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_atim = shmfd->shm_atime; 223 sb->st_ctim = shmfd->shm_ctime; 224 sb->st_mtim = shmfd->shm_mtime; 225 sb->st_birthtim = 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_clear_dirty(m, base, PAGE_SIZE - base); 308 } else if ((length & PAGE_MASK) && 309 __predict_false(object->cache != NULL)) { 310 vm_page_cache_free(object, OFF_TO_IDX(length), 311 nobjsize); 312 } 313 } else { 314 315 /* Attempt to reserve the swap */ 316 delta = ptoa(nobjsize - object->size); 317 if (!swap_reserve_by_uid(delta, object->uip)) { 318 VM_OBJECT_UNLOCK(object); 319 return (ENOMEM); 320 } 321 object->charge += delta; 322 } 323 shmfd->shm_size = length; 324 mtx_lock(&shm_timestamp_lock); 325 vfs_timestamp(&shmfd->shm_ctime); 326 shmfd->shm_mtime = shmfd->shm_ctime; 327 mtx_unlock(&shm_timestamp_lock); 328 object->size = nobjsize; 329 VM_OBJECT_UNLOCK(object); 330 return (0); 331 } 332 333 /* 334 * shmfd object management including creation and reference counting 335 * routines. 336 */ 337 static struct shmfd * 338 shm_alloc(struct ucred *ucred, mode_t mode) 339 { 340 struct shmfd *shmfd; 341 342 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 343 shmfd->shm_size = 0; 344 shmfd->shm_uid = ucred->cr_uid; 345 shmfd->shm_gid = ucred->cr_gid; 346 shmfd->shm_mode = mode; 347 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 348 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 349 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 350 VM_OBJECT_LOCK(shmfd->shm_object); 351 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 352 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 353 VM_OBJECT_UNLOCK(shmfd->shm_object); 354 vfs_timestamp(&shmfd->shm_birthtime); 355 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 356 shmfd->shm_birthtime; 357 refcount_init(&shmfd->shm_refs, 1); 358 #ifdef MAC 359 mac_posixshm_init(shmfd); 360 mac_posixshm_create(ucred, shmfd); 361 #endif 362 363 return (shmfd); 364 } 365 366 static struct shmfd * 367 shm_hold(struct shmfd *shmfd) 368 { 369 370 refcount_acquire(&shmfd->shm_refs); 371 return (shmfd); 372 } 373 374 static void 375 shm_drop(struct shmfd *shmfd) 376 { 377 378 if (refcount_release(&shmfd->shm_refs)) { 379 #ifdef MAC 380 mac_posixshm_destroy(shmfd); 381 #endif 382 vm_object_deallocate(shmfd->shm_object); 383 free(shmfd, M_SHMFD); 384 } 385 } 386 387 /* 388 * Determine if the credentials have sufficient permissions for a 389 * specified combination of FREAD and FWRITE. 390 */ 391 static int 392 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 393 { 394 accmode_t accmode; 395 396 accmode = 0; 397 if (flags & FREAD) 398 accmode |= VREAD; 399 if (flags & FWRITE) 400 accmode |= VWRITE; 401 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 402 accmode, ucred, NULL)); 403 } 404 405 /* 406 * Dictionary management. We maintain an in-kernel dictionary to map 407 * paths to shmfd objects. We use the FNV hash on the path to store 408 * the mappings in a hash table. 409 */ 410 static void 411 shm_dict_init(void *arg) 412 { 413 414 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 415 sx_init(&shm_dict_lock, "shm dictionary"); 416 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 417 } 418 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 419 420 static struct shmfd * 421 shm_lookup(char *path, Fnv32_t fnv) 422 { 423 struct shm_mapping *map; 424 425 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 426 if (map->sm_fnv != fnv) 427 continue; 428 if (strcmp(map->sm_path, path) == 0) 429 return (map->sm_shmfd); 430 } 431 432 return (NULL); 433 } 434 435 static void 436 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 437 { 438 struct shm_mapping *map; 439 440 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 441 map->sm_path = path; 442 map->sm_fnv = fnv; 443 map->sm_shmfd = shm_hold(shmfd); 444 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 445 } 446 447 static int 448 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 449 { 450 struct shm_mapping *map; 451 int error; 452 453 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 454 if (map->sm_fnv != fnv) 455 continue; 456 if (strcmp(map->sm_path, path) == 0) { 457 #ifdef MAC 458 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 459 if (error) 460 return (error); 461 #endif 462 error = shm_access(map->sm_shmfd, ucred, 463 FREAD | FWRITE); 464 if (error) 465 return (error); 466 LIST_REMOVE(map, sm_link); 467 shm_drop(map->sm_shmfd); 468 free(map->sm_path, M_SHMFD); 469 free(map, M_SHMFD); 470 return (0); 471 } 472 } 473 474 return (ENOENT); 475 } 476 477 /* System calls. */ 478 int 479 shm_open(struct thread *td, struct shm_open_args *uap) 480 { 481 struct filedesc *fdp; 482 struct shmfd *shmfd; 483 struct file *fp; 484 char *path; 485 Fnv32_t fnv; 486 mode_t cmode; 487 int fd, error; 488 489 if ((uap->flags & O_ACCMODE) != O_RDONLY && 490 (uap->flags & O_ACCMODE) != O_RDWR) 491 return (EINVAL); 492 493 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 494 return (EINVAL); 495 496 fdp = td->td_proc->p_fd; 497 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 498 499 error = falloc(td, &fp, &fd); 500 if (error) 501 return (error); 502 503 /* A SHM_ANON path pointer creates an anonymous object. */ 504 if (uap->path == SHM_ANON) { 505 /* A read-only anonymous object is pointless. */ 506 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 507 fdclose(fdp, fp, fd, td); 508 fdrop(fp, td); 509 return (EINVAL); 510 } 511 shmfd = shm_alloc(td->td_ucred, cmode); 512 } else { 513 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 514 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 515 516 /* Require paths to start with a '/' character. */ 517 if (error == 0 && path[0] != '/') 518 error = EINVAL; 519 if (error) { 520 fdclose(fdp, fp, fd, td); 521 fdrop(fp, td); 522 free(path, M_SHMFD); 523 return (error); 524 } 525 526 fnv = fnv_32_str(path, FNV1_32_INIT); 527 sx_xlock(&shm_dict_lock); 528 shmfd = shm_lookup(path, fnv); 529 if (shmfd == NULL) { 530 /* Object does not yet exist, create it if requested. */ 531 if (uap->flags & O_CREAT) { 532 shmfd = shm_alloc(td->td_ucred, cmode); 533 shm_insert(path, fnv, shmfd); 534 } else { 535 free(path, M_SHMFD); 536 error = ENOENT; 537 } 538 } else { 539 /* 540 * Object already exists, obtain a new 541 * reference if requested and permitted. 542 */ 543 free(path, M_SHMFD); 544 if ((uap->flags & (O_CREAT | O_EXCL)) == 545 (O_CREAT | O_EXCL)) 546 error = EEXIST; 547 else { 548 #ifdef MAC 549 error = mac_posixshm_check_open(td->td_ucred, 550 shmfd); 551 if (error == 0) 552 #endif 553 error = shm_access(shmfd, td->td_ucred, 554 FFLAGS(uap->flags & O_ACCMODE)); 555 } 556 557 /* 558 * Truncate the file back to zero length if 559 * O_TRUNC was specified and the object was 560 * opened with read/write. 561 */ 562 if (error == 0 && 563 (uap->flags & (O_ACCMODE | O_TRUNC)) == 564 (O_RDWR | O_TRUNC)) { 565 #ifdef MAC 566 error = mac_posixshm_check_truncate( 567 td->td_ucred, fp->f_cred, shmfd); 568 if (error == 0) 569 #endif 570 shm_dotruncate(shmfd, 0); 571 } 572 if (error == 0) 573 shm_hold(shmfd); 574 } 575 sx_xunlock(&shm_dict_lock); 576 577 if (error) { 578 fdclose(fdp, fp, fd, td); 579 fdrop(fp, td); 580 return (error); 581 } 582 } 583 584 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 585 586 FILEDESC_XLOCK(fdp); 587 if (fdp->fd_ofiles[fd] == fp) 588 fdp->fd_ofileflags[fd] |= UF_EXCLOSE; 589 FILEDESC_XUNLOCK(fdp); 590 td->td_retval[0] = fd; 591 fdrop(fp, td); 592 593 return (0); 594 } 595 596 int 597 shm_unlink(struct thread *td, struct shm_unlink_args *uap) 598 { 599 char *path; 600 Fnv32_t fnv; 601 int error; 602 603 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 604 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 605 if (error) { 606 free(path, M_TEMP); 607 return (error); 608 } 609 610 fnv = fnv_32_str(path, FNV1_32_INIT); 611 sx_xlock(&shm_dict_lock); 612 error = shm_remove(path, fnv, td->td_ucred); 613 sx_xunlock(&shm_dict_lock); 614 free(path, M_TEMP); 615 616 return (error); 617 } 618 619 /* 620 * mmap() helper to validate mmap() requests against shm object state 621 * and give mmap() the vm_object to use for the mapping. 622 */ 623 int 624 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 625 vm_object_t *obj) 626 { 627 628 /* 629 * XXXRW: This validation is probably insufficient, and subject to 630 * sign errors. It should be fixed. 631 */ 632 if (foff >= shmfd->shm_size || 633 foff + objsize > round_page(shmfd->shm_size)) 634 return (EINVAL); 635 636 mtx_lock(&shm_timestamp_lock); 637 vfs_timestamp(&shmfd->shm_atime); 638 mtx_unlock(&shm_timestamp_lock); 639 vm_object_reference(shmfd->shm_object); 640 *obj = shmfd->shm_object; 641 return (0); 642 } 643