1 /* $FreeBSD: src/sys/kern/sysv_sem.c,v 1.69 2004/03/17 09:37:13 cperciva Exp $ */
2
3 /*
4 * Implementation of SVID semaphores
5 *
6 * Author: Daniel Boulet
7 *
8 * This software is provided ``AS IS'' without any warranties of any kind.
9 */
10
11 #include "opt_sysvipc.h"
12
13 #include <sys/param.h>
14 #include <sys/systm.h>
15 #include <sys/sysmsg.h>
16 #include <sys/kernel.h>
17 #include <sys/proc.h>
18 #include <sys/sem.h>
19 #include <sys/sysent.h>
20 #include <sys/sysctl.h>
21 #include <sys/malloc.h>
22 #include <sys/jail.h>
23 #include <sys/thread.h>
24
25 static MALLOC_DEFINE(M_SEM, "sem", "SVID compatible semaphores");
26
27 static void seminit (void *);
28
29 static struct sem_undo *semu_alloc (struct proc *p);
30 static int semundo_adjust (struct proc *p, int semid, int semnum, int adjval);
31 static void semundo_clear (int semid, int semnum);
32
33 static struct lwkt_token semu_token = LWKT_TOKEN_INITIALIZER(semu_token);
34 static int semtot = 0;
35 static struct semid_pool *sema; /* semaphore id pool */
36 static TAILQ_HEAD(, sem_undo) semu_list = TAILQ_HEAD_INITIALIZER(semu_list);
37 static struct lock sema_lk;
38
39 struct sem {
40 u_short semval; /* semaphore value */
41 pid_t sempid; /* pid of last operation */
42 u_short semncnt; /* # awaiting semval > cval */
43 u_short semzcnt; /* # awaiting semval = 0 */
44 };
45
46 /*
47 * Undo structure (one per process)
48 */
49 struct sem_undo {
50 TAILQ_ENTRY(sem_undo) un_entry; /* linked list for semundo_clear() */
51 struct proc *un_proc; /* owner of this structure */
52 int un_refs; /* prevent unlink/kfree */
53 short un_cnt; /* # of active entries */
54 short un_unused;
55 struct undo {
56 short un_adjval; /* adjust on exit values */
57 short un_num; /* semaphore # */
58 int un_id; /* semid */
59 } un_ent[1]; /* undo entries */
60 };
61
62 /*
63 * Configuration parameters
64 */
65 #ifndef SEMMNI
66 #define SEMMNI 1024 /* # of semaphore identifiers */
67 #endif
68 #ifndef SEMMNS
69 #define SEMMNS 32767 /* # of semaphores in system */
70 #endif
71 #ifndef SEMUME
72 #define SEMUME 25 /* max # of undo entries per process */
73 #endif
74 #ifndef SEMMNU
75 #define SEMMNU 1024 /* # of undo structures in system */
76 /* NO LONGER USED */
77 #endif
78
79 /* shouldn't need tuning */
80 #ifndef SEMMAP
81 #define SEMMAP 128 /* # of entries in semaphore map */
82 #endif
83 #ifndef SEMMSL
84 #define SEMMSL SEMMNS /* max # of semaphores per id */
85 #endif
86 #ifndef SEMOPM
87 #define SEMOPM 100 /* max # of operations per semop call */
88 #endif
89
90 #define SEMVMX 32767 /* semaphore maximum value */
91 #define SEMAEM 16384 /* adjust on exit max value */
92
93 /*
94 * Due to the way semaphore memory is allocated, we have to ensure that
95 * SEMUSZ is properly aligned.
96 */
97
98 #define SEM_ALIGN(bytes) roundup2(bytes, sizeof(long))
99
100 /* actual size of an undo structure */
101 #define SEMUSZ(nent) SEM_ALIGN(offsetof(struct sem_undo, un_ent[nent]))
102
103 /*
104 * semaphore info struct
105 */
106 struct seminfo seminfo = {
107 SEMMAP, /* # of entries in semaphore map */
108 SEMMNI, /* # of semaphore identifiers */
109 SEMMNS, /* # of semaphores in system */
110 SEMMNU, /* # of undo structures in system */
111 SEMMSL, /* max # of semaphores per id */
112 SEMOPM, /* max # of operations per semop call */
113 SEMUME, /* max # of undo entries per process */
114 SEMUSZ(SEMUME), /* size in bytes of undo structure */
115 SEMVMX, /* semaphore maximum value */
116 SEMAEM /* adjust on exit max value */
117 };
118
119 TUNABLE_INT("kern.ipc.semmap", &seminfo.semmap);
120 TUNABLE_INT("kern.ipc.semmni", &seminfo.semmni);
121 TUNABLE_INT("kern.ipc.semmns", &seminfo.semmns);
122 TUNABLE_INT("kern.ipc.semmnu", &seminfo.semmnu);
123 TUNABLE_INT("kern.ipc.semmsl", &seminfo.semmsl);
124 TUNABLE_INT("kern.ipc.semopm", &seminfo.semopm);
125 TUNABLE_INT("kern.ipc.semume", &seminfo.semume);
126 TUNABLE_INT("kern.ipc.semusz", &seminfo.semusz);
127 TUNABLE_INT("kern.ipc.semvmx", &seminfo.semvmx);
128 TUNABLE_INT("kern.ipc.semaem", &seminfo.semaem);
129
130 SYSCTL_INT(_kern_ipc, OID_AUTO, semmap, CTLFLAG_RW, &seminfo.semmap, 0,
131 "Number of entries in semaphore map");
132 SYSCTL_INT(_kern_ipc, OID_AUTO, semmni, CTLFLAG_RD, &seminfo.semmni, 0,
133 "Number of semaphore identifiers");
134 SYSCTL_INT(_kern_ipc, OID_AUTO, semmns, CTLFLAG_RD, &seminfo.semmns, 0,
135 "Total number of semaphores");
136 SYSCTL_INT(_kern_ipc, OID_AUTO, semmnu, CTLFLAG_RD, &seminfo.semmnu, 0,
137 "Total number of undo structures");
138 SYSCTL_INT(_kern_ipc, OID_AUTO, semmsl, CTLFLAG_RW, &seminfo.semmsl, 0,
139 "Max number of semaphores per id");
140 SYSCTL_INT(_kern_ipc, OID_AUTO, semopm, CTLFLAG_RD, &seminfo.semopm, 0,
141 "Max number of operations per semop call");
142 SYSCTL_INT(_kern_ipc, OID_AUTO, semume, CTLFLAG_RD, &seminfo.semume, 0,
143 "Max number of undo entries per process");
144 SYSCTL_INT(_kern_ipc, OID_AUTO, semusz, CTLFLAG_RD, &seminfo.semusz, 0,
145 "Size in bytes of undo structure");
146 SYSCTL_INT(_kern_ipc, OID_AUTO, semvmx, CTLFLAG_RW, &seminfo.semvmx, 0,
147 "Semaphore maximum value");
148 SYSCTL_INT(_kern_ipc, OID_AUTO, semaem, CTLFLAG_RW, &seminfo.semaem, 0,
149 "Adjust on exit max value");
150
151 #if 0
152 RO seminfo.semmap /* SEMMAP unused */
153 RO seminfo.semmni
154 RO seminfo.semmns
155 RO seminfo.semmnu /* undo entries per system */
156 RW seminfo.semmsl
157 RO seminfo.semopm /* SEMOPM unused */
158 RO seminfo.semume
159 RO seminfo.semusz /* param - derived from SEMUME for per-proc sizeof */
160 RO seminfo.semvmx /* SEMVMX unused - user param */
161 RO seminfo.semaem /* SEMAEM unused - user param */
162 #endif
163
164 static void
seminit(void * dummy)165 seminit(void *dummy)
166 {
167 int i;
168
169 sema = kmalloc(sizeof(struct semid_pool) * seminfo.semmni,
170 M_SEM, M_WAITOK | M_ZERO);
171
172 lockinit(&sema_lk, "semglb", 0, 0);
173 for (i = 0; i < seminfo.semmni; i++) {
174 struct semid_pool *semaptr = &sema[i];
175
176 lockinit(&semaptr->lk, "semary", 0, 0);
177 semaptr->ds.sem_base = NULL;
178 semaptr->ds.sem_perm.mode = 0;
179 }
180 }
181 SYSINIT(sysv_sem, SI_SUB_SYSV_SEM, SI_ORDER_FIRST, seminit, NULL);
182
183 /*
184 * Allocate a new sem_undo structure for a process
185 * (returns ptr to structure or NULL if no more room)
186 */
187 static struct sem_undo *
semu_alloc(struct proc * p)188 semu_alloc(struct proc *p)
189 {
190 struct sem_undo *semu;
191
192 /*
193 * Allocate the semu structure and associate it with the process,
194 * as necessary.
195 */
196 while ((semu = p->p_sem_undo) == NULL) {
197 semu = kmalloc(SEMUSZ(seminfo.semume), M_SEM,
198 M_WAITOK | M_ZERO);
199 lwkt_gettoken(&semu_token);
200 lwkt_gettoken(&p->p_token);
201 if (p->p_sem_undo == NULL) {
202 p->p_sem_undo = semu;
203 p->p_flags |= P_SYSVSEM;
204 semu->un_proc = p;
205 TAILQ_INSERT_TAIL(&semu_list, semu, un_entry);
206 } else {
207 kfree(semu, M_SEM);
208 }
209 lwkt_reltoken(&p->p_token);
210 lwkt_reltoken(&semu_token);
211 }
212 return(semu);
213 }
214
215 /*
216 * Adjust a particular entry for a particular proc
217 */
218 static int
semundo_adjust(struct proc * p,int semid,int semnum,int adjval)219 semundo_adjust(struct proc *p, int semid, int semnum, int adjval)
220 {
221 struct sem_undo *suptr;
222 struct undo *sunptr;
223 int i;
224 int error = 0;
225
226 /*
227 * Look for and remember the sem_undo if the caller doesn't
228 * provide it.
229 */
230 suptr = semu_alloc(p);
231 lwkt_gettoken(&p->p_token);
232
233 /*
234 * Look for the requested entry and adjust it (delete if adjval becomes
235 * 0).
236 */
237 sunptr = &suptr->un_ent[0];
238 for (i = 0; i < suptr->un_cnt; i++, sunptr++) {
239 if (sunptr->un_id != semid || sunptr->un_num != semnum)
240 continue;
241 if (adjval == 0)
242 sunptr->un_adjval = 0;
243 else
244 sunptr->un_adjval += adjval;
245 if (sunptr->un_adjval == 0) {
246 suptr->un_cnt--;
247 if (i < suptr->un_cnt)
248 suptr->un_ent[i] = suptr->un_ent[suptr->un_cnt];
249 }
250 goto done;
251 }
252
253 /* Didn't find the right entry - create it */
254 if (adjval == 0)
255 goto done;
256 if (suptr->un_cnt != seminfo.semume) {
257 sunptr = &suptr->un_ent[suptr->un_cnt];
258 suptr->un_cnt++;
259 sunptr->un_adjval = adjval;
260 sunptr->un_id = semid;
261 sunptr->un_num = semnum;
262 } else {
263 error = EINVAL;
264 }
265 done:
266 lwkt_reltoken(&p->p_token);
267
268 return (error);
269 }
270
271 /*
272 * This is rather expensive
273 */
274 static void
semundo_clear(int semid,int semnum)275 semundo_clear(int semid, int semnum)
276 {
277 struct proc *p;
278 struct sem_undo *suptr;
279 struct sem_undo *sunext;
280 struct undo *sunptr;
281 int i;
282
283 lwkt_gettoken(&semu_token);
284 sunext = TAILQ_FIRST(&semu_list);
285 while ((suptr = sunext) != NULL) {
286 if ((p = suptr->un_proc) == NULL) {
287 sunext = TAILQ_NEXT(suptr, un_entry);
288 continue;
289 }
290 ++suptr->un_refs;
291 PHOLD(p);
292 lwkt_gettoken(&p->p_token);
293
294 /*
295 * Check for semexit() race
296 */
297 if (p->p_sem_undo != suptr)
298 goto skip;
299
300 sunptr = &suptr->un_ent[0];
301 i = 0;
302
303 while (i < suptr->un_cnt) {
304 if (sunptr->un_id == semid) {
305 if (semnum == -1 || sunptr->un_num == semnum) {
306 suptr->un_cnt--;
307 if (i < suptr->un_cnt) {
308 suptr->un_ent[i] =
309 suptr->un_ent[suptr->un_cnt];
310 /*
311 * do not increment i
312 * or sunptr after copydown.
313 */
314 continue;
315 }
316 }
317 if (semnum != -1)
318 break;
319 }
320 ++i;
321 ++sunptr;
322 }
323
324 skip:
325 lwkt_reltoken(&p->p_token);
326 PRELE(p);
327
328 /*
329 * Handle deletion and semexit races
330 */
331 sunext = TAILQ_NEXT(suptr, un_entry);
332 if (--suptr->un_refs == 0 && suptr->un_proc == NULL) {
333 KKASSERT(suptr->un_cnt == 0);
334 TAILQ_REMOVE(&semu_list, suptr, un_entry);
335 kfree(suptr, M_SEM);
336 }
337 }
338 lwkt_reltoken(&semu_token);
339 }
340
341 /*
342 * Note that the user-mode half of this passes a union, not a pointer
343 *
344 * MPALMOSTSAFE
345 */
346 int
sys___semctl(struct sysmsg * sysmsg,const struct __semctl_args * uap)347 sys___semctl(struct sysmsg *sysmsg, const struct __semctl_args *uap)
348 {
349 struct thread *td = curthread;
350 struct prison *pr = td->td_proc->p_ucred->cr_prison;
351 int semid = uap->semid;
352 int semnum = uap->semnum;
353 int cmd = uap->cmd;
354 union semun *arg = uap->arg;
355 union semun real_arg;
356 struct ucred *cred = td->td_ucred;
357 int i, rval, eval;
358 struct semid_ds sbuf;
359 struct semid_pool *semaptr;
360 struct sem *semptr;
361
362 #ifdef SEM_DEBUG
363 kprintf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg);
364 #endif
365
366 if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
367 return (ENOSYS);
368
369 semid = IPCID_TO_IX(semid);
370 if (semid < 0 || semid >= seminfo.semmni) {
371 return(EINVAL);
372 }
373 semaptr = &sema[semid];
374 lockmgr(&semaptr->lk, LK_EXCLUSIVE);
375
376 if ((semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0 ||
377 semaptr->ds.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
378 lockmgr(&semaptr->lk, LK_RELEASE);
379 return(EINVAL);
380 }
381
382 eval = 0;
383 rval = 0;
384
385 switch (cmd) {
386 case IPC_RMID:
387 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_M);
388 if (eval != 0)
389 break;
390 semaptr->ds.sem_perm.cuid = cred->cr_uid;
391 semaptr->ds.sem_perm.uid = cred->cr_uid;
392
393 /*
394 * NOTE: Nobody will be waiting on the semaphores since
395 * we have an exclusive lock on semaptr->lk).
396 */
397 lockmgr(&sema_lk, LK_EXCLUSIVE);
398 semtot -= semaptr->ds.sem_nsems;
399 kfree(semaptr->ds.sem_base, M_SEM);
400 semaptr->ds.sem_base = NULL;
401 semaptr->ds.sem_perm.mode = 0; /* clears SEM_ALLOC */
402 lockmgr(&sema_lk, LK_RELEASE);
403
404 semundo_clear(semid, -1);
405 break;
406
407 case IPC_SET:
408 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_M);
409 if (eval)
410 break;
411 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
412 break;
413 if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf,
414 sizeof(sbuf))) != 0) {
415 break;
416 }
417 semaptr->ds.sem_perm.uid = sbuf.sem_perm.uid;
418 semaptr->ds.sem_perm.gid = sbuf.sem_perm.gid;
419 semaptr->ds.sem_perm.mode =
420 (semaptr->ds.sem_perm.mode & ~0777) |
421 (sbuf.sem_perm.mode & 0777);
422 semaptr->ds.sem_ctime = time_second;
423 break;
424
425 case IPC_STAT:
426 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
427 if (eval)
428 break;
429 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
430 break;
431 eval = copyout(&semaptr->ds, real_arg.buf,
432 sizeof(struct semid_ds));
433 break;
434 case SEM_STAT:
435 /*
436 * For this command we assume semid is an array index
437 * rather than an IPC id. However, the conversion is
438 * just a mask so just validate that the passed-in semid
439 * matches the masked semid.
440 */
441 if (uap->semid != semid) {
442 eval = EINVAL;
443 break;
444 }
445 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
446 if (eval)
447 break;
448 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
449 break;
450 eval = copyout(&semaptr->ds, real_arg.buf,
451 sizeof(struct semid_ds));
452 rval = IXSEQ_TO_IPCID(semid, semaptr->ds.sem_perm);
453 break;
454
455 case GETNCNT:
456 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
457 if (eval)
458 break;
459 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) {
460 eval = EINVAL;
461 break;
462 }
463 rval = semaptr->ds.sem_base[semnum].semncnt;
464 break;
465
466 case GETPID:
467 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
468 if (eval)
469 break;
470 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) {
471 eval = EINVAL;
472 break;
473 }
474 rval = semaptr->ds.sem_base[semnum].sempid;
475 break;
476
477 case GETVAL:
478 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
479 if (eval)
480 break;
481 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) {
482 eval = EINVAL;
483 break;
484 }
485 rval = semaptr->ds.sem_base[semnum].semval;
486 break;
487
488 case GETALL:
489 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
490 if (eval)
491 break;
492 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
493 break;
494 for (i = 0; i < semaptr->ds.sem_nsems; i++) {
495 eval = copyout(&semaptr->ds.sem_base[i].semval,
496 &real_arg.array[i],
497 sizeof(real_arg.array[0]));
498 if (eval)
499 break;
500 }
501 break;
502
503 case GETZCNT:
504 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R);
505 if (eval)
506 break;
507 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) {
508 eval = EINVAL;
509 break;
510 }
511 rval = semaptr->ds.sem_base[semnum].semzcnt;
512 break;
513
514 case SETVAL:
515 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_W);
516 if (eval)
517 break;
518 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) {
519 eval = EINVAL;
520 break;
521 }
522 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
523 break;
524
525 /*
526 * Because we hold semaptr->lk exclusively we can safely
527 * modify any semptr content without acquiring its token.
528 */
529 semptr = &semaptr->ds.sem_base[semnum];
530 semptr->semval = real_arg.val;
531 semundo_clear(semid, semnum);
532 if (semptr->semzcnt || semptr->semncnt)
533 wakeup(semptr);
534 break;
535
536 case SETALL:
537 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_W);
538 if (eval)
539 break;
540 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
541 break;
542 /*
543 * Because we hold semaptr->lk exclusively we can safely
544 * modify any semptr content without acquiring its token.
545 */
546 for (i = 0; i < semaptr->ds.sem_nsems; i++) {
547 semptr = &semaptr->ds.sem_base[i];
548 eval = copyin(&real_arg.array[i],
549 (caddr_t)&semptr->semval,
550 sizeof(real_arg.array[0]));
551 if (semptr->semzcnt || semptr->semncnt)
552 wakeup(semptr);
553 if (eval != 0)
554 break;
555 }
556 semundo_clear(semid, -1);
557 break;
558
559 default:
560 eval = EINVAL;
561 break;
562 }
563 lockmgr(&semaptr->lk, LK_RELEASE);
564
565 if (eval == 0)
566 sysmsg->sysmsg_result = rval;
567 return(eval);
568 }
569
570 /*
571 * MPALMOSTSAFE
572 */
573 int
sys_semget(struct sysmsg * sysmsg,const struct semget_args * uap)574 sys_semget(struct sysmsg *sysmsg, const struct semget_args *uap)
575 {
576 struct thread *td = curthread;
577 struct prison *pr = td->td_proc->p_ucred->cr_prison;
578 int semid, eval;
579 int key = uap->key;
580 int nsems = uap->nsems;
581 int semflg = uap->semflg;
582 struct ucred *cred = td->td_ucred;
583
584 #ifdef SEM_DEBUG
585 kprintf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg);
586 #endif
587
588 if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
589 return (ENOSYS);
590
591 eval = 0;
592
593 if (key != IPC_PRIVATE) {
594 for (semid = 0; semid < seminfo.semmni; semid++) {
595 if ((sema[semid].ds.sem_perm.mode & SEM_ALLOC) == 0 ||
596 sema[semid].ds.sem_perm.key != key) {
597 continue;
598 }
599 lockmgr(&sema[semid].lk, LK_EXCLUSIVE);
600 if ((sema[semid].ds.sem_perm.mode & SEM_ALLOC) == 0 ||
601 sema[semid].ds.sem_perm.key != key) {
602 lockmgr(&sema[semid].lk, LK_RELEASE);
603 continue;
604 }
605 break;
606 }
607 if (semid < seminfo.semmni) {
608 /* sema[semid].lk still locked from above */
609 #ifdef SEM_DEBUG
610 kprintf("found public key\n");
611 #endif
612 if ((eval = ipcperm(td->td_proc,
613 &sema[semid].ds.sem_perm,
614 semflg & 0700))) {
615 lockmgr(&sema[semid].lk, LK_RELEASE);
616 goto done;
617 }
618 if (nsems > 0 && sema[semid].ds.sem_nsems < nsems) {
619 #ifdef SEM_DEBUG
620 kprintf("too small\n");
621 #endif
622 eval = EINVAL;
623 lockmgr(&sema[semid].lk, LK_RELEASE);
624 goto done;
625 }
626 if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
627 #ifdef SEM_DEBUG
628 kprintf("not exclusive\n");
629 #endif
630 eval = EEXIST;
631 lockmgr(&sema[semid].lk, LK_RELEASE);
632 goto done;
633 }
634
635 /*
636 * Return this one.
637 */
638 lockmgr(&sema[semid].lk, LK_RELEASE);
639 goto done;
640 }
641 }
642
643 #ifdef SEM_DEBUG
644 kprintf("need to allocate the semid_ds\n");
645 #endif
646 if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
647 if (nsems <= 0 || nsems > seminfo.semmsl) {
648 #ifdef SEM_DEBUG
649 kprintf("nsems out of range (0<%d<=%d)\n",
650 nsems, seminfo.semmsl);
651 #endif
652 eval = EINVAL;
653 goto done;
654 }
655
656 /*
657 * SEM_ALLOC flag cannot be set unless sema_lk is locked.
658 * semtot field also protected by sema_lk.
659 */
660 lockmgr(&sema_lk, LK_EXCLUSIVE);
661 if (nsems > seminfo.semmns - semtot) {
662 #ifdef SEM_DEBUG
663 kprintf("not enough semaphores left "
664 "(need %d, got %d)\n",
665 nsems, seminfo.semmns - semtot);
666 #endif
667 eval = ENOSPC;
668 lockmgr(&sema_lk, LK_RELEASE);
669 goto done;
670 }
671 for (semid = 0; semid < seminfo.semmni; semid++) {
672 if ((sema[semid].ds.sem_perm.mode & SEM_ALLOC) == 0)
673 break;
674 }
675 if (semid == seminfo.semmni) {
676 #ifdef SEM_DEBUG
677 kprintf("no more semid_ds's available\n");
678 #endif
679 eval = ENOSPC;
680 lockmgr(&sema_lk, LK_RELEASE);
681 goto done;
682 }
683 #ifdef SEM_DEBUG
684 kprintf("semid %d is available\n", semid);
685 #endif
686 lockmgr(&sema[semid].lk, LK_EXCLUSIVE);
687 sema[semid].ds.sem_perm.key = key;
688 sema[semid].ds.sem_perm.cuid = cred->cr_uid;
689 sema[semid].ds.sem_perm.uid = cred->cr_uid;
690 sema[semid].ds.sem_perm.cgid = cred->cr_gid;
691 sema[semid].ds.sem_perm.gid = cred->cr_gid;
692 sema[semid].ds.sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
693 sema[semid].ds.sem_perm.seq =
694 (sema[semid].ds.sem_perm.seq + 1) & 0x7fff;
695 sema[semid].ds.sem_nsems = nsems;
696 sema[semid].ds.sem_otime = 0;
697 sema[semid].ds.sem_ctime = time_second;
698 sema[semid].ds.sem_base = kmalloc(sizeof(struct sem) * nsems,
699 M_SEM, M_WAITOK|M_ZERO);
700 semtot += nsems;
701 ++sema[semid].gen;
702 lockmgr(&sema[semid].lk, LK_RELEASE);
703 lockmgr(&sema_lk, LK_RELEASE);
704 #ifdef SEM_DEBUG
705 kprintf("sembase = 0x%x, next = 0x%x\n",
706 sema[semid].ds.sem_base, &sem[semtot]);
707 #endif
708 /* eval == 0 */
709 } else {
710 #ifdef SEM_DEBUG
711 kprintf("didn't find it and wasn't asked to create it\n");
712 #endif
713 eval = ENOENT;
714 }
715
716 done:
717 if (eval == 0) {
718 sysmsg->sysmsg_result =
719 IXSEQ_TO_IPCID(semid, sema[semid].ds.sem_perm);
720 }
721 return(eval);
722 }
723
724 /*
725 * MPSAFE
726 */
727 int
sys_semop(struct sysmsg * sysmsg,const struct semop_args * uap)728 sys_semop(struct sysmsg *sysmsg, const struct semop_args *uap)
729 {
730 struct thread *td = curthread;
731 struct prison *pr = td->td_proc->p_ucred->cr_prison;
732 int semid = uap->semid;
733 u_int nsops = uap->nsops;
734 struct sembuf sops[MAX_SOPS];
735 struct semid_pool *semaptr;
736 struct sembuf *sopptr;
737 struct sem *semptr;
738 struct sem *xsemptr;
739 int i, j, eval;
740 int do_undos;
741
742 #ifdef SEM_DEBUG
743 kprintf("call to semop(%d, 0x%x, %u)\n", semid, sops, nsops);
744 #endif
745 if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
746 return (ENOSYS);
747
748 semid = IPCID_TO_IX(semid); /* Convert back to zero origin */
749
750 if (semid < 0 || semid >= seminfo.semmni) {
751 eval = EINVAL;
752 goto done2;
753 }
754
755 wakeup_start_delayed();
756 semaptr = &sema[semid];
757 lockmgr(&semaptr->lk, LK_SHARED);
758
759 if ((semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0) {
760 eval = EINVAL;
761 goto done;
762 }
763 if (semaptr->ds.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
764 eval = EINVAL;
765 goto done;
766 }
767
768 if ((eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_W))) {
769 #ifdef SEM_DEBUG
770 kprintf("eval = %d from ipaccess\n", eval);
771 #endif
772 goto done;
773 }
774
775 if (nsops > MAX_SOPS) {
776 #ifdef SEM_DEBUG
777 kprintf("too many sops (max=%d, nsops=%u)\n", MAX_SOPS, nsops);
778 #endif
779 eval = E2BIG;
780 goto done;
781 }
782
783 if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) {
784 #ifdef SEM_DEBUG
785 kprintf("eval = %d from copyin(%08x, %08x, %u)\n", eval,
786 uap->sops, &sops, nsops * sizeof(sops[0]));
787 #endif
788 goto done;
789 }
790
791 /*
792 * Loop trying to satisfy the vector of requests.
793 * If we reach a point where we must wait, any requests already
794 * performed are rolled back and we go to sleep until some other
795 * process wakes us up. At this point, we start all over again.
796 *
797 * This ensures that from the perspective of other tasks, a set
798 * of requests is atomic (never partially satisfied).
799 */
800 do_undos = 0;
801
802 for (;;) {
803 long gen;
804
805 semptr = NULL;
806
807 for (i = 0; i < nsops; i++) {
808 sopptr = &sops[i];
809
810 if (sopptr->sem_num >= semaptr->ds.sem_nsems) {
811 eval = EFBIG;
812 goto done;
813 }
814
815 semptr = &semaptr->ds.sem_base[sopptr->sem_num];
816 lwkt_getpooltoken(semptr);
817
818 #ifdef SEM_DEBUG
819 kprintf("semop: semaptr=%x, sem_base=%x, semptr=%x, "
820 "sem[%d]=%d : op=%d, flag=%s\n",
821 semaptr, semaptr->ds.sem_base, semptr,
822 sopptr->sem_num, semptr->semval, sopptr->sem_op,
823 (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait");
824 #endif
825
826 if (sopptr->sem_op < 0) {
827 if (semptr->semval + sopptr->sem_op < 0) {
828 #ifdef SEM_DEBUG
829 kprintf("semop: can't do it now\n");
830 #endif
831 break;
832 } else {
833 semptr->semval += sopptr->sem_op;
834 if (semptr->semval == 0 &&
835 semptr->semzcnt > 0) {
836 wakeup(semptr);
837 }
838 }
839 if (sopptr->sem_flg & SEM_UNDO)
840 do_undos = 1;
841 } else if (sopptr->sem_op == 0) {
842 if (semptr->semval > 0) {
843 #ifdef SEM_DEBUG
844 kprintf("semop: not zero now\n");
845 #endif
846 break;
847 }
848 } else {
849 semptr->semval += sopptr->sem_op;
850 if (sopptr->sem_flg & SEM_UNDO)
851 do_undos = 1;
852 if (semptr->semncnt > 0)
853 wakeup(semptr);
854 }
855 lwkt_relpooltoken(semptr);
856 }
857
858 /*
859 * Did we get through the entire vector?
860 */
861 if (i >= nsops)
862 goto donex;
863
864 /*
865 * No, protect the semaphore request which also flags that
866 * a wakeup is needed, then release semptr since we know
867 * another process is likely going to need to access it
868 * soon.
869 */
870 if (sopptr->sem_op == 0)
871 semptr->semzcnt++;
872 else
873 semptr->semncnt++;
874 tsleep_interlock(semptr, PCATCH);
875 lwkt_relpooltoken(semptr);
876
877 /*
878 * Rollback the semaphores we had acquired.
879 */
880 #ifdef SEM_DEBUG
881 kprintf("semop: rollback 0 through %d\n", i-1);
882 #endif
883 for (j = 0; j < i; j++) {
884 xsemptr = &semaptr->ds.sem_base[sops[j].sem_num];
885 lwkt_getpooltoken(xsemptr);
886 xsemptr->semval -= sops[j].sem_op;
887 if (xsemptr->semval == 0 && xsemptr->semzcnt > 0)
888 wakeup(xsemptr);
889 if (xsemptr->semval <= 0 && xsemptr->semncnt > 0)
890 wakeup(xsemptr);
891 lwkt_relpooltoken(xsemptr);
892 }
893
894 /*
895 * If the request that we couldn't satisfy has the
896 * NOWAIT flag set then return with EAGAIN.
897 */
898 if (sopptr->sem_flg & IPC_NOWAIT) {
899 eval = EAGAIN;
900 goto done;
901 }
902
903 /*
904 * Release semaptr->lk while sleeping, allowing other
905 * semops (like SETVAL, SETALL, etc), which require an
906 * exclusive lock and might wake us up.
907 *
908 * Reload and recheck the validity of semaptr on return.
909 * Note that semptr itself might have changed too, but
910 * we've already interlocked for semptr and that is what
911 * will be woken up if it wakes up the tsleep on a MP
912 * race.
913 *
914 * gen protects against destroy/re-create races where the
915 * creds match.
916 */
917 #ifdef SEM_DEBUG
918 kprintf("semop: good night!\n");
919 #endif
920 gen = semaptr->gen;
921 lockmgr(&semaptr->lk, LK_RELEASE);
922 eval = tsleep(semptr, PCATCH | PINTERLOCKED, "semwait", hz);
923 lockmgr(&semaptr->lk, LK_SHARED);
924 #ifdef SEM_DEBUG
925 kprintf("semop: good morning (eval=%d)!\n", eval);
926 #endif
927
928 /* return code is checked below, after sem[nz]cnt-- */
929
930 /*
931 * Make sure that the semaphore still exists
932 */
933 if (semaptr->gen != gen ||
934 (semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0 ||
935 semaptr->ds.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
936 eval = EIDRM;
937 goto done;
938 }
939
940 /*
941 * The semaphore is still alive. Readjust the count of
942 * waiting processes.
943 */
944 semptr = &semaptr->ds.sem_base[sopptr->sem_num];
945 lwkt_getpooltoken(semptr);
946 if (sopptr->sem_op == 0)
947 semptr->semzcnt--;
948 else
949 semptr->semncnt--;
950 lwkt_relpooltoken(semptr);
951
952 /*
953 * Is it really morning, or was our sleep interrupted?
954 * (Delayed check of tsleep() return code because we
955 * need to decrement sem[nz]cnt either way.)
956 */
957 if (eval) {
958 eval = EINTR;
959 goto done;
960 }
961 #ifdef SEM_DEBUG
962 kprintf("semop: good morning!\n");
963 #endif
964 /* RETRY LOOP */
965 }
966
967 donex:
968 /*
969 * Process any SEM_UNDO requests.
970 */
971 if (do_undos) {
972 for (i = 0; i < nsops; i++) {
973 /*
974 * We only need to deal with SEM_UNDO's for non-zero
975 * op's.
976 */
977 int adjval;
978
979 if ((sops[i].sem_flg & SEM_UNDO) == 0)
980 continue;
981 adjval = sops[i].sem_op;
982 if (adjval == 0)
983 continue;
984 eval = semundo_adjust(td->td_proc, semid,
985 sops[i].sem_num, -adjval);
986 if (eval == 0)
987 continue;
988
989 /*
990 * Oh-Oh! We ran out of either sem_undo's or undo's.
991 * Rollback the adjustments to this point and then
992 * rollback the semaphore ups and down so we can return
993 * with an error with all structures restored. We
994 * rollback the undo's in the exact reverse order that
995 * we applied them. This guarantees that we won't run
996 * out of space as we roll things back out.
997 */
998 for (j = i - 1; j >= 0; j--) {
999 if ((sops[j].sem_flg & SEM_UNDO) == 0)
1000 continue;
1001 adjval = sops[j].sem_op;
1002 if (adjval == 0)
1003 continue;
1004 if (semundo_adjust(td->td_proc, semid,
1005 sops[j].sem_num, adjval) != 0)
1006 panic("semop - can't undo undos");
1007 }
1008
1009 for (j = 0; j < nsops; j++) {
1010 xsemptr = &semaptr->ds.sem_base[
1011 sops[j].sem_num];
1012 lwkt_getpooltoken(xsemptr);
1013 xsemptr->semval -= sops[j].sem_op;
1014 if (xsemptr->semval == 0 &&
1015 xsemptr->semzcnt > 0)
1016 wakeup(xsemptr);
1017 if (xsemptr->semval <= 0 &&
1018 xsemptr->semncnt > 0)
1019 wakeup(xsemptr);
1020 lwkt_relpooltoken(xsemptr);
1021 }
1022
1023 #ifdef SEM_DEBUG
1024 kprintf("eval = %d from semundo_adjust\n", eval);
1025 #endif
1026 goto done;
1027 } /* loop through the sops */
1028 } /* if (do_undos) */
1029
1030 /* We're definitely done - set the sempid's */
1031 for (i = 0; i < nsops; i++) {
1032 sopptr = &sops[i];
1033 semptr = &semaptr->ds.sem_base[sopptr->sem_num];
1034 lwkt_getpooltoken(semptr);
1035 semptr->sempid = td->td_proc->p_pid;
1036 lwkt_relpooltoken(semptr);
1037 }
1038
1039 /* Do a wakeup if any semaphore was up'd. */
1040 #ifdef SEM_DEBUG
1041 kprintf("semop: done\n");
1042 #endif
1043 sysmsg->sysmsg_result = 0;
1044 eval = 0;
1045 done:
1046 lockmgr(&semaptr->lk, LK_RELEASE);
1047 wakeup_end_delayed();
1048 done2:
1049 return(eval);
1050 }
1051
1052 /*
1053 * Go through the undo structures for this process and apply the adjustments to
1054 * semaphores.
1055 *
1056 * (p->p_token is held by the caller)
1057 */
1058 void
semexit(struct proc * p)1059 semexit(struct proc *p)
1060 {
1061 struct sem_undo *suptr;
1062 struct sem *semptr;
1063
1064 /*
1065 * We're getting a global token, don't do it if we couldn't
1066 * possibly have any semaphores.
1067 */
1068 if ((p->p_flags & P_SYSVSEM) == 0)
1069 return;
1070 suptr = p->p_sem_undo;
1071 KKASSERT(suptr != NULL);
1072
1073 /*
1074 * Disconnect suptr from the process and increment un_refs to
1075 * prevent anyone else from being able to destroy the structure.
1076 * Do not remove it from the linked list until after we are through
1077 * scanning it as other semaphore calls might still effect it.
1078 */
1079 lwkt_gettoken(&semu_token);
1080 #if 0
1081 /*
1082 * do not disconnect proc yet, doing so prevents RMID
1083 * from cleaning up the structure atomically with SEM_ALLOC
1084 */
1085 p->p_sem_undo = NULL;
1086 p->p_flags &= ~P_SYSVSEM;
1087 suptr->un_proc = NULL;
1088 #endif
1089 ++suptr->un_refs;
1090 lwkt_reltoken(&semu_token);
1091
1092 while (suptr->un_cnt) {
1093 struct semid_pool *semaptr;
1094 int semid;
1095 int semnum;
1096 int adjval;
1097 int ix;
1098
1099 /*
1100 * These values are stable because we hold p->p_token.
1101 * However, they can get ripped out from under us when
1102 * we block or obtain other tokens so we have to re-check.
1103 */
1104 ix = suptr->un_cnt - 1;
1105 semid = suptr->un_ent[ix].un_id;
1106 semnum = suptr->un_ent[ix].un_num;
1107 adjval = suptr->un_ent[ix].un_adjval;
1108
1109 semaptr = &sema[semid];
1110
1111 /*
1112 * Recheck after locking, then execute the undo
1113 * operation. semptr remains valid due to the
1114 * semaptr->lk.
1115 */
1116 lockmgr(&semaptr->lk, LK_EXCLUSIVE);
1117 semptr = &semaptr->ds.sem_base[semnum];
1118 lwkt_getpooltoken(semptr);
1119
1120 if (ix == suptr->un_cnt - 1 &&
1121 semid == suptr->un_ent[ix].un_id &&
1122 semnum == suptr->un_ent[ix].un_num &&
1123 adjval == suptr->un_ent[ix].un_adjval) {
1124 /*
1125 * Only do assertions when we aren't in a SMP race.
1126 */
1127 if ((semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0)
1128 panic("semexit - semid not allocated");
1129 if (semnum >= semaptr->ds.sem_nsems)
1130 panic("semexit - semnum out of range");
1131 --suptr->un_cnt;
1132
1133 if (adjval < 0) {
1134 if (semptr->semval < -adjval)
1135 semptr->semval = 0;
1136 else
1137 semptr->semval += adjval;
1138 } else {
1139 semptr->semval += adjval;
1140 }
1141 wakeup(semptr);
1142 }
1143 lwkt_relpooltoken(semptr);
1144 lockmgr(&semaptr->lk, LK_RELEASE);
1145 }
1146
1147 /*
1148 * Final cleanup, remove from the list, remove the process association,
1149 * then deallocate on last ref.
1150 */
1151 lwkt_gettoken(&semu_token);
1152
1153 p->p_sem_undo = NULL;
1154 p->p_flags &= ~P_SYSVSEM;
1155 suptr->un_proc = NULL;
1156
1157 if (--suptr->un_refs == 0) {
1158 TAILQ_REMOVE(&semu_list, suptr, un_entry);
1159 KKASSERT(suptr->un_cnt == 0);
1160 kfree(suptr, M_SEM);
1161 }
1162 lwkt_reltoken(&semu_token);
1163 }
1164