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("$FreeBSD$"); 57 58 #include <sys/param.h> 59 #include <sys/conf.h> 60 #include <sys/fcntl.h> 61 #include <sys/file.h> 62 #include <sys/filedesc.h> 63 #include <sys/fnv_hash.h> 64 #include <sys/kernel.h> 65 #include <sys/lock.h> 66 #include <sys/malloc.h> 67 #include <sys/mman.h> 68 #include <sys/mutex.h> 69 #include <sys/proc.h> 70 #include <sys/refcount.h> 71 #include <sys/resourcevar.h> 72 #include <sys/stat.h> 73 #include <sys/sysctl.h> 74 #include <sys/sysproto.h> 75 #include <sys/systm.h> 76 #include <sys/sx.h> 77 #include <sys/time.h> 78 #include <sys/vnode.h> 79 80 #include <security/mac/mac_framework.h> 81 82 #include <vm/vm.h> 83 #include <vm/vm_param.h> 84 #include <vm/pmap.h> 85 #include <vm/vm_extern.h> 86 #include <vm/vm_map.h> 87 #include <vm/vm_kern.h> 88 #include <vm/vm_object.h> 89 #include <vm/vm_page.h> 90 #include <vm/vm_pager.h> 91 #include <vm/swap_pager.h> 92 93 struct shm_mapping { 94 char *sm_path; 95 Fnv32_t sm_fnv; 96 struct shmfd *sm_shmfd; 97 LIST_ENTRY(shm_mapping) sm_link; 98 }; 99 100 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 101 static LIST_HEAD(, shm_mapping) *shm_dictionary; 102 static struct sx shm_dict_lock; 103 static struct mtx shm_timestamp_lock; 104 static u_long shm_hash; 105 static struct unrhdr *shm_ino_unr; 106 static dev_t shm_dev_ino; 107 108 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 109 110 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 111 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 112 static void shm_init(void *arg); 113 static void shm_drop(struct shmfd *shmfd); 114 static struct shmfd *shm_hold(struct shmfd *shmfd); 115 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 116 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 117 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 118 static int shm_dotruncate(struct shmfd *shmfd, off_t length); 119 120 static fo_rdwr_t shm_read; 121 static fo_rdwr_t shm_write; 122 static fo_truncate_t shm_truncate; 123 static fo_ioctl_t shm_ioctl; 124 static fo_poll_t shm_poll; 125 static fo_kqfilter_t shm_kqfilter; 126 static fo_stat_t shm_stat; 127 static fo_close_t shm_close; 128 129 /* File descriptor operations. */ 130 static struct fileops shm_ops = { 131 .fo_read = shm_read, 132 .fo_write = shm_write, 133 .fo_truncate = shm_truncate, 134 .fo_ioctl = shm_ioctl, 135 .fo_poll = shm_poll, 136 .fo_kqfilter = shm_kqfilter, 137 .fo_stat = shm_stat, 138 .fo_close = shm_close, 139 .fo_flags = DFLAG_PASSABLE 140 }; 141 142 FEATURE(posix_shm, "POSIX shared memory"); 143 144 static int 145 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 146 int flags, struct thread *td) 147 { 148 149 return (EOPNOTSUPP); 150 } 151 152 static int 153 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 154 int flags, struct thread *td) 155 { 156 157 return (EOPNOTSUPP); 158 } 159 160 static int 161 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 162 struct thread *td) 163 { 164 struct shmfd *shmfd; 165 #ifdef MAC 166 int error; 167 #endif 168 169 shmfd = fp->f_data; 170 #ifdef MAC 171 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 172 if (error) 173 return (error); 174 #endif 175 return (shm_dotruncate(shmfd, length)); 176 } 177 178 static int 179 shm_ioctl(struct file *fp, u_long com, void *data, 180 struct ucred *active_cred, struct thread *td) 181 { 182 183 return (EOPNOTSUPP); 184 } 185 186 static int 187 shm_poll(struct file *fp, int events, struct ucred *active_cred, 188 struct thread *td) 189 { 190 191 return (EOPNOTSUPP); 192 } 193 194 static int 195 shm_kqfilter(struct file *fp, struct knote *kn) 196 { 197 198 return (EOPNOTSUPP); 199 } 200 201 static int 202 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 203 struct thread *td) 204 { 205 struct shmfd *shmfd; 206 #ifdef MAC 207 int error; 208 #endif 209 210 shmfd = fp->f_data; 211 212 #ifdef MAC 213 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 214 if (error) 215 return (error); 216 #endif 217 218 /* 219 * Attempt to return sanish values for fstat() on a memory file 220 * descriptor. 221 */ 222 bzero(sb, sizeof(*sb)); 223 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 224 sb->st_blksize = PAGE_SIZE; 225 sb->st_size = shmfd->shm_size; 226 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 227 sb->st_atimespec = shmfd->shm_atime; 228 sb->st_ctimespec = shmfd->shm_ctime; 229 sb->st_mtimespec = shmfd->shm_mtime; 230 sb->st_birthtimespec = shmfd->shm_birthtime; 231 sb->st_uid = shmfd->shm_uid; 232 sb->st_gid = shmfd->shm_gid; 233 sb->st_dev = shm_dev_ino; 234 sb->st_ino = shmfd->shm_ino; 235 236 return (0); 237 } 238 239 static int 240 shm_close(struct file *fp, struct thread *td) 241 { 242 struct shmfd *shmfd; 243 244 shmfd = fp->f_data; 245 fp->f_data = NULL; 246 shm_drop(shmfd); 247 248 return (0); 249 } 250 251 static int 252 shm_dotruncate(struct shmfd *shmfd, off_t length) 253 { 254 vm_object_t object; 255 vm_page_t m; 256 vm_pindex_t nobjsize; 257 vm_ooffset_t delta; 258 259 object = shmfd->shm_object; 260 VM_OBJECT_LOCK(object); 261 if (length == shmfd->shm_size) { 262 VM_OBJECT_UNLOCK(object); 263 return (0); 264 } 265 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 266 267 /* Are we shrinking? If so, trim the end. */ 268 if (length < shmfd->shm_size) { 269 /* 270 * Disallow any requests to shrink the size if this 271 * object is mapped into the kernel. 272 */ 273 if (shmfd->shm_kmappings > 0) { 274 VM_OBJECT_UNLOCK(object); 275 return (EBUSY); 276 } 277 delta = ptoa(object->size - nobjsize); 278 279 /* Toss in memory pages. */ 280 if (nobjsize < object->size) 281 vm_object_page_remove(object, nobjsize, object->size, 282 FALSE); 283 284 /* Toss pages from swap. */ 285 if (object->type == OBJT_SWAP) 286 swap_pager_freespace(object, nobjsize, delta); 287 288 /* Free the swap accounted for shm */ 289 swap_release_by_uid(delta, object->uip); 290 object->charge -= delta; 291 292 /* 293 * If the last page is partially mapped, then zero out 294 * the garbage at the end of the page. See comments 295 * in vnode_pager_setsize() for more details. 296 * 297 * XXXJHB: This handles in memory pages, but what about 298 * a page swapped out to disk? 299 */ 300 if ((length & PAGE_MASK) && 301 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL && 302 m->valid != 0) { 303 int base = (int)length & PAGE_MASK; 304 int size = PAGE_SIZE - base; 305 306 pmap_zero_page_area(m, base, size); 307 308 /* 309 * Update the valid bits to reflect the blocks that 310 * have been zeroed. Some of these valid bits may 311 * have already been set. 312 */ 313 vm_page_set_valid(m, base, size); 314 315 /* 316 * Round "base" to the next block boundary so that the 317 * dirty bit for a partially zeroed block is not 318 * cleared. 319 */ 320 base = roundup2(base, DEV_BSIZE); 321 322 vm_page_lock_queues(); 323 vm_page_clear_dirty(m, base, PAGE_SIZE - base); 324 vm_page_unlock_queues(); 325 } else if ((length & PAGE_MASK) && 326 __predict_false(object->cache != NULL)) { 327 vm_page_cache_free(object, OFF_TO_IDX(length), 328 nobjsize); 329 } 330 } else { 331 332 /* Attempt to reserve the swap */ 333 delta = ptoa(nobjsize - object->size); 334 if (!swap_reserve_by_uid(delta, object->uip)) { 335 VM_OBJECT_UNLOCK(object); 336 return (ENOMEM); 337 } 338 object->charge += delta; 339 } 340 shmfd->shm_size = length; 341 mtx_lock(&shm_timestamp_lock); 342 vfs_timestamp(&shmfd->shm_ctime); 343 shmfd->shm_mtime = shmfd->shm_ctime; 344 mtx_unlock(&shm_timestamp_lock); 345 object->size = nobjsize; 346 VM_OBJECT_UNLOCK(object); 347 return (0); 348 } 349 350 /* 351 * shmfd object management including creation and reference counting 352 * routines. 353 */ 354 static struct shmfd * 355 shm_alloc(struct ucred *ucred, mode_t mode) 356 { 357 struct shmfd *shmfd; 358 int ino; 359 360 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 361 shmfd->shm_size = 0; 362 shmfd->shm_uid = ucred->cr_uid; 363 shmfd->shm_gid = ucred->cr_gid; 364 shmfd->shm_mode = mode; 365 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 366 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 367 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 368 VM_OBJECT_LOCK(shmfd->shm_object); 369 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 370 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 371 VM_OBJECT_UNLOCK(shmfd->shm_object); 372 vfs_timestamp(&shmfd->shm_birthtime); 373 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 374 shmfd->shm_birthtime; 375 ino = alloc_unr(shm_ino_unr); 376 if (ino == -1) 377 shmfd->shm_ino = 0; 378 else 379 shmfd->shm_ino = ino; 380 refcount_init(&shmfd->shm_refs, 1); 381 #ifdef MAC 382 mac_posixshm_init(shmfd); 383 mac_posixshm_create(ucred, shmfd); 384 #endif 385 386 return (shmfd); 387 } 388 389 static struct shmfd * 390 shm_hold(struct shmfd *shmfd) 391 { 392 393 refcount_acquire(&shmfd->shm_refs); 394 return (shmfd); 395 } 396 397 static void 398 shm_drop(struct shmfd *shmfd) 399 { 400 401 if (refcount_release(&shmfd->shm_refs)) { 402 #ifdef MAC 403 mac_posixshm_destroy(shmfd); 404 #endif 405 vm_object_deallocate(shmfd->shm_object); 406 if (shmfd->shm_ino != 0) 407 free_unr(shm_ino_unr, shmfd->shm_ino); 408 free(shmfd, M_SHMFD); 409 } 410 } 411 412 /* 413 * Determine if the credentials have sufficient permissions for a 414 * specified combination of FREAD and FWRITE. 415 */ 416 static int 417 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 418 { 419 accmode_t accmode; 420 421 accmode = 0; 422 if (flags & FREAD) 423 accmode |= VREAD; 424 if (flags & FWRITE) 425 accmode |= VWRITE; 426 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 427 accmode, ucred, NULL)); 428 } 429 430 /* 431 * Dictionary management. We maintain an in-kernel dictionary to map 432 * paths to shmfd objects. We use the FNV hash on the path to store 433 * the mappings in a hash table. 434 */ 435 static void 436 shm_init(void *arg) 437 { 438 439 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 440 sx_init(&shm_dict_lock, "shm dictionary"); 441 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 442 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL); 443 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized")); 444 shm_dev_ino = devfs_alloc_cdp_inode(); 445 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized")); 446 } 447 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL); 448 449 static struct shmfd * 450 shm_lookup(char *path, Fnv32_t fnv) 451 { 452 struct shm_mapping *map; 453 454 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 455 if (map->sm_fnv != fnv) 456 continue; 457 if (strcmp(map->sm_path, path) == 0) 458 return (map->sm_shmfd); 459 } 460 461 return (NULL); 462 } 463 464 static void 465 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 466 { 467 struct shm_mapping *map; 468 469 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 470 map->sm_path = path; 471 map->sm_fnv = fnv; 472 map->sm_shmfd = shm_hold(shmfd); 473 shmfd->shm_path = path; 474 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 475 } 476 477 static int 478 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 479 { 480 struct shm_mapping *map; 481 int error; 482 483 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 484 if (map->sm_fnv != fnv) 485 continue; 486 if (strcmp(map->sm_path, path) == 0) { 487 #ifdef MAC 488 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 489 if (error) 490 return (error); 491 #endif 492 error = shm_access(map->sm_shmfd, ucred, 493 FREAD | FWRITE); 494 if (error) 495 return (error); 496 map->sm_shmfd->shm_path = NULL; 497 LIST_REMOVE(map, sm_link); 498 shm_drop(map->sm_shmfd); 499 free(map->sm_path, M_SHMFD); 500 free(map, M_SHMFD); 501 return (0); 502 } 503 } 504 505 return (ENOENT); 506 } 507 508 /* System calls. */ 509 int 510 shm_open(struct thread *td, struct shm_open_args *uap) 511 { 512 struct filedesc *fdp; 513 struct shmfd *shmfd; 514 struct file *fp; 515 char *path; 516 Fnv32_t fnv; 517 mode_t cmode; 518 int fd, error; 519 520 if ((uap->flags & O_ACCMODE) != O_RDONLY && 521 (uap->flags & O_ACCMODE) != O_RDWR) 522 return (EINVAL); 523 524 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 525 return (EINVAL); 526 527 fdp = td->td_proc->p_fd; 528 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 529 530 error = falloc(td, &fp, &fd); 531 if (error) 532 return (error); 533 534 /* A SHM_ANON path pointer creates an anonymous object. */ 535 if (uap->path == SHM_ANON) { 536 /* A read-only anonymous object is pointless. */ 537 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 538 fdclose(fdp, fp, fd, td); 539 fdrop(fp, td); 540 return (EINVAL); 541 } 542 shmfd = shm_alloc(td->td_ucred, cmode); 543 } else { 544 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 545 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 546 547 /* Require paths to start with a '/' character. */ 548 if (error == 0 && path[0] != '/') 549 error = EINVAL; 550 if (error) { 551 fdclose(fdp, fp, fd, td); 552 fdrop(fp, td); 553 free(path, M_SHMFD); 554 return (error); 555 } 556 557 fnv = fnv_32_str(path, FNV1_32_INIT); 558 sx_xlock(&shm_dict_lock); 559 shmfd = shm_lookup(path, fnv); 560 if (shmfd == NULL) { 561 /* Object does not yet exist, create it if requested. */ 562 if (uap->flags & O_CREAT) { 563 shmfd = shm_alloc(td->td_ucred, cmode); 564 shm_insert(path, fnv, shmfd); 565 } else { 566 free(path, M_SHMFD); 567 error = ENOENT; 568 } 569 } else { 570 /* 571 * Object already exists, obtain a new 572 * reference if requested and permitted. 573 */ 574 free(path, M_SHMFD); 575 if ((uap->flags & (O_CREAT | O_EXCL)) == 576 (O_CREAT | O_EXCL)) 577 error = EEXIST; 578 else { 579 #ifdef MAC 580 error = mac_posixshm_check_open(td->td_ucred, 581 shmfd); 582 if (error == 0) 583 #endif 584 error = shm_access(shmfd, td->td_ucred, 585 FFLAGS(uap->flags & O_ACCMODE)); 586 } 587 588 /* 589 * Truncate the file back to zero length if 590 * O_TRUNC was specified and the object was 591 * opened with read/write. 592 */ 593 if (error == 0 && 594 (uap->flags & (O_ACCMODE | O_TRUNC)) == 595 (O_RDWR | O_TRUNC)) { 596 #ifdef MAC 597 error = mac_posixshm_check_truncate( 598 td->td_ucred, fp->f_cred, shmfd); 599 if (error == 0) 600 #endif 601 shm_dotruncate(shmfd, 0); 602 } 603 if (error == 0) 604 shm_hold(shmfd); 605 } 606 sx_xunlock(&shm_dict_lock); 607 608 if (error) { 609 fdclose(fdp, fp, fd, td); 610 fdrop(fp, td); 611 return (error); 612 } 613 } 614 615 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 616 617 FILEDESC_XLOCK(fdp); 618 if (fdp->fd_ofiles[fd] == fp) 619 fdp->fd_ofileflags[fd] |= UF_EXCLOSE; 620 FILEDESC_XUNLOCK(fdp); 621 td->td_retval[0] = fd; 622 fdrop(fp, td); 623 624 return (0); 625 } 626 627 int 628 shm_unlink(struct thread *td, struct shm_unlink_args *uap) 629 { 630 char *path; 631 Fnv32_t fnv; 632 int error; 633 634 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 635 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 636 if (error) { 637 free(path, M_TEMP); 638 return (error); 639 } 640 641 fnv = fnv_32_str(path, FNV1_32_INIT); 642 sx_xlock(&shm_dict_lock); 643 error = shm_remove(path, fnv, td->td_ucred); 644 sx_xunlock(&shm_dict_lock); 645 free(path, M_TEMP); 646 647 return (error); 648 } 649 650 /* 651 * mmap() helper to validate mmap() requests against shm object state 652 * and give mmap() the vm_object to use for the mapping. 653 */ 654 int 655 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 656 vm_object_t *obj) 657 { 658 659 /* 660 * XXXRW: This validation is probably insufficient, and subject to 661 * sign errors. It should be fixed. 662 */ 663 if (foff >= shmfd->shm_size || 664 foff + objsize > round_page(shmfd->shm_size)) 665 return (EINVAL); 666 667 mtx_lock(&shm_timestamp_lock); 668 vfs_timestamp(&shmfd->shm_atime); 669 mtx_unlock(&shm_timestamp_lock); 670 vm_object_reference(shmfd->shm_object); 671 *obj = shmfd->shm_object; 672 return (0); 673 } 674 675 /* 676 * Helper routines to allow the backing object of a shared memory file 677 * descriptor to be mapped in the kernel. 678 */ 679 int 680 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 681 { 682 struct shmfd *shmfd; 683 vm_offset_t kva, ofs; 684 vm_object_t obj; 685 int rv; 686 687 if (fp->f_type != DTYPE_SHM) 688 return (EINVAL); 689 shmfd = fp->f_data; 690 obj = shmfd->shm_object; 691 VM_OBJECT_LOCK(obj); 692 /* 693 * XXXRW: This validation is probably insufficient, and subject to 694 * sign errors. It should be fixed. 695 */ 696 if (offset >= shmfd->shm_size || 697 offset + size > round_page(shmfd->shm_size)) { 698 VM_OBJECT_UNLOCK(obj); 699 return (EINVAL); 700 } 701 702 shmfd->shm_kmappings++; 703 vm_object_reference_locked(obj); 704 VM_OBJECT_UNLOCK(obj); 705 706 /* Map the object into the kernel_map and wire it. */ 707 kva = vm_map_min(kernel_map); 708 ofs = offset & PAGE_MASK; 709 offset = trunc_page(offset); 710 size = round_page(size + ofs); 711 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 712 VMFS_ALIGNED_SPACE, VM_PROT_READ | VM_PROT_WRITE, 713 VM_PROT_READ | VM_PROT_WRITE, 0); 714 if (rv == KERN_SUCCESS) { 715 rv = vm_map_wire(kernel_map, kva, kva + size, 716 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 717 if (rv == KERN_SUCCESS) { 718 *memp = (void *)(kva + ofs); 719 return (0); 720 } 721 vm_map_remove(kernel_map, kva, kva + size); 722 } else 723 vm_object_deallocate(obj); 724 725 /* On failure, drop our mapping reference. */ 726 VM_OBJECT_LOCK(obj); 727 shmfd->shm_kmappings--; 728 VM_OBJECT_UNLOCK(obj); 729 730 return (vm_mmap_to_errno(rv)); 731 } 732 733 /* 734 * We require the caller to unmap the entire entry. This allows us to 735 * safely decrement shm_kmappings when a mapping is removed. 736 */ 737 int 738 shm_unmap(struct file *fp, void *mem, size_t size) 739 { 740 struct shmfd *shmfd; 741 vm_map_entry_t entry; 742 vm_offset_t kva, ofs; 743 vm_object_t obj; 744 vm_pindex_t pindex; 745 vm_prot_t prot; 746 boolean_t wired; 747 vm_map_t map; 748 int rv; 749 750 if (fp->f_type != DTYPE_SHM) 751 return (EINVAL); 752 shmfd = fp->f_data; 753 kva = (vm_offset_t)mem; 754 ofs = kva & PAGE_MASK; 755 kva = trunc_page(kva); 756 size = round_page(size + ofs); 757 map = kernel_map; 758 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 759 &obj, &pindex, &prot, &wired); 760 if (rv != KERN_SUCCESS) 761 return (EINVAL); 762 if (entry->start != kva || entry->end != kva + size) { 763 vm_map_lookup_done(map, entry); 764 return (EINVAL); 765 } 766 vm_map_lookup_done(map, entry); 767 if (obj != shmfd->shm_object) 768 return (EINVAL); 769 vm_map_remove(map, kva, kva + size); 770 VM_OBJECT_LOCK(obj); 771 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 772 shmfd->shm_kmappings--; 773 VM_OBJECT_UNLOCK(obj); 774 return (0); 775 } 776 777 void 778 shm_path(struct shmfd *shmfd, char *path, size_t size) 779 { 780 781 if (shmfd->shm_path == NULL) 782 return; 783 sx_slock(&shm_dict_lock); 784 if (shmfd->shm_path != NULL) 785 strlcpy(path, shmfd->shm_path, size); 786 sx_sunlock(&shm_dict_lock); 787 }
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