1 /* $NetBSD: sem.c,v 1.9 2019/02/21 21:33:34 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2003, 2019 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE 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 BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 /*
33 * Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions
38 * are met:
39 * 1. Redistributions of source code must retain the above copyright
40 * notice(s), this list of conditions and the following disclaimer as
41 * the first lines of this file unmodified other than the possible
42 * addition of one or more copyright notices.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice(s), this list of conditions and the following disclaimer in
45 * the documentation and/or other materials provided with the
46 * distribution.
47 *
48 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
49 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
50 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
51 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
52 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
53 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
54 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
55 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
56 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
57 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
58 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
59 */
60
61 #include <sys/cdefs.h>
62 __RCSID("$NetBSD: sem.c,v 1.9 2019/02/21 21:33:34 christos Exp $");
63
64 #ifndef __LIBPTHREAD_SOURCE__
65 /*
66 * There is no longer any difference between the libpthread and the librt
67 * versions of sem.c; both are fully kernel-assisted via the _ksem_*()
68 * system calls. The only difference is the need to lock some internal
69 * data structures in the pthread version, which could be achieved by
70 * different means. However, in order to maintain binary compatibility
71 * with applications that use POSIX semaphores and linked against only
72 * libpthread, we continue to maintain a copy of the implementation here
73 * that does not depend on any additional libraries (other than libc).
74 */
75 #define sem_init _librt_sem_init
76 #define sem_destroy _librt_sem_destroy
77 #define sem_open _librt_sem_open
78 #define sem_close _librt_sem_close
79 #define sem_unlink _librt_sem_unlink
80 #define sem_wait _librt_sem_wait
81 #define sem_timedwait _librt_sem_timedwait
82 #define sem_trywait _librt_sem_trywait
83 #define sem_post _librt_sem_post
84 #define sem_getvalue _librt_sem_getvalue
85 #endif /* ! __LIBPTHREAD_SOURCE__ */
86
87 #undef _LIBC
88 #define _LIBC
89
90 #include <sys/types.h>
91 #include <sys/ksem.h>
92 #include <sys/queue.h>
93 #include <stdlib.h>
94 #include <errno.h>
95 #include <fcntl.h>
96 #include <stdint.h>
97 #include <semaphore.h>
98 #include <stdarg.h>
99
100 #ifdef __LIBPTHREAD_SOURCE__
101 #include "pthread.h"
102 #endif /* __LIBPTHREAD_SOURCE__ */
103
104 #define SEM_NAMED 0x4e414d44U /* 'NAMD' */
105 #define SEM_MAGIC 0x90af0421U
106 #define SEM_MAGIC_NAMED (SEM_MAGIC ^ SEM_NAMED)
107
108 #define SEMID_IS_KSEMID(id) (((uint32_t)(id) & KSEM_MARKER_MASK) \
109 == KSEM_PSHARED_MARKER)
110 #define SEM_IS_KSEMID(k) SEMID_IS_KSEMID((intptr_t)(k))
111
112
113 #define SEM_IS_UNNAMED(k) (SEM_IS_KSEMID(k) || \
114 (k)->ksem_magic == SEM_MAGIC)
115
116 #define SEM_IS_NAMED(k) (!SEM_IS_UNNAMED(k))
117
118 #define SEM_MAGIC_OK(k) (SEM_IS_KSEMID(k) || \
119 (k)->ksem_magic == SEM_MAGIC || \
120 (k)->ksem_magic == SEM_MAGIC_NAMED)
121
122 struct _sem_st {
123 unsigned int ksem_magic;
124 intptr_t ksem_semid;
125
126 /* Used only to de-dup named semaphores. */
127 LIST_ENTRY(_sem_st) ksem_list;
128 sem_t *ksem_identity;
129 };
130
131 static LIST_HEAD(, _sem_st) named_sems = LIST_HEAD_INITIALIZER(&named_sems);
132 #ifdef __LIBPTHREAD_SOURCE__
133 static pthread_mutex_t named_sems_mtx = PTHREAD_MUTEX_INITIALIZER;
134
135 #define LOCK_NAMED_SEMS() pthread_mutex_lock(&named_sems_mtx)
136 #define UNLOCK_NAMED_SEMS() pthread_mutex_unlock(&named_sems_mtx)
137 #else /* ! __LIBPTHREAD_SOURCE__ */
138 #define LOCK_NAMED_SEMS() __nothing
139 #define UNLOCK_NAMED_SEMS() __nothing
140 #endif /* __LIBPTHREAD_SOURCE__ */
141
142 #ifndef __LIBPTHREAD_SOURCE__
143 #ifdef __weak_alias
__weak_alias(sem_init,_librt_sem_init)144 __weak_alias(sem_init,_librt_sem_init)
145 __weak_alias(sem_destroy,_librt_sem_destroy)
146 __weak_alias(sem_open,_librt_sem_open)
147 __weak_alias(sem_close,_librt_sem_close)
148 __weak_alias(sem_unlink,_librt_sem_unlink)
149 __weak_alias(sem_wait,_librt_sem_wait)
150 __weak_alias(sem_timedwait,_librt_sem_timedwait)
151 __weak_alias(sem_trywait,_librt_sem_trywait)
152 __weak_alias(sem_post,_librt_sem_post)
153 __weak_alias(sem_getvalue,_librt_sem_getvalue)
154 #else
155 #error Weak aliases required to build POSIX semaphore support.
156 #endif /* __weak_alias */
157 #endif /* __LIBPTHREAD_SOURCE__ */
158
159 static inline intptr_t
160 sem_to_semid(sem_t *sem)
161 {
162
163 if (SEM_IS_KSEMID(*sem))
164 return (intptr_t)*sem;
165
166 return (*sem)->ksem_semid;
167 }
168
169 static void
sem_free(sem_t sem)170 sem_free(sem_t sem)
171 {
172
173 sem->ksem_magic = 0;
174 free(sem);
175 }
176
177 static int
sem_alloc(unsigned int value,intptr_t semid,unsigned int magic,sem_t * semp)178 sem_alloc(unsigned int value, intptr_t semid, unsigned int magic, sem_t *semp)
179 {
180 sem_t sem;
181
182 if (value > SEM_VALUE_MAX)
183 return EINVAL;
184
185 if ((sem = malloc(sizeof(struct _sem_st))) == NULL)
186 return ENOSPC;
187
188 sem->ksem_magic = magic;
189 sem->ksem_semid = semid;
190
191 *semp = sem;
192 return 0;
193 }
194
195 /* ARGSUSED */
196 int
sem_init(sem_t * sem,int pshared,unsigned int value)197 sem_init(sem_t *sem, int pshared, unsigned int value)
198 {
199 intptr_t semid = pshared ? KSEM_PSHARED : 0;
200 int error;
201
202 if (_ksem_init(value, &semid) == -1)
203 return -1;
204
205 /*
206 * pshared anonymous semaphores are treated a little differently.
207 * We don't allocate a sem structure and return a pointer to it.
208 * That pointer might live in the shared memory segment that's
209 * shared between processes, but the _sem_st that contains the
210 * important bits certainly would not be.
211 *
212 * So, instead, we return the ksem ID given to us by the kernel.
213 * The kernel has arranged for the least-significant bit of the
214 * ksem ID to always be 1 so as to ensure we can always tell
215 * these IDs apart from the pointers that we vend out for other
216 * non-pshared semaphores.
217 */
218 if (pshared) {
219 if (!SEMID_IS_KSEMID(semid)) {
220 _ksem_destroy(semid);
221 errno = ENOTSUP;
222 return -1;
223 }
224 *sem = (sem_t)semid;
225 return 0;
226 }
227
228 if ((error = sem_alloc(value, semid, SEM_MAGIC, sem)) != 0) {
229 _ksem_destroy(semid);
230 errno = error;
231 return -1;
232 }
233
234 return 0;
235 }
236
237 int
sem_destroy(sem_t * sem)238 sem_destroy(sem_t *sem)
239 {
240 int error, save_errno;
241
242 #ifdef ERRORCHECK
243 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
244 errno = EINVAL;
245 return -1;
246 }
247 #endif
248
249 if (SEM_IS_KSEMID(*sem)) {
250 error = _ksem_destroy((intptr_t)*sem);
251 } else {
252 if (SEM_IS_NAMED(*sem)) {
253 errno = EINVAL;
254 return -1;
255 }
256
257 error = _ksem_destroy((*sem)->ksem_semid);
258 save_errno = errno;
259 sem_free(*sem);
260 if (error == -1)
261 errno = save_errno;
262 }
263
264 return error;
265 }
266
267 sem_t *
sem_open(const char * name,int oflag,...)268 sem_open(const char *name, int oflag, ...)
269 {
270 sem_t *sem, s;
271 intptr_t semid;
272 mode_t mode;
273 unsigned int value;
274 int error;
275 va_list ap;
276
277 mode = 0;
278 value = 0;
279
280 if (oflag & O_CREAT) {
281 va_start(ap, oflag);
282 mode = va_arg(ap, int);
283 value = va_arg(ap, unsigned int);
284 va_end(ap);
285 }
286
287 /*
288 * We can be lazy and let the kernel handle the oflag,
289 * we'll just merge duplicate IDs into our list.
290 */
291 if (_ksem_open(name, oflag, mode, value, &semid) == -1)
292 return SEM_FAILED;
293
294 /*
295 * Search for a duplicate ID, we must return the same sem_t *
296 * if we locate one.
297 */
298 LOCK_NAMED_SEMS();
299 LIST_FOREACH(s, &named_sems, ksem_list) {
300 if (s->ksem_semid == semid) {
301 UNLOCK_NAMED_SEMS();
302 return s->ksem_identity;
303 }
304 }
305
306 if ((sem = malloc(sizeof(*sem))) == NULL) {
307 error = ENOSPC;
308 goto bad;
309 }
310 if ((error = sem_alloc(value, semid, SEM_MAGIC_NAMED, sem)) != 0)
311 goto bad;
312
313 LIST_INSERT_HEAD(&named_sems, *sem, ksem_list);
314 UNLOCK_NAMED_SEMS();
315 (*sem)->ksem_identity = sem;
316
317 return sem;
318
319 bad:
320 UNLOCK_NAMED_SEMS();
321 _ksem_close(semid);
322 if (sem != NULL) {
323 if (*sem != NULL)
324 sem_free(*sem);
325 free(sem);
326 }
327 errno = error;
328 return SEM_FAILED;
329 }
330
331 int
sem_close(sem_t * sem)332 sem_close(sem_t *sem)
333 {
334 int error, save_errno;
335
336 #ifdef ERRORCHECK
337 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
338 errno = EINVAL;
339 return -1;
340 }
341 #endif
342
343 if (!SEM_IS_NAMED(*sem)) {
344 errno = EINVAL;
345 return -1;
346 }
347
348 LOCK_NAMED_SEMS();
349 error = _ksem_close((*sem)->ksem_semid);
350 LIST_REMOVE((*sem), ksem_list);
351 save_errno = errno;
352 UNLOCK_NAMED_SEMS();
353 sem_free(*sem);
354 free(sem);
355 if (error == -1)
356 errno = save_errno;
357 return error;
358 }
359
360 int
sem_unlink(const char * name)361 sem_unlink(const char *name)
362 {
363
364 return _ksem_unlink(name);
365 }
366
367 int
sem_wait(sem_t * sem)368 sem_wait(sem_t *sem)
369 {
370
371 #ifdef ERRORCHECK
372 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
373 errno = EINVAL;
374 return -1;
375 }
376 #endif
377
378 return _ksem_wait(sem_to_semid(sem));
379 }
380
381 int
sem_timedwait(sem_t * sem,const struct timespec * __restrict abstime)382 sem_timedwait(sem_t *sem, const struct timespec * __restrict abstime)
383 {
384
385 #ifdef ERRORCHECK
386 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
387 errno = EINVAL;
388 return -1;
389 }
390 #endif
391
392 return _ksem_timedwait(sem_to_semid(sem), abstime);
393 }
394
395 int
sem_trywait(sem_t * sem)396 sem_trywait(sem_t *sem)
397 {
398
399 #ifdef ERRORCHECK
400 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
401 errno = EINVAL;
402 return -1;
403 }
404 #endif
405
406 return _ksem_trywait(sem_to_semid(sem));
407 }
408
409 int
sem_post(sem_t * sem)410 sem_post(sem_t *sem)
411 {
412
413 #ifdef ERRORCHECK
414 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
415 errno = EINVAL;
416 return -1;
417 }
418 #endif
419
420 return _ksem_post(sem_to_semid(sem));
421 }
422
423 int
sem_getvalue(sem_t * __restrict sem,int * __restrict sval)424 sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
425 {
426
427 #ifdef ERRORCHECK
428 if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
429 errno = EINVAL;
430 return -1;
431 }
432 #endif
433
434 return _ksem_getvalue(sem_to_semid(sem), sval);
435 }
436