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
cttyopen(struct dev_open_args * ap)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
cttyclose(struct dev_close_args * ap)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
cttyread(struct dev_read_args * ap)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
cttywrite(struct dev_write_args * ap)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
cttyioctl(struct dev_ioctl_args * ap)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
cttykqfilter(struct dev_kqfilter_args * ap)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
cttyfilt_detach(struct knote * kn)309 cttyfilt_detach(struct knote *kn) {}
310
311 static int
cttyfilt_read(struct knote * kn,long hint)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
cttyfilt_write(struct knote * kn,long hint)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
ctty_drvinit(void * unused __unused)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