1/*-
2 * Copyright (c) 2006 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 * (2) 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 * (3) Add support for this file type to fstat(1).
39 *
40 * (4) Resource limits? Does this need its own resource limits or are the
41 * existing limits in mmap(2) sufficient?
42 *
43 * (5) Partial page truncation. vnode_pager_setsize() will zero any parts
44 * of a partially mapped page as a result of ftruncate(2)/truncate(2).
45 * We can do the same (with the same pmap evil), but do we need to
46 * worry about the bits on disk if the page is swapped out or will the
47 * swapper zero the parts of a page that are invalid if the page is
48 * swapped back in for us?
49 *
50 * (6) Add MAC support in mac_biba(4) and mac_mls(4).
51 *
52 * (7) Add a MAC check_create() hook for creating new named objects.
53 */
54
55#include <sys/cdefs.h>
56__FBSDID("$FreeBSD: head/sys/kern/uipc_shm.c 193511 2009-06-05 14:55:22Z rwatson $");
57
58#include <sys/param.h>
59#include <sys/fcntl.h>
60#include <sys/file.h>
61#include <sys/filedesc.h>
62#include <sys/fnv_hash.h>
63#include <sys/kernel.h>
64#include <sys/lock.h>
65#include <sys/malloc.h>
66#include <sys/mman.h>
67#include <sys/mutex.h>
68#include <sys/proc.h>
69#include <sys/refcount.h>
70#include <sys/resourcevar.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
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_map.h>
85#include <vm/vm_object.h>
86#include <vm/vm_page.h>
87#include <vm/vm_pager.h>
88#include <vm/swap_pager.h>
89
90struct shm_mapping {
91 char *sm_path;
92 Fnv32_t sm_fnv;
93 struct shmfd *sm_shmfd;
94 LIST_ENTRY(shm_mapping) sm_link;
95};
96
97static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
98static LIST_HEAD(, shm_mapping) *shm_dictionary;
99static struct sx shm_dict_lock;
100static struct mtx shm_timestamp_lock;
101static u_long shm_hash;
102
103#define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
104
105static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
106static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
107static void shm_dict_init(void *arg);
108static void shm_drop(struct shmfd *shmfd);
109static struct shmfd *shm_hold(struct shmfd *shmfd);
110static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
111static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
112static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
113static void shm_dotruncate(struct shmfd *shmfd, off_t length);
114
115static fo_rdwr_t shm_read;
116static fo_rdwr_t shm_write;
117static fo_truncate_t shm_truncate;
118static fo_ioctl_t shm_ioctl;
119static fo_poll_t shm_poll;
120static fo_kqfilter_t shm_kqfilter;
121static fo_stat_t shm_stat;
122static fo_close_t shm_close;
123
124/* File descriptor operations. */
125static struct fileops shm_ops = {
126 .fo_read = shm_read,
127 .fo_write = shm_write,
128 .fo_truncate = shm_truncate,
129 .fo_ioctl = shm_ioctl,
130 .fo_poll = shm_poll,
131 .fo_kqfilter = shm_kqfilter,
132 .fo_stat = shm_stat,
133 .fo_close = shm_close,
134 .fo_flags = DFLAG_PASSABLE
135};
136
137FEATURE(posix_shm, "POSIX shared memory");
138
139static int
140shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
141 int flags, struct thread *td)
142{
143
144 return (EOPNOTSUPP);
145}
146
147static int
148shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
149 int flags, struct thread *td)
150{
151
152 return (EOPNOTSUPP);
153}
154
155static int
156shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
157 struct thread *td)
158{
159 struct shmfd *shmfd;
160#ifdef MAC
161 int error;
162#endif
163
164 shmfd = fp->f_data;
165#ifdef MAC
166 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
167 if (error)
168 return (error);
169#endif
170 shm_dotruncate(shmfd, length);
171 return (0);
172}
173
174static int
175shm_ioctl(struct file *fp, u_long com, void *data,
176 struct ucred *active_cred, struct thread *td)
177{
178
179 return (EOPNOTSUPP);
180}
181
182static int
183shm_poll(struct file *fp, int events, struct ucred *active_cred,
184 struct thread *td)
185{
186
187 return (EOPNOTSUPP);
188}
189
190static int
191shm_kqfilter(struct file *fp, struct knote *kn)
192{
193
194 return (EOPNOTSUPP);
195}
196
197static int
198shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
199 struct thread *td)
200{
201 struct shmfd *shmfd;
202#ifdef MAC
203 int error;
204#endif
205
206 shmfd = fp->f_data;
207
208#ifdef MAC
209 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
210 if (error)
211 return (error);
212#endif
213
214 /*
215 * Attempt to return sanish values for fstat() on a memory file
216 * descriptor.
217 */
218 bzero(sb, sizeof(*sb));
219 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
220 sb->st_blksize = PAGE_SIZE;
221 sb->st_size = shmfd->shm_size;
222 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
223 sb->st_atimespec = shmfd->shm_atime;
224 sb->st_ctimespec = shmfd->shm_ctime;
225 sb->st_mtimespec = shmfd->shm_mtime;
226 sb->st_birthtimespec = shmfd->shm_birthtime;
227 sb->st_uid = shmfd->shm_uid;
228 sb->st_gid = shmfd->shm_gid;
229
230 return (0);
231}
232
233static int
234shm_close(struct file *fp, struct thread *td)
235{
236 struct shmfd *shmfd;
237
238 shmfd = fp->f_data;
239 fp->f_data = NULL;
240 shm_drop(shmfd);
241
242 return (0);
243}
244
245static void
246shm_dotruncate(struct shmfd *shmfd, off_t length)
247{
248 vm_object_t object;
249 vm_page_t m;
250 vm_pindex_t nobjsize;
251
252 object = shmfd->shm_object;
253 VM_OBJECT_LOCK(object);
254 if (length == shmfd->shm_size) {
255 VM_OBJECT_UNLOCK(object);
256 return;
257 }
258 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
259
260 /* Are we shrinking? If so, trim the end. */
261 if (length < shmfd->shm_size) {
262 /* Toss in memory pages. */
263 if (nobjsize < object->size)
264 vm_object_page_remove(object, nobjsize, object->size,
265 FALSE);
266
267 /* Toss pages from swap. */
268 if (object->type == OBJT_SWAP)
269 swap_pager_freespace(object, nobjsize,
270 object->size - nobjsize);
271
272 /*
273 * If the last page is partially mapped, then zero out
274 * the garbage at the end of the page. See comments
275 * in vnode_pager_setsize() for more details.
276 *
277 * XXXJHB: This handles in memory pages, but what about
278 * a page swapped out to disk?
279 */
280 if ((length & PAGE_MASK) &&
281 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL &&
282 m->valid != 0) {
283 int base = (int)length & PAGE_MASK;
284 int size = PAGE_SIZE - base;
285
286 pmap_zero_page_area(m, base, size);
287
288 /*
289 * Update the valid bits to reflect the blocks that
290 * have been zeroed. Some of these valid bits may
291 * have already been set.
292 */
293 vm_page_set_valid(m, base, size);
294
295 /*
296 * Round "base" to the next block boundary so that the
297 * dirty bit for a partially zeroed block is not
298 * cleared.
299 */
300 base = roundup2(base, DEV_BSIZE);
301
302 vm_page_lock_queues();
303 vm_page_clear_dirty(m, base, PAGE_SIZE - base);
304 vm_page_unlock_queues();
305 } else if ((length & PAGE_MASK) &&
306 __predict_false(object->cache != NULL)) {
307 vm_page_cache_free(object, OFF_TO_IDX(length),
308 nobjsize);
309 }
310 }
311 shmfd->shm_size = length;
312 mtx_lock(&shm_timestamp_lock);
313 vfs_timestamp(&shmfd->shm_ctime);
314 shmfd->shm_mtime = shmfd->shm_ctime;
315 mtx_unlock(&shm_timestamp_lock);
316 object->size = nobjsize;
317 VM_OBJECT_UNLOCK(object);
318}
319
320/*
321 * shmfd object management including creation and reference counting
322 * routines.
323 */
324static struct shmfd *
325shm_alloc(struct ucred *ucred, mode_t mode)
326{
327 struct shmfd *shmfd;
328
329 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
330 shmfd->shm_size = 0;
331 shmfd->shm_uid = ucred->cr_uid;
332 shmfd->shm_gid = ucred->cr_gid;
333 shmfd->shm_mode = mode;
334 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
335 shmfd->shm_size, VM_PROT_DEFAULT, 0);
336 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
337 VM_OBJECT_LOCK(shmfd->shm_object);
338 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
339 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
340 VM_OBJECT_UNLOCK(shmfd->shm_object);
341 vfs_timestamp(&shmfd->shm_birthtime);
342 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
343 shmfd->shm_birthtime;
344 refcount_init(&shmfd->shm_refs, 1);
345#ifdef MAC
346 mac_posixshm_init(shmfd);
347 mac_posixshm_create(ucred, shmfd);
348#endif
349
350 return (shmfd);
351}
352
353static struct shmfd *
354shm_hold(struct shmfd *shmfd)
355{
356
357 refcount_acquire(&shmfd->shm_refs);
358 return (shmfd);
359}
360
361static void
362shm_drop(struct shmfd *shmfd)
363{
364
365 if (refcount_release(&shmfd->shm_refs)) {
366#ifdef MAC
367 mac_posixshm_destroy(shmfd);
368#endif
369 vm_object_deallocate(shmfd->shm_object);
370 free(shmfd, M_SHMFD);
371 }
372}
373
374/*
375 * Determine if the credentials have sufficient permissions for a
376 * specified combination of FREAD and FWRITE.
377 */
378static int
379shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
380{
381 accmode_t accmode;
382
383 accmode = 0;
384 if (flags & FREAD)
385 accmode |= VREAD;
386 if (flags & FWRITE)
387 accmode |= VWRITE;
388 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
389 accmode, ucred, NULL));
390}
391
392/*
393 * Dictionary management. We maintain an in-kernel dictionary to map
394 * paths to shmfd objects. We use the FNV hash on the path to store
395 * the mappings in a hash table.
396 */
397static void
398shm_dict_init(void *arg)
399{
400
401 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
402 sx_init(&shm_dict_lock, "shm dictionary");
403 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
404}
405SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL);
406
407static struct shmfd *
408shm_lookup(char *path, Fnv32_t fnv)
409{
410 struct shm_mapping *map;
411
412 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
413 if (map->sm_fnv != fnv)
414 continue;
415 if (strcmp(map->sm_path, path) == 0)
416 return (map->sm_shmfd);
417 }
418
419 return (NULL);
420}
421
422static void
423shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
424{
425 struct shm_mapping *map;
426
427 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
428 map->sm_path = path;
429 map->sm_fnv = fnv;
430 map->sm_shmfd = shm_hold(shmfd);
431 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
432}
433
434static int
435shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
436{
437 struct shm_mapping *map;
438 int error;
439
440 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
441 if (map->sm_fnv != fnv)
442 continue;
443 if (strcmp(map->sm_path, path) == 0) {
444#ifdef MAC
445 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
446 if (error)
447 return (error);
448#endif
449 error = shm_access(map->sm_shmfd, ucred,
450 FREAD | FWRITE);
451 if (error)
452 return (error);
453 LIST_REMOVE(map, sm_link);
454 shm_drop(map->sm_shmfd);
455 free(map->sm_path, M_SHMFD);
456 free(map, M_SHMFD);
457 return (0);
458 }
459 }
460
461 return (ENOENT);
462}
463
464/* System calls. */
465int
466shm_open(struct thread *td, struct shm_open_args *uap)
467{
468 struct filedesc *fdp;
469 struct shmfd *shmfd;
470 struct file *fp;
471 char *path;
472 Fnv32_t fnv;
473 mode_t cmode;
474 int fd, error;
475
476 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
477 (uap->flags & O_ACCMODE) != O_RDWR)
478 return (EINVAL);
479
480 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0)
481 return (EINVAL);
482
483 fdp = td->td_proc->p_fd;
484 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
485
486 error = falloc(td, &fp, &fd);
487 if (error)
488 return (error);
489
490 /* A SHM_ANON path pointer creates an anonymous object. */
491 if (uap->path == SHM_ANON) {
492 /* A read-only anonymous object is pointless. */
493 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
494 fdclose(fdp, fp, fd, td);
495 fdrop(fp, td);
496 return (EINVAL);
497 }
498 shmfd = shm_alloc(td->td_ucred, cmode);
499 } else {
500 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
501 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
502
503 /* Require paths to start with a '/' character. */
504 if (error == 0 && path[0] != '/')
505 error = EINVAL;
506 if (error) {
507 fdclose(fdp, fp, fd, td);
508 fdrop(fp, td);
509 free(path, M_SHMFD);
510 return (error);
511 }
512
513 fnv = fnv_32_str(path, FNV1_32_INIT);
514 sx_xlock(&shm_dict_lock);
515 shmfd = shm_lookup(path, fnv);
516 if (shmfd == NULL) {
517 /* Object does not yet exist, create it if requested. */
518 if (uap->flags & O_CREAT) {
519 shmfd = shm_alloc(td->td_ucred, cmode);
520 shm_insert(path, fnv, shmfd);
521 } else {
522 free(path, M_SHMFD);
523 error = ENOENT;
524 }
525 } else {
526 /*
527 * Object already exists, obtain a new
528 * reference if requested and permitted.
529 */
530 free(path, M_SHMFD);
531 if ((uap->flags & (O_CREAT | O_EXCL)) ==
532 (O_CREAT | O_EXCL))
533 error = EEXIST;
534 else {
535#ifdef MAC
536 error = mac_posixshm_check_open(td->td_ucred,
537 shmfd);
538 if (error == 0)
539#endif
540 error = shm_access(shmfd, td->td_ucred,
541 FFLAGS(uap->flags & O_ACCMODE));
542 }
543
544 /*
545 * Truncate the file back to zero length if
546 * O_TRUNC was specified and the object was
547 * opened with read/write.
548 */
549 if (error == 0 &&
550 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
551 (O_RDWR | O_TRUNC)) {
552#ifdef MAC
553 error = mac_posixshm_check_truncate(
554 td->td_ucred, fp->f_cred, shmfd);
555 if (error == 0)
556#endif
557 shm_dotruncate(shmfd, 0);
558 }
559 if (error == 0)
560 shm_hold(shmfd);
561 }
562 sx_xunlock(&shm_dict_lock);
563
564 if (error) {
565 fdclose(fdp, fp, fd, td);
566 fdrop(fp, td);
567 return (error);
568 }
569 }
570
571 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
572
573 FILEDESC_XLOCK(fdp);
574 if (fdp->fd_ofiles[fd] == fp)
575 fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
576 FILEDESC_XUNLOCK(fdp);
577 td->td_retval[0] = fd;
578 fdrop(fp, td);
579
580 return (0);
581}
582
583int
584shm_unlink(struct thread *td, struct shm_unlink_args *uap)
585{
586 char *path;
587 Fnv32_t fnv;
588 int error;
589
590 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
591 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
592 if (error) {
593 free(path, M_TEMP);
594 return (error);
595 }
596
597 fnv = fnv_32_str(path, FNV1_32_INIT);
598 sx_xlock(&shm_dict_lock);
599 error = shm_remove(path, fnv, td->td_ucred);
600 sx_xunlock(&shm_dict_lock);
601 free(path, M_TEMP);
602
603 return (error);
604}
605
606/*
607 * mmap() helper to validate mmap() requests against shm object state
608 * and give mmap() the vm_object to use for the mapping.
609 */
610int
611shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
612 vm_object_t *obj)
613{
614
615 /*
616 * XXXRW: This validation is probably insufficient, and subject to
617 * sign errors. It should be fixed.
618 */
619 if (foff >= shmfd->shm_size ||
620 foff + objsize > round_page(shmfd->shm_size))
621 return (EINVAL);
622
623 mtx_lock(&shm_timestamp_lock);
624 vfs_timestamp(&shmfd->shm_atime);
625 mtx_unlock(&shm_timestamp_lock);
626 vm_object_reference(shmfd->shm_object);
627 *obj = shmfd->shm_object;
628 return (0);
629}
2 * Copyright (c) 2006 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 * (2) 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 * (3) Add support for this file type to fstat(1).
39 *
40 * (4) Resource limits? Does this need its own resource limits or are the
41 * existing limits in mmap(2) sufficient?
42 *
43 * (5) Partial page truncation. vnode_pager_setsize() will zero any parts
44 * of a partially mapped page as a result of ftruncate(2)/truncate(2).
45 * We can do the same (with the same pmap evil), but do we need to
46 * worry about the bits on disk if the page is swapped out or will the
47 * swapper zero the parts of a page that are invalid if the page is
48 * swapped back in for us?
49 *
50 * (6) Add MAC support in mac_biba(4) and mac_mls(4).
51 *
52 * (7) Add a MAC check_create() hook for creating new named objects.
53 */
54
55#include <sys/cdefs.h>
56__FBSDID("$FreeBSD: head/sys/kern/uipc_shm.c 193511 2009-06-05 14:55:22Z rwatson $");
57
58#include <sys/param.h>
59#include <sys/fcntl.h>
60#include <sys/file.h>
61#include <sys/filedesc.h>
62#include <sys/fnv_hash.h>
63#include <sys/kernel.h>
64#include <sys/lock.h>
65#include <sys/malloc.h>
66#include <sys/mman.h>
67#include <sys/mutex.h>
68#include <sys/proc.h>
69#include <sys/refcount.h>
70#include <sys/resourcevar.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
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_map.h>
85#include <vm/vm_object.h>
86#include <vm/vm_page.h>
87#include <vm/vm_pager.h>
88#include <vm/swap_pager.h>
89
90struct shm_mapping {
91 char *sm_path;
92 Fnv32_t sm_fnv;
93 struct shmfd *sm_shmfd;
94 LIST_ENTRY(shm_mapping) sm_link;
95};
96
97static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
98static LIST_HEAD(, shm_mapping) *shm_dictionary;
99static struct sx shm_dict_lock;
100static struct mtx shm_timestamp_lock;
101static u_long shm_hash;
102
103#define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
104
105static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
106static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
107static void shm_dict_init(void *arg);
108static void shm_drop(struct shmfd *shmfd);
109static struct shmfd *shm_hold(struct shmfd *shmfd);
110static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
111static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
112static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
113static void shm_dotruncate(struct shmfd *shmfd, off_t length);
114
115static fo_rdwr_t shm_read;
116static fo_rdwr_t shm_write;
117static fo_truncate_t shm_truncate;
118static fo_ioctl_t shm_ioctl;
119static fo_poll_t shm_poll;
120static fo_kqfilter_t shm_kqfilter;
121static fo_stat_t shm_stat;
122static fo_close_t shm_close;
123
124/* File descriptor operations. */
125static struct fileops shm_ops = {
126 .fo_read = shm_read,
127 .fo_write = shm_write,
128 .fo_truncate = shm_truncate,
129 .fo_ioctl = shm_ioctl,
130 .fo_poll = shm_poll,
131 .fo_kqfilter = shm_kqfilter,
132 .fo_stat = shm_stat,
133 .fo_close = shm_close,
134 .fo_flags = DFLAG_PASSABLE
135};
136
137FEATURE(posix_shm, "POSIX shared memory");
138
139static int
140shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
141 int flags, struct thread *td)
142{
143
144 return (EOPNOTSUPP);
145}
146
147static int
148shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
149 int flags, struct thread *td)
150{
151
152 return (EOPNOTSUPP);
153}
154
155static int
156shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
157 struct thread *td)
158{
159 struct shmfd *shmfd;
160#ifdef MAC
161 int error;
162#endif
163
164 shmfd = fp->f_data;
165#ifdef MAC
166 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
167 if (error)
168 return (error);
169#endif
170 shm_dotruncate(shmfd, length);
171 return (0);
172}
173
174static int
175shm_ioctl(struct file *fp, u_long com, void *data,
176 struct ucred *active_cred, struct thread *td)
177{
178
179 return (EOPNOTSUPP);
180}
181
182static int
183shm_poll(struct file *fp, int events, struct ucred *active_cred,
184 struct thread *td)
185{
186
187 return (EOPNOTSUPP);
188}
189
190static int
191shm_kqfilter(struct file *fp, struct knote *kn)
192{
193
194 return (EOPNOTSUPP);
195}
196
197static int
198shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
199 struct thread *td)
200{
201 struct shmfd *shmfd;
202#ifdef MAC
203 int error;
204#endif
205
206 shmfd = fp->f_data;
207
208#ifdef MAC
209 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
210 if (error)
211 return (error);
212#endif
213
214 /*
215 * Attempt to return sanish values for fstat() on a memory file
216 * descriptor.
217 */
218 bzero(sb, sizeof(*sb));
219 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
220 sb->st_blksize = PAGE_SIZE;
221 sb->st_size = shmfd->shm_size;
222 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
223 sb->st_atimespec = shmfd->shm_atime;
224 sb->st_ctimespec = shmfd->shm_ctime;
225 sb->st_mtimespec = shmfd->shm_mtime;
226 sb->st_birthtimespec = shmfd->shm_birthtime;
227 sb->st_uid = shmfd->shm_uid;
228 sb->st_gid = shmfd->shm_gid;
229
230 return (0);
231}
232
233static int
234shm_close(struct file *fp, struct thread *td)
235{
236 struct shmfd *shmfd;
237
238 shmfd = fp->f_data;
239 fp->f_data = NULL;
240 shm_drop(shmfd);
241
242 return (0);
243}
244
245static void
246shm_dotruncate(struct shmfd *shmfd, off_t length)
247{
248 vm_object_t object;
249 vm_page_t m;
250 vm_pindex_t nobjsize;
251
252 object = shmfd->shm_object;
253 VM_OBJECT_LOCK(object);
254 if (length == shmfd->shm_size) {
255 VM_OBJECT_UNLOCK(object);
256 return;
257 }
258 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
259
260 /* Are we shrinking? If so, trim the end. */
261 if (length < shmfd->shm_size) {
262 /* Toss in memory pages. */
263 if (nobjsize < object->size)
264 vm_object_page_remove(object, nobjsize, object->size,
265 FALSE);
266
267 /* Toss pages from swap. */
268 if (object->type == OBJT_SWAP)
269 swap_pager_freespace(object, nobjsize,
270 object->size - nobjsize);
271
272 /*
273 * If the last page is partially mapped, then zero out
274 * the garbage at the end of the page. See comments
275 * in vnode_pager_setsize() for more details.
276 *
277 * XXXJHB: This handles in memory pages, but what about
278 * a page swapped out to disk?
279 */
280 if ((length & PAGE_MASK) &&
281 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL &&
282 m->valid != 0) {
283 int base = (int)length & PAGE_MASK;
284 int size = PAGE_SIZE - base;
285
286 pmap_zero_page_area(m, base, size);
287
288 /*
289 * Update the valid bits to reflect the blocks that
290 * have been zeroed. Some of these valid bits may
291 * have already been set.
292 */
293 vm_page_set_valid(m, base, size);
294
295 /*
296 * Round "base" to the next block boundary so that the
297 * dirty bit for a partially zeroed block is not
298 * cleared.
299 */
300 base = roundup2(base, DEV_BSIZE);
301
302 vm_page_lock_queues();
303 vm_page_clear_dirty(m, base, PAGE_SIZE - base);
304 vm_page_unlock_queues();
305 } else if ((length & PAGE_MASK) &&
306 __predict_false(object->cache != NULL)) {
307 vm_page_cache_free(object, OFF_TO_IDX(length),
308 nobjsize);
309 }
310 }
311 shmfd->shm_size = length;
312 mtx_lock(&shm_timestamp_lock);
313 vfs_timestamp(&shmfd->shm_ctime);
314 shmfd->shm_mtime = shmfd->shm_ctime;
315 mtx_unlock(&shm_timestamp_lock);
316 object->size = nobjsize;
317 VM_OBJECT_UNLOCK(object);
318}
319
320/*
321 * shmfd object management including creation and reference counting
322 * routines.
323 */
324static struct shmfd *
325shm_alloc(struct ucred *ucred, mode_t mode)
326{
327 struct shmfd *shmfd;
328
329 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
330 shmfd->shm_size = 0;
331 shmfd->shm_uid = ucred->cr_uid;
332 shmfd->shm_gid = ucred->cr_gid;
333 shmfd->shm_mode = mode;
334 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
335 shmfd->shm_size, VM_PROT_DEFAULT, 0);
336 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
337 VM_OBJECT_LOCK(shmfd->shm_object);
338 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
339 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
340 VM_OBJECT_UNLOCK(shmfd->shm_object);
341 vfs_timestamp(&shmfd->shm_birthtime);
342 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
343 shmfd->shm_birthtime;
344 refcount_init(&shmfd->shm_refs, 1);
345#ifdef MAC
346 mac_posixshm_init(shmfd);
347 mac_posixshm_create(ucred, shmfd);
348#endif
349
350 return (shmfd);
351}
352
353static struct shmfd *
354shm_hold(struct shmfd *shmfd)
355{
356
357 refcount_acquire(&shmfd->shm_refs);
358 return (shmfd);
359}
360
361static void
362shm_drop(struct shmfd *shmfd)
363{
364
365 if (refcount_release(&shmfd->shm_refs)) {
366#ifdef MAC
367 mac_posixshm_destroy(shmfd);
368#endif
369 vm_object_deallocate(shmfd->shm_object);
370 free(shmfd, M_SHMFD);
371 }
372}
373
374/*
375 * Determine if the credentials have sufficient permissions for a
376 * specified combination of FREAD and FWRITE.
377 */
378static int
379shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
380{
381 accmode_t accmode;
382
383 accmode = 0;
384 if (flags & FREAD)
385 accmode |= VREAD;
386 if (flags & FWRITE)
387 accmode |= VWRITE;
388 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
389 accmode, ucred, NULL));
390}
391
392/*
393 * Dictionary management. We maintain an in-kernel dictionary to map
394 * paths to shmfd objects. We use the FNV hash on the path to store
395 * the mappings in a hash table.
396 */
397static void
398shm_dict_init(void *arg)
399{
400
401 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
402 sx_init(&shm_dict_lock, "shm dictionary");
403 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
404}
405SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL);
406
407static struct shmfd *
408shm_lookup(char *path, Fnv32_t fnv)
409{
410 struct shm_mapping *map;
411
412 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
413 if (map->sm_fnv != fnv)
414 continue;
415 if (strcmp(map->sm_path, path) == 0)
416 return (map->sm_shmfd);
417 }
418
419 return (NULL);
420}
421
422static void
423shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
424{
425 struct shm_mapping *map;
426
427 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
428 map->sm_path = path;
429 map->sm_fnv = fnv;
430 map->sm_shmfd = shm_hold(shmfd);
431 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
432}
433
434static int
435shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
436{
437 struct shm_mapping *map;
438 int error;
439
440 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
441 if (map->sm_fnv != fnv)
442 continue;
443 if (strcmp(map->sm_path, path) == 0) {
444#ifdef MAC
445 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
446 if (error)
447 return (error);
448#endif
449 error = shm_access(map->sm_shmfd, ucred,
450 FREAD | FWRITE);
451 if (error)
452 return (error);
453 LIST_REMOVE(map, sm_link);
454 shm_drop(map->sm_shmfd);
455 free(map->sm_path, M_SHMFD);
456 free(map, M_SHMFD);
457 return (0);
458 }
459 }
460
461 return (ENOENT);
462}
463
464/* System calls. */
465int
466shm_open(struct thread *td, struct shm_open_args *uap)
467{
468 struct filedesc *fdp;
469 struct shmfd *shmfd;
470 struct file *fp;
471 char *path;
472 Fnv32_t fnv;
473 mode_t cmode;
474 int fd, error;
475
476 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
477 (uap->flags & O_ACCMODE) != O_RDWR)
478 return (EINVAL);
479
480 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0)
481 return (EINVAL);
482
483 fdp = td->td_proc->p_fd;
484 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
485
486 error = falloc(td, &fp, &fd);
487 if (error)
488 return (error);
489
490 /* A SHM_ANON path pointer creates an anonymous object. */
491 if (uap->path == SHM_ANON) {
492 /* A read-only anonymous object is pointless. */
493 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
494 fdclose(fdp, fp, fd, td);
495 fdrop(fp, td);
496 return (EINVAL);
497 }
498 shmfd = shm_alloc(td->td_ucred, cmode);
499 } else {
500 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
501 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
502
503 /* Require paths to start with a '/' character. */
504 if (error == 0 && path[0] != '/')
505 error = EINVAL;
506 if (error) {
507 fdclose(fdp, fp, fd, td);
508 fdrop(fp, td);
509 free(path, M_SHMFD);
510 return (error);
511 }
512
513 fnv = fnv_32_str(path, FNV1_32_INIT);
514 sx_xlock(&shm_dict_lock);
515 shmfd = shm_lookup(path, fnv);
516 if (shmfd == NULL) {
517 /* Object does not yet exist, create it if requested. */
518 if (uap->flags & O_CREAT) {
519 shmfd = shm_alloc(td->td_ucred, cmode);
520 shm_insert(path, fnv, shmfd);
521 } else {
522 free(path, M_SHMFD);
523 error = ENOENT;
524 }
525 } else {
526 /*
527 * Object already exists, obtain a new
528 * reference if requested and permitted.
529 */
530 free(path, M_SHMFD);
531 if ((uap->flags & (O_CREAT | O_EXCL)) ==
532 (O_CREAT | O_EXCL))
533 error = EEXIST;
534 else {
535#ifdef MAC
536 error = mac_posixshm_check_open(td->td_ucred,
537 shmfd);
538 if (error == 0)
539#endif
540 error = shm_access(shmfd, td->td_ucred,
541 FFLAGS(uap->flags & O_ACCMODE));
542 }
543
544 /*
545 * Truncate the file back to zero length if
546 * O_TRUNC was specified and the object was
547 * opened with read/write.
548 */
549 if (error == 0 &&
550 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
551 (O_RDWR | O_TRUNC)) {
552#ifdef MAC
553 error = mac_posixshm_check_truncate(
554 td->td_ucred, fp->f_cred, shmfd);
555 if (error == 0)
556#endif
557 shm_dotruncate(shmfd, 0);
558 }
559 if (error == 0)
560 shm_hold(shmfd);
561 }
562 sx_xunlock(&shm_dict_lock);
563
564 if (error) {
565 fdclose(fdp, fp, fd, td);
566 fdrop(fp, td);
567 return (error);
568 }
569 }
570
571 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
572
573 FILEDESC_XLOCK(fdp);
574 if (fdp->fd_ofiles[fd] == fp)
575 fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
576 FILEDESC_XUNLOCK(fdp);
577 td->td_retval[0] = fd;
578 fdrop(fp, td);
579
580 return (0);
581}
582
583int
584shm_unlink(struct thread *td, struct shm_unlink_args *uap)
585{
586 char *path;
587 Fnv32_t fnv;
588 int error;
589
590 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
591 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
592 if (error) {
593 free(path, M_TEMP);
594 return (error);
595 }
596
597 fnv = fnv_32_str(path, FNV1_32_INIT);
598 sx_xlock(&shm_dict_lock);
599 error = shm_remove(path, fnv, td->td_ucred);
600 sx_xunlock(&shm_dict_lock);
601 free(path, M_TEMP);
602
603 return (error);
604}
605
606/*
607 * mmap() helper to validate mmap() requests against shm object state
608 * and give mmap() the vm_object to use for the mapping.
609 */
610int
611shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
612 vm_object_t *obj)
613{
614
615 /*
616 * XXXRW: This validation is probably insufficient, and subject to
617 * sign errors. It should be fixed.
618 */
619 if (foff >= shmfd->shm_size ||
620 foff + objsize > round_page(shmfd->shm_size))
621 return (EINVAL);
622
623 mtx_lock(&shm_timestamp_lock);
624 vfs_timestamp(&shmfd->shm_atime);
625 mtx_unlock(&shm_timestamp_lock);
626 vm_object_reference(shmfd->shm_object);
627 *obj = shmfd->shm_object;
628 return (0);
629}