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