uipc_shm.c revision 321020
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 321020 2017-07-15 17:25:40Z dchagin $"); 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#ifdef MAC 297 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd); 298 if (error) 299 return (error); 300#endif 301 foffset_lock_uio(fp, uio, flags); 302 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset, 303 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 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 shmfd->shm_object->pg_color = 0; 558 VM_OBJECT_WLOCK(shmfd->shm_object); 559 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 560 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT); 561 VM_OBJECT_WUNLOCK(shmfd->shm_object); 562 vfs_timestamp(&shmfd->shm_birthtime); 563 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 564 shmfd->shm_birthtime; 565 ino = alloc_unr(shm_ino_unr); 566 if (ino == -1) 567 shmfd->shm_ino = 0; 568 else 569 shmfd->shm_ino = ino; 570 refcount_init(&shmfd->shm_refs, 1); 571 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF); 572 rangelock_init(&shmfd->shm_rl); 573#ifdef MAC 574 mac_posixshm_init(shmfd); 575 mac_posixshm_create(ucred, shmfd); 576#endif 577 578 return (shmfd); 579} 580 581static struct shmfd * 582shm_hold(struct shmfd *shmfd) 583{ 584 585 refcount_acquire(&shmfd->shm_refs); 586 return (shmfd); 587} 588 589static void 590shm_drop(struct shmfd *shmfd) 591{ 592 593 if (refcount_release(&shmfd->shm_refs)) { 594#ifdef MAC 595 mac_posixshm_destroy(shmfd); 596#endif 597 rangelock_destroy(&shmfd->shm_rl); 598 mtx_destroy(&shmfd->shm_mtx); 599 vm_object_deallocate(shmfd->shm_object); 600 if (shmfd->shm_ino != 0) 601 free_unr(shm_ino_unr, shmfd->shm_ino); 602 free(shmfd, M_SHMFD); 603 } 604} 605 606/* 607 * Determine if the credentials have sufficient permissions for a 608 * specified combination of FREAD and FWRITE. 609 */ 610static int 611shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 612{ 613 accmode_t accmode; 614 int error; 615 616 accmode = 0; 617 if (flags & FREAD) 618 accmode |= VREAD; 619 if (flags & FWRITE) 620 accmode |= VWRITE; 621 mtx_lock(&shm_timestamp_lock); 622 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 623 accmode, ucred, NULL); 624 mtx_unlock(&shm_timestamp_lock); 625 return (error); 626} 627 628/* 629 * Dictionary management. We maintain an in-kernel dictionary to map 630 * paths to shmfd objects. We use the FNV hash on the path to store 631 * the mappings in a hash table. 632 */ 633static void 634shm_init(void *arg) 635{ 636 637 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 638 sx_init(&shm_dict_lock, "shm dictionary"); 639 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 640 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL); 641 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized")); 642 shm_dev_ino = devfs_alloc_cdp_inode(); 643 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized")); 644} 645SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL); 646 647static struct shmfd * 648shm_lookup(char *path, Fnv32_t fnv) 649{ 650 struct shm_mapping *map; 651 652 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 653 if (map->sm_fnv != fnv) 654 continue; 655 if (strcmp(map->sm_path, path) == 0) 656 return (map->sm_shmfd); 657 } 658 659 return (NULL); 660} 661 662static void 663shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 664{ 665 struct shm_mapping *map; 666 667 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 668 map->sm_path = path; 669 map->sm_fnv = fnv; 670 map->sm_shmfd = shm_hold(shmfd); 671 shmfd->shm_path = path; 672 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 673} 674 675static int 676shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 677{ 678 struct shm_mapping *map; 679 int error; 680 681 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 682 if (map->sm_fnv != fnv) 683 continue; 684 if (strcmp(map->sm_path, path) == 0) { 685#ifdef MAC 686 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 687 if (error) 688 return (error); 689#endif 690 error = shm_access(map->sm_shmfd, ucred, 691 FREAD | FWRITE); 692 if (error) 693 return (error); 694 map->sm_shmfd->shm_path = NULL; 695 LIST_REMOVE(map, sm_link); 696 shm_drop(map->sm_shmfd); 697 free(map->sm_path, M_SHMFD); 698 free(map, M_SHMFD); 699 return (0); 700 } 701 } 702 703 return (ENOENT); 704} 705 706/* System calls. */ 707int 708sys_shm_open(struct thread *td, struct shm_open_args *uap) 709{ 710 struct filedesc *fdp; 711 struct shmfd *shmfd; 712 struct file *fp; 713 char *path; 714 Fnv32_t fnv; 715 mode_t cmode; 716 int fd, error; 717 718#ifdef CAPABILITY_MODE 719 /* 720 * shm_open(2) is only allowed for anonymous objects. 721 */ 722 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON)) 723 return (ECAPMODE); 724#endif 725 726 if ((uap->flags & O_ACCMODE) != O_RDONLY && 727 (uap->flags & O_ACCMODE) != O_RDWR) 728 return (EINVAL); 729 730 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0) 731 return (EINVAL); 732 733 fdp = td->td_proc->p_fd; 734 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 735 736 error = falloc(td, &fp, &fd, O_CLOEXEC); 737 if (error) 738 return (error); 739 740 /* A SHM_ANON path pointer creates an anonymous object. */ 741 if (uap->path == SHM_ANON) { 742 /* A read-only anonymous object is pointless. */ 743 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 744 fdclose(td, fp, fd); 745 fdrop(fp, td); 746 return (EINVAL); 747 } 748 shmfd = shm_alloc(td->td_ucred, cmode); 749 } else { 750 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 751 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 752#ifdef KTRACE 753 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI)) 754 ktrnamei(path); 755#endif 756 /* Require paths to start with a '/' character. */ 757 if (error == 0 && path[0] != '/') 758 error = EINVAL; 759 if (error) { 760 fdclose(td, fp, fd); 761 fdrop(fp, td); 762 free(path, M_SHMFD); 763 return (error); 764 } 765 766 fnv = fnv_32_str(path, FNV1_32_INIT); 767 sx_xlock(&shm_dict_lock); 768 shmfd = shm_lookup(path, fnv); 769 if (shmfd == NULL) { 770 /* Object does not yet exist, create it if requested. */ 771 if (uap->flags & O_CREAT) { 772#ifdef MAC 773 error = mac_posixshm_check_create(td->td_ucred, 774 path); 775 if (error == 0) { 776#endif 777 shmfd = shm_alloc(td->td_ucred, cmode); 778 shm_insert(path, fnv, shmfd); 779#ifdef MAC 780 } 781#endif 782 } else { 783 free(path, M_SHMFD); 784 error = ENOENT; 785 } 786 } else { 787 /* 788 * Object already exists, obtain a new 789 * reference if requested and permitted. 790 */ 791 free(path, M_SHMFD); 792 if ((uap->flags & (O_CREAT | O_EXCL)) == 793 (O_CREAT | O_EXCL)) 794 error = EEXIST; 795 else { 796#ifdef MAC 797 error = mac_posixshm_check_open(td->td_ucred, 798 shmfd, FFLAGS(uap->flags & O_ACCMODE)); 799 if (error == 0) 800#endif 801 error = shm_access(shmfd, td->td_ucred, 802 FFLAGS(uap->flags & O_ACCMODE)); 803 } 804 805 /* 806 * Truncate the file back to zero length if 807 * O_TRUNC was specified and the object was 808 * opened with read/write. 809 */ 810 if (error == 0 && 811 (uap->flags & (O_ACCMODE | O_TRUNC)) == 812 (O_RDWR | O_TRUNC)) { 813#ifdef MAC 814 error = mac_posixshm_check_truncate( 815 td->td_ucred, fp->f_cred, shmfd); 816 if (error == 0) 817#endif 818 shm_dotruncate(shmfd, 0); 819 } 820 if (error == 0) 821 shm_hold(shmfd); 822 } 823 sx_xunlock(&shm_dict_lock); 824 825 if (error) { 826 fdclose(td, fp, fd); 827 fdrop(fp, td); 828 return (error); 829 } 830 } 831 832 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 833 834 td->td_retval[0] = fd; 835 fdrop(fp, td); 836 837 return (0); 838} 839 840int 841sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 842{ 843 char *path; 844 Fnv32_t fnv; 845 int error; 846 847 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 848 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 849 if (error) { 850 free(path, M_TEMP); 851 return (error); 852 } 853#ifdef KTRACE 854 if (KTRPOINT(curthread, KTR_NAMEI)) 855 ktrnamei(path); 856#endif 857 fnv = fnv_32_str(path, FNV1_32_INIT); 858 sx_xlock(&shm_dict_lock); 859 error = shm_remove(path, fnv, td->td_ucred); 860 sx_xunlock(&shm_dict_lock); 861 free(path, M_TEMP); 862 863 return (error); 864} 865 866/* 867 * mmap() helper to validate mmap() requests against shm object state 868 * and give mmap() the vm_object to use for the mapping. 869 */ 870int 871shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 872 vm_object_t *obj) 873{ 874 875 /* 876 * XXXRW: This validation is probably insufficient, and subject to 877 * sign errors. It should be fixed. 878 */ 879 if (foff >= shmfd->shm_size || 880 foff + objsize > round_page(shmfd->shm_size)) 881 return (EINVAL); 882 883 mtx_lock(&shm_timestamp_lock); 884 vfs_timestamp(&shmfd->shm_atime); 885 mtx_unlock(&shm_timestamp_lock); 886 vm_object_reference(shmfd->shm_object); 887 *obj = shmfd->shm_object; 888 return (0); 889} 890 891static int 892shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 893 struct thread *td) 894{ 895 struct shmfd *shmfd; 896 int error; 897 898 error = 0; 899 shmfd = fp->f_data; 900 mtx_lock(&shm_timestamp_lock); 901 /* 902 * SUSv4 says that x bits of permission need not be affected. 903 * Be consistent with our shm_open there. 904 */ 905#ifdef MAC 906 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 907 if (error != 0) 908 goto out; 909#endif 910 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 911 shmfd->shm_gid, VADMIN, active_cred, NULL); 912 if (error != 0) 913 goto out; 914 shmfd->shm_mode = mode & ACCESSPERMS; 915out: 916 mtx_unlock(&shm_timestamp_lock); 917 return (error); 918} 919 920static int 921shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 922 struct thread *td) 923{ 924 struct shmfd *shmfd; 925 int error; 926 927 error = 0; 928 shmfd = fp->f_data; 929 mtx_lock(&shm_timestamp_lock); 930#ifdef MAC 931 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 932 if (error != 0) 933 goto out; 934#endif 935 if (uid == (uid_t)-1) 936 uid = shmfd->shm_uid; 937 if (gid == (gid_t)-1) 938 gid = shmfd->shm_gid; 939 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 940 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 941 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 942 goto out; 943 shmfd->shm_uid = uid; 944 shmfd->shm_gid = gid; 945out: 946 mtx_unlock(&shm_timestamp_lock); 947 return (error); 948} 949 950/* 951 * Helper routines to allow the backing object of a shared memory file 952 * descriptor to be mapped in the kernel. 953 */ 954int 955shm_map(struct file *fp, size_t size, off_t offset, void **memp) 956{ 957 struct shmfd *shmfd; 958 vm_offset_t kva, ofs; 959 vm_object_t obj; 960 int rv; 961 962 if (fp->f_type != DTYPE_SHM) 963 return (EINVAL); 964 shmfd = fp->f_data; 965 obj = shmfd->shm_object; 966 VM_OBJECT_WLOCK(obj); 967 /* 968 * XXXRW: This validation is probably insufficient, and subject to 969 * sign errors. It should be fixed. 970 */ 971 if (offset >= shmfd->shm_size || 972 offset + size > round_page(shmfd->shm_size)) { 973 VM_OBJECT_WUNLOCK(obj); 974 return (EINVAL); 975 } 976 977 shmfd->shm_kmappings++; 978 vm_object_reference_locked(obj); 979 VM_OBJECT_WUNLOCK(obj); 980 981 /* Map the object into the kernel_map and wire it. */ 982 kva = vm_map_min(kernel_map); 983 ofs = offset & PAGE_MASK; 984 offset = trunc_page(offset); 985 size = round_page(size + ofs); 986 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0, 987 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 988 VM_PROT_READ | VM_PROT_WRITE, 0); 989 if (rv == KERN_SUCCESS) { 990 rv = vm_map_wire(kernel_map, kva, kva + size, 991 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 992 if (rv == KERN_SUCCESS) { 993 *memp = (void *)(kva + ofs); 994 return (0); 995 } 996 vm_map_remove(kernel_map, kva, kva + size); 997 } else 998 vm_object_deallocate(obj); 999 1000 /* On failure, drop our mapping reference. */ 1001 VM_OBJECT_WLOCK(obj); 1002 shmfd->shm_kmappings--; 1003 VM_OBJECT_WUNLOCK(obj); 1004 1005 return (vm_mmap_to_errno(rv)); 1006} 1007 1008/* 1009 * We require the caller to unmap the entire entry. This allows us to 1010 * safely decrement shm_kmappings when a mapping is removed. 1011 */ 1012int 1013shm_unmap(struct file *fp, void *mem, size_t size) 1014{ 1015 struct shmfd *shmfd; 1016 vm_map_entry_t entry; 1017 vm_offset_t kva, ofs; 1018 vm_object_t obj; 1019 vm_pindex_t pindex; 1020 vm_prot_t prot; 1021 boolean_t wired; 1022 vm_map_t map; 1023 int rv; 1024 1025 if (fp->f_type != DTYPE_SHM) 1026 return (EINVAL); 1027 shmfd = fp->f_data; 1028 kva = (vm_offset_t)mem; 1029 ofs = kva & PAGE_MASK; 1030 kva = trunc_page(kva); 1031 size = round_page(size + ofs); 1032 map = kernel_map; 1033 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 1034 &obj, &pindex, &prot, &wired); 1035 if (rv != KERN_SUCCESS) 1036 return (EINVAL); 1037 if (entry->start != kva || entry->end != kva + size) { 1038 vm_map_lookup_done(map, entry); 1039 return (EINVAL); 1040 } 1041 vm_map_lookup_done(map, entry); 1042 if (obj != shmfd->shm_object) 1043 return (EINVAL); 1044 vm_map_remove(map, kva, kva + size); 1045 VM_OBJECT_WLOCK(obj); 1046 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 1047 shmfd->shm_kmappings--; 1048 VM_OBJECT_WUNLOCK(obj); 1049 return (0); 1050} 1051 1052void 1053shm_path(struct shmfd *shmfd, char *path, size_t size) 1054{ 1055 1056 if (shmfd->shm_path == NULL) 1057 return; 1058 sx_slock(&shm_dict_lock); 1059 if (shmfd->shm_path != NULL) 1060 strlcpy(path, shmfd->shm_path, size); 1061 sx_sunlock(&shm_dict_lock); 1062} 1063