xref: /freebsd/sys/dev/snp/snp.c (revision 6419bb52)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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 __FBSDID("$FreeBSD$");
31 
32 #include <sys/param.h>
33 #include <sys/conf.h>
34 #include <sys/fcntl.h>
35 #include <sys/filio.h>
36 #include <sys/kernel.h>
37 #include <sys/malloc.h>
38 #include <sys/module.h>
39 #include <sys/poll.h>
40 #include <sys/proc.h>
41 #include <sys/snoop.h>
42 #include <sys/sx.h>
43 #include <sys/systm.h>
44 #include <sys/tty.h>
45 #include <sys/uio.h>
46 
47 static struct cdev	*snp_dev;
48 static MALLOC_DEFINE(M_SNP, "snp", "tty snoop device");
49 
50 /* XXX: should be mtx, but TTY can be locked by Giant. */
51 #if 0
52 static struct mtx	snp_register_lock;
53 MTX_SYSINIT(snp_register_lock, &snp_register_lock,
54     "tty snoop registration", MTX_DEF);
55 #define	SNP_LOCK()	mtx_lock(&snp_register_lock)
56 #define	SNP_UNLOCK()	mtx_unlock(&snp_register_lock)
57 #else
58 static struct sx	snp_register_lock;
59 SX_SYSINIT(snp_register_lock, &snp_register_lock,
60     "tty snoop registration");
61 #define	SNP_LOCK()	sx_xlock(&snp_register_lock)
62 #define	SNP_UNLOCK()	sx_xunlock(&snp_register_lock)
63 #endif
64 
65 #define	SNPGTYY_32DEV	_IOR('T', 89, uint32_t)
66 
67 /*
68  * There is no need to have a big input buffer. In most typical setups,
69  * we won't inject much data into the TTY, because users can't type
70  * really fast.
71  */
72 #define SNP_INPUT_BUFSIZE	16
73 /*
74  * The output buffer has to be really big. Right now we don't support
75  * any form of flow control, which means we lost any data we can't
76  * accept. We set the output buffer size to about twice the size of a
77  * pseudo-terminal/virtual console's output buffer.
78  */
79 #define SNP_OUTPUT_BUFSIZE	16384
80 
81 static d_open_t		snp_open;
82 static d_read_t		snp_read;
83 static d_write_t	snp_write;
84 static d_ioctl_t	snp_ioctl;
85 static d_poll_t		snp_poll;
86 
87 static struct cdevsw snp_cdevsw = {
88 	.d_version	= D_VERSION,
89 	.d_open		= snp_open,
90 	.d_read		= snp_read,
91 	.d_write	= snp_write,
92 	.d_ioctl	= snp_ioctl,
93 	.d_poll		= snp_poll,
94 	.d_name		= "snp",
95 };
96 
97 static th_getc_capture_t	snp_getc_capture;
98 
99 static struct ttyhook snp_hook = {
100 	.th_getc_capture	= snp_getc_capture,
101 };
102 
103 /*
104  * Per-instance structure.
105  *
106  * List of locks
107  * (r)	locked by snp_register_lock on assignment
108  * (t)	locked by tty_lock
109  */
110 struct snp_softc {
111 	struct tty	*snp_tty;	/* (r) TTY we're snooping. */
112 	struct ttyoutq	snp_outq;	/* (t) Output queue. */
113 	struct cv	snp_outwait;	/* (t) Output wait queue. */
114 	struct selinfo	snp_outpoll;	/* (t) Output polling. */
115 };
116 
117 static void
118 snp_dtor(void *data)
119 {
120 	struct snp_softc *ss = data;
121 	struct tty *tp;
122 
123 	tp = ss->snp_tty;
124 	if (tp != NULL) {
125 		tty_lock(tp);
126 		ttyoutq_free(&ss->snp_outq);
127 		ttyhook_unregister(tp);
128 	}
129 
130 	cv_destroy(&ss->snp_outwait);
131 	free(ss, M_SNP);
132 }
133 
134 /*
135  * Snoop device node routines.
136  */
137 
138 static int
139 snp_open(struct cdev *dev, int flag, int mode, struct thread *td)
140 {
141 	struct snp_softc *ss;
142 
143 	/* Allocate per-snoop data. */
144 	ss = malloc(sizeof(struct snp_softc), M_SNP, M_WAITOK|M_ZERO);
145 	cv_init(&ss->snp_outwait, "snp out");
146 
147 	devfs_set_cdevpriv(ss, snp_dtor);
148 
149 	return (0);
150 }
151 
152 static int
153 snp_read(struct cdev *dev, struct uio *uio, int flag)
154 {
155 	int error, oresid = uio->uio_resid;
156 	struct snp_softc *ss;
157 	struct tty *tp;
158 
159 	if (uio->uio_resid == 0)
160 		return (0);
161 
162 	error = devfs_get_cdevpriv((void **)&ss);
163 	if (error != 0)
164 		return (error);
165 
166 	tp = ss->snp_tty;
167 	if (tp == NULL || tty_gone(tp))
168 		return (EIO);
169 
170 	tty_lock(tp);
171 	for (;;) {
172 		error = ttyoutq_read_uio(&ss->snp_outq, tp, uio);
173 		if (error != 0 || uio->uio_resid != oresid)
174 			break;
175 
176 		/* Wait for more data. */
177 		if (flag & O_NONBLOCK) {
178 			error = EWOULDBLOCK;
179 			break;
180 		}
181 		error = cv_wait_sig(&ss->snp_outwait, tty_getlock(tp));
182 		if (error != 0)
183 			break;
184 		if (tty_gone(tp)) {
185 			error = EIO;
186 			break;
187 		}
188 	}
189 	tty_unlock(tp);
190 
191 	return (error);
192 }
193 
194 static int
195 snp_write(struct cdev *dev, struct uio *uio, int flag)
196 {
197 	struct snp_softc *ss;
198 	struct tty *tp;
199 	int error, len;
200 	char in[SNP_INPUT_BUFSIZE];
201 
202 	error = devfs_get_cdevpriv((void **)&ss);
203 	if (error != 0)
204 		return (error);
205 
206 	tp = ss->snp_tty;
207 	if (tp == NULL || tty_gone(tp))
208 		return (EIO);
209 
210 	while (uio->uio_resid > 0) {
211 		/* Read new data. */
212 		len = imin(uio->uio_resid, sizeof in);
213 		error = uiomove(in, len, uio);
214 		if (error != 0)
215 			return (error);
216 
217 		tty_lock(tp);
218 
219 		/* Driver could have abandoned the TTY in the mean time. */
220 		if (tty_gone(tp)) {
221 			tty_unlock(tp);
222 			return (ENXIO);
223 		}
224 
225 		/*
226 		 * Deliver data to the TTY. Ignore errors for now,
227 		 * because we shouldn't bail out when we're running
228 		 * close to the watermarks.
229 		 */
230 		ttydisc_rint_simple(tp, in, len);
231 		ttydisc_rint_done(tp);
232 
233 		tty_unlock(tp);
234 	}
235 
236 	return (0);
237 }
238 
239 static int
240 snp_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags,
241     struct thread *td)
242 {
243 	struct snp_softc *ss;
244 	struct tty *tp;
245 	int error;
246 
247 	error = devfs_get_cdevpriv((void **)&ss);
248 	if (error != 0)
249 		return (error);
250 
251 	switch (cmd) {
252 	case SNPSTTY:
253 		/* Bind TTY to snoop instance. */
254 		SNP_LOCK();
255 		if (ss->snp_tty != NULL) {
256 			SNP_UNLOCK();
257 			return (EBUSY);
258 		}
259 		/*
260 		 * XXXRW / XXXJA: no capability check here.
261 		 */
262 		error = ttyhook_register(&ss->snp_tty, td->td_proc,
263 		    *(int *)data, &snp_hook, ss);
264 		SNP_UNLOCK();
265 		if (error != 0)
266 			return (error);
267 
268 		/* Now that went okay, allocate a buffer for the queue. */
269 		tp = ss->snp_tty;
270 		tty_lock(tp);
271 		ttyoutq_setsize(&ss->snp_outq, tp, SNP_OUTPUT_BUFSIZE);
272 		tty_unlock(tp);
273 
274 		return (0);
275 	case SNPGTTY:
276 		/* Obtain device number of associated TTY. */
277 		if (ss->snp_tty == NULL)
278 			*(dev_t *)data = NODEV;
279 		else
280 			*(dev_t *)data = tty_udev(ss->snp_tty);
281 		return (0);
282 	case SNPGTYY_32DEV:
283 		if (ss->snp_tty == NULL)
284 			*(uint32_t *)data = -1;
285 		else
286 			*(uint32_t *)data = tty_udev(ss->snp_tty); /* trunc */
287 		return (0);
288 	case FIONREAD:
289 		tp = ss->snp_tty;
290 		if (tp != NULL) {
291 			tty_lock(tp);
292 			*(int *)data = ttyoutq_bytesused(&ss->snp_outq);
293 			tty_unlock(tp);
294 		} else {
295 			*(int *)data = 0;
296 		}
297 		return (0);
298 	default:
299 		return (ENOTTY);
300 	}
301 }
302 
303 static int
304 snp_poll(struct cdev *dev, int events, struct thread *td)
305 {
306 	struct snp_softc *ss;
307 	struct tty *tp;
308 	int revents;
309 
310 	if (devfs_get_cdevpriv((void **)&ss) != 0)
311 		return (events &
312 		    (POLLHUP|POLLIN|POLLRDNORM|POLLOUT|POLLWRNORM));
313 
314 	revents = 0;
315 
316 	if (events & (POLLIN | POLLRDNORM)) {
317 		tp = ss->snp_tty;
318 		if (tp != NULL) {
319 			tty_lock(tp);
320 			if (ttyoutq_bytesused(&ss->snp_outq) > 0)
321 				revents |= events & (POLLIN | POLLRDNORM);
322 			tty_unlock(tp);
323 		}
324 	}
325 
326 	if (revents == 0)
327 		selrecord(td, &ss->snp_outpoll);
328 
329 	return (revents);
330 }
331 
332 /*
333  * TTY hook events.
334  */
335 
336 static int
337 snp_modevent(module_t mod, int type, void *data)
338 {
339 
340 	switch (type) {
341 	case MOD_LOAD:
342 		snp_dev = make_dev(&snp_cdevsw, 0,
343 		    UID_ROOT, GID_WHEEL, 0600, "snp");
344 		return (0);
345 	case MOD_UNLOAD:
346 		/* XXX: Make existing users leave. */
347 		destroy_dev(snp_dev);
348 		return (0);
349 	default:
350 		return (EOPNOTSUPP);
351 	}
352 }
353 
354 static void
355 snp_getc_capture(struct tty *tp, const void *buf, size_t len)
356 {
357 	struct snp_softc *ss = ttyhook_softc(tp);
358 
359 	ttyoutq_write(&ss->snp_outq, buf, len);
360 
361 	cv_broadcast(&ss->snp_outwait);
362 	selwakeup(&ss->snp_outpoll);
363 }
364 
365 static moduledata_t snp_mod = {
366 	"snp",
367 	snp_modevent,
368 	NULL
369 };
370 
371 DECLARE_MODULE(snp, snp_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
372