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