1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2014 Dmitry Chagin <dchagin@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
30
31 #include <sys/param.h>
32 #include <sys/systm.h>
33 #include <sys/kernel.h>
34 #include <sys/malloc.h>
35 #include <sys/limits.h>
36 #include <sys/lock.h>
37 #include <sys/mutex.h>
38 #include <sys/types.h>
39 #include <sys/user.h>
40 #include <sys/fcntl.h>
41 #include <sys/file.h>
42 #include <sys/filedesc.h>
43 #include <sys/filio.h>
44 #include <sys/stat.h>
45 #include <sys/errno.h>
46 #include <sys/event.h>
47 #include <sys/poll.h>
48 #include <sys/proc.h>
49 #include <sys/uio.h>
50 #include <sys/selinfo.h>
51 #include <sys/eventfd.h>
52
53 #include <security/audit/audit.h>
54
55 _Static_assert(EFD_CLOEXEC == O_CLOEXEC, "Mismatched EFD_CLOEXEC");
56 _Static_assert(EFD_NONBLOCK == O_NONBLOCK, "Mismatched EFD_NONBLOCK");
57
58 MALLOC_DEFINE(M_EVENTFD, "eventfd", "eventfd structures");
59
60 static fo_rdwr_t eventfd_read;
61 static fo_rdwr_t eventfd_write;
62 static fo_ioctl_t eventfd_ioctl;
63 static fo_poll_t eventfd_poll;
64 static fo_kqfilter_t eventfd_kqfilter;
65 static fo_stat_t eventfd_stat;
66 static fo_close_t eventfd_close;
67 static fo_fill_kinfo_t eventfd_fill_kinfo;
68
69 static struct fileops eventfdops = {
70 .fo_read = eventfd_read,
71 .fo_write = eventfd_write,
72 .fo_truncate = invfo_truncate,
73 .fo_ioctl = eventfd_ioctl,
74 .fo_poll = eventfd_poll,
75 .fo_kqfilter = eventfd_kqfilter,
76 .fo_stat = eventfd_stat,
77 .fo_close = eventfd_close,
78 .fo_chmod = invfo_chmod,
79 .fo_chown = invfo_chown,
80 .fo_sendfile = invfo_sendfile,
81 .fo_fill_kinfo = eventfd_fill_kinfo,
82 .fo_flags = DFLAG_PASSABLE
83 };
84
85 static void filt_eventfddetach(struct knote *kn);
86 static int filt_eventfdread(struct knote *kn, long hint);
87 static int filt_eventfdwrite(struct knote *kn, long hint);
88
89 static struct filterops eventfd_rfiltops = {
90 .f_isfd = 1,
91 .f_detach = filt_eventfddetach,
92 .f_event = filt_eventfdread
93 };
94
95 static struct filterops eventfd_wfiltops = {
96 .f_isfd = 1,
97 .f_detach = filt_eventfddetach,
98 .f_event = filt_eventfdwrite
99 };
100
101 struct eventfd {
102 eventfd_t efd_count;
103 uint32_t efd_flags;
104 struct selinfo efd_sel;
105 struct mtx efd_lock;
106 };
107
108 int
109 eventfd_create_file(struct thread *td, struct file *fp, uint32_t initval,
110 int flags)
111 {
112 struct eventfd *efd;
113 int fflags;
114
115 AUDIT_ARG_FFLAGS(flags);
116 AUDIT_ARG_VALUE(initval);
117
118 efd = malloc(sizeof(*efd), M_EVENTFD, M_WAITOK | M_ZERO);
119 efd->efd_flags = flags;
120 efd->efd_count = initval;
121 mtx_init(&efd->efd_lock, "eventfd", NULL, MTX_DEF);
122 knlist_init_mtx(&efd->efd_sel.si_note, &efd->efd_lock);
123
124 fflags = FREAD | FWRITE;
125 if ((flags & EFD_NONBLOCK) != 0)
126 fflags |= FNONBLOCK;
127 finit(fp, fflags, DTYPE_EVENTFD, efd, &eventfdops);
128
129 return (0);
130 }
131
132 static int
133 eventfd_close(struct file *fp, struct thread *td)
134 {
135 struct eventfd *efd;
136
137 efd = fp->f_data;
138 seldrain(&efd->efd_sel);
139 knlist_destroy(&efd->efd_sel.si_note);
140 mtx_destroy(&efd->efd_lock);
141 free(efd, M_EVENTFD);
142 return (0);
143 }
144
145 static int
146 eventfd_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
147 int flags, struct thread *td)
148 {
149 struct eventfd *efd;
150 eventfd_t count;
151 int error;
152
153 if (uio->uio_resid < sizeof(eventfd_t))
154 return (EINVAL);
155
156 error = 0;
157 efd = fp->f_data;
158 mtx_lock(&efd->efd_lock);
159 while (error == 0 && efd->efd_count == 0) {
160 if ((fp->f_flag & FNONBLOCK) != 0) {
161 mtx_unlock(&efd->efd_lock);
162 return (EAGAIN);
163 }
164 error = mtx_sleep(&efd->efd_count, &efd->efd_lock, PCATCH,
165 "efdrd", 0);
166 }
167 if (error == 0) {
168 MPASS(efd->efd_count > 0);
169 if ((efd->efd_flags & EFD_SEMAPHORE) != 0) {
170 count = 1;
171 --efd->efd_count;
172 } else {
173 count = efd->efd_count;
174 efd->efd_count = 0;
175 }
176 KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
177 selwakeup(&efd->efd_sel);
178 wakeup(&efd->efd_count);
179 mtx_unlock(&efd->efd_lock);
180 error = uiomove(&count, sizeof(eventfd_t), uio);
181 } else
182 mtx_unlock(&efd->efd_lock);
183
184 return (error);
185 }
186
187 static int
188 eventfd_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
189 int flags, struct thread *td)
190 {
191 struct eventfd *efd;
192 eventfd_t count;
193 int error;
194
195 if (uio->uio_resid < sizeof(eventfd_t))
196 return (EINVAL);
197
198 error = uiomove(&count, sizeof(eventfd_t), uio);
199 if (error != 0)
200 return (error);
201 if (count == UINT64_MAX)
202 return (EINVAL);
203
204 efd = fp->f_data;
205 mtx_lock(&efd->efd_lock);
206 retry:
207 if (UINT64_MAX - efd->efd_count <= count) {
208 if ((fp->f_flag & FNONBLOCK) != 0) {
209 mtx_unlock(&efd->efd_lock);
210 /* Do not not return the number of bytes written */
211 uio->uio_resid += sizeof(eventfd_t);
212 return (EAGAIN);
213 }
214 error = mtx_sleep(&efd->efd_count, &efd->efd_lock,
215 PCATCH, "efdwr", 0);
216 if (error == 0)
217 goto retry;
218 }
219 if (error == 0) {
220 MPASS(UINT64_MAX - efd->efd_count > count);
221 efd->efd_count += count;
222 KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
223 selwakeup(&efd->efd_sel);
224 wakeup(&efd->efd_count);
225 }
226 mtx_unlock(&efd->efd_lock);
227
228 return (error);
229 }
230
231 static int
232 eventfd_poll(struct file *fp, int events, struct ucred *active_cred,
233 struct thread *td)
234 {
235 struct eventfd *efd;
236 int revents;
237
238 efd = fp->f_data;
239 revents = 0;
240 mtx_lock(&efd->efd_lock);
241 if ((events & (POLLIN | POLLRDNORM)) != 0 && efd->efd_count > 0)
242 revents |= events & (POLLIN | POLLRDNORM);
243 if ((events & (POLLOUT | POLLWRNORM)) != 0 && UINT64_MAX - 1 >
244 efd->efd_count)
245 revents |= events & (POLLOUT | POLLWRNORM);
246 if (revents == 0)
247 selrecord(td, &efd->efd_sel);
248 mtx_unlock(&efd->efd_lock);
249
250 return (revents);
251 }
252
253 static int
254 eventfd_kqfilter(struct file *fp, struct knote *kn)
255 {
256 struct eventfd *efd = fp->f_data;
257
258 mtx_lock(&efd->efd_lock);
259 switch (kn->kn_filter) {
260 case EVFILT_READ:
261 kn->kn_fop = &eventfd_rfiltops;
262 break;
263 case EVFILT_WRITE:
264 kn->kn_fop = &eventfd_wfiltops;
265 break;
266 default:
267 mtx_unlock(&efd->efd_lock);
268 return (EINVAL);
269 }
270
271 kn->kn_hook = efd;
272 knlist_add(&efd->efd_sel.si_note, kn, 1);
273 mtx_unlock(&efd->efd_lock);
274
275 return (0);
276 }
277
278 static void
279 filt_eventfddetach(struct knote *kn)
280 {
281 struct eventfd *efd = kn->kn_hook;
282
283 mtx_lock(&efd->efd_lock);
284 knlist_remove(&efd->efd_sel.si_note, kn, 1);
285 mtx_unlock(&efd->efd_lock);
286 }
287
288 static int
289 filt_eventfdread(struct knote *kn, long hint)
290 {
291 struct eventfd *efd = kn->kn_hook;
292 int ret;
293
294 mtx_assert(&efd->efd_lock, MA_OWNED);
295 kn->kn_data = (int64_t)efd->efd_count;
296 ret = efd->efd_count > 0;
297
298 return (ret);
299 }
300
301 static int
302 filt_eventfdwrite(struct knote *kn, long hint)
303 {
304 struct eventfd *efd = kn->kn_hook;
305 int ret;
306
307 mtx_assert(&efd->efd_lock, MA_OWNED);
308 kn->kn_data = (int64_t)(UINT64_MAX - 1 - efd->efd_count);
309 ret = UINT64_MAX - 1 > efd->efd_count;
310
311 return (ret);
312 }
313
314 static int
315 eventfd_ioctl(struct file *fp, u_long cmd, void *data,
316 struct ucred *active_cred, struct thread *td)
317 {
318 switch (cmd) {
319 case FIONBIO:
320 case FIOASYNC:
321 return (0);
322 }
323
324 return (ENOTTY);
325 }
326
327 static int
328 eventfd_stat(struct file *fp, struct stat *st, struct ucred *active_cred)
329 {
330 bzero((void *)st, sizeof *st);
331 st->st_mode = S_IFIFO;
332 return (0);
333 }
334
335 static int
336 eventfd_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
337 {
338 struct eventfd *efd = fp->f_data;
339
340 kif->kf_type = KF_TYPE_EVENTFD;
341 mtx_lock(&efd->efd_lock);
342 kif->kf_un.kf_eventfd.kf_eventfd_value = efd->efd_count;
343 kif->kf_un.kf_eventfd.kf_eventfd_flags = efd->efd_flags;
344 kif->kf_un.kf_eventfd.kf_eventfd_addr = (uintptr_t)efd;
345 mtx_unlock(&efd->efd_lock);
346 return (0);
347 }
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