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