1 /*
2 +----------------------------------------------------------------------+
3 | Copyright (c) The PHP Group |
4 +----------------------------------------------------------------------+
5 | This source file is subject to version 3.01 of the PHP license, |
6 | that is bundled with this package in the file LICENSE, and is |
7 | available through the world-wide-web at the following url: |
8 | https://www.php.net/license/3_01.txt |
9 | If you did not receive a copy of the PHP license and are unable to |
10 | obtain it through the world-wide-web, please send a note to |
11 | license@php.net so we can mail you a copy immediately. |
12 +----------------------------------------------------------------------+
13 | Authors: Tom May <tom@go2net.com> |
14 | Gavin Sherry <gavin@linuxworld.com.au> |
15 +----------------------------------------------------------------------+
16 */
17
18 #ifdef HAVE_CONFIG_H
19 #include "config.h"
20 #endif
21
22 #include "php.h"
23
24 #ifdef HAVE_SYSVSEM
25
26 #include <sys/types.h>
27 #include <sys/ipc.h>
28 #include <sys/sem.h>
29 #include <errno.h>
30
31 #include "sysvsem_arginfo.h"
32 #include "php_sysvsem.h"
33 #include "ext/standard/info.h"
34
35 #if !HAVE_SEMUN
36
37 union semun {
38 int val; /* value for SETVAL */
39 struct semid_ds *buf; /* buffer for IPC_STAT, IPC_SET */
40 unsigned short int *array; /* array for GETALL, SETALL */
41 struct seminfo *__buf; /* buffer for IPC_INFO */
42 };
43
44 #undef HAVE_SEMUN
45 #define HAVE_SEMUN 1
46
47 #endif
48
49 /* {{{ sysvsem_module_entry */
50 zend_module_entry sysvsem_module_entry = {
51 STANDARD_MODULE_HEADER,
52 "sysvsem",
53 ext_functions,
54 PHP_MINIT(sysvsem),
55 NULL,
56 NULL,
57 NULL,
58 PHP_MINFO(sysvsem),
59 PHP_SYSVSEM_VERSION,
60 STANDARD_MODULE_PROPERTIES
61 };
62 /* }}} */
63
64 #ifdef COMPILE_DL_SYSVSEM
65 ZEND_GET_MODULE(sysvsem)
66 #endif
67
68 /* Semaphore functions using System V semaphores. Each semaphore
69 * actually consists of three semaphores allocated as a unit under the
70 * same key. Semaphore 0 (SYSVSEM_SEM) is the actual semaphore, it is
71 * initialized to max_acquire and decremented as processes acquire it.
72 * The value of semaphore 1 (SYSVSEM_USAGE) is a count of the number
73 * of processes using the semaphore. After calling semget(), if a
74 * process finds that the usage count is 1, it will set the value of
75 * SYSVSEM_SEM to max_acquire. This allows max_acquire to be set and
76 * track the PHP code without having a global init routine or external
77 * semaphore init code. Except see the bug regarding a race condition
78 * php_sysvsem_get(). Semaphore 2 (SYSVSEM_SETVAL) serializes the
79 * calls to GETVAL SYSVSEM_USAGE and SETVAL SYSVSEM_SEM. It can be
80 * acquired only when it is zero.
81 */
82
83 #define SYSVSEM_SEM 0
84 #define SYSVSEM_USAGE 1
85 #define SYSVSEM_SETVAL 2
86
87 /* SysvSemaphore class */
88
89 zend_class_entry *sysvsem_ce;
90 static zend_object_handlers sysvsem_object_handlers;
91
sysvsem_from_obj(zend_object * obj)92 static inline sysvsem_sem *sysvsem_from_obj(zend_object *obj) {
93 return (sysvsem_sem *)((char *)(obj) - XtOffsetOf(sysvsem_sem, std));
94 }
95
96 #define Z_SYSVSEM_P(zv) sysvsem_from_obj(Z_OBJ_P(zv))
97
sysvsem_create_object(zend_class_entry * class_type)98 static zend_object *sysvsem_create_object(zend_class_entry *class_type) {
99 sysvsem_sem *intern = zend_object_alloc(sizeof(sysvsem_sem), class_type);
100
101 zend_object_std_init(&intern->std, class_type);
102 object_properties_init(&intern->std, class_type);
103 intern->std.handlers = &sysvsem_object_handlers;
104
105 return &intern->std;
106 }
107
sysvsem_get_constructor(zend_object * object)108 static zend_function *sysvsem_get_constructor(zend_object *object) {
109 zend_throw_error(NULL, "Cannot directly construct SysvSemaphore, use sem_get() instead");
110 return NULL;
111 }
112
sysvsem_free_obj(zend_object * object)113 static void sysvsem_free_obj(zend_object *object)
114 {
115 sysvsem_sem *sem_ptr = sysvsem_from_obj(object);
116 struct sembuf sop[2];
117 int opcount = 1;
118
119 /*
120 * if count == -1, semaphore has been removed
121 * Need better way to handle this
122 */
123 if (sem_ptr->count == -1 || !sem_ptr->auto_release) {
124 zend_object_std_dtor(&sem_ptr->std);
125 return;
126 }
127 /* Decrement the usage count. */
128
129 sop[0].sem_num = SYSVSEM_USAGE;
130 sop[0].sem_op = -1;
131 sop[0].sem_flg = SEM_UNDO;
132
133 /* Release the semaphore if it has been acquired but not released. */
134
135 if (sem_ptr->count) {
136
137 sop[1].sem_num = SYSVSEM_SEM;
138 sop[1].sem_op = sem_ptr->count;
139 sop[1].sem_flg = SEM_UNDO;
140
141 opcount++;
142 }
143
144 semop(sem_ptr->semid, sop, opcount);
145
146 zend_object_std_dtor(&sem_ptr->std);
147 }
148 /* }}} */
149
150 /* {{{ PHP_MINIT_FUNCTION */
PHP_MINIT_FUNCTION(sysvsem)151 PHP_MINIT_FUNCTION(sysvsem)
152 {
153 sysvsem_ce = register_class_SysvSemaphore();
154 sysvsem_ce->create_object = sysvsem_create_object;
155
156 memcpy(&sysvsem_object_handlers, &std_object_handlers, sizeof(zend_object_handlers));
157 sysvsem_object_handlers.offset = XtOffsetOf(sysvsem_sem, std);
158 sysvsem_object_handlers.free_obj = sysvsem_free_obj;
159 sysvsem_object_handlers.get_constructor = sysvsem_get_constructor;
160 sysvsem_object_handlers.clone_obj = NULL;
161 sysvsem_object_handlers.compare = zend_objects_not_comparable;
162
163 return SUCCESS;
164 }
165 /* }}} */
166
167 /* {{{ PHP_MINFO_FUNCTION */
PHP_MINFO_FUNCTION(sysvsem)168 PHP_MINFO_FUNCTION(sysvsem)
169 {
170 php_info_print_table_start();
171 php_info_print_table_row(2, "sysvsem support", "enabled");
172 php_info_print_table_end();
173 }
174 /* }}} */
175
176 #define SETVAL_WANTS_PTR
177
178 #if defined(_AIX)
179 #undef SETVAL_WANTS_PTR
180 #endif
181
182 /* {{{ Return an id for the semaphore with the given key, and allow max_acquire (default 1) processes to acquire it simultaneously */
PHP_FUNCTION(sem_get)183 PHP_FUNCTION(sem_get)
184 {
185 zend_long key, max_acquire = 1, perm = 0666;
186 bool auto_release = 1;
187 int semid;
188 struct sembuf sop[3];
189 int count;
190 sysvsem_sem *sem_ptr;
191
192 if (FAILURE == zend_parse_parameters(ZEND_NUM_ARGS(), "l|llb", &key, &max_acquire, &perm, &auto_release)) {
193 RETURN_THROWS();
194 }
195
196 /* Get/create the semaphore. Note that we rely on the semaphores
197 * being zeroed when they are created. Despite the fact that
198 * the(?) Linux semget() man page says they are not initialized,
199 * the kernel versions 2.0.x and 2.1.z do in fact zero them.
200 */
201
202 semid = semget(key, 3, perm|IPC_CREAT);
203 if (semid == -1) {
204 php_error_docref(NULL, E_WARNING, "Failed for key 0x" ZEND_XLONG_FMT ": %s", key, strerror(errno));
205 RETURN_FALSE;
206 }
207
208 /* Find out how many processes are using this semaphore. Note
209 * that on Linux (at least) there is a race condition here because
210 * semaphore undo on process exit is not atomic, so we could
211 * acquire SYSVSEM_SETVAL before a crashed process has decremented
212 * SYSVSEM_USAGE in which case count will be greater than it
213 * should be and we won't set max_acquire. Fortunately this
214 * doesn't actually matter in practice.
215 */
216
217 /* Wait for sem 1 to be zero . . . */
218
219 sop[0].sem_num = SYSVSEM_SETVAL;
220 sop[0].sem_op = 0;
221 sop[0].sem_flg = 0;
222
223 /* . . . and increment it so it becomes non-zero . . . */
224
225 sop[1].sem_num = SYSVSEM_SETVAL;
226 sop[1].sem_op = 1;
227 sop[1].sem_flg = SEM_UNDO;
228
229 /* . . . and increment the usage count. */
230
231 sop[2].sem_num = SYSVSEM_USAGE;
232 sop[2].sem_op = 1;
233 sop[2].sem_flg = SEM_UNDO;
234 while (semop(semid, sop, 3) == -1) {
235 if (errno != EINTR) {
236 php_error_docref(NULL, E_WARNING, "Failed acquiring SYSVSEM_SETVAL for key 0x" ZEND_XLONG_FMT ": %s", key, strerror(errno));
237 break;
238 }
239 }
240
241 /* Get the usage count. */
242 count = semctl(semid, SYSVSEM_USAGE, GETVAL, NULL);
243 if (count == -1) {
244 php_error_docref(NULL, E_WARNING, "Failed for key 0x" ZEND_XLONG_FMT ": %s", key, strerror(errno));
245 }
246
247 /* If we are the only user, then take this opportunity to set the max. */
248
249 if (count == 1) {
250 #if HAVE_SEMUN
251 /* This is correct for Linux which has union semun. */
252 union semun semarg;
253 semarg.val = max_acquire;
254 if (semctl(semid, SYSVSEM_SEM, SETVAL, semarg) == -1) {
255 php_error_docref(NULL, E_WARNING, "Failed for key 0x" ZEND_XLONG_FMT ": %s", key, strerror(errno));
256 }
257 #elif defined(SETVAL_WANTS_PTR)
258 /* This is correct for Solaris 2.6 which does not have union semun. */
259 if (semctl(semid, SYSVSEM_SEM, SETVAL, &max_acquire) == -1) {
260 php_error_docref(NULL, E_WARNING, "Failed for key 0x%lx: %s", key, strerror(errno));
261 }
262 #else
263 /* This works for i.e. AIX */
264 if (semctl(semid, SYSVSEM_SEM, SETVAL, max_acquire) == -1) {
265 php_error_docref(NULL, E_WARNING, "Failed for key 0x%lx: %s", key, strerror(errno));
266 }
267 #endif
268 }
269
270 /* Set semaphore 1 back to zero. */
271
272 sop[0].sem_num = SYSVSEM_SETVAL;
273 sop[0].sem_op = -1;
274 sop[0].sem_flg = SEM_UNDO;
275 while (semop(semid, sop, 1) == -1) {
276 if (errno != EINTR) {
277 php_error_docref(NULL, E_WARNING, "Failed releasing SYSVSEM_SETVAL for key 0x" ZEND_XLONG_FMT ": %s", key, strerror(errno));
278 break;
279 }
280 }
281
282 object_init_ex(return_value, sysvsem_ce);
283
284 sem_ptr = Z_SYSVSEM_P(return_value);
285 sem_ptr->key = key;
286 sem_ptr->semid = semid;
287 sem_ptr->count = 0;
288 sem_ptr->auto_release = (int) auto_release;
289 }
290 /* }}} */
291
292 /* {{{ php_sysvsem_semop */
php_sysvsem_semop(INTERNAL_FUNCTION_PARAMETERS,int acquire)293 static void php_sysvsem_semop(INTERNAL_FUNCTION_PARAMETERS, int acquire)
294 {
295 zval *arg_id;
296 bool nowait = 0;
297 sysvsem_sem *sem_ptr;
298 struct sembuf sop;
299
300 if (acquire) {
301 if (zend_parse_parameters(ZEND_NUM_ARGS(), "O|b", &arg_id, sysvsem_ce, &nowait) == FAILURE) {
302 RETURN_THROWS();
303 }
304 } else {
305 if (zend_parse_parameters(ZEND_NUM_ARGS(), "O", &arg_id, sysvsem_ce) == FAILURE) {
306 RETURN_THROWS();
307 }
308 }
309
310 sem_ptr = Z_SYSVSEM_P(arg_id);
311
312 if (!acquire && sem_ptr->count == 0) {
313 php_error_docref(NULL, E_WARNING, "SysV semaphore for key 0x%x is not currently acquired", sem_ptr->key);
314 RETURN_FALSE;
315 }
316
317 sop.sem_num = SYSVSEM_SEM;
318 sop.sem_op = acquire ? -1 : 1;
319 sop.sem_flg = SEM_UNDO | (nowait ? IPC_NOWAIT : 0);
320
321 while (semop(sem_ptr->semid, &sop, 1) == -1) {
322 if (errno != EINTR) {
323 if (errno != EAGAIN) {
324 php_error_docref(NULL, E_WARNING, "Failed to %s key 0x%x: %s", acquire ? "acquire" : "release", sem_ptr->key, strerror(errno));
325 }
326 RETURN_FALSE;
327 }
328 }
329
330 sem_ptr->count -= acquire ? -1 : 1;
331 RETURN_TRUE;
332 }
333 /* }}} */
334
335 /* {{{ Acquires the semaphore with the given id, blocking if necessary */
PHP_FUNCTION(sem_acquire)336 PHP_FUNCTION(sem_acquire)
337 {
338 php_sysvsem_semop(INTERNAL_FUNCTION_PARAM_PASSTHRU, 1);
339 }
340 /* }}} */
341
342 /* {{{ Releases the semaphore with the given id */
PHP_FUNCTION(sem_release)343 PHP_FUNCTION(sem_release)
344 {
345 php_sysvsem_semop(INTERNAL_FUNCTION_PARAM_PASSTHRU, 0);
346 }
347 /* }}} */
348
349 /* {{{ Removes semaphore from Unix systems */
350
351 /*
352 * contributed by Gavin Sherry gavin@linuxworld.com.au
353 * Fri Mar 16 00:50:13 EST 2001
354 */
355
PHP_FUNCTION(sem_remove)356 PHP_FUNCTION(sem_remove)
357 {
358 zval *arg_id;
359 sysvsem_sem *sem_ptr;
360 #if HAVE_SEMUN
361 union semun un;
362 struct semid_ds buf;
363 #endif
364
365 if (zend_parse_parameters(ZEND_NUM_ARGS(), "O", &arg_id, sysvsem_ce) == FAILURE) {
366 RETURN_THROWS();
367 }
368
369 sem_ptr = Z_SYSVSEM_P(arg_id);
370
371 #if HAVE_SEMUN
372 un.buf = &buf;
373 if (semctl(sem_ptr->semid, 0, IPC_STAT, un) < 0) {
374 #else
375 if (semctl(sem_ptr->semid, 0, IPC_STAT, NULL) < 0) {
376 #endif
377 php_error_docref(NULL, E_WARNING, "SysV semaphore for key 0x%x does not (any longer) exist", sem_ptr->key);
378 RETURN_FALSE;
379 }
380
381 #if HAVE_SEMUN
382 if (semctl(sem_ptr->semid, 0, IPC_RMID, un) < 0) {
383 #else
384 if (semctl(sem_ptr->semid, 0, IPC_RMID, NULL) < 0) {
385 #endif
386 php_error_docref(NULL, E_WARNING, "Failed for SysV semaphore for key 0x%x: %s", sem_ptr->key, strerror(errno));
387 RETURN_FALSE;
388 }
389
390 /* let release_sysvsem_sem know we have removed
391 * the semaphore to avoid issues with releasing.
392 */
393
394 sem_ptr->count = -1;
395 RETURN_TRUE;
396 }
397
398 /* }}} */
399
400 #endif /* HAVE_SYSVSEM */
401
