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
122struct _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
131static LIST_HEAD(, _sem_st) named_sems = LIST_HEAD_INITIALIZER(&named_sems);
132#ifdef __LIBPTHREAD_SOURCE__
133static 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
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
159static inline intptr_t
160sem_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
169static void
170sem_free(sem_t sem)
171{
172
173	sem->ksem_magic = 0;
174	free(sem);
175}
176
177static int
178sem_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 */
196int
197sem_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
237int
238sem_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
267sem_t *
268sem_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
331int
332sem_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
360int
361sem_unlink(const char *name)
362{
363
364	return _ksem_unlink(name);
365}
366
367int
368sem_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
381int
382sem_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
395int
396sem_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
409int
410sem_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
423int
424sem_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