sys/kern/uipc_shm.c

   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("$FreeBSD$");
  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/syscallsubr.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 #include <sys/unistd.h>
  79 #include <sys/user.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_extern.h>
  87 #include <vm/vm_map.h>
  88 #include <vm/vm_kern.h>
  89 #include <vm/vm_object.h>
  90 #include <vm/vm_page.h>
  91 #include <vm/vm_pageout.h>
  92 #include <vm/vm_pager.h>
  93 #include <vm/swap_pager.h>
  94
  95 struct shm_mapping {
  96         char            *sm_path;
  97         Fnv32_t         sm_fnv;
  98         struct shmfd    *sm_shmfd;
  99         LIST_ENTRY(shm_mapping) sm_link;
 100 };
 101
 102 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
 103 static LIST_HEAD(, shm_mapping) *shm_dictionary;
 104 static struct sx shm_dict_lock;
 105 static struct mtx shm_timestamp_lock;
 106 static u_long shm_hash;
 107 static struct unrhdr *shm_ino_unr;
 108 static dev_t shm_dev_ino;
 109
 110 #define SHM_HASH(fnv)   (&shm_dictionary[(fnv) & shm_hash])
 111
 112 static int      shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
 113 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
 114 static void     shm_init(void *arg);
 115 static void     shm_drop(struct shmfd *shmfd);
 116 static struct shmfd *shm_hold(struct shmfd *shmfd);
 117 static void     shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
 118 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
 119 static int      shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
 120 static int      shm_dotruncate(struct shmfd *shmfd, off_t length);
 121
 122 static fo_rdwr_t        shm_read;
 123 static fo_rdwr_t        shm_write;
 124 static fo_truncate_t    shm_truncate;
 125 static fo_stat_t        shm_stat;
 126 static fo_close_t       shm_close;
 127 static fo_chmod_t       shm_chmod;
 128 static fo_chown_t       shm_chown;
 129 static fo_seek_t        shm_seek;
 130 static fo_fill_kinfo_t  shm_fill_kinfo;
 131 static fo_mmap_t        shm_mmap;
 132
 133 /* File descriptor operations. */
 134 static struct fileops shm_ops = {
 135         .fo_read = shm_read,
 136         .fo_write = shm_write,
 137         .fo_truncate = shm_truncate,
 138         .fo_ioctl = invfo_ioctl,
 139         .fo_poll = invfo_poll,
 140         .fo_kqfilter = invfo_kqfilter,
 141         .fo_stat = shm_stat,
 142         .fo_close = shm_close,
 143         .fo_chmod = shm_chmod,
 144         .fo_chown = shm_chown,
 145         .fo_sendfile = vn_sendfile,
 146         .fo_seek = shm_seek,
 147         .fo_fill_kinfo = shm_fill_kinfo,
 148         .fo_mmap = shm_mmap,
 149         .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
 150 };
 151
 152 FEATURE(posix_shm, "POSIX shared memory");
 153
 154 static int
 155 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
 156 {
 157         vm_page_t m;
 158         vm_pindex_t idx;
 159         size_t tlen;
 160         int error, offset, rv;
 161
 162         idx = OFF_TO_IDX(uio->uio_offset);
 163         offset = uio->uio_offset & PAGE_MASK;
 164         tlen = MIN(PAGE_SIZE - offset, len);
 165
 166         VM_OBJECT_WLOCK(obj);
 167
 168         /*
 169          * Read I/O without either a corresponding resident page or swap
 170          * page: use zero_region.  This is intended to avoid instantiating
 171          * pages on read from a sparse region.
 172          */
 173         if (uio->uio_rw == UIO_READ && vm_page_lookup(obj, idx) == NULL &&
 174             !vm_pager_has_page(obj, idx, NULL, NULL)) {
 175                 VM_OBJECT_WUNLOCK(obj);
 176                 return (uiomove(__DECONST(void *, zero_region), tlen, uio));
 177         }
 178
 179         /*
 180          * Parallel reads of the page content from disk are prevented
 181          * by exclusive busy.
 182          *
 183          * Although the tmpfs vnode lock is held here, it is
 184          * nonetheless safe to sleep waiting for a free page.  The
 185          * pageout daemon does not need to acquire the tmpfs vnode
 186          * lock to page out tobj's pages because tobj is a OBJT_SWAP
 187          * type object.
 188          */
 189         m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
 190         if (m->valid != VM_PAGE_BITS_ALL) {
 191                 if (vm_pager_has_page(obj, idx, NULL, NULL)) {
 192                         rv = vm_pager_get_pages(obj, &m, 1, NULL, NULL);
 193                         if (rv != VM_PAGER_OK) {
 194                                 printf(
 195             "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
 196                                     obj, idx, m->valid, rv);
 197                                 vm_page_lock(m);
 198                                 vm_page_free(m);
 199                                 vm_page_unlock(m);
 200                                 VM_OBJECT_WUNLOCK(obj);
 201                                 return (EIO);
 202                         }
 203                 } else
 204                         vm_page_zero_invalid(m, TRUE);
 205         }
 206         vm_page_xunbusy(m);
 207         vm_page_lock(m);
 208         vm_page_hold(m);
 209         if (m->queue == PQ_NONE) {
 210                 vm_page_deactivate(m);
 211         } else {
 212                 /* Requeue to maintain LRU ordering. */
 213                 vm_page_requeue(m);
 214         }
 215         vm_page_unlock(m);
 216         VM_OBJECT_WUNLOCK(obj);
 217         error = uiomove_fromphys(&m, offset, tlen, uio);
 218         if (uio->uio_rw == UIO_WRITE && error == 0) {
 219                 VM_OBJECT_WLOCK(obj);
 220                 vm_page_dirty(m);
 221                 vm_pager_page_unswapped(m);
 222                 VM_OBJECT_WUNLOCK(obj);
 223         }
 224         vm_page_lock(m);
 225         vm_page_unhold(m);
 226         vm_page_unlock(m);
 227
 228         return (error);
 229 }
 230
 231 int
 232 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
 233 {
 234         ssize_t resid;
 235         size_t len;
 236         int error;
 237
 238         error = 0;
 239         while ((resid = uio->uio_resid) > 0) {
 240                 if (obj_size <= uio->uio_offset)
 241                         break;
 242                 len = MIN(obj_size - uio->uio_offset, resid);
 243                 if (len == 0)
 244                         break;
 245                 error = uiomove_object_page(obj, len, uio);
 246                 if (error != 0 || resid == uio->uio_resid)
 247                         break;
 248         }
 249         return (error);
 250 }
 251
 252 static int
 253 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
 254 {
 255         struct shmfd *shmfd;
 256         off_t foffset;
 257         int error;
 258
 259         shmfd = fp->f_data;
 260         foffset = foffset_lock(fp, 0);
 261         error = 0;
 262         switch (whence) {
 263         case L_INCR:
 264                 if (foffset < 0 ||
 265                     (offset > 0 && foffset > OFF_MAX - offset)) {
 266                         error = EOVERFLOW;
 267                         break;
 268                 }
 269                 offset += foffset;
 270                 break;
 271         case L_XTND:
 272                 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
 273                         error = EOVERFLOW;
 274                         break;
 275                 }
 276                 offset += shmfd->shm_size;
 277                 break;
 278         case L_SET:
 279                 break;
 280         default:
 281                 error = EINVAL;
 282         }
 283         if (error == 0) {
 284                 if (offset < 0 || offset > shmfd->shm_size)
 285                         error = EINVAL;
 286                 else
 287                         td->td_uretoff.tdu_off = offset;
 288         }
 289         foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
 290         return (error);
 291 }
 292
 293 static int
 294 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 295     int flags, struct thread *td)
 296 {
 297         struct shmfd *shmfd;
 298         void *rl_cookie;
 299         int error;
 300
 301         shmfd = fp->f_data;
 302         foffset_lock_uio(fp, uio, flags);
 303         rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
 304             uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 305 #ifdef MAC
 306         error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
 307         if (error)
 308                 return (error);
 309 #endif
 310         error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
 311         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 312         foffset_unlock_uio(fp, uio, flags);
 313         return (error);
 314 }
 315
 316 static int
 317 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 318     int flags, struct thread *td)
 319 {
 320         struct shmfd *shmfd;
 321         void *rl_cookie;
 322         int error;
 323
 324         shmfd = fp->f_data;
 325 #ifdef MAC
 326         error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
 327         if (error)
 328                 return (error);
 329 #endif
 330         foffset_lock_uio(fp, uio, flags);
 331         if ((flags & FOF_OFFSET) == 0) {
 332                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
 333                     &shmfd->shm_mtx);
 334         } else {
 335                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
 336                     uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 337         }
 338
 339         error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
 340         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 341         foffset_unlock_uio(fp, uio, flags);
 342         return (error);
 343 }
 344
 345 static int
 346 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 347     struct thread *td)
 348 {
 349         struct shmfd *shmfd;
 350 #ifdef MAC
 351         int error;
 352 #endif
 353
 354         shmfd = fp->f_data;
 355 #ifdef MAC
 356         error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
 357         if (error)
 358                 return (error);
 359 #endif
 360         return (shm_dotruncate(shmfd, length));
 361 }
 362
 363 static int
 364 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
 365     struct thread *td)
 366 {
 367         struct shmfd *shmfd;
 368 #ifdef MAC
 369         int error;
 370 #endif
 371
 372         shmfd = fp->f_data;
 373
 374 #ifdef MAC
 375         error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
 376         if (error)
 377                 return (error);
 378 #endif
 379
 380         /*
 381          * Attempt to return sanish values for fstat() on a memory file
 382          * descriptor.
 383          */
 384         bzero(sb, sizeof(*sb));
 385         sb->st_blksize = PAGE_SIZE;
 386         sb->st_size = shmfd->shm_size;
 387         sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
 388         mtx_lock(&shm_timestamp_lock);
 389         sb->st_atim = shmfd->shm_atime;
 390         sb->st_ctim = shmfd->shm_ctime;
 391         sb->st_mtim = shmfd->shm_mtime;
 392         sb->st_birthtim = shmfd->shm_birthtime;
 393         sb->st_mode = S_IFREG | shmfd->shm_mode;                /* XXX */
 394         sb->st_uid = shmfd->shm_uid;
 395         sb->st_gid = shmfd->shm_gid;
 396         mtx_unlock(&shm_timestamp_lock);
 397         sb->st_dev = shm_dev_ino;
 398         sb->st_ino = shmfd->shm_ino;
 399
 400         return (0);
 401 }
 402
 403 static int
 404 shm_close(struct file *fp, struct thread *td)
 405 {
 406         struct shmfd *shmfd;
 407
 408         shmfd = fp->f_data;
 409         fp->f_data = NULL;
 410         shm_drop(shmfd);
 411
 412         return (0);
 413 }
 414
 415 static int
 416 shm_dotruncate(struct shmfd *shmfd, off_t length)
 417 {
 418         vm_object_t object;
 419         vm_page_t m;
 420         vm_pindex_t idx, nobjsize;
 421         vm_ooffset_t delta;
 422         int base, rv;
 423
 424         object = shmfd->shm_object;
 425         VM_OBJECT_WLOCK(object);
 426         if (length == shmfd->shm_size) {
 427                 VM_OBJECT_WUNLOCK(object);
 428                 return (0);
 429         }
 430         nobjsize = OFF_TO_IDX(length + PAGE_MASK);
 431
 432         /* Are we shrinking?  If so, trim the end. */
 433         if (length < shmfd->shm_size) {
 434                 /*
 435                  * Disallow any requests to shrink the size if this
 436                  * object is mapped into the kernel.
 437                  */
 438                 if (shmfd->shm_kmappings > 0) {
 439                         VM_OBJECT_WUNLOCK(object);
 440                         return (EBUSY);
 441                 }
 442
 443                 /*
 444                  * Zero the truncated part of the last page.
 445                  */
 446                 base = length & PAGE_MASK;
 447                 if (base != 0) {
 448                         idx = OFF_TO_IDX(length);
 449 retry:
 450                         m = vm_page_lookup(object, idx);
 451                         if (m != NULL) {
 452                                 if (vm_page_sleep_if_busy(m, "shmtrc"))
 453                                         goto retry;
 454                         } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
 455                                 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
 456                                 if (m == NULL) {
 457                                         VM_OBJECT_WUNLOCK(object);
 458                                         VM_WAIT;
 459                                         VM_OBJECT_WLOCK(object);
 460                                         goto retry;
 461                                 } else if (m->valid != VM_PAGE_BITS_ALL)
 462                                         rv = vm_pager_get_pages(object, &m, 1,
 463                                             NULL, NULL);
 464                                 else
 465                                         /* A cached page was reactivated. */
 466                                         rv = VM_PAGER_OK;
 467                                 vm_page_lock(m);
 468                                 if (rv == VM_PAGER_OK) {
 469                                         vm_page_deactivate(m);
 470                                         vm_page_unlock(m);
 471                                         vm_page_xunbusy(m);
 472                                 } else {
 473                                         vm_page_free(m);
 474                                         vm_page_unlock(m);
 475                                         VM_OBJECT_WUNLOCK(object);
 476                                         return (EIO);
 477                                 }
 478                         }
 479                         if (m != NULL) {
 480                                 pmap_zero_page_area(m, base, PAGE_SIZE - base);
 481                                 KASSERT(m->valid == VM_PAGE_BITS_ALL,
 482                                     ("shm_dotruncate: page %p is invalid", m));
 483                                 vm_page_dirty(m);
 484                                 vm_pager_page_unswapped(m);
 485                         }
 486                 }
 487                 delta = ptoa(object->size - nobjsize);
 488
 489                 /* Toss in memory pages. */
 490                 if (nobjsize < object->size)
 491                         vm_object_page_remove(object, nobjsize, object->size,
 492                             0);
 493
 494                 /* Toss pages from swap. */
 495                 if (object->type == OBJT_SWAP)
 496                         swap_pager_freespace(object, nobjsize, delta);
 497
 498                 /* Free the swap accounted for shm */
 499                 swap_release_by_cred(delta, object->cred);
 500                 object->charge -= delta;
 501         } else {
 502                 /* Attempt to reserve the swap */
 503                 delta = ptoa(nobjsize - object->size);
 504                 if (!swap_reserve_by_cred(delta, object->cred)) {
 505                         VM_OBJECT_WUNLOCK(object);
 506                         return (ENOMEM);
 507                 }
 508                 object->charge += delta;
 509         }
 510         shmfd->shm_size = length;
 511         mtx_lock(&shm_timestamp_lock);
 512         vfs_timestamp(&shmfd->shm_ctime);
 513         shmfd->shm_mtime = shmfd->shm_ctime;
 514         mtx_unlock(&shm_timestamp_lock);
 515         object->size = nobjsize;
 516         VM_OBJECT_WUNLOCK(object);
 517         return (0);
 518 }
 519
 520 /*
 521  * shmfd object management including creation and reference counting
 522  * routines.
 523  */
 524 static struct shmfd *
 525 shm_alloc(struct ucred *ucred, mode_t mode)
 526 {
 527         struct shmfd *shmfd;
 528         int ino;
 529
 530         shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
 531         shmfd->shm_size = 0;
 532         shmfd->shm_uid = ucred->cr_uid;
 533         shmfd->shm_gid = ucred->cr_gid;
 534         shmfd->shm_mode = mode;
 535         shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
 536             shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
 537         KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
 538         shmfd->shm_object->pg_color = 0;
 539         VM_OBJECT_WLOCK(shmfd->shm_object);
 540         vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
 541         vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
 542         VM_OBJECT_WUNLOCK(shmfd->shm_object);
 543         vfs_timestamp(&shmfd->shm_birthtime);
 544         shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
 545             shmfd->shm_birthtime;
 546         ino = alloc_unr(shm_ino_unr);
 547         if (ino == -1)
 548                 shmfd->shm_ino = 0;
 549         else
 550                 shmfd->shm_ino = ino;
 551         refcount_init(&shmfd->shm_refs, 1);
 552         mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
 553         rangelock_init(&shmfd->shm_rl);
 554 #ifdef MAC
 555         mac_posixshm_init(shmfd);
 556         mac_posixshm_create(ucred, shmfd);
 557 #endif
 558
 559         return (shmfd);
 560 }
 561
 562 static struct shmfd *
 563 shm_hold(struct shmfd *shmfd)
 564 {
 565
 566         refcount_acquire(&shmfd->shm_refs);
 567         return (shmfd);
 568 }
 569
 570 static void
 571 shm_drop(struct shmfd *shmfd)
 572 {
 573
 574         if (refcount_release(&shmfd->shm_refs)) {
 575 #ifdef MAC
 576                 mac_posixshm_destroy(shmfd);
 577 #endif
 578                 rangelock_destroy(&shmfd->shm_rl);
 579                 mtx_destroy(&shmfd->shm_mtx);
 580                 vm_object_deallocate(shmfd->shm_object);
 581                 if (shmfd->shm_ino != 0)
 582                         free_unr(shm_ino_unr, shmfd->shm_ino);
 583                 free(shmfd, M_SHMFD);
 584         }
 585 }
 586
 587 /*
 588  * Determine if the credentials have sufficient permissions for a
 589  * specified combination of FREAD and FWRITE.
 590  */
 591 static int
 592 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
 593 {
 594         accmode_t accmode;
 595         int error;
 596
 597         accmode = 0;
 598         if (flags & FREAD)
 599                 accmode |= VREAD;
 600         if (flags & FWRITE)
 601                 accmode |= VWRITE;
 602         mtx_lock(&shm_timestamp_lock);
 603         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
 604             accmode, ucred, NULL);
 605         mtx_unlock(&shm_timestamp_lock);
 606         return (error);
 607 }
 608
 609 /*
 610  * Dictionary management.  We maintain an in-kernel dictionary to map
 611  * paths to shmfd objects.  We use the FNV hash on the path to store
 612  * the mappings in a hash table.
 613  */
 614 static void
 615 shm_init(void *arg)
 616 {
 617
 618         mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
 619         sx_init(&shm_dict_lock, "shm dictionary");
 620         shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
 621         shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL);
 622         KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized"));
 623         shm_dev_ino = devfs_alloc_cdp_inode();
 624         KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
 625 }
 626 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
 627
 628 static struct shmfd *
 629 shm_lookup(char *path, Fnv32_t fnv)
 630 {
 631         struct shm_mapping *map;
 632
 633         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 634                 if (map->sm_fnv != fnv)
 635                         continue;
 636                 if (strcmp(map->sm_path, path) == 0)
 637                         return (map->sm_shmfd);
 638         }
 639
 640         return (NULL);
 641 }
 642
 643 static void
 644 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
 645 {
 646         struct shm_mapping *map;
 647
 648         map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
 649         map->sm_path = path;
 650         map->sm_fnv = fnv;
 651         map->sm_shmfd = shm_hold(shmfd);
 652         shmfd->shm_path = path;
 653         LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
 654 }
 655
 656 static int
 657 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
 658 {
 659         struct shm_mapping *map;
 660         int error;
 661
 662         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 663                 if (map->sm_fnv != fnv)
 664                         continue;
 665                 if (strcmp(map->sm_path, path) == 0) {
 666 #ifdef MAC
 667                         error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
 668                         if (error)
 669                                 return (error);
 670 #endif
 671                         error = shm_access(map->sm_shmfd, ucred,
 672                             FREAD | FWRITE);
 673                         if (error)
 674                                 return (error);
 675                         map->sm_shmfd->shm_path = NULL;
 676                         LIST_REMOVE(map, sm_link);
 677                         shm_drop(map->sm_shmfd);
 678                         free(map->sm_path, M_SHMFD);
 679                         free(map, M_SHMFD);
 680                         return (0);
 681                 }
 682         }
 683
 684         return (ENOENT);
 685 }
 686
 687 int
 688 kern_shm_open(struct thread *td, const char *userpath, int flags, mode_t mode,
 689     struct filecaps *fcaps)
 690 {
 691         struct filedesc *fdp;
 692         struct shmfd *shmfd;
 693         struct file *fp;
 694         char *path;
 695         Fnv32_t fnv;
 696         mode_t cmode;
 697         int fd, error;
 698
 699 #ifdef CAPABILITY_MODE
 700         /*
 701          * shm_open(2) is only allowed for anonymous objects.
 702          */
 703         if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON))
 704                 return (ECAPMODE);
 705 #endif
 706
 707         if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR)
 708                 return (EINVAL);
 709
 710         if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
 711                 return (EINVAL);
 712
 713         fdp = td->td_proc->p_fd;
 714         cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
 715
 716         error = falloc_caps(td, &fp, &fd, O_CLOEXEC, fcaps);
 717         if (error)
 718                 return (error);
 719
 720         /* A SHM_ANON path pointer creates an anonymous object. */
 721         if (userpath == SHM_ANON) {
 722                 /* A read-only anonymous object is pointless. */
 723                 if ((flags & O_ACCMODE) == O_RDONLY) {
 724                         fdclose(td, fp, fd);
 725                         fdrop(fp, td);
 726                         return (EINVAL);
 727                 }
 728                 shmfd = shm_alloc(td->td_ucred, cmode);
 729         } else {
 730                 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
 731                 error = copyinstr(userpath, path, MAXPATHLEN, NULL);
 732 #ifdef KTRACE
 733                 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
 734                         ktrnamei(path);
 735 #endif
 736                 /* Require paths to start with a '/' character. */
 737                 if (error == 0 && path[0] != '/')
 738                         error = EINVAL;
 739                 if (error) {
 740                         fdclose(td, fp, fd);
 741                         fdrop(fp, td);
 742                         free(path, M_SHMFD);
 743                         return (error);
 744                 }
 745
 746                 fnv = fnv_32_str(path, FNV1_32_INIT);
 747                 sx_xlock(&shm_dict_lock);
 748                 shmfd = shm_lookup(path, fnv);
 749                 if (shmfd == NULL) {
 750                         /* Object does not yet exist, create it if requested. */
 751                         if (flags & O_CREAT) {
 752 #ifdef MAC
 753                                 error = mac_posixshm_check_create(td->td_ucred,
 754                                     path);
 755                                 if (error == 0) {
 756 #endif
 757                                         shmfd = shm_alloc(td->td_ucred, cmode);
 758                                         shm_insert(path, fnv, shmfd);
 759 #ifdef MAC
 760                                 }
 761 #endif
 762                         } else {
 763                                 free(path, M_SHMFD);
 764                                 error = ENOENT;
 765                         }
 766                 } else {
 767                         /*
 768                          * Object already exists, obtain a new
 769                          * reference if requested and permitted.
 770                          */
 771                         free(path, M_SHMFD);
 772                         if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
 773                                 error = EEXIST;
 774                         else {
 775 #ifdef MAC
 776                                 error = mac_posixshm_check_open(td->td_ucred,
 777                                     shmfd, FFLAGS(flags & O_ACCMODE));
 778                                 if (error == 0)
 779 #endif
 780                                 error = shm_access(shmfd, td->td_ucred,
 781                                     FFLAGS(flags & O_ACCMODE));
 782                         }
 783
 784                         /*
 785                          * Truncate the file back to zero length if
 786                          * O_TRUNC was specified and the object was
 787                          * opened with read/write.
 788                          */
 789                         if (error == 0 &&
 790                             (flags & (O_ACCMODE | O_TRUNC)) ==
 791                             (O_RDWR | O_TRUNC)) {
 792 #ifdef MAC
 793                                 error = mac_posixshm_check_truncate(
 794                                         td->td_ucred, fp->f_cred, shmfd);
 795                                 if (error == 0)
 796 #endif
 797                                         shm_dotruncate(shmfd, 0);
 798                         }
 799                         if (error == 0)
 800                                 shm_hold(shmfd);
 801                 }
 802                 sx_xunlock(&shm_dict_lock);
 803
 804                 if (error) {
 805                         fdclose(td, fp, fd);
 806                         fdrop(fp, td);
 807                         return (error);
 808                 }
 809         }
 810
 811         finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
 812
 813         td->td_retval[0] = fd;
 814         fdrop(fp, td);
 815
 816         return (0);
 817 }
 818
 819 /* System calls. */
 820 int
 821 sys_shm_open(struct thread *td, struct shm_open_args *uap)
 822 {
 823
 824         return (kern_shm_open(td, uap->path, uap->flags, uap->mode, NULL));
 825 }
 826
 827 int
 828 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
 829 {
 830         char *path;
 831         Fnv32_t fnv;
 832         int error;
 833
 834         path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
 835         error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
 836         if (error) {
 837                 free(path, M_TEMP);
 838                 return (error);
 839         }
 840 #ifdef KTRACE
 841         if (KTRPOINT(curthread, KTR_NAMEI))
 842                 ktrnamei(path);
 843 #endif
 844         fnv = fnv_32_str(path, FNV1_32_INIT);
 845         sx_xlock(&shm_dict_lock);
 846         error = shm_remove(path, fnv, td->td_ucred);
 847         sx_xunlock(&shm_dict_lock);
 848         free(path, M_TEMP);
 849
 850         return (error);
 851 }
 852
 853 int
 854 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize,
 855     vm_prot_t prot, vm_prot_t cap_maxprot, int flags,
 856     vm_ooffset_t foff, struct thread *td)
 857 {
 858         struct shmfd *shmfd;
 859         vm_prot_t maxprot;
 860         int error;
 861
 862         shmfd = fp->f_data;
 863         maxprot = VM_PROT_NONE;
 864
 865         /* FREAD should always be set. */
 866         if ((fp->f_flag & FREAD) != 0)
 867                 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ;
 868         if ((fp->f_flag & FWRITE) != 0)
 869                 maxprot |= VM_PROT_WRITE;
 870
 871         /* Don't permit shared writable mappings on read-only descriptors. */
 872         if ((flags & MAP_SHARED) != 0 &&
 873             (maxprot & VM_PROT_WRITE) == 0 &&
 874             (prot & VM_PROT_WRITE) != 0)
 875                 return (EACCES);
 876         maxprot &= cap_maxprot;
 877
 878 #ifdef MAC
 879         error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags);
 880         if (error != 0)
 881                 return (error);
 882 #endif
 883
 884         /*
 885          * XXXRW: This validation is probably insufficient, and subject to
 886          * sign errors.  It should be fixed.
 887          */
 888         if (foff >= shmfd->shm_size ||
 889             foff + objsize > round_page(shmfd->shm_size))
 890                 return (EINVAL);
 891
 892         mtx_lock(&shm_timestamp_lock);
 893         vfs_timestamp(&shmfd->shm_atime);
 894         mtx_unlock(&shm_timestamp_lock);
 895         vm_object_reference(shmfd->shm_object);
 896
 897         error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags,
 898             shmfd->shm_object, foff, FALSE, td);
 899         if (error != 0)
 900                 vm_object_deallocate(shmfd->shm_object);
 901         return (0);
 902 }
 903
 904 static int
 905 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
 906     struct thread *td)
 907 {
 908         struct shmfd *shmfd;
 909         int error;
 910
 911         error = 0;
 912         shmfd = fp->f_data;
 913         mtx_lock(&shm_timestamp_lock);
 914         /*
 915          * SUSv4 says that x bits of permission need not be affected.
 916          * Be consistent with our shm_open there.
 917          */
 918 #ifdef MAC
 919         error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
 920         if (error != 0)
 921                 goto out;
 922 #endif
 923         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
 924             shmfd->shm_gid, VADMIN, active_cred, NULL);
 925         if (error != 0)
 926                 goto out;
 927         shmfd->shm_mode = mode & ACCESSPERMS;
 928 out:
 929         mtx_unlock(&shm_timestamp_lock);
 930         return (error);
 931 }
 932
 933 static int
 934 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
 935     struct thread *td)
 936 {
 937         struct shmfd *shmfd;
 938         int error;
 939
 940         error = 0;
 941         shmfd = fp->f_data;
 942         mtx_lock(&shm_timestamp_lock);
 943 #ifdef MAC
 944         error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
 945         if (error != 0)
 946                 goto out;
 947 #endif
 948         if (uid == (uid_t)-1)
 949                 uid = shmfd->shm_uid;
 950         if (gid == (gid_t)-1)
 951                  gid = shmfd->shm_gid;
 952         if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
 953             (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
 954             (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
 955                 goto out;
 956         shmfd->shm_uid = uid;
 957         shmfd->shm_gid = gid;
 958 out:
 959         mtx_unlock(&shm_timestamp_lock);
 960         return (error);
 961 }
 962
 963 /*
 964  * Helper routines to allow the backing object of a shared memory file
 965  * descriptor to be mapped in the kernel.
 966  */
 967 int
 968 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
 969 {
 970         struct shmfd *shmfd;
 971         vm_offset_t kva, ofs;
 972         vm_object_t obj;
 973         int rv;
 974
 975         if (fp->f_type != DTYPE_SHM)
 976                 return (EINVAL);
 977         shmfd = fp->f_data;
 978         obj = shmfd->shm_object;
 979         VM_OBJECT_WLOCK(obj);
 980         /*
 981          * XXXRW: This validation is probably insufficient, and subject to
 982          * sign errors.  It should be fixed.
 983          */
 984         if (offset >= shmfd->shm_size ||
 985             offset + size > round_page(shmfd->shm_size)) {
 986                 VM_OBJECT_WUNLOCK(obj);
 987                 return (EINVAL);
 988         }
 989
 990         shmfd->shm_kmappings++;
 991         vm_object_reference_locked(obj);
 992         VM_OBJECT_WUNLOCK(obj);
 993
 994         /* Map the object into the kernel_map and wire it. */
 995         kva = vm_map_min(kernel_map);
 996         ofs = offset & PAGE_MASK;
 997         offset = trunc_page(offset);
 998         size = round_page(size + ofs);
 999         rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
1000             VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
1001             VM_PROT_READ | VM_PROT_WRITE, 0);
1002         if (rv == KERN_SUCCESS) {
1003                 rv = vm_map_wire(kernel_map, kva, kva + size,
1004                     VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
1005                 if (rv == KERN_SUCCESS) {
1006                         *memp = (void *)(kva + ofs);
1007                         return (0);
1008                 }
1009                 vm_map_remove(kernel_map, kva, kva + size);
1010         } else
1011                 vm_object_deallocate(obj);
1012
1013         /* On failure, drop our mapping reference. */
1014         VM_OBJECT_WLOCK(obj);
1015         shmfd->shm_kmappings--;
1016         VM_OBJECT_WUNLOCK(obj);
1017
1018         return (vm_mmap_to_errno(rv));
1019 }
1020
1021 /*
1022  * We require the caller to unmap the entire entry.  This allows us to
1023  * safely decrement shm_kmappings when a mapping is removed.
1024  */
1025 int
1026 shm_unmap(struct file *fp, void *mem, size_t size)
1027 {
1028         struct shmfd *shmfd;
1029         vm_map_entry_t entry;
1030         vm_offset_t kva, ofs;
1031         vm_object_t obj;
1032         vm_pindex_t pindex;
1033         vm_prot_t prot;
1034         boolean_t wired;
1035         vm_map_t map;
1036         int rv;
1037
1038         if (fp->f_type != DTYPE_SHM)
1039                 return (EINVAL);
1040         shmfd = fp->f_data;
1041         kva = (vm_offset_t)mem;
1042         ofs = kva & PAGE_MASK;
1043         kva = trunc_page(kva);
1044         size = round_page(size + ofs);
1045         map = kernel_map;
1046         rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1047             &obj, &pindex, &prot, &wired);
1048         if (rv != KERN_SUCCESS)
1049                 return (EINVAL);
1050         if (entry->start != kva || entry->end != kva + size) {
1051                 vm_map_lookup_done(map, entry);
1052                 return (EINVAL);
1053         }
1054         vm_map_lookup_done(map, entry);
1055         if (obj != shmfd->shm_object)
1056                 return (EINVAL);
1057         vm_map_remove(map, kva, kva + size);
1058         VM_OBJECT_WLOCK(obj);
1059         KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1060         shmfd->shm_kmappings--;
1061         VM_OBJECT_WUNLOCK(obj);
1062         return (0);
1063 }
1064
1065 static int
1066 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
1067 {
1068         struct shmfd *shmfd;
1069
1070         kif->kf_type = KF_TYPE_SHM;
1071         shmfd = fp->f_data;
1072
1073         mtx_lock(&shm_timestamp_lock);
1074         kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode;    /* XXX */
1075         mtx_unlock(&shm_timestamp_lock);
1076         kif->kf_un.kf_file.kf_file_size = shmfd->shm_size;
1077         if (shmfd->shm_path != NULL) {
1078                 sx_slock(&shm_dict_lock);
1079                 if (shmfd->shm_path != NULL)
1080                         strlcpy(kif->kf_path, shmfd->shm_path,
1081                             sizeof(kif->kf_path));
1082                 sx_sunlock(&shm_dict_lock);
1083         }
1084         return (0);
1085 }