xref: /freebsd/usr.sbin/bhyve/mevent.c (revision 9c999a259f00b35f0467acd351fea9157ed7e1e4) 
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2011 NetApp, Inc.
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 NETAPP, INC ``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 NETAPP, INC 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  * $FreeBSD$
29  */
30 
31 /*
32  * Micro event library for FreeBSD, designed for a single i/o thread
33  * using kqueue, and having events be persistent by default.
34  */
35 
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38 
39 #include <assert.h>
40 #ifndef WITHOUT_CAPSICUM
41 #include <capsicum_helpers.h>
42 #endif
43 #include <err.h>
44 #include <errno.h>
45 #include <stdbool.h>
46 #include <stdlib.h>
47 #include <stdio.h>
48 #include <string.h>
49 #include <sysexits.h>
50 #include <unistd.h>
51 
52 #include <sys/types.h>
53 #ifndef WITHOUT_CAPSICUM
54 #include <sys/capsicum.h>
55 #endif
56 #include <sys/event.h>
57 #include <sys/time.h>
58 
59 #include <pthread.h>
60 #include <pthread_np.h>
61 
62 #include "mevent.h"
63 
64 #define	MEVENT_MAX	64
65 
66 static pthread_t mevent_tid;
67 static pthread_once_t mevent_once = PTHREAD_ONCE_INIT;
68 static int mevent_timid = 43;
69 static int mevent_pipefd[2];
70 static int mfd;
71 static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;
72 
73 struct mevent {
74 	void	(*me_func)(int, enum ev_type, void *);
75 #define me_msecs me_fd
76 	int	me_fd;
77 	int	me_timid;
78 	enum ev_type me_type;
79 	void    *me_param;
80 	int	me_cq;
81 	int	me_state; /* Desired kevent flags. */
82 	int	me_closefd;
83 	int	me_fflags;
84 	LIST_ENTRY(mevent) me_list;
85 };
86 
87 static LIST_HEAD(listhead, mevent) global_head, change_head;
88 
89 static void
90 mevent_qlock(void)
91 {
92 	pthread_mutex_lock(&mevent_lmutex);
93 }
94 
95 static void
96 mevent_qunlock(void)
97 {
98 	pthread_mutex_unlock(&mevent_lmutex);
99 }
100 
101 static void
102 mevent_pipe_read(int fd, enum ev_type type, void *param)
103 {
104 	char buf[MEVENT_MAX];
105 	int status;
106 
107 	/*
108 	 * Drain the pipe read side. The fd is non-blocking so this is
109 	 * safe to do.
110 	 */
111 	do {
112 		status = read(fd, buf, sizeof(buf));
113 	} while (status == MEVENT_MAX);
114 }
115 
116 static void
117 mevent_notify(void)
118 {
119 	char c = '\0';
120 
121 	/*
122 	 * If calling from outside the i/o thread, write a byte on the
123 	 * pipe to force the i/o thread to exit the blocking kevent call.
124 	 */
125 	if (mevent_pipefd[1] != 0 && pthread_self() != mevent_tid) {
126 		write(mevent_pipefd[1], &c, 1);
127 	}
128 }
129 
130 static void
131 mevent_init(void)
132 {
133 #ifndef WITHOUT_CAPSICUM
134 	cap_rights_t rights;
135 #endif
136 
137 	mfd = kqueue();
138 	assert(mfd > 0);
139 
140 #ifndef WITHOUT_CAPSICUM
141 	cap_rights_init(&rights, CAP_KQUEUE);
142 	if (caph_rights_limit(mfd, &rights) == -1)
143 		errx(EX_OSERR, "Unable to apply rights for sandbox");
144 #endif
145 
146 	LIST_INIT(&change_head);
147 	LIST_INIT(&global_head);
148 }
149 
150 static int
151 mevent_kq_filter(struct mevent *mevp)
152 {
153 	int retval;
154 
155 	retval = 0;
156 
157 	if (mevp->me_type == EVF_READ)
158 		retval = EVFILT_READ;
159 
160 	if (mevp->me_type == EVF_WRITE)
161 		retval = EVFILT_WRITE;
162 
163 	if (mevp->me_type == EVF_TIMER)
164 		retval = EVFILT_TIMER;
165 
166 	if (mevp->me_type == EVF_SIGNAL)
167 		retval = EVFILT_SIGNAL;
168 
169 	if (mevp->me_type == EVF_VNODE)
170 		retval = EVFILT_VNODE;
171 
172 	return (retval);
173 }
174 
175 static int
176 mevent_kq_flags(struct mevent *mevp)
177 {
178 	return (mevp->me_state);
179 }
180 
181 static int
182 mevent_kq_fflags(struct mevent *mevp)
183 {
184 	int retval;
185 
186 	retval = 0;
187 
188 	switch (mevp->me_type) {
189 	case EVF_VNODE:
190 		if ((mevp->me_fflags & EVFF_ATTRIB) != 0)
191 			retval |= NOTE_ATTRIB;
192 		break;
193 	case EVF_READ:
194 	case EVF_WRITE:
195 	case EVF_TIMER:
196 	case EVF_SIGNAL:
197 		break;
198 	}
199 
200 	return (retval);
201 }
202 
203 static void
204 mevent_populate(struct mevent *mevp, struct kevent *kev)
205 {
206 	if (mevp->me_type == EVF_TIMER) {
207 		kev->ident = mevp->me_timid;
208 		kev->data = mevp->me_msecs;
209 	} else {
210 		kev->ident = mevp->me_fd;
211 		kev->data = 0;
212 	}
213 	kev->filter = mevent_kq_filter(mevp);
214 	kev->flags = mevent_kq_flags(mevp);
215 	kev->fflags = mevent_kq_fflags(mevp);
216 	kev->udata = mevp;
217 }
218 
219 static int
220 mevent_build(struct kevent *kev)
221 {
222 	struct mevent *mevp, *tmpp;
223 	int i;
224 
225 	i = 0;
226 
227 	mevent_qlock();
228 
229 	LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
230 		if (mevp->me_closefd) {
231 			/*
232 			 * A close of the file descriptor will remove the
233 			 * event
234 			 */
235 			close(mevp->me_fd);
236 		} else {
237 			assert((mevp->me_state & EV_ADD) == 0);
238 			mevent_populate(mevp, &kev[i]);
239 			i++;
240 		}
241 
242 		mevp->me_cq = 0;
243 		LIST_REMOVE(mevp, me_list);
244 
245 		if (mevp->me_state & EV_DELETE) {
246 			free(mevp);
247 		} else {
248 			LIST_INSERT_HEAD(&global_head, mevp, me_list);
249 		}
250 
251 		assert(i < MEVENT_MAX);
252 	}
253 
254 	mevent_qunlock();
255 
256 	return (i);
257 }
258 
259 static void
260 mevent_handle(struct kevent *kev, int numev)
261 {
262 	struct mevent *mevp;
263 	int i;
264 
265 	for (i = 0; i < numev; i++) {
266 		mevp = kev[i].udata;
267 
268 		/* XXX check for EV_ERROR ? */
269 
270 		(*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);
271 	}
272 }
273 
274 static struct mevent *
275 mevent_add_state(int tfd, enum ev_type type,
276 	   void (*func)(int, enum ev_type, void *), void *param,
277 	   int state, int fflags)
278 {
279 	struct kevent kev;
280 	struct mevent *lp, *mevp;
281 	int ret;
282 
283 	if (tfd < 0 || func == NULL) {
284 		return (NULL);
285 	}
286 
287 	mevp = NULL;
288 
289 	pthread_once(&mevent_once, mevent_init);
290 
291 	mevent_qlock();
292 
293 	/*
294 	 * Verify that the fd/type tuple is not present in any list
295 	 */
296 	LIST_FOREACH(lp, &global_head, me_list) {
297 		if (type != EVF_TIMER && lp->me_fd == tfd &&
298 		    lp->me_type == type) {
299 			goto exit;
300 		}
301 	}
302 
303 	LIST_FOREACH(lp, &change_head, me_list) {
304 		if (type != EVF_TIMER && lp->me_fd == tfd &&
305 		    lp->me_type == type) {
306 			goto exit;
307 		}
308 	}
309 
310 	/*
311 	 * Allocate an entry and populate it.
312 	 */
313 	mevp = calloc(1, sizeof(struct mevent));
314 	if (mevp == NULL) {
315 		goto exit;
316 	}
317 
318 	if (type == EVF_TIMER) {
319 		mevp->me_msecs = tfd;
320 		mevp->me_timid = mevent_timid++;
321 	} else
322 		mevp->me_fd = tfd;
323 	mevp->me_type = type;
324 	mevp->me_func = func;
325 	mevp->me_param = param;
326 	mevp->me_state = state;
327 	mevp->me_fflags = fflags;
328 
329 	/*
330 	 * Try to add the event.  If this fails, report the failure to
331 	 * the caller.
332 	 */
333 	mevent_populate(mevp, &kev);
334 	ret = kevent(mfd, &kev, 1, NULL, 0, NULL);
335 	if (ret == -1) {
336 		free(mevp);
337 		mevp = NULL;
338 		goto exit;
339 	}
340 
341 	mevp->me_state &= ~EV_ADD;
342 	LIST_INSERT_HEAD(&global_head, mevp, me_list);
343 
344 exit:
345 	mevent_qunlock();
346 
347 	return (mevp);
348 }
349 
350 struct mevent *
351 mevent_add(int tfd, enum ev_type type,
352 	   void (*func)(int, enum ev_type, void *), void *param)
353 {
354 
355 	return (mevent_add_state(tfd, type, func, param, EV_ADD, 0));
356 }
357 
358 struct mevent *
359 mevent_add_flags(int tfd, enum ev_type type, int fflags,
360 		 void (*func)(int, enum ev_type, void *), void *param)
361 {
362 
363 	return (mevent_add_state(tfd, type, func, param, EV_ADD, fflags));
364 }
365 
366 struct mevent *
367 mevent_add_disabled(int tfd, enum ev_type type,
368 		    void (*func)(int, enum ev_type, void *), void *param)
369 {
370 
371 	return (mevent_add_state(tfd, type, func, param, EV_ADD | EV_DISABLE, 0));
372 }
373 
374 static int
375 mevent_update(struct mevent *evp, bool enable)
376 {
377 	int newstate;
378 
379 	mevent_qlock();
380 
381 	/*
382 	 * It's not possible to enable/disable a deleted event
383 	 */
384 	assert((evp->me_state & EV_DELETE) == 0);
385 
386 	newstate = evp->me_state;
387 	if (enable) {
388 		newstate |= EV_ENABLE;
389 		newstate &= ~EV_DISABLE;
390 	} else {
391 		newstate |= EV_DISABLE;
392 		newstate &= ~EV_ENABLE;
393 	}
394 
395 	/*
396 	 * No update needed if state isn't changing
397 	 */
398 	if (evp->me_state != newstate) {
399 		evp->me_state = newstate;
400 
401 		/*
402 		 * Place the entry onto the changed list if not
403 		 * already there.
404 		 */
405 		if (evp->me_cq == 0) {
406 			evp->me_cq = 1;
407 			LIST_REMOVE(evp, me_list);
408 			LIST_INSERT_HEAD(&change_head, evp, me_list);
409 			mevent_notify();
410 		}
411 	}
412 
413 	mevent_qunlock();
414 
415 	return (0);
416 }
417 
418 int
419 mevent_enable(struct mevent *evp)
420 {
421 
422 	return (mevent_update(evp, true));
423 }
424 
425 int
426 mevent_disable(struct mevent *evp)
427 {
428 
429 	return (mevent_update(evp, false));
430 }
431 
432 static int
433 mevent_delete_event(struct mevent *evp, int closefd)
434 {
435 	mevent_qlock();
436 
437 	/*
438          * Place the entry onto the changed list if not already there, and
439 	 * mark as to be deleted.
440          */
441         if (evp->me_cq == 0) {
442 		evp->me_cq = 1;
443 		LIST_REMOVE(evp, me_list);
444 		LIST_INSERT_HEAD(&change_head, evp, me_list);
445 		mevent_notify();
446         }
447 	evp->me_state = EV_DELETE;
448 
449 	if (closefd)
450 		evp->me_closefd = 1;
451 
452 	mevent_qunlock();
453 
454 	return (0);
455 }
456 
457 int
458 mevent_delete(struct mevent *evp)
459 {
460 
461 	return (mevent_delete_event(evp, 0));
462 }
463 
464 int
465 mevent_delete_close(struct mevent *evp)
466 {
467 
468 	return (mevent_delete_event(evp, 1));
469 }
470 
471 static void
472 mevent_set_name(void)
473 {
474 
475 	pthread_set_name_np(mevent_tid, "mevent");
476 }
477 
478 void
479 mevent_dispatch(void)
480 {
481 	struct kevent changelist[MEVENT_MAX];
482 	struct kevent eventlist[MEVENT_MAX];
483 	struct mevent *pipev;
484 	int numev;
485 	int ret;
486 #ifndef WITHOUT_CAPSICUM
487 	cap_rights_t rights;
488 #endif
489 
490 	mevent_tid = pthread_self();
491 	mevent_set_name();
492 
493 	pthread_once(&mevent_once, mevent_init);
494 
495 	/*
496 	 * Open the pipe that will be used for other threads to force
497 	 * the blocking kqueue call to exit by writing to it. Set the
498 	 * descriptor to non-blocking.
499 	 */
500 	ret = pipe(mevent_pipefd);
501 	if (ret < 0) {
502 		perror("pipe");
503 		exit(0);
504 	}
505 
506 #ifndef WITHOUT_CAPSICUM
507 	cap_rights_init(&rights, CAP_EVENT, CAP_READ, CAP_WRITE);
508 	if (caph_rights_limit(mevent_pipefd[0], &rights) == -1)
509 		errx(EX_OSERR, "Unable to apply rights for sandbox");
510 	if (caph_rights_limit(mevent_pipefd[1], &rights) == -1)
511 		errx(EX_OSERR, "Unable to apply rights for sandbox");
512 #endif
513 
514 	/*
515 	 * Add internal event handler for the pipe write fd
516 	 */
517 	pipev = mevent_add(mevent_pipefd[0], EVF_READ, mevent_pipe_read, NULL);
518 	assert(pipev != NULL);
519 
520 	for (;;) {
521 		/*
522 		 * Build changelist if required.
523 		 * XXX the changelist can be put into the blocking call
524 		 * to eliminate the extra syscall. Currently better for
525 		 * debug.
526 		 */
527 		numev = mevent_build(changelist);
528 		if (numev) {
529 			ret = kevent(mfd, changelist, numev, NULL, 0, NULL);
530 			if (ret == -1) {
531 				perror("Error return from kevent change");
532 			}
533 		}
534 
535 		/*
536 		 * Block awaiting events
537 		 */
538 		ret = kevent(mfd, NULL, 0, eventlist, MEVENT_MAX, NULL);
539 		if (ret == -1 && errno != EINTR) {
540 			perror("Error return from kevent monitor");
541 		}
542 
543 		/*
544 		 * Handle reported events
545 		 */
546 		mevent_handle(eventlist, ret);
547 	}
548 }
549