1 /*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
6 * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
7 * This code underwent a massive rewrite in order to solve some problems
8 * with the original code. In particular the original code failed to
9 * wake up processes that were waiting for semval to go to 0 if the
10 * value went to 0 and was then incremented rapidly enough. In solving
11 * this problem I have also modified the implementation so that it
12 * processes pending operations in a FIFO manner, thus give a guarantee
13 * that processes waiting for a lock on the semaphore won't starve
14 * unless another locking process fails to unlock.
15 * In addition the following two changes in behavior have been introduced:
16 * - The original implementation of semop returned the value
17 * last semaphore element examined on success. This does not
18 * match the manual page specifications, and effectively
19 * allows the user to read the semaphore even if they do not
20 * have read permissions. The implementation now returns 0
21 * on success as stated in the manual page.
22 * - There is some confusion over whether the set of undo adjustments
23 * to be performed at exit should be done in an atomic manner.
24 * That is, if we are attempting to decrement the semval should we queue
25 * up and wait until we can do so legally?
26 * The original implementation attempted to do this.
27 * The current implementation does not do so. This is because I don't
28 * think it is the right thing (TM) to do, and because I couldn't
29 * see a clean way to get the old behavior with the new design.
30 * The POSIX standard and SVID should be consulted to determine
31 * what behavior is mandated.
32 *
33 * Further notes on refinement (Christoph Rohland, December 1998):
34 * - The POSIX standard says, that the undo adjustments simply should
35 * redo. So the current implementation is o.K.
36 * - The previous code had two flaws:
37 * 1) It actively gave the semaphore to the next waiting process
38 * sleeping on the semaphore. Since this process did not have the
39 * cpu this led to many unnecessary context switches and bad
40 * performance. Now we only check which process should be able to
41 * get the semaphore and if this process wants to reduce some
42 * semaphore value we simply wake it up without doing the
43 * operation. So it has to try to get it later. Thus e.g. the
44 * running process may reacquire the semaphore during the current
45 * time slice. If it only waits for zero or increases the semaphore,
46 * we do the operation in advance and wake it up.
47 * 2) It did not wake up all zero waiting processes. We try to do
48 * better but only get the semops right which only wait for zero or
49 * increase. If there are decrement operations in the operations
50 * array we do the same as before.
51 *
52 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
53 *
54 * SMP-threaded, sysctl's added
55 * (c) 1999 Manfred Spraul <manfreds@colorfullife.com>
56 * Enforced range limit on SEM_UNDO
57 * (c) 2001 Red Hat Inc <alan@redhat.com>
58 */
59
60 #include <linux/config.h>
61 #include <linux/slab.h>
62 #include <linux/spinlock.h>
63 #include <linux/init.h>
64 #include <linux/proc_fs.h>
65 #include <linux/time.h>
66 #include <asm/uaccess.h>
67 #include "util.h"
68
69
70 #define sem_lock(id) ((struct sem_array*)ipc_lock(&sem_ids,id))
71 #define sem_unlock(id) ipc_unlock(&sem_ids,id)
72 #define sem_rmid(id) ((struct sem_array*)ipc_rmid(&sem_ids,id))
73 #define sem_checkid(sma, semid) \
74 ipc_checkid(&sem_ids,&sma->sem_perm,semid)
75 #define sem_buildid(id, seq) \
76 ipc_buildid(&sem_ids, id, seq)
77 static struct ipc_ids sem_ids;
78
79 static int newary (key_t, int, int);
80 static void freeary (int id);
81 #ifdef CONFIG_PROC_FS
82 static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
83 #endif
84
85 #define SEMMSL_FAST 256 /* 512 bytes on stack */
86 #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
87
88 /*
89 * linked list protection:
90 * sem_undo.id_next,
91 * sem_array.sem_pending{,last},
92 * sem_array.sem_undo: sem_lock() for read/write
93 * sem_undo.proc_next: only "current" is allowed to read/write that field.
94 *
95 */
96
97 int sem_ctls[4] = {SEMMSL, SEMMNS, SEMOPM, SEMMNI};
98 #define sc_semmsl (sem_ctls[0])
99 #define sc_semmns (sem_ctls[1])
100 #define sc_semopm (sem_ctls[2])
101 #define sc_semmni (sem_ctls[3])
102
103 static int used_sems;
104
sem_init(void)105 void __init sem_init (void)
106 {
107 used_sems = 0;
108 ipc_init_ids(&sem_ids,sc_semmni);
109
110 #ifdef CONFIG_PROC_FS
111 create_proc_read_entry("sysvipc/sem", 0, 0, sysvipc_sem_read_proc, NULL);
112 #endif
113 }
114
newary(key_t key,int nsems,int semflg)115 static int newary (key_t key, int nsems, int semflg)
116 {
117 int id;
118 struct sem_array *sma;
119 int size;
120
121 if (!nsems)
122 return -EINVAL;
123 if (used_sems + nsems > sc_semmns)
124 return -ENOSPC;
125
126 size = sizeof (*sma) + nsems * sizeof (struct sem);
127 sma = (struct sem_array *) ipc_alloc(size);
128 if (!sma) {
129 return -ENOMEM;
130 }
131 memset (sma, 0, size);
132 id = ipc_addid(&sem_ids, &sma->sem_perm, sc_semmni);
133 if(id == -1) {
134 ipc_free(sma, size);
135 return -ENOSPC;
136 }
137 used_sems += nsems;
138
139 sma->sem_perm.mode = (semflg & S_IRWXUGO);
140 sma->sem_perm.key = key;
141
142 sma->sem_base = (struct sem *) &sma[1];
143 /* sma->sem_pending = NULL; */
144 sma->sem_pending_last = &sma->sem_pending;
145 /* sma->undo = NULL; */
146 sma->sem_nsems = nsems;
147 sma->sem_ctime = CURRENT_TIME;
148 sem_unlock(id);
149
150 return sem_buildid(id, sma->sem_perm.seq);
151 }
152
sys_semget(key_t key,int nsems,int semflg)153 asmlinkage long sys_semget (key_t key, int nsems, int semflg)
154 {
155 int id, err = -EINVAL;
156 struct sem_array *sma;
157
158 if (nsems < 0 || nsems > sc_semmsl)
159 return -EINVAL;
160 down(&sem_ids.sem);
161
162 if (key == IPC_PRIVATE) {
163 err = newary(key, nsems, semflg);
164 } else if ((id = ipc_findkey(&sem_ids, key)) == -1) { /* key not used */
165 if (!(semflg & IPC_CREAT))
166 err = -ENOENT;
167 else
168 err = newary(key, nsems, semflg);
169 } else if (semflg & IPC_CREAT && semflg & IPC_EXCL) {
170 err = -EEXIST;
171 } else {
172 sma = sem_lock(id);
173 if(sma==NULL)
174 BUG();
175 if (nsems > sma->sem_nsems)
176 err = -EINVAL;
177 else if (ipcperms(&sma->sem_perm, semflg))
178 err = -EACCES;
179 else
180 err = sem_buildid(id, sma->sem_perm.seq);
181 sem_unlock(id);
182 }
183
184 up(&sem_ids.sem);
185 return err;
186 }
187
188 /* doesn't acquire the sem_lock on error! */
sem_revalidate(int semid,struct sem_array * sma,int nsems,short flg)189 static int sem_revalidate(int semid, struct sem_array* sma, int nsems, short flg)
190 {
191 struct sem_array* smanew;
192
193 smanew = sem_lock(semid);
194 if(smanew==NULL)
195 return -EIDRM;
196 if(smanew != sma || sem_checkid(sma,semid) || sma->sem_nsems != nsems) {
197 sem_unlock(semid);
198 return -EIDRM;
199 }
200
201 if (ipcperms(&sma->sem_perm, flg)) {
202 sem_unlock(semid);
203 return -EACCES;
204 }
205 return 0;
206 }
207 /* Manage the doubly linked list sma->sem_pending as a FIFO:
208 * insert new queue elements at the tail sma->sem_pending_last.
209 */
append_to_queue(struct sem_array * sma,struct sem_queue * q)210 static inline void append_to_queue (struct sem_array * sma,
211 struct sem_queue * q)
212 {
213 *(q->prev = sma->sem_pending_last) = q;
214 *(sma->sem_pending_last = &q->next) = NULL;
215 }
216
prepend_to_queue(struct sem_array * sma,struct sem_queue * q)217 static inline void prepend_to_queue (struct sem_array * sma,
218 struct sem_queue * q)
219 {
220 q->next = sma->sem_pending;
221 *(q->prev = &sma->sem_pending) = q;
222 if (q->next)
223 q->next->prev = &q->next;
224 else /* sma->sem_pending_last == &sma->sem_pending */
225 sma->sem_pending_last = &q->next;
226 }
227
remove_from_queue(struct sem_array * sma,struct sem_queue * q)228 static inline void remove_from_queue (struct sem_array * sma,
229 struct sem_queue * q)
230 {
231 *(q->prev) = q->next;
232 if (q->next)
233 q->next->prev = q->prev;
234 else /* sma->sem_pending_last == &q->next */
235 sma->sem_pending_last = q->prev;
236 q->prev = NULL; /* mark as removed */
237 }
238
239 /*
240 * Determine whether a sequence of semaphore operations would succeed
241 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
242 */
243
try_atomic_semop(struct sem_array * sma,struct sembuf * sops,int nsops,struct sem_undo * un,int pid,int do_undo)244 static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
245 int nsops, struct sem_undo *un, int pid,
246 int do_undo)
247 {
248 int result, sem_op;
249 struct sembuf *sop;
250 struct sem * curr;
251
252 for (sop = sops; sop < sops + nsops; sop++) {
253 curr = sma->sem_base + sop->sem_num;
254 sem_op = sop->sem_op;
255 result = curr->semval;
256
257 if (!sem_op && result)
258 goto would_block;
259
260 result += sem_op;
261 if (result < 0)
262 goto would_block;
263 if (result > SEMVMX)
264 goto out_of_range;
265 if (sop->sem_flg & SEM_UNDO) {
266 int undo = un->semadj[sop->sem_num] - sem_op;
267 /*
268 * Exceeding the undo range is an error.
269 */
270 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
271 goto out_of_range;
272 }
273 curr->semval = result;
274 }
275
276 if (do_undo) {
277 result = 0;
278 goto undo;
279 }
280 sop--;
281 while (sop >= sops) {
282 sma->sem_base[sop->sem_num].sempid = pid;
283 if (sop->sem_flg & SEM_UNDO)
284 un->semadj[sop->sem_num] -= sop->sem_op;
285 sop--;
286 }
287 sma->sem_otime = CURRENT_TIME;
288 return 0;
289
290 out_of_range:
291 result = -ERANGE;
292 goto undo;
293
294 would_block:
295 if (sop->sem_flg & IPC_NOWAIT)
296 result = -EAGAIN;
297 else
298 result = 1;
299
300 undo:
301 sop--;
302 while (sop >= sops) {
303 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
304 sop--;
305 }
306
307 return result;
308 }
309
310 /* Go through the pending queue for the indicated semaphore
311 * looking for tasks that can be completed.
312 */
update_queue(struct sem_array * sma)313 static void update_queue (struct sem_array * sma)
314 {
315 int error;
316 struct sem_queue * q;
317
318 for (q = sma->sem_pending; q; q = q->next) {
319
320 if (q->status == 1)
321 continue; /* this one was woken up before */
322
323 error = try_atomic_semop(sma, q->sops, q->nsops,
324 q->undo, q->pid, q->alter);
325
326 /* Does q->sleeper still need to sleep? */
327 if (error <= 0) {
328 /* Found one, wake it up */
329 wake_up_process(q->sleeper);
330 if (error == 0 && q->alter) {
331 /* if q-> alter let it self try */
332 q->status = 1;
333 return;
334 }
335 q->status = error;
336 remove_from_queue(sma,q);
337 }
338 }
339 }
340
341 /* The following counts are associated to each semaphore:
342 * semncnt number of tasks waiting on semval being nonzero
343 * semzcnt number of tasks waiting on semval being zero
344 * This model assumes that a task waits on exactly one semaphore.
345 * Since semaphore operations are to be performed atomically, tasks actually
346 * wait on a whole sequence of semaphores simultaneously.
347 * The counts we return here are a rough approximation, but still
348 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
349 */
count_semncnt(struct sem_array * sma,ushort semnum)350 static int count_semncnt (struct sem_array * sma, ushort semnum)
351 {
352 int semncnt;
353 struct sem_queue * q;
354
355 semncnt = 0;
356 for (q = sma->sem_pending; q; q = q->next) {
357 struct sembuf * sops = q->sops;
358 int nsops = q->nsops;
359 int i;
360 for (i = 0; i < nsops; i++)
361 if (sops[i].sem_num == semnum
362 && (sops[i].sem_op < 0)
363 && !(sops[i].sem_flg & IPC_NOWAIT))
364 semncnt++;
365 }
366 return semncnt;
367 }
count_semzcnt(struct sem_array * sma,ushort semnum)368 static int count_semzcnt (struct sem_array * sma, ushort semnum)
369 {
370 int semzcnt;
371 struct sem_queue * q;
372
373 semzcnt = 0;
374 for (q = sma->sem_pending; q; q = q->next) {
375 struct sembuf * sops = q->sops;
376 int nsops = q->nsops;
377 int i;
378 for (i = 0; i < nsops; i++)
379 if (sops[i].sem_num == semnum
380 && (sops[i].sem_op == 0)
381 && !(sops[i].sem_flg & IPC_NOWAIT))
382 semzcnt++;
383 }
384 return semzcnt;
385 }
386
387 /* Free a semaphore set. */
freeary(int id)388 static void freeary (int id)
389 {
390 struct sem_array *sma;
391 struct sem_undo *un;
392 struct sem_queue *q;
393 int size;
394
395 sma = sem_rmid(id);
396
397 /* Invalidate the existing undo structures for this semaphore set.
398 * (They will be freed without any further action in sem_exit()
399 * or during the next semop.)
400 */
401 for (un = sma->undo; un; un = un->id_next)
402 un->semid = -1;
403
404 /* Wake up all pending processes and let them fail with EIDRM. */
405 for (q = sma->sem_pending; q; q = q->next) {
406 q->status = -EIDRM;
407 q->prev = NULL;
408 wake_up_process(q->sleeper); /* doesn't sleep */
409 }
410 sem_unlock(id);
411
412 used_sems -= sma->sem_nsems;
413 size = sizeof (*sma) + sma->sem_nsems * sizeof (struct sem);
414 ipc_free(sma, size);
415 }
416
copy_semid_to_user(void * buf,struct semid64_ds * in,int version)417 static unsigned long copy_semid_to_user(void *buf, struct semid64_ds *in, int version)
418 {
419 switch(version) {
420 case IPC_64:
421 return copy_to_user(buf, in, sizeof(*in));
422 case IPC_OLD:
423 {
424 struct semid_ds out;
425
426 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
427
428 out.sem_otime = in->sem_otime;
429 out.sem_ctime = in->sem_ctime;
430 out.sem_nsems = in->sem_nsems;
431
432 return copy_to_user(buf, &out, sizeof(out));
433 }
434 default:
435 return -EINVAL;
436 }
437 }
438
semctl_nolock(int semid,int semnum,int cmd,int version,union semun arg)439 static int semctl_nolock(int semid, int semnum, int cmd, int version, union semun arg)
440 {
441 int err = -EINVAL;
442
443 switch(cmd) {
444 case IPC_INFO:
445 case SEM_INFO:
446 {
447 struct seminfo seminfo;
448 int max_id;
449
450 memset(&seminfo,0,sizeof(seminfo));
451 seminfo.semmni = sc_semmni;
452 seminfo.semmns = sc_semmns;
453 seminfo.semmsl = sc_semmsl;
454 seminfo.semopm = sc_semopm;
455 seminfo.semvmx = SEMVMX;
456 seminfo.semmnu = SEMMNU;
457 seminfo.semmap = SEMMAP;
458 seminfo.semume = SEMUME;
459 down(&sem_ids.sem);
460 if (cmd == SEM_INFO) {
461 seminfo.semusz = sem_ids.in_use;
462 seminfo.semaem = used_sems;
463 } else {
464 seminfo.semusz = SEMUSZ;
465 seminfo.semaem = SEMAEM;
466 }
467 max_id = sem_ids.max_id;
468 up(&sem_ids.sem);
469 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
470 return -EFAULT;
471 return (max_id < 0) ? 0: max_id;
472 }
473 case SEM_STAT:
474 {
475 struct sem_array *sma;
476 struct semid64_ds tbuf;
477 int id;
478
479 if(semid >= sem_ids.size)
480 return -EINVAL;
481
482 memset(&tbuf,0,sizeof(tbuf));
483
484 sma = sem_lock(semid);
485 if(sma == NULL)
486 return -EINVAL;
487
488 err = -EACCES;
489 if (ipcperms (&sma->sem_perm, S_IRUGO))
490 goto out_unlock;
491 id = sem_buildid(semid, sma->sem_perm.seq);
492
493 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
494 tbuf.sem_otime = sma->sem_otime;
495 tbuf.sem_ctime = sma->sem_ctime;
496 tbuf.sem_nsems = sma->sem_nsems;
497 sem_unlock(semid);
498 if (copy_semid_to_user (arg.buf, &tbuf, version))
499 return -EFAULT;
500 return id;
501 }
502 default:
503 return -EINVAL;
504 }
505 return err;
506 out_unlock:
507 sem_unlock(semid);
508 return err;
509 }
510
semctl_main(int semid,int semnum,int cmd,int version,union semun arg)511 static int semctl_main(int semid, int semnum, int cmd, int version, union semun arg)
512 {
513 struct sem_array *sma;
514 struct sem* curr;
515 int err;
516 ushort fast_sem_io[SEMMSL_FAST];
517 ushort* sem_io = fast_sem_io;
518 int nsems;
519
520 sma = sem_lock(semid);
521 if(sma==NULL)
522 return -EINVAL;
523
524 nsems = sma->sem_nsems;
525
526 err=-EIDRM;
527 if (sem_checkid(sma,semid))
528 goto out_unlock;
529
530 err = -EACCES;
531 if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
532 goto out_unlock;
533
534 switch (cmd) {
535 case GETALL:
536 {
537 ushort *array = arg.array;
538 int i;
539
540 if(nsems > SEMMSL_FAST) {
541 sem_unlock(semid);
542 sem_io = ipc_alloc(sizeof(ushort)*nsems);
543 if(sem_io == NULL)
544 return -ENOMEM;
545 err = sem_revalidate(semid, sma, nsems, S_IRUGO);
546 if(err)
547 goto out_free;
548 }
549
550 for (i = 0; i < sma->sem_nsems; i++)
551 sem_io[i] = sma->sem_base[i].semval;
552 sem_unlock(semid);
553 err = 0;
554 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
555 err = -EFAULT;
556 goto out_free;
557 }
558 case SETALL:
559 {
560 int i;
561 struct sem_undo *un;
562
563 sem_unlock(semid);
564
565 if(nsems > SEMMSL_FAST) {
566 sem_io = ipc_alloc(sizeof(ushort)*nsems);
567 if(sem_io == NULL)
568 return -ENOMEM;
569 }
570
571 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
572 err = -EFAULT;
573 goto out_free;
574 }
575
576 for (i = 0; i < nsems; i++) {
577 if (sem_io[i] > SEMVMX) {
578 err = -ERANGE;
579 goto out_free;
580 }
581 }
582 err = sem_revalidate(semid, sma, nsems, S_IWUGO);
583 if(err)
584 goto out_free;
585
586 for (i = 0; i < nsems; i++)
587 sma->sem_base[i].semval = sem_io[i];
588 for (un = sma->undo; un; un = un->id_next)
589 for (i = 0; i < nsems; i++)
590 un->semadj[i] = 0;
591 sma->sem_ctime = CURRENT_TIME;
592 /* maybe some queued-up processes were waiting for this */
593 update_queue(sma);
594 err = 0;
595 goto out_unlock;
596 }
597 case IPC_STAT:
598 {
599 struct semid64_ds tbuf;
600 memset(&tbuf,0,sizeof(tbuf));
601 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
602 tbuf.sem_otime = sma->sem_otime;
603 tbuf.sem_ctime = sma->sem_ctime;
604 tbuf.sem_nsems = sma->sem_nsems;
605 sem_unlock(semid);
606 if (copy_semid_to_user (arg.buf, &tbuf, version))
607 return -EFAULT;
608 return 0;
609 }
610 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
611 }
612 err = -EINVAL;
613 if(semnum < 0 || semnum >= nsems)
614 goto out_unlock;
615
616 curr = &sma->sem_base[semnum];
617
618 switch (cmd) {
619 case GETVAL:
620 err = curr->semval;
621 goto out_unlock;
622 case GETPID:
623 err = curr->sempid;
624 goto out_unlock;
625 case GETNCNT:
626 err = count_semncnt(sma,semnum);
627 goto out_unlock;
628 case GETZCNT:
629 err = count_semzcnt(sma,semnum);
630 goto out_unlock;
631 case SETVAL:
632 {
633 int val = arg.val;
634 struct sem_undo *un;
635 err = -ERANGE;
636 if (val > SEMVMX || val < 0)
637 goto out_unlock;
638
639 for (un = sma->undo; un; un = un->id_next)
640 un->semadj[semnum] = 0;
641 curr->semval = val;
642 curr->sempid = current->pid;
643 sma->sem_ctime = CURRENT_TIME;
644 /* maybe some queued-up processes were waiting for this */
645 update_queue(sma);
646 err = 0;
647 goto out_unlock;
648 }
649 }
650 out_unlock:
651 sem_unlock(semid);
652 out_free:
653 if(sem_io != fast_sem_io)
654 ipc_free(sem_io, sizeof(ushort)*nsems);
655 return err;
656 }
657
658 struct sem_setbuf {
659 uid_t uid;
660 gid_t gid;
661 mode_t mode;
662 };
663
copy_semid_from_user(struct sem_setbuf * out,void * buf,int version)664 static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void *buf, int version)
665 {
666 switch(version) {
667 case IPC_64:
668 {
669 struct semid64_ds tbuf;
670
671 if(copy_from_user(&tbuf, buf, sizeof(tbuf)))
672 return -EFAULT;
673
674 out->uid = tbuf.sem_perm.uid;
675 out->gid = tbuf.sem_perm.gid;
676 out->mode = tbuf.sem_perm.mode;
677
678 return 0;
679 }
680 case IPC_OLD:
681 {
682 struct semid_ds tbuf_old;
683
684 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
685 return -EFAULT;
686
687 out->uid = tbuf_old.sem_perm.uid;
688 out->gid = tbuf_old.sem_perm.gid;
689 out->mode = tbuf_old.sem_perm.mode;
690
691 return 0;
692 }
693 default:
694 return -EINVAL;
695 }
696 }
697
semctl_down(int semid,int semnum,int cmd,int version,union semun arg)698 static int semctl_down(int semid, int semnum, int cmd, int version, union semun arg)
699 {
700 struct sem_array *sma;
701 int err;
702 struct sem_setbuf setbuf;
703 struct kern_ipc_perm *ipcp;
704
705 if(cmd == IPC_SET) {
706 if(copy_semid_from_user (&setbuf, arg.buf, version))
707 return -EFAULT;
708 }
709 sma = sem_lock(semid);
710 if(sma==NULL)
711 return -EINVAL;
712
713 if (sem_checkid(sma,semid)) {
714 err=-EIDRM;
715 goto out_unlock;
716 }
717 ipcp = &sma->sem_perm;
718
719 if (current->euid != ipcp->cuid &&
720 current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
721 err=-EPERM;
722 goto out_unlock;
723 }
724
725 switch(cmd){
726 case IPC_RMID:
727 freeary(semid);
728 err = 0;
729 break;
730 case IPC_SET:
731 ipcp->uid = setbuf.uid;
732 ipcp->gid = setbuf.gid;
733 ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
734 | (setbuf.mode & S_IRWXUGO);
735 sma->sem_ctime = CURRENT_TIME;
736 sem_unlock(semid);
737 err = 0;
738 break;
739 default:
740 sem_unlock(semid);
741 err = -EINVAL;
742 break;
743 }
744 return err;
745
746 out_unlock:
747 sem_unlock(semid);
748 return err;
749 }
750
sys_semctl(int semid,int semnum,int cmd,union semun arg)751 asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
752 {
753 int err = -EINVAL;
754 int version;
755
756 if (semid < 0)
757 return -EINVAL;
758
759 version = ipc_parse_version(&cmd);
760
761 switch(cmd) {
762 case IPC_INFO:
763 case SEM_INFO:
764 case SEM_STAT:
765 err = semctl_nolock(semid,semnum,cmd,version,arg);
766 return err;
767 case GETALL:
768 case GETVAL:
769 case GETPID:
770 case GETNCNT:
771 case GETZCNT:
772 case IPC_STAT:
773 case SETVAL:
774 case SETALL:
775 err = semctl_main(semid,semnum,cmd,version,arg);
776 return err;
777 case IPC_RMID:
778 case IPC_SET:
779 down(&sem_ids.sem);
780 err = semctl_down(semid,semnum,cmd,version,arg);
781 up(&sem_ids.sem);
782 return err;
783 default:
784 return -EINVAL;
785 }
786 }
787
freeundos(struct sem_array * sma,struct sem_undo * un)788 static struct sem_undo* freeundos(struct sem_array *sma, struct sem_undo* un)
789 {
790 struct sem_undo* u;
791 struct sem_undo** up;
792
793 for(up = ¤t->semundo;(u=*up);up=&u->proc_next) {
794 if(un==u) {
795 un=u->proc_next;
796 *up=un;
797 kfree(u);
798 return un;
799 }
800 }
801 printk ("freeundos undo list error id=%d\n", un->semid);
802 return un->proc_next;
803 }
804
805 /* returns without sem_lock on error! */
alloc_undo(struct sem_array * sma,struct sem_undo ** unp,int semid,int alter)806 static int alloc_undo(struct sem_array *sma, struct sem_undo** unp, int semid, int alter)
807 {
808 int size, nsems, error;
809 struct sem_undo *un;
810
811 nsems = sma->sem_nsems;
812 size = sizeof(struct sem_undo) + sizeof(short)*nsems;
813 sem_unlock(semid);
814
815 un = (struct sem_undo *) kmalloc(size, GFP_KERNEL);
816 if (!un)
817 return -ENOMEM;
818
819 memset(un, 0, size);
820 error = sem_revalidate(semid, sma, nsems, alter ? S_IWUGO : S_IRUGO);
821 if(error) {
822 kfree(un);
823 return error;
824 }
825
826 un->semadj = (short *) &un[1];
827 un->semid = semid;
828 un->proc_next = current->semundo;
829 current->semundo = un;
830 un->id_next = sma->undo;
831 sma->undo = un;
832 *unp = un;
833 return 0;
834 }
835
sys_semop(int semid,struct sembuf * tsops,unsigned nsops)836 asmlinkage long sys_semop (int semid, struct sembuf *tsops, unsigned nsops)
837 {
838 return sys_semtimedop(semid, tsops, nsops, NULL);
839 }
840
sys_semtimedop(int semid,struct sembuf * tsops,unsigned nsops,const struct timespec * timeout)841 asmlinkage long sys_semtimedop (int semid, struct sembuf *tsops,
842 unsigned nsops, const struct timespec *timeout)
843 {
844 int error = -EINVAL;
845 struct sem_array *sma;
846 struct sembuf fast_sops[SEMOPM_FAST];
847 struct sembuf* sops = fast_sops, *sop;
848 struct sem_undo *un;
849 int undos = 0, decrease = 0, alter = 0;
850 struct sem_queue queue;
851 unsigned long jiffies_left = 0;
852
853 if (nsops < 1 || semid < 0)
854 return -EINVAL;
855 if (nsops > sc_semopm)
856 return -E2BIG;
857 if(nsops > SEMOPM_FAST) {
858 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
859 if(sops==NULL)
860 return -ENOMEM;
861 }
862 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
863 error=-EFAULT;
864 goto out_free;
865 }
866 if (timeout) {
867 struct timespec _timeout;
868 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
869 error = -EFAULT;
870 goto out_free;
871 }
872 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
873 _timeout.tv_nsec >= 1000000000L) {
874 error = -EINVAL;
875 goto out_free;
876 }
877 jiffies_left = timespec_to_jiffies(&_timeout);
878 }
879 sma = sem_lock(semid);
880 error=-EINVAL;
881 if(sma==NULL)
882 goto out_free;
883 error = -EIDRM;
884 if (sem_checkid(sma,semid))
885 goto out_unlock_free;
886 error = -EFBIG;
887 for (sop = sops; sop < sops + nsops; sop++) {
888 if (sop->sem_num >= sma->sem_nsems)
889 goto out_unlock_free;
890 if (sop->sem_flg & SEM_UNDO)
891 undos++;
892 if (sop->sem_op < 0)
893 decrease = 1;
894 if (sop->sem_op > 0)
895 alter = 1;
896 }
897 alter |= decrease;
898
899 error = -EACCES;
900 if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
901 goto out_unlock_free;
902 if (undos) {
903 /* Make sure we have an undo structure
904 * for this process and this semaphore set.
905 */
906 un=current->semundo;
907 while(un != NULL) {
908 if(un->semid==semid)
909 break;
910 if(un->semid==-1)
911 un=freeundos(sma,un);
912 else
913 un=un->proc_next;
914 }
915 if (!un) {
916 error = alloc_undo(sma,&un,semid,alter);
917 if(error)
918 goto out_free;
919 }
920 } else
921 un = NULL;
922
923 error = try_atomic_semop (sma, sops, nsops, un, current->pid, 0);
924 if (error <= 0)
925 goto update;
926
927 /* We need to sleep on this operation, so we put the current
928 * task into the pending queue and go to sleep.
929 */
930
931 queue.sma = sma;
932 queue.sops = sops;
933 queue.nsops = nsops;
934 queue.undo = un;
935 queue.pid = current->pid;
936 queue.alter = decrease;
937 queue.id = semid;
938 if (alter)
939 append_to_queue(sma ,&queue);
940 else
941 prepend_to_queue(sma ,&queue);
942 current->semsleeping = &queue;
943
944 for (;;) {
945 struct sem_array* tmp;
946 queue.status = -EINTR;
947 queue.sleeper = current;
948 current->state = TASK_INTERRUPTIBLE;
949 sem_unlock(semid);
950
951 if (timeout)
952 jiffies_left = schedule_timeout(jiffies_left);
953 else
954 schedule();
955
956 tmp = sem_lock(semid);
957 if(tmp==NULL) {
958 if(queue.prev != NULL)
959 BUG();
960 current->semsleeping = NULL;
961 error = -EIDRM;
962 goto out_free;
963 }
964 /*
965 * If queue.status == 1 we where woken up and
966 * have to retry else we simply return.
967 * If an interrupt occurred we have to clean up the
968 * queue
969 *
970 */
971 if (queue.status == 1)
972 {
973 error = try_atomic_semop (sma, sops, nsops, un,
974 current->pid,0);
975 if (error <= 0)
976 break;
977 } else {
978 error = queue.status;
979 if (error == -EINTR && timeout && jiffies_left == 0)
980 error = -EAGAIN;
981 if (queue.prev) /* got Interrupt */
982 break;
983 /* Everything done by update_queue */
984 current->semsleeping = NULL;
985 goto out_unlock_free;
986 }
987 }
988 current->semsleeping = NULL;
989 remove_from_queue(sma,&queue);
990 update:
991 if (alter)
992 update_queue (sma);
993 out_unlock_free:
994 sem_unlock(semid);
995 out_free:
996 if(sops != fast_sops)
997 kfree(sops);
998 return error;
999 }
1000
1001 /*
1002 * add semadj values to semaphores, free undo structures.
1003 * undo structures are not freed when semaphore arrays are destroyed
1004 * so some of them may be out of date.
1005 * IMPLEMENTATION NOTE: There is some confusion over whether the
1006 * set of adjustments that needs to be done should be done in an atomic
1007 * manner or not. That is, if we are attempting to decrement the semval
1008 * should we queue up and wait until we can do so legally?
1009 * The original implementation attempted to do this (queue and wait).
1010 * The current implementation does not do so. The POSIX standard
1011 * and SVID should be consulted to determine what behavior is mandated.
1012 */
sem_exit(void)1013 void sem_exit (void)
1014 {
1015 struct sem_queue *q;
1016 struct sem_undo *u, *un = NULL, **up, **unp;
1017 struct sem_array *sma;
1018 int nsems, i;
1019
1020 /* If the current process was sleeping for a semaphore,
1021 * remove it from the queue.
1022 */
1023 if ((q = current->semsleeping)) {
1024 int semid = q->id;
1025 sma = sem_lock(semid);
1026 current->semsleeping = NULL;
1027
1028 if (q->prev) {
1029 if(sma==NULL)
1030 BUG();
1031 remove_from_queue(q->sma,q);
1032 }
1033 if(sma!=NULL)
1034 sem_unlock(semid);
1035 }
1036
1037 for (up = ¤t->semundo; (u = *up); *up = u->proc_next, kfree(u)) {
1038 int semid = u->semid;
1039 if(semid == -1)
1040 continue;
1041 sma = sem_lock(semid);
1042 if (sma == NULL)
1043 continue;
1044
1045 if (u->semid == -1)
1046 goto next_entry;
1047
1048 if (sem_checkid(sma,u->semid))
1049 goto next_entry;
1050
1051 /* remove u from the sma->undo list */
1052 for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
1053 if (u == un)
1054 goto found;
1055 }
1056 printk ("sem_exit undo list error id=%d\n", u->semid);
1057 goto next_entry;
1058 found:
1059 *unp = un->id_next;
1060 /* perform adjustments registered in u */
1061 nsems = sma->sem_nsems;
1062 for (i = 0; i < nsems; i++) {
1063 struct sem * sem = &sma->sem_base[i];
1064 sem->semval += u->semadj[i];
1065 if (sem->semval < 0)
1066 sem->semval = 0; /* shouldn't happen */
1067 sem->sempid = current->pid;
1068 }
1069 sma->sem_otime = CURRENT_TIME;
1070 /* maybe some queued-up processes were waiting for this */
1071 update_queue(sma);
1072 next_entry:
1073 sem_unlock(semid);
1074 }
1075 current->semundo = NULL;
1076 }
1077
1078 #ifdef CONFIG_PROC_FS
sysvipc_sem_read_proc(char * buffer,char ** start,off_t offset,int length,int * eof,void * data)1079 static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
1080 {
1081 off_t pos = 0;
1082 off_t begin = 0;
1083 int i, len = 0;
1084
1085 len += sprintf(buffer, " key semid perms nsems uid gid cuid cgid otime ctime\n");
1086 down(&sem_ids.sem);
1087
1088 for(i = 0; i <= sem_ids.max_id; i++) {
1089 struct sem_array *sma;
1090 sma = sem_lock(i);
1091 if(sma) {
1092 len += sprintf(buffer + len, "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
1093 sma->sem_perm.key,
1094 sem_buildid(i,sma->sem_perm.seq),
1095 sma->sem_perm.mode,
1096 sma->sem_nsems,
1097 sma->sem_perm.uid,
1098 sma->sem_perm.gid,
1099 sma->sem_perm.cuid,
1100 sma->sem_perm.cgid,
1101 sma->sem_otime,
1102 sma->sem_ctime);
1103 sem_unlock(i);
1104
1105 pos += len;
1106 if(pos < offset) {
1107 len = 0;
1108 begin = pos;
1109 }
1110 if(pos > offset + length)
1111 goto done;
1112 }
1113 }
1114 *eof = 1;
1115 done:
1116 up(&sem_ids.sem);
1117 *start = buffer + (offset - begin);
1118 len -= (offset - begin);
1119 if(len > length)
1120 len = length;
1121 if(len < 0)
1122 len = 0;
1123 return len;
1124 }
1125 #endif
1126