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 "opt_mac.h" 59 60 #include <sys/param.h> 61 #include <sys/fcntl.h> 62 #include <sys/file.h> 63 #include <sys/filedesc.h> 64 #include <sys/fnv_hash.h> 65 #include <sys/kernel.h> 66 #include <sys/lock.h> 67 #include <sys/malloc.h> 68 #include <sys/mman.h> 69 #include <sys/mutex.h> 70 #include <sys/proc.h> 71 #include <sys/refcount.h> 72 #include <sys/resourcevar.h> 73 #include <sys/stat.h> 74 #include <sys/sysctl.h> 75 #include <sys/sysproto.h> 76 #include <sys/systm.h> 77 #include <sys/sx.h> 78 #include <sys/time.h> 79 #include <sys/vnode.h> 80 81 #include <security/mac/mac_framework.h> 82 83 #include <vm/vm.h> 84 #include <vm/vm_param.h> 85 #include <vm/pmap.h> 86 #include <vm/vm_map.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 void 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 shm_dotruncate(shmfd, length); 173 return (0); 174 } 175 176 static int 177 shm_ioctl(struct file *fp, u_long com, void *data, 178 struct ucred *active_cred, struct thread *td) 179 { 180 181 return (EOPNOTSUPP); 182 } 183 184 static int 185 shm_poll(struct file *fp, int events, struct ucred *active_cred, 186 struct thread *td) 187 { 188 189 return (EOPNOTSUPP); 190 } 191 192 static int 193 shm_kqfilter(struct file *fp, struct knote *kn) 194 { 195 196 return (EOPNOTSUPP); 197 } 198 199 static int 200 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 201 struct thread *td) 202 { 203 struct shmfd *shmfd; 204 #ifdef MAC 205 int error; 206 #endif 207 208 shmfd = fp->f_data; 209 210 #ifdef MAC 211 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 212 if (error) 213 return (error); 214 #endif 215 216 /* 217 * Attempt to return sanish values for fstat() on a memory file 218 * descriptor. 219 */ 220 bzero(sb, sizeof(*sb)); 221 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 222 sb->st_blksize = PAGE_SIZE; 223 sb->st_size = shmfd->shm_size; 224 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 225 sb->st_atimespec = shmfd->shm_atime; 226 sb->st_ctimespec = shmfd->shm_ctime; 227 sb->st_mtimespec = shmfd->shm_mtime; 228 sb->st_birthtimespec = shmfd->shm_birthtime; 229 sb->st_uid = shmfd->shm_uid; 230 sb->st_gid = shmfd->shm_gid; 231 232 return (0); 233 } 234 235 static int 236 shm_close(struct file *fp, struct thread *td) 237 { 238 struct shmfd *shmfd; 239 240 shmfd = fp->f_data; 241 fp->f_data = NULL; 242 shm_drop(shmfd); 243 244 return (0); 245 } 246 247 static void 248 shm_dotruncate(struct shmfd *shmfd, off_t length) 249 { 250 vm_object_t object; 251 vm_page_t m; 252 vm_pindex_t nobjsize; 253 254 object = shmfd->shm_object; 255 VM_OBJECT_LOCK(object); 256 if (length == shmfd->shm_size) { 257 VM_OBJECT_UNLOCK(object); 258 return; 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 /* 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, 272 object->size - nobjsize); 273 274 /* 275 * If the last page is partially mapped, then zero out 276 * the garbage at the end of the page. See comments 277 * in vnode_page_setsize() for more details. 278 * 279 * XXXJHB: This handles in memory pages, but what about 280 * a page swapped out to disk? 281 */ 282 if ((length & PAGE_MASK) && 283 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL && 284 m->valid != 0) { 285 int base = (int)length & PAGE_MASK; 286 int size = PAGE_SIZE - base; 287 288 pmap_zero_page_area(m, base, size); 289 vm_page_lock_queues(); 290 vm_page_set_validclean(m, base, size); 291 if (m->dirty != 0) 292 m->dirty = VM_PAGE_BITS_ALL; 293 vm_page_unlock_queues(); 294 } else if ((length & PAGE_MASK) && 295 __predict_false(object->cache != NULL)) { 296 vm_page_cache_free(object, OFF_TO_IDX(length), 297 nobjsize); 298 } 299 } 300 shmfd->shm_size = length; 301 mtx_lock(&shm_timestamp_lock); 302 vfs_timestamp(&shmfd->shm_ctime); 303 shmfd->shm_mtime = shmfd->shm_ctime; 304 mtx_unlock(&shm_timestamp_lock); 305 object->size = nobjsize; 306 VM_OBJECT_UNLOCK(object); 307 } 308 309 /* 310 * shmfd object management including creation and reference counting 311 * routines. 312 */ 313 static struct shmfd * 314 shm_alloc(struct ucred *ucred, mode_t mode) 315 { 316 struct shmfd *shmfd; 317 318 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 319 shmfd->shm_size = 0; 320 shmfd->shm_uid = ucred->cr_uid; 321 shmfd->shm_gid = ucred->cr_gid; 322 shmfd->shm_mode = mode; 323 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 324 shmfd->shm_size, VM_PROT_DEFAULT, 0); 325 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 326 VM_OBJECT_LOCK(shmfd->shm_object); 327 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 328 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 329 VM_OBJECT_UNLOCK(shmfd->shm_object); 330 vfs_timestamp(&shmfd->shm_birthtime); 331 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 332 shmfd->shm_birthtime; 333 refcount_init(&shmfd->shm_refs, 1); 334 #ifdef MAC 335 mac_posixshm_init(shmfd); 336 mac_posixshm_create(ucred, shmfd); 337 #endif 338 339 return (shmfd); 340 } 341 342 static struct shmfd * 343 shm_hold(struct shmfd *shmfd) 344 { 345 346 refcount_acquire(&shmfd->shm_refs); 347 return (shmfd); 348 } 349 350 static void 351 shm_drop(struct shmfd *shmfd) 352 { 353 354 if (refcount_release(&shmfd->shm_refs)) { 355 #ifdef MAC 356 mac_posixshm_destroy(shmfd); 357 #endif 358 vm_object_deallocate(shmfd->shm_object); 359 free(shmfd, M_SHMFD); 360 } 361 } 362 363 /* 364 * Determine if the credentials have sufficient permissions for a 365 * specified combination of FREAD and FWRITE. 366 */ 367 static int 368 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 369 { 370 accmode_t accmode; 371 372 accmode = 0; 373 if (flags & FREAD) 374 accmode |= VREAD; 375 if (flags & FWRITE) 376 accmode |= VWRITE; 377 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 378 accmode, ucred, NULL)); 379 } 380 381 /* 382 * Dictionary management. We maintain an in-kernel dictionary to map 383 * paths to shmfd objects. We use the FNV hash on the path to store 384 * the mappings in a hash table. 385 */ 386 static void 387 shm_dict_init(void *arg) 388 { 389 390 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 391 sx_init(&shm_dict_lock, "shm dictionary"); 392 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 393 } 394 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 395 396 static struct shmfd * 397 shm_lookup(char *path, Fnv32_t fnv) 398 { 399 struct shm_mapping *map; 400 401 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 402 if (map->sm_fnv != fnv) 403 continue; 404 if (strcmp(map->sm_path, path) == 0) 405 return (map->sm_shmfd); 406 } 407 408 return (NULL); 409 } 410 411 static void 412 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 413 { 414 struct shm_mapping *map; 415 416 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 417 map->sm_path = path; 418 map->sm_fnv = fnv; 419 map->sm_shmfd = shm_hold(shmfd); 420 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 421 } 422 423 static int 424 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 425 { 426 struct shm_mapping *map; 427 int error; 428 429 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 430 if (map->sm_fnv != fnv) 431 continue; 432 if (strcmp(map->sm_path, path) == 0) { 433 #ifdef MAC 434 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 435 if (error) 436 return (error); 437 #endif 438 error = shm_access(map->sm_shmfd, ucred, 439 FREAD | FWRITE); 440 if (error) 441 return (error); 442 LIST_REMOVE(map, sm_link); 443 shm_drop(map->sm_shmfd); 444 free(map->sm_path, M_SHMFD); 445 free(map, M_SHMFD); 446 return (0); 447 } 448 } 449 450 return (ENOENT); 451 } 452 453 /* System calls. */ 454 int 455 shm_open(struct thread *td, struct shm_open_args *uap) 456 { 457 struct filedesc *fdp; 458 struct shmfd *shmfd; 459 struct file *fp; 460 char *path; 461 Fnv32_t fnv; 462 mode_t cmode; 463 int fd, error; 464 465 if ((uap->flags & O_ACCMODE) != O_RDONLY && 466 (uap->flags & O_ACCMODE) != O_RDWR) 467 return (EINVAL); 468 469 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 470 return (EINVAL); 471 472 fdp = td->td_proc->p_fd; 473 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 474 475 error = falloc(td, &fp, &fd); 476 if (error) 477 return (error); 478 479 /* A SHM_ANON path pointer creates an anonymous object. */ 480 if (uap->path == SHM_ANON) { 481 /* A read-only anonymous object is pointless. */ 482 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 483 fdclose(fdp, fp, fd, td); 484 fdrop(fp, td); 485 return (EINVAL); 486 } 487 shmfd = shm_alloc(td->td_ucred, cmode); 488 } else { 489 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 490 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 491 492 /* Require paths to start with a '/' character. */ 493 if (error == 0 && path[0] != '/') 494 error = EINVAL; 495 if (error) { 496 fdclose(fdp, fp, fd, td); 497 fdrop(fp, td); 498 free(path, M_SHMFD); 499 return (error); 500 } 501 502 fnv = fnv_32_str(path, FNV1_32_INIT); 503 sx_xlock(&shm_dict_lock); 504 shmfd = shm_lookup(path, fnv); 505 if (shmfd == NULL) { 506 /* Object does not yet exist, create it if requested. */ 507 if (uap->flags & O_CREAT) { 508 shmfd = shm_alloc(td->td_ucred, cmode); 509 shm_insert(path, fnv, shmfd); 510 } else { 511 free(path, M_SHMFD); 512 error = ENOENT; 513 } 514 } else { 515 /* 516 * Object already exists, obtain a new 517 * reference if requested and permitted. 518 */ 519 free(path, M_SHMFD); 520 if ((uap->flags & (O_CREAT | O_EXCL)) == 521 (O_CREAT | O_EXCL)) 522 error = EEXIST; 523 else { 524 #ifdef MAC 525 error = mac_posixshm_check_open(td->td_ucred, 526 shmfd); 527 if (error == 0) 528 #endif 529 error = shm_access(shmfd, td->td_ucred, 530 FFLAGS(uap->flags & O_ACCMODE)); 531 } 532 533 /* 534 * Truncate the file back to zero length if 535 * O_TRUNC was specified and the object was 536 * opened with read/write. 537 */ 538 if (error == 0 && 539 (uap->flags & (O_ACCMODE | O_TRUNC)) == 540 (O_RDWR | O_TRUNC)) { 541 #ifdef MAC 542 error = mac_posixshm_check_truncate( 543 td->td_ucred, fp->f_cred, shmfd); 544 if (error == 0) 545 #endif 546 shm_dotruncate(shmfd, 0); 547 } 548 if (error == 0) 549 shm_hold(shmfd); 550 } 551 sx_xunlock(&shm_dict_lock); 552 553 if (error) { 554 fdclose(fdp, fp, fd, td); 555 fdrop(fp, td); 556 return (error); 557 } 558 } 559 560 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 561 562 FILEDESC_XLOCK(fdp); 563 if (fdp->fd_ofiles[fd] == fp) 564 fdp->fd_ofileflags[fd] |= UF_EXCLOSE; 565 FILEDESC_XUNLOCK(fdp); 566 td->td_retval[0] = fd; 567 fdrop(fp, td); 568 569 return (0); 570 } 571 572 int 573 shm_unlink(struct thread *td, struct shm_unlink_args *uap) 574 { 575 char *path; 576 Fnv32_t fnv; 577 int error; 578 579 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 580 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 581 if (error) { 582 free(path, M_TEMP); 583 return (error); 584 } 585 586 fnv = fnv_32_str(path, FNV1_32_INIT); 587 sx_xlock(&shm_dict_lock); 588 error = shm_remove(path, fnv, td->td_ucred); 589 sx_xunlock(&shm_dict_lock); 590 free(path, M_TEMP); 591 592 return (error); 593 } 594 595 /* 596 * mmap() helper to validate mmap() requests against shm object state 597 * and give mmap() the vm_object to use for the mapping. 598 */ 599 int 600 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 601 vm_object_t *obj) 602 { 603 604 /* 605 * XXXRW: This validation is probably insufficient, and subject to 606 * sign errors. It should be fixed. 607 */ 608 if (foff >= shmfd->shm_size || 609 foff + objsize > round_page(shmfd->shm_size)) 610 return (EINVAL); 611 612 mtx_lock(&shm_timestamp_lock); 613 vfs_timestamp(&shmfd->shm_atime); 614 mtx_unlock(&shm_timestamp_lock); 615 vm_object_reference(shmfd->shm_object); 616 *obj = shmfd->shm_object; 617 return (0); 618 } 619