Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/sysv_sem.c
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1 /* $FreeBSD$ */ 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 24 static MALLOC_DEFINE(M_SEM, "sem", "SVID compatible semaphores"); 25 26 static void seminit __P((void *)); 27 28 #ifndef _SYS_SYSPROTO_H_ 29 struct __semctl_args; 30 int __semctl __P((struct proc *p, struct __semctl_args *uap)); 31 struct semget_args; 32 int semget __P((struct proc *p, struct semget_args *uap)); 33 struct semop_args; 34 int semop __P((struct proc *p, struct semop_args *uap)); 35 #endif 36 37 static struct sem_undo *semu_alloc __P((struct proc *p)); 38 static int semundo_adjust __P((struct proc *p, struct sem_undo **supptr, 39 int semid, int semnum, int adjval)); 40 static void semundo_clear __P((int semid, int semnum)); 41 42 /* XXX casting to (sy_call_t *) is bogus, as usual. */ 43 static sy_call_t *semcalls[] = { 44 (sy_call_t *)__semctl, (sy_call_t *)semget, 45 (sy_call_t *)semop 46 }; 47 48 static int semtot = 0; 49 static struct semid_ds *sema; /* semaphore id pool */ 50 static struct sem *sem; /* semaphore pool */ 51 static struct sem_undo *semu_list; /* list of active undo structures */ 52 static int *semu; /* undo structure pool */ 53 54 struct sem { 55 u_short semval; /* semaphore value */ 56 pid_t sempid; /* pid of last operation */ 57 u_short semncnt; /* # awaiting semval > cval */ 58 u_short semzcnt; /* # awaiting semval = 0 */ 59 }; 60 61 /* 62 * Undo structure (one per process) 63 */ 64 struct sem_undo { 65 struct sem_undo *un_next; /* ptr to next active undo structure */ 66 struct proc *un_proc; /* owner of this structure */ 67 short un_cnt; /* # of active entries */ 68 struct undo { 69 short un_adjval; /* adjust on exit values */ 70 short un_num; /* semaphore # */ 71 int un_id; /* semid */ 72 } un_ent[1]; /* undo entries */ 73 }; 74 75 /* 76 * Configuration parameters 77 */ 78 #ifndef SEMMNI 79 #define SEMMNI 10 /* # of semaphore identifiers */ 80 #endif 81 #ifndef SEMMNS 82 #define SEMMNS 60 /* # of semaphores in system */ 83 #endif 84 #ifndef SEMUME 85 #define SEMUME 10 /* max # of undo entries per process */ 86 #endif 87 #ifndef SEMMNU 88 #define SEMMNU 30 /* # of undo structures in system */ 89 #endif 90 91 /* shouldn't need tuning */ 92 #ifndef SEMMAP 93 #define SEMMAP 30 /* # of entries in semaphore map */ 94 #endif 95 #ifndef SEMMSL 96 #define SEMMSL SEMMNS /* max # of semaphores per id */ 97 #endif 98 #ifndef SEMOPM 99 #define SEMOPM 100 /* max # of operations per semop call */ 100 #endif 101 102 #define SEMVMX 32767 /* semaphore maximum value */ 103 #define SEMAEM 16384 /* adjust on exit max value */ 104 105 /* 106 * Due to the way semaphore memory is allocated, we have to ensure that 107 * SEMUSZ is properly aligned. 108 */ 109 110 #define SEM_ALIGN(bytes) (((bytes) + (sizeof(long) - 1)) & ~(sizeof(long) - 1)) 111 112 /* actual size of an undo structure */ 113 #define SEMUSZ SEM_ALIGN(offsetof(struct sem_undo, un_ent[SEMUME])) 114 115 /* 116 * Macro to find a particular sem_undo vector 117 */ 118 #define SEMU(ix) ((struct sem_undo *)(((intptr_t)semu)+ix * seminfo.semusz)) 119 120 /* 121 * semaphore info struct 122 */ 123 struct seminfo seminfo = { 124 SEMMAP, /* # of entries in semaphore map */ 125 SEMMNI, /* # of semaphore identifiers */ 126 SEMMNS, /* # of semaphores in system */ 127 SEMMNU, /* # of undo structures in system */ 128 SEMMSL, /* max # of semaphores per id */ 129 SEMOPM, /* max # of operations per semop call */ 130 SEMUME, /* max # of undo entries per process */ 131 SEMUSZ, /* size in bytes of undo structure */ 132 SEMVMX, /* semaphore maximum value */ 133 SEMAEM /* adjust on exit max value */ 134 }; 135 136 TUNABLE_INT("kern.ipc.semmap", &seminfo.semmap); 137 TUNABLE_INT("kern.ipc.semmni", &seminfo.semmni); 138 TUNABLE_INT("kern.ipc.semmns", &seminfo.semmns); 139 TUNABLE_INT("kern.ipc.semmnu", &seminfo.semmnu); 140 TUNABLE_INT("kern.ipc.semmsl", &seminfo.semmsl); 141 TUNABLE_INT("kern.ipc.semopm", &seminfo.semopm); 142 TUNABLE_INT("kern.ipc.semume", &seminfo.semume); 143 TUNABLE_INT("kern.ipc.semusz", &seminfo.semusz); 144 TUNABLE_INT("kern.ipc.semvmx", &seminfo.semvmx); 145 TUNABLE_INT("kern.ipc.semaem", &seminfo.semaem); 146 147 SYSCTL_DECL(_kern_ipc); 148 SYSCTL_INT(_kern_ipc, OID_AUTO, semmap, CTLFLAG_RW, &seminfo.semmap, 0, ""); 149 SYSCTL_INT(_kern_ipc, OID_AUTO, semmni, CTLFLAG_RD, &seminfo.semmni, 0, ""); 150 SYSCTL_INT(_kern_ipc, OID_AUTO, semmns, CTLFLAG_RD, &seminfo.semmns, 0, ""); 151 SYSCTL_INT(_kern_ipc, OID_AUTO, semmnu, CTLFLAG_RD, &seminfo.semmnu, 0, ""); 152 SYSCTL_INT(_kern_ipc, OID_AUTO, semmsl, CTLFLAG_RW, &seminfo.semmsl, 0, ""); 153 SYSCTL_INT(_kern_ipc, OID_AUTO, semopm, CTLFLAG_RD, &seminfo.semopm, 0, ""); 154 SYSCTL_INT(_kern_ipc, OID_AUTO, semume, CTLFLAG_RD, &seminfo.semume, 0, ""); 155 SYSCTL_INT(_kern_ipc, OID_AUTO, semusz, CTLFLAG_RD, &seminfo.semusz, 0, ""); 156 SYSCTL_INT(_kern_ipc, OID_AUTO, semvmx, CTLFLAG_RW, &seminfo.semvmx, 0, ""); 157 SYSCTL_INT(_kern_ipc, OID_AUTO, semaem, CTLFLAG_RW, &seminfo.semaem, 0, ""); 158 159 #if 0 160 RO seminfo.semmap /* SEMMAP unused */ 161 RO seminfo.semmni 162 RO seminfo.semmns 163 RO seminfo.semmnu /* undo entries per system */ 164 RW seminfo.semmsl 165 RO seminfo.semopm /* SEMOPM unused */ 166 RO seminfo.semume 167 RO seminfo.semusz /* param - derived from SEMUME for per-proc sizeof */ 168 RO seminfo.semvmx /* SEMVMX unused - user param */ 169 RO seminfo.semaem /* SEMAEM unused - user param */ 170 #endif 171 172 static void 173 seminit(dummy) 174 void *dummy; 175 { 176 register int i; 177 178 sem = malloc(sizeof(struct sem) * seminfo.semmns, M_SEM, M_WAITOK); 179 if (sem == NULL) 180 panic("sem is NULL"); 181 sema = malloc(sizeof(struct semid_ds) * seminfo.semmni, M_SEM, M_WAITOK); 182 if (sema == NULL) 183 panic("sema is NULL"); 184 semu = malloc(seminfo.semmnu * seminfo.semusz, M_SEM, M_WAITOK); 185 if (semu == NULL) 186 panic("semu is NULL"); 187 188 for (i = 0; i < seminfo.semmni; i++) { 189 sema[i].sem_base = 0; 190 sema[i].sem_perm.mode = 0; 191 } 192 for (i = 0; i < seminfo.semmnu; i++) { 193 register struct sem_undo *suptr = SEMU(i); 194 suptr->un_proc = NULL; 195 } 196 semu_list = NULL; 197 } 198 SYSINIT(sysv_sem, SI_SUB_SYSV_SEM, SI_ORDER_FIRST, seminit, NULL) 199 200 /* 201 * Entry point for all SEM calls 202 */ 203 int 204 semsys(p, uap) 205 struct proc *p; 206 /* XXX actually varargs. */ 207 struct semsys_args /* { 208 u_int which; 209 int a2; 210 int a3; 211 int a4; 212 int a5; 213 } */ *uap; 214 { 215 216 if (!jail_sysvipc_allowed && p->p_prison != NULL) 217 return (ENOSYS); 218 219 if (uap->which >= sizeof(semcalls)/sizeof(semcalls[0])) 220 return (EINVAL); 221 return ((*semcalls[uap->which])(p, &uap->a2)); 222 } 223 224 /* 225 * Allocate a new sem_undo structure for a process 226 * (returns ptr to structure or NULL if no more room) 227 */ 228 229 static struct sem_undo * 230 semu_alloc(p) 231 struct proc *p; 232 { 233 register int i; 234 register struct sem_undo *suptr; 235 register struct sem_undo **supptr; 236 int attempt; 237 238 /* 239 * Try twice to allocate something. 240 * (we'll purge any empty structures after the first pass so 241 * two passes are always enough) 242 */ 243 244 for (attempt = 0; attempt < 2; attempt++) { 245 /* 246 * Look for a free structure. 247 * Fill it in and return it if we find one. 248 */ 249 250 for (i = 0; i < seminfo.semmnu; i++) { 251 suptr = SEMU(i); 252 if (suptr->un_proc == NULL) { 253 suptr->un_next = semu_list; 254 semu_list = suptr; 255 suptr->un_cnt = 0; 256 suptr->un_proc = p; 257 return(suptr); 258 } 259 } 260 261 /* 262 * We didn't find a free one, if this is the first attempt 263 * then try to free some structures. 264 */ 265 266 if (attempt == 0) { 267 /* All the structures are in use - try to free some */ 268 int did_something = 0; 269 270 supptr = &semu_list; 271 while ((suptr = *supptr) != NULL) { 272 if (suptr->un_cnt == 0) { 273 suptr->un_proc = NULL; 274 *supptr = suptr->un_next; 275 did_something = 1; 276 } else 277 supptr = &(suptr->un_next); 278 } 279 280 /* If we didn't free anything then just give-up */ 281 if (!did_something) 282 return(NULL); 283 } else { 284 /* 285 * The second pass failed even though we freed 286 * something after the first pass! 287 * This is IMPOSSIBLE! 288 */ 289 panic("semu_alloc - second attempt failed"); 290 } 291 } 292 return (NULL); 293 } 294 295 /* 296 * Adjust a particular entry for a particular proc 297 */ 298 299 static int 300 semundo_adjust(p, supptr, semid, semnum, adjval) 301 register struct proc *p; 302 struct sem_undo **supptr; 303 int semid, semnum; 304 int adjval; 305 { 306 register struct sem_undo *suptr; 307 register struct undo *sunptr; 308 int i; 309 310 /* Look for and remember the sem_undo if the caller doesn't provide 311 it */ 312 313 suptr = *supptr; 314 if (suptr == NULL) { 315 for (suptr = semu_list; suptr != NULL; 316 suptr = suptr->un_next) { 317 if (suptr->un_proc == p) { 318 *supptr = suptr; 319 break; 320 } 321 } 322 if (suptr == NULL) { 323 if (adjval == 0) 324 return(0); 325 suptr = semu_alloc(p); 326 if (suptr == NULL) 327 return(ENOSPC); 328 *supptr = suptr; 329 } 330 } 331 332 /* 333 * Look for the requested entry and adjust it (delete if adjval becomes 334 * 0). 335 */ 336 sunptr = &suptr->un_ent[0]; 337 for (i = 0; i < suptr->un_cnt; i++, sunptr++) { 338 if (sunptr->un_id != semid || sunptr->un_num != semnum) 339 continue; 340 if (adjval == 0) 341 sunptr->un_adjval = 0; 342 else 343 sunptr->un_adjval += adjval; 344 if (sunptr->un_adjval == 0) { 345 suptr->un_cnt--; 346 if (i < suptr->un_cnt) 347 suptr->un_ent[i] = 348 suptr->un_ent[suptr->un_cnt]; 349 } 350 return(0); 351 } 352 353 /* Didn't find the right entry - create it */ 354 if (adjval == 0) 355 return(0); 356 if (suptr->un_cnt != seminfo.semume) { 357 sunptr = &suptr->un_ent[suptr->un_cnt]; 358 suptr->un_cnt++; 359 sunptr->un_adjval = adjval; 360 sunptr->un_id = semid; sunptr->un_num = semnum; 361 } else 362 return(EINVAL); 363 return(0); 364 } 365 366 static void 367 semundo_clear(semid, semnum) 368 int semid, semnum; 369 { 370 register struct sem_undo *suptr; 371 372 for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) { 373 register struct undo *sunptr = &suptr->un_ent[0]; 374 register int i = 0; 375 376 while (i < suptr->un_cnt) { 377 if (sunptr->un_id == semid) { 378 if (semnum == -1 || sunptr->un_num == semnum) { 379 suptr->un_cnt--; 380 if (i < suptr->un_cnt) { 381 suptr->un_ent[i] = 382 suptr->un_ent[suptr->un_cnt]; 383 continue; 384 } 385 } 386 if (semnum != -1) 387 break; 388 } 389 i++, sunptr++; 390 } 391 } 392 } 393 394 /* 395 * Note that the user-mode half of this passes a union, not a pointer 396 */ 397 #ifndef _SYS_SYSPROTO_H_ 398 struct __semctl_args { 399 int semid; 400 int semnum; 401 int cmd; 402 union semun *arg; 403 }; 404 #endif 405 406 int 407 __semctl(p, uap) 408 struct proc *p; 409 register struct __semctl_args *uap; 410 { 411 int semid = uap->semid; 412 int semnum = uap->semnum; 413 int cmd = uap->cmd; 414 union semun *arg = uap->arg; 415 union semun real_arg; 416 struct ucred *cred = p->p_ucred; 417 int i, rval, eval; 418 struct semid_ds sbuf; 419 register struct semid_ds *semaptr; 420 421 #ifdef SEM_DEBUG 422 printf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg); 423 #endif 424 425 if (!jail_sysvipc_allowed && p->p_prison != NULL) 426 return (ENOSYS); 427 428 semid = IPCID_TO_IX(semid); 429 if (semid < 0 || semid >= seminfo.semmni) 430 return(EINVAL); 431 432 semaptr = &sema[semid]; 433 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 || 434 semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) 435 return(EINVAL); 436 437 eval = 0; 438 rval = 0; 439 440 switch (cmd) { 441 case IPC_RMID: 442 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_M))) 443 return(eval); 444 semaptr->sem_perm.cuid = cred->cr_uid; 445 semaptr->sem_perm.uid = cred->cr_uid; 446 semtot -= semaptr->sem_nsems; 447 for (i = semaptr->sem_base - sem; i < semtot; i++) 448 sem[i] = sem[i + semaptr->sem_nsems]; 449 for (i = 0; i < seminfo.semmni; i++) { 450 if ((sema[i].sem_perm.mode & SEM_ALLOC) && 451 sema[i].sem_base > semaptr->sem_base) 452 sema[i].sem_base -= semaptr->sem_nsems; 453 } 454 semaptr->sem_perm.mode = 0; 455 semundo_clear(semid, -1); 456 wakeup((caddr_t)semaptr); 457 break; 458 459 case IPC_SET: 460 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_M))) 461 return(eval); 462 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 463 return(eval); 464 if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf, 465 sizeof(sbuf))) != 0) 466 return(eval); 467 semaptr->sem_perm.uid = sbuf.sem_perm.uid; 468 semaptr->sem_perm.gid = sbuf.sem_perm.gid; 469 semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) | 470 (sbuf.sem_perm.mode & 0777); 471 semaptr->sem_ctime = time_second; 472 break; 473 474 case IPC_STAT: 475 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R))) 476 return(eval); 477 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 478 return(eval); 479 eval = copyout((caddr_t)semaptr, real_arg.buf, 480 sizeof(struct semid_ds)); 481 break; 482 483 case GETNCNT: 484 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R))) 485 return(eval); 486 if (semnum < 0 || semnum >= semaptr->sem_nsems) 487 return(EINVAL); 488 rval = semaptr->sem_base[semnum].semncnt; 489 break; 490 491 case GETPID: 492 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R))) 493 return(eval); 494 if (semnum < 0 || semnum >= semaptr->sem_nsems) 495 return(EINVAL); 496 rval = semaptr->sem_base[semnum].sempid; 497 break; 498 499 case GETVAL: 500 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R))) 501 return(eval); 502 if (semnum < 0 || semnum >= semaptr->sem_nsems) 503 return(EINVAL); 504 rval = semaptr->sem_base[semnum].semval; 505 break; 506 507 case GETALL: 508 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R))) 509 return(eval); 510 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 511 return(eval); 512 for (i = 0; i < semaptr->sem_nsems; i++) { 513 eval = copyout((caddr_t)&semaptr->sem_base[i].semval, 514 &real_arg.array[i], sizeof(real_arg.array[0])); 515 if (eval != 0) 516 break; 517 } 518 break; 519 520 case GETZCNT: 521 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R))) 522 return(eval); 523 if (semnum < 0 || semnum >= semaptr->sem_nsems) 524 return(EINVAL); 525 rval = semaptr->sem_base[semnum].semzcnt; 526 break; 527 528 case SETVAL: 529 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W))) 530 return(eval); 531 if (semnum < 0 || semnum >= semaptr->sem_nsems) 532 return(EINVAL); 533 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 534 return(eval); 535 semaptr->sem_base[semnum].semval = real_arg.val; 536 semundo_clear(semid, semnum); 537 wakeup((caddr_t)semaptr); 538 break; 539 540 case SETALL: 541 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W))) 542 return(eval); 543 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 544 return(eval); 545 for (i = 0; i < semaptr->sem_nsems; i++) { 546 eval = copyin(&real_arg.array[i], 547 (caddr_t)&semaptr->sem_base[i].semval, 548 sizeof(real_arg.array[0])); 549 if (eval != 0) 550 break; 551 } 552 semundo_clear(semid, -1); 553 wakeup((caddr_t)semaptr); 554 break; 555 556 default: 557 return(EINVAL); 558 } 559 560 if (eval == 0) 561 p->p_retval[0] = rval; 562 return(eval); 563 } 564 565 #ifndef _SYS_SYSPROTO_H_ 566 struct semget_args { 567 key_t key; 568 int nsems; 569 int semflg; 570 }; 571 #endif 572 573 int 574 semget(p, uap) 575 struct proc *p; 576 register struct semget_args *uap; 577 { 578 int semid, eval; 579 int key = uap->key; 580 int nsems = uap->nsems; 581 int semflg = uap->semflg; 582 struct ucred *cred = p->p_ucred; 583 584 #ifdef SEM_DEBUG 585 printf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg); 586 #endif 587 588 if (!jail_sysvipc_allowed && p->p_prison != NULL) 589 return (ENOSYS); 590 591 if (key != IPC_PRIVATE) { 592 for (semid = 0; semid < seminfo.semmni; semid++) { 593 if ((sema[semid].sem_perm.mode & SEM_ALLOC) && 594 sema[semid].sem_perm.key == key) 595 break; 596 } 597 if (semid < seminfo.semmni) { 598 #ifdef SEM_DEBUG 599 printf("found public key\n"); 600 #endif 601 if ((eval = ipcperm(p, &sema[semid].sem_perm, 602 semflg & 0700))) 603 return(eval); 604 if (nsems > 0 && sema[semid].sem_nsems < nsems) { 605 #ifdef SEM_DEBUG 606 printf("too small\n"); 607 #endif 608 return(EINVAL); 609 } 610 if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) { 611 #ifdef SEM_DEBUG 612 printf("not exclusive\n"); 613 #endif 614 return(EEXIST); 615 } 616 goto found; 617 } 618 } 619 620 #ifdef SEM_DEBUG 621 printf("need to allocate the semid_ds\n"); 622 #endif 623 if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) { 624 if (nsems <= 0 || nsems > seminfo.semmsl) { 625 #ifdef SEM_DEBUG 626 printf("nsems out of range (0<%d<=%d)\n", nsems, 627 seminfo.semmsl); 628 #endif 629 return(EINVAL); 630 } 631 if (nsems > seminfo.semmns - semtot) { 632 #ifdef SEM_DEBUG 633 printf("not enough semaphores left (need %d, got %d)\n", 634 nsems, seminfo.semmns - semtot); 635 #endif 636 return(ENOSPC); 637 } 638 for (semid = 0; semid < seminfo.semmni; semid++) { 639 if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0) 640 break; 641 } 642 if (semid == seminfo.semmni) { 643 #ifdef SEM_DEBUG 644 printf("no more semid_ds's available\n"); 645 #endif 646 return(ENOSPC); 647 } 648 #ifdef SEM_DEBUG 649 printf("semid %d is available\n", semid); 650 #endif 651 sema[semid].sem_perm.key = key; 652 sema[semid].sem_perm.cuid = cred->cr_uid; 653 sema[semid].sem_perm.uid = cred->cr_uid; 654 sema[semid].sem_perm.cgid = cred->cr_gid; 655 sema[semid].sem_perm.gid = cred->cr_gid; 656 sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC; 657 sema[semid].sem_perm.seq = 658 (sema[semid].sem_perm.seq + 1) & 0x7fff; 659 sema[semid].sem_nsems = nsems; 660 sema[semid].sem_otime = 0; 661 sema[semid].sem_ctime = time_second; 662 sema[semid].sem_base = &sem[semtot]; 663 semtot += nsems; 664 bzero(sema[semid].sem_base, 665 sizeof(sema[semid].sem_base[0])*nsems); 666 #ifdef SEM_DEBUG 667 printf("sembase = 0x%x, next = 0x%x\n", sema[semid].sem_base, 668 &sem[semtot]); 669 #endif 670 } else { 671 #ifdef SEM_DEBUG 672 printf("didn't find it and wasn't asked to create it\n"); 673 #endif 674 return(ENOENT); 675 } 676 677 found: 678 p->p_retval[0] = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm); 679 return(0); 680 } 681 682 #ifndef _SYS_SYSPROTO_H_ 683 struct semop_args { 684 int semid; 685 struct sembuf *sops; 686 u_int nsops; 687 }; 688 #endif 689 690 int 691 semop(p, uap) 692 struct proc *p; 693 register struct semop_args *uap; 694 { 695 int semid = uap->semid; 696 u_int nsops = uap->nsops; 697 struct sembuf sops[MAX_SOPS]; 698 register struct semid_ds *semaptr; 699 register struct sembuf *sopptr; 700 register struct sem *semptr; 701 struct sem_undo *suptr = NULL; 702 int i, j, eval; 703 int do_wakeup, do_undos; 704 705 #ifdef SEM_DEBUG 706 printf("call to semop(%d, 0x%x, %u)\n", semid, sops, nsops); 707 #endif 708 709 if (!jail_sysvipc_allowed && p->p_prison != NULL) 710 return (ENOSYS); 711 712 semid = IPCID_TO_IX(semid); /* Convert back to zero origin */ 713 714 if (semid < 0 || semid >= seminfo.semmni) 715 return(EINVAL); 716 717 semaptr = &sema[semid]; 718 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0) 719 return(EINVAL); 720 if (semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) 721 return(EINVAL); 722 723 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W))) { 724 #ifdef SEM_DEBUG 725 printf("eval = %d from ipaccess\n", eval); 726 #endif 727 return(eval); 728 } 729 730 if (nsops > MAX_SOPS) { 731 #ifdef SEM_DEBUG 732 printf("too many sops (max=%d, nsops=%u)\n", MAX_SOPS, nsops); 733 #endif 734 return(E2BIG); 735 } 736 737 if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) { 738 #ifdef SEM_DEBUG 739 printf("eval = %d from copyin(%08x, %08x, %u)\n", eval, 740 uap->sops, &sops, nsops * sizeof(sops[0])); 741 #endif 742 return(eval); 743 } 744 745 /* 746 * Loop trying to satisfy the vector of requests. 747 * If we reach a point where we must wait, any requests already 748 * performed are rolled back and we go to sleep until some other 749 * process wakes us up. At this point, we start all over again. 750 * 751 * This ensures that from the perspective of other tasks, a set 752 * of requests is atomic (never partially satisfied). 753 */ 754 do_undos = 0; 755 756 for (;;) { 757 do_wakeup = 0; 758 759 for (i = 0; i < nsops; i++) { 760 sopptr = &sops[i]; 761 762 if (sopptr->sem_num >= semaptr->sem_nsems) 763 return(EFBIG); 764 765 semptr = &semaptr->sem_base[sopptr->sem_num]; 766 767 #ifdef SEM_DEBUG 768 printf("semop: semaptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n", 769 semaptr, semaptr->sem_base, semptr, 770 sopptr->sem_num, semptr->semval, sopptr->sem_op, 771 (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait"); 772 #endif 773 774 if (sopptr->sem_op < 0) { 775 if (semptr->semval + sopptr->sem_op < 0) { 776 #ifdef SEM_DEBUG 777 printf("semop: can't do it now\n"); 778 #endif 779 break; 780 } else { 781 semptr->semval += sopptr->sem_op; 782 if (semptr->semval == 0 && 783 semptr->semzcnt > 0) 784 do_wakeup = 1; 785 } 786 if (sopptr->sem_flg & SEM_UNDO) 787 do_undos = 1; 788 } else if (sopptr->sem_op == 0) { 789 if (semptr->semval > 0) { 790 #ifdef SEM_DEBUG 791 printf("semop: not zero now\n"); 792 #endif 793 break; 794 } 795 } else { 796 if (semptr->semncnt > 0) 797 do_wakeup = 1; 798 semptr->semval += sopptr->sem_op; 799 if (sopptr->sem_flg & SEM_UNDO) 800 do_undos = 1; 801 } 802 } 803 804 /* 805 * Did we get through the entire vector? 806 */ 807 if (i >= nsops) 808 goto done; 809 810 /* 811 * No ... rollback anything that we've already done 812 */ 813 #ifdef SEM_DEBUG 814 printf("semop: rollback 0 through %d\n", i-1); 815 #endif 816 for (j = 0; j < i; j++) 817 semaptr->sem_base[sops[j].sem_num].semval -= 818 sops[j].sem_op; 819 820 /* 821 * If the request that we couldn't satisfy has the 822 * NOWAIT flag set then return with EAGAIN. 823 */ 824 if (sopptr->sem_flg & IPC_NOWAIT) 825 return(EAGAIN); 826 827 if (sopptr->sem_op == 0) 828 semptr->semzcnt++; 829 else 830 semptr->semncnt++; 831 832 #ifdef SEM_DEBUG 833 printf("semop: good night!\n"); 834 #endif 835 eval = tsleep((caddr_t)semaptr, (PZERO - 4) | PCATCH, 836 "semwait", 0); 837 /* return code is checked below, after sem[nz]cnt-- */ 838 #ifdef SEM_DEBUG 839 printf("semop: good morning (eval=%d)!\n", eval); 840 #endif 841 842 suptr = NULL; /* sem_undo may have been reallocated */ 843 844 /* 845 * Make sure that the semaphore still exists 846 */ 847 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 || 848 semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) 849 return(EIDRM); 850 851 /* 852 * The semaphore is still alive. Readjust the count of 853 * waiting processes. 854 */ 855 if (sopptr->sem_op == 0) 856 semptr->semzcnt--; 857 else 858 semptr->semncnt--; 859 860 /* 861 * Is it really morning, or was our sleep interrupted? 862 * (Delayed check of msleep() return code because we 863 * need to decrement sem[nz]cnt either way.) 864 */ 865 if (eval != 0) 866 return(EINTR); 867 #ifdef SEM_DEBUG 868 printf("semop: good morning!\n"); 869 #endif 870 } 871 872 done: 873 /* 874 * Process any SEM_UNDO requests. 875 */ 876 if (do_undos) { 877 for (i = 0; i < nsops; i++) { 878 /* 879 * We only need to deal with SEM_UNDO's for non-zero 880 * op's. 881 */ 882 int adjval; 883 884 if ((sops[i].sem_flg & SEM_UNDO) == 0) 885 continue; 886 adjval = sops[i].sem_op; 887 if (adjval == 0) 888 continue; 889 eval = semundo_adjust(p, &suptr, semid, 890 sops[i].sem_num, -adjval); 891 if (eval == 0) 892 continue; 893 894 /* 895 * Oh-Oh! We ran out of either sem_undo's or undo's. 896 * Rollback the adjustments to this point and then 897 * rollback the semaphore ups and down so we can return 898 * with an error with all structures restored. We 899 * rollback the undo's in the exact reverse order that 900 * we applied them. This guarantees that we won't run 901 * out of space as we roll things back out. 902 */ 903 for (j = i - 1; j >= 0; j--) { 904 if ((sops[j].sem_flg & SEM_UNDO) == 0) 905 continue; 906 adjval = sops[j].sem_op; 907 if (adjval == 0) 908 continue; 909 if (semundo_adjust(p, &suptr, semid, 910 sops[j].sem_num, adjval) != 0) 911 panic("semop - can't undo undos"); 912 } 913 914 for (j = 0; j < nsops; j++) 915 semaptr->sem_base[sops[j].sem_num].semval -= 916 sops[j].sem_op; 917 918 #ifdef SEM_DEBUG 919 printf("eval = %d from semundo_adjust\n", eval); 920 #endif 921 return(eval); 922 } /* loop through the sops */ 923 } /* if (do_undos) */ 924 925 /* We're definitely done - set the sempid's */ 926 for (i = 0; i < nsops; i++) { 927 sopptr = &sops[i]; 928 semptr = &semaptr->sem_base[sopptr->sem_num]; 929 semptr->sempid = p->p_pid; 930 } 931 932 /* Do a wakeup if any semaphore was up'd. */ 933 if (do_wakeup) { 934 #ifdef SEM_DEBUG 935 printf("semop: doing wakeup\n"); 936 #endif 937 wakeup((caddr_t)semaptr); 938 #ifdef SEM_DEBUG 939 printf("semop: back from wakeup\n"); 940 #endif 941 } 942 #ifdef SEM_DEBUG 943 printf("semop: done\n"); 944 #endif 945 p->p_retval[0] = 0; 946 return(0); 947 } 948 949 /* 950 * Go through the undo structures for this process and apply the adjustments to 951 * semaphores. 952 */ 953 void 954 semexit(p) 955 struct proc *p; 956 { 957 register struct sem_undo *suptr; 958 register struct sem_undo **supptr; 959 int did_something; 960 961 did_something = 0; 962 963 /* 964 * Go through the chain of undo vectors looking for one 965 * associated with this process. 966 */ 967 968 for (supptr = &semu_list; (suptr = *supptr) != NULL; 969 supptr = &suptr->un_next) { 970 if (suptr->un_proc == p) 971 break; 972 } 973 974 if (suptr == NULL) 975 return; 976 977 #ifdef SEM_DEBUG 978 printf("proc @%08x has undo structure with %d entries\n", p, 979 suptr->un_cnt); 980 #endif 981 982 /* 983 * If there are any active undo elements then process them. 984 */ 985 if (suptr->un_cnt > 0) { 986 int ix; 987 988 for (ix = 0; ix < suptr->un_cnt; ix++) { 989 int semid = suptr->un_ent[ix].un_id; 990 int semnum = suptr->un_ent[ix].un_num; 991 int adjval = suptr->un_ent[ix].un_adjval; 992 struct semid_ds *semaptr; 993 994 semaptr = &sema[semid]; 995 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0) 996 panic("semexit - semid not allocated"); 997 if (semnum >= semaptr->sem_nsems) 998 panic("semexit - semnum out of range"); 999 1000 #ifdef SEM_DEBUG 1001 printf("semexit: %08x id=%d num=%d(adj=%d) ; sem=%d\n", 1002 suptr->un_proc, suptr->un_ent[ix].un_id, 1003 suptr->un_ent[ix].un_num, 1004 suptr->un_ent[ix].un_adjval, 1005 semaptr->sem_base[semnum].semval); 1006 #endif 1007 1008 if (adjval < 0) { 1009 if (semaptr->sem_base[semnum].semval < -adjval) 1010 semaptr->sem_base[semnum].semval = 0; 1011 else 1012 semaptr->sem_base[semnum].semval += 1013 adjval; 1014 } else 1015 semaptr->sem_base[semnum].semval += adjval; 1016 1017 wakeup((caddr_t)semaptr); 1018 #ifdef SEM_DEBUG 1019 printf("semexit: back from wakeup\n"); 1020 #endif 1021 } 1022 } 1023 1024 /* 1025 * Deallocate the undo vector. 1026 */ 1027 #ifdef SEM_DEBUG 1028 printf("removing vector\n"); 1029 #endif 1030 suptr->un_proc = NULL; 1031 *supptr = suptr->un_next; 1032 }
Cache object: 3109dbe9ac129171c1e496453dffe0ef
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