xref: /freebsd/usr.sbin/bhyve/mevent.c (revision 190cef3d) 
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 #include <err.h>
41 #include <errno.h>
42 #include <stdlib.h>
43 #include <stdio.h>
44 #include <string.h>
45 #include <sysexits.h>
46 #include <unistd.h>
47 
48 #include <sys/types.h>
49 #ifndef WITHOUT_CAPSICUM
50 #include <sys/capsicum.h>
51 #endif
52 #include <sys/event.h>
53 #include <sys/time.h>
54 
55 #include <pthread.h>
56 #include <pthread_np.h>
57 
58 #include "mevent.h"
59 
60 #define	MEVENT_MAX	64
61 
62 #define	MEV_ADD		1
63 #define	MEV_ENABLE	2
64 #define	MEV_DISABLE	3
65 #define	MEV_DEL_PENDING	4
66 
67 extern char *vmname;
68 
69 static pthread_t mevent_tid;
70 static int mevent_timid = 43;
71 static int mevent_pipefd[2];
72 static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;
73 
74 struct mevent {
75 	void	(*me_func)(int, enum ev_type, void *);
76 #define me_msecs me_fd
77 	int	me_fd;
78 	int	me_timid;
79 	enum ev_type me_type;
80 	void    *me_param;
81 	int	me_cq;
82 	int	me_state;
83 	int	me_closefd;
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;
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 int
131 mevent_kq_filter(struct mevent *mevp)
132 {
133 	int retval;
134 
135 	retval = 0;
136 
137 	if (mevp->me_type == EVF_READ)
138 		retval = EVFILT_READ;
139 
140 	if (mevp->me_type == EVF_WRITE)
141 		retval = EVFILT_WRITE;
142 
143 	if (mevp->me_type == EVF_TIMER)
144 		retval = EVFILT_TIMER;
145 
146 	if (mevp->me_type == EVF_SIGNAL)
147 		retval = EVFILT_SIGNAL;
148 
149 	return (retval);
150 }
151 
152 static int
153 mevent_kq_flags(struct mevent *mevp)
154 {
155 	int ret;
156 
157 	switch (mevp->me_state) {
158 	case MEV_ADD:
159 		ret = EV_ADD;		/* implicitly enabled */
160 		break;
161 	case MEV_ENABLE:
162 		ret = EV_ENABLE;
163 		break;
164 	case MEV_DISABLE:
165 		ret = EV_DISABLE;
166 		break;
167 	case MEV_DEL_PENDING:
168 		ret = EV_DELETE;
169 		break;
170 	default:
171 		assert(0);
172 		break;
173 	}
174 
175 	return (ret);
176 }
177 
178 static int
179 mevent_kq_fflags(struct mevent *mevp)
180 {
181 	/* XXX nothing yet, perhaps EV_EOF for reads ? */
182 	return (0);
183 }
184 
185 static int
186 mevent_build(int mfd, struct kevent *kev)
187 {
188 	struct mevent *mevp, *tmpp;
189 	int i;
190 
191 	i = 0;
192 
193 	mevent_qlock();
194 
195 	LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
196 		if (mevp->me_closefd) {
197 			/*
198 			 * A close of the file descriptor will remove the
199 			 * event
200 			 */
201 			close(mevp->me_fd);
202 		} else {
203 			if (mevp->me_type == EVF_TIMER) {
204 				kev[i].ident = mevp->me_timid;
205 				kev[i].data = mevp->me_msecs;
206 			} else {
207 				kev[i].ident = mevp->me_fd;
208 				kev[i].data = 0;
209 			}
210 			kev[i].filter = mevent_kq_filter(mevp);
211 			kev[i].flags = mevent_kq_flags(mevp);
212 			kev[i].fflags = mevent_kq_fflags(mevp);
213 			kev[i].udata = mevp;
214 			i++;
215 		}
216 
217 		mevp->me_cq = 0;
218 		LIST_REMOVE(mevp, me_list);
219 
220 		if (mevp->me_state == MEV_DEL_PENDING) {
221 			free(mevp);
222 		} else {
223 			LIST_INSERT_HEAD(&global_head, mevp, me_list);
224 		}
225 
226 		assert(i < MEVENT_MAX);
227 	}
228 
229 	mevent_qunlock();
230 
231 	return (i);
232 }
233 
234 static void
235 mevent_handle(struct kevent *kev, int numev)
236 {
237 	struct mevent *mevp;
238 	int i;
239 
240 	for (i = 0; i < numev; i++) {
241 		mevp = kev[i].udata;
242 
243 		/* XXX check for EV_ERROR ? */
244 
245 		(*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);
246 	}
247 }
248 
249 struct mevent *
250 mevent_add(int tfd, enum ev_type type,
251 	   void (*func)(int, enum ev_type, void *), void *param)
252 {
253 	struct mevent *lp, *mevp;
254 
255 	if (tfd < 0 || func == NULL) {
256 		return (NULL);
257 	}
258 
259 	mevp = NULL;
260 
261 	mevent_qlock();
262 
263 	/*
264 	 * Verify that the fd/type tuple is not present in any list
265 	 */
266 	LIST_FOREACH(lp, &global_head, me_list) {
267 		if (type != EVF_TIMER && lp->me_fd == tfd &&
268 		    lp->me_type == type) {
269 			goto exit;
270 		}
271 	}
272 
273 	LIST_FOREACH(lp, &change_head, me_list) {
274 		if (type != EVF_TIMER && lp->me_fd == tfd &&
275 		    lp->me_type == type) {
276 			goto exit;
277 		}
278 	}
279 
280 	/*
281 	 * Allocate an entry, populate it, and add it to the change list.
282 	 */
283 	mevp = calloc(1, sizeof(struct mevent));
284 	if (mevp == NULL) {
285 		goto exit;
286 	}
287 
288 	if (type == EVF_TIMER) {
289 		mevp->me_msecs = tfd;
290 		mevp->me_timid = mevent_timid++;
291 	} else
292 		mevp->me_fd = tfd;
293 	mevp->me_type = type;
294 	mevp->me_func = func;
295 	mevp->me_param = param;
296 
297 	LIST_INSERT_HEAD(&change_head, mevp, me_list);
298 	mevp->me_cq = 1;
299 	mevp->me_state = MEV_ADD;
300 	mevent_notify();
301 
302 exit:
303 	mevent_qunlock();
304 
305 	return (mevp);
306 }
307 
308 static int
309 mevent_update(struct mevent *evp, int newstate)
310 {
311 	/*
312 	 * It's not possible to enable/disable a deleted event
313 	 */
314 	if (evp->me_state == MEV_DEL_PENDING)
315 		return (EINVAL);
316 
317 	/*
318 	 * No update needed if state isn't changing
319 	 */
320 	if (evp->me_state == newstate)
321 		return (0);
322 
323 	mevent_qlock();
324 
325 	evp->me_state = newstate;
326 
327 	/*
328 	 * Place the entry onto the changed list if not already there.
329 	 */
330 	if (evp->me_cq == 0) {
331 		evp->me_cq = 1;
332 		LIST_REMOVE(evp, me_list);
333 		LIST_INSERT_HEAD(&change_head, evp, me_list);
334 		mevent_notify();
335 	}
336 
337 	mevent_qunlock();
338 
339 	return (0);
340 }
341 
342 int
343 mevent_enable(struct mevent *evp)
344 {
345 
346 	return (mevent_update(evp, MEV_ENABLE));
347 }
348 
349 int
350 mevent_disable(struct mevent *evp)
351 {
352 
353 	return (mevent_update(evp, MEV_DISABLE));
354 }
355 
356 static int
357 mevent_delete_event(struct mevent *evp, int closefd)
358 {
359 	mevent_qlock();
360 
361 	/*
362          * Place the entry onto the changed list if not already there, and
363 	 * mark as to be deleted.
364          */
365         if (evp->me_cq == 0) {
366 		evp->me_cq = 1;
367 		LIST_REMOVE(evp, me_list);
368 		LIST_INSERT_HEAD(&change_head, evp, me_list);
369 		mevent_notify();
370         }
371 	evp->me_state = MEV_DEL_PENDING;
372 
373 	if (closefd)
374 		evp->me_closefd = 1;
375 
376 	mevent_qunlock();
377 
378 	return (0);
379 }
380 
381 int
382 mevent_delete(struct mevent *evp)
383 {
384 
385 	return (mevent_delete_event(evp, 0));
386 }
387 
388 int
389 mevent_delete_close(struct mevent *evp)
390 {
391 
392 	return (mevent_delete_event(evp, 1));
393 }
394 
395 static void
396 mevent_set_name(void)
397 {
398 
399 	pthread_set_name_np(mevent_tid, "mevent");
400 }
401 
402 void
403 mevent_dispatch(void)
404 {
405 	struct kevent changelist[MEVENT_MAX];
406 	struct kevent eventlist[MEVENT_MAX];
407 	struct mevent *pipev;
408 	int mfd;
409 	int numev;
410 	int ret;
411 #ifndef WITHOUT_CAPSICUM
412 	cap_rights_t rights;
413 #endif
414 
415 	mevent_tid = pthread_self();
416 	mevent_set_name();
417 
418 	mfd = kqueue();
419 	assert(mfd > 0);
420 
421 #ifndef WITHOUT_CAPSICUM
422 	cap_rights_init(&rights, CAP_KQUEUE);
423 	if (cap_rights_limit(mfd, &rights) == -1 && errno != ENOSYS)
424 		errx(EX_OSERR, "Unable to apply rights for sandbox");
425 #endif
426 
427 	/*
428 	 * Open the pipe that will be used for other threads to force
429 	 * the blocking kqueue call to exit by writing to it. Set the
430 	 * descriptor to non-blocking.
431 	 */
432 	ret = pipe(mevent_pipefd);
433 	if (ret < 0) {
434 		perror("pipe");
435 		exit(0);
436 	}
437 
438 #ifndef WITHOUT_CAPSICUM
439 	cap_rights_init(&rights, CAP_EVENT, CAP_READ, CAP_WRITE);
440 	if (cap_rights_limit(mevent_pipefd[0], &rights) == -1 && errno != ENOSYS)
441 		errx(EX_OSERR, "Unable to apply rights for sandbox");
442 	if (cap_rights_limit(mevent_pipefd[1], &rights) == -1 && errno != ENOSYS)
443 		errx(EX_OSERR, "Unable to apply rights for sandbox");
444 #endif
445 
446 	/*
447 	 * Add internal event handler for the pipe write fd
448 	 */
449 	pipev = mevent_add(mevent_pipefd[0], EVF_READ, mevent_pipe_read, NULL);
450 	assert(pipev != NULL);
451 
452 	for (;;) {
453 		/*
454 		 * Build changelist if required.
455 		 * XXX the changelist can be put into the blocking call
456 		 * to eliminate the extra syscall. Currently better for
457 		 * debug.
458 		 */
459 		numev = mevent_build(mfd, changelist);
460 		if (numev) {
461 			ret = kevent(mfd, changelist, numev, NULL, 0, NULL);
462 			if (ret == -1) {
463 				perror("Error return from kevent change");
464 			}
465 		}
466 
467 		/*
468 		 * Block awaiting events
469 		 */
470 		ret = kevent(mfd, NULL, 0, eventlist, MEVENT_MAX, NULL);
471 		if (ret == -1 && errno != EINTR) {
472 			perror("Error return from kevent monitor");
473 		}
474 
475 		/*
476 		 * Handle reported events
477 		 */
478 		mevent_handle(eventlist, ret);
479 	}
480 }
481