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/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_map.h> 85 #include <vm/vm_object.h> 86 #include <vm/vm_page.h> 87 #include <vm/vm_pager.h> 88 #include <vm/swap_pager.h> 89 90 struct shm_mapping { 91 char *sm_path; 92 Fnv32_t sm_fnv; 93 struct shmfd *sm_shmfd; 94 LIST_ENTRY(shm_mapping) sm_link; 95 }; 96 97 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 98 static LIST_HEAD(, shm_mapping) *shm_dictionary; 99 static struct sx shm_dict_lock; 100 static struct mtx shm_timestamp_lock; 101 static u_long shm_hash; 102 103 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 104 105 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 106 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 107 static void shm_dict_init(void *arg); 108 static void shm_drop(struct shmfd *shmfd); 109 static struct shmfd *shm_hold(struct shmfd *shmfd); 110 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 111 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 112 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 113 static int shm_dotruncate(struct shmfd *shmfd, off_t length); 114 115 static fo_rdwr_t shm_read; 116 static fo_rdwr_t shm_write; 117 static fo_truncate_t shm_truncate; 118 static fo_ioctl_t shm_ioctl; 119 static fo_poll_t shm_poll; 120 static fo_kqfilter_t shm_kqfilter; 121 static fo_stat_t shm_stat; 122 static fo_close_t shm_close; 123 124 /* File descriptor operations. */ 125 static struct fileops shm_ops = { 126 .fo_read = shm_read, 127 .fo_write = shm_write, 128 .fo_truncate = shm_truncate, 129 .fo_ioctl = shm_ioctl, 130 .fo_poll = shm_poll, 131 .fo_kqfilter = shm_kqfilter, 132 .fo_stat = shm_stat, 133 .fo_close = shm_close, 134 .fo_flags = DFLAG_PASSABLE 135 }; 136 137 FEATURE(posix_shm, "POSIX shared memory"); 138 139 static int 140 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 141 int flags, struct thread *td) 142 { 143 144 return (EOPNOTSUPP); 145 } 146 147 static int 148 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 149 int flags, struct thread *td) 150 { 151 152 return (EOPNOTSUPP); 153 } 154 155 static int 156 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 157 struct thread *td) 158 { 159 struct shmfd *shmfd; 160 #ifdef MAC 161 int error; 162 #endif 163 164 shmfd = fp->f_data; 165 #ifdef MAC 166 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 167 if (error) 168 return (error); 169 #endif 170 return (shm_dotruncate(shmfd, length)); 171 } 172 173 static int 174 shm_ioctl(struct file *fp, u_long com, void *data, 175 struct ucred *active_cred, struct thread *td) 176 { 177 178 return (EOPNOTSUPP); 179 } 180 181 static int 182 shm_poll(struct file *fp, int events, struct ucred *active_cred, 183 struct thread *td) 184 { 185 186 return (EOPNOTSUPP); 187 } 188 189 static int 190 shm_kqfilter(struct file *fp, struct knote *kn) 191 { 192 193 return (EOPNOTSUPP); 194 } 195 196 static int 197 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 198 struct thread *td) 199 { 200 struct shmfd *shmfd; 201 #ifdef MAC 202 int error; 203 #endif 204 205 shmfd = fp->f_data; 206 207 #ifdef MAC 208 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 209 if (error) 210 return (error); 211 #endif 212 213 /* 214 * Attempt to return sanish values for fstat() on a memory file 215 * descriptor. 216 */ 217 bzero(sb, sizeof(*sb)); 218 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 219 sb->st_blksize = PAGE_SIZE; 220 sb->st_size = shmfd->shm_size; 221 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 222 sb->st_atimespec = shmfd->shm_atime; 223 sb->st_ctimespec = shmfd->shm_ctime; 224 sb->st_mtimespec = shmfd->shm_mtime; 225 sb->st_birthtimespec = shmfd->shm_birthtime; 226 sb->st_uid = shmfd->shm_uid; 227 sb->st_gid = shmfd->shm_gid; 228 229 return (0); 230 } 231 232 static int 233 shm_close(struct file *fp, struct thread *td) 234 { 235 struct shmfd *shmfd; 236 237 shmfd = fp->f_data; 238 fp->f_data = NULL; 239 shm_drop(shmfd); 240 241 return (0); 242 } 243 244 static int 245 shm_dotruncate(struct shmfd *shmfd, off_t length) 246 { 247 vm_object_t object; 248 vm_page_t m; 249 vm_pindex_t nobjsize; 250 vm_ooffset_t delta; 251 252 object = shmfd->shm_object; 253 VM_OBJECT_LOCK(object); 254 if (length == shmfd->shm_size) { 255 VM_OBJECT_UNLOCK(object); 256 return (0); 257 } 258 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 259 260 /* Are we shrinking? If so, trim the end. */ 261 if (length < shmfd->shm_size) { 262 delta = ptoa(object->size - nobjsize); 263 264 /* Toss in memory pages. */ 265 if (nobjsize < object->size) 266 vm_object_page_remove(object, nobjsize, object->size, 267 FALSE); 268 269 /* Toss pages from swap. */ 270 if (object->type == OBJT_SWAP) 271 swap_pager_freespace(object, nobjsize, delta); 272 273 /* Free the swap accounted for shm */ 274 swap_release_by_uid(delta, object->uip); 275 object->charge -= delta; 276 277 /* 278 * If the last page is partially mapped, then zero out 279 * the garbage at the end of the page. See comments 280 * in vnode_pager_setsize() for more details. 281 * 282 * XXXJHB: This handles in memory pages, but what about 283 * a page swapped out to disk? 284 */ 285 if ((length & PAGE_MASK) && 286 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL && 287 m->valid != 0) { 288 int base = (int)length & PAGE_MASK; 289 int size = PAGE_SIZE - base; 290 291 pmap_zero_page_area(m, base, size); 292 293 /* 294 * Update the valid bits to reflect the blocks that 295 * have been zeroed. Some of these valid bits may 296 * have already been set. 297 */ 298 vm_page_set_valid(m, base, size); 299 300 /* 301 * Round "base" to the next block boundary so that the 302 * dirty bit for a partially zeroed block is not 303 * cleared. 304 */ 305 base = roundup2(base, DEV_BSIZE); 306 307 vm_page_lock_queues(); 308 vm_page_clear_dirty(m, base, PAGE_SIZE - base); 309 vm_page_unlock_queues(); 310 } else if ((length & PAGE_MASK) && 311 __predict_false(object->cache != NULL)) { 312 vm_page_cache_free(object, OFF_TO_IDX(length), 313 nobjsize); 314 } 315 } else { 316 317 /* Attempt to reserve the swap */ 318 delta = ptoa(nobjsize - object->size); 319 if (!swap_reserve_by_uid(delta, object->uip)) { 320 VM_OBJECT_UNLOCK(object); 321 return (ENOMEM); 322 } 323 object->charge += delta; 324 } 325 shmfd->shm_size = length; 326 mtx_lock(&shm_timestamp_lock); 327 vfs_timestamp(&shmfd->shm_ctime); 328 shmfd->shm_mtime = shmfd->shm_ctime; 329 mtx_unlock(&shm_timestamp_lock); 330 object->size = nobjsize; 331 VM_OBJECT_UNLOCK(object); 332 return (0); 333 } 334 335 /* 336 * shmfd object management including creation and reference counting 337 * routines. 338 */ 339 static struct shmfd * 340 shm_alloc(struct ucred *ucred, mode_t mode) 341 { 342 struct shmfd *shmfd; 343 344 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 345 shmfd->shm_size = 0; 346 shmfd->shm_uid = ucred->cr_uid; 347 shmfd->shm_gid = ucred->cr_gid; 348 shmfd->shm_mode = mode; 349 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 350 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 351 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 352 VM_OBJECT_LOCK(shmfd->shm_object); 353 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 354 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 355 VM_OBJECT_UNLOCK(shmfd->shm_object); 356 vfs_timestamp(&shmfd->shm_birthtime); 357 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 358 shmfd->shm_birthtime; 359 refcount_init(&shmfd->shm_refs, 1); 360 #ifdef MAC 361 mac_posixshm_init(shmfd); 362 mac_posixshm_create(ucred, shmfd); 363 #endif 364 365 return (shmfd); 366 } 367 368 static struct shmfd * 369 shm_hold(struct shmfd *shmfd) 370 { 371 372 refcount_acquire(&shmfd->shm_refs); 373 return (shmfd); 374 } 375 376 static void 377 shm_drop(struct shmfd *shmfd) 378 { 379 380 if (refcount_release(&shmfd->shm_refs)) { 381 #ifdef MAC 382 mac_posixshm_destroy(shmfd); 383 #endif 384 vm_object_deallocate(shmfd->shm_object); 385 free(shmfd, M_SHMFD); 386 } 387 } 388 389 /* 390 * Determine if the credentials have sufficient permissions for a 391 * specified combination of FREAD and FWRITE. 392 */ 393 static int 394 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 395 { 396 accmode_t accmode; 397 398 accmode = 0; 399 if (flags & FREAD) 400 accmode |= VREAD; 401 if (flags & FWRITE) 402 accmode |= VWRITE; 403 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 404 accmode, ucred, NULL)); 405 } 406 407 /* 408 * Dictionary management. We maintain an in-kernel dictionary to map 409 * paths to shmfd objects. We use the FNV hash on the path to store 410 * the mappings in a hash table. 411 */ 412 static void 413 shm_dict_init(void *arg) 414 { 415 416 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 417 sx_init(&shm_dict_lock, "shm dictionary"); 418 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 419 } 420 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 421 422 static struct shmfd * 423 shm_lookup(char *path, Fnv32_t fnv) 424 { 425 struct shm_mapping *map; 426 427 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 428 if (map->sm_fnv != fnv) 429 continue; 430 if (strcmp(map->sm_path, path) == 0) 431 return (map->sm_shmfd); 432 } 433 434 return (NULL); 435 } 436 437 static void 438 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 439 { 440 struct shm_mapping *map; 441 442 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 443 map->sm_path = path; 444 map->sm_fnv = fnv; 445 map->sm_shmfd = shm_hold(shmfd); 446 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 447 } 448 449 static int 450 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 451 { 452 struct shm_mapping *map; 453 int error; 454 455 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 456 if (map->sm_fnv != fnv) 457 continue; 458 if (strcmp(map->sm_path, path) == 0) { 459 #ifdef MAC 460 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 461 if (error) 462 return (error); 463 #endif 464 error = shm_access(map->sm_shmfd, ucred, 465 FREAD | FWRITE); 466 if (error) 467 return (error); 468 LIST_REMOVE(map, sm_link); 469 shm_drop(map->sm_shmfd); 470 free(map->sm_path, M_SHMFD); 471 free(map, M_SHMFD); 472 return (0); 473 } 474 } 475 476 return (ENOENT); 477 } 478 479 /* System calls. */ 480 int 481 shm_open(struct thread *td, struct shm_open_args *uap) 482 { 483 struct filedesc *fdp; 484 struct shmfd *shmfd; 485 struct file *fp; 486 char *path; 487 Fnv32_t fnv; 488 mode_t cmode; 489 int fd, error; 490 491 if ((uap->flags & O_ACCMODE) != O_RDONLY && 492 (uap->flags & O_ACCMODE) != O_RDWR) 493 return (EINVAL); 494 495 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 496 return (EINVAL); 497 498 fdp = td->td_proc->p_fd; 499 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 500 501 error = falloc(td, &fp, &fd); 502 if (error) 503 return (error); 504 505 /* A SHM_ANON path pointer creates an anonymous object. */ 506 if (uap->path == SHM_ANON) { 507 /* A read-only anonymous object is pointless. */ 508 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 509 fdclose(fdp, fp, fd, td); 510 fdrop(fp, td); 511 return (EINVAL); 512 } 513 shmfd = shm_alloc(td->td_ucred, cmode); 514 } else { 515 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 516 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 517 518 /* Require paths to start with a '/' character. */ 519 if (error == 0 && path[0] != '/') 520 error = EINVAL; 521 if (error) { 522 fdclose(fdp, fp, fd, td); 523 fdrop(fp, td); 524 free(path, M_SHMFD); 525 return (error); 526 } 527 528 fnv = fnv_32_str(path, FNV1_32_INIT); 529 sx_xlock(&shm_dict_lock); 530 shmfd = shm_lookup(path, fnv); 531 if (shmfd == NULL) { 532 /* Object does not yet exist, create it if requested. */ 533 if (uap->flags & O_CREAT) { 534 shmfd = shm_alloc(td->td_ucred, cmode); 535 shm_insert(path, fnv, shmfd); 536 } else { 537 free(path, M_SHMFD); 538 error = ENOENT; 539 } 540 } else { 541 /* 542 * Object already exists, obtain a new 543 * reference if requested and permitted. 544 */ 545 free(path, M_SHMFD); 546 if ((uap->flags & (O_CREAT | O_EXCL)) == 547 (O_CREAT | O_EXCL)) 548 error = EEXIST; 549 else { 550 #ifdef MAC 551 error = mac_posixshm_check_open(td->td_ucred, 552 shmfd); 553 if (error == 0) 554 #endif 555 error = shm_access(shmfd, td->td_ucred, 556 FFLAGS(uap->flags & O_ACCMODE)); 557 } 558 559 /* 560 * Truncate the file back to zero length if 561 * O_TRUNC was specified and the object was 562 * opened with read/write. 563 */ 564 if (error == 0 && 565 (uap->flags & (O_ACCMODE | O_TRUNC)) == 566 (O_RDWR | O_TRUNC)) { 567 #ifdef MAC 568 error = mac_posixshm_check_truncate( 569 td->td_ucred, fp->f_cred, shmfd); 570 if (error == 0) 571 #endif 572 shm_dotruncate(shmfd, 0); 573 } 574 if (error == 0) 575 shm_hold(shmfd); 576 } 577 sx_xunlock(&shm_dict_lock); 578 579 if (error) { 580 fdclose(fdp, fp, fd, td); 581 fdrop(fp, td); 582 return (error); 583 } 584 } 585 586 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 587 588 FILEDESC_XLOCK(fdp); 589 if (fdp->fd_ofiles[fd] == fp) 590 fdp->fd_ofileflags[fd] |= UF_EXCLOSE; 591 FILEDESC_XUNLOCK(fdp); 592 td->td_retval[0] = fd; 593 fdrop(fp, td); 594 595 return (0); 596 } 597 598 int 599 shm_unlink(struct thread *td, struct shm_unlink_args *uap) 600 { 601 char *path; 602 Fnv32_t fnv; 603 int error; 604 605 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 606 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 607 if (error) { 608 free(path, M_TEMP); 609 return (error); 610 } 611 612 fnv = fnv_32_str(path, FNV1_32_INIT); 613 sx_xlock(&shm_dict_lock); 614 error = shm_remove(path, fnv, td->td_ucred); 615 sx_xunlock(&shm_dict_lock); 616 free(path, M_TEMP); 617 618 return (error); 619 } 620 621 /* 622 * mmap() helper to validate mmap() requests against shm object state 623 * and give mmap() the vm_object to use for the mapping. 624 */ 625 int 626 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 627 vm_object_t *obj) 628 { 629 630 /* 631 * XXXRW: This validation is probably insufficient, and subject to 632 * sign errors. It should be fixed. 633 */ 634 if (foff >= shmfd->shm_size || 635 foff + objsize > round_page(shmfd->shm_size)) 636 return (EINVAL); 637 638 mtx_lock(&shm_timestamp_lock); 639 vfs_timestamp(&shmfd->shm_atime); 640 mtx_unlock(&shm_timestamp_lock); 641 vm_object_reference(shmfd->shm_object); 642 *obj = shmfd->shm_object; 643 return (0); 644 } 645