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 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 * (2) 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 * (3) Add support for this file type to fstat(1). 39 * 40 * (4) Resource limits? Does this need its own resource limits or are the 41 * existing limits in mmap(2) sufficient? 42 * 43 * (5) Partial page truncation. vnode_pager_setsize() will zero any parts 44 * of a partially mapped page as a result of ftruncate(2)/truncate(2). 45 * We can do the same (with the same pmap evil), but do we need to 46 * worry about the bits on disk if the page is swapped out or will the 47 * swapper zero the parts of a page that are invalid if the page is 48 * swapped back in for us? 49 * 50 * (6) Add MAC support in mac_biba(4) and mac_mls(4). 51 * 52 * (7) Add a MAC check_create() hook for creating new named objects. 53 */ 54 55 #include <sys/cdefs.h> 56 __FBSDID("$FreeBSD: releng/8.4/sys/kern/uipc_shm.c 236699 2012-06-06 21:57:03Z jhb $"); 57 58 #include <sys/param.h> 59 #include <sys/fcntl.h> 60 #include <sys/file.h> 61 #include <sys/filedesc.h> 62 #include <sys/fnv_hash.h> 63 #include <sys/kernel.h> 64 #include <sys/lock.h> 65 #include <sys/malloc.h> 66 #include <sys/mman.h> 67 #include <sys/mutex.h> 68 #include <sys/proc.h> 69 #include <sys/refcount.h> 70 #include <sys/resourcevar.h> 71 #include <sys/stat.h> 72 #include <sys/sysctl.h> 73 #include <sys/sysproto.h> 74 #include <sys/systm.h> 75 #include <sys/sx.h> 76 #include <sys/time.h> 77 #include <sys/vnode.h> 78 79 #include <security/mac/mac_framework.h> 80 81 #include <vm/vm.h> 82 #include <vm/vm_param.h> 83 #include <vm/pmap.h> 84 #include <vm/vm_extern.h> 85 #include <vm/vm_map.h> 86 #include <vm/vm_kern.h> 87 #include <vm/vm_object.h> 88 #include <vm/vm_page.h> 89 #include <vm/vm_pager.h> 90 #include <vm/swap_pager.h> 91 92 struct shm_mapping { 93 char *sm_path; 94 Fnv32_t sm_fnv; 95 struct shmfd *sm_shmfd; 96 LIST_ENTRY(shm_mapping) sm_link; 97 }; 98 99 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 100 static LIST_HEAD(, shm_mapping) *shm_dictionary; 101 static struct sx shm_dict_lock; 102 static struct mtx shm_timestamp_lock; 103 static u_long shm_hash; 104 105 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 106 107 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 108 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 109 static void shm_dict_init(void *arg); 110 static void shm_drop(struct shmfd *shmfd); 111 static struct shmfd *shm_hold(struct shmfd *shmfd); 112 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 113 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 114 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 115 static int shm_dotruncate(struct shmfd *shmfd, off_t length); 116 117 static fo_rdwr_t shm_read; 118 static fo_rdwr_t shm_write; 119 static fo_truncate_t shm_truncate; 120 static fo_ioctl_t shm_ioctl; 121 static fo_poll_t shm_poll; 122 static fo_kqfilter_t shm_kqfilter; 123 static fo_stat_t shm_stat; 124 static fo_close_t shm_close; 125 126 /* File descriptor operations. */ 127 static struct fileops shm_ops = { 128 .fo_read = shm_read, 129 .fo_write = shm_write, 130 .fo_truncate = shm_truncate, 131 .fo_ioctl = shm_ioctl, 132 .fo_poll = shm_poll, 133 .fo_kqfilter = shm_kqfilter, 134 .fo_stat = shm_stat, 135 .fo_close = shm_close, 136 .fo_flags = DFLAG_PASSABLE 137 }; 138 139 FEATURE(posix_shm, "POSIX shared memory"); 140 141 static int 142 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 143 int flags, struct thread *td) 144 { 145 146 return (EOPNOTSUPP); 147 } 148 149 static int 150 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 151 int flags, struct thread *td) 152 { 153 154 return (EOPNOTSUPP); 155 } 156 157 static int 158 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 159 struct thread *td) 160 { 161 struct shmfd *shmfd; 162 #ifdef MAC 163 int error; 164 #endif 165 166 shmfd = fp->f_data; 167 #ifdef MAC 168 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 169 if (error) 170 return (error); 171 #endif 172 return (shm_dotruncate(shmfd, length)); 173 } 174 175 static int 176 shm_ioctl(struct file *fp, u_long com, void *data, 177 struct ucred *active_cred, struct thread *td) 178 { 179 180 return (EOPNOTSUPP); 181 } 182 183 static int 184 shm_poll(struct file *fp, int events, struct ucred *active_cred, 185 struct thread *td) 186 { 187 188 return (EOPNOTSUPP); 189 } 190 191 static int 192 shm_kqfilter(struct file *fp, struct knote *kn) 193 { 194 195 return (EOPNOTSUPP); 196 } 197 198 static int 199 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 200 struct thread *td) 201 { 202 struct shmfd *shmfd; 203 #ifdef MAC 204 int error; 205 #endif 206 207 shmfd = fp->f_data; 208 209 #ifdef MAC 210 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 211 if (error) 212 return (error); 213 #endif 214 215 /* 216 * Attempt to return sanish values for fstat() on a memory file 217 * descriptor. 218 */ 219 bzero(sb, sizeof(*sb)); 220 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 221 sb->st_blksize = PAGE_SIZE; 222 sb->st_size = shmfd->shm_size; 223 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 224 sb->st_atimespec = shmfd->shm_atime; 225 sb->st_ctimespec = shmfd->shm_ctime; 226 sb->st_mtimespec = shmfd->shm_mtime; 227 sb->st_birthtimespec = shmfd->shm_birthtime; 228 sb->st_uid = shmfd->shm_uid; 229 sb->st_gid = shmfd->shm_gid; 230 231 return (0); 232 } 233 234 static int 235 shm_close(struct file *fp, struct thread *td) 236 { 237 struct shmfd *shmfd; 238 239 shmfd = fp->f_data; 240 fp->f_data = NULL; 241 shm_drop(shmfd); 242 243 return (0); 244 } 245 246 static int 247 shm_dotruncate(struct shmfd *shmfd, off_t length) 248 { 249 vm_object_t object; 250 vm_page_t m; 251 vm_pindex_t nobjsize; 252 vm_ooffset_t delta; 253 254 object = shmfd->shm_object; 255 VM_OBJECT_LOCK(object); 256 if (length == shmfd->shm_size) { 257 VM_OBJECT_UNLOCK(object); 258 return (0); 259 } 260 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 261 262 /* Are we shrinking? If so, trim the end. */ 263 if (length < shmfd->shm_size) { 264 /* 265 * Disallow any requests to shrink the size if this 266 * object is mapped into the kernel. 267 */ 268 if (shmfd->shm_kmappings > 0) { 269 VM_OBJECT_UNLOCK(object); 270 return (EBUSY); 271 } 272 delta = ptoa(object->size - nobjsize); 273 274 /* Toss in memory pages. */ 275 if (nobjsize < object->size) 276 vm_object_page_remove(object, nobjsize, object->size, 277 FALSE); 278 279 /* Toss pages from swap. */ 280 if (object->type == OBJT_SWAP) 281 swap_pager_freespace(object, nobjsize, delta); 282 283 /* Free the swap accounted for shm */ 284 swap_release_by_uid(delta, object->uip); 285 object->charge -= delta; 286 287 /* 288 * If the last page is partially mapped, then zero out 289 * the garbage at the end of the page. See comments 290 * in vnode_pager_setsize() for more details. 291 * 292 * XXXJHB: This handles in memory pages, but what about 293 * a page swapped out to disk? 294 */ 295 if ((length & PAGE_MASK) && 296 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL && 297 m->valid != 0) { 298 int base = (int)length & PAGE_MASK; 299 int size = PAGE_SIZE - base; 300 301 pmap_zero_page_area(m, base, size); 302 303 /* 304 * Update the valid bits to reflect the blocks that 305 * have been zeroed. Some of these valid bits may 306 * have already been set. 307 */ 308 vm_page_set_valid(m, base, size); 309 310 /* 311 * Round "base" to the next block boundary so that the 312 * dirty bit for a partially zeroed block is not 313 * cleared. 314 */ 315 base = roundup2(base, DEV_BSIZE); 316 317 vm_page_lock_queues(); 318 vm_page_clear_dirty(m, base, PAGE_SIZE - base); 319 vm_page_unlock_queues(); 320 } else if ((length & PAGE_MASK) && 321 __predict_false(object->cache != NULL)) { 322 vm_page_cache_free(object, OFF_TO_IDX(length), 323 nobjsize); 324 } 325 } else { 326 327 /* Attempt to reserve the swap */ 328 delta = ptoa(nobjsize - object->size); 329 if (!swap_reserve_by_uid(delta, object->uip)) { 330 VM_OBJECT_UNLOCK(object); 331 return (ENOMEM); 332 } 333 object->charge += delta; 334 } 335 shmfd->shm_size = length; 336 mtx_lock(&shm_timestamp_lock); 337 vfs_timestamp(&shmfd->shm_ctime); 338 shmfd->shm_mtime = shmfd->shm_ctime; 339 mtx_unlock(&shm_timestamp_lock); 340 object->size = nobjsize; 341 VM_OBJECT_UNLOCK(object); 342 return (0); 343 } 344 345 /* 346 * shmfd object management including creation and reference counting 347 * routines. 348 */ 349 static struct shmfd * 350 shm_alloc(struct ucred *ucred, mode_t mode) 351 { 352 struct shmfd *shmfd; 353 354 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 355 shmfd->shm_size = 0; 356 shmfd->shm_uid = ucred->cr_uid; 357 shmfd->shm_gid = ucred->cr_gid; 358 shmfd->shm_mode = mode; 359 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 360 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 361 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 362 VM_OBJECT_LOCK(shmfd->shm_object); 363 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 364 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 365 VM_OBJECT_UNLOCK(shmfd->shm_object); 366 vfs_timestamp(&shmfd->shm_birthtime); 367 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 368 shmfd->shm_birthtime; 369 refcount_init(&shmfd->shm_refs, 1); 370 #ifdef MAC 371 mac_posixshm_init(shmfd); 372 mac_posixshm_create(ucred, shmfd); 373 #endif 374 375 return (shmfd); 376 } 377 378 static struct shmfd * 379 shm_hold(struct shmfd *shmfd) 380 { 381 382 refcount_acquire(&shmfd->shm_refs); 383 return (shmfd); 384 } 385 386 static void 387 shm_drop(struct shmfd *shmfd) 388 { 389 390 if (refcount_release(&shmfd->shm_refs)) { 391 #ifdef MAC 392 mac_posixshm_destroy(shmfd); 393 #endif 394 vm_object_deallocate(shmfd->shm_object); 395 free(shmfd, M_SHMFD); 396 } 397 } 398 399 /* 400 * Determine if the credentials have sufficient permissions for a 401 * specified combination of FREAD and FWRITE. 402 */ 403 static int 404 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 405 { 406 accmode_t accmode; 407 408 accmode = 0; 409 if (flags & FREAD) 410 accmode |= VREAD; 411 if (flags & FWRITE) 412 accmode |= VWRITE; 413 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 414 accmode, ucred, NULL)); 415 } 416 417 /* 418 * Dictionary management. We maintain an in-kernel dictionary to map 419 * paths to shmfd objects. We use the FNV hash on the path to store 420 * the mappings in a hash table. 421 */ 422 static void 423 shm_dict_init(void *arg) 424 { 425 426 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 427 sx_init(&shm_dict_lock, "shm dictionary"); 428 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 429 } 430 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 431 432 static struct shmfd * 433 shm_lookup(char *path, Fnv32_t fnv) 434 { 435 struct shm_mapping *map; 436 437 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 438 if (map->sm_fnv != fnv) 439 continue; 440 if (strcmp(map->sm_path, path) == 0) 441 return (map->sm_shmfd); 442 } 443 444 return (NULL); 445 } 446 447 static void 448 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 449 { 450 struct shm_mapping *map; 451 452 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 453 map->sm_path = path; 454 map->sm_fnv = fnv; 455 map->sm_shmfd = shm_hold(shmfd); 456 shmfd->shm_path = path; 457 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 458 } 459 460 static int 461 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 462 { 463 struct shm_mapping *map; 464 int error; 465 466 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 467 if (map->sm_fnv != fnv) 468 continue; 469 if (strcmp(map->sm_path, path) == 0) { 470 #ifdef MAC 471 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 472 if (error) 473 return (error); 474 #endif 475 error = shm_access(map->sm_shmfd, ucred, 476 FREAD | FWRITE); 477 if (error) 478 return (error); 479 map->sm_shmfd->shm_path = NULL; 480 LIST_REMOVE(map, sm_link); 481 shm_drop(map->sm_shmfd); 482 free(map->sm_path, M_SHMFD); 483 free(map, M_SHMFD); 484 return (0); 485 } 486 } 487 488 return (ENOENT); 489 } 490 491 /* System calls. */ 492 int 493 shm_open(struct thread *td, struct shm_open_args *uap) 494 { 495 struct filedesc *fdp; 496 struct shmfd *shmfd; 497 struct file *fp; 498 char *path; 499 Fnv32_t fnv; 500 mode_t cmode; 501 int fd, error; 502 503 if ((uap->flags & O_ACCMODE) != O_RDONLY && 504 (uap->flags & O_ACCMODE) != O_RDWR) 505 return (EINVAL); 506 507 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 508 return (EINVAL); 509 510 fdp = td->td_proc->p_fd; 511 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 512 513 error = falloc(td, &fp, &fd); 514 if (error) 515 return (error); 516 517 /* A SHM_ANON path pointer creates an anonymous object. */ 518 if (uap->path == SHM_ANON) { 519 /* A read-only anonymous object is pointless. */ 520 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 521 fdclose(fdp, fp, fd, td); 522 fdrop(fp, td); 523 return (EINVAL); 524 } 525 shmfd = shm_alloc(td->td_ucred, cmode); 526 } else { 527 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 528 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 529 530 /* Require paths to start with a '/' character. */ 531 if (error == 0 && path[0] != '/') 532 error = EINVAL; 533 if (error) { 534 fdclose(fdp, fp, fd, td); 535 fdrop(fp, td); 536 free(path, M_SHMFD); 537 return (error); 538 } 539 540 fnv = fnv_32_str(path, FNV1_32_INIT); 541 sx_xlock(&shm_dict_lock); 542 shmfd = shm_lookup(path, fnv); 543 if (shmfd == NULL) { 544 /* Object does not yet exist, create it if requested. */ 545 if (uap->flags & O_CREAT) { 546 shmfd = shm_alloc(td->td_ucred, cmode); 547 shm_insert(path, fnv, shmfd); 548 } else { 549 free(path, M_SHMFD); 550 error = ENOENT; 551 } 552 } else { 553 /* 554 * Object already exists, obtain a new 555 * reference if requested and permitted. 556 */ 557 free(path, M_SHMFD); 558 if ((uap->flags & (O_CREAT | O_EXCL)) == 559 (O_CREAT | O_EXCL)) 560 error = EEXIST; 561 else { 562 #ifdef MAC 563 error = mac_posixshm_check_open(td->td_ucred, 564 shmfd); 565 if (error == 0) 566 #endif 567 error = shm_access(shmfd, td->td_ucred, 568 FFLAGS(uap->flags & O_ACCMODE)); 569 } 570 571 /* 572 * Truncate the file back to zero length if 573 * O_TRUNC was specified and the object was 574 * opened with read/write. 575 */ 576 if (error == 0 && 577 (uap->flags & (O_ACCMODE | O_TRUNC)) == 578 (O_RDWR | O_TRUNC)) { 579 #ifdef MAC 580 error = mac_posixshm_check_truncate( 581 td->td_ucred, fp->f_cred, shmfd); 582 if (error == 0) 583 #endif 584 shm_dotruncate(shmfd, 0); 585 } 586 if (error == 0) 587 shm_hold(shmfd); 588 } 589 sx_xunlock(&shm_dict_lock); 590 591 if (error) { 592 fdclose(fdp, fp, fd, td); 593 fdrop(fp, td); 594 return (error); 595 } 596 } 597 598 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 599 600 FILEDESC_XLOCK(fdp); 601 if (fdp->fd_ofiles[fd] == fp) 602 fdp->fd_ofileflags[fd] |= UF_EXCLOSE; 603 FILEDESC_XUNLOCK(fdp); 604 td->td_retval[0] = fd; 605 fdrop(fp, td); 606 607 return (0); 608 } 609 610 int 611 shm_unlink(struct thread *td, struct shm_unlink_args *uap) 612 { 613 char *path; 614 Fnv32_t fnv; 615 int error; 616 617 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 618 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 619 if (error) { 620 free(path, M_TEMP); 621 return (error); 622 } 623 624 fnv = fnv_32_str(path, FNV1_32_INIT); 625 sx_xlock(&shm_dict_lock); 626 error = shm_remove(path, fnv, td->td_ucred); 627 sx_xunlock(&shm_dict_lock); 628 free(path, M_TEMP); 629 630 return (error); 631 } 632 633 /* 634 * mmap() helper to validate mmap() requests against shm object state 635 * and give mmap() the vm_object to use for the mapping. 636 */ 637 int 638 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 639 vm_object_t *obj) 640 { 641 642 /* 643 * XXXRW: This validation is probably insufficient, and subject to 644 * sign errors. It should be fixed. 645 */ 646 if (foff >= shmfd->shm_size || 647 foff + objsize > round_page(shmfd->shm_size)) 648 return (EINVAL); 649 650 mtx_lock(&shm_timestamp_lock); 651 vfs_timestamp(&shmfd->shm_atime); 652 mtx_unlock(&shm_timestamp_lock); 653 vm_object_reference(shmfd->shm_object); 654 *obj = shmfd->shm_object; 655 return (0); 656 } 657 658 /* 659 * Helper routines to allow the backing object of a shared memory file 660 * descriptor to be mapped in the kernel. 661 */ 662 int 663 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 664 { 665 struct shmfd *shmfd; 666 vm_offset_t kva, ofs; 667 vm_object_t obj; 668 int rv; 669 670 if (fp->f_type != DTYPE_SHM) 671 return (EINVAL); 672 shmfd = fp->f_data; 673 obj = shmfd->shm_object; 674 VM_OBJECT_LOCK(obj); 675 /* 676 * XXXRW: This validation is probably insufficient, and subject to 677 * sign errors. It should be fixed. 678 */ 679 if (offset >= shmfd->shm_size || 680 offset + size > round_page(shmfd->shm_size)) { 681 VM_OBJECT_UNLOCK(obj); 682 return (EINVAL); 683 } 684 685 shmfd->shm_kmappings++; 686 vm_object_reference_locked(obj); 687 VM_OBJECT_UNLOCK(obj); 688 689 /* Map the object into the kernel_map and wire it. */ 690 kva = vm_map_min(kernel_map); 691 ofs = offset & PAGE_MASK; 692 offset = trunc_page(offset); 693 size = round_page(size + ofs); 694 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 695 VMFS_ALIGNED_SPACE, VM_PROT_READ | VM_PROT_WRITE, 696 VM_PROT_READ | VM_PROT_WRITE, 0); 697 if (rv == KERN_SUCCESS) { 698 rv = vm_map_wire(kernel_map, kva, kva + size, 699 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 700 if (rv == KERN_SUCCESS) { 701 *memp = (void *)(kva + ofs); 702 return (0); 703 } 704 vm_map_remove(kernel_map, kva, kva + size); 705 } else 706 vm_object_deallocate(obj); 707 708 /* On failure, drop our mapping reference. */ 709 VM_OBJECT_LOCK(obj); 710 shmfd->shm_kmappings--; 711 VM_OBJECT_UNLOCK(obj); 712 713 return (vm_mmap_to_errno(rv)); 714 } 715 716 /* 717 * We require the caller to unmap the entire entry. This allows us to 718 * safely decrement shm_kmappings when a mapping is removed. 719 */ 720 int 721 shm_unmap(struct file *fp, void *mem, size_t size) 722 { 723 struct shmfd *shmfd; 724 vm_map_entry_t entry; 725 vm_offset_t kva, ofs; 726 vm_object_t obj; 727 vm_pindex_t pindex; 728 vm_prot_t prot; 729 boolean_t wired; 730 vm_map_t map; 731 int rv; 732 733 if (fp->f_type != DTYPE_SHM) 734 return (EINVAL); 735 shmfd = fp->f_data; 736 kva = (vm_offset_t)mem; 737 ofs = kva & PAGE_MASK; 738 kva = trunc_page(kva); 739 size = round_page(size + ofs); 740 map = kernel_map; 741 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 742 &obj, &pindex, &prot, &wired); 743 if (rv != KERN_SUCCESS) 744 return (EINVAL); 745 if (entry->start != kva || entry->end != kva + size) { 746 vm_map_lookup_done(map, entry); 747 return (EINVAL); 748 } 749 vm_map_lookup_done(map, entry); 750 if (obj != shmfd->shm_object) 751 return (EINVAL); 752 vm_map_remove(map, kva, kva + size); 753 VM_OBJECT_LOCK(obj); 754 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 755 shmfd->shm_kmappings--; 756 VM_OBJECT_UNLOCK(obj); 757 return (0); 758 } 759 760 void 761 shm_path(struct shmfd *shmfd, char *path, size_t size) 762 { 763 764 if (shmfd->shm_path == NULL) 765 return; 766 sx_slock(&shm_dict_lock); 767 if (shmfd->shm_path != NULL) 768 strlcpy(path, shmfd->shm_path, size); 769 sx_sunlock(&shm_dict_lock); 770 }
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