uipc_sem.c revision 1.34
1 /* $NetBSD: uipc_sem.c,v 1.34 2011/04/16 20:39:18 rmind Exp $ */ 2 3 /*- 4 * Copyright (c) 2011 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Mindaugas Rasiukevicius. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * Copyright (c) 2002 Alfred Perlstein <alfred (at) FreeBSD.org> 34 * All rights reserved. 35 * 36 * Redistribution and use in source and binary forms, with or without 37 * modification, are permitted provided that the following conditions 38 * are met: 39 * 1. Redistributions of source code must retain the above copyright 40 * notice, this list of conditions and the following disclaimer. 41 * 2. Redistributions in binary form must reproduce the above copyright 42 * notice, this list of conditions and the following disclaimer in the 43 * documentation and/or other materials provided with the distribution. 44 * 45 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 46 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 47 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 48 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 49 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 50 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 51 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 52 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 53 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 54 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 55 * SUCH DAMAGE. 56 */ 57 58 /* 59 * Implementation of POSIX semaphore. 60 */ 61 62 #include <sys/cdefs.h> 63 __KERNEL_RCSID(0, "$NetBSD: uipc_sem.c,v 1.34 2011/04/16 20:39:18 rmind Exp $"); 64 65 #include <sys/param.h> 66 #include <sys/kernel.h> 67 68 #include <sys/atomic.h> 69 #include <sys/proc.h> 70 #include <sys/ksem.h> 71 #include <sys/syscall.h> 72 #include <sys/stat.h> 73 #include <sys/kmem.h> 74 #include <sys/fcntl.h> 75 #include <sys/file.h> 76 #include <sys/filedesc.h> 77 #include <sys/kauth.h> 78 #include <sys/module.h> 79 #include <sys/mount.h> 80 #include <sys/syscall.h> 81 #include <sys/syscallargs.h> 82 #include <sys/syscallvar.h> 83 84 MODULE(MODULE_CLASS_MISC, ksem, NULL); 85 86 #define SEM_MAX_NAMELEN 14 87 #define SEM_VALUE_MAX (~0U) 88 89 #define KS_UNLINKED 0x01 90 91 typedef struct ksem { 92 LIST_ENTRY(ksem) ks_entry; /* global list entry */ 93 kmutex_t ks_lock; /* lock on this ksem */ 94 kcondvar_t ks_cv; /* condition variable */ 95 u_int ks_ref; /* number of references */ 96 u_int ks_value; /* current value */ 97 u_int ks_waiters; /* number of waiters */ 98 char * ks_name; /* name, if named */ 99 size_t ks_namelen; /* length of name */ 100 int ks_flags; /* for KS_UNLINKED */ 101 mode_t ks_mode; /* protection bits */ 102 uid_t ks_uid; /* creator uid */ 103 gid_t ks_gid; /* creator gid */ 104 } ksem_t; 105 106 static kmutex_t ksem_lock __cacheline_aligned; 107 static LIST_HEAD(,ksem) ksem_head __cacheline_aligned; 108 static u_int nsems_total __cacheline_aligned; 109 static u_int nsems __cacheline_aligned; 110 111 static int ksem_sysinit(void); 112 static int ksem_sysfini(bool); 113 static int ksem_modcmd(modcmd_t, void *); 114 static int ksem_close_fop(file_t *); 115 116 static const struct fileops semops = { 117 .fo_read = fbadop_read, 118 .fo_write = fbadop_write, 119 .fo_ioctl = fbadop_ioctl, 120 .fo_fcntl = fnullop_fcntl, 121 .fo_poll = fnullop_poll, 122 .fo_stat = fbadop_stat, 123 .fo_close = ksem_close_fop, 124 .fo_kqfilter = fnullop_kqfilter, 125 .fo_restart = fnullop_restart, 126 }; 127 128 static const struct syscall_package ksem_syscalls[] = { 129 { SYS__ksem_init, 0, (sy_call_t *)sys__ksem_init }, 130 { SYS__ksem_open, 0, (sy_call_t *)sys__ksem_open }, 131 { SYS__ksem_unlink, 0, (sy_call_t *)sys__ksem_unlink }, 132 { SYS__ksem_close, 0, (sy_call_t *)sys__ksem_close }, 133 { SYS__ksem_post, 0, (sy_call_t *)sys__ksem_post }, 134 { SYS__ksem_wait, 0, (sy_call_t *)sys__ksem_wait }, 135 { SYS__ksem_trywait, 0, (sy_call_t *)sys__ksem_trywait }, 136 { SYS__ksem_getvalue, 0, (sy_call_t *)sys__ksem_getvalue }, 137 { SYS__ksem_destroy, 0, (sy_call_t *)sys__ksem_destroy }, 138 { 0, 0, NULL }, 139 }; 140 141 static int 142 ksem_sysinit(void) 143 { 144 int error; 145 146 mutex_init(&ksem_lock, MUTEX_DEFAULT, IPL_NONE); 147 LIST_INIT(&ksem_head); 148 nsems_total = 0; 149 nsems = 0; 150 151 error = syscall_establish(NULL, ksem_syscalls); 152 if (error) { 153 (void)ksem_sysfini(false); 154 } 155 return error; 156 } 157 158 static int 159 ksem_sysfini(bool interface) 160 { 161 int error; 162 163 if (interface) { 164 error = syscall_disestablish(NULL, ksem_syscalls); 165 if (error != 0) { 166 return error; 167 } 168 /* 169 * Make sure that no semaphores are in use. Note: semops 170 * must be unused at this point. 171 */ 172 if (nsems_total) { 173 error = syscall_establish(NULL, ksem_syscalls); 174 KASSERT(error == 0); 175 return EBUSY; 176 } 177 } 178 mutex_destroy(&ksem_lock); 179 return 0; 180 } 181 182 static int 183 ksem_modcmd(modcmd_t cmd, void *arg) 184 { 185 186 switch (cmd) { 187 case MODULE_CMD_INIT: 188 return ksem_sysinit(); 189 190 case MODULE_CMD_FINI: 191 return ksem_sysfini(true); 192 193 default: 194 return ENOTTY; 195 } 196 } 197 198 static ksem_t * 199 ksem_lookup(const char *name) 200 { 201 ksem_t *ks; 202 203 KASSERT(mutex_owned(&ksem_lock)); 204 205 LIST_FOREACH(ks, &ksem_head, ks_entry) { 206 if (strcmp(ks->ks_name, name) == 0) { 207 mutex_enter(&ks->ks_lock); 208 return ks; 209 } 210 } 211 return NULL; 212 } 213 214 static int 215 ksem_perm(lwp_t *l, ksem_t *ks) 216 { 217 kauth_cred_t uc = l->l_cred; 218 mode_t mode = ks->ks_mode; 219 220 KASSERT(mutex_owned(&ks->ks_lock)); 221 if ((kauth_cred_geteuid(uc) == ks->ks_uid && (mode & S_IWUSR) != 0) || 222 (kauth_cred_getegid(uc) == ks->ks_gid && (mode & S_IWGRP) != 0) || 223 (mode & S_IWOTH) != 0 || 224 kauth_authorize_generic(uc, KAUTH_GENERIC_ISSUSER, NULL) == 0) 225 return 0; 226 227 return EACCES; 228 } 229 230 /* 231 * ksem_get: get the semaphore from the descriptor. 232 * 233 * => locks the semaphore, if found. 234 * => holds a reference on the file descriptor. 235 */ 236 static int 237 ksem_get(int fd, ksem_t **ksret) 238 { 239 ksem_t *ks; 240 file_t *fp; 241 242 fp = fd_getfile(fd); 243 if (__predict_false(fp == NULL)) { 244 return EBADF; 245 } 246 if (__predict_false(fp->f_type != DTYPE_SEM)) { 247 fd_putfile(fd); 248 return EBADF; 249 } 250 ks = fp->f_data; 251 mutex_enter(&ks->ks_lock); 252 253 *ksret = ks; 254 return 0; 255 } 256 257 /* 258 * ksem_create: allocate and setup a new semaphore structure. 259 */ 260 static int 261 ksem_create(lwp_t *l, const char *name, ksem_t **ksret, mode_t mode, u_int val) 262 { 263 ksem_t *ks; 264 kauth_cred_t uc; 265 char *kname; 266 size_t len; 267 268 /* Pre-check for the limit. */ 269 if (nsems >= ksem_max) { 270 return ENFILE; 271 } 272 273 if (val > SEM_VALUE_MAX) { 274 return EINVAL; 275 } 276 277 if (name != NULL) { 278 len = strlen(name); 279 if (len > SEM_MAX_NAMELEN) { 280 return ENAMETOOLONG; 281 } 282 /* Name must start with a '/' but not contain one. */ 283 if (*name != '/' || len < 2 || strchr(name + 1, '/') != NULL) { 284 return EINVAL; 285 } 286 kname = kmem_alloc(++len, KM_SLEEP); 287 strlcpy(kname, name, len); 288 } else { 289 kname = NULL; 290 len = 0; 291 } 292 293 ks = kmem_zalloc(sizeof(ksem_t), KM_SLEEP); 294 mutex_init(&ks->ks_lock, MUTEX_DEFAULT, IPL_NONE); 295 cv_init(&ks->ks_cv, "psem"); 296 ks->ks_name = kname; 297 ks->ks_namelen = len; 298 ks->ks_mode = mode; 299 ks->ks_value = val; 300 ks->ks_ref = 1; 301 302 uc = l->l_cred; 303 ks->ks_uid = kauth_cred_geteuid(uc); 304 ks->ks_gid = kauth_cred_getegid(uc); 305 306 atomic_inc_uint(&nsems_total); 307 *ksret = ks; 308 return 0; 309 } 310 311 static void 312 ksem_free(ksem_t *ks) 313 { 314 315 KASSERT(ks->ks_ref == 0); 316 KASSERT(!cv_has_waiters(&ks->ks_cv)); 317 318 if (ks->ks_name) { 319 KASSERT(ks->ks_namelen > 0); 320 kmem_free(ks->ks_name, ks->ks_namelen); 321 } 322 mutex_destroy(&ks->ks_lock); 323 cv_destroy(&ks->ks_cv); 324 kmem_free(ks, sizeof(ksem_t)); 325 326 atomic_dec_uint(&nsems_total); 327 } 328 329 int 330 sys__ksem_init(struct lwp *l, const struct sys__ksem_init_args *uap, 331 register_t *retval) 332 { 333 /* { 334 unsigned int value; 335 intptr_t *idp; 336 } */ 337 338 return do_ksem_init(l, SCARG(uap, value), SCARG(uap, idp), copyout); 339 } 340 341 int 342 do_ksem_init(lwp_t *l, u_int val, intptr_t *idp, copyout_t docopyout) 343 { 344 proc_t *p = l->l_proc; 345 ksem_t *ks; 346 file_t *fp; 347 intptr_t id; 348 int fd, error; 349 350 error = fd_allocfile(&fp, &fd); 351 if (error) { 352 return error; 353 } 354 fp->f_type = DTYPE_SEM; 355 fp->f_flag = FREAD | FWRITE; 356 fp->f_ops = &semops; 357 358 id = (intptr_t)fd; 359 error = (*docopyout)(&id, idp, sizeof(*idp)); 360 if (error) { 361 fd_abort(p, fp, fd); 362 return error; 363 } 364 365 /* Note the mode does not matter for anonymous semaphores. */ 366 error = ksem_create(l, NULL, &ks, 0, val); 367 if (error) { 368 fd_abort(p, fp, fd); 369 return error; 370 } 371 fp->f_data = ks; 372 fd_affix(p, fp, fd); 373 return error; 374 } 375 376 int 377 sys__ksem_open(struct lwp *l, const struct sys__ksem_open_args *uap, 378 register_t *retval) 379 { 380 /* { 381 const char *name; 382 int oflag; 383 mode_t mode; 384 unsigned int value; 385 intptr_t *idp; 386 } */ 387 388 return do_ksem_open(l, SCARG(uap, name), SCARG(uap, oflag), 389 SCARG(uap, mode), SCARG(uap, value), SCARG(uap, idp), copyout); 390 } 391 392 int 393 do_ksem_open(struct lwp *l, const char *semname, int oflag, mode_t mode, 394 unsigned int value, intptr_t *idp, copyout_t docopyout) 395 { 396 char name[SEM_MAX_NAMELEN + 1]; 397 proc_t *p = l->l_proc; 398 ksem_t *ksnew = NULL, *ks; 399 file_t *fp; 400 intptr_t id; 401 int fd, error; 402 403 error = copyinstr(semname, name, sizeof(name), NULL); 404 if (error) { 405 return error; 406 } 407 error = fd_allocfile(&fp, &fd); 408 if (error) { 409 return error; 410 } 411 fp->f_type = DTYPE_SEM; 412 fp->f_flag = FREAD | FWRITE; 413 fp->f_ops = &semops; 414 415 /* 416 * The ID (file descriptor number) can be stored early. 417 * Note that zero is a special value for libpthread. 418 */ 419 id = (intptr_t)fd; 420 error = (*docopyout)(&id, idp, sizeof(*idp)); 421 if (error) { 422 goto err; 423 } 424 425 if (oflag & O_CREAT) { 426 /* Create a new semaphore. */ 427 error = ksem_create(l, name, &ksnew, mode, value); 428 if (error) { 429 goto err; 430 } 431 KASSERT(ksnew != NULL); 432 } 433 434 /* Lookup for a semaphore with such name. */ 435 mutex_enter(&ksem_lock); 436 ks = ksem_lookup(name); 437 if (ks) { 438 KASSERT(mutex_owned(&ks->ks_lock)); 439 mutex_exit(&ksem_lock); 440 441 /* Check for exclusive create. */ 442 if (oflag & O_EXCL) { 443 mutex_exit(&ks->ks_lock); 444 error = EEXIST; 445 goto err; 446 } 447 /* 448 * Verify permissions. If we can access it, 449 * add the reference of this thread. 450 */ 451 error = ksem_perm(l, ks); 452 if (error == 0) { 453 ks->ks_ref++; 454 } 455 mutex_exit(&ks->ks_lock); 456 if (error) { 457 goto err; 458 } 459 } else { 460 /* Fail if not found and not creating. */ 461 if ((oflag & O_CREAT) == 0) { 462 mutex_exit(&ksem_lock); 463 KASSERT(ksnew == NULL); 464 error = ENOENT; 465 goto err; 466 } 467 468 /* Check for the limit locked. */ 469 if (nsems >= ksem_max) { 470 mutex_exit(&ksem_lock); 471 error = ENFILE; 472 goto err; 473 } 474 475 /* 476 * Finally, insert semaphore into the list. 477 * Note: it already has the initial reference. 478 */ 479 ks = ksnew; 480 LIST_INSERT_HEAD(&ksem_head, ks, ks_entry); 481 nsems++; 482 mutex_exit(&ksem_lock); 483 484 ksnew = NULL; 485 } 486 KASSERT(ks != NULL); 487 fp->f_data = ks; 488 fd_affix(p, fp, fd); 489 err: 490 if (error) { 491 fd_abort(p, fp, fd); 492 } 493 if (ksnew) { 494 ksem_free(ksnew); 495 } 496 return error; 497 } 498 499 int 500 sys__ksem_close(struct lwp *l, const struct sys__ksem_close_args *uap, 501 register_t *retval) 502 { 503 /* { 504 intptr_t id; 505 } */ 506 int fd = (int)SCARG(uap, id); 507 508 if (fd_getfile(fd) == NULL) { 509 return EBADF; 510 } 511 return fd_close(fd); 512 } 513 514 static int 515 ksem_close_fop(file_t *fp) 516 { 517 ksem_t *ks = fp->f_data; 518 bool destroy = false; 519 520 mutex_enter(&ks->ks_lock); 521 KASSERT(ks->ks_ref > 0); 522 if (--ks->ks_ref == 0) { 523 /* 524 * Destroy if the last reference and semaphore is unnamed, 525 * or unlinked (for named semaphore). 526 */ 527 destroy = (ks->ks_flags & KS_UNLINKED) || (ks->ks_name == NULL); 528 } 529 mutex_exit(&ks->ks_lock); 530 531 if (destroy) { 532 ksem_free(ks); 533 } 534 return 0; 535 } 536 537 int 538 sys__ksem_unlink(struct lwp *l, const struct sys__ksem_unlink_args *uap, 539 register_t *retval) 540 { 541 /* { 542 const char *name; 543 } */ 544 char name[SEM_MAX_NAMELEN + 1]; 545 ksem_t *ks; 546 u_int refcnt; 547 int error; 548 549 error = copyinstr(SCARG(uap, name), name, sizeof(name), NULL); 550 if (error) 551 return error; 552 553 mutex_enter(&ksem_lock); 554 ks = ksem_lookup(name); 555 if (ks == NULL) { 556 mutex_exit(&ksem_lock); 557 return ENOENT; 558 } 559 KASSERT(mutex_owned(&ks->ks_lock)); 560 561 /* Verify permissions. */ 562 error = ksem_perm(l, ks); 563 if (error) { 564 mutex_exit(&ks->ks_lock); 565 mutex_exit(&ksem_lock); 566 return error; 567 } 568 569 /* Remove from the global list. */ 570 LIST_REMOVE(ks, ks_entry); 571 nsems--; 572 mutex_exit(&ksem_lock); 573 574 refcnt = ks->ks_ref; 575 if (refcnt) { 576 /* Mark as unlinked, if there are references. */ 577 ks->ks_flags |= KS_UNLINKED; 578 } 579 mutex_exit(&ks->ks_lock); 580 581 if (refcnt == 0) { 582 ksem_free(ks); 583 } 584 return 0; 585 } 586 587 int 588 sys__ksem_post(struct lwp *l, const struct sys__ksem_post_args *uap, 589 register_t *retval) 590 { 591 /* { 592 intptr_t id; 593 } */ 594 int fd = (int)SCARG(uap, id), error; 595 ksem_t *ks; 596 597 error = ksem_get(fd, &ks); 598 if (error) { 599 return error; 600 } 601 KASSERT(mutex_owned(&ks->ks_lock)); 602 if (ks->ks_value == SEM_VALUE_MAX) { 603 error = EOVERFLOW; 604 goto out; 605 } 606 ks->ks_value++; 607 if (ks->ks_waiters) { 608 cv_broadcast(&ks->ks_cv); 609 } 610 out: 611 mutex_exit(&ks->ks_lock); 612 fd_putfile(fd); 613 return error; 614 } 615 616 static int 617 ksem_wait(lwp_t *l, intptr_t id, bool try) 618 { 619 int fd = (int)id, error; 620 ksem_t *ks; 621 622 error = ksem_get(fd, &ks); 623 if (error) { 624 return error; 625 } 626 KASSERT(mutex_owned(&ks->ks_lock)); 627 while (ks->ks_value == 0) { 628 ks->ks_waiters++; 629 error = try ? EAGAIN : cv_wait_sig(&ks->ks_cv, &ks->ks_lock); 630 ks->ks_waiters--; 631 if (error) 632 goto out; 633 } 634 ks->ks_value--; 635 out: 636 mutex_exit(&ks->ks_lock); 637 fd_putfile(fd); 638 return error; 639 } 640 641 int 642 sys__ksem_wait(struct lwp *l, const struct sys__ksem_wait_args *uap, 643 register_t *retval) 644 { 645 /* { 646 intptr_t id; 647 } */ 648 649 return ksem_wait(l, SCARG(uap, id), false); 650 } 651 652 int 653 sys__ksem_trywait(struct lwp *l, const struct sys__ksem_trywait_args *uap, 654 register_t *retval) 655 { 656 /* { 657 intptr_t id; 658 } */ 659 660 return ksem_wait(l, SCARG(uap, id), true); 661 } 662 663 int 664 sys__ksem_getvalue(struct lwp *l, const struct sys__ksem_getvalue_args *uap, 665 register_t *retval) 666 { 667 /* { 668 intptr_t id; 669 unsigned int *value; 670 } */ 671 int fd = (int)SCARG(uap, id), error; 672 ksem_t *ks; 673 unsigned int val; 674 675 error = ksem_get(fd, &ks); 676 if (error) { 677 return error; 678 } 679 KASSERT(mutex_owned(&ks->ks_lock)); 680 val = ks->ks_value; 681 mutex_exit(&ks->ks_lock); 682 fd_putfile(fd); 683 684 return copyout(&val, SCARG(uap, value), sizeof(val)); 685 } 686 687 int 688 sys__ksem_destroy(struct lwp *l, const struct sys__ksem_destroy_args *uap, 689 register_t *retval) 690 { 691 /* { 692 intptr_t id; 693 } */ 694 int fd = (int)SCARG(uap, id), error; 695 ksem_t *ks; 696 697 error = ksem_get(fd, &ks); 698 if (error) { 699 return error; 700 } 701 KASSERT(mutex_owned(&ks->ks_lock)); 702 703 /* Operation is only for unnamed semaphores. */ 704 if (ks->ks_name != NULL) { 705 error = EINVAL; 706 goto out; 707 } 708 /* Cannot destroy if there are waiters. */ 709 if (ks->ks_waiters) { 710 error = EBUSY; 711 goto out; 712 } 713 out: 714 mutex_exit(&ks->ks_lock); 715 if (error) { 716 fd_putfile(fd); 717 return error; 718 } 719 return fd_close(fd); 720 } 721
Indexes created Fri Sep 26 20:09:58 GMT 2025