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/fcntl.h>
  53 #include <sys/file.h>
  54 #include <sys/filedesc.h>
  55 #include <sys/fnv_hash.h>
  56 #include <sys/kernel.h>
  57 #include <sys/uio.h>
  58 #include <sys/signal.h>
  59 #include <sys/ktrace.h>
  60 #include <sys/lock.h>
  61 #include <sys/malloc.h>
  62 #include <sys/mman.h>
  63 #include <sys/mutex.h>
  64 #include <sys/priv.h>
  65 #include <sys/proc.h>
  66 #include <sys/refcount.h>
  67 #include <sys/resourcevar.h>
  68 #include <sys/rwlock.h>
  69 #include <sys/stat.h>
  70 #include <sys/sysctl.h>
  71 #include <sys/sysproto.h>
  72 #include <sys/systm.h>
  73 #include <sys/sx.h>
  74 #include <sys/time.h>
  75 #include <sys/vnode.h>
  76 #include <sys/unistd.h>
  77
  78 #include <security/mac/mac_framework.h>
  79
  80 #include <vm/vm.h>
  81 #include <vm/vm_param.h>
  82 #include <vm/pmap.h>
  83 #include <vm/vm_extern.h>
  84 #include <vm/vm_map.h>
  85 #include <vm/vm_kern.h>
  86 #include <vm/vm_object.h>
  87 #include <vm/vm_page.h>
  88 #include <vm/vm_pageout.h>
  89 #include <vm/vm_pager.h>
  90 #include <vm/swap_pager.h>
  91
  92 struct shm_mapping {
  93         char            *sm_path;
  94         Fnv32_t         sm_fnv;
  95         struct shmfd    *sm_shmfd;
  96         LIST_ENTRY(shm_mapping) sm_link;
  97 };
  98
  99 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
 100 static LIST_HEAD(, shm_mapping) *shm_dictionary;
 101 static struct sx shm_dict_lock;
 102 static struct mtx shm_timestamp_lock;
 103 static u_long shm_hash;
 104
 105 #define SHM_HASH(fnv)   (&shm_dictionary[(fnv) & shm_hash])
 106
 107 static int      shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
 108 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
 109 static void     shm_dict_init(void *arg);
 110 static void     shm_drop(struct shmfd *shmfd);
 111 static struct shmfd *shm_hold(struct shmfd *shmfd);
 112 static void     shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
 113 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
 114 static int      shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
 115 static int      shm_dotruncate(struct shmfd *shmfd, off_t length);
 116
 117 static fo_rdwr_t        shm_read;
 118 static fo_rdwr_t        shm_write;
 119 static fo_truncate_t    shm_truncate;
 120 static fo_ioctl_t       shm_ioctl;
 121 static fo_poll_t        shm_poll;
 122 static fo_kqfilter_t    shm_kqfilter;
 123 static fo_stat_t        shm_stat;
 124 static fo_close_t       shm_close;
 125 static fo_chmod_t       shm_chmod;
 126 static fo_chown_t       shm_chown;
 127 static fo_seek_t        shm_seek;
 128
 129 /* File descriptor operations. */
 130 static struct fileops shm_ops = {
 131         .fo_read = shm_read,
 132         .fo_write = shm_write,
 133         .fo_truncate = shm_truncate,
 134         .fo_ioctl = shm_ioctl,
 135         .fo_poll = shm_poll,
 136         .fo_kqfilter = shm_kqfilter,
 137         .fo_stat = shm_stat,
 138         .fo_close = shm_close,
 139         .fo_chmod = shm_chmod,
 140         .fo_chown = shm_chown,
 141         .fo_sendfile = vn_sendfile,
 142         .fo_seek = shm_seek,
 143         .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
 144 };
 145
 146 FEATURE(posix_shm, "POSIX shared memory");
 147
 148 static int
 149 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
 150 {
 151         vm_page_t m;
 152         vm_pindex_t idx;
 153         size_t tlen;
 154         int error, offset, rv;
 155
 156         idx = OFF_TO_IDX(uio->uio_offset);
 157         offset = uio->uio_offset & PAGE_MASK;
 158         tlen = MIN(PAGE_SIZE - offset, len);
 159
 160         VM_OBJECT_WLOCK(obj);
 161
 162         /*
 163          * Parallel reads of the page content from disk are prevented
 164          * by exclusive busy.
 165          *
 166          * Although the tmpfs vnode lock is held here, it is
 167          * nonetheless safe to sleep waiting for a free page.  The
 168          * pageout daemon does not need to acquire the tmpfs vnode
 169          * lock to page out tobj's pages because tobj is a OBJT_SWAP
 170          * type object.
 171          */
 172         m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
 173         if (m->valid != VM_PAGE_BITS_ALL) {
 174                 if (vm_pager_has_page(obj, idx, NULL, NULL)) {
 175                         rv = vm_pager_get_pages(obj, &m, 1, 0);
 176                         m = vm_page_lookup(obj, idx);
 177                         if (m == NULL) {
 178                                 printf(
 179                     "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n",
 180                                     obj, idx, rv);
 181                                 VM_OBJECT_WUNLOCK(obj);
 182                                 return (EIO);
 183                         }
 184                         if (rv != VM_PAGER_OK) {
 185                                 printf(
 186             "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
 187                                     obj, idx, m->valid, rv);
 188                                 vm_page_lock(m);
 189                                 vm_page_free(m);
 190                                 vm_page_unlock(m);
 191                                 VM_OBJECT_WUNLOCK(obj);
 192                                 return (EIO);
 193                         }
 194                 } else
 195                         vm_page_zero_invalid(m, TRUE);
 196         }
 197         vm_page_xunbusy(m);
 198         vm_page_lock(m);
 199         vm_page_hold(m);
 200         if (m->queue == PQ_NONE) {
 201                 vm_page_deactivate(m);
 202         } else {
 203                 /* Requeue to maintain LRU ordering. */
 204                 vm_page_requeue(m);
 205         }
 206         vm_page_unlock(m);
 207         VM_OBJECT_WUNLOCK(obj);
 208         error = uiomove_fromphys(&m, offset, tlen, uio);
 209         if (uio->uio_rw == UIO_WRITE && error == 0) {
 210                 VM_OBJECT_WLOCK(obj);
 211                 vm_page_dirty(m);
 212                 vm_pager_page_unswapped(m);
 213                 VM_OBJECT_WUNLOCK(obj);
 214         }
 215         vm_page_lock(m);
 216         vm_page_unhold(m);
 217         vm_page_unlock(m);
 218
 219         return (error);
 220 }
 221
 222 int
 223 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
 224 {
 225         ssize_t resid;
 226         size_t len;
 227         int error;
 228
 229         error = 0;
 230         while ((resid = uio->uio_resid) > 0) {
 231                 if (obj_size <= uio->uio_offset)
 232                         break;
 233                 len = MIN(obj_size - uio->uio_offset, resid);
 234                 if (len == 0)
 235                         break;
 236                 error = uiomove_object_page(obj, len, uio);
 237                 if (error != 0 || resid == uio->uio_resid)
 238                         break;
 239         }
 240         return (error);
 241 }
 242
 243 static int
 244 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
 245 {
 246         struct shmfd *shmfd;
 247         off_t foffset;
 248         int error;
 249
 250         shmfd = fp->f_data;
 251         foffset = foffset_lock(fp, 0);
 252         error = 0;
 253         switch (whence) {
 254         case L_INCR:
 255                 if (foffset < 0 ||
 256                     (offset > 0 && foffset > OFF_MAX - offset)) {
 257                         error = EOVERFLOW;
 258                         break;
 259                 }
 260                 offset += foffset;
 261                 break;
 262         case L_XTND:
 263                 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
 264                         error = EOVERFLOW;
 265                         break;
 266                 }
 267                 offset += shmfd->shm_size;
 268                 break;
 269         case L_SET:
 270                 break;
 271         default:
 272                 error = EINVAL;
 273         }
 274         if (error == 0) {
 275                 if (offset < 0 || offset > shmfd->shm_size)
 276                         error = EINVAL;
 277                 else
 278                         td->td_uretoff.tdu_off = offset;
 279         }
 280         foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
 281         return (error);
 282 }
 283
 284 static int
 285 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 286     int flags, struct thread *td)
 287 {
 288         struct shmfd *shmfd;
 289         void *rl_cookie;
 290         int error;
 291
 292         shmfd = fp->f_data;
 293         foffset_lock_uio(fp, uio, flags);
 294         rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
 295             uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 296 #ifdef MAC
 297         error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
 298         if (error)
 299                 return (error);
 300 #endif
 301         error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
 302         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 303         foffset_unlock_uio(fp, uio, flags);
 304         return (error);
 305 }
 306
 307 static int
 308 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 309     int flags, struct thread *td)
 310 {
 311         struct shmfd *shmfd;
 312         void *rl_cookie;
 313         int error;
 314
 315         shmfd = fp->f_data;
 316 #ifdef MAC
 317         error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
 318         if (error)
 319                 return (error);
 320 #endif
 321         foffset_lock_uio(fp, uio, flags);
 322         if ((flags & FOF_OFFSET) == 0) {
 323                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
 324                     &shmfd->shm_mtx);
 325         } else {
 326                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
 327                     uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 328         }
 329
 330         error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
 331         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 332         foffset_unlock_uio(fp, uio, flags);
 333         return (error);
 334 }
 335
 336 static int
 337 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 338     struct thread *td)
 339 {
 340         struct shmfd *shmfd;
 341 #ifdef MAC
 342         int error;
 343 #endif
 344
 345         shmfd = fp->f_data;
 346 #ifdef MAC
 347         error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
 348         if (error)
 349                 return (error);
 350 #endif
 351         return (shm_dotruncate(shmfd, length));
 352 }
 353
 354 static int
 355 shm_ioctl(struct file *fp, u_long com, void *data,
 356     struct ucred *active_cred, struct thread *td)
 357 {
 358
 359         return (EOPNOTSUPP);
 360 }
 361
 362 static int
 363 shm_poll(struct file *fp, int events, struct ucred *active_cred,
 364     struct thread *td)
 365 {
 366
 367         return (EOPNOTSUPP);
 368 }
 369
 370 static int
 371 shm_kqfilter(struct file *fp, struct knote *kn)
 372 {
 373
 374         return (EOPNOTSUPP);
 375 }
 376
 377 static int
 378 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
 379     struct thread *td)
 380 {
 381         struct shmfd *shmfd;
 382 #ifdef MAC
 383         int error;
 384 #endif
 385
 386         shmfd = fp->f_data;
 387
 388 #ifdef MAC
 389         error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
 390         if (error)
 391                 return (error);
 392 #endif
 393
 394         /*
 395          * Attempt to return sanish values for fstat() on a memory file
 396          * descriptor.
 397          */
 398         bzero(sb, sizeof(*sb));
 399         sb->st_blksize = PAGE_SIZE;
 400         sb->st_size = shmfd->shm_size;
 401         sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
 402         mtx_lock(&shm_timestamp_lock);
 403         sb->st_atim = shmfd->shm_atime;
 404         sb->st_ctim = shmfd->shm_ctime;
 405         sb->st_mtim = shmfd->shm_mtime;
 406         sb->st_birthtim = shmfd->shm_birthtime;
 407         sb->st_mode = S_IFREG | shmfd->shm_mode;                /* XXX */
 408         sb->st_uid = shmfd->shm_uid;
 409         sb->st_gid = shmfd->shm_gid;
 410         mtx_unlock(&shm_timestamp_lock);
 411
 412         return (0);
 413 }
 414
 415 static int
 416 shm_close(struct file *fp, struct thread *td)
 417 {
 418         struct shmfd *shmfd;
 419
 420         shmfd = fp->f_data;
 421         fp->f_data = NULL;
 422         shm_drop(shmfd);
 423
 424         return (0);
 425 }
 426
 427 static int
 428 shm_dotruncate(struct shmfd *shmfd, off_t length)
 429 {
 430         vm_object_t object;
 431         vm_page_t m, ma[1];
 432         vm_pindex_t idx, nobjsize;
 433         vm_ooffset_t delta;
 434         int base, rv;
 435
 436         object = shmfd->shm_object;
 437         VM_OBJECT_WLOCK(object);
 438         if (length == shmfd->shm_size) {
 439                 VM_OBJECT_WUNLOCK(object);
 440                 return (0);
 441         }
 442         nobjsize = OFF_TO_IDX(length + PAGE_MASK);
 443
 444         /* Are we shrinking?  If so, trim the end. */
 445         if (length < shmfd->shm_size) {
 446                 /*
 447                  * Disallow any requests to shrink the size if this
 448                  * object is mapped into the kernel.
 449                  */
 450                 if (shmfd->shm_kmappings > 0) {
 451                         VM_OBJECT_WUNLOCK(object);
 452                         return (EBUSY);
 453                 }
 454
 455                 /*
 456                  * Zero the truncated part of the last page.
 457                  */
 458                 base = length & PAGE_MASK;
 459                 if (base != 0) {
 460                         idx = OFF_TO_IDX(length);
 461 retry:
 462                         m = vm_page_lookup(object, idx);
 463                         if (m != NULL) {
 464                                 if (vm_page_sleep_if_busy(m, "shmtrc"))
 465                                         goto retry;
 466                         } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
 467                                 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
 468                                 if (m == NULL) {
 469                                         VM_OBJECT_WUNLOCK(object);
 470                                         VM_WAIT;
 471                                         VM_OBJECT_WLOCK(object);
 472                                         goto retry;
 473                                 } else if (m->valid != VM_PAGE_BITS_ALL) {
 474                                         ma[0] = m;
 475                                         rv = vm_pager_get_pages(object, ma, 1,
 476                                             0);
 477                                         m = vm_page_lookup(object, idx);
 478                                 } else
 479                                         /* A cached page was reactivated. */
 480                                         rv = VM_PAGER_OK;
 481                                 vm_page_lock(m);
 482                                 if (rv == VM_PAGER_OK) {
 483                                         vm_page_deactivate(m);
 484                                         vm_page_unlock(m);
 485                                         vm_page_xunbusy(m);
 486                                 } else {
 487                                         vm_page_free(m);
 488                                         vm_page_unlock(m);
 489                                         VM_OBJECT_WUNLOCK(object);
 490                                         return (EIO);
 491                                 }
 492                         }
 493                         if (m != NULL) {
 494                                 pmap_zero_page_area(m, base, PAGE_SIZE - base);
 495                                 KASSERT(m->valid == VM_PAGE_BITS_ALL,
 496                                     ("shm_dotruncate: page %p is invalid", m));
 497                                 vm_page_dirty(m);
 498                                 vm_pager_page_unswapped(m);
 499                         }
 500                 }
 501                 delta = ptoa(object->size - nobjsize);
 502
 503                 /* Toss in memory pages. */
 504                 if (nobjsize < object->size)
 505                         vm_object_page_remove(object, nobjsize, object->size,
 506                             0);
 507
 508                 /* Toss pages from swap. */
 509                 if (object->type == OBJT_SWAP)
 510                         swap_pager_freespace(object, nobjsize, delta);
 511
 512                 /* Free the swap accounted for shm */
 513                 swap_release_by_cred(delta, object->cred);
 514                 object->charge -= delta;
 515         } else {
 516                 /* Attempt to reserve the swap */
 517                 delta = ptoa(nobjsize - object->size);
 518                 if (!swap_reserve_by_cred(delta, object->cred)) {
 519                         VM_OBJECT_WUNLOCK(object);
 520                         return (ENOMEM);
 521                 }
 522                 object->charge += delta;
 523         }
 524         shmfd->shm_size = length;
 525         mtx_lock(&shm_timestamp_lock);
 526         vfs_timestamp(&shmfd->shm_ctime);
 527         shmfd->shm_mtime = shmfd->shm_ctime;
 528         mtx_unlock(&shm_timestamp_lock);
 529         object->size = nobjsize;
 530         VM_OBJECT_WUNLOCK(object);
 531         return (0);
 532 }
 533
 534 /*
 535  * shmfd object management including creation and reference counting
 536  * routines.
 537  */
 538 static struct shmfd *
 539 shm_alloc(struct ucred *ucred, mode_t mode)
 540 {
 541         struct shmfd *shmfd;
 542
 543         shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
 544         shmfd->shm_size = 0;
 545         shmfd->shm_uid = ucred->cr_uid;
 546         shmfd->shm_gid = ucred->cr_gid;
 547         shmfd->shm_mode = mode;
 548         shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
 549             shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
 550         KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
 551         VM_OBJECT_WLOCK(shmfd->shm_object);
 552         vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
 553         vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
 554         VM_OBJECT_WUNLOCK(shmfd->shm_object);
 555         vfs_timestamp(&shmfd->shm_birthtime);
 556         shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
 557             shmfd->shm_birthtime;
 558         refcount_init(&shmfd->shm_refs, 1);
 559         mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
 560         rangelock_init(&shmfd->shm_rl);
 561 #ifdef MAC
 562         mac_posixshm_init(shmfd);
 563         mac_posixshm_create(ucred, shmfd);
 564 #endif
 565
 566         return (shmfd);
 567 }
 568
 569 static struct shmfd *
 570 shm_hold(struct shmfd *shmfd)
 571 {
 572
 573         refcount_acquire(&shmfd->shm_refs);
 574         return (shmfd);
 575 }
 576
 577 static void
 578 shm_drop(struct shmfd *shmfd)
 579 {
 580
 581         if (refcount_release(&shmfd->shm_refs)) {
 582 #ifdef MAC
 583                 mac_posixshm_destroy(shmfd);
 584 #endif
 585                 rangelock_destroy(&shmfd->shm_rl);
 586                 mtx_destroy(&shmfd->shm_mtx);
 587                 vm_object_deallocate(shmfd->shm_object);
 588                 free(shmfd, M_SHMFD);
 589         }
 590 }
 591
 592 /*
 593  * Determine if the credentials have sufficient permissions for a
 594  * specified combination of FREAD and FWRITE.
 595  */
 596 static int
 597 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
 598 {
 599         accmode_t accmode;
 600         int error;
 601
 602         accmode = 0;
 603         if (flags & FREAD)
 604                 accmode |= VREAD;
 605         if (flags & FWRITE)
 606                 accmode |= VWRITE;
 607         mtx_lock(&shm_timestamp_lock);
 608         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
 609             accmode, ucred, NULL);
 610         mtx_unlock(&shm_timestamp_lock);
 611         return (error);
 612 }
 613
 614 /*
 615  * Dictionary management.  We maintain an in-kernel dictionary to map
 616  * paths to shmfd objects.  We use the FNV hash on the path to store
 617  * the mappings in a hash table.
 618  */
 619 static void
 620 shm_dict_init(void *arg)
 621 {
 622
 623         mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
 624         sx_init(&shm_dict_lock, "shm dictionary");
 625         shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
 626 }
 627 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL);
 628
 629 static struct shmfd *
 630 shm_lookup(char *path, Fnv32_t fnv)
 631 {
 632         struct shm_mapping *map;
 633
 634         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 635                 if (map->sm_fnv != fnv)
 636                         continue;
 637                 if (strcmp(map->sm_path, path) == 0)
 638                         return (map->sm_shmfd);
 639         }
 640
 641         return (NULL);
 642 }
 643
 644 static void
 645 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
 646 {
 647         struct shm_mapping *map;
 648
 649         map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
 650         map->sm_path = path;
 651         map->sm_fnv = fnv;
 652         map->sm_shmfd = shm_hold(shmfd);
 653         shmfd->shm_path = path;
 654         LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
 655 }
 656
 657 static int
 658 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
 659 {
 660         struct shm_mapping *map;
 661         int error;
 662
 663         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 664                 if (map->sm_fnv != fnv)
 665                         continue;
 666                 if (strcmp(map->sm_path, path) == 0) {
 667 #ifdef MAC
 668                         error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
 669                         if (error)
 670                                 return (error);
 671 #endif
 672                         error = shm_access(map->sm_shmfd, ucred,
 673                             FREAD | FWRITE);
 674                         if (error)
 675                                 return (error);
 676                         map->sm_shmfd->shm_path = NULL;
 677                         LIST_REMOVE(map, sm_link);
 678                         shm_drop(map->sm_shmfd);
 679                         free(map->sm_path, M_SHMFD);
 680                         free(map, M_SHMFD);
 681                         return (0);
 682                 }
 683         }
 684
 685         return (ENOENT);
 686 }
 687
 688 /* System calls. */
 689 int
 690 sys_shm_open(struct thread *td, struct shm_open_args *uap)
 691 {
 692         struct filedesc *fdp;
 693         struct shmfd *shmfd;
 694         struct file *fp;
 695         char *path;
 696         Fnv32_t fnv;
 697         mode_t cmode;
 698         int fd, error;
 699
 700 #ifdef CAPABILITY_MODE
 701         /*
 702          * shm_open(2) is only allowed for anonymous objects.
 703          */
 704         if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON))
 705                 return (ECAPMODE);
 706 #endif
 707
 708         if ((uap->flags & O_ACCMODE) != O_RDONLY &&
 709             (uap->flags & O_ACCMODE) != O_RDWR)
 710                 return (EINVAL);
 711
 712         if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
 713                 return (EINVAL);
 714
 715         fdp = td->td_proc->p_fd;
 716         cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
 717
 718         error = falloc(td, &fp, &fd, O_CLOEXEC);
 719         if (error)
 720                 return (error);
 721
 722         /* A SHM_ANON path pointer creates an anonymous object. */
 723         if (uap->path == SHM_ANON) {
 724                 /* A read-only anonymous object is pointless. */
 725                 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
 726                         fdclose(fdp, fp, fd, td);
 727                         fdrop(fp, td);
 728                         return (EINVAL);
 729                 }
 730                 shmfd = shm_alloc(td->td_ucred, cmode);
 731         } else {
 732                 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
 733                 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
 734 #ifdef KTRACE
 735                 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
 736                         ktrnamei(path);
 737 #endif
 738                 /* Require paths to start with a '/' character. */
 739                 if (error == 0 && path[0] != '/')
 740                         error = EINVAL;
 741                 if (error) {
 742                         fdclose(fdp, fp, fd, td);
 743                         fdrop(fp, td);
 744                         free(path, M_SHMFD);
 745                         return (error);
 746                 }
 747
 748                 fnv = fnv_32_str(path, FNV1_32_INIT);
 749                 sx_xlock(&shm_dict_lock);
 750                 shmfd = shm_lookup(path, fnv);
 751                 if (shmfd == NULL) {
 752                         /* Object does not yet exist, create it if requested. */
 753                         if (uap->flags & O_CREAT) {
 754 #ifdef MAC
 755                                 error = mac_posixshm_check_create(td->td_ucred,
 756                                     path);
 757                                 if (error == 0) {
 758 #endif
 759                                         shmfd = shm_alloc(td->td_ucred, cmode);
 760                                         shm_insert(path, fnv, shmfd);
 761 #ifdef MAC
 762                                 }
 763 #endif
 764                         } else {
 765                                 free(path, M_SHMFD);
 766                                 error = ENOENT;
 767                         }
 768                 } else {
 769                         /*
 770                          * Object already exists, obtain a new
 771                          * reference if requested and permitted.
 772                          */
 773                         free(path, M_SHMFD);
 774                         if ((uap->flags & (O_CREAT | O_EXCL)) ==
 775                             (O_CREAT | O_EXCL))
 776                                 error = EEXIST;
 777                         else {
 778 #ifdef MAC
 779                                 error = mac_posixshm_check_open(td->td_ucred,
 780                                     shmfd, FFLAGS(uap->flags & O_ACCMODE));
 781                                 if (error == 0)
 782 #endif
 783                                 error = shm_access(shmfd, td->td_ucred,
 784                                     FFLAGS(uap->flags & O_ACCMODE));
 785                         }
 786
 787                         /*
 788                          * Truncate the file back to zero length if
 789                          * O_TRUNC was specified and the object was
 790                          * opened with read/write.
 791                          */
 792                         if (error == 0 &&
 793                             (uap->flags & (O_ACCMODE | O_TRUNC)) ==
 794                             (O_RDWR | O_TRUNC)) {
 795 #ifdef MAC
 796                                 error = mac_posixshm_check_truncate(
 797                                         td->td_ucred, fp->f_cred, shmfd);
 798                                 if (error == 0)
 799 #endif
 800                                         shm_dotruncate(shmfd, 0);
 801                         }
 802                         if (error == 0)
 803                                 shm_hold(shmfd);
 804                 }
 805                 sx_xunlock(&shm_dict_lock);
 806
 807                 if (error) {
 808                         fdclose(fdp, fp, fd, td);
 809                         fdrop(fp, td);
 810                         return (error);
 811                 }
 812         }
 813
 814         finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
 815
 816         td->td_retval[0] = fd;
 817         fdrop(fp, td);
 818
 819         return (0);
 820 }
 821
 822 int
 823 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
 824 {
 825         char *path;
 826         Fnv32_t fnv;
 827         int error;
 828
 829         path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
 830         error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
 831         if (error) {
 832                 free(path, M_TEMP);
 833                 return (error);
 834         }
 835 #ifdef KTRACE
 836         if (KTRPOINT(curthread, KTR_NAMEI))
 837                 ktrnamei(path);
 838 #endif
 839         fnv = fnv_32_str(path, FNV1_32_INIT);
 840         sx_xlock(&shm_dict_lock);
 841         error = shm_remove(path, fnv, td->td_ucred);
 842         sx_xunlock(&shm_dict_lock);
 843         free(path, M_TEMP);
 844
 845         return (error);
 846 }
 847
 848 /*
 849  * mmap() helper to validate mmap() requests against shm object state
 850  * and give mmap() the vm_object to use for the mapping.
 851  */
 852 int
 853 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
 854     vm_object_t *obj)
 855 {
 856
 857         /*
 858          * XXXRW: This validation is probably insufficient, and subject to
 859          * sign errors.  It should be fixed.
 860          */
 861         if (foff >= shmfd->shm_size ||
 862             foff + objsize > round_page(shmfd->shm_size))
 863                 return (EINVAL);
 864
 865         mtx_lock(&shm_timestamp_lock);
 866         vfs_timestamp(&shmfd->shm_atime);
 867         mtx_unlock(&shm_timestamp_lock);
 868         vm_object_reference(shmfd->shm_object);
 869         *obj = shmfd->shm_object;
 870         return (0);
 871 }
 872
 873 static int
 874 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
 875     struct thread *td)
 876 {
 877         struct shmfd *shmfd;
 878         int error;
 879
 880         error = 0;
 881         shmfd = fp->f_data;
 882         mtx_lock(&shm_timestamp_lock);
 883         /*
 884          * SUSv4 says that x bits of permission need not be affected.
 885          * Be consistent with our shm_open there.
 886          */
 887 #ifdef MAC
 888         error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
 889         if (error != 0)
 890                 goto out;
 891 #endif
 892         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
 893             shmfd->shm_gid, VADMIN, active_cred, NULL);
 894         if (error != 0)
 895                 goto out;
 896         shmfd->shm_mode = mode & ACCESSPERMS;
 897 out:
 898         mtx_unlock(&shm_timestamp_lock);
 899         return (error);
 900 }
 901
 902 static int
 903 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
 904     struct thread *td)
 905 {
 906         struct shmfd *shmfd;
 907         int error;
 908
 909         error = 0;
 910         shmfd = fp->f_data;
 911         mtx_lock(&shm_timestamp_lock);
 912 #ifdef MAC
 913         error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
 914         if (error != 0)
 915                 goto out;
 916 #endif
 917         if (uid == (uid_t)-1)
 918                 uid = shmfd->shm_uid;
 919         if (gid == (gid_t)-1)
 920                  gid = shmfd->shm_gid;
 921         if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
 922             (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
 923             (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
 924                 goto out;
 925         shmfd->shm_uid = uid;
 926         shmfd->shm_gid = gid;
 927 out:
 928         mtx_unlock(&shm_timestamp_lock);
 929         return (error);
 930 }
 931
 932 /*
 933  * Helper routines to allow the backing object of a shared memory file
 934  * descriptor to be mapped in the kernel.
 935  */
 936 int
 937 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
 938 {
 939         struct shmfd *shmfd;
 940         vm_offset_t kva, ofs;
 941         vm_object_t obj;
 942         int rv;
 943
 944         if (fp->f_type != DTYPE_SHM)
 945                 return (EINVAL);
 946         shmfd = fp->f_data;
 947         obj = shmfd->shm_object;
 948         VM_OBJECT_WLOCK(obj);
 949         /*
 950          * XXXRW: This validation is probably insufficient, and subject to
 951          * sign errors.  It should be fixed.
 952          */
 953         if (offset >= shmfd->shm_size ||
 954             offset + size > round_page(shmfd->shm_size)) {
 955                 VM_OBJECT_WUNLOCK(obj);
 956                 return (EINVAL);
 957         }
 958
 959         shmfd->shm_kmappings++;
 960         vm_object_reference_locked(obj);
 961         VM_OBJECT_WUNLOCK(obj);
 962
 963         /* Map the object into the kernel_map and wire it. */
 964         kva = vm_map_min(kernel_map);
 965         ofs = offset & PAGE_MASK;
 966         offset = trunc_page(offset);
 967         size = round_page(size + ofs);
 968         rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
 969             VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
 970             VM_PROT_READ | VM_PROT_WRITE, 0);
 971         if (rv == KERN_SUCCESS) {
 972                 rv = vm_map_wire(kernel_map, kva, kva + size,
 973                     VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
 974                 if (rv == KERN_SUCCESS) {
 975                         *memp = (void *)(kva + ofs);
 976                         return (0);
 977                 }
 978                 vm_map_remove(kernel_map, kva, kva + size);
 979         } else
 980                 vm_object_deallocate(obj);
 981
 982         /* On failure, drop our mapping reference. */
 983         VM_OBJECT_WLOCK(obj);
 984         shmfd->shm_kmappings--;
 985         VM_OBJECT_WUNLOCK(obj);
 986
 987         return (vm_mmap_to_errno(rv));
 988 }
 989
 990 /*
 991  * We require the caller to unmap the entire entry.  This allows us to
 992  * safely decrement shm_kmappings when a mapping is removed.
 993  */
 994 int
 995 shm_unmap(struct file *fp, void *mem, size_t size)
 996 {
 997         struct shmfd *shmfd;
 998         vm_map_entry_t entry;
 999         vm_offset_t kva, ofs;
1000         vm_object_t obj;
1001         vm_pindex_t pindex;
1002         vm_prot_t prot;
1003         boolean_t wired;
1004         vm_map_t map;
1005         int rv;
1006
1007         if (fp->f_type != DTYPE_SHM)
1008                 return (EINVAL);
1009         shmfd = fp->f_data;
1010         kva = (vm_offset_t)mem;
1011         ofs = kva & PAGE_MASK;
1012         kva = trunc_page(kva);
1013         size = round_page(size + ofs);
1014         map = kernel_map;
1015         rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1016             &obj, &pindex, &prot, &wired);
1017         if (rv != KERN_SUCCESS)
1018                 return (EINVAL);
1019         if (entry->start != kva || entry->end != kva + size) {
1020                 vm_map_lookup_done(map, entry);
1021                 return (EINVAL);
1022         }
1023         vm_map_lookup_done(map, entry);
1024         if (obj != shmfd->shm_object)
1025                 return (EINVAL);
1026         vm_map_remove(map, kva, kva + size);
1027         VM_OBJECT_WLOCK(obj);
1028         KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1029         shmfd->shm_kmappings--;
1030         VM_OBJECT_WUNLOCK(obj);
1031         return (0);
1032 }
1033
1034 void
1035 shm_path(struct shmfd *shmfd, char *path, size_t size)
1036 {
1037
1038         if (shmfd->shm_path == NULL)
1039                 return;
1040         sx_slock(&shm_dict_lock);
1041         if (shmfd->shm_path != NULL)
1042                 strlcpy(path, shmfd->shm_path, size);
1043         sx_sunlock(&shm_dict_lock);
1044 }