The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_shm.c

Version: -  FREEBSD  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-2  -  FREEBSD-11-1  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-4  -  FREEBSD-10-3  -  FREEBSD-10-2  -  FREEBSD-10-1  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-3  -  FREEBSD-9-2  -  FREEBSD-9-1  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-4  -  FREEBSD-8-3  -  FREEBSD-8-2  -  FREEBSD-8-1  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-4  -  FREEBSD-7-3  -  FREEBSD-7-2  -  FREEBSD-7-1  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-4  -  FREEBSD-6-3  -  FREEBSD-6-2  -  FREEBSD-6-1  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-5  -  FREEBSD-5-4  -  FREEBSD-5-3  -  FREEBSD-5-2  -  FREEBSD-5-1  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  linux-2.6  -  linux-2.4.22  -  MK83  -  MK84  -  PLAN9  -  DFBSD  -  NETBSD  -  NETBSD5  -  NETBSD4  -  NETBSD3  -  NETBSD20  -  OPENBSD  -  xnu-517  -  xnu-792  -  xnu-792.6.70  -  xnu-1228  -  xnu-1456.1.26  -  xnu-1699.24.8  -  xnu-2050.18.24  -  OPENSOLARIS  -  minix-3-1-1 
SearchContext: -  none  -  3  -  10 

    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: releng/10.0/sys/kern/uipc_shm.c 255467 2013-09-11 06:41:15Z kib $");
   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 }

Cache object: 1fa60e4018ecb9023ade50b6c7861b5b


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.