Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_shm.c
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1 /*- 2 * Copyright (c) 2006, 2011 Robert N. M. Watson 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 /* 28 * Support for shared swap-backed anonymous memory objects via 29 * shm_open(2) and shm_unlink(2). While most of the implementation is 30 * here, vm_mmap.c contains mapping logic changes. 31 * 32 * TODO: 33 * 34 * (1) Need to export data to a userland tool via a sysctl. Should ipcs(1) 35 * and ipcrm(1) be expanded or should new tools to manage both POSIX 36 * kernel semaphores and POSIX shared memory be written? 37 * 38 * (2) Add support for this file type to fstat(1). 39 * 40 * (3) Resource limits? Does this need its own resource limits or are the 41 * existing limits in mmap(2) sufficient? 42 */ 43 44 #include <sys/cdefs.h> 45 __FBSDID("$FreeBSD: releng/10.0/sys/kern/uipc_shm.c 255467 2013-09-11 06:41:15Z kib $"); 46 47 #include "opt_capsicum.h" 48 49 #include <sys/param.h> 50 #include <sys/capability.h> 51 #include <sys/fcntl.h> 52 #include <sys/file.h> 53 #include <sys/filedesc.h> 54 #include <sys/fnv_hash.h> 55 #include <sys/kernel.h> 56 #include <sys/lock.h> 57 #include <sys/malloc.h> 58 #include <sys/mman.h> 59 #include <sys/mutex.h> 60 #include <sys/priv.h> 61 #include <sys/proc.h> 62 #include <sys/refcount.h> 63 #include <sys/resourcevar.h> 64 #include <sys/rwlock.h> 65 #include <sys/stat.h> 66 #include <sys/sysctl.h> 67 #include <sys/sysproto.h> 68 #include <sys/systm.h> 69 #include <sys/sx.h> 70 #include <sys/time.h> 71 #include <sys/vnode.h> 72 #include <sys/unistd.h> 73 74 #include <security/mac/mac_framework.h> 75 76 #include <vm/vm.h> 77 #include <vm/vm_param.h> 78 #include <vm/pmap.h> 79 #include <vm/vm_extern.h> 80 #include <vm/vm_map.h> 81 #include <vm/vm_kern.h> 82 #include <vm/vm_object.h> 83 #include <vm/vm_page.h> 84 #include <vm/vm_pageout.h> 85 #include <vm/vm_pager.h> 86 #include <vm/swap_pager.h> 87 88 struct shm_mapping { 89 char *sm_path; 90 Fnv32_t sm_fnv; 91 struct shmfd *sm_shmfd; 92 LIST_ENTRY(shm_mapping) sm_link; 93 }; 94 95 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 96 static LIST_HEAD(, shm_mapping) *shm_dictionary; 97 static struct sx shm_dict_lock; 98 static struct mtx shm_timestamp_lock; 99 static u_long shm_hash; 100 101 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 102 103 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 104 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 105 static void shm_dict_init(void *arg); 106 static void shm_drop(struct shmfd *shmfd); 107 static struct shmfd *shm_hold(struct shmfd *shmfd); 108 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 109 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 110 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 111 static int shm_dotruncate(struct shmfd *shmfd, off_t length); 112 113 static fo_rdwr_t shm_read; 114 static fo_rdwr_t shm_write; 115 static fo_truncate_t shm_truncate; 116 static fo_ioctl_t shm_ioctl; 117 static fo_poll_t shm_poll; 118 static fo_kqfilter_t shm_kqfilter; 119 static fo_stat_t shm_stat; 120 static fo_close_t shm_close; 121 static fo_chmod_t shm_chmod; 122 static fo_chown_t shm_chown; 123 static fo_seek_t shm_seek; 124 125 /* File descriptor operations. */ 126 static struct fileops shm_ops = { 127 .fo_read = shm_read, 128 .fo_write = shm_write, 129 .fo_truncate = shm_truncate, 130 .fo_ioctl = shm_ioctl, 131 .fo_poll = shm_poll, 132 .fo_kqfilter = shm_kqfilter, 133 .fo_stat = shm_stat, 134 .fo_close = shm_close, 135 .fo_chmod = shm_chmod, 136 .fo_chown = shm_chown, 137 .fo_sendfile = vn_sendfile, 138 .fo_seek = shm_seek, 139 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE 140 }; 141 142 FEATURE(posix_shm, "POSIX shared memory"); 143 144 static int 145 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio) 146 { 147 vm_page_t m; 148 vm_pindex_t idx; 149 size_t tlen; 150 int error, offset, rv; 151 152 idx = OFF_TO_IDX(uio->uio_offset); 153 offset = uio->uio_offset & PAGE_MASK; 154 tlen = MIN(PAGE_SIZE - offset, len); 155 156 VM_OBJECT_WLOCK(obj); 157 158 /* 159 * Parallel reads of the page content from disk are prevented 160 * by exclusive busy. 161 * 162 * Although the tmpfs vnode lock is held here, it is 163 * nonetheless safe to sleep waiting for a free page. The 164 * pageout daemon does not need to acquire the tmpfs vnode 165 * lock to page out tobj's pages because tobj is a OBJT_SWAP 166 * type object. 167 */ 168 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL); 169 if (m->valid != VM_PAGE_BITS_ALL) { 170 if (vm_pager_has_page(obj, idx, NULL, NULL)) { 171 rv = vm_pager_get_pages(obj, &m, 1, 0); 172 m = vm_page_lookup(obj, idx); 173 if (m == NULL) { 174 printf( 175 "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n", 176 obj, idx, rv); 177 VM_OBJECT_WUNLOCK(obj); 178 return (EIO); 179 } 180 if (rv != VM_PAGER_OK) { 181 printf( 182 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n", 183 obj, idx, m->valid, rv); 184 vm_page_lock(m); 185 vm_page_free(m); 186 vm_page_unlock(m); 187 VM_OBJECT_WUNLOCK(obj); 188 return (EIO); 189 } 190 } else 191 vm_page_zero_invalid(m, TRUE); 192 } 193 vm_page_xunbusy(m); 194 vm_page_lock(m); 195 vm_page_hold(m); 196 vm_page_unlock(m); 197 VM_OBJECT_WUNLOCK(obj); 198 error = uiomove_fromphys(&m, offset, tlen, uio); 199 if (uio->uio_rw == UIO_WRITE && error == 0) { 200 VM_OBJECT_WLOCK(obj); 201 vm_page_dirty(m); 202 VM_OBJECT_WUNLOCK(obj); 203 } 204 vm_page_lock(m); 205 vm_page_unhold(m); 206 if (m->queue == PQ_NONE) { 207 vm_page_deactivate(m); 208 } else { 209 /* Requeue to maintain LRU ordering. */ 210 vm_page_requeue(m); 211 } 212 vm_page_unlock(m); 213 214 return (error); 215 } 216 217 int 218 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio) 219 { 220 ssize_t resid; 221 size_t len; 222 int error; 223 224 error = 0; 225 while ((resid = uio->uio_resid) > 0) { 226 if (obj_size <= uio->uio_offset) 227 break; 228 len = MIN(obj_size - uio->uio_offset, resid); 229 if (len == 0) 230 break; 231 error = uiomove_object_page(obj, len, uio); 232 if (error != 0 || resid == uio->uio_resid) 233 break; 234 } 235 return (error); 236 } 237 238 static int 239 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td) 240 { 241 struct shmfd *shmfd; 242 off_t foffset; 243 int error; 244 245 shmfd = fp->f_data; 246 foffset = foffset_lock(fp, 0); 247 error = 0; 248 switch (whence) { 249 case L_INCR: 250 if (foffset < 0 || 251 (offset > 0 && foffset > OFF_MAX - offset)) { 252 error = EOVERFLOW; 253 break; 254 } 255 offset += foffset; 256 break; 257 case L_XTND: 258 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) { 259 error = EOVERFLOW; 260 break; 261 } 262 offset += shmfd->shm_size; 263 break; 264 case L_SET: 265 break; 266 default: 267 error = EINVAL; 268 } 269 if (error == 0) { 270 if (offset < 0 || offset > shmfd->shm_size) 271 error = EINVAL; 272 else 273 *(off_t *)(td->td_retval) = offset; 274 } 275 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0); 276 return (error); 277 } 278 279 static int 280 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 281 int flags, struct thread *td) 282 { 283 struct shmfd *shmfd; 284 void *rl_cookie; 285 int error; 286 287 shmfd = fp->f_data; 288 foffset_lock_uio(fp, uio, flags); 289 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset, 290 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 291 #ifdef MAC 292 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd); 293 if (error) 294 return (error); 295 #endif 296 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 297 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 298 foffset_unlock_uio(fp, uio, flags); 299 return (error); 300 } 301 302 static int 303 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 304 int flags, struct thread *td) 305 { 306 struct shmfd *shmfd; 307 void *rl_cookie; 308 int error; 309 310 shmfd = fp->f_data; 311 #ifdef MAC 312 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd); 313 if (error) 314 return (error); 315 #endif 316 foffset_lock_uio(fp, uio, flags); 317 if ((flags & FOF_OFFSET) == 0) { 318 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX, 319 &shmfd->shm_mtx); 320 } else { 321 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset, 322 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 323 } 324 325 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 326 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 327 foffset_unlock_uio(fp, uio, flags); 328 return (error); 329 } 330 331 static int 332 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 333 struct thread *td) 334 { 335 struct shmfd *shmfd; 336 #ifdef MAC 337 int error; 338 #endif 339 340 shmfd = fp->f_data; 341 #ifdef MAC 342 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 343 if (error) 344 return (error); 345 #endif 346 return (shm_dotruncate(shmfd, length)); 347 } 348 349 static int 350 shm_ioctl(struct file *fp, u_long com, void *data, 351 struct ucred *active_cred, struct thread *td) 352 { 353 354 return (EOPNOTSUPP); 355 } 356 357 static int 358 shm_poll(struct file *fp, int events, struct ucred *active_cred, 359 struct thread *td) 360 { 361 362 return (EOPNOTSUPP); 363 } 364 365 static int 366 shm_kqfilter(struct file *fp, struct knote *kn) 367 { 368 369 return (EOPNOTSUPP); 370 } 371 372 static int 373 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 374 struct thread *td) 375 { 376 struct shmfd *shmfd; 377 #ifdef MAC 378 int error; 379 #endif 380 381 shmfd = fp->f_data; 382 383 #ifdef MAC 384 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 385 if (error) 386 return (error); 387 #endif 388 389 /* 390 * Attempt to return sanish values for fstat() on a memory file 391 * descriptor. 392 */ 393 bzero(sb, sizeof(*sb)); 394 sb->st_blksize = PAGE_SIZE; 395 sb->st_size = shmfd->shm_size; 396 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 397 mtx_lock(&shm_timestamp_lock); 398 sb->st_atim = shmfd->shm_atime; 399 sb->st_ctim = shmfd->shm_ctime; 400 sb->st_mtim = shmfd->shm_mtime; 401 sb->st_birthtim = shmfd->shm_birthtime; 402 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 403 sb->st_uid = shmfd->shm_uid; 404 sb->st_gid = shmfd->shm_gid; 405 mtx_unlock(&shm_timestamp_lock); 406 407 return (0); 408 } 409 410 static int 411 shm_close(struct file *fp, struct thread *td) 412 { 413 struct shmfd *shmfd; 414 415 shmfd = fp->f_data; 416 fp->f_data = NULL; 417 shm_drop(shmfd); 418 419 return (0); 420 } 421 422 static int 423 shm_dotruncate(struct shmfd *shmfd, off_t length) 424 { 425 vm_object_t object; 426 vm_page_t m, ma[1]; 427 vm_pindex_t idx, nobjsize; 428 vm_ooffset_t delta; 429 int base, rv; 430 431 object = shmfd->shm_object; 432 VM_OBJECT_WLOCK(object); 433 if (length == shmfd->shm_size) { 434 VM_OBJECT_WUNLOCK(object); 435 return (0); 436 } 437 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 438 439 /* Are we shrinking? If so, trim the end. */ 440 if (length < shmfd->shm_size) { 441 /* 442 * Disallow any requests to shrink the size if this 443 * object is mapped into the kernel. 444 */ 445 if (shmfd->shm_kmappings > 0) { 446 VM_OBJECT_WUNLOCK(object); 447 return (EBUSY); 448 } 449 450 /* 451 * Zero the truncated part of the last page. 452 */ 453 base = length & PAGE_MASK; 454 if (base != 0) { 455 idx = OFF_TO_IDX(length); 456 retry: 457 m = vm_page_lookup(object, idx); 458 if (m != NULL) { 459 if (vm_page_sleep_if_busy(m, "shmtrc")) 460 goto retry; 461 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 462 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL); 463 if (m == NULL) { 464 VM_OBJECT_WUNLOCK(object); 465 VM_WAIT; 466 VM_OBJECT_WLOCK(object); 467 goto retry; 468 } else if (m->valid != VM_PAGE_BITS_ALL) { 469 ma[0] = m; 470 rv = vm_pager_get_pages(object, ma, 1, 471 0); 472 m = vm_page_lookup(object, idx); 473 } else 474 /* A cached page was reactivated. */ 475 rv = VM_PAGER_OK; 476 vm_page_lock(m); 477 if (rv == VM_PAGER_OK) { 478 vm_page_deactivate(m); 479 vm_page_unlock(m); 480 vm_page_xunbusy(m); 481 } else { 482 vm_page_free(m); 483 vm_page_unlock(m); 484 VM_OBJECT_WUNLOCK(object); 485 return (EIO); 486 } 487 } 488 if (m != NULL) { 489 pmap_zero_page_area(m, base, PAGE_SIZE - base); 490 KASSERT(m->valid == VM_PAGE_BITS_ALL, 491 ("shm_dotruncate: page %p is invalid", m)); 492 vm_page_dirty(m); 493 vm_pager_page_unswapped(m); 494 } 495 } 496 delta = ptoa(object->size - nobjsize); 497 498 /* Toss in memory pages. */ 499 if (nobjsize < object->size) 500 vm_object_page_remove(object, nobjsize, object->size, 501 0); 502 503 /* Toss pages from swap. */ 504 if (object->type == OBJT_SWAP) 505 swap_pager_freespace(object, nobjsize, delta); 506 507 /* Free the swap accounted for shm */ 508 swap_release_by_cred(delta, object->cred); 509 object->charge -= delta; 510 } else { 511 /* Attempt to reserve the swap */ 512 delta = ptoa(nobjsize - object->size); 513 if (!swap_reserve_by_cred(delta, object->cred)) { 514 VM_OBJECT_WUNLOCK(object); 515 return (ENOMEM); 516 } 517 object->charge += delta; 518 } 519 shmfd->shm_size = length; 520 mtx_lock(&shm_timestamp_lock); 521 vfs_timestamp(&shmfd->shm_ctime); 522 shmfd->shm_mtime = shmfd->shm_ctime; 523 mtx_unlock(&shm_timestamp_lock); 524 object->size = nobjsize; 525 VM_OBJECT_WUNLOCK(object); 526 return (0); 527 } 528 529 /* 530 * shmfd object management including creation and reference counting 531 * routines. 532 */ 533 static struct shmfd * 534 shm_alloc(struct ucred *ucred, mode_t mode) 535 { 536 struct shmfd *shmfd; 537 538 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 539 shmfd->shm_size = 0; 540 shmfd->shm_uid = ucred->cr_uid; 541 shmfd->shm_gid = ucred->cr_gid; 542 shmfd->shm_mode = mode; 543 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 544 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 545 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 546 VM_OBJECT_WLOCK(shmfd->shm_object); 547 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 548 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 549 VM_OBJECT_WUNLOCK(shmfd->shm_object); 550 vfs_timestamp(&shmfd->shm_birthtime); 551 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 552 shmfd->shm_birthtime; 553 refcount_init(&shmfd->shm_refs, 1); 554 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF); 555 rangelock_init(&shmfd->shm_rl); 556 #ifdef MAC 557 mac_posixshm_init(shmfd); 558 mac_posixshm_create(ucred, shmfd); 559 #endif 560 561 return (shmfd); 562 } 563 564 static struct shmfd * 565 shm_hold(struct shmfd *shmfd) 566 { 567 568 refcount_acquire(&shmfd->shm_refs); 569 return (shmfd); 570 } 571 572 static void 573 shm_drop(struct shmfd *shmfd) 574 { 575 576 if (refcount_release(&shmfd->shm_refs)) { 577 #ifdef MAC 578 mac_posixshm_destroy(shmfd); 579 #endif 580 rangelock_destroy(&shmfd->shm_rl); 581 mtx_destroy(&shmfd->shm_mtx); 582 vm_object_deallocate(shmfd->shm_object); 583 free(shmfd, M_SHMFD); 584 } 585 } 586 587 /* 588 * Determine if the credentials have sufficient permissions for a 589 * specified combination of FREAD and FWRITE. 590 */ 591 static int 592 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 593 { 594 accmode_t accmode; 595 int error; 596 597 accmode = 0; 598 if (flags & FREAD) 599 accmode |= VREAD; 600 if (flags & FWRITE) 601 accmode |= VWRITE; 602 mtx_lock(&shm_timestamp_lock); 603 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 604 accmode, ucred, NULL); 605 mtx_unlock(&shm_timestamp_lock); 606 return (error); 607 } 608 609 /* 610 * Dictionary management. We maintain an in-kernel dictionary to map 611 * paths to shmfd objects. We use the FNV hash on the path to store 612 * the mappings in a hash table. 613 */ 614 static void 615 shm_dict_init(void *arg) 616 { 617 618 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 619 sx_init(&shm_dict_lock, "shm dictionary"); 620 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 621 } 622 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 623 624 static struct shmfd * 625 shm_lookup(char *path, Fnv32_t fnv) 626 { 627 struct shm_mapping *map; 628 629 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 630 if (map->sm_fnv != fnv) 631 continue; 632 if (strcmp(map->sm_path, path) == 0) 633 return (map->sm_shmfd); 634 } 635 636 return (NULL); 637 } 638 639 static void 640 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 641 { 642 struct shm_mapping *map; 643 644 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 645 map->sm_path = path; 646 map->sm_fnv = fnv; 647 map->sm_shmfd = shm_hold(shmfd); 648 shmfd->shm_path = path; 649 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 650 } 651 652 static int 653 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 654 { 655 struct shm_mapping *map; 656 int error; 657 658 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 659 if (map->sm_fnv != fnv) 660 continue; 661 if (strcmp(map->sm_path, path) == 0) { 662 #ifdef MAC 663 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 664 if (error) 665 return (error); 666 #endif 667 error = shm_access(map->sm_shmfd, ucred, 668 FREAD | FWRITE); 669 if (error) 670 return (error); 671 map->sm_shmfd->shm_path = NULL; 672 LIST_REMOVE(map, sm_link); 673 shm_drop(map->sm_shmfd); 674 free(map->sm_path, M_SHMFD); 675 free(map, M_SHMFD); 676 return (0); 677 } 678 } 679 680 return (ENOENT); 681 } 682 683 /* System calls. */ 684 int 685 sys_shm_open(struct thread *td, struct shm_open_args *uap) 686 { 687 struct filedesc *fdp; 688 struct shmfd *shmfd; 689 struct file *fp; 690 char *path; 691 Fnv32_t fnv; 692 mode_t cmode; 693 int fd, error; 694 695 #ifdef CAPABILITY_MODE 696 /* 697 * shm_open(2) is only allowed for anonymous objects. 698 */ 699 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON)) 700 return (ECAPMODE); 701 #endif 702 703 if ((uap->flags & O_ACCMODE) != O_RDONLY && 704 (uap->flags & O_ACCMODE) != O_RDWR) 705 return (EINVAL); 706 707 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 708 return (EINVAL); 709 710 fdp = td->td_proc->p_fd; 711 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 712 713 error = falloc(td, &fp, &fd, O_CLOEXEC); 714 if (error) 715 return (error); 716 717 /* A SHM_ANON path pointer creates an anonymous object. */ 718 if (uap->path == SHM_ANON) { 719 /* A read-only anonymous object is pointless. */ 720 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 721 fdclose(fdp, fp, fd, td); 722 fdrop(fp, td); 723 return (EINVAL); 724 } 725 shmfd = shm_alloc(td->td_ucred, cmode); 726 } else { 727 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 728 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 729 730 /* Require paths to start with a '/' character. */ 731 if (error == 0 && path[0] != '/') 732 error = EINVAL; 733 if (error) { 734 fdclose(fdp, fp, fd, td); 735 fdrop(fp, td); 736 free(path, M_SHMFD); 737 return (error); 738 } 739 740 fnv = fnv_32_str(path, FNV1_32_INIT); 741 sx_xlock(&shm_dict_lock); 742 shmfd = shm_lookup(path, fnv); 743 if (shmfd == NULL) { 744 /* Object does not yet exist, create it if requested. */ 745 if (uap->flags & O_CREAT) { 746 #ifdef MAC 747 error = mac_posixshm_check_create(td->td_ucred, 748 path); 749 if (error == 0) { 750 #endif 751 shmfd = shm_alloc(td->td_ucred, cmode); 752 shm_insert(path, fnv, shmfd); 753 #ifdef MAC 754 } 755 #endif 756 } else { 757 free(path, M_SHMFD); 758 error = ENOENT; 759 } 760 } else { 761 /* 762 * Object already exists, obtain a new 763 * reference if requested and permitted. 764 */ 765 free(path, M_SHMFD); 766 if ((uap->flags & (O_CREAT | O_EXCL)) == 767 (O_CREAT | O_EXCL)) 768 error = EEXIST; 769 else { 770 #ifdef MAC 771 error = mac_posixshm_check_open(td->td_ucred, 772 shmfd, FFLAGS(uap->flags & O_ACCMODE)); 773 if (error == 0) 774 #endif 775 error = shm_access(shmfd, td->td_ucred, 776 FFLAGS(uap->flags & O_ACCMODE)); 777 } 778 779 /* 780 * Truncate the file back to zero length if 781 * O_TRUNC was specified and the object was 782 * opened with read/write. 783 */ 784 if (error == 0 && 785 (uap->flags & (O_ACCMODE | O_TRUNC)) == 786 (O_RDWR | O_TRUNC)) { 787 #ifdef MAC 788 error = mac_posixshm_check_truncate( 789 td->td_ucred, fp->f_cred, shmfd); 790 if (error == 0) 791 #endif 792 shm_dotruncate(shmfd, 0); 793 } 794 if (error == 0) 795 shm_hold(shmfd); 796 } 797 sx_xunlock(&shm_dict_lock); 798 799 if (error) { 800 fdclose(fdp, fp, fd, td); 801 fdrop(fp, td); 802 return (error); 803 } 804 } 805 806 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 807 808 td->td_retval[0] = fd; 809 fdrop(fp, td); 810 811 return (0); 812 } 813 814 int 815 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 816 { 817 char *path; 818 Fnv32_t fnv; 819 int error; 820 821 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 822 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 823 if (error) { 824 free(path, M_TEMP); 825 return (error); 826 } 827 828 fnv = fnv_32_str(path, FNV1_32_INIT); 829 sx_xlock(&shm_dict_lock); 830 error = shm_remove(path, fnv, td->td_ucred); 831 sx_xunlock(&shm_dict_lock); 832 free(path, M_TEMP); 833 834 return (error); 835 } 836 837 /* 838 * mmap() helper to validate mmap() requests against shm object state 839 * and give mmap() the vm_object to use for the mapping. 840 */ 841 int 842 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 843 vm_object_t *obj) 844 { 845 846 /* 847 * XXXRW: This validation is probably insufficient, and subject to 848 * sign errors. It should be fixed. 849 */ 850 if (foff >= shmfd->shm_size || 851 foff + objsize > round_page(shmfd->shm_size)) 852 return (EINVAL); 853 854 mtx_lock(&shm_timestamp_lock); 855 vfs_timestamp(&shmfd->shm_atime); 856 mtx_unlock(&shm_timestamp_lock); 857 vm_object_reference(shmfd->shm_object); 858 *obj = shmfd->shm_object; 859 return (0); 860 } 861 862 static int 863 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 864 struct thread *td) 865 { 866 struct shmfd *shmfd; 867 int error; 868 869 error = 0; 870 shmfd = fp->f_data; 871 mtx_lock(&shm_timestamp_lock); 872 /* 873 * SUSv4 says that x bits of permission need not be affected. 874 * Be consistent with our shm_open there. 875 */ 876 #ifdef MAC 877 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 878 if (error != 0) 879 goto out; 880 #endif 881 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 882 shmfd->shm_gid, VADMIN, active_cred, NULL); 883 if (error != 0) 884 goto out; 885 shmfd->shm_mode = mode & ACCESSPERMS; 886 out: 887 mtx_unlock(&shm_timestamp_lock); 888 return (error); 889 } 890 891 static int 892 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 893 struct thread *td) 894 { 895 struct shmfd *shmfd; 896 int error; 897 898 error = 0; 899 shmfd = fp->f_data; 900 mtx_lock(&shm_timestamp_lock); 901 #ifdef MAC 902 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 903 if (error != 0) 904 goto out; 905 #endif 906 if (uid == (uid_t)-1) 907 uid = shmfd->shm_uid; 908 if (gid == (gid_t)-1) 909 gid = shmfd->shm_gid; 910 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 911 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 912 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 913 goto out; 914 shmfd->shm_uid = uid; 915 shmfd->shm_gid = gid; 916 out: 917 mtx_unlock(&shm_timestamp_lock); 918 return (error); 919 } 920 921 /* 922 * Helper routines to allow the backing object of a shared memory file 923 * descriptor to be mapped in the kernel. 924 */ 925 int 926 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 927 { 928 struct shmfd *shmfd; 929 vm_offset_t kva, ofs; 930 vm_object_t obj; 931 int rv; 932 933 if (fp->f_type != DTYPE_SHM) 934 return (EINVAL); 935 shmfd = fp->f_data; 936 obj = shmfd->shm_object; 937 VM_OBJECT_WLOCK(obj); 938 /* 939 * XXXRW: This validation is probably insufficient, and subject to 940 * sign errors. It should be fixed. 941 */ 942 if (offset >= shmfd->shm_size || 943 offset + size > round_page(shmfd->shm_size)) { 944 VM_OBJECT_WUNLOCK(obj); 945 return (EINVAL); 946 } 947 948 shmfd->shm_kmappings++; 949 vm_object_reference_locked(obj); 950 VM_OBJECT_WUNLOCK(obj); 951 952 /* Map the object into the kernel_map and wire it. */ 953 kva = vm_map_min(kernel_map); 954 ofs = offset & PAGE_MASK; 955 offset = trunc_page(offset); 956 size = round_page(size + ofs); 957 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0, 958 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 959 VM_PROT_READ | VM_PROT_WRITE, 0); 960 if (rv == KERN_SUCCESS) { 961 rv = vm_map_wire(kernel_map, kva, kva + size, 962 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 963 if (rv == KERN_SUCCESS) { 964 *memp = (void *)(kva + ofs); 965 return (0); 966 } 967 vm_map_remove(kernel_map, kva, kva + size); 968 } else 969 vm_object_deallocate(obj); 970 971 /* On failure, drop our mapping reference. */ 972 VM_OBJECT_WLOCK(obj); 973 shmfd->shm_kmappings--; 974 VM_OBJECT_WUNLOCK(obj); 975 976 return (vm_mmap_to_errno(rv)); 977 } 978 979 /* 980 * We require the caller to unmap the entire entry. This allows us to 981 * safely decrement shm_kmappings when a mapping is removed. 982 */ 983 int 984 shm_unmap(struct file *fp, void *mem, size_t size) 985 { 986 struct shmfd *shmfd; 987 vm_map_entry_t entry; 988 vm_offset_t kva, ofs; 989 vm_object_t obj; 990 vm_pindex_t pindex; 991 vm_prot_t prot; 992 boolean_t wired; 993 vm_map_t map; 994 int rv; 995 996 if (fp->f_type != DTYPE_SHM) 997 return (EINVAL); 998 shmfd = fp->f_data; 999 kva = (vm_offset_t)mem; 1000 ofs = kva & PAGE_MASK; 1001 kva = trunc_page(kva); 1002 size = round_page(size + ofs); 1003 map = kernel_map; 1004 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 1005 &obj, &pindex, &prot, &wired); 1006 if (rv != KERN_SUCCESS) 1007 return (EINVAL); 1008 if (entry->start != kva || entry->end != kva + size) { 1009 vm_map_lookup_done(map, entry); 1010 return (EINVAL); 1011 } 1012 vm_map_lookup_done(map, entry); 1013 if (obj != shmfd->shm_object) 1014 return (EINVAL); 1015 vm_map_remove(map, kva, kva + size); 1016 VM_OBJECT_WLOCK(obj); 1017 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 1018 shmfd->shm_kmappings--; 1019 VM_OBJECT_WUNLOCK(obj); 1020 return (0); 1021 } 1022 1023 void 1024 shm_path(struct shmfd *shmfd, char *path, size_t size) 1025 { 1026 1027 if (shmfd->shm_path == NULL) 1028 return; 1029 sx_slock(&shm_dict_lock); 1030 if (shmfd->shm_path != NULL) 1031 strlcpy(path, shmfd->shm_path, size); 1032 sx_sunlock(&shm_dict_lock); 1033 }
Cache object: 1fa60e4018ecb9023ade50b6c7861b5b
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