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
  73 #include <security/mac/mac_framework.h>
  74
  75 #include <vm/vm.h>
  76 #include <vm/vm_param.h>
  77 #include <vm/pmap.h>
  78 #include <vm/vm_extern.h>
  79 #include <vm/vm_map.h>
  80 #include <vm/vm_kern.h>
  81 #include <vm/vm_object.h>
  82 #include <vm/vm_page.h>
  83 #include <vm/vm_pageout.h>
  84 #include <vm/vm_pager.h>
  85 #include <vm/swap_pager.h>
  86
  87 struct shm_mapping {
  88         char            *sm_path;
  89         Fnv32_t         sm_fnv;
  90         struct shmfd    *sm_shmfd;
  91         LIST_ENTRY(shm_mapping) sm_link;
  92 };
  93
  94 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
  95 static LIST_HEAD(, shm_mapping) *shm_dictionary;
  96 static struct sx shm_dict_lock;
  97 static struct mtx shm_timestamp_lock;
  98 static u_long shm_hash;
  99
 100 #define SHM_HASH(fnv)   (&shm_dictionary[(fnv) & shm_hash])
 101
 102 static int      shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
 103 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
 104 static void     shm_dict_init(void *arg);
 105 static void     shm_drop(struct shmfd *shmfd);
 106 static struct shmfd *shm_hold(struct shmfd *shmfd);
 107 static void     shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
 108 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
 109 static int      shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
 110 static int      shm_dotruncate(struct shmfd *shmfd, off_t length);
 111
 112 static fo_rdwr_t        shm_read;
 113 static fo_rdwr_t        shm_write;
 114 static fo_truncate_t    shm_truncate;
 115 static fo_ioctl_t       shm_ioctl;
 116 static fo_poll_t        shm_poll;
 117 static fo_kqfilter_t    shm_kqfilter;
 118 static fo_stat_t        shm_stat;
 119 static fo_close_t       shm_close;
 120 static fo_chmod_t       shm_chmod;
 121 static fo_chown_t       shm_chown;
 122
 123 /* File descriptor operations. */
 124 static struct fileops shm_ops = {
 125         .fo_read = shm_read,
 126         .fo_write = shm_write,
 127         .fo_truncate = shm_truncate,
 128         .fo_ioctl = shm_ioctl,
 129         .fo_poll = shm_poll,
 130         .fo_kqfilter = shm_kqfilter,
 131         .fo_stat = shm_stat,
 132         .fo_close = shm_close,
 133         .fo_chmod = shm_chmod,
 134         .fo_chown = shm_chown,
 135         .fo_flags = DFLAG_PASSABLE
 136 };
 137
 138 FEATURE(posix_shm, "POSIX shared memory");
 139
 140 static int
 141 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 142     int flags, struct thread *td)
 143 {
 144
 145         return (EOPNOTSUPP);
 146 }
 147
 148 static int
 149 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 150     int flags, struct thread *td)
 151 {
 152
 153         return (EOPNOTSUPP);
 154 }
 155
 156 static int
 157 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 158     struct thread *td)
 159 {
 160         struct shmfd *shmfd;
 161 #ifdef MAC
 162         int error;
 163 #endif
 164
 165         shmfd = fp->f_data;
 166 #ifdef MAC
 167         error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
 168         if (error)
 169                 return (error);
 170 #endif
 171         return (shm_dotruncate(shmfd, length));
 172 }
 173
 174 static int
 175 shm_ioctl(struct file *fp, u_long com, void *data,
 176     struct ucred *active_cred, struct thread *td)
 177 {
 178
 179         return (EOPNOTSUPP);
 180 }
 181
 182 static int
 183 shm_poll(struct file *fp, int events, struct ucred *active_cred,
 184     struct thread *td)
 185 {
 186
 187         return (EOPNOTSUPP);
 188 }
 189
 190 static int
 191 shm_kqfilter(struct file *fp, struct knote *kn)
 192 {
 193
 194         return (EOPNOTSUPP);
 195 }
 196
 197 static int
 198 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
 199     struct thread *td)
 200 {
 201         struct shmfd *shmfd;
 202 #ifdef MAC
 203         int error;
 204 #endif
 205
 206         shmfd = fp->f_data;
 207
 208 #ifdef MAC
 209         error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
 210         if (error)
 211                 return (error);
 212 #endif
 213
 214         /*
 215          * Attempt to return sanish values for fstat() on a memory file
 216          * descriptor.
 217          */
 218         bzero(sb, sizeof(*sb));
 219         sb->st_blksize = PAGE_SIZE;
 220         sb->st_size = shmfd->shm_size;
 221         sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
 222         mtx_lock(&shm_timestamp_lock);
 223         sb->st_atim = shmfd->shm_atime;
 224         sb->st_ctim = shmfd->shm_ctime;
 225         sb->st_mtim = shmfd->shm_mtime;
 226         sb->st_birthtim = shmfd->shm_birthtime;
 227         sb->st_mode = S_IFREG | shmfd->shm_mode;                /* XXX */
 228         sb->st_uid = shmfd->shm_uid;
 229         sb->st_gid = shmfd->shm_gid;
 230         mtx_unlock(&shm_timestamp_lock);
 231
 232         return (0);
 233 }
 234
 235 static int
 236 shm_close(struct file *fp, struct thread *td)
 237 {
 238         struct shmfd *shmfd;
 239
 240         shmfd = fp->f_data;
 241         fp->f_data = NULL;
 242         shm_drop(shmfd);
 243
 244         return (0);
 245 }
 246
 247 static int
 248 shm_dotruncate(struct shmfd *shmfd, off_t length)
 249 {
 250         vm_object_t object;
 251         vm_page_t m, ma[1];
 252         vm_pindex_t idx, nobjsize;
 253         vm_ooffset_t delta;
 254         int base, rv;
 255
 256         object = shmfd->shm_object;
 257         VM_OBJECT_WLOCK(object);
 258         if (length == shmfd->shm_size) {
 259                 VM_OBJECT_WUNLOCK(object);
 260                 return (0);
 261         }
 262         nobjsize = OFF_TO_IDX(length + PAGE_MASK);
 263
 264         /* Are we shrinking?  If so, trim the end. */
 265         if (length < shmfd->shm_size) {
 266                 /*
 267                  * Disallow any requests to shrink the size if this
 268                  * object is mapped into the kernel.
 269                  */
 270                 if (shmfd->shm_kmappings > 0) {
 271                         VM_OBJECT_WUNLOCK(object);
 272                         return (EBUSY);
 273                 }
 274
 275                 /*
 276                  * Zero the truncated part of the last page.
 277                  */
 278                 base = length & PAGE_MASK;
 279                 if (base != 0) {
 280                         idx = OFF_TO_IDX(length);
 281 retry:
 282                         m = vm_page_lookup(object, idx);
 283                         if (m != NULL) {
 284                                 if ((m->oflags & VPO_BUSY) != 0 ||
 285                                     m->busy != 0) {
 286                                         vm_page_sleep(m, "shmtrc");
 287                                         goto retry;
 288                                 }
 289                         } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
 290                                 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
 291                                 if (m == NULL) {
 292                                         VM_OBJECT_WUNLOCK(object);
 293                                         VM_WAIT;
 294                                         VM_OBJECT_WLOCK(object);
 295                                         goto retry;
 296                                 } else if (m->valid != VM_PAGE_BITS_ALL) {
 297                                         ma[0] = m;
 298                                         rv = vm_pager_get_pages(object, ma, 1,
 299                                             0);
 300                                         m = vm_page_lookup(object, idx);
 301                                 } else
 302                                         /* A cached page was reactivated. */
 303                                         rv = VM_PAGER_OK;
 304                                 vm_page_lock(m);
 305                                 if (rv == VM_PAGER_OK) {
 306                                         vm_page_deactivate(m);
 307                                         vm_page_unlock(m);
 308                                         vm_page_wakeup(m);
 309                                 } else {
 310                                         vm_page_free(m);
 311                                         vm_page_unlock(m);
 312                                         VM_OBJECT_WUNLOCK(object);
 313                                         return (EIO);
 314                                 }
 315                         }
 316                         if (m != NULL) {
 317                                 pmap_zero_page_area(m, base, PAGE_SIZE - base);
 318                                 KASSERT(m->valid == VM_PAGE_BITS_ALL,
 319                                     ("shm_dotruncate: page %p is invalid", m));
 320                                 vm_page_dirty(m);
 321                                 vm_pager_page_unswapped(m);
 322                         }
 323                 }
 324                 delta = ptoa(object->size - nobjsize);
 325
 326                 /* Toss in memory pages. */
 327                 if (nobjsize < object->size)
 328                         vm_object_page_remove(object, nobjsize, object->size,
 329                             0);
 330
 331                 /* Toss pages from swap. */
 332                 if (object->type == OBJT_SWAP)
 333                         swap_pager_freespace(object, nobjsize, delta);
 334
 335                 /* Free the swap accounted for shm */
 336                 swap_release_by_cred(delta, object->cred);
 337                 object->charge -= delta;
 338         } else {
 339                 /* Attempt to reserve the swap */
 340                 delta = ptoa(nobjsize - object->size);
 341                 if (!swap_reserve_by_cred(delta, object->cred)) {
 342                         VM_OBJECT_WUNLOCK(object);
 343                         return (ENOMEM);
 344                 }
 345                 object->charge += delta;
 346         }
 347         shmfd->shm_size = length;
 348         mtx_lock(&shm_timestamp_lock);
 349         vfs_timestamp(&shmfd->shm_ctime);
 350         shmfd->shm_mtime = shmfd->shm_ctime;
 351         mtx_unlock(&shm_timestamp_lock);
 352         object->size = nobjsize;
 353         VM_OBJECT_WUNLOCK(object);
 354         return (0);
 355 }
 356
 357 /*
 358  * shmfd object management including creation and reference counting
 359  * routines.
 360  */
 361 static struct shmfd *
 362 shm_alloc(struct ucred *ucred, mode_t mode)
 363 {
 364         struct shmfd *shmfd;
 365
 366         shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
 367         shmfd->shm_size = 0;
 368         shmfd->shm_uid = ucred->cr_uid;
 369         shmfd->shm_gid = ucred->cr_gid;
 370         shmfd->shm_mode = mode;
 371         shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
 372             shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
 373         KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
 374         VM_OBJECT_WLOCK(shmfd->shm_object);
 375         vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
 376         vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
 377         VM_OBJECT_WUNLOCK(shmfd->shm_object);
 378         vfs_timestamp(&shmfd->shm_birthtime);
 379         shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
 380             shmfd->shm_birthtime;
 381         refcount_init(&shmfd->shm_refs, 1);
 382 #ifdef MAC
 383         mac_posixshm_init(shmfd);
 384         mac_posixshm_create(ucred, shmfd);
 385 #endif
 386
 387         return (shmfd);
 388 }
 389
 390 static struct shmfd *
 391 shm_hold(struct shmfd *shmfd)
 392 {
 393
 394         refcount_acquire(&shmfd->shm_refs);
 395         return (shmfd);
 396 }
 397
 398 static void
 399 shm_drop(struct shmfd *shmfd)
 400 {
 401
 402         if (refcount_release(&shmfd->shm_refs)) {
 403 #ifdef MAC
 404                 mac_posixshm_destroy(shmfd);
 405 #endif
 406                 vm_object_deallocate(shmfd->shm_object);
 407                 free(shmfd, M_SHMFD);
 408         }
 409 }
 410
 411 /*
 412  * Determine if the credentials have sufficient permissions for a
 413  * specified combination of FREAD and FWRITE.
 414  */
 415 static int
 416 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
 417 {
 418         accmode_t accmode;
 419         int error;
 420
 421         accmode = 0;
 422         if (flags & FREAD)
 423                 accmode |= VREAD;
 424         if (flags & FWRITE)
 425                 accmode |= VWRITE;
 426         mtx_lock(&shm_timestamp_lock);
 427         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
 428             accmode, ucred, NULL);
 429         mtx_unlock(&shm_timestamp_lock);
 430         return (error);
 431 }
 432
 433 /*
 434  * Dictionary management.  We maintain an in-kernel dictionary to map
 435  * paths to shmfd objects.  We use the FNV hash on the path to store
 436  * the mappings in a hash table.
 437  */
 438 static void
 439 shm_dict_init(void *arg)
 440 {
 441
 442         mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
 443         sx_init(&shm_dict_lock, "shm dictionary");
 444         shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
 445 }
 446 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL);
 447
 448 static struct shmfd *
 449 shm_lookup(char *path, Fnv32_t fnv)
 450 {
 451         struct shm_mapping *map;
 452
 453         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 454                 if (map->sm_fnv != fnv)
 455                         continue;
 456                 if (strcmp(map->sm_path, path) == 0)
 457                         return (map->sm_shmfd);
 458         }
 459
 460         return (NULL);
 461 }
 462
 463 static void
 464 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
 465 {
 466         struct shm_mapping *map;
 467
 468         map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
 469         map->sm_path = path;
 470         map->sm_fnv = fnv;
 471         map->sm_shmfd = shm_hold(shmfd);
 472         shmfd->shm_path = path;
 473         LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
 474 }
 475
 476 static int
 477 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
 478 {
 479         struct shm_mapping *map;
 480         int error;
 481
 482         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 483                 if (map->sm_fnv != fnv)
 484                         continue;
 485                 if (strcmp(map->sm_path, path) == 0) {
 486 #ifdef MAC
 487                         error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
 488                         if (error)
 489                                 return (error);
 490 #endif
 491                         error = shm_access(map->sm_shmfd, ucred,
 492                             FREAD | FWRITE);
 493                         if (error)
 494                                 return (error);
 495                         map->sm_shmfd->shm_path = NULL;
 496                         LIST_REMOVE(map, sm_link);
 497                         shm_drop(map->sm_shmfd);
 498                         free(map->sm_path, M_SHMFD);
 499                         free(map, M_SHMFD);
 500                         return (0);
 501                 }
 502         }
 503
 504         return (ENOENT);
 505 }
 506
 507 /* System calls. */
 508 int
 509 sys_shm_open(struct thread *td, struct shm_open_args *uap)
 510 {
 511         struct filedesc *fdp;
 512         struct shmfd *shmfd;
 513         struct file *fp;
 514         char *path;
 515         Fnv32_t fnv;
 516         mode_t cmode;
 517         int fd, error;
 518
 519 #ifdef CAPABILITY_MODE
 520         /*
 521          * shm_open(2) is only allowed for anonymous objects.
 522          */
 523         if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON))
 524                 return (ECAPMODE);
 525 #endif
 526
 527         if ((uap->flags & O_ACCMODE) != O_RDONLY &&
 528             (uap->flags & O_ACCMODE) != O_RDWR)
 529                 return (EINVAL);
 530
 531         if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0)
 532                 return (EINVAL);
 533
 534         fdp = td->td_proc->p_fd;
 535         cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
 536
 537         error = falloc(td, &fp, &fd, O_CLOEXEC);
 538         if (error)
 539                 return (error);
 540
 541         /* A SHM_ANON path pointer creates an anonymous object. */
 542         if (uap->path == SHM_ANON) {
 543                 /* A read-only anonymous object is pointless. */
 544                 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
 545                         fdclose(fdp, fp, fd, td);
 546                         fdrop(fp, td);
 547                         return (EINVAL);
 548                 }
 549                 shmfd = shm_alloc(td->td_ucred, cmode);
 550         } else {
 551                 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
 552                 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
 553
 554                 /* Require paths to start with a '/' character. */
 555                 if (error == 0 && path[0] != '/')
 556                         error = EINVAL;
 557                 if (error) {
 558                         fdclose(fdp, fp, fd, td);
 559                         fdrop(fp, td);
 560                         free(path, M_SHMFD);
 561                         return (error);
 562                 }
 563
 564                 fnv = fnv_32_str(path, FNV1_32_INIT);
 565                 sx_xlock(&shm_dict_lock);
 566                 shmfd = shm_lookup(path, fnv);
 567                 if (shmfd == NULL) {
 568                         /* Object does not yet exist, create it if requested. */
 569                         if (uap->flags & O_CREAT) {
 570 #ifdef MAC
 571                                 error = mac_posixshm_check_create(td->td_ucred,
 572                                     path);
 573                                 if (error == 0) {
 574 #endif
 575                                         shmfd = shm_alloc(td->td_ucred, cmode);
 576                                         shm_insert(path, fnv, shmfd);
 577 #ifdef MAC
 578                                 }
 579 #endif
 580                         } else {
 581                                 free(path, M_SHMFD);
 582                                 error = ENOENT;
 583                         }
 584                 } else {
 585                         /*
 586                          * Object already exists, obtain a new
 587                          * reference if requested and permitted.
 588                          */
 589                         free(path, M_SHMFD);
 590                         if ((uap->flags & (O_CREAT | O_EXCL)) ==
 591                             (O_CREAT | O_EXCL))
 592                                 error = EEXIST;
 593                         else {
 594 #ifdef MAC
 595                                 error = mac_posixshm_check_open(td->td_ucred,
 596                                     shmfd, FFLAGS(uap->flags & O_ACCMODE));
 597                                 if (error == 0)
 598 #endif
 599                                 error = shm_access(shmfd, td->td_ucred,
 600                                     FFLAGS(uap->flags & O_ACCMODE));
 601                         }
 602
 603                         /*
 604                          * Truncate the file back to zero length if
 605                          * O_TRUNC was specified and the object was
 606                          * opened with read/write.
 607                          */
 608                         if (error == 0 &&
 609                             (uap->flags & (O_ACCMODE | O_TRUNC)) ==
 610                             (O_RDWR | O_TRUNC)) {
 611 #ifdef MAC
 612                                 error = mac_posixshm_check_truncate(
 613                                         td->td_ucred, fp->f_cred, shmfd);
 614                                 if (error == 0)
 615 #endif
 616                                         shm_dotruncate(shmfd, 0);
 617                         }
 618                         if (error == 0)
 619                                 shm_hold(shmfd);
 620                 }
 621                 sx_xunlock(&shm_dict_lock);
 622
 623                 if (error) {
 624                         fdclose(fdp, fp, fd, td);
 625                         fdrop(fp, td);
 626                         return (error);
 627                 }
 628         }
 629
 630         finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
 631
 632         td->td_retval[0] = fd;
 633         fdrop(fp, td);
 634
 635         return (0);
 636 }
 637
 638 int
 639 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
 640 {
 641         char *path;
 642         Fnv32_t fnv;
 643         int error;
 644
 645         path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
 646         error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
 647         if (error) {
 648                 free(path, M_TEMP);
 649                 return (error);
 650         }
 651
 652         fnv = fnv_32_str(path, FNV1_32_INIT);
 653         sx_xlock(&shm_dict_lock);
 654         error = shm_remove(path, fnv, td->td_ucred);
 655         sx_xunlock(&shm_dict_lock);
 656         free(path, M_TEMP);
 657
 658         return (error);
 659 }
 660
 661 /*
 662  * mmap() helper to validate mmap() requests against shm object state
 663  * and give mmap() the vm_object to use for the mapping.
 664  */
 665 int
 666 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
 667     vm_object_t *obj)
 668 {
 669
 670         /*
 671          * XXXRW: This validation is probably insufficient, and subject to
 672          * sign errors.  It should be fixed.
 673          */
 674         if (foff >= shmfd->shm_size ||
 675             foff + objsize > round_page(shmfd->shm_size))
 676                 return (EINVAL);
 677
 678         mtx_lock(&shm_timestamp_lock);
 679         vfs_timestamp(&shmfd->shm_atime);
 680         mtx_unlock(&shm_timestamp_lock);
 681         vm_object_reference(shmfd->shm_object);
 682         *obj = shmfd->shm_object;
 683         return (0);
 684 }
 685
 686 static int
 687 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
 688     struct thread *td)
 689 {
 690         struct shmfd *shmfd;
 691         int error;
 692
 693         error = 0;
 694         shmfd = fp->f_data;
 695         mtx_lock(&shm_timestamp_lock);
 696         /*
 697          * SUSv4 says that x bits of permission need not be affected.
 698          * Be consistent with our shm_open there.
 699          */
 700 #ifdef MAC
 701         error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
 702         if (error != 0)
 703                 goto out;
 704 #endif
 705         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
 706             shmfd->shm_gid, VADMIN, active_cred, NULL);
 707         if (error != 0)
 708                 goto out;
 709         shmfd->shm_mode = mode & ACCESSPERMS;
 710 out:
 711         mtx_unlock(&shm_timestamp_lock);
 712         return (error);
 713 }
 714
 715 static int
 716 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
 717     struct thread *td)
 718 {
 719         struct shmfd *shmfd;
 720         int error;
 721
 722         error = 0;
 723         shmfd = fp->f_data;
 724         mtx_lock(&shm_timestamp_lock);
 725 #ifdef MAC
 726         error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
 727         if (error != 0)
 728                 goto out;
 729 #endif
 730         if (uid == (uid_t)-1)
 731                 uid = shmfd->shm_uid;
 732         if (gid == (gid_t)-1)
 733                  gid = shmfd->shm_gid;
 734         if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
 735             (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
 736             (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
 737                 goto out;
 738         shmfd->shm_uid = uid;
 739         shmfd->shm_gid = gid;
 740 out:
 741         mtx_unlock(&shm_timestamp_lock);
 742         return (error);
 743 }
 744
 745 /*
 746  * Helper routines to allow the backing object of a shared memory file
 747  * descriptor to be mapped in the kernel.
 748  */
 749 int
 750 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
 751 {
 752         struct shmfd *shmfd;
 753         vm_offset_t kva, ofs;
 754         vm_object_t obj;
 755         int rv;
 756
 757         if (fp->f_type != DTYPE_SHM)
 758                 return (EINVAL);
 759         shmfd = fp->f_data;
 760         obj = shmfd->shm_object;
 761         VM_OBJECT_WLOCK(obj);
 762         /*
 763          * XXXRW: This validation is probably insufficient, and subject to
 764          * sign errors.  It should be fixed.
 765          */
 766         if (offset >= shmfd->shm_size ||
 767             offset + size > round_page(shmfd->shm_size)) {
 768                 VM_OBJECT_WUNLOCK(obj);
 769                 return (EINVAL);
 770         }
 771
 772         shmfd->shm_kmappings++;
 773         vm_object_reference_locked(obj);
 774         VM_OBJECT_WUNLOCK(obj);
 775
 776         /* Map the object into the kernel_map and wire it. */
 777         kva = vm_map_min(kernel_map);
 778         ofs = offset & PAGE_MASK;
 779         offset = trunc_page(offset);
 780         size = round_page(size + ofs);
 781         rv = vm_map_find(kernel_map, obj, offset, &kva, size,
 782             VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
 783             VM_PROT_READ | VM_PROT_WRITE, 0);
 784         if (rv == KERN_SUCCESS) {
 785                 rv = vm_map_wire(kernel_map, kva, kva + size,
 786                     VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
 787                 if (rv == KERN_SUCCESS) {
 788                         *memp = (void *)(kva + ofs);
 789                         return (0);
 790                 }
 791                 vm_map_remove(kernel_map, kva, kva + size);
 792         } else
 793                 vm_object_deallocate(obj);
 794
 795         /* On failure, drop our mapping reference. */
 796         VM_OBJECT_WLOCK(obj);
 797         shmfd->shm_kmappings--;
 798         VM_OBJECT_WUNLOCK(obj);
 799
 800         return (vm_mmap_to_errno(rv));
 801 }
 802
 803 /*
 804  * We require the caller to unmap the entire entry.  This allows us to
 805  * safely decrement shm_kmappings when a mapping is removed.
 806  */
 807 int
 808 shm_unmap(struct file *fp, void *mem, size_t size)
 809 {
 810         struct shmfd *shmfd;
 811         vm_map_entry_t entry;
 812         vm_offset_t kva, ofs;
 813         vm_object_t obj;
 814         vm_pindex_t pindex;
 815         vm_prot_t prot;
 816         boolean_t wired;
 817         vm_map_t map;
 818         int rv;
 819
 820         if (fp->f_type != DTYPE_SHM)
 821                 return (EINVAL);
 822         shmfd = fp->f_data;
 823         kva = (vm_offset_t)mem;
 824         ofs = kva & PAGE_MASK;
 825         kva = trunc_page(kva);
 826         size = round_page(size + ofs);
 827         map = kernel_map;
 828         rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
 829             &obj, &pindex, &prot, &wired);
 830         if (rv != KERN_SUCCESS)
 831                 return (EINVAL);
 832         if (entry->start != kva || entry->end != kva + size) {
 833                 vm_map_lookup_done(map, entry);
 834                 return (EINVAL);
 835         }
 836         vm_map_lookup_done(map, entry);
 837         if (obj != shmfd->shm_object)
 838                 return (EINVAL);
 839         vm_map_remove(map, kva, kva + size);
 840         VM_OBJECT_WLOCK(obj);
 841         KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
 842         shmfd->shm_kmappings--;
 843         VM_OBJECT_WUNLOCK(obj);
 844         return (0);
 845 }
 846
 847 void
 848 shm_path(struct shmfd *shmfd, char *path, size_t size)
 849 {
 850
 851         if (shmfd->shm_path == NULL)
 852                 return;
 853         sx_slock(&shm_dict_lock);
 854         if (shmfd->shm_path != NULL)
 855                 strlcpy(path, shmfd->shm_path, size);
 856         sx_sunlock(&shm_dict_lock);
 857 }