uipc_shm.c revision 280258
1/*- 2 * Copyright (c) 2006, 2011 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) 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 * (2) Add support for this file type to fstat(1). 39 * 40 * (3) Resource limits? Does this need its own resource limits or are the 41 * existing limits in mmap(2) sufficient? 42 */ 43 44#include <sys/cdefs.h> 45__FBSDID("$FreeBSD: stable/10/sys/kern/uipc_shm.c 280258 2015-03-19 13:37:36Z rwatson $"); 46 47#include "opt_capsicum.h" 48#include "opt_ktrace.h" 49 50#include <sys/param.h> 51#include <sys/capsicum.h> 52#include <sys/conf.h> 53#include <sys/fcntl.h> 54#include <sys/file.h> 55#include <sys/filedesc.h> 56#include <sys/fnv_hash.h> 57#include <sys/kernel.h> 58#include <sys/uio.h> 59#include <sys/signal.h> 60#include <sys/ktrace.h> 61#include <sys/lock.h> 62#include <sys/malloc.h> 63#include <sys/mman.h> 64#include <sys/mutex.h> 65#include <sys/priv.h> 66#include <sys/proc.h> 67#include <sys/refcount.h> 68#include <sys/resourcevar.h> 69#include <sys/rwlock.h> 70#include <sys/stat.h> 71#include <sys/sysctl.h> 72#include <sys/sysproto.h> 73#include <sys/systm.h> 74#include <sys/sx.h> 75#include <sys/time.h> 76#include <sys/vnode.h> 77#include <sys/unistd.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_extern.h> 85#include <vm/vm_map.h> 86#include <vm/vm_kern.h> 87#include <vm/vm_object.h> 88#include <vm/vm_page.h> 89#include <vm/vm_pageout.h> 90#include <vm/vm_pager.h> 91#include <vm/swap_pager.h> 92 93struct 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 100static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 101static LIST_HEAD(, shm_mapping) *shm_dictionary; 102static struct sx shm_dict_lock; 103static struct mtx shm_timestamp_lock; 104static u_long shm_hash; 105static struct unrhdr *shm_ino_unr; 106static dev_t shm_dev_ino; 107 108#define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 109 110static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 111static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 112static void shm_init(void *arg); 113static void shm_drop(struct shmfd *shmfd); 114static struct shmfd *shm_hold(struct shmfd *shmfd); 115static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 116static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 117static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 118static int shm_dotruncate(struct shmfd *shmfd, off_t length); 119 120static fo_rdwr_t shm_read; 121static fo_rdwr_t shm_write; 122static fo_truncate_t shm_truncate; 123static fo_ioctl_t shm_ioctl; 124static fo_poll_t shm_poll; 125static fo_kqfilter_t shm_kqfilter; 126static fo_stat_t shm_stat; 127static fo_close_t shm_close; 128static fo_chmod_t shm_chmod; 129static fo_chown_t shm_chown; 130static fo_seek_t shm_seek; 131 132/* File descriptor operations. */ 133static struct fileops shm_ops = { 134 .fo_read = shm_read, 135 .fo_write = shm_write, 136 .fo_truncate = shm_truncate, 137 .fo_ioctl = shm_ioctl, 138 .fo_poll = shm_poll, 139 .fo_kqfilter = shm_kqfilter, 140 .fo_stat = shm_stat, 141 .fo_close = shm_close, 142 .fo_chmod = shm_chmod, 143 .fo_chown = shm_chown, 144 .fo_sendfile = vn_sendfile, 145 .fo_seek = shm_seek, 146 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE 147}; 148 149FEATURE(posix_shm, "POSIX shared memory"); 150 151static int 152uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio) 153{ 154 vm_page_t m; 155 vm_pindex_t idx; 156 size_t tlen; 157 int error, offset, rv; 158 159 idx = OFF_TO_IDX(uio->uio_offset); 160 offset = uio->uio_offset & PAGE_MASK; 161 tlen = MIN(PAGE_SIZE - offset, len); 162 163 VM_OBJECT_WLOCK(obj); 164 165 /* 166 * Parallel reads of the page content from disk are prevented 167 * by exclusive busy. 168 * 169 * Although the tmpfs vnode lock is held here, it is 170 * nonetheless safe to sleep waiting for a free page. The 171 * pageout daemon does not need to acquire the tmpfs vnode 172 * lock to page out tobj's pages because tobj is a OBJT_SWAP 173 * type object. 174 */ 175 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL); 176 if (m->valid != VM_PAGE_BITS_ALL) { 177 if (vm_pager_has_page(obj, idx, NULL, NULL)) { 178 rv = vm_pager_get_pages(obj, &m, 1, 0); 179 m = vm_page_lookup(obj, idx); 180 if (m == NULL) { 181 printf( 182 "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n", 183 obj, idx, rv); 184 VM_OBJECT_WUNLOCK(obj); 185 return (EIO); 186 } 187 if (rv != VM_PAGER_OK) { 188 printf( 189 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n", 190 obj, idx, m->valid, rv); 191 vm_page_lock(m); 192 vm_page_free(m); 193 vm_page_unlock(m); 194 VM_OBJECT_WUNLOCK(obj); 195 return (EIO); 196 } 197 } else 198 vm_page_zero_invalid(m, TRUE); 199 } 200 vm_page_xunbusy(m); 201 vm_page_lock(m); 202 vm_page_hold(m); 203 if (m->queue == PQ_NONE) { 204 vm_page_deactivate(m); 205 } else { 206 /* Requeue to maintain LRU ordering. */ 207 vm_page_requeue(m); 208 } 209 vm_page_unlock(m); 210 VM_OBJECT_WUNLOCK(obj); 211 error = uiomove_fromphys(&m, offset, tlen, uio); 212 if (uio->uio_rw == UIO_WRITE && error == 0) { 213 VM_OBJECT_WLOCK(obj); 214 vm_page_dirty(m); 215 vm_pager_page_unswapped(m); 216 VM_OBJECT_WUNLOCK(obj); 217 } 218 vm_page_lock(m); 219 vm_page_unhold(m); 220 vm_page_unlock(m); 221 222 return (error); 223} 224 225int 226uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio) 227{ 228 ssize_t resid; 229 size_t len; 230 int error; 231 232 error = 0; 233 while ((resid = uio->uio_resid) > 0) { 234 if (obj_size <= uio->uio_offset) 235 break; 236 len = MIN(obj_size - uio->uio_offset, resid); 237 if (len == 0) 238 break; 239 error = uiomove_object_page(obj, len, uio); 240 if (error != 0 || resid == uio->uio_resid) 241 break; 242 } 243 return (error); 244} 245 246static int 247shm_seek(struct file *fp, off_t offset, int whence, struct thread *td) 248{ 249 struct shmfd *shmfd; 250 off_t foffset; 251 int error; 252 253 shmfd = fp->f_data; 254 foffset = foffset_lock(fp, 0); 255 error = 0; 256 switch (whence) { 257 case L_INCR: 258 if (foffset < 0 || 259 (offset > 0 && foffset > OFF_MAX - offset)) { 260 error = EOVERFLOW; 261 break; 262 } 263 offset += foffset; 264 break; 265 case L_XTND: 266 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) { 267 error = EOVERFLOW; 268 break; 269 } 270 offset += shmfd->shm_size; 271 break; 272 case L_SET: 273 break; 274 default: 275 error = EINVAL; 276 } 277 if (error == 0) { 278 if (offset < 0 || offset > shmfd->shm_size) 279 error = EINVAL; 280 else 281 *(off_t *)(td->td_retval) = offset; 282 } 283 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0); 284 return (error); 285} 286 287static int 288shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 289 int flags, struct thread *td) 290{ 291 struct shmfd *shmfd; 292 void *rl_cookie; 293 int error; 294 295 shmfd = fp->f_data; 296 foffset_lock_uio(fp, uio, flags); 297 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset, 298 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 299#ifdef MAC 300 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd); 301 if (error) 302 return (error); 303#endif 304 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 305 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 306 foffset_unlock_uio(fp, uio, flags); 307 return (error); 308} 309 310static int 311shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 312 int flags, struct thread *td) 313{ 314 struct shmfd *shmfd; 315 void *rl_cookie; 316 int error; 317 318 shmfd = fp->f_data; 319#ifdef MAC 320 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd); 321 if (error) 322 return (error); 323#endif 324 foffset_lock_uio(fp, uio, flags); 325 if ((flags & FOF_OFFSET) == 0) { 326 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX, 327 &shmfd->shm_mtx); 328 } else { 329 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset, 330 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 331 } 332 333 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 334 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 335 foffset_unlock_uio(fp, uio, flags); 336 return (error); 337} 338 339static int 340shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 341 struct thread *td) 342{ 343 struct shmfd *shmfd; 344#ifdef MAC 345 int error; 346#endif 347 348 shmfd = fp->f_data; 349#ifdef MAC 350 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 351 if (error) 352 return (error); 353#endif 354 return (shm_dotruncate(shmfd, length)); 355} 356 357static int 358shm_ioctl(struct file *fp, u_long com, void *data, 359 struct ucred *active_cred, struct thread *td) 360{ 361 362 return (EOPNOTSUPP); 363} 364 365static int 366shm_poll(struct file *fp, int events, struct ucred *active_cred, 367 struct thread *td) 368{ 369 370 return (EOPNOTSUPP); 371} 372 373static int 374shm_kqfilter(struct file *fp, struct knote *kn) 375{ 376 377 return (EOPNOTSUPP); 378} 379 380static int 381shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 382 struct thread *td) 383{ 384 struct shmfd *shmfd; 385#ifdef MAC 386 int error; 387#endif 388 389 shmfd = fp->f_data; 390 391#ifdef MAC 392 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 393 if (error) 394 return (error); 395#endif 396 397 /* 398 * Attempt to return sanish values for fstat() on a memory file 399 * descriptor. 400 */ 401 bzero(sb, sizeof(*sb)); 402 sb->st_blksize = PAGE_SIZE; 403 sb->st_size = shmfd->shm_size; 404 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 405 mtx_lock(&shm_timestamp_lock); 406 sb->st_atim = shmfd->shm_atime; 407 sb->st_ctim = shmfd->shm_ctime; 408 sb->st_mtim = shmfd->shm_mtime; 409 sb->st_birthtim = shmfd->shm_birthtime; 410 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 411 sb->st_uid = shmfd->shm_uid; 412 sb->st_gid = shmfd->shm_gid; 413 mtx_unlock(&shm_timestamp_lock); 414 sb->st_dev = shm_dev_ino; 415 sb->st_ino = shmfd->shm_ino; 416 417 return (0); 418} 419 420static int 421shm_close(struct file *fp, struct thread *td) 422{ 423 struct shmfd *shmfd; 424 425 shmfd = fp->f_data; 426 fp->f_data = NULL; 427 shm_drop(shmfd); 428 429 return (0); 430} 431 432static int 433shm_dotruncate(struct shmfd *shmfd, off_t length) 434{ 435 vm_object_t object; 436 vm_page_t m, ma[1]; 437 vm_pindex_t idx, nobjsize; 438 vm_ooffset_t delta; 439 int base, rv; 440 441 object = shmfd->shm_object; 442 VM_OBJECT_WLOCK(object); 443 if (length == shmfd->shm_size) { 444 VM_OBJECT_WUNLOCK(object); 445 return (0); 446 } 447 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 448 449 /* Are we shrinking? If so, trim the end. */ 450 if (length < shmfd->shm_size) { 451 /* 452 * Disallow any requests to shrink the size if this 453 * object is mapped into the kernel. 454 */ 455 if (shmfd->shm_kmappings > 0) { 456 VM_OBJECT_WUNLOCK(object); 457 return (EBUSY); 458 } 459 460 /* 461 * Zero the truncated part of the last page. 462 */ 463 base = length & PAGE_MASK; 464 if (base != 0) { 465 idx = OFF_TO_IDX(length); 466retry: 467 m = vm_page_lookup(object, idx); 468 if (m != NULL) { 469 if (vm_page_sleep_if_busy(m, "shmtrc")) 470 goto retry; 471 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 472 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL); 473 if (m == NULL) { 474 VM_OBJECT_WUNLOCK(object); 475 VM_WAIT; 476 VM_OBJECT_WLOCK(object); 477 goto retry; 478 } else if (m->valid != VM_PAGE_BITS_ALL) { 479 ma[0] = m; 480 rv = vm_pager_get_pages(object, ma, 1, 481 0); 482 m = vm_page_lookup(object, idx); 483 } else 484 /* A cached page was reactivated. */ 485 rv = VM_PAGER_OK; 486 vm_page_lock(m); 487 if (rv == VM_PAGER_OK) { 488 vm_page_deactivate(m); 489 vm_page_unlock(m); 490 vm_page_xunbusy(m); 491 } else { 492 vm_page_free(m); 493 vm_page_unlock(m); 494 VM_OBJECT_WUNLOCK(object); 495 return (EIO); 496 } 497 } 498 if (m != NULL) { 499 pmap_zero_page_area(m, base, PAGE_SIZE - base); 500 KASSERT(m->valid == VM_PAGE_BITS_ALL, 501 ("shm_dotruncate: page %p is invalid", m)); 502 vm_page_dirty(m); 503 vm_pager_page_unswapped(m); 504 } 505 } 506 delta = ptoa(object->size - nobjsize); 507 508 /* Toss in memory pages. */ 509 if (nobjsize < object->size) 510 vm_object_page_remove(object, nobjsize, object->size, 511 0); 512 513 /* Toss pages from swap. */ 514 if (object->type == OBJT_SWAP) 515 swap_pager_freespace(object, nobjsize, delta); 516 517 /* Free the swap accounted for shm */ 518 swap_release_by_cred(delta, object->cred); 519 object->charge -= delta; 520 } else { 521 /* Attempt to reserve the swap */ 522 delta = ptoa(nobjsize - object->size); 523 if (!swap_reserve_by_cred(delta, object->cred)) { 524 VM_OBJECT_WUNLOCK(object); 525 return (ENOMEM); 526 } 527 object->charge += delta; 528 } 529 shmfd->shm_size = length; 530 mtx_lock(&shm_timestamp_lock); 531 vfs_timestamp(&shmfd->shm_ctime); 532 shmfd->shm_mtime = shmfd->shm_ctime; 533 mtx_unlock(&shm_timestamp_lock); 534 object->size = nobjsize; 535 VM_OBJECT_WUNLOCK(object); 536 return (0); 537} 538 539/* 540 * shmfd object management including creation and reference counting 541 * routines. 542 */ 543static struct shmfd * 544shm_alloc(struct ucred *ucred, mode_t mode) 545{ 546 struct shmfd *shmfd; 547 int ino; 548 549 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 550 shmfd->shm_size = 0; 551 shmfd->shm_uid = ucred->cr_uid; 552 shmfd->shm_gid = ucred->cr_gid; 553 shmfd->shm_mode = mode; 554 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 555 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 556 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 557 VM_OBJECT_WLOCK(shmfd->shm_object); 558 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 559 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 560 VM_OBJECT_WUNLOCK(shmfd->shm_object); 561 vfs_timestamp(&shmfd->shm_birthtime); 562 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 563 shmfd->shm_birthtime; 564 ino = alloc_unr(shm_ino_unr); 565 if (ino == -1) 566 shmfd->shm_ino = 0; 567 else 568 shmfd->shm_ino = ino; 569 refcount_init(&shmfd->shm_refs, 1); 570 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF); 571 rangelock_init(&shmfd->shm_rl); 572#ifdef MAC 573 mac_posixshm_init(shmfd); 574 mac_posixshm_create(ucred, shmfd); 575#endif 576 577 return (shmfd); 578} 579 580static struct shmfd * 581shm_hold(struct shmfd *shmfd) 582{ 583 584 refcount_acquire(&shmfd->shm_refs); 585 return (shmfd); 586} 587 588static void 589shm_drop(struct shmfd *shmfd) 590{ 591 592 if (refcount_release(&shmfd->shm_refs)) { 593#ifdef MAC 594 mac_posixshm_destroy(shmfd); 595#endif 596 rangelock_destroy(&shmfd->shm_rl); 597 mtx_destroy(&shmfd->shm_mtx); 598 vm_object_deallocate(shmfd->shm_object); 599 if (shmfd->shm_ino != 0) 600 free_unr(shm_ino_unr, shmfd->shm_ino); 601 free(shmfd, M_SHMFD); 602 } 603} 604 605/* 606 * Determine if the credentials have sufficient permissions for a 607 * specified combination of FREAD and FWRITE. 608 */ 609static int 610shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 611{ 612 accmode_t accmode; 613 int error; 614 615 accmode = 0; 616 if (flags & FREAD) 617 accmode |= VREAD; 618 if (flags & FWRITE) 619 accmode |= VWRITE; 620 mtx_lock(&shm_timestamp_lock); 621 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 622 accmode, ucred, NULL); 623 mtx_unlock(&shm_timestamp_lock); 624 return (error); 625} 626 627/* 628 * Dictionary management. We maintain an in-kernel dictionary to map 629 * paths to shmfd objects. We use the FNV hash on the path to store 630 * the mappings in a hash table. 631 */ 632static void 633shm_init(void *arg) 634{ 635 636 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 637 sx_init(&shm_dict_lock, "shm dictionary"); 638 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 639 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL); 640 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized")); 641 shm_dev_ino = devfs_alloc_cdp_inode(); 642 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized")); 643} 644SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL); 645 646static struct shmfd * 647shm_lookup(char *path, Fnv32_t fnv) 648{ 649 struct shm_mapping *map; 650 651 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 652 if (map->sm_fnv != fnv) 653 continue; 654 if (strcmp(map->sm_path, path) == 0) 655 return (map->sm_shmfd); 656 } 657 658 return (NULL); 659} 660 661static void 662shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 663{ 664 struct shm_mapping *map; 665 666 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 667 map->sm_path = path; 668 map->sm_fnv = fnv; 669 map->sm_shmfd = shm_hold(shmfd); 670 shmfd->shm_path = path; 671 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 672} 673 674static int 675shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 676{ 677 struct shm_mapping *map; 678 int error; 679 680 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 681 if (map->sm_fnv != fnv) 682 continue; 683 if (strcmp(map->sm_path, path) == 0) { 684#ifdef MAC 685 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 686 if (error) 687 return (error); 688#endif 689 error = shm_access(map->sm_shmfd, ucred, 690 FREAD | FWRITE); 691 if (error) 692 return (error); 693 map->sm_shmfd->shm_path = NULL; 694 LIST_REMOVE(map, sm_link); 695 shm_drop(map->sm_shmfd); 696 free(map->sm_path, M_SHMFD); 697 free(map, M_SHMFD); 698 return (0); 699 } 700 } 701 702 return (ENOENT); 703} 704 705/* System calls. */ 706int 707sys_shm_open(struct thread *td, struct shm_open_args *uap) 708{ 709 struct filedesc *fdp; 710 struct shmfd *shmfd; 711 struct file *fp; 712 char *path; 713 Fnv32_t fnv; 714 mode_t cmode; 715 int fd, error; 716 717#ifdef CAPABILITY_MODE 718 /* 719 * shm_open(2) is only allowed for anonymous objects. 720 */ 721 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON)) 722 return (ECAPMODE); 723#endif 724 725 if ((uap->flags & O_ACCMODE) != O_RDONLY && 726 (uap->flags & O_ACCMODE) != O_RDWR) 727 return (EINVAL); 728 729 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0) 730 return (EINVAL); 731 732 fdp = td->td_proc->p_fd; 733 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 734 735 error = falloc(td, &fp, &fd, O_CLOEXEC); 736 if (error) 737 return (error); 738 739 /* A SHM_ANON path pointer creates an anonymous object. */ 740 if (uap->path == SHM_ANON) { 741 /* A read-only anonymous object is pointless. */ 742 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 743 fdclose(fdp, fp, fd, td); 744 fdrop(fp, td); 745 return (EINVAL); 746 } 747 shmfd = shm_alloc(td->td_ucred, cmode); 748 } else { 749 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 750 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 751#ifdef KTRACE 752 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI)) 753 ktrnamei(path); 754#endif 755 /* Require paths to start with a '/' character. */ 756 if (error == 0 && path[0] != '/') 757 error = EINVAL; 758 if (error) { 759 fdclose(fdp, fp, fd, td); 760 fdrop(fp, td); 761 free(path, M_SHMFD); 762 return (error); 763 } 764 765 fnv = fnv_32_str(path, FNV1_32_INIT); 766 sx_xlock(&shm_dict_lock); 767 shmfd = shm_lookup(path, fnv); 768 if (shmfd == NULL) { 769 /* Object does not yet exist, create it if requested. */ 770 if (uap->flags & O_CREAT) { 771#ifdef MAC 772 error = mac_posixshm_check_create(td->td_ucred, 773 path); 774 if (error == 0) { 775#endif 776 shmfd = shm_alloc(td->td_ucred, cmode); 777 shm_insert(path, fnv, shmfd); 778#ifdef MAC 779 } 780#endif 781 } else { 782 free(path, M_SHMFD); 783 error = ENOENT; 784 } 785 } else { 786 /* 787 * Object already exists, obtain a new 788 * reference if requested and permitted. 789 */ 790 free(path, M_SHMFD); 791 if ((uap->flags & (O_CREAT | O_EXCL)) == 792 (O_CREAT | O_EXCL)) 793 error = EEXIST; 794 else { 795#ifdef MAC 796 error = mac_posixshm_check_open(td->td_ucred, 797 shmfd, FFLAGS(uap->flags & O_ACCMODE)); 798 if (error == 0) 799#endif 800 error = shm_access(shmfd, td->td_ucred, 801 FFLAGS(uap->flags & O_ACCMODE)); 802 } 803 804 /* 805 * Truncate the file back to zero length if 806 * O_TRUNC was specified and the object was 807 * opened with read/write. 808 */ 809 if (error == 0 && 810 (uap->flags & (O_ACCMODE | O_TRUNC)) == 811 (O_RDWR | O_TRUNC)) { 812#ifdef MAC 813 error = mac_posixshm_check_truncate( 814 td->td_ucred, fp->f_cred, shmfd); 815 if (error == 0) 816#endif 817 shm_dotruncate(shmfd, 0); 818 } 819 if (error == 0) 820 shm_hold(shmfd); 821 } 822 sx_xunlock(&shm_dict_lock); 823 824 if (error) { 825 fdclose(fdp, fp, fd, td); 826 fdrop(fp, td); 827 return (error); 828 } 829 } 830 831 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 832 833 td->td_retval[0] = fd; 834 fdrop(fp, td); 835 836 return (0); 837} 838 839int 840sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 841{ 842 char *path; 843 Fnv32_t fnv; 844 int error; 845 846 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 847 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 848 if (error) { 849 free(path, M_TEMP); 850 return (error); 851 } 852#ifdef KTRACE 853 if (KTRPOINT(curthread, KTR_NAMEI)) 854 ktrnamei(path); 855#endif 856 fnv = fnv_32_str(path, FNV1_32_INIT); 857 sx_xlock(&shm_dict_lock); 858 error = shm_remove(path, fnv, td->td_ucred); 859 sx_xunlock(&shm_dict_lock); 860 free(path, M_TEMP); 861 862 return (error); 863} 864 865/* 866 * mmap() helper to validate mmap() requests against shm object state 867 * and give mmap() the vm_object to use for the mapping. 868 */ 869int 870shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 871 vm_object_t *obj) 872{ 873 874 /* 875 * XXXRW: This validation is probably insufficient, and subject to 876 * sign errors. It should be fixed. 877 */ 878 if (foff >= shmfd->shm_size || 879 foff + objsize > round_page(shmfd->shm_size)) 880 return (EINVAL); 881 882 mtx_lock(&shm_timestamp_lock); 883 vfs_timestamp(&shmfd->shm_atime); 884 mtx_unlock(&shm_timestamp_lock); 885 vm_object_reference(shmfd->shm_object); 886 *obj = shmfd->shm_object; 887 return (0); 888} 889 890static int 891shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 892 struct thread *td) 893{ 894 struct shmfd *shmfd; 895 int error; 896 897 error = 0; 898 shmfd = fp->f_data; 899 mtx_lock(&shm_timestamp_lock); 900 /* 901 * SUSv4 says that x bits of permission need not be affected. 902 * Be consistent with our shm_open there. 903 */ 904#ifdef MAC 905 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 906 if (error != 0) 907 goto out; 908#endif 909 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 910 shmfd->shm_gid, VADMIN, active_cred, NULL); 911 if (error != 0) 912 goto out; 913 shmfd->shm_mode = mode & ACCESSPERMS; 914out: 915 mtx_unlock(&shm_timestamp_lock); 916 return (error); 917} 918 919static int 920shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 921 struct thread *td) 922{ 923 struct shmfd *shmfd; 924 int error; 925 926 error = 0; 927 shmfd = fp->f_data; 928 mtx_lock(&shm_timestamp_lock); 929#ifdef MAC 930 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 931 if (error != 0) 932 goto out; 933#endif 934 if (uid == (uid_t)-1) 935 uid = shmfd->shm_uid; 936 if (gid == (gid_t)-1) 937 gid = shmfd->shm_gid; 938 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 939 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 940 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 941 goto out; 942 shmfd->shm_uid = uid; 943 shmfd->shm_gid = gid; 944out: 945 mtx_unlock(&shm_timestamp_lock); 946 return (error); 947} 948 949/* 950 * Helper routines to allow the backing object of a shared memory file 951 * descriptor to be mapped in the kernel. 952 */ 953int 954shm_map(struct file *fp, size_t size, off_t offset, void **memp) 955{ 956 struct shmfd *shmfd; 957 vm_offset_t kva, ofs; 958 vm_object_t obj; 959 int rv; 960 961 if (fp->f_type != DTYPE_SHM) 962 return (EINVAL); 963 shmfd = fp->f_data; 964 obj = shmfd->shm_object; 965 VM_OBJECT_WLOCK(obj); 966 /* 967 * XXXRW: This validation is probably insufficient, and subject to 968 * sign errors. It should be fixed. 969 */ 970 if (offset >= shmfd->shm_size || 971 offset + size > round_page(shmfd->shm_size)) { 972 VM_OBJECT_WUNLOCK(obj); 973 return (EINVAL); 974 } 975 976 shmfd->shm_kmappings++; 977 vm_object_reference_locked(obj); 978 VM_OBJECT_WUNLOCK(obj); 979 980 /* Map the object into the kernel_map and wire it. */ 981 kva = vm_map_min(kernel_map); 982 ofs = offset & PAGE_MASK; 983 offset = trunc_page(offset); 984 size = round_page(size + ofs); 985 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0, 986 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 987 VM_PROT_READ | VM_PROT_WRITE, 0); 988 if (rv == KERN_SUCCESS) { 989 rv = vm_map_wire(kernel_map, kva, kva + size, 990 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 991 if (rv == KERN_SUCCESS) { 992 *memp = (void *)(kva + ofs); 993 return (0); 994 } 995 vm_map_remove(kernel_map, kva, kva + size); 996 } else 997 vm_object_deallocate(obj); 998 999 /* On failure, drop our mapping reference. */ 1000 VM_OBJECT_WLOCK(obj); 1001 shmfd->shm_kmappings--; 1002 VM_OBJECT_WUNLOCK(obj); 1003 1004 return (vm_mmap_to_errno(rv)); 1005} 1006 1007/* 1008 * We require the caller to unmap the entire entry. This allows us to 1009 * safely decrement shm_kmappings when a mapping is removed. 1010 */ 1011int 1012shm_unmap(struct file *fp, void *mem, size_t size) 1013{ 1014 struct shmfd *shmfd; 1015 vm_map_entry_t entry; 1016 vm_offset_t kva, ofs; 1017 vm_object_t obj; 1018 vm_pindex_t pindex; 1019 vm_prot_t prot; 1020 boolean_t wired; 1021 vm_map_t map; 1022 int rv; 1023 1024 if (fp->f_type != DTYPE_SHM) 1025 return (EINVAL); 1026 shmfd = fp->f_data; 1027 kva = (vm_offset_t)mem; 1028 ofs = kva & PAGE_MASK; 1029 kva = trunc_page(kva); 1030 size = round_page(size + ofs); 1031 map = kernel_map; 1032 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 1033 &obj, &pindex, &prot, &wired); 1034 if (rv != KERN_SUCCESS) 1035 return (EINVAL); 1036 if (entry->start != kva || entry->end != kva + size) { 1037 vm_map_lookup_done(map, entry); 1038 return (EINVAL); 1039 } 1040 vm_map_lookup_done(map, entry); 1041 if (obj != shmfd->shm_object) 1042 return (EINVAL); 1043 vm_map_remove(map, kva, kva + size); 1044 VM_OBJECT_WLOCK(obj); 1045 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 1046 shmfd->shm_kmappings--; 1047 VM_OBJECT_WUNLOCK(obj); 1048 return (0); 1049} 1050 1051void 1052shm_path(struct shmfd *shmfd, char *path, size_t size) 1053{ 1054 1055 if (shmfd->shm_path == NULL) 1056 return; 1057 sx_slock(&shm_dict_lock); 1058 if (shmfd->shm_path != NULL) 1059 strlcpy(path, shmfd->shm_path, size); 1060 sx_sunlock(&shm_dict_lock); 1061} 1062