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("$FreeBSD$");
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/jail.h>
61 #include <sys/ktrace.h>
62 #include <sys/lock.h>
63 #include <sys/malloc.h>
64 #include <sys/mman.h>
65 #include <sys/mutex.h>
66 #include <sys/priv.h>
67 #include <sys/proc.h>
68 #include <sys/refcount.h>
69 #include <sys/resourcevar.h>
70 #include <sys/rwlock.h>
71 #include <sys/stat.h>
72 #include <sys/sysctl.h>
73 #include <sys/sysproto.h>
74 #include <sys/systm.h>
75 #include <sys/sx.h>
76 #include <sys/time.h>
77 #include <sys/vnode.h>
78 #include <sys/unistd.h>
79
80 #include <security/mac/mac_framework.h>
81
82 #include <vm/vm.h>
83 #include <vm/vm_param.h>
84 #include <vm/pmap.h>
85 #include <vm/vm_extern.h>
86 #include <vm/vm_map.h>
87 #include <vm/vm_kern.h>
88 #include <vm/vm_object.h>
89 #include <vm/vm_page.h>
90 #include <vm/vm_pageout.h>
91 #include <vm/vm_pager.h>
92 #include <vm/swap_pager.h>
93
94 struct shm_mapping {
95 char *sm_path;
96 Fnv32_t sm_fnv;
97 struct shmfd *sm_shmfd;
98 LIST_ENTRY(shm_mapping) sm_link;
99 };
100
101 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
102 static LIST_HEAD(, shm_mapping) *shm_dictionary;
103 static struct sx shm_dict_lock;
104 static struct mtx shm_timestamp_lock;
105 static u_long shm_hash;
106 static struct unrhdr *shm_ino_unr;
107 static dev_t shm_dev_ino;
108
109 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
110
111 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
112 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
113 static void shm_init(void *arg);
114 static void shm_drop(struct shmfd *shmfd);
115 static struct shmfd *shm_hold(struct shmfd *shmfd);
116 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
117 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
118 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
119 static int shm_dotruncate(struct shmfd *shmfd, off_t length);
120
121 static fo_rdwr_t shm_read;
122 static fo_rdwr_t shm_write;
123 static fo_truncate_t shm_truncate;
124 static fo_ioctl_t shm_ioctl;
125 static fo_poll_t shm_poll;
126 static fo_kqfilter_t shm_kqfilter;
127 static fo_stat_t shm_stat;
128 static fo_close_t shm_close;
129 static fo_chmod_t shm_chmod;
130 static fo_chown_t shm_chown;
131 static fo_seek_t shm_seek;
132
133 /* File descriptor operations. */
134 static struct fileops shm_ops = {
135 .fo_read = shm_read,
136 .fo_write = shm_write,
137 .fo_truncate = shm_truncate,
138 .fo_ioctl = shm_ioctl,
139 .fo_poll = shm_poll,
140 .fo_kqfilter = shm_kqfilter,
141 .fo_stat = shm_stat,
142 .fo_close = shm_close,
143 .fo_chmod = shm_chmod,
144 .fo_chown = shm_chown,
145 .fo_sendfile = vn_sendfile,
146 .fo_seek = shm_seek,
147 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
148 };
149
150 FEATURE(posix_shm, "POSIX shared memory");
151
152 static int
153 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
154 {
155 vm_page_t m;
156 vm_pindex_t idx;
157 size_t tlen;
158 int error, offset, rv;
159
160 idx = OFF_TO_IDX(uio->uio_offset);
161 offset = uio->uio_offset & PAGE_MASK;
162 tlen = MIN(PAGE_SIZE - offset, len);
163
164 VM_OBJECT_WLOCK(obj);
165
166 /*
167 * Parallel reads of the page content from disk are prevented
168 * by exclusive busy.
169 *
170 * Although the tmpfs vnode lock is held here, it is
171 * nonetheless safe to sleep waiting for a free page. The
172 * pageout daemon does not need to acquire the tmpfs vnode
173 * lock to page out tobj's pages because tobj is a OBJT_SWAP
174 * type object.
175 */
176 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
177 if (m->valid != VM_PAGE_BITS_ALL) {
178 if (vm_pager_has_page(obj, idx, NULL, NULL)) {
179 rv = vm_pager_get_pages(obj, &m, 1, 0);
180 m = vm_page_lookup(obj, idx);
181 if (m == NULL) {
182 printf(
183 "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n",
184 obj, idx, rv);
185 VM_OBJECT_WUNLOCK(obj);
186 return (EIO);
187 }
188 if (rv != VM_PAGER_OK) {
189 printf(
190 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
191 obj, idx, m->valid, rv);
192 vm_page_lock(m);
193 vm_page_free(m);
194 vm_page_unlock(m);
195 VM_OBJECT_WUNLOCK(obj);
196 return (EIO);
197 }
198 } else
199 vm_page_zero_invalid(m, TRUE);
200 }
201 vm_page_xunbusy(m);
202 vm_page_lock(m);
203 vm_page_hold(m);
204 if (m->queue == PQ_NONE) {
205 vm_page_deactivate(m);
206 } else {
207 /* Requeue to maintain LRU ordering. */
208 vm_page_requeue(m);
209 }
210 vm_page_unlock(m);
211 VM_OBJECT_WUNLOCK(obj);
212 error = uiomove_fromphys(&m, offset, tlen, uio);
213 if (uio->uio_rw == UIO_WRITE && error == 0) {
214 VM_OBJECT_WLOCK(obj);
215 vm_page_dirty(m);
216 vm_pager_page_unswapped(m);
217 VM_OBJECT_WUNLOCK(obj);
218 }
219 vm_page_lock(m);
220 vm_page_unhold(m);
221 vm_page_unlock(m);
222
223 return (error);
224 }
225
226 int
227 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
228 {
229 ssize_t resid;
230 size_t len;
231 int error;
232
233 error = 0;
234 while ((resid = uio->uio_resid) > 0) {
235 if (obj_size <= uio->uio_offset)
236 break;
237 len = MIN(obj_size - uio->uio_offset, resid);
238 if (len == 0)
239 break;
240 error = uiomove_object_page(obj, len, uio);
241 if (error != 0 || resid == uio->uio_resid)
242 break;
243 }
244 return (error);
245 }
246
247 static int
248 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
249 {
250 struct shmfd *shmfd;
251 off_t foffset;
252 int error;
253
254 shmfd = fp->f_data;
255 foffset = foffset_lock(fp, 0);
256 error = 0;
257 switch (whence) {
258 case L_INCR:
259 if (foffset < 0 ||
260 (offset > 0 && foffset > OFF_MAX - offset)) {
261 error = EOVERFLOW;
262 break;
263 }
264 offset += foffset;
265 break;
266 case L_XTND:
267 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
268 error = EOVERFLOW;
269 break;
270 }
271 offset += shmfd->shm_size;
272 break;
273 case L_SET:
274 break;
275 default:
276 error = EINVAL;
277 }
278 if (error == 0) {
279 if (offset < 0 || offset > shmfd->shm_size)
280 error = EINVAL;
281 else
282 *(off_t *)(td->td_retval) = offset;
283 }
284 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
285 return (error);
286 }
287
288 static int
289 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
290 int flags, struct thread *td)
291 {
292 struct shmfd *shmfd;
293 void *rl_cookie;
294 int error;
295
296 shmfd = fp->f_data;
297 #ifdef MAC
298 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
299 if (error)
300 return (error);
301 #endif
302 foffset_lock_uio(fp, uio, flags);
303 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
304 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
305 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
306 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
307 foffset_unlock_uio(fp, uio, flags);
308 return (error);
309 }
310
311 static int
312 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
313 int flags, struct thread *td)
314 {
315 struct shmfd *shmfd;
316 void *rl_cookie;
317 int error;
318
319 shmfd = fp->f_data;
320 #ifdef MAC
321 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
322 if (error)
323 return (error);
324 #endif
325 foffset_lock_uio(fp, uio, flags);
326 if ((flags & FOF_OFFSET) == 0) {
327 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
328 &shmfd->shm_mtx);
329 } else {
330 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
331 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
332 }
333
334 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
335 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
336 foffset_unlock_uio(fp, uio, flags);
337 return (error);
338 }
339
340 static int
341 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
342 struct thread *td)
343 {
344 struct shmfd *shmfd;
345 #ifdef MAC
346 int error;
347 #endif
348
349 shmfd = fp->f_data;
350 #ifdef MAC
351 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
352 if (error)
353 return (error);
354 #endif
355 return (shm_dotruncate(shmfd, length));
356 }
357
358 static int
359 shm_ioctl(struct file *fp, u_long com, void *data,
360 struct ucred *active_cred, struct thread *td)
361 {
362
363 return (EOPNOTSUPP);
364 }
365
366 static int
367 shm_poll(struct file *fp, int events, struct ucred *active_cred,
368 struct thread *td)
369 {
370
371 return (EOPNOTSUPP);
372 }
373
374 static int
375 shm_kqfilter(struct file *fp, struct knote *kn)
376 {
377
378 return (EOPNOTSUPP);
379 }
380
381 static int
382 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
383 struct thread *td)
384 {
385 struct shmfd *shmfd;
386 #ifdef MAC
387 int error;
388 #endif
389
390 shmfd = fp->f_data;
391
392 #ifdef MAC
393 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
394 if (error)
395 return (error);
396 #endif
397
398 /*
399 * Attempt to return sanish values for fstat() on a memory file
400 * descriptor.
401 */
402 bzero(sb, sizeof(*sb));
403 sb->st_blksize = PAGE_SIZE;
404 sb->st_size = shmfd->shm_size;
405 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
406 mtx_lock(&shm_timestamp_lock);
407 sb->st_atim = shmfd->shm_atime;
408 sb->st_ctim = shmfd->shm_ctime;
409 sb->st_mtim = shmfd->shm_mtime;
410 sb->st_birthtim = shmfd->shm_birthtime;
411 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
412 sb->st_uid = shmfd->shm_uid;
413 sb->st_gid = shmfd->shm_gid;
414 mtx_unlock(&shm_timestamp_lock);
415 sb->st_dev = shm_dev_ino;
416 sb->st_ino = shmfd->shm_ino;
417
418 return (0);
419 }
420
421 static int
422 shm_close(struct file *fp, struct thread *td)
423 {
424 struct shmfd *shmfd;
425
426 shmfd = fp->f_data;
427 fp->f_data = NULL;
428 shm_drop(shmfd);
429
430 return (0);
431 }
432
433 static int
434 shm_dotruncate(struct shmfd *shmfd, off_t length)
435 {
436 vm_object_t object;
437 vm_page_t m, ma[1];
438 vm_pindex_t idx, nobjsize;
439 vm_ooffset_t delta;
440 int base, rv;
441
442 KASSERT(length >= 0, ("shm_dotruncate: length < 0"));
443 object = shmfd->shm_object;
444 VM_OBJECT_WLOCK(object);
445 if (length == shmfd->shm_size) {
446 VM_OBJECT_WUNLOCK(object);
447 return (0);
448 }
449 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
450
451 /* Are we shrinking? If so, trim the end. */
452 if (length < shmfd->shm_size) {
453 /*
454 * Disallow any requests to shrink the size if this
455 * object is mapped into the kernel.
456 */
457 if (shmfd->shm_kmappings > 0) {
458 VM_OBJECT_WUNLOCK(object);
459 return (EBUSY);
460 }
461
462 /*
463 * Zero the truncated part of the last page.
464 */
465 base = length & PAGE_MASK;
466 if (base != 0) {
467 idx = OFF_TO_IDX(length);
468 retry:
469 m = vm_page_lookup(object, idx);
470 if (m != NULL) {
471 if (vm_page_sleep_if_busy(m, "shmtrc"))
472 goto retry;
473 } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
474 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
475 if (m == NULL) {
476 VM_OBJECT_WUNLOCK(object);
477 VM_WAIT;
478 VM_OBJECT_WLOCK(object);
479 goto retry;
480 } else if (m->valid != VM_PAGE_BITS_ALL) {
481 ma[0] = m;
482 rv = vm_pager_get_pages(object, ma, 1,
483 0);
484 m = vm_page_lookup(object, idx);
485 } else
486 /* A cached page was reactivated. */
487 rv = VM_PAGER_OK;
488 vm_page_lock(m);
489 if (rv == VM_PAGER_OK) {
490 vm_page_deactivate(m);
491 vm_page_unlock(m);
492 vm_page_xunbusy(m);
493 } else {
494 vm_page_free(m);
495 vm_page_unlock(m);
496 VM_OBJECT_WUNLOCK(object);
497 return (EIO);
498 }
499 }
500 if (m != NULL) {
501 pmap_zero_page_area(m, base, PAGE_SIZE - base);
502 KASSERT(m->valid == VM_PAGE_BITS_ALL,
503 ("shm_dotruncate: page %p is invalid", m));
504 vm_page_dirty(m);
505 vm_pager_page_unswapped(m);
506 }
507 }
508 delta = IDX_TO_OFF(object->size - nobjsize);
509
510 /* Toss in memory pages. */
511 if (nobjsize < object->size)
512 vm_object_page_remove(object, nobjsize, object->size,
513 0);
514
515 /* Toss pages from swap. */
516 if (object->type == OBJT_SWAP)
517 swap_pager_freespace(object, nobjsize, delta);
518
519 /* Free the swap accounted for shm */
520 swap_release_by_cred(delta, object->cred);
521 object->charge -= delta;
522 } else {
523 /* Try to reserve additional swap space. */
524 delta = IDX_TO_OFF(nobjsize - object->size);
525 if (!swap_reserve_by_cred(delta, object->cred)) {
526 VM_OBJECT_WUNLOCK(object);
527 return (ENOMEM);
528 }
529 object->charge += delta;
530 }
531 shmfd->shm_size = length;
532 mtx_lock(&shm_timestamp_lock);
533 vfs_timestamp(&shmfd->shm_ctime);
534 shmfd->shm_mtime = shmfd->shm_ctime;
535 mtx_unlock(&shm_timestamp_lock);
536 object->size = nobjsize;
537 VM_OBJECT_WUNLOCK(object);
538 return (0);
539 }
540
541 /*
542 * shmfd object management including creation and reference counting
543 * routines.
544 */
545 static struct shmfd *
546 shm_alloc(struct ucred *ucred, mode_t mode)
547 {
548 struct shmfd *shmfd;
549 int ino;
550
551 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
552 shmfd->shm_size = 0;
553 shmfd->shm_uid = ucred->cr_uid;
554 shmfd->shm_gid = ucred->cr_gid;
555 shmfd->shm_mode = mode;
556 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
557 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
558 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
559 shmfd->shm_object->pg_color = 0;
560 VM_OBJECT_WLOCK(shmfd->shm_object);
561 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
562 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
563 VM_OBJECT_WUNLOCK(shmfd->shm_object);
564 vfs_timestamp(&shmfd->shm_birthtime);
565 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
566 shmfd->shm_birthtime;
567 ino = alloc_unr(shm_ino_unr);
568 if (ino == -1)
569 shmfd->shm_ino = 0;
570 else
571 shmfd->shm_ino = ino;
572 refcount_init(&shmfd->shm_refs, 1);
573 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
574 rangelock_init(&shmfd->shm_rl);
575 #ifdef MAC
576 mac_posixshm_init(shmfd);
577 mac_posixshm_create(ucred, shmfd);
578 #endif
579
580 return (shmfd);
581 }
582
583 static struct shmfd *
584 shm_hold(struct shmfd *shmfd)
585 {
586
587 refcount_acquire(&shmfd->shm_refs);
588 return (shmfd);
589 }
590
591 static void
592 shm_drop(struct shmfd *shmfd)
593 {
594
595 if (refcount_release(&shmfd->shm_refs)) {
596 #ifdef MAC
597 mac_posixshm_destroy(shmfd);
598 #endif
599 rangelock_destroy(&shmfd->shm_rl);
600 mtx_destroy(&shmfd->shm_mtx);
601 vm_object_deallocate(shmfd->shm_object);
602 if (shmfd->shm_ino != 0)
603 free_unr(shm_ino_unr, shmfd->shm_ino);
604 free(shmfd, M_SHMFD);
605 }
606 }
607
608 /*
609 * Determine if the credentials have sufficient permissions for a
610 * specified combination of FREAD and FWRITE.
611 */
612 static int
613 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
614 {
615 accmode_t accmode;
616 int error;
617
618 accmode = 0;
619 if (flags & FREAD)
620 accmode |= VREAD;
621 if (flags & FWRITE)
622 accmode |= VWRITE;
623 mtx_lock(&shm_timestamp_lock);
624 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
625 accmode, ucred, NULL);
626 mtx_unlock(&shm_timestamp_lock);
627 return (error);
628 }
629
630 /*
631 * Dictionary management. We maintain an in-kernel dictionary to map
632 * paths to shmfd objects. We use the FNV hash on the path to store
633 * the mappings in a hash table.
634 */
635 static void
636 shm_init(void *arg)
637 {
638
639 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
640 sx_init(&shm_dict_lock, "shm dictionary");
641 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
642 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL);
643 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized"));
644 shm_dev_ino = devfs_alloc_cdp_inode();
645 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
646 }
647 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
648
649 static struct shmfd *
650 shm_lookup(char *path, Fnv32_t fnv)
651 {
652 struct shm_mapping *map;
653
654 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
655 if (map->sm_fnv != fnv)
656 continue;
657 if (strcmp(map->sm_path, path) == 0)
658 return (map->sm_shmfd);
659 }
660
661 return (NULL);
662 }
663
664 static void
665 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
666 {
667 struct shm_mapping *map;
668
669 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
670 map->sm_path = path;
671 map->sm_fnv = fnv;
672 map->sm_shmfd = shm_hold(shmfd);
673 shmfd->shm_path = path;
674 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
675 }
676
677 static int
678 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
679 {
680 struct shm_mapping *map;
681 int error;
682
683 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
684 if (map->sm_fnv != fnv)
685 continue;
686 if (strcmp(map->sm_path, path) == 0) {
687 #ifdef MAC
688 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
689 if (error)
690 return (error);
691 #endif
692 error = shm_access(map->sm_shmfd, ucred,
693 FREAD | FWRITE);
694 if (error)
695 return (error);
696 map->sm_shmfd->shm_path = NULL;
697 LIST_REMOVE(map, sm_link);
698 shm_drop(map->sm_shmfd);
699 free(map->sm_path, M_SHMFD);
700 free(map, M_SHMFD);
701 return (0);
702 }
703 }
704
705 return (ENOENT);
706 }
707
708 /* System calls. */
709 int
710 sys_shm_open(struct thread *td, struct shm_open_args *uap)
711 {
712 struct filedesc *fdp;
713 struct shmfd *shmfd;
714 struct file *fp;
715 char *path;
716 const char *pr_path;
717 size_t pr_pathlen;
718 Fnv32_t fnv;
719 mode_t cmode;
720 int fd, error;
721
722 #ifdef CAPABILITY_MODE
723 /*
724 * shm_open(2) is only allowed for anonymous objects.
725 */
726 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON))
727 return (ECAPMODE);
728 #endif
729
730 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
731 (uap->flags & O_ACCMODE) != O_RDWR)
732 return (EINVAL);
733
734 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
735 return (EINVAL);
736
737 fdp = td->td_proc->p_fd;
738 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
739
740 error = falloc(td, &fp, &fd, O_CLOEXEC);
741 if (error)
742 return (error);
743
744 /* A SHM_ANON path pointer creates an anonymous object. */
745 if (uap->path == SHM_ANON) {
746 /* A read-only anonymous object is pointless. */
747 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
748 fdclose(td, fp, fd);
749 fdrop(fp, td);
750 return (EINVAL);
751 }
752 shmfd = shm_alloc(td->td_ucred, cmode);
753 } else {
754 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
755 pr_path = td->td_ucred->cr_prison->pr_path;
756
757 /* Construct a full pathname for jailed callers. */
758 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
759 : strlcpy(path, pr_path, MAXPATHLEN);
760 error = copyinstr(uap->path, path + pr_pathlen,
761 MAXPATHLEN - pr_pathlen, NULL);
762 #ifdef KTRACE
763 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
764 ktrnamei(path);
765 #endif
766 /* Require paths to start with a '/' character. */
767 if (error == 0 && path[pr_pathlen] != '/')
768 error = EINVAL;
769 if (error) {
770 fdclose(td, fp, fd);
771 fdrop(fp, td);
772 free(path, M_SHMFD);
773 return (error);
774 }
775
776 fnv = fnv_32_str(path, FNV1_32_INIT);
777 sx_xlock(&shm_dict_lock);
778 shmfd = shm_lookup(path, fnv);
779 if (shmfd == NULL) {
780 /* Object does not yet exist, create it if requested. */
781 if (uap->flags & O_CREAT) {
782 #ifdef MAC
783 error = mac_posixshm_check_create(td->td_ucred,
784 path);
785 if (error == 0) {
786 #endif
787 shmfd = shm_alloc(td->td_ucred, cmode);
788 shm_insert(path, fnv, shmfd);
789 #ifdef MAC
790 }
791 #endif
792 } else {
793 free(path, M_SHMFD);
794 error = ENOENT;
795 }
796 } else {
797 /*
798 * Object already exists, obtain a new
799 * reference if requested and permitted.
800 */
801 free(path, M_SHMFD);
802 if ((uap->flags & (O_CREAT | O_EXCL)) ==
803 (O_CREAT | O_EXCL))
804 error = EEXIST;
805 else {
806 #ifdef MAC
807 error = mac_posixshm_check_open(td->td_ucred,
808 shmfd, FFLAGS(uap->flags & O_ACCMODE));
809 if (error == 0)
810 #endif
811 error = shm_access(shmfd, td->td_ucred,
812 FFLAGS(uap->flags & O_ACCMODE));
813 }
814
815 /*
816 * Truncate the file back to zero length if
817 * O_TRUNC was specified and the object was
818 * opened with read/write.
819 */
820 if (error == 0 &&
821 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
822 (O_RDWR | O_TRUNC)) {
823 #ifdef MAC
824 error = mac_posixshm_check_truncate(
825 td->td_ucred, fp->f_cred, shmfd);
826 if (error == 0)
827 #endif
828 shm_dotruncate(shmfd, 0);
829 }
830 if (error == 0)
831 shm_hold(shmfd);
832 }
833 sx_xunlock(&shm_dict_lock);
834
835 if (error) {
836 fdclose(td, fp, fd);
837 fdrop(fp, td);
838 return (error);
839 }
840 }
841
842 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
843
844 td->td_retval[0] = fd;
845 fdrop(fp, td);
846
847 return (0);
848 }
849
850 int
851 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
852 {
853 char *path;
854 const char *pr_path;
855 size_t pr_pathlen;
856 Fnv32_t fnv;
857 int error;
858
859 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
860 pr_path = td->td_ucred->cr_prison->pr_path;
861 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
862 : strlcpy(path, pr_path, MAXPATHLEN);
863 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen,
864 NULL);
865 if (error) {
866 free(path, M_TEMP);
867 return (error);
868 }
869 #ifdef KTRACE
870 if (KTRPOINT(curthread, KTR_NAMEI))
871 ktrnamei(path);
872 #endif
873 fnv = fnv_32_str(path, FNV1_32_INIT);
874 sx_xlock(&shm_dict_lock);
875 error = shm_remove(path, fnv, td->td_ucred);
876 sx_xunlock(&shm_dict_lock);
877 free(path, M_TEMP);
878
879 return (error);
880 }
881
882 /*
883 * mmap() helper to validate mmap() requests against shm object state
884 * and give mmap() the vm_object to use for the mapping.
885 */
886 int
887 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
888 vm_object_t *obj)
889 {
890
891 /*
892 * XXXRW: This validation is probably insufficient, and subject to
893 * sign errors. It should be fixed.
894 */
895 if (foff >= shmfd->shm_size ||
896 foff + objsize > round_page(shmfd->shm_size))
897 return (EINVAL);
898
899 mtx_lock(&shm_timestamp_lock);
900 vfs_timestamp(&shmfd->shm_atime);
901 mtx_unlock(&shm_timestamp_lock);
902 vm_object_reference(shmfd->shm_object);
903 *obj = shmfd->shm_object;
904 return (0);
905 }
906
907 static int
908 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
909 struct thread *td)
910 {
911 struct shmfd *shmfd;
912 int error;
913
914 error = 0;
915 shmfd = fp->f_data;
916 mtx_lock(&shm_timestamp_lock);
917 /*
918 * SUSv4 says that x bits of permission need not be affected.
919 * Be consistent with our shm_open there.
920 */
921 #ifdef MAC
922 error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
923 if (error != 0)
924 goto out;
925 #endif
926 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
927 shmfd->shm_gid, VADMIN, active_cred, NULL);
928 if (error != 0)
929 goto out;
930 shmfd->shm_mode = mode & ACCESSPERMS;
931 out:
932 mtx_unlock(&shm_timestamp_lock);
933 return (error);
934 }
935
936 static int
937 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
938 struct thread *td)
939 {
940 struct shmfd *shmfd;
941 int error;
942
943 error = 0;
944 shmfd = fp->f_data;
945 mtx_lock(&shm_timestamp_lock);
946 #ifdef MAC
947 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
948 if (error != 0)
949 goto out;
950 #endif
951 if (uid == (uid_t)-1)
952 uid = shmfd->shm_uid;
953 if (gid == (gid_t)-1)
954 gid = shmfd->shm_gid;
955 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
956 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
957 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
958 goto out;
959 shmfd->shm_uid = uid;
960 shmfd->shm_gid = gid;
961 out:
962 mtx_unlock(&shm_timestamp_lock);
963 return (error);
964 }
965
966 /*
967 * Helper routines to allow the backing object of a shared memory file
968 * descriptor to be mapped in the kernel.
969 */
970 int
971 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
972 {
973 struct shmfd *shmfd;
974 vm_offset_t kva, ofs;
975 vm_object_t obj;
976 int rv;
977
978 if (fp->f_type != DTYPE_SHM)
979 return (EINVAL);
980 shmfd = fp->f_data;
981 obj = shmfd->shm_object;
982 VM_OBJECT_WLOCK(obj);
983 /*
984 * XXXRW: This validation is probably insufficient, and subject to
985 * sign errors. It should be fixed.
986 */
987 if (offset >= shmfd->shm_size ||
988 offset + size > round_page(shmfd->shm_size)) {
989 VM_OBJECT_WUNLOCK(obj);
990 return (EINVAL);
991 }
992
993 shmfd->shm_kmappings++;
994 vm_object_reference_locked(obj);
995 VM_OBJECT_WUNLOCK(obj);
996
997 /* Map the object into the kernel_map and wire it. */
998 kva = vm_map_min(kernel_map);
999 ofs = offset & PAGE_MASK;
1000 offset = trunc_page(offset);
1001 size = round_page(size + ofs);
1002 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
1003 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
1004 VM_PROT_READ | VM_PROT_WRITE, 0);
1005 if (rv == KERN_SUCCESS) {
1006 rv = vm_map_wire(kernel_map, kva, kva + size,
1007 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
1008 if (rv == KERN_SUCCESS) {
1009 *memp = (void *)(kva + ofs);
1010 return (0);
1011 }
1012 vm_map_remove(kernel_map, kva, kva + size);
1013 } else
1014 vm_object_deallocate(obj);
1015
1016 /* On failure, drop our mapping reference. */
1017 VM_OBJECT_WLOCK(obj);
1018 shmfd->shm_kmappings--;
1019 VM_OBJECT_WUNLOCK(obj);
1020
1021 return (vm_mmap_to_errno(rv));
1022 }
1023
1024 /*
1025 * We require the caller to unmap the entire entry. This allows us to
1026 * safely decrement shm_kmappings when a mapping is removed.
1027 */
1028 int
1029 shm_unmap(struct file *fp, void *mem, size_t size)
1030 {
1031 struct shmfd *shmfd;
1032 vm_map_entry_t entry;
1033 vm_offset_t kva, ofs;
1034 vm_object_t obj;
1035 vm_pindex_t pindex;
1036 vm_prot_t prot;
1037 boolean_t wired;
1038 vm_map_t map;
1039 int rv;
1040
1041 if (fp->f_type != DTYPE_SHM)
1042 return (EINVAL);
1043 shmfd = fp->f_data;
1044 kva = (vm_offset_t)mem;
1045 ofs = kva & PAGE_MASK;
1046 kva = trunc_page(kva);
1047 size = round_page(size + ofs);
1048 map = kernel_map;
1049 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1050 &obj, &pindex, &prot, &wired);
1051 if (rv != KERN_SUCCESS)
1052 return (EINVAL);
1053 if (entry->start != kva || entry->end != kva + size) {
1054 vm_map_lookup_done(map, entry);
1055 return (EINVAL);
1056 }
1057 vm_map_lookup_done(map, entry);
1058 if (obj != shmfd->shm_object)
1059 return (EINVAL);
1060 vm_map_remove(map, kva, kva + size);
1061 VM_OBJECT_WLOCK(obj);
1062 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1063 shmfd->shm_kmappings--;
1064 VM_OBJECT_WUNLOCK(obj);
1065 return (0);
1066 }
1067
1068 void
1069 shm_path(struct shmfd *shmfd, char *path, size_t size)
1070 {
1071 const char *shm_path, *pr_path;
1072 size_t pr_pathlen;
1073
1074 if (shmfd->shm_path == NULL)
1075 return;
1076 sx_slock(&shm_dict_lock);
1077 shm_path = shmfd->shm_path;
1078 if (shm_path != NULL) {
1079 pr_path = curthread->td_ucred->cr_prison->pr_path;
1080 if (strcmp(pr_path, "/") != 0) {
1081 /* Return the jail-rooted pathname. */
1082 pr_pathlen = strlen(pr_path);
1083 if (strncmp(shm_path, pr_path, pr_pathlen) == 0 &&
1084 shm_path[pr_pathlen] == '/')
1085 shm_path += pr_pathlen;
1086 }
1087 strlcpy(path, shm_path, size);
1088 }
1089 sx_sunlock(&shm_dict_lock);
1090 }
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