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 * (1) Convert test utilities into regression tests and import them into 35 * src/tools/regression. 36 * 37 * (2) Need to export data to a userland tool via a sysctl. Should ipcs(1) 38 * and ipcrm(1) be expanded or should new tools to manage both POSIX 39 * kernel semaphores and POSIX shared memory be written? 40 * 41 * (3) Add support for this file type to fstat(1). 42 * 43 * (4) Resource limits? Does this need its own resource limits or are the 44 * existing limits in mmap(2) sufficient? 45 * 46 * (5) Partial page truncation. vnode_pager_setsize() will zero any parts 47 * of a partially mapped page as a result of ftruncate(2)/truncate(2). 48 * We can do the same (with the same pmap evil), but do we need to 49 * worry about the bits on disk if the page is swapped out or will the 50 * swapper zero the parts of a page that are invalid if the page is 51 * swapped back in for us? 52 */ 53 54 #include <sys/cdefs.h> 55 __FBSDID("$FreeBSD$"); 56 57 #include "opt_mac.h" 58 59 #include <sys/param.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_map.h> 86 #include <vm/vm_object.h> 87 #include <vm/vm_page.h> 88 #include <vm/vm_pager.h> 89 #include <vm/swap_pager.h> 90 91 struct shm_mapping { 92 char *sm_path; 93 Fnv32_t sm_fnv; 94 struct shmfd *sm_shmfd; 95 LIST_ENTRY(shm_mapping) sm_link; 96 }; 97 98 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 99 static LIST_HEAD(, shm_mapping) *shm_dictionary; 100 static struct sx shm_dict_lock; 101 static struct mtx shm_timestamp_lock; 102 static u_long shm_hash; 103 104 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 105 106 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 107 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 108 static void shm_dict_init(void *arg); 109 static void shm_drop(struct shmfd *shmfd); 110 static struct shmfd *shm_hold(struct shmfd *shmfd); 111 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 112 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 113 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 114 static void shm_dotruncate(struct shmfd *shmfd, off_t length); 115 116 static fo_rdwr_t shm_read; 117 static fo_rdwr_t shm_write; 118 static fo_truncate_t shm_truncate; 119 static fo_ioctl_t shm_ioctl; 120 static fo_poll_t shm_poll; 121 static fo_kqfilter_t shm_kqfilter; 122 static fo_stat_t shm_stat; 123 static fo_close_t shm_close; 124 125 /* File descriptor operations. */ 126 static struct fileops shm_ops = { 127 .fo_read = shm_read, 128 .fo_write = shm_write, 129 .fo_truncate = shm_truncate, 130 .fo_ioctl = shm_ioctl, 131 .fo_poll = shm_poll, 132 .fo_kqfilter = shm_kqfilter, 133 .fo_stat = shm_stat, 134 .fo_close = shm_close, 135 .fo_flags = DFLAG_PASSABLE 136 }; 137 138 FEATURE(posix_shm, "POSIX shared memory"); 139 140 static int 141 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 142 int flags, struct thread *td) 143 { 144 145 return (EOPNOTSUPP); 146 } 147 148 static int 149 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 150 int flags, struct thread *td) 151 { 152 153 return (EOPNOTSUPP); 154 } 155 156 static int 157 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 158 struct thread *td) 159 { 160 struct shmfd *shmfd; 161 #ifdef MAC 162 int error; 163 #endif 164 165 shmfd = fp->f_data; 166 #ifdef MAC 167 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 168 if (error) 169 return (error); 170 #endif 171 shm_dotruncate(shmfd, length); 172 return (0); 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 void 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; 252 253 object = shmfd->shm_object; 254 VM_OBJECT_LOCK(object); 255 if (length == shmfd->shm_size) { 256 VM_OBJECT_UNLOCK(object); 257 return; 258 } 259 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 260 261 /* Are we shrinking? If so, trim the end. */ 262 if (length < shmfd->shm_size) { 263 /* Toss in memory pages. */ 264 if (nobjsize < object->size) 265 vm_object_page_remove(object, nobjsize, object->size, 266 FALSE); 267 268 /* Toss pages from swap. */ 269 if (object->type == OBJT_SWAP) 270 swap_pager_freespace(object, nobjsize, 271 object->size - nobjsize); 272 273 /* 274 * If the last page is partially mapped, then zero out 275 * the garbage at the end of the page. See comments 276 * in vnode_page_setsize() for more details. 277 * 278 * XXXJHB: This handles in memory pages, but what about 279 * a page swapped out to disk? 280 */ 281 if ((length & PAGE_MASK) && 282 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL && 283 m->valid != 0) { 284 int base = (int)length & PAGE_MASK; 285 int size = PAGE_SIZE - base; 286 287 pmap_zero_page_area(m, base, size); 288 vm_page_lock_queues(); 289 vm_page_set_validclean(m, base, size); 290 if (m->dirty != 0) 291 m->dirty = VM_PAGE_BITS_ALL; 292 vm_page_unlock_queues(); 293 } 294 } 295 shmfd->shm_size = length; 296 mtx_lock(&shm_timestamp_lock); 297 vfs_timestamp(&shmfd->shm_ctime); 298 shmfd->shm_mtime = shmfd->shm_ctime; 299 mtx_unlock(&shm_timestamp_lock); 300 object->size = nobjsize; 301 VM_OBJECT_UNLOCK(object); 302 } 303 304 /* 305 * shmfd object management including creation and reference counting 306 * routines. 307 */ 308 static struct shmfd * 309 shm_alloc(struct ucred *ucred, mode_t mode) 310 { 311 struct shmfd *shmfd; 312 313 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 314 shmfd->shm_size = 0; 315 shmfd->shm_uid = ucred->cr_uid; 316 shmfd->shm_gid = ucred->cr_gid; 317 shmfd->shm_mode = mode; 318 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 319 shmfd->shm_size, VM_PROT_DEFAULT, 0); 320 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 321 vfs_timestamp(&shmfd->shm_birthtime); 322 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 323 shmfd->shm_birthtime; 324 refcount_init(&shmfd->shm_refs, 1); 325 #ifdef MAC 326 mac_posixshm_init(shmfd); 327 mac_posixshm_create(ucred, shmfd); 328 #endif 329 330 return (shmfd); 331 } 332 333 static struct shmfd * 334 shm_hold(struct shmfd *shmfd) 335 { 336 337 refcount_acquire(&shmfd->shm_refs); 338 return (shmfd); 339 } 340 341 static void 342 shm_drop(struct shmfd *shmfd) 343 { 344 345 if (refcount_release(&shmfd->shm_refs)) { 346 #ifdef MAC 347 mac_posixshm_destroy(shmfd); 348 #endif 349 vm_object_deallocate(shmfd->shm_object); 350 free(shmfd, M_SHMFD); 351 } 352 } 353 354 /* 355 * Determine if the credentials have sufficient permissions for a 356 * specified combination of FREAD and FWRITE. 357 */ 358 static int 359 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 360 { 361 int acc_mode; 362 363 acc_mode = 0; 364 if (flags & FREAD) 365 acc_mode |= VREAD; 366 if (flags & FWRITE) 367 acc_mode |= VWRITE; 368 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 369 acc_mode, ucred, NULL)); 370 } 371 372 /* 373 * Dictionary management. We maintain an in-kernel dictionary to map 374 * paths to shmfd objects. We use the FNV hash on the path to store 375 * the mappings in a hash table. 376 */ 377 static void 378 shm_dict_init(void *arg) 379 { 380 381 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 382 sx_init(&shm_dict_lock, "shm dictionary"); 383 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 384 } 385 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 386 387 static struct shmfd * 388 shm_lookup(char *path, Fnv32_t fnv) 389 { 390 struct shm_mapping *map; 391 392 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 393 if (map->sm_fnv != fnv) 394 continue; 395 if (strcmp(map->sm_path, path) == 0) 396 return (map->sm_shmfd); 397 } 398 399 return (NULL); 400 } 401 402 static void 403 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 404 { 405 struct shm_mapping *map; 406 407 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 408 map->sm_path = path; 409 map->sm_fnv = fnv; 410 map->sm_shmfd = shm_hold(shmfd); 411 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 412 } 413 414 static int 415 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 416 { 417 struct shm_mapping *map; 418 int error; 419 420 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 421 if (map->sm_fnv != fnv) 422 continue; 423 if (strcmp(map->sm_path, path) == 0) { 424 #ifdef MAC 425 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 426 if (error) 427 return (error); 428 #endif 429 error = shm_access(map->sm_shmfd, ucred, 430 FREAD | FWRITE); 431 if (error) 432 return (error); 433 LIST_REMOVE(map, sm_link); 434 shm_drop(map->sm_shmfd); 435 free(map->sm_path, M_SHMFD); 436 free(map, M_SHMFD); 437 return (0); 438 } 439 } 440 441 return (ENOENT); 442 } 443 444 /* System calls. */ 445 int 446 shm_open(struct thread *td, struct shm_open_args *uap) 447 { 448 struct filedesc *fdp; 449 struct shmfd *shmfd; 450 struct file *fp; 451 char *path; 452 Fnv32_t fnv; 453 mode_t cmode; 454 int fd, error; 455 456 if ((uap->flags & O_ACCMODE) != O_RDONLY && 457 (uap->flags & O_ACCMODE) != O_RDWR) 458 return (EINVAL); 459 460 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 461 return (EINVAL); 462 463 fdp = td->td_proc->p_fd; 464 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 465 466 error = falloc(td, &fp, &fd); 467 if (error) 468 return (error); 469 470 /* A SHM_ANON path pointer creates an anonymous object. */ 471 if (uap->path == SHM_ANON) { 472 /* A read-only anonymous object is pointless. */ 473 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 474 fdclose(fdp, fp, fd, td); 475 fdrop(fp, td); 476 return (EINVAL); 477 } 478 shmfd = shm_alloc(td->td_ucred, cmode); 479 } else { 480 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 481 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 482 483 /* Require paths to start with a '/' character. */ 484 if (error == 0 && path[0] != '/') 485 error = EINVAL; 486 if (error) { 487 fdclose(fdp, fp, fd, td); 488 fdrop(fp, td); 489 free(path, M_SHMFD); 490 return (error); 491 } 492 493 fnv = fnv_32_str(path, FNV1_32_INIT); 494 sx_xlock(&shm_dict_lock); 495 shmfd = shm_lookup(path, fnv); 496 if (shmfd == NULL) { 497 /* Object does not yet exist, create it if requested. */ 498 if (uap->flags & O_CREAT) { 499 shmfd = shm_alloc(td->td_ucred, cmode); 500 shm_insert(path, fnv, shmfd); 501 } else { 502 free(path, M_SHMFD); 503 error = ENOENT; 504 } 505 } else { 506 /* 507 * Object already exists, obtain a new 508 * reference if requested and permitted. 509 */ 510 free(path, M_SHMFD); 511 if ((uap->flags & (O_CREAT | O_EXCL)) == 512 (O_CREAT | O_EXCL)) 513 error = EEXIST; 514 else { 515 #ifdef MAC 516 error = mac_posixshm_check_open(td->td_ucred, 517 shmfd); 518 if (error == 0) 519 #endif 520 error = shm_access(shmfd, td->td_ucred, 521 FFLAGS(uap->flags & O_ACCMODE)); 522 } 523 524 /* 525 * Truncate the file back to zero length if 526 * O_TRUNC was specified and the object was 527 * opened with read/write. 528 */ 529 if (error == 0 && 530 (uap->flags & (O_ACCMODE | O_TRUNC)) == 531 (O_RDWR | O_TRUNC)) { 532 #ifdef MAC 533 error = mac_posixshm_check_truncate( 534 td->td_ucred, fp->f_cred, shmfd); 535 if (error == 0) 536 #endif 537 shm_dotruncate(shmfd, 0); 538 } 539 if (error == 0) 540 shm_hold(shmfd); 541 } 542 sx_xunlock(&shm_dict_lock); 543 544 if (error) { 545 fdclose(fdp, fp, fd, td); 546 fdrop(fp, td); 547 return (error); 548 } 549 } 550 551 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 552 553 FILEDESC_XLOCK(fdp); 554 if (fdp->fd_ofiles[fd] == fp) 555 fdp->fd_ofileflags[fd] |= UF_EXCLOSE; 556 FILEDESC_XUNLOCK(fdp); 557 td->td_retval[0] = fd; 558 fdrop(fp, td); 559 560 return (0); 561 } 562 563 int 564 shm_unlink(struct thread *td, struct shm_unlink_args *uap) 565 { 566 char *path; 567 Fnv32_t fnv; 568 int error; 569 570 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 571 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 572 if (error) { 573 free(path, M_TEMP); 574 return (error); 575 } 576 577 fnv = fnv_32_str(path, FNV1_32_INIT); 578 sx_xlock(&shm_dict_lock); 579 error = shm_remove(path, fnv, td->td_ucred); 580 sx_xunlock(&shm_dict_lock); 581 free(path, M_TEMP); 582 583 return (error); 584 } 585 586 /* 587 * mmap() helper to validate mmap() requests against shm object state 588 * and give mmap() the vm_object to use for the mapping. 589 */ 590 int 591 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 592 vm_object_t *obj) 593 { 594 595 /* 596 * XXXRW: This validation is probably insufficient, and subject to 597 * sign errors. It should be fixed. 598 */ 599 if (foff >= shmfd->shm_size || foff + objsize > shmfd->shm_size) 600 return (EINVAL); 601 602 mtx_lock(&shm_timestamp_lock); 603 vfs_timestamp(&shmfd->shm_atime); 604 mtx_unlock(&shm_timestamp_lock); 605 vm_object_reference(shmfd->shm_object); 606 *obj = shmfd->shm_object; 607 return (0); 608 } 609