xref: /freebsd/sys/dev/snp/snp.c (revision d0b2dbfa)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
5  * 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  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 #include <sys/param.h>
31 #include <sys/conf.h>
32 #include <sys/fcntl.h>
33 #include <sys/filio.h>
34 #include <sys/kernel.h>
35 #include <sys/malloc.h>
36 #include <sys/module.h>
37 #include <sys/poll.h>
38 #include <sys/proc.h>
39 #include <sys/snoop.h>
40 #include <sys/sx.h>
41 #include <sys/systm.h>
42 #include <sys/tty.h>
43 #include <sys/uio.h>
44 
45 static struct cdev	*snp_dev;
46 static MALLOC_DEFINE(M_SNP, "snp", "tty snoop device");
47 
48 /* XXX: should be mtx, but TTY can be locked by Giant. */
49 #if 0
50 static struct mtx	snp_register_lock;
51 MTX_SYSINIT(snp_register_lock, &snp_register_lock,
52     "tty snoop registration", MTX_DEF);
53 #define	SNP_LOCK()	mtx_lock(&snp_register_lock)
54 #define	SNP_UNLOCK()	mtx_unlock(&snp_register_lock)
55 #else
56 static struct sx	snp_register_lock;
57 SX_SYSINIT(snp_register_lock, &snp_register_lock,
58     "tty snoop registration");
59 #define	SNP_LOCK()	sx_xlock(&snp_register_lock)
60 #define	SNP_UNLOCK()	sx_xunlock(&snp_register_lock)
61 #endif
62 
63 #define	SNPGTYY_32DEV	_IOR('T', 89, uint32_t)
64 
65 /*
66  * There is no need to have a big input buffer. In most typical setups,
67  * we won't inject much data into the TTY, because users can't type
68  * really fast.
69  */
70 #define SNP_INPUT_BUFSIZE	16
71 /*
72  * The output buffer has to be really big. Right now we don't support
73  * any form of flow control, which means we lost any data we can't
74  * accept. We set the output buffer size to about twice the size of a
75  * pseudo-terminal/virtual console's output buffer.
76  */
77 #define SNP_OUTPUT_BUFSIZE	16384
78 
79 static d_open_t		snp_open;
80 static d_read_t		snp_read;
81 static d_write_t	snp_write;
82 static d_ioctl_t	snp_ioctl;
83 static d_poll_t		snp_poll;
84 
85 static struct cdevsw snp_cdevsw = {
86 	.d_version	= D_VERSION,
87 	.d_open		= snp_open,
88 	.d_read		= snp_read,
89 	.d_write	= snp_write,
90 	.d_ioctl	= snp_ioctl,
91 	.d_poll		= snp_poll,
92 	.d_name		= "snp",
93 };
94 
95 static th_getc_capture_t	snp_getc_capture;
96 
97 static struct ttyhook snp_hook = {
98 	.th_getc_capture	= snp_getc_capture,
99 };
100 
101 /*
102  * Per-instance structure.
103  *
104  * List of locks
105  * (r)	locked by snp_register_lock on assignment
106  * (t)	locked by tty_lock
107  */
108 struct snp_softc {
109 	struct tty	*snp_tty;	/* (r) TTY we're snooping. */
110 	struct ttyoutq	snp_outq;	/* (t) Output queue. */
111 	struct cv	snp_outwait;	/* (t) Output wait queue. */
112 	struct selinfo	snp_outpoll;	/* (t) Output polling. */
113 };
114 
115 static void
116 snp_dtor(void *data)
117 {
118 	struct snp_softc *ss = data;
119 	struct tty *tp;
120 
121 	tp = ss->snp_tty;
122 	if (tp != NULL) {
123 		tty_lock(tp);
124 		ttyoutq_free(&ss->snp_outq);
125 		ttyhook_unregister(tp);
126 		ss->snp_tty = NULL;
127 	}
128 
129 	cv_destroy(&ss->snp_outwait);
130 	free(ss, M_SNP);
131 }
132 
133 /*
134  * Snoop device node routines.
135  */
136 
137 static int
138 snp_open(struct cdev *dev, int flag, int mode, struct thread *td)
139 {
140 	struct snp_softc *ss;
141 
142 	/* Allocate per-snoop data. */
143 	ss = malloc(sizeof(struct snp_softc), M_SNP, M_WAITOK|M_ZERO);
144 	cv_init(&ss->snp_outwait, "snp out");
145 
146 	devfs_set_cdevpriv(ss, snp_dtor);
147 
148 	return (0);
149 }
150 
151 static int
152 snp_read(struct cdev *dev, struct uio *uio, int flag)
153 {
154 	int error, oresid = uio->uio_resid;
155 	struct snp_softc *ss;
156 	struct tty *tp;
157 
158 	if (uio->uio_resid == 0)
159 		return (0);
160 
161 	error = devfs_get_cdevpriv((void **)&ss);
162 	if (error != 0)
163 		return (error);
164 
165 	tp = ss->snp_tty;
166 	if (tp == NULL || tty_gone(tp))
167 		return (EIO);
168 
169 	tty_lock(tp);
170 	for (;;) {
171 		error = ttyoutq_read_uio(&ss->snp_outq, tp, uio);
172 		if (error != 0 || uio->uio_resid != oresid)
173 			break;
174 
175 		/* Wait for more data. */
176 		if (flag & O_NONBLOCK) {
177 			error = EWOULDBLOCK;
178 			break;
179 		}
180 		error = cv_wait_sig(&ss->snp_outwait, tty_getlock(tp));
181 		if (error != 0)
182 			break;
183 		if (tty_gone(tp)) {
184 			error = EIO;
185 			break;
186 		}
187 	}
188 	tty_unlock(tp);
189 
190 	return (error);
191 }
192 
193 static int
194 snp_write(struct cdev *dev, struct uio *uio, int flag)
195 {
196 	struct snp_softc *ss;
197 	struct tty *tp;
198 	int error, len;
199 	char in[SNP_INPUT_BUFSIZE];
200 
201 	error = devfs_get_cdevpriv((void **)&ss);
202 	if (error != 0)
203 		return (error);
204 
205 	tp = ss->snp_tty;
206 	if (tp == NULL || tty_gone(tp))
207 		return (EIO);
208 
209 	while (uio->uio_resid > 0) {
210 		/* Read new data. */
211 		len = imin(uio->uio_resid, sizeof in);
212 		error = uiomove(in, len, uio);
213 		if (error != 0)
214 			return (error);
215 
216 		tty_lock(tp);
217 
218 		/* Driver could have abandoned the TTY in the mean time. */
219 		if (tty_gone(tp)) {
220 			tty_unlock(tp);
221 			return (ENXIO);
222 		}
223 
224 		/*
225 		 * Deliver data to the TTY. Ignore errors for now,
226 		 * because we shouldn't bail out when we're running
227 		 * close to the watermarks.
228 		 */
229 		ttydisc_rint_simple(tp, in, len);
230 		ttydisc_rint_done(tp);
231 
232 		tty_unlock(tp);
233 	}
234 
235 	return (0);
236 }
237 
238 static int
239 snp_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags,
240     struct thread *td)
241 {
242 	struct snp_softc *ss;
243 	struct tty *tp;
244 	int error;
245 
246 	error = devfs_get_cdevpriv((void **)&ss);
247 	if (error != 0)
248 		return (error);
249 
250 	switch (cmd) {
251 	case SNPSTTY:
252 		/* Bind TTY to snoop instance. */
253 		SNP_LOCK();
254 		tp = ss->snp_tty;
255 		if (tp != NULL) {
256 			if (*(int *)data == -1) {
257 				tty_lock(tp);
258 				ss->snp_tty = NULL;
259 				ttyoutq_free(&ss->snp_outq);
260 				ttyhook_unregister(tp);
261 				error = 0;
262 			} else {
263 				error = EBUSY;
264 			}
265 			SNP_UNLOCK();
266 			return (error);
267 		}
268 		/*
269 		 * XXXRW / XXXJA: no capability check here.
270 		 */
271 		error = ttyhook_register(&ss->snp_tty, td->td_proc,
272 		    *(int *)data, &snp_hook, ss);
273 		SNP_UNLOCK();
274 		if (error != 0)
275 			return (error);
276 
277 		/* Now that went okay, allocate a buffer for the queue. */
278 		tp = ss->snp_tty;
279 		tty_lock(tp);
280 		ttyoutq_setsize(&ss->snp_outq, tp, SNP_OUTPUT_BUFSIZE);
281 		tty_unlock(tp);
282 
283 		return (0);
284 	case SNPGTTY:
285 		/* Obtain device number of associated TTY. */
286 		if (ss->snp_tty == NULL)
287 			*(dev_t *)data = NODEV;
288 		else
289 			*(dev_t *)data = tty_udev(ss->snp_tty);
290 		return (0);
291 	case SNPGTYY_32DEV:
292 		if (ss->snp_tty == NULL)
293 			*(uint32_t *)data = -1;
294 		else
295 			*(uint32_t *)data = tty_udev(ss->snp_tty); /* trunc */
296 		return (0);
297 	case FIONREAD:
298 		tp = ss->snp_tty;
299 		if (tp != NULL) {
300 			tty_lock(tp);
301 			if (tty_gone(tp))
302 				*(int *)data = SNP_TTYCLOSE;
303 			else
304 				*(int *)data = ttyoutq_bytesused(&ss->snp_outq);
305 			tty_unlock(tp);
306 		} else {
307 			*(int *)data = SNP_DETACH;
308 		}
309 		return (0);
310 	default:
311 		return (ENOTTY);
312 	}
313 }
314 
315 static int
316 snp_poll(struct cdev *dev, int events, struct thread *td)
317 {
318 	struct snp_softc *ss;
319 	struct tty *tp;
320 	int revents;
321 
322 	if (devfs_get_cdevpriv((void **)&ss) != 0)
323 		return (events &
324 		    (POLLHUP|POLLIN|POLLRDNORM|POLLOUT|POLLWRNORM));
325 
326 	revents = 0;
327 
328 	if (events & (POLLIN | POLLRDNORM)) {
329 		tp = ss->snp_tty;
330 		if (tp != NULL) {
331 			tty_lock(tp);
332 			if (ttyoutq_bytesused(&ss->snp_outq) > 0)
333 				revents |= events & (POLLIN | POLLRDNORM);
334 			tty_unlock(tp);
335 		}
336 	}
337 
338 	if (revents == 0)
339 		selrecord(td, &ss->snp_outpoll);
340 
341 	return (revents);
342 }
343 
344 /*
345  * TTY hook events.
346  */
347 
348 static int
349 snp_modevent(module_t mod, int type, void *data)
350 {
351 
352 	switch (type) {
353 	case MOD_LOAD:
354 		snp_dev = make_dev(&snp_cdevsw, 0,
355 		    UID_ROOT, GID_WHEEL, 0600, "snp");
356 		return (0);
357 	case MOD_UNLOAD:
358 		/* XXX: Make existing users leave. */
359 		destroy_dev(snp_dev);
360 		return (0);
361 	default:
362 		return (EOPNOTSUPP);
363 	}
364 }
365 
366 static void
367 snp_getc_capture(struct tty *tp, const void *buf, size_t len)
368 {
369 	struct snp_softc *ss = ttyhook_softc(tp);
370 
371 	ttyoutq_write(&ss->snp_outq, buf, len);
372 
373 	cv_broadcast(&ss->snp_outwait);
374 	selwakeup(&ss->snp_outpoll);
375 }
376 
377 static moduledata_t snp_mod = {
378 	"snp",
379 	snp_modevent,
380 	NULL
381 };
382 
383 DECLARE_MODULE(snp, snp_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
384