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/sysproto.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 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 * 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 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 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 sunptr = &suptr->un_ent[0]; 295 i = 0; 296 297 while (i < suptr->un_cnt) { 298 if (sunptr->un_id == semid) { 299 if (semnum == -1 || sunptr->un_num == semnum) { 300 suptr->un_cnt--; 301 if (i < suptr->un_cnt) { 302 suptr->un_ent[i] = 303 suptr->un_ent[suptr->un_cnt]; 304 /* 305 * do not increment i 306 * or sunptr after copydown. 307 */ 308 continue; 309 } 310 } 311 if (semnum != -1) 312 break; 313 } 314 ++i; 315 ++sunptr; 316 } 317 318 lwkt_reltoken(&p->p_token); 319 PRELE(p); 320 321 /* 322 * Handle deletion races 323 */ 324 sunext = TAILQ_NEXT(suptr, un_entry); 325 if (--suptr->un_refs == 0 && suptr->un_proc == NULL) { 326 KKASSERT(suptr->un_cnt == 0); 327 TAILQ_REMOVE(&semu_list, suptr, un_entry); 328 kfree(suptr, M_SEM); 329 } 330 } 331 lwkt_reltoken(&semu_token); 332 } 333 334 /* 335 * Note that the user-mode half of this passes a union, not a pointer 336 * 337 * MPALMOSTSAFE 338 */ 339 int 340 sys___semctl(struct __semctl_args *uap) 341 { 342 struct thread *td = curthread; 343 struct prison *pr = td->td_proc->p_ucred->cr_prison; 344 int semid = uap->semid; 345 int semnum = uap->semnum; 346 int cmd = uap->cmd; 347 union semun *arg = uap->arg; 348 union semun real_arg; 349 struct ucred *cred = td->td_ucred; 350 int i, rval, eval; 351 struct semid_ds sbuf; 352 struct semid_pool *semaptr; 353 struct sem *semptr; 354 355 #ifdef SEM_DEBUG 356 kprintf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg); 357 #endif 358 359 if (pr && !pr->pr_sysvipc_allowed) 360 return (ENOSYS); 361 362 semid = IPCID_TO_IX(semid); 363 if (semid < 0 || semid >= seminfo.semmni) { 364 return(EINVAL); 365 } 366 semaptr = &sema[semid]; 367 lockmgr(&semaptr->lk, LK_EXCLUSIVE); 368 369 if ((semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0 || 370 semaptr->ds.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) { 371 lockmgr(&semaptr->lk, LK_RELEASE); 372 return(EINVAL); 373 } 374 375 eval = 0; 376 rval = 0; 377 378 switch (cmd) { 379 case IPC_RMID: 380 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_M); 381 if (eval != 0) 382 break; 383 semaptr->ds.sem_perm.cuid = cred->cr_uid; 384 semaptr->ds.sem_perm.uid = cred->cr_uid; 385 386 /* 387 * NOTE: Nobody will be waiting on the semaphores since 388 * we have an exclusive lock on semaptr->lk). 389 */ 390 lockmgr(&sema_lk, LK_EXCLUSIVE); 391 semtot -= semaptr->ds.sem_nsems; 392 kfree(semaptr->ds.sem_base, M_SEM); 393 semaptr->ds.sem_base = NULL; 394 semaptr->ds.sem_perm.mode = 0; /* clears SEM_ALLOC */ 395 lockmgr(&sema_lk, LK_RELEASE); 396 397 semundo_clear(semid, -1); 398 break; 399 400 case IPC_SET: 401 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_M); 402 if (eval) 403 break; 404 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 405 break; 406 if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf, 407 sizeof(sbuf))) != 0) { 408 break; 409 } 410 semaptr->ds.sem_perm.uid = sbuf.sem_perm.uid; 411 semaptr->ds.sem_perm.gid = sbuf.sem_perm.gid; 412 semaptr->ds.sem_perm.mode = 413 (semaptr->ds.sem_perm.mode & ~0777) | 414 (sbuf.sem_perm.mode & 0777); 415 semaptr->ds.sem_ctime = time_second; 416 break; 417 418 case IPC_STAT: 419 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 420 if (eval) 421 break; 422 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 423 break; 424 eval = copyout(&semaptr->ds, real_arg.buf, 425 sizeof(struct semid_ds)); 426 break; 427 case SEM_STAT: 428 /* 429 * For this command we assume semid is an array index 430 * rather than an IPC id. However, the conversion is 431 * just a mask so just validate that the passed-in semid 432 * matches the masked semid. 433 */ 434 if (uap->semid != semid) { 435 eval = EINVAL; 436 break; 437 } 438 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 439 if (eval) 440 break; 441 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 442 break; 443 eval = copyout(&semaptr->ds, real_arg.buf, 444 sizeof(struct semid_ds)); 445 rval = IXSEQ_TO_IPCID(semid, semaptr->ds.sem_perm); 446 break; 447 448 case GETNCNT: 449 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 450 if (eval) 451 break; 452 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) { 453 eval = EINVAL; 454 break; 455 } 456 rval = semaptr->ds.sem_base[semnum].semncnt; 457 break; 458 459 case GETPID: 460 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 461 if (eval) 462 break; 463 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) { 464 eval = EINVAL; 465 break; 466 } 467 rval = semaptr->ds.sem_base[semnum].sempid; 468 break; 469 470 case GETVAL: 471 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 472 if (eval) 473 break; 474 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) { 475 eval = EINVAL; 476 break; 477 } 478 rval = semaptr->ds.sem_base[semnum].semval; 479 break; 480 481 case GETALL: 482 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 483 if (eval) 484 break; 485 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 486 break; 487 for (i = 0; i < semaptr->ds.sem_nsems; i++) { 488 eval = copyout(&semaptr->ds.sem_base[i].semval, 489 &real_arg.array[i], 490 sizeof(real_arg.array[0])); 491 if (eval) 492 break; 493 } 494 break; 495 496 case GETZCNT: 497 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_R); 498 if (eval) 499 break; 500 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) { 501 eval = EINVAL; 502 break; 503 } 504 rval = semaptr->ds.sem_base[semnum].semzcnt; 505 break; 506 507 case SETVAL: 508 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_W); 509 if (eval) 510 break; 511 if (semnum < 0 || semnum >= semaptr->ds.sem_nsems) { 512 eval = EINVAL; 513 break; 514 } 515 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 516 break; 517 518 /* 519 * Because we hold semaptr->lk exclusively we can safely 520 * modify any semptr content without acquiring its token. 521 */ 522 semptr = &semaptr->ds.sem_base[semnum]; 523 semptr->semval = real_arg.val; 524 semundo_clear(semid, semnum); 525 if (semptr->semzcnt || semptr->semncnt) 526 wakeup(semptr); 527 break; 528 529 case SETALL: 530 eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_W); 531 if (eval) 532 break; 533 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 534 break; 535 /* 536 * Because we hold semaptr->lk exclusively we can safely 537 * modify any semptr content without acquiring its token. 538 */ 539 for (i = 0; i < semaptr->ds.sem_nsems; i++) { 540 semptr = &semaptr->ds.sem_base[i]; 541 eval = copyin(&real_arg.array[i], 542 (caddr_t)&semptr->semval, 543 sizeof(real_arg.array[0])); 544 if (semptr->semzcnt || semptr->semncnt) 545 wakeup(semptr); 546 if (eval != 0) 547 break; 548 } 549 semundo_clear(semid, -1); 550 break; 551 552 default: 553 eval = EINVAL; 554 break; 555 } 556 lockmgr(&semaptr->lk, LK_RELEASE); 557 558 if (eval == 0) 559 uap->sysmsg_result = rval; 560 return(eval); 561 } 562 563 /* 564 * MPALMOSTSAFE 565 */ 566 int 567 sys_semget(struct semget_args *uap) 568 { 569 struct thread *td = curthread; 570 struct prison *pr = td->td_proc->p_ucred->cr_prison; 571 int semid, eval; 572 int key = uap->key; 573 int nsems = uap->nsems; 574 int semflg = uap->semflg; 575 struct ucred *cred = td->td_ucred; 576 577 #ifdef SEM_DEBUG 578 kprintf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg); 579 #endif 580 581 if (pr && !pr->pr_sysvipc_allowed) 582 return (ENOSYS); 583 584 eval = 0; 585 586 if (key != IPC_PRIVATE) { 587 for (semid = 0; semid < seminfo.semmni; semid++) { 588 if ((sema[semid].ds.sem_perm.mode & SEM_ALLOC) == 0 || 589 sema[semid].ds.sem_perm.key != key) { 590 continue; 591 } 592 lockmgr(&sema[semid].lk, LK_EXCLUSIVE); 593 if ((sema[semid].ds.sem_perm.mode & SEM_ALLOC) == 0 || 594 sema[semid].ds.sem_perm.key != key) { 595 lockmgr(&sema[semid].lk, LK_RELEASE); 596 continue; 597 } 598 break; 599 } 600 if (semid < seminfo.semmni) { 601 /* sema[semid].lk still locked from above */ 602 #ifdef SEM_DEBUG 603 kprintf("found public key\n"); 604 #endif 605 if ((eval = ipcperm(td->td_proc, 606 &sema[semid].ds.sem_perm, 607 semflg & 0700))) { 608 lockmgr(&sema[semid].lk, LK_RELEASE); 609 goto done; 610 } 611 if (nsems > 0 && sema[semid].ds.sem_nsems < nsems) { 612 #ifdef SEM_DEBUG 613 kprintf("too small\n"); 614 #endif 615 eval = EINVAL; 616 lockmgr(&sema[semid].lk, LK_RELEASE); 617 goto done; 618 } 619 if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) { 620 #ifdef SEM_DEBUG 621 kprintf("not exclusive\n"); 622 #endif 623 eval = EEXIST; 624 lockmgr(&sema[semid].lk, LK_RELEASE); 625 goto done; 626 } 627 628 /* 629 * Return this one. 630 */ 631 lockmgr(&sema[semid].lk, LK_RELEASE); 632 goto done; 633 } 634 } 635 636 #ifdef SEM_DEBUG 637 kprintf("need to allocate the semid_ds\n"); 638 #endif 639 if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) { 640 if (nsems <= 0 || nsems > seminfo.semmsl) { 641 #ifdef SEM_DEBUG 642 kprintf("nsems out of range (0<%d<=%d)\n", 643 nsems, seminfo.semmsl); 644 #endif 645 eval = EINVAL; 646 goto done; 647 } 648 649 /* 650 * SEM_ALLOC flag cannot be set unless sema_lk is locked. 651 * semtot field also protected by sema_lk. 652 */ 653 lockmgr(&sema_lk, LK_EXCLUSIVE); 654 if (nsems > seminfo.semmns - semtot) { 655 #ifdef SEM_DEBUG 656 kprintf("not enough semaphores left " 657 "(need %d, got %d)\n", 658 nsems, seminfo.semmns - semtot); 659 #endif 660 eval = ENOSPC; 661 lockmgr(&sema_lk, LK_RELEASE); 662 goto done; 663 } 664 for (semid = 0; semid < seminfo.semmni; semid++) { 665 if ((sema[semid].ds.sem_perm.mode & SEM_ALLOC) == 0) 666 break; 667 } 668 if (semid == seminfo.semmni) { 669 #ifdef SEM_DEBUG 670 kprintf("no more semid_ds's available\n"); 671 #endif 672 eval = ENOSPC; 673 lockmgr(&sema_lk, LK_RELEASE); 674 goto done; 675 } 676 #ifdef SEM_DEBUG 677 kprintf("semid %d is available\n", semid); 678 #endif 679 lockmgr(&sema[semid].lk, LK_EXCLUSIVE); 680 sema[semid].ds.sem_perm.key = key; 681 sema[semid].ds.sem_perm.cuid = cred->cr_uid; 682 sema[semid].ds.sem_perm.uid = cred->cr_uid; 683 sema[semid].ds.sem_perm.cgid = cred->cr_gid; 684 sema[semid].ds.sem_perm.gid = cred->cr_gid; 685 sema[semid].ds.sem_perm.mode = (semflg & 0777) | SEM_ALLOC; 686 sema[semid].ds.sem_perm.seq = 687 (sema[semid].ds.sem_perm.seq + 1) & 0x7fff; 688 sema[semid].ds.sem_nsems = nsems; 689 sema[semid].ds.sem_otime = 0; 690 sema[semid].ds.sem_ctime = time_second; 691 sema[semid].ds.sem_base = kmalloc(sizeof(struct sem) * nsems, 692 M_SEM, M_WAITOK|M_ZERO); 693 semtot += nsems; 694 ++sema[semid].gen; 695 lockmgr(&sema[semid].lk, LK_RELEASE); 696 lockmgr(&sema_lk, LK_RELEASE); 697 #ifdef SEM_DEBUG 698 kprintf("sembase = 0x%x, next = 0x%x\n", 699 sema[semid].ds.sem_base, &sem[semtot]); 700 #endif 701 /* eval == 0 */ 702 } else { 703 #ifdef SEM_DEBUG 704 kprintf("didn't find it and wasn't asked to create it\n"); 705 #endif 706 eval = ENOENT; 707 } 708 709 done: 710 if (eval == 0) { 711 uap->sysmsg_result = 712 IXSEQ_TO_IPCID(semid, sema[semid].ds.sem_perm); 713 } 714 return(eval); 715 } 716 717 /* 718 * MPSAFE 719 */ 720 int 721 sys_semop(struct semop_args *uap) 722 { 723 struct thread *td = curthread; 724 struct prison *pr = td->td_proc->p_ucred->cr_prison; 725 int semid = uap->semid; 726 u_int nsops = uap->nsops; 727 struct sembuf sops[MAX_SOPS]; 728 struct semid_pool *semaptr; 729 struct sembuf *sopptr; 730 struct sem *semptr; 731 struct sem *xsemptr; 732 int i, j, eval; 733 int do_undos; 734 735 #ifdef SEM_DEBUG 736 kprintf("call to semop(%d, 0x%x, %u)\n", semid, sops, nsops); 737 #endif 738 if (pr && !pr->pr_sysvipc_allowed) 739 return (ENOSYS); 740 741 semid = IPCID_TO_IX(semid); /* Convert back to zero origin */ 742 743 if (semid < 0 || semid >= seminfo.semmni) { 744 eval = EINVAL; 745 goto done2; 746 } 747 748 wakeup_start_delayed(); 749 semaptr = &sema[semid]; 750 lockmgr(&semaptr->lk, LK_SHARED); 751 752 if ((semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0) { 753 eval = EINVAL; 754 goto done; 755 } 756 if (semaptr->ds.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) { 757 eval = EINVAL; 758 goto done; 759 } 760 761 if ((eval = ipcperm(td->td_proc, &semaptr->ds.sem_perm, IPC_W))) { 762 #ifdef SEM_DEBUG 763 kprintf("eval = %d from ipaccess\n", eval); 764 #endif 765 goto done; 766 } 767 768 if (nsops > MAX_SOPS) { 769 #ifdef SEM_DEBUG 770 kprintf("too many sops (max=%d, nsops=%u)\n", MAX_SOPS, nsops); 771 #endif 772 eval = E2BIG; 773 goto done; 774 } 775 776 if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) { 777 #ifdef SEM_DEBUG 778 kprintf("eval = %d from copyin(%08x, %08x, %u)\n", eval, 779 uap->sops, &sops, nsops * sizeof(sops[0])); 780 #endif 781 goto done; 782 } 783 784 /* 785 * Loop trying to satisfy the vector of requests. 786 * If we reach a point where we must wait, any requests already 787 * performed are rolled back and we go to sleep until some other 788 * process wakes us up. At this point, we start all over again. 789 * 790 * This ensures that from the perspective of other tasks, a set 791 * of requests is atomic (never partially satisfied). 792 */ 793 do_undos = 0; 794 795 for (;;) { 796 long gen; 797 798 semptr = NULL; 799 800 for (i = 0; i < nsops; i++) { 801 sopptr = &sops[i]; 802 803 if (sopptr->sem_num >= semaptr->ds.sem_nsems) { 804 eval = EFBIG; 805 goto done; 806 } 807 808 semptr = &semaptr->ds.sem_base[sopptr->sem_num]; 809 lwkt_getpooltoken(semptr); 810 811 #ifdef SEM_DEBUG 812 kprintf("semop: semaptr=%x, sem_base=%x, semptr=%x, " 813 "sem[%d]=%d : op=%d, flag=%s\n", 814 semaptr, semaptr->ds.sem_base, semptr, 815 sopptr->sem_num, semptr->semval, sopptr->sem_op, 816 (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait"); 817 #endif 818 819 if (sopptr->sem_op < 0) { 820 if (semptr->semval + sopptr->sem_op < 0) { 821 #ifdef SEM_DEBUG 822 kprintf("semop: can't do it now\n"); 823 #endif 824 break; 825 } else { 826 semptr->semval += sopptr->sem_op; 827 if (semptr->semval == 0 && 828 semptr->semzcnt > 0) { 829 wakeup(semptr); 830 } 831 } 832 if (sopptr->sem_flg & SEM_UNDO) 833 do_undos = 1; 834 } else if (sopptr->sem_op == 0) { 835 if (semptr->semval > 0) { 836 #ifdef SEM_DEBUG 837 kprintf("semop: not zero now\n"); 838 #endif 839 break; 840 } 841 } else { 842 semptr->semval += sopptr->sem_op; 843 if (sopptr->sem_flg & SEM_UNDO) 844 do_undos = 1; 845 if (semptr->semncnt > 0) 846 wakeup(semptr); 847 } 848 lwkt_relpooltoken(semptr); 849 } 850 851 /* 852 * Did we get through the entire vector? 853 */ 854 if (i >= nsops) 855 goto donex; 856 857 /* 858 * No, protect the semaphore request which also flags that 859 * a wakeup is needed, then release semptr since we know 860 * another process is likely going to need to access it 861 * soon. 862 */ 863 if (sopptr->sem_op == 0) 864 semptr->semzcnt++; 865 else 866 semptr->semncnt++; 867 tsleep_interlock(semptr, PCATCH); 868 lwkt_relpooltoken(semptr); 869 870 /* 871 * Rollback the semaphores we had acquired. 872 */ 873 #ifdef SEM_DEBUG 874 kprintf("semop: rollback 0 through %d\n", i-1); 875 #endif 876 for (j = 0; j < i; j++) { 877 xsemptr = &semaptr->ds.sem_base[sops[j].sem_num]; 878 lwkt_getpooltoken(xsemptr); 879 xsemptr->semval -= sops[j].sem_op; 880 if (xsemptr->semval == 0 && xsemptr->semzcnt > 0) 881 wakeup(xsemptr); 882 if (xsemptr->semval <= 0 && xsemptr->semncnt > 0) 883 wakeup(xsemptr); 884 lwkt_relpooltoken(xsemptr); 885 } 886 887 /* 888 * If the request that we couldn't satisfy has the 889 * NOWAIT flag set then return with EAGAIN. 890 */ 891 if (sopptr->sem_flg & IPC_NOWAIT) { 892 eval = EAGAIN; 893 goto done; 894 } 895 896 /* 897 * Release semaptr->lk while sleeping, allowing other 898 * semops (like SETVAL, SETALL, etc), which require an 899 * exclusive lock and might wake us up. 900 * 901 * Reload and recheck the validity of semaptr on return. 902 * Note that semptr itself might have changed too, but 903 * we've already interlocked for semptr and that is what 904 * will be woken up if it wakes up the tsleep on a MP 905 * race. 906 * 907 * gen protects against destroy/re-create races where the 908 * creds match. 909 */ 910 #ifdef SEM_DEBUG 911 kprintf("semop: good night!\n"); 912 #endif 913 gen = semaptr->gen; 914 lockmgr(&semaptr->lk, LK_RELEASE); 915 eval = tsleep(semptr, PCATCH | PINTERLOCKED, "semwait", hz); 916 lockmgr(&semaptr->lk, LK_SHARED); 917 #ifdef SEM_DEBUG 918 kprintf("semop: good morning (eval=%d)!\n", eval); 919 #endif 920 921 /* return code is checked below, after sem[nz]cnt-- */ 922 923 /* 924 * Make sure that the semaphore still exists 925 */ 926 if (semaptr->gen != gen || 927 (semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0 || 928 semaptr->ds.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) { 929 eval = EIDRM; 930 goto done; 931 } 932 933 /* 934 * The semaphore is still alive. Readjust the count of 935 * waiting processes. 936 */ 937 semptr = &semaptr->ds.sem_base[sopptr->sem_num]; 938 lwkt_getpooltoken(semptr); 939 if (sopptr->sem_op == 0) 940 semptr->semzcnt--; 941 else 942 semptr->semncnt--; 943 lwkt_relpooltoken(semptr); 944 945 /* 946 * Is it really morning, or was our sleep interrupted? 947 * (Delayed check of tsleep() return code because we 948 * need to decrement sem[nz]cnt either way.) 949 */ 950 if (eval) { 951 eval = EINTR; 952 goto done; 953 } 954 #ifdef SEM_DEBUG 955 kprintf("semop: good morning!\n"); 956 #endif 957 /* RETRY LOOP */ 958 } 959 960 donex: 961 /* 962 * Process any SEM_UNDO requests. 963 */ 964 if (do_undos) { 965 for (i = 0; i < nsops; i++) { 966 /* 967 * We only need to deal with SEM_UNDO's for non-zero 968 * op's. 969 */ 970 int adjval; 971 972 if ((sops[i].sem_flg & SEM_UNDO) == 0) 973 continue; 974 adjval = sops[i].sem_op; 975 if (adjval == 0) 976 continue; 977 eval = semundo_adjust(td->td_proc, semid, 978 sops[i].sem_num, -adjval); 979 if (eval == 0) 980 continue; 981 982 /* 983 * Oh-Oh! We ran out of either sem_undo's or undo's. 984 * Rollback the adjustments to this point and then 985 * rollback the semaphore ups and down so we can return 986 * with an error with all structures restored. We 987 * rollback the undo's in the exact reverse order that 988 * we applied them. This guarantees that we won't run 989 * out of space as we roll things back out. 990 */ 991 for (j = i - 1; j >= 0; j--) { 992 if ((sops[j].sem_flg & SEM_UNDO) == 0) 993 continue; 994 adjval = sops[j].sem_op; 995 if (adjval == 0) 996 continue; 997 if (semundo_adjust(td->td_proc, semid, 998 sops[j].sem_num, adjval) != 0) 999 panic("semop - can't undo undos"); 1000 } 1001 1002 for (j = 0; j < nsops; j++) { 1003 xsemptr = &semaptr->ds.sem_base[ 1004 sops[j].sem_num]; 1005 lwkt_getpooltoken(xsemptr); 1006 xsemptr->semval -= sops[j].sem_op; 1007 if (xsemptr->semval == 0 && 1008 xsemptr->semzcnt > 0) 1009 wakeup(xsemptr); 1010 if (xsemptr->semval <= 0 && 1011 xsemptr->semncnt > 0) 1012 wakeup(xsemptr); 1013 lwkt_relpooltoken(xsemptr); 1014 } 1015 1016 #ifdef SEM_DEBUG 1017 kprintf("eval = %d from semundo_adjust\n", eval); 1018 #endif 1019 goto done; 1020 } /* loop through the sops */ 1021 } /* if (do_undos) */ 1022 1023 /* We're definitely done - set the sempid's */ 1024 for (i = 0; i < nsops; i++) { 1025 sopptr = &sops[i]; 1026 semptr = &semaptr->ds.sem_base[sopptr->sem_num]; 1027 lwkt_getpooltoken(semptr); 1028 semptr->sempid = td->td_proc->p_pid; 1029 lwkt_relpooltoken(semptr); 1030 } 1031 1032 /* Do a wakeup if any semaphore was up'd. */ 1033 #ifdef SEM_DEBUG 1034 kprintf("semop: done\n"); 1035 #endif 1036 uap->sysmsg_result = 0; 1037 eval = 0; 1038 done: 1039 lockmgr(&semaptr->lk, LK_RELEASE); 1040 wakeup_end_delayed(); 1041 done2: 1042 return(eval); 1043 } 1044 1045 /* 1046 * Go through the undo structures for this process and apply the adjustments to 1047 * semaphores. 1048 * 1049 * (p->p_token is held by the caller) 1050 */ 1051 void 1052 semexit(struct proc *p) 1053 { 1054 struct sem_undo *suptr; 1055 struct sem *semptr; 1056 1057 /* 1058 * We're getting a global token, don't do it if we couldn't 1059 * possibly have any semaphores. 1060 */ 1061 if ((p->p_flags & P_SYSVSEM) == 0) 1062 return; 1063 suptr = p->p_sem_undo; 1064 KKASSERT(suptr != NULL); 1065 1066 /* 1067 * Disconnect suptr from the process and increment un_refs to 1068 * prevent anyone else from being able to destroy the structure. 1069 * Do not remove it from the linked list until after we are through 1070 * scanning it as other semaphore calls might still effect it. 1071 */ 1072 lwkt_gettoken(&semu_token); 1073 p->p_sem_undo = NULL; 1074 p->p_flags &= ~P_SYSVSEM; 1075 suptr->un_proc = NULL; 1076 ++suptr->un_refs; 1077 lwkt_reltoken(&semu_token); 1078 1079 while (suptr->un_cnt) { 1080 struct semid_pool *semaptr; 1081 int semid; 1082 int semnum; 1083 int adjval; 1084 int ix; 1085 1086 /* 1087 * These values are stable because we hold p->p_token. 1088 * However, they can get ripped out from under us when 1089 * we block or obtain other tokens so we have to re-check. 1090 */ 1091 ix = suptr->un_cnt - 1; 1092 semid = suptr->un_ent[ix].un_id; 1093 semnum = suptr->un_ent[ix].un_num; 1094 adjval = suptr->un_ent[ix].un_adjval; 1095 1096 semaptr = &sema[semid]; 1097 1098 /* 1099 * Recheck after locking, then execute the undo 1100 * operation. semptr remains valid due to the 1101 * semaptr->lk. 1102 */ 1103 lockmgr(&semaptr->lk, LK_SHARED); 1104 semptr = &semaptr->ds.sem_base[semnum]; 1105 lwkt_getpooltoken(semptr); 1106 1107 if (ix == suptr->un_cnt - 1 && 1108 semid == suptr->un_ent[ix].un_id && 1109 semnum == suptr->un_ent[ix].un_num && 1110 adjval == suptr->un_ent[ix].un_adjval) { 1111 /* 1112 * Only do assertions when we aren't in a SMP race. 1113 */ 1114 if ((semaptr->ds.sem_perm.mode & SEM_ALLOC) == 0) 1115 panic("semexit - semid not allocated"); 1116 if (semnum >= semaptr->ds.sem_nsems) 1117 panic("semexit - semnum out of range"); 1118 --suptr->un_cnt; 1119 1120 if (adjval < 0) { 1121 if (semptr->semval < -adjval) 1122 semptr->semval = 0; 1123 else 1124 semptr->semval += adjval; 1125 } else { 1126 semptr->semval += adjval; 1127 } 1128 wakeup(semptr); 1129 } 1130 lwkt_relpooltoken(semptr); 1131 lockmgr(&semaptr->lk, LK_RELEASE); 1132 } 1133 1134 /* 1135 * Final cleanup, remove from the list and deallocate on the 1136 * last ref only. 1137 */ 1138 lwkt_gettoken(&semu_token); 1139 if (--suptr->un_refs == 0) { 1140 TAILQ_REMOVE(&semu_list, suptr, un_entry); 1141 KKASSERT(suptr->un_cnt == 0); 1142 kfree(suptr, M_SEM); 1143 } 1144 lwkt_reltoken(&semu_token); 1145 } 1146