdrop(ttyvp); 126 goto retry; 127 } 128 if (error == 0) 129 vsetflags(ttyvp, VCTTYISOPEN); 130 vn_unlock(ttyvp); 131 vdrop(ttyvp); 132 return(error); 133 } 134 135 /* 136 * This closes /dev/tty. Because multiple opens of /dev/tty only 137 * generate a single open to the actual tty, the file modes are 138 * locked to FREAD|FWRITE. 139 */ 140 static int 141 cttyclose(struct dev_close_args *ap) 142 { 143 struct proc *p = curproc; 144 struct vnode *ttyvp; 145 int error; 146 147 KKASSERT(p); 148 retry: 149 /* 150 * The tty may have been TIOCNOTTY'd, don't return an 151 * error on close. We just have nothing to do. 152 */ 153 if ((ttyvp = cttyvp(p)) == NULL) 154 return(0); 155 if (ttyvp->v_flag & VCTTYISOPEN) { 156 /* 157 * Avoid a nasty race if we block while getting the lock. 158 */ 159 vref(ttyvp); 160 error = vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY | 161 LK_FAILRECLAIM); 162 if (error) { 163 vrele(ttyvp); 164 goto retry; 165 } 166 if (ttyvp != cttyvp(p) || (ttyvp->v_flag & VCTTYISOPEN) == 0) { 167 kprintf("Warning: cttyclose: race avoided\n"); 168 vn_unlock(ttyvp); 169 vrele(ttyvp); 170 goto retry; 171 } 172 vclrflags(ttyvp, VCTTYISOPEN); 173 error = VOP_CLOSE(ttyvp, FREAD|FWRITE, NULL); 174 vn_unlock(ttyvp); 175 vrele(ttyvp); 176 } else { 177 error = 0; 178 } 179 return(error); 180 } 181 182 /* 183 * Read from the controlling terminal (/dev/tty). The tty is refed as 184 * of the cttyvp(), but the ref can get ripped out from under us if 185 * the controlling terminal is revoked while we are blocked on the lock, 186 * so use vget() instead of vn_lock(). 187 */ 188 static int 189 cttyread(struct dev_read_args *ap) 190 { 191 struct proc *p = curproc; 192 struct vnode *ttyvp; 193 int error; 194 195 KKASSERT(p); 196 ttyvp = cttyvp(p); 197 if (ttyvp == NULL) 198 return (EIO); 199 if ((error = vget(ttyvp, LK_EXCLUSIVE | LK_RETRY)) == 0) { 200 error = VOP_READ(ttyvp, ap->a_uio, ap->a_ioflag, NOCRED); 201 vput(ttyvp); 202 } 203 return (error); 204 } 205 206 /* 207 * Read from the controlling terminal (/dev/tty). The tty is refed as 208 * of the cttyvp(), but the ref can get ripped out from under us if 209 * the controlling terminal is revoked while we are blocked on the lock, 210 * so use vget() instead of vn_lock(). 211 */ 212 static int 213 cttywrite(struct dev_write_args *ap) 214 { 215 struct proc *p = curproc; 216 struct vnode *ttyvp; 217 int error; 218 219 KKASSERT(p); 220 ttyvp = cttyvp(p); 221 if (ttyvp == NULL) 222 return (EIO); 223 if ((error = vget(ttyvp, LK_EXCLUSIVE | LK_RETRY)) == 0) { 224 error = VOP_WRITE(ttyvp, ap->a_uio, ap->a_ioflag, NOCRED); 225 vput(ttyvp); 226 } 227 return (error); 228 } 229 230 /*ARGSUSED*/ 231 static int 232 cttyioctl(struct dev_ioctl_args *ap) 233 { 234 struct vnode *ttyvp; 235 struct proc *p = curproc; 236 237 KKASSERT(p); 238 lwkt_gettoken(&p->p_token); 239 ttyvp = cttyvp(p); 240 if (ttyvp == NULL) { 241 lwkt_reltoken(&p->p_token); 242 return (EIO); 243 } 244 /* 245 * Don't allow controlling tty to be set to the controlling tty 246 * (infinite recursion). 247 */ 248 if (ap->a_cmd == TIOCSCTTY) { 249 lwkt_reltoken(&p->p_token); 250 return EINVAL; 251 } 252 if (ap->a_cmd == TIOCNOTTY) { 253 if (!SESS_LEADER(p)) { 254 p->p_flags &= ~P_CONTROLT; 255 lwkt_reltoken(&p->p_token); 256 return (0); 257 } else { 258 lwkt_reltoken(&p->p_token); 259 return (EINVAL); 260 } 261 } 262 lwkt_reltoken(&p->p_token); 263 264 return (VOP_IOCTL(ttyvp, ap->a_cmd, ap->a_data, ap->a_fflag, 265 ap->a_cred, ap->a_sysmsg)); 266 } 267 268 static struct filterops cttyfiltops_read = 269 { FILTEROP_ISFD | FILTEROP_MPSAFE, NULL, 270 cttyfilt_detach, cttyfilt_read }; 271 static struct filterops cttyfiltops_write = 272 { FILTEROP_ISFD | FILTEROP_MPSAFE, NULL, 273 cttyfilt_detach, cttyfilt_write }; 274 275 static int 276 cttykqfilter(struct dev_kqfilter_args *ap) 277 { 278 cdev_t dev = ap->a_head.a_dev; 279 struct proc *p = curproc; 280 struct knote *kn = ap->a_kn; 281 struct vnode *ttyvp; 282 283 KKASSERT(p); 284 ttyvp = cttyvp(p); 285 286 if (ttyvp != NULL) 287 return (VOP_KQFILTER(ttyvp, kn)); 288 289 ap->a_result = 0; 290 291 switch (kn->kn_filter) { 292 case EVFILT_READ: 293 kn->kn_fop = &cttyfiltops_read; 294 kn->kn_hook = (caddr_t)dev; 295 break; 296 case EVFILT_WRITE: 297 kn->kn_fop = &cttyfiltops_write; 298 kn->kn_hook = (caddr_t)dev; 299 break; 300 default: 301 ap->a_result = EOPNOTSUPP; 302 return (0); 303 } 304 305 return (0); 306 } 307 308 static void 309 cttyfilt_detach(struct knote *kn) {} 310 311 static int 312 cttyfilt_read(struct knote *kn, long hint) 313 { 314 cdev_t dev = (cdev_t)kn->kn_hook; 315 316 if (seltrue(dev, POLLIN | POLLRDNORM)) 317 return (1); 318 319 return (0); 320 } 321 322 static int 323 cttyfilt_write(struct knote *kn, long hint) 324 { 325 cdev_t dev = (cdev_t)kn->kn_hook; 326 327 if (seltrue(dev, POLLOUT | POLLWRNORM)) 328 return (1); 329 330 return (0); 331 } 332 333 static void 334 ctty_drvinit(void *unused __unused) 335 { 336 make_dev(&ctty_ops, 0, 0, 0, 0666, "tty"); 337 } 338 339 SYSINIT(cttydev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR, 340 ctty_drvinit, NULL); 341