FreeBSD/Linux Kernel Cross Reference
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: releng/10.2/sys/kern/uipc_shm.c 281778 2015-04-20 17:43:36Z alc $");
46
47 #include "opt_capsicum.h"
48 #include "opt_ktrace.h"
49
50 #include <sys/param.h>
51 #include <sys/capsicum.h>
52 #include <sys/conf.h>
53 #include <sys/fcntl.h>
54 #include <sys/file.h>
55 #include <sys/filedesc.h>
56 #include <sys/fnv_hash.h>
57 #include <sys/kernel.h>
58 #include <sys/uio.h>
59 #include <sys/signal.h>
60 #include <sys/ktrace.h>
61 #include <sys/lock.h>
62 #include <sys/malloc.h>
63 #include <sys/mman.h>
64 #include <sys/mutex.h>
65 #include <sys/priv.h>
66 #include <sys/proc.h>
67 #include <sys/refcount.h>
68 #include <sys/resourcevar.h>
69 #include <sys/rwlock.h>
70 #include <sys/stat.h>
71 #include <sys/sysctl.h>
72 #include <sys/sysproto.h>
73 #include <sys/systm.h>
74 #include <sys/sx.h>
75 #include <sys/time.h>
76 #include <sys/vnode.h>
77 #include <sys/unistd.h>
78
79 #include <security/mac/mac_framework.h>
80
81 #include <vm/vm.h>
82 #include <vm/vm_param.h>
83 #include <vm/pmap.h>
84 #include <vm/vm_extern.h>
85 #include <vm/vm_map.h>
86 #include <vm/vm_kern.h>
87 #include <vm/vm_object.h>
88 #include <vm/vm_page.h>
89 #include <vm/vm_pageout.h>
90 #include <vm/vm_pager.h>
91 #include <vm/swap_pager.h>
92
93 struct shm_mapping {
94 char *sm_path;
95 Fnv32_t sm_fnv;
96 struct shmfd *sm_shmfd;
97 LIST_ENTRY(shm_mapping) sm_link;
98 };
99
100 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
101 static LIST_HEAD(, shm_mapping) *shm_dictionary;
102 static struct sx shm_dict_lock;
103 static struct mtx shm_timestamp_lock;
104 static u_long shm_hash;
105 static struct unrhdr *shm_ino_unr;
106 static dev_t shm_dev_ino;
107
108 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
109
110 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
111 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
112 static void shm_init(void *arg);
113 static void shm_drop(struct shmfd *shmfd);
114 static struct shmfd *shm_hold(struct shmfd *shmfd);
115 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
116 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
117 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
118 static int shm_dotruncate(struct shmfd *shmfd, off_t length);
119
120 static fo_rdwr_t shm_read;
121 static fo_rdwr_t shm_write;
122 static fo_truncate_t shm_truncate;
123 static fo_ioctl_t shm_ioctl;
124 static fo_poll_t shm_poll;
125 static fo_kqfilter_t shm_kqfilter;
126 static fo_stat_t shm_stat;
127 static fo_close_t shm_close;
128 static fo_chmod_t shm_chmod;
129 static fo_chown_t shm_chown;
130 static fo_seek_t shm_seek;
131
132 /* File descriptor operations. */
133 static struct fileops shm_ops = {
134 .fo_read = shm_read,
135 .fo_write = shm_write,
136 .fo_truncate = shm_truncate,
137 .fo_ioctl = shm_ioctl,
138 .fo_poll = shm_poll,
139 .fo_kqfilter = shm_kqfilter,
140 .fo_stat = shm_stat,
141 .fo_close = shm_close,
142 .fo_chmod = shm_chmod,
143 .fo_chown = shm_chown,
144 .fo_sendfile = vn_sendfile,
145 .fo_seek = shm_seek,
146 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
147 };
148
149 FEATURE(posix_shm, "POSIX shared memory");
150
151 static int
152 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
153 {
154 vm_page_t m;
155 vm_pindex_t idx;
156 size_t tlen;
157 int error, offset, rv;
158
159 idx = OFF_TO_IDX(uio->uio_offset);
160 offset = uio->uio_offset & PAGE_MASK;
161 tlen = MIN(PAGE_SIZE - offset, len);
162
163 VM_OBJECT_WLOCK(obj);
164
165 /*
166 * Parallel reads of the page content from disk are prevented
167 * by exclusive busy.
168 *
169 * Although the tmpfs vnode lock is held here, it is
170 * nonetheless safe to sleep waiting for a free page. The
171 * pageout daemon does not need to acquire the tmpfs vnode
172 * lock to page out tobj's pages because tobj is a OBJT_SWAP
173 * type object.
174 */
175 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
176 if (m->valid != VM_PAGE_BITS_ALL) {
177 if (vm_pager_has_page(obj, idx, NULL, NULL)) {
178 rv = vm_pager_get_pages(obj, &m, 1, 0);
179 m = vm_page_lookup(obj, idx);
180 if (m == NULL) {
181 printf(
182 "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n",
183 obj, idx, rv);
184 VM_OBJECT_WUNLOCK(obj);
185 return (EIO);
186 }
187 if (rv != VM_PAGER_OK) {
188 printf(
189 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
190 obj, idx, m->valid, rv);
191 vm_page_lock(m);
192 vm_page_free(m);
193 vm_page_unlock(m);
194 VM_OBJECT_WUNLOCK(obj);
195 return (EIO);
196 }
197 } else
198 vm_page_zero_invalid(m, TRUE);
199 }
200 vm_page_xunbusy(m);
201 vm_page_lock(m);
202 vm_page_hold(m);
203 if (m->queue == PQ_NONE) {
204 vm_page_deactivate(m);
205 } else {
206 /* Requeue to maintain LRU ordering. */
207 vm_page_requeue(m);
208 }
209 vm_page_unlock(m);
210 VM_OBJECT_WUNLOCK(obj);
211 error = uiomove_fromphys(&m, offset, tlen, uio);
212 if (uio->uio_rw == UIO_WRITE && error == 0) {
213 VM_OBJECT_WLOCK(obj);
214 vm_page_dirty(m);
215 vm_pager_page_unswapped(m);
216 VM_OBJECT_WUNLOCK(obj);
217 }
218 vm_page_lock(m);
219 vm_page_unhold(m);
220 vm_page_unlock(m);
221
222 return (error);
223 }
224
225 int
226 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
227 {
228 ssize_t resid;
229 size_t len;
230 int error;
231
232 error = 0;
233 while ((resid = uio->uio_resid) > 0) {
234 if (obj_size <= uio->uio_offset)
235 break;
236 len = MIN(obj_size - uio->uio_offset, resid);
237 if (len == 0)
238 break;
239 error = uiomove_object_page(obj, len, uio);
240 if (error != 0 || resid == uio->uio_resid)
241 break;
242 }
243 return (error);
244 }
245
246 static int
247 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
248 {
249 struct shmfd *shmfd;
250 off_t foffset;
251 int error;
252
253 shmfd = fp->f_data;
254 foffset = foffset_lock(fp, 0);
255 error = 0;
256 switch (whence) {
257 case L_INCR:
258 if (foffset < 0 ||
259 (offset > 0 && foffset > OFF_MAX - offset)) {
260 error = EOVERFLOW;
261 break;
262 }
263 offset += foffset;
264 break;
265 case L_XTND:
266 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
267 error = EOVERFLOW;
268 break;
269 }
270 offset += shmfd->shm_size;
271 break;
272 case L_SET:
273 break;
274 default:
275 error = EINVAL;
276 }
277 if (error == 0) {
278 if (offset < 0 || offset > shmfd->shm_size)
279 error = EINVAL;
280 else
281 *(off_t *)(td->td_retval) = offset;
282 }
283 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
284 return (error);
285 }
286
287 static int
288 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
289 int flags, struct thread *td)
290 {
291 struct shmfd *shmfd;
292 void *rl_cookie;
293 int error;
294
295 shmfd = fp->f_data;
296 foffset_lock_uio(fp, uio, flags);
297 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
298 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
299 #ifdef MAC
300 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
301 if (error)
302 return (error);
303 #endif
304 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
305 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
306 foffset_unlock_uio(fp, uio, flags);
307 return (error);
308 }
309
310 static int
311 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
312 int flags, struct thread *td)
313 {
314 struct shmfd *shmfd;
315 void *rl_cookie;
316 int error;
317
318 shmfd = fp->f_data;
319 #ifdef MAC
320 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
321 if (error)
322 return (error);
323 #endif
324 foffset_lock_uio(fp, uio, flags);
325 if ((flags & FOF_OFFSET) == 0) {
326 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
327 &shmfd->shm_mtx);
328 } else {
329 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
330 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
331 }
332
333 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
334 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
335 foffset_unlock_uio(fp, uio, flags);
336 return (error);
337 }
338
339 static int
340 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
341 struct thread *td)
342 {
343 struct shmfd *shmfd;
344 #ifdef MAC
345 int error;
346 #endif
347
348 shmfd = fp->f_data;
349 #ifdef MAC
350 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
351 if (error)
352 return (error);
353 #endif
354 return (shm_dotruncate(shmfd, length));
355 }
356
357 static int
358 shm_ioctl(struct file *fp, u_long com, void *data,
359 struct ucred *active_cred, struct thread *td)
360 {
361
362 return (EOPNOTSUPP);
363 }
364
365 static int
366 shm_poll(struct file *fp, int events, struct ucred *active_cred,
367 struct thread *td)
368 {
369
370 return (EOPNOTSUPP);
371 }
372
373 static int
374 shm_kqfilter(struct file *fp, struct knote *kn)
375 {
376
377 return (EOPNOTSUPP);
378 }
379
380 static int
381 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
382 struct thread *td)
383 {
384 struct shmfd *shmfd;
385 #ifdef MAC
386 int error;
387 #endif
388
389 shmfd = fp->f_data;
390
391 #ifdef MAC
392 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
393 if (error)
394 return (error);
395 #endif
396
397 /*
398 * Attempt to return sanish values for fstat() on a memory file
399 * descriptor.
400 */
401 bzero(sb, sizeof(*sb));
402 sb->st_blksize = PAGE_SIZE;
403 sb->st_size = shmfd->shm_size;
404 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
405 mtx_lock(&shm_timestamp_lock);
406 sb->st_atim = shmfd->shm_atime;
407 sb->st_ctim = shmfd->shm_ctime;
408 sb->st_mtim = shmfd->shm_mtime;
409 sb->st_birthtim = shmfd->shm_birthtime;
410 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
411 sb->st_uid = shmfd->shm_uid;
412 sb->st_gid = shmfd->shm_gid;
413 mtx_unlock(&shm_timestamp_lock);
414 sb->st_dev = shm_dev_ino;
415 sb->st_ino = shmfd->shm_ino;
416
417 return (0);
418 }
419
420 static int
421 shm_close(struct file *fp, struct thread *td)
422 {
423 struct shmfd *shmfd;
424
425 shmfd = fp->f_data;
426 fp->f_data = NULL;
427 shm_drop(shmfd);
428
429 return (0);
430 }
431
432 static int
433 shm_dotruncate(struct shmfd *shmfd, off_t length)
434 {
435 vm_object_t object;
436 vm_page_t m, ma[1];
437 vm_pindex_t idx, nobjsize;
438 vm_ooffset_t delta;
439 int base, rv;
440
441 object = shmfd->shm_object;
442 VM_OBJECT_WLOCK(object);
443 if (length == shmfd->shm_size) {
444 VM_OBJECT_WUNLOCK(object);
445 return (0);
446 }
447 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
448
449 /* Are we shrinking? If so, trim the end. */
450 if (length < shmfd->shm_size) {
451 /*
452 * Disallow any requests to shrink the size if this
453 * object is mapped into the kernel.
454 */
455 if (shmfd->shm_kmappings > 0) {
456 VM_OBJECT_WUNLOCK(object);
457 return (EBUSY);
458 }
459
460 /*
461 * Zero the truncated part of the last page.
462 */
463 base = length & PAGE_MASK;
464 if (base != 0) {
465 idx = OFF_TO_IDX(length);
466 retry:
467 m = vm_page_lookup(object, idx);
468 if (m != NULL) {
469 if (vm_page_sleep_if_busy(m, "shmtrc"))
470 goto retry;
471 } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
472 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
473 if (m == NULL) {
474 VM_OBJECT_WUNLOCK(object);
475 VM_WAIT;
476 VM_OBJECT_WLOCK(object);
477 goto retry;
478 } else if (m->valid != VM_PAGE_BITS_ALL) {
479 ma[0] = m;
480 rv = vm_pager_get_pages(object, ma, 1,
481 0);
482 m = vm_page_lookup(object, idx);
483 } else
484 /* A cached page was reactivated. */
485 rv = VM_PAGER_OK;
486 vm_page_lock(m);
487 if (rv == VM_PAGER_OK) {
488 vm_page_deactivate(m);
489 vm_page_unlock(m);
490 vm_page_xunbusy(m);
491 } else {
492 vm_page_free(m);
493 vm_page_unlock(m);
494 VM_OBJECT_WUNLOCK(object);
495 return (EIO);
496 }
497 }
498 if (m != NULL) {
499 pmap_zero_page_area(m, base, PAGE_SIZE - base);
500 KASSERT(m->valid == VM_PAGE_BITS_ALL,
501 ("shm_dotruncate: page %p is invalid", m));
502 vm_page_dirty(m);
503 vm_pager_page_unswapped(m);
504 }
505 }
506 delta = ptoa(object->size - nobjsize);
507
508 /* Toss in memory pages. */
509 if (nobjsize < object->size)
510 vm_object_page_remove(object, nobjsize, object->size,
511 0);
512
513 /* Toss pages from swap. */
514 if (object->type == OBJT_SWAP)
515 swap_pager_freespace(object, nobjsize, delta);
516
517 /* Free the swap accounted for shm */
518 swap_release_by_cred(delta, object->cred);
519 object->charge -= delta;
520 } else {
521 /* Attempt to reserve the swap */
522 delta = ptoa(nobjsize - object->size);
523 if (!swap_reserve_by_cred(delta, object->cred)) {
524 VM_OBJECT_WUNLOCK(object);
525 return (ENOMEM);
526 }
527 object->charge += delta;
528 }
529 shmfd->shm_size = length;
530 mtx_lock(&shm_timestamp_lock);
531 vfs_timestamp(&shmfd->shm_ctime);
532 shmfd->shm_mtime = shmfd->shm_ctime;
533 mtx_unlock(&shm_timestamp_lock);
534 object->size = nobjsize;
535 VM_OBJECT_WUNLOCK(object);
536 return (0);
537 }
538
539 /*
540 * shmfd object management including creation and reference counting
541 * routines.
542 */
543 static struct shmfd *
544 shm_alloc(struct ucred *ucred, mode_t mode)
545 {
546 struct shmfd *shmfd;
547 int ino;
548
549 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
550 shmfd->shm_size = 0;
551 shmfd->shm_uid = ucred->cr_uid;
552 shmfd->shm_gid = ucred->cr_gid;
553 shmfd->shm_mode = mode;
554 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
555 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
556 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
557 shmfd->shm_object->pg_color = 0;
558 VM_OBJECT_WLOCK(shmfd->shm_object);
559 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
560 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
561 VM_OBJECT_WUNLOCK(shmfd->shm_object);
562 vfs_timestamp(&shmfd->shm_birthtime);
563 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
564 shmfd->shm_birthtime;
565 ino = alloc_unr(shm_ino_unr);
566 if (ino == -1)
567 shmfd->shm_ino = 0;
568 else
569 shmfd->shm_ino = ino;
570 refcount_init(&shmfd->shm_refs, 1);
571 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
572 rangelock_init(&shmfd->shm_rl);
573 #ifdef MAC
574 mac_posixshm_init(shmfd);
575 mac_posixshm_create(ucred, shmfd);
576 #endif
577
578 return (shmfd);
579 }
580
581 static struct shmfd *
582 shm_hold(struct shmfd *shmfd)
583 {
584
585 refcount_acquire(&shmfd->shm_refs);
586 return (shmfd);
587 }
588
589 static void
590 shm_drop(struct shmfd *shmfd)
591 {
592
593 if (refcount_release(&shmfd->shm_refs)) {
594 #ifdef MAC
595 mac_posixshm_destroy(shmfd);
596 #endif
597 rangelock_destroy(&shmfd->shm_rl);
598 mtx_destroy(&shmfd->shm_mtx);
599 vm_object_deallocate(shmfd->shm_object);
600 if (shmfd->shm_ino != 0)
601 free_unr(shm_ino_unr, shmfd->shm_ino);
602 free(shmfd, M_SHMFD);
603 }
604 }
605
606 /*
607 * Determine if the credentials have sufficient permissions for a
608 * specified combination of FREAD and FWRITE.
609 */
610 static int
611 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
612 {
613 accmode_t accmode;
614 int error;
615
616 accmode = 0;
617 if (flags & FREAD)
618 accmode |= VREAD;
619 if (flags & FWRITE)
620 accmode |= VWRITE;
621 mtx_lock(&shm_timestamp_lock);
622 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
623 accmode, ucred, NULL);
624 mtx_unlock(&shm_timestamp_lock);
625 return (error);
626 }
627
628 /*
629 * Dictionary management. We maintain an in-kernel dictionary to map
630 * paths to shmfd objects. We use the FNV hash on the path to store
631 * the mappings in a hash table.
632 */
633 static void
634 shm_init(void *arg)
635 {
636
637 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
638 sx_init(&shm_dict_lock, "shm dictionary");
639 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
640 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL);
641 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized"));
642 shm_dev_ino = devfs_alloc_cdp_inode();
643 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
644 }
645 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
646
647 static struct shmfd *
648 shm_lookup(char *path, Fnv32_t fnv)
649 {
650 struct shm_mapping *map;
651
652 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
653 if (map->sm_fnv != fnv)
654 continue;
655 if (strcmp(map->sm_path, path) == 0)
656 return (map->sm_shmfd);
657 }
658
659 return (NULL);
660 }
661
662 static void
663 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
664 {
665 struct shm_mapping *map;
666
667 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
668 map->sm_path = path;
669 map->sm_fnv = fnv;
670 map->sm_shmfd = shm_hold(shmfd);
671 shmfd->shm_path = path;
672 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
673 }
674
675 static int
676 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
677 {
678 struct shm_mapping *map;
679 int error;
680
681 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
682 if (map->sm_fnv != fnv)
683 continue;
684 if (strcmp(map->sm_path, path) == 0) {
685 #ifdef MAC
686 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
687 if (error)
688 return (error);
689 #endif
690 error = shm_access(map->sm_shmfd, ucred,
691 FREAD | FWRITE);
692 if (error)
693 return (error);
694 map->sm_shmfd->shm_path = NULL;
695 LIST_REMOVE(map, sm_link);
696 shm_drop(map->sm_shmfd);
697 free(map->sm_path, M_SHMFD);
698 free(map, M_SHMFD);
699 return (0);
700 }
701 }
702
703 return (ENOENT);
704 }
705
706 /* System calls. */
707 int
708 sys_shm_open(struct thread *td, struct shm_open_args *uap)
709 {
710 struct filedesc *fdp;
711 struct shmfd *shmfd;
712 struct file *fp;
713 char *path;
714 Fnv32_t fnv;
715 mode_t cmode;
716 int fd, error;
717
718 #ifdef CAPABILITY_MODE
719 /*
720 * shm_open(2) is only allowed for anonymous objects.
721 */
722 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON))
723 return (ECAPMODE);
724 #endif
725
726 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
727 (uap->flags & O_ACCMODE) != O_RDWR)
728 return (EINVAL);
729
730 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
731 return (EINVAL);
732
733 fdp = td->td_proc->p_fd;
734 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
735
736 error = falloc(td, &fp, &fd, O_CLOEXEC);
737 if (error)
738 return (error);
739
740 /* A SHM_ANON path pointer creates an anonymous object. */
741 if (uap->path == SHM_ANON) {
742 /* A read-only anonymous object is pointless. */
743 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
744 fdclose(fdp, fp, fd, td);
745 fdrop(fp, td);
746 return (EINVAL);
747 }
748 shmfd = shm_alloc(td->td_ucred, cmode);
749 } else {
750 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
751 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
752 #ifdef KTRACE
753 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
754 ktrnamei(path);
755 #endif
756 /* Require paths to start with a '/' character. */
757 if (error == 0 && path[0] != '/')
758 error = EINVAL;
759 if (error) {
760 fdclose(fdp, fp, fd, td);
761 fdrop(fp, td);
762 free(path, M_SHMFD);
763 return (error);
764 }
765
766 fnv = fnv_32_str(path, FNV1_32_INIT);
767 sx_xlock(&shm_dict_lock);
768 shmfd = shm_lookup(path, fnv);
769 if (shmfd == NULL) {
770 /* Object does not yet exist, create it if requested. */
771 if (uap->flags & O_CREAT) {
772 #ifdef MAC
773 error = mac_posixshm_check_create(td->td_ucred,
774 path);
775 if (error == 0) {
776 #endif
777 shmfd = shm_alloc(td->td_ucred, cmode);
778 shm_insert(path, fnv, shmfd);
779 #ifdef MAC
780 }
781 #endif
782 } else {
783 free(path, M_SHMFD);
784 error = ENOENT;
785 }
786 } else {
787 /*
788 * Object already exists, obtain a new
789 * reference if requested and permitted.
790 */
791 free(path, M_SHMFD);
792 if ((uap->flags & (O_CREAT | O_EXCL)) ==
793 (O_CREAT | O_EXCL))
794 error = EEXIST;
795 else {
796 #ifdef MAC
797 error = mac_posixshm_check_open(td->td_ucred,
798 shmfd, FFLAGS(uap->flags & O_ACCMODE));
799 if (error == 0)
800 #endif
801 error = shm_access(shmfd, td->td_ucred,
802 FFLAGS(uap->flags & O_ACCMODE));
803 }
804
805 /*
806 * Truncate the file back to zero length if
807 * O_TRUNC was specified and the object was
808 * opened with read/write.
809 */
810 if (error == 0 &&
811 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
812 (O_RDWR | O_TRUNC)) {
813 #ifdef MAC
814 error = mac_posixshm_check_truncate(
815 td->td_ucred, fp->f_cred, shmfd);
816 if (error == 0)
817 #endif
818 shm_dotruncate(shmfd, 0);
819 }
820 if (error == 0)
821 shm_hold(shmfd);
822 }
823 sx_xunlock(&shm_dict_lock);
824
825 if (error) {
826 fdclose(fdp, fp, fd, td);
827 fdrop(fp, td);
828 return (error);
829 }
830 }
831
832 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
833
834 td->td_retval[0] = fd;
835 fdrop(fp, td);
836
837 return (0);
838 }
839
840 int
841 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
842 {
843 char *path;
844 Fnv32_t fnv;
845 int error;
846
847 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
848 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
849 if (error) {
850 free(path, M_TEMP);
851 return (error);
852 }
853 #ifdef KTRACE
854 if (KTRPOINT(curthread, KTR_NAMEI))
855 ktrnamei(path);
856 #endif
857 fnv = fnv_32_str(path, FNV1_32_INIT);
858 sx_xlock(&shm_dict_lock);
859 error = shm_remove(path, fnv, td->td_ucred);
860 sx_xunlock(&shm_dict_lock);
861 free(path, M_TEMP);
862
863 return (error);
864 }
865
866 /*
867 * mmap() helper to validate mmap() requests against shm object state
868 * and give mmap() the vm_object to use for the mapping.
869 */
870 int
871 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
872 vm_object_t *obj)
873 {
874
875 /*
876 * XXXRW: This validation is probably insufficient, and subject to
877 * sign errors. It should be fixed.
878 */
879 if (foff >= shmfd->shm_size ||
880 foff + objsize > round_page(shmfd->shm_size))
881 return (EINVAL);
882
883 mtx_lock(&shm_timestamp_lock);
884 vfs_timestamp(&shmfd->shm_atime);
885 mtx_unlock(&shm_timestamp_lock);
886 vm_object_reference(shmfd->shm_object);
887 *obj = shmfd->shm_object;
888 return (0);
889 }
890
891 static int
892 shm_chmod(struct file *fp, mode_t mode, 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 /*
902 * SUSv4 says that x bits of permission need not be affected.
903 * Be consistent with our shm_open there.
904 */
905 #ifdef MAC
906 error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
907 if (error != 0)
908 goto out;
909 #endif
910 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
911 shmfd->shm_gid, VADMIN, active_cred, NULL);
912 if (error != 0)
913 goto out;
914 shmfd->shm_mode = mode & ACCESSPERMS;
915 out:
916 mtx_unlock(&shm_timestamp_lock);
917 return (error);
918 }
919
920 static int
921 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
922 struct thread *td)
923 {
924 struct shmfd *shmfd;
925 int error;
926
927 error = 0;
928 shmfd = fp->f_data;
929 mtx_lock(&shm_timestamp_lock);
930 #ifdef MAC
931 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
932 if (error != 0)
933 goto out;
934 #endif
935 if (uid == (uid_t)-1)
936 uid = shmfd->shm_uid;
937 if (gid == (gid_t)-1)
938 gid = shmfd->shm_gid;
939 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
940 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
941 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
942 goto out;
943 shmfd->shm_uid = uid;
944 shmfd->shm_gid = gid;
945 out:
946 mtx_unlock(&shm_timestamp_lock);
947 return (error);
948 }
949
950 /*
951 * Helper routines to allow the backing object of a shared memory file
952 * descriptor to be mapped in the kernel.
953 */
954 int
955 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
956 {
957 struct shmfd *shmfd;
958 vm_offset_t kva, ofs;
959 vm_object_t obj;
960 int rv;
961
962 if (fp->f_type != DTYPE_SHM)
963 return (EINVAL);
964 shmfd = fp->f_data;
965 obj = shmfd->shm_object;
966 VM_OBJECT_WLOCK(obj);
967 /*
968 * XXXRW: This validation is probably insufficient, and subject to
969 * sign errors. It should be fixed.
970 */
971 if (offset >= shmfd->shm_size ||
972 offset + size > round_page(shmfd->shm_size)) {
973 VM_OBJECT_WUNLOCK(obj);
974 return (EINVAL);
975 }
976
977 shmfd->shm_kmappings++;
978 vm_object_reference_locked(obj);
979 VM_OBJECT_WUNLOCK(obj);
980
981 /* Map the object into the kernel_map and wire it. */
982 kva = vm_map_min(kernel_map);
983 ofs = offset & PAGE_MASK;
984 offset = trunc_page(offset);
985 size = round_page(size + ofs);
986 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
987 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
988 VM_PROT_READ | VM_PROT_WRITE, 0);
989 if (rv == KERN_SUCCESS) {
990 rv = vm_map_wire(kernel_map, kva, kva + size,
991 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
992 if (rv == KERN_SUCCESS) {
993 *memp = (void *)(kva + ofs);
994 return (0);
995 }
996 vm_map_remove(kernel_map, kva, kva + size);
997 } else
998 vm_object_deallocate(obj);
999
1000 /* On failure, drop our mapping reference. */
1001 VM_OBJECT_WLOCK(obj);
1002 shmfd->shm_kmappings--;
1003 VM_OBJECT_WUNLOCK(obj);
1004
1005 return (vm_mmap_to_errno(rv));
1006 }
1007
1008 /*
1009 * We require the caller to unmap the entire entry. This allows us to
1010 * safely decrement shm_kmappings when a mapping is removed.
1011 */
1012 int
1013 shm_unmap(struct file *fp, void *mem, size_t size)
1014 {
1015 struct shmfd *shmfd;
1016 vm_map_entry_t entry;
1017 vm_offset_t kva, ofs;
1018 vm_object_t obj;
1019 vm_pindex_t pindex;
1020 vm_prot_t prot;
1021 boolean_t wired;
1022 vm_map_t map;
1023 int rv;
1024
1025 if (fp->f_type != DTYPE_SHM)
1026 return (EINVAL);
1027 shmfd = fp->f_data;
1028 kva = (vm_offset_t)mem;
1029 ofs = kva & PAGE_MASK;
1030 kva = trunc_page(kva);
1031 size = round_page(size + ofs);
1032 map = kernel_map;
1033 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1034 &obj, &pindex, &prot, &wired);
1035 if (rv != KERN_SUCCESS)
1036 return (EINVAL);
1037 if (entry->start != kva || entry->end != kva + size) {
1038 vm_map_lookup_done(map, entry);
1039 return (EINVAL);
1040 }
1041 vm_map_lookup_done(map, entry);
1042 if (obj != shmfd->shm_object)
1043 return (EINVAL);
1044 vm_map_remove(map, kva, kva + size);
1045 VM_OBJECT_WLOCK(obj);
1046 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1047 shmfd->shm_kmappings--;
1048 VM_OBJECT_WUNLOCK(obj);
1049 return (0);
1050 }
1051
1052 void
1053 shm_path(struct shmfd *shmfd, char *path, size_t size)
1054 {
1055
1056 if (shmfd->shm_path == NULL)
1057 return;
1058 sx_slock(&shm_dict_lock);
1059 if (shmfd->shm_path != NULL)
1060 strlcpy(path, shmfd->shm_path, size);
1061 sx_sunlock(&shm_dict_lock);
1062 }
Cache object: c953bf358b8a949c69f7e4c418b3b489
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