1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (C) 2010 David Xu <davidxu@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(s), this list of conditions and the following disclaimer as
12 * the first lines of this file unmodified other than the possible
13 * addition of one or more copyright notices.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice(s), this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
17 * distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
20 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
23 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
26 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
27 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
28 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
29 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include "namespace.h"
33 #include <sys/types.h>
34 #include <sys/queue.h>
35 #include <sys/mman.h>
36 #include <sys/stat.h>
37 #include <errno.h>
38 #include <machine/atomic.h>
39 #include <sys/umtx.h>
40 #include <limits.h>
41 #include <fcntl.h>
42 #include <pthread.h>
43 #include <stdarg.h>
44 #include <stdbool.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <time.h>
48 #include <semaphore.h>
49 #include <unistd.h>
50 #include "un-namespace.h"
51 #include "libc_private.h"
52
53 __weak_reference(_sem_close, sem_close);
54 __weak_reference(_sem_destroy, sem_destroy);
55 __weak_reference(_sem_getvalue, sem_getvalue);
56 __weak_reference(_sem_init, sem_init);
57 __weak_reference(_sem_open, sem_open);
58 __weak_reference(_sem_post, sem_post);
59 __weak_reference(_sem_timedwait, sem_timedwait);
60 __weak_reference(_sem_clockwait_np, sem_clockwait_np);
61 __weak_reference(_sem_trywait, sem_trywait);
62 __weak_reference(_sem_unlink, sem_unlink);
63 __weak_reference(_sem_wait, sem_wait);
64
65 #define SEM_PREFIX "/tmp/SEMD"
66 #define SEM_MAGIC ((u_int32_t)0x73656d32)
67
68 _Static_assert(SEM_VALUE_MAX <= USEM_MAX_COUNT, "SEM_VALUE_MAX too large");
69
70 struct sem_nameinfo {
71 int open_count;
72 char *name;
73 dev_t dev;
74 ino_t ino;
75 sem_t *sem;
76 LIST_ENTRY(sem_nameinfo) next;
77 };
78
79 static pthread_once_t once = PTHREAD_ONCE_INIT;
80 static pthread_mutex_t sem_llock;
81 static LIST_HEAD(, sem_nameinfo) sem_list = LIST_HEAD_INITIALIZER(sem_list);
82
83 static void
sem_prefork(void)84 sem_prefork(void)
85 {
86
87 _pthread_mutex_lock(&sem_llock);
88 }
89
90 static void
sem_postfork(void)91 sem_postfork(void)
92 {
93
94 _pthread_mutex_unlock(&sem_llock);
95 }
96
97 static void
sem_child_postfork(void)98 sem_child_postfork(void)
99 {
100
101 _pthread_mutex_unlock(&sem_llock);
102 }
103
104 static void
sem_module_init(void)105 sem_module_init(void)
106 {
107
108 _pthread_mutex_init(&sem_llock, NULL);
109 _pthread_atfork(sem_prefork, sem_postfork, sem_child_postfork);
110 }
111
112 static inline int
sem_check_validity(sem_t * sem)113 sem_check_validity(sem_t *sem)
114 {
115
116 if (sem->_magic == SEM_MAGIC)
117 return (0);
118 errno = EINVAL;
119 return (-1);
120 }
121
122 int
_sem_init(sem_t * sem,int pshared,unsigned int value)123 _sem_init(sem_t *sem, int pshared, unsigned int value)
124 {
125
126 if (value > SEM_VALUE_MAX) {
127 errno = EINVAL;
128 return (-1);
129 }
130
131 bzero(sem, sizeof(sem_t));
132 sem->_magic = SEM_MAGIC;
133 sem->_kern._count = (u_int32_t)value;
134 sem->_kern._flags = pshared ? USYNC_PROCESS_SHARED : 0;
135 return (0);
136 }
137
138 sem_t *
_sem_open(const char * name,int flags,...)139 _sem_open(const char *name, int flags, ...)
140 {
141 char path[PATH_MAX];
142 struct stat sb;
143 va_list ap;
144 struct sem_nameinfo *ni;
145 sem_t *sem, tmp;
146 int errsave, fd, len, mode, value;
147
148 ni = NULL;
149 sem = NULL;
150 fd = -1;
151 value = 0;
152
153 if (name[0] != '/') {
154 errno = EINVAL;
155 return (SEM_FAILED);
156 }
157 name++;
158 strcpy(path, SEM_PREFIX);
159 if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
160 errno = ENAMETOOLONG;
161 return (SEM_FAILED);
162 }
163 if (flags & ~(O_CREAT|O_EXCL)) {
164 errno = EINVAL;
165 return (SEM_FAILED);
166 }
167 if ((flags & O_CREAT) != 0) {
168 va_start(ap, flags);
169 mode = va_arg(ap, int);
170 value = va_arg(ap, int);
171 va_end(ap);
172 }
173 fd = -1;
174 _pthread_once(&once, sem_module_init);
175
176 _pthread_mutex_lock(&sem_llock);
177 LIST_FOREACH(ni, &sem_list, next) {
178 if (ni->name != NULL && strcmp(name, ni->name) == 0) {
179 fd = _open(path, flags | O_RDWR | O_CLOEXEC |
180 O_EXLOCK, mode);
181 if (fd == -1 || _fstat(fd, &sb) == -1) {
182 ni = NULL;
183 goto error;
184 }
185 if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT |
186 O_EXCL) || ni->dev != sb.st_dev ||
187 ni->ino != sb.st_ino) {
188 ni->name = NULL;
189 ni = NULL;
190 break;
191 }
192 ni->open_count++;
193 sem = ni->sem;
194 _pthread_mutex_unlock(&sem_llock);
195 _close(fd);
196 return (sem);
197 }
198 }
199
200 len = sizeof(*ni) + strlen(name) + 1;
201 ni = (struct sem_nameinfo *)malloc(len);
202 if (ni == NULL) {
203 errno = ENOSPC;
204 goto error;
205 }
206
207 ni->name = (char *)(ni+1);
208 strcpy(ni->name, name);
209
210 if (fd == -1) {
211 fd = _open(path, flags | O_RDWR | O_CLOEXEC | O_EXLOCK, mode);
212 if (fd == -1 || _fstat(fd, &sb) == -1)
213 goto error;
214 }
215 if (sb.st_size < sizeof(sem_t)) {
216 tmp._magic = SEM_MAGIC;
217 tmp._kern._count = value;
218 tmp._kern._flags = USYNC_PROCESS_SHARED | SEM_NAMED;
219 if (_write(fd, &tmp, sizeof(tmp)) != sizeof(tmp))
220 goto error;
221 }
222 flock(fd, LOCK_UN);
223 sem = mmap(NULL, sizeof(sem_t), PROT_READ | PROT_WRITE,
224 MAP_SHARED | MAP_NOSYNC, fd, 0);
225 if (sem == MAP_FAILED) {
226 sem = NULL;
227 if (errno == ENOMEM)
228 errno = ENOSPC;
229 goto error;
230 }
231 if (sem->_magic != SEM_MAGIC) {
232 errno = EINVAL;
233 goto error;
234 }
235 ni->open_count = 1;
236 ni->sem = sem;
237 ni->dev = sb.st_dev;
238 ni->ino = sb.st_ino;
239 LIST_INSERT_HEAD(&sem_list, ni, next);
240 _close(fd);
241 _pthread_mutex_unlock(&sem_llock);
242 return (sem);
243
244 error:
245 errsave = errno;
246 if (fd != -1)
247 _close(fd);
248 if (sem != NULL)
249 munmap(sem, sizeof(sem_t));
250 free(ni);
251 _pthread_mutex_unlock(&sem_llock);
252 errno = errsave;
253 return (SEM_FAILED);
254 }
255
256 int
_sem_close(sem_t * sem)257 _sem_close(sem_t *sem)
258 {
259 struct sem_nameinfo *ni;
260 bool last;
261
262 if (sem_check_validity(sem) != 0)
263 return (-1);
264
265 if (!(sem->_kern._flags & SEM_NAMED)) {
266 errno = EINVAL;
267 return (-1);
268 }
269
270 _pthread_once(&once, sem_module_init);
271
272 _pthread_mutex_lock(&sem_llock);
273 LIST_FOREACH(ni, &sem_list, next) {
274 if (sem == ni->sem) {
275 last = --ni->open_count == 0;
276 if (last)
277 LIST_REMOVE(ni, next);
278 _pthread_mutex_unlock(&sem_llock);
279 if (last) {
280 munmap(sem, sizeof(*sem));
281 free(ni);
282 }
283 return (0);
284 }
285 }
286 _pthread_mutex_unlock(&sem_llock);
287 errno = EINVAL;
288 return (-1);
289 }
290
291 int
_sem_unlink(const char * name)292 _sem_unlink(const char *name)
293 {
294 char path[PATH_MAX];
295
296 if (name[0] != '/') {
297 errno = ENOENT;
298 return -1;
299 }
300 name++;
301 strcpy(path, SEM_PREFIX);
302 if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
303 errno = ENAMETOOLONG;
304 return (-1);
305 }
306
307 return (unlink(path));
308 }
309
310 int
_sem_destroy(sem_t * sem)311 _sem_destroy(sem_t *sem)
312 {
313
314 if (sem_check_validity(sem) != 0)
315 return (-1);
316
317 if (sem->_kern._flags & SEM_NAMED) {
318 errno = EINVAL;
319 return (-1);
320 }
321 sem->_magic = 0;
322 return (0);
323 }
324
325 int
_sem_getvalue(sem_t * __restrict sem,int * __restrict sval)326 _sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
327 {
328
329 if (sem_check_validity(sem) != 0)
330 return (-1);
331
332 *sval = (int)USEM_COUNT(sem->_kern._count);
333 return (0);
334 }
335
336 static __inline int
usem_wake(struct _usem2 * sem)337 usem_wake(struct _usem2 *sem)
338 {
339
340 return (_umtx_op(sem, UMTX_OP_SEM2_WAKE, 0, NULL, NULL));
341 }
342
343 static __inline int
usem_wait(struct _usem2 * sem,clockid_t clock_id,int flags,const struct timespec * rqtp,struct timespec * rmtp)344 usem_wait(struct _usem2 *sem, clockid_t clock_id, int flags,
345 const struct timespec *rqtp, struct timespec *rmtp)
346 {
347 struct {
348 struct _umtx_time timeout;
349 struct timespec remain;
350 } tms;
351 void *tm_p;
352 size_t tm_size;
353 int retval;
354
355 if (rqtp == NULL) {
356 tm_p = NULL;
357 tm_size = 0;
358 } else {
359 tms.timeout._clockid = clock_id;
360 tms.timeout._flags = (flags & TIMER_ABSTIME) ? UMTX_ABSTIME : 0;
361 tms.timeout._timeout = *rqtp;
362 tm_p = &tms;
363 tm_size = sizeof(tms);
364 }
365 retval = _umtx_op(sem, UMTX_OP_SEM2_WAIT, 0, (void *)tm_size, tm_p);
366 if (retval == -1 && errno == EINTR && (flags & TIMER_ABSTIME) == 0 &&
367 rqtp != NULL && rmtp != NULL) {
368 *rmtp = tms.remain;
369 }
370
371 return (retval);
372 }
373
374 int
_sem_trywait(sem_t * sem)375 _sem_trywait(sem_t *sem)
376 {
377 int val;
378
379 if (sem_check_validity(sem) != 0)
380 return (-1);
381
382 while (USEM_COUNT(val = sem->_kern._count) > 0) {
383 if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
384 return (0);
385 }
386 errno = EAGAIN;
387 return (-1);
388 }
389
390 int
_sem_clockwait_np(sem_t * __restrict sem,clockid_t clock_id,int flags,const struct timespec * rqtp,struct timespec * rmtp)391 _sem_clockwait_np(sem_t * __restrict sem, clockid_t clock_id, int flags,
392 const struct timespec *rqtp, struct timespec *rmtp)
393 {
394 int val, retval;
395
396 if (sem_check_validity(sem) != 0)
397 return (-1);
398
399 retval = 0;
400 _pthread_testcancel();
401 for (;;) {
402 while (USEM_COUNT(val = sem->_kern._count) > 0) {
403 if (atomic_cmpset_acq_int(&sem->_kern._count, val,
404 val - 1))
405 return (0);
406 }
407
408 if (retval) {
409 _pthread_testcancel();
410 break;
411 }
412
413 /*
414 * The timeout argument is only supposed to
415 * be checked if the thread would have blocked.
416 */
417 if (rqtp != NULL) {
418 if (rqtp->tv_nsec >= 1000000000 || rqtp->tv_nsec < 0) {
419 errno = EINVAL;
420 return (-1);
421 }
422 }
423 _pthread_cancel_enter(1);
424 retval = usem_wait(&sem->_kern, clock_id, flags, rqtp, rmtp);
425 _pthread_cancel_leave(0);
426 }
427 return (retval);
428 }
429
430 int
_sem_timedwait(sem_t * __restrict sem,const struct timespec * __restrict abstime)431 _sem_timedwait(sem_t * __restrict sem,
432 const struct timespec * __restrict abstime)
433 {
434
435 return (_sem_clockwait_np(sem, CLOCK_REALTIME, TIMER_ABSTIME, abstime,
436 NULL));
437 };
438
439 int
_sem_wait(sem_t * sem)440 _sem_wait(sem_t *sem)
441 {
442
443 return (_sem_timedwait(sem, NULL));
444 }
445
446 /*
447 * POSIX:
448 * The sem_post() interface is reentrant with respect to signals and may be
449 * invoked from a signal-catching function.
450 * The implementation does not use lock, so it should be safe.
451 */
452 int
_sem_post(sem_t * sem)453 _sem_post(sem_t *sem)
454 {
455 unsigned int count;
456
457 if (sem_check_validity(sem) != 0)
458 return (-1);
459
460 do {
461 count = sem->_kern._count;
462 if (USEM_COUNT(count) + 1 > SEM_VALUE_MAX) {
463 errno = EOVERFLOW;
464 return (-1);
465 }
466 } while (!atomic_cmpset_rel_int(&sem->_kern._count, count, count + 1));
467 if (count & USEM_HAS_WAITERS)
468 usem_wake(&sem->_kern);
469 return (0);
470 }
471