1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
29 #include <sys/systm.h>
30 #include <sys/kernel.h>
31 #include <sys/malloc.h>
32 #include <sys/limits.h>
33 #include <sys/lock.h>
34 #include <sys/mutex.h>
35 #include <sys/types.h>
36 #include <sys/user.h>
37 #include <sys/fcntl.h>
38 #include <sys/file.h>
39 #include <sys/filedesc.h>
40 #include <sys/filio.h>
41 #include <sys/stat.h>
42 #include <sys/errno.h>
43 #include <sys/event.h>
44 #include <sys/poll.h>
45 #include <sys/proc.h>
46 #include <sys/uio.h>
47 #include <sys/selinfo.h>
48 #include <sys/eventfd.h>
49
50 #include <security/audit/audit.h>
51
52 _Static_assert(EFD_CLOEXEC == O_CLOEXEC, "Mismatched EFD_CLOEXEC");
53 _Static_assert(EFD_NONBLOCK == O_NONBLOCK, "Mismatched EFD_NONBLOCK");
54
55 MALLOC_DEFINE(M_EVENTFD, "eventfd", "eventfd structures");
56
57 static fo_rdwr_t eventfd_read;
58 static fo_rdwr_t eventfd_write;
59 static fo_ioctl_t eventfd_ioctl;
60 static fo_poll_t eventfd_poll;
61 static fo_kqfilter_t eventfd_kqfilter;
62 static fo_stat_t eventfd_stat;
63 static fo_close_t eventfd_close;
64 static fo_fill_kinfo_t eventfd_fill_kinfo;
65
66 static struct fileops eventfdops = {
67 .fo_read = eventfd_read,
68 .fo_write = eventfd_write,
69 .fo_truncate = invfo_truncate,
70 .fo_ioctl = eventfd_ioctl,
71 .fo_poll = eventfd_poll,
72 .fo_kqfilter = eventfd_kqfilter,
73 .fo_stat = eventfd_stat,
74 .fo_close = eventfd_close,
75 .fo_chmod = invfo_chmod,
76 .fo_chown = invfo_chown,
77 .fo_sendfile = invfo_sendfile,
78 .fo_fill_kinfo = eventfd_fill_kinfo,
79 .fo_cmp = file_kcmp_generic,
80 .fo_flags = DFLAG_PASSABLE
81 };
82
83 static void filt_eventfddetach(struct knote *kn);
84 static int filt_eventfdread(struct knote *kn, long hint);
85 static int filt_eventfdwrite(struct knote *kn, long hint);
86
87 static struct filterops eventfd_rfiltops = {
88 .f_isfd = 1,
89 .f_detach = filt_eventfddetach,
90 .f_event = filt_eventfdread
91 };
92
93 static struct filterops eventfd_wfiltops = {
94 .f_isfd = 1,
95 .f_detach = filt_eventfddetach,
96 .f_event = filt_eventfdwrite
97 };
98
99 struct eventfd {
100 eventfd_t efd_count;
101 uint32_t efd_flags;
102 struct selinfo efd_sel;
103 struct mtx efd_lock;
104 };
105
106 int
eventfd_create_file(struct thread * td,struct file * fp,uint32_t initval,int flags)107 eventfd_create_file(struct thread *td, struct file *fp, uint32_t initval,
108 int flags)
109 {
110 struct eventfd *efd;
111 int fflags;
112
113 AUDIT_ARG_FFLAGS(flags);
114 AUDIT_ARG_VALUE(initval);
115
116 efd = malloc(sizeof(*efd), M_EVENTFD, M_WAITOK | M_ZERO);
117 efd->efd_flags = flags;
118 efd->efd_count = initval;
119 mtx_init(&efd->efd_lock, "eventfd", NULL, MTX_DEF);
120 knlist_init_mtx(&efd->efd_sel.si_note, &efd->efd_lock);
121
122 fflags = FREAD | FWRITE;
123 if ((flags & EFD_NONBLOCK) != 0)
124 fflags |= FNONBLOCK;
125 finit(fp, fflags, DTYPE_EVENTFD, efd, &eventfdops);
126
127 return (0);
128 }
129
130 static int
eventfd_close(struct file * fp,struct thread * td)131 eventfd_close(struct file *fp, struct thread *td)
132 {
133 struct eventfd *efd;
134
135 efd = fp->f_data;
136 seldrain(&efd->efd_sel);
137 knlist_destroy(&efd->efd_sel.si_note);
138 mtx_destroy(&efd->efd_lock);
139 free(efd, M_EVENTFD);
140 return (0);
141 }
142
143 static int
eventfd_read(struct file * fp,struct uio * uio,struct ucred * active_cred,int flags,struct thread * td)144 eventfd_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
145 int flags, struct thread *td)
146 {
147 struct eventfd *efd;
148 eventfd_t count;
149 int error;
150
151 if (uio->uio_resid < sizeof(eventfd_t))
152 return (EINVAL);
153
154 error = 0;
155 efd = fp->f_data;
156 mtx_lock(&efd->efd_lock);
157 while (error == 0 && efd->efd_count == 0) {
158 if ((fp->f_flag & FNONBLOCK) != 0) {
159 mtx_unlock(&efd->efd_lock);
160 return (EAGAIN);
161 }
162 error = mtx_sleep(&efd->efd_count, &efd->efd_lock, PCATCH,
163 "efdrd", 0);
164 }
165 if (error == 0) {
166 MPASS(efd->efd_count > 0);
167 if ((efd->efd_flags & EFD_SEMAPHORE) != 0) {
168 count = 1;
169 --efd->efd_count;
170 } else {
171 count = efd->efd_count;
172 efd->efd_count = 0;
173 }
174 KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
175 selwakeup(&efd->efd_sel);
176 wakeup(&efd->efd_count);
177 mtx_unlock(&efd->efd_lock);
178 error = uiomove(&count, sizeof(eventfd_t), uio);
179 } else
180 mtx_unlock(&efd->efd_lock);
181
182 return (error);
183 }
184
185 static int
eventfd_write(struct file * fp,struct uio * uio,struct ucred * active_cred,int flags,struct thread * td)186 eventfd_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
187 int flags, struct thread *td)
188 {
189 struct eventfd *efd;
190 eventfd_t count;
191 int error;
192
193 if (uio->uio_resid < sizeof(eventfd_t))
194 return (EINVAL);
195
196 error = uiomove(&count, sizeof(eventfd_t), uio);
197 if (error != 0)
198 return (error);
199 if (count == UINT64_MAX)
200 return (EINVAL);
201
202 efd = fp->f_data;
203 mtx_lock(&efd->efd_lock);
204 retry:
205 if (UINT64_MAX - efd->efd_count <= count) {
206 if ((fp->f_flag & FNONBLOCK) != 0) {
207 mtx_unlock(&efd->efd_lock);
208 /* Do not not return the number of bytes written */
209 uio->uio_resid += sizeof(eventfd_t);
210 return (EAGAIN);
211 }
212 error = mtx_sleep(&efd->efd_count, &efd->efd_lock,
213 PCATCH, "efdwr", 0);
214 if (error == 0)
215 goto retry;
216 }
217 if (error == 0) {
218 MPASS(UINT64_MAX - efd->efd_count > count);
219 efd->efd_count += count;
220 KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
221 selwakeup(&efd->efd_sel);
222 wakeup(&efd->efd_count);
223 }
224 mtx_unlock(&efd->efd_lock);
225
226 return (error);
227 }
228
229 static int
eventfd_poll(struct file * fp,int events,struct ucred * active_cred,struct thread * td)230 eventfd_poll(struct file *fp, int events, struct ucred *active_cred,
231 struct thread *td)
232 {
233 struct eventfd *efd;
234 int revents;
235
236 efd = fp->f_data;
237 revents = 0;
238 mtx_lock(&efd->efd_lock);
239 if ((events & (POLLIN | POLLRDNORM)) != 0 && efd->efd_count > 0)
240 revents |= events & (POLLIN | POLLRDNORM);
241 if ((events & (POLLOUT | POLLWRNORM)) != 0 && UINT64_MAX - 1 >
242 efd->efd_count)
243 revents |= events & (POLLOUT | POLLWRNORM);
244 if (revents == 0)
245 selrecord(td, &efd->efd_sel);
246 mtx_unlock(&efd->efd_lock);
247
248 return (revents);
249 }
250
251 static int
eventfd_kqfilter(struct file * fp,struct knote * kn)252 eventfd_kqfilter(struct file *fp, struct knote *kn)
253 {
254 struct eventfd *efd = fp->f_data;
255
256 mtx_lock(&efd->efd_lock);
257 switch (kn->kn_filter) {
258 case EVFILT_READ:
259 kn->kn_fop = &eventfd_rfiltops;
260 break;
261 case EVFILT_WRITE:
262 kn->kn_fop = &eventfd_wfiltops;
263 break;
264 default:
265 mtx_unlock(&efd->efd_lock);
266 return (EINVAL);
267 }
268
269 kn->kn_hook = efd;
270 knlist_add(&efd->efd_sel.si_note, kn, 1);
271 mtx_unlock(&efd->efd_lock);
272
273 return (0);
274 }
275
276 static void
filt_eventfddetach(struct knote * kn)277 filt_eventfddetach(struct knote *kn)
278 {
279 struct eventfd *efd = kn->kn_hook;
280
281 mtx_lock(&efd->efd_lock);
282 knlist_remove(&efd->efd_sel.si_note, kn, 1);
283 mtx_unlock(&efd->efd_lock);
284 }
285
286 static int
filt_eventfdread(struct knote * kn,long hint)287 filt_eventfdread(struct knote *kn, long hint)
288 {
289 struct eventfd *efd = kn->kn_hook;
290 int ret;
291
292 mtx_assert(&efd->efd_lock, MA_OWNED);
293 kn->kn_data = (int64_t)efd->efd_count;
294 ret = efd->efd_count > 0;
295
296 return (ret);
297 }
298
299 static int
filt_eventfdwrite(struct knote * kn,long hint)300 filt_eventfdwrite(struct knote *kn, long hint)
301 {
302 struct eventfd *efd = kn->kn_hook;
303 int ret;
304
305 mtx_assert(&efd->efd_lock, MA_OWNED);
306 kn->kn_data = (int64_t)(UINT64_MAX - 1 - efd->efd_count);
307 ret = UINT64_MAX - 1 > efd->efd_count;
308
309 return (ret);
310 }
311
312 static int
eventfd_ioctl(struct file * fp,u_long cmd,void * data,struct ucred * active_cred,struct thread * td)313 eventfd_ioctl(struct file *fp, u_long cmd, void *data,
314 struct ucred *active_cred, struct thread *td)
315 {
316 switch (cmd) {
317 case FIONBIO:
318 case FIOASYNC:
319 return (0);
320 }
321
322 return (ENOTTY);
323 }
324
325 static int
eventfd_stat(struct file * fp,struct stat * st,struct ucred * active_cred)326 eventfd_stat(struct file *fp, struct stat *st, struct ucred *active_cred)
327 {
328 bzero((void *)st, sizeof *st);
329 st->st_mode = S_IFIFO;
330 return (0);
331 }
332
333 static int
eventfd_fill_kinfo(struct file * fp,struct kinfo_file * kif,struct filedesc * fdp)334 eventfd_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
335 {
336 struct eventfd *efd = fp->f_data;
337
338 kif->kf_type = KF_TYPE_EVENTFD;
339 mtx_lock(&efd->efd_lock);
340 kif->kf_un.kf_eventfd.kf_eventfd_value = efd->efd_count;
341 kif->kf_un.kf_eventfd.kf_eventfd_flags = efd->efd_flags;
342 kif->kf_un.kf_eventfd.kf_eventfd_addr = (uintptr_t)efd;
343 mtx_unlock(&efd->efd_lock);
344 return (0);
345 }
346