summaryrefslogtreecommitdiffstats
path: root/sys/kern/uipc_shm.c
blob: f11c6eaed7b54e582360a637631dd69262ee4fe4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
/*-
 * Copyright (c) 2006, 2011 Robert N. M. Watson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Support for shared swap-backed anonymous memory objects via
 * shm_open(2) and shm_unlink(2).  While most of the implementation is
 * here, vm_mmap.c contains mapping logic changes.
 *
 * TODO:
 *
 * (1) Need to export data to a userland tool via a sysctl.  Should ipcs(1)
 *     and ipcrm(1) be expanded or should new tools to manage both POSIX
 *     kernel semaphores and POSIX shared memory be written?
 *
 * (2) Add support for this file type to fstat(1).
 *
 * (3) Resource limits?  Does this need its own resource limits or are the
 *     existing limits in mmap(2) sufficient?
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_capsicum.h"
#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/conf.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/uio.h>
#include <sys/signal.h>
#include <sys/ktrace.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/refcount.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <sys/sx.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/unistd.h>

#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_extern.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>

struct shm_mapping {
	char		*sm_path;
	Fnv32_t		sm_fnv;
	struct shmfd	*sm_shmfd;
	LIST_ENTRY(shm_mapping) sm_link;
};

static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
static LIST_HEAD(, shm_mapping) *shm_dictionary;
static struct sx shm_dict_lock;
static struct mtx shm_timestamp_lock;
static u_long shm_hash;
static struct unrhdr *shm_ino_unr;
static dev_t shm_dev_ino;

#define	SHM_HASH(fnv)	(&shm_dictionary[(fnv) & shm_hash])

static int	shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
static void	shm_init(void *arg);
static void	shm_drop(struct shmfd *shmfd);
static struct shmfd *shm_hold(struct shmfd *shmfd);
static void	shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
static int	shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
static int	shm_dotruncate(struct shmfd *shmfd, off_t length);

static fo_rdwr_t	shm_read;
static fo_rdwr_t	shm_write;
static fo_truncate_t	shm_truncate;
static fo_ioctl_t	shm_ioctl;
static fo_poll_t	shm_poll;
static fo_kqfilter_t	shm_kqfilter;
static fo_stat_t	shm_stat;
static fo_close_t	shm_close;
static fo_chmod_t	shm_chmod;
static fo_chown_t	shm_chown;
static fo_seek_t	shm_seek;

/* File descriptor operations. */
static struct fileops shm_ops = {
	.fo_read = shm_read,
	.fo_write = shm_write,
	.fo_truncate = shm_truncate,
	.fo_ioctl = shm_ioctl,
	.fo_poll = shm_poll,
	.fo_kqfilter = shm_kqfilter,
	.fo_stat = shm_stat,
	.fo_close = shm_close,
	.fo_chmod = shm_chmod,
	.fo_chown = shm_chown,
	.fo_sendfile = vn_sendfile,
	.fo_seek = shm_seek,
	.fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
};

FEATURE(posix_shm, "POSIX shared memory");

static int
uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
{
	vm_page_t m;
	vm_pindex_t idx;
	size_t tlen;
	int error, offset, rv;

	idx = OFF_TO_IDX(uio->uio_offset);
	offset = uio->uio_offset & PAGE_MASK;
	tlen = MIN(PAGE_SIZE - offset, len);

	VM_OBJECT_WLOCK(obj);

	/*
	 * Parallel reads of the page content from disk are prevented
	 * by exclusive busy.
	 *
	 * Although the tmpfs vnode lock is held here, it is
	 * nonetheless safe to sleep waiting for a free page.  The
	 * pageout daemon does not need to acquire the tmpfs vnode
	 * lock to page out tobj's pages because tobj is a OBJT_SWAP
	 * type object.
	 */
	m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
	if (m->valid != VM_PAGE_BITS_ALL) {
		if (vm_pager_has_page(obj, idx, NULL, NULL)) {
			rv = vm_pager_get_pages(obj, &m, 1, 0);
			m = vm_page_lookup(obj, idx);
			if (m == NULL) {
				printf(
		    "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n",
				    obj, idx, rv);
				VM_OBJECT_WUNLOCK(obj);
				return (EIO);
			}
			if (rv != VM_PAGER_OK) {
				printf(
	    "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
				    obj, idx, m->valid, rv);
				vm_page_lock(m);
				vm_page_free(m);
				vm_page_unlock(m);
				VM_OBJECT_WUNLOCK(obj);
				return (EIO);
			}
		} else
			vm_page_zero_invalid(m, TRUE);
	}
	vm_page_xunbusy(m);
	vm_page_lock(m);
	vm_page_hold(m);
	if (m->queue == PQ_NONE) {
		vm_page_deactivate(m);
	} else {
		/* Requeue to maintain LRU ordering. */
		vm_page_requeue(m);
	}
	vm_page_unlock(m);
	VM_OBJECT_WUNLOCK(obj);
	error = uiomove_fromphys(&m, offset, tlen, uio);
	if (uio->uio_rw == UIO_WRITE && error == 0) {
		VM_OBJECT_WLOCK(obj);
		vm_page_dirty(m);
		vm_pager_page_unswapped(m);
		VM_OBJECT_WUNLOCK(obj);
	}
	vm_page_lock(m);
	vm_page_unhold(m);
	vm_page_unlock(m);

	return (error);
}

int
uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
{
	ssize_t resid;
	size_t len;
	int error;

	error = 0;
	while ((resid = uio->uio_resid) > 0) {
		if (obj_size <= uio->uio_offset)
			break;
		len = MIN(obj_size - uio->uio_offset, resid);
		if (len == 0)
			break;
		error = uiomove_object_page(obj, len, uio);
		if (error != 0 || resid == uio->uio_resid)
			break;
	}
	return (error);
}

static int
shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
{
	struct shmfd *shmfd;
	off_t foffset;
	int error;

	shmfd = fp->f_data;
	foffset = foffset_lock(fp, 0);
	error = 0;
	switch (whence) {
	case L_INCR:
		if (foffset < 0 ||
		    (offset > 0 && foffset > OFF_MAX - offset)) {
			error = EOVERFLOW;
			break;
		}
		offset += foffset;
		break;
	case L_XTND:
		if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
			error = EOVERFLOW;
			break;
		}
		offset += shmfd->shm_size;
		break;
	case L_SET:
		break;
	default:
		error = EINVAL;
	}
	if (error == 0) {
		if (offset < 0 || offset > shmfd->shm_size)
			error = EINVAL;
		else
			*(off_t *)(td->td_retval) = offset;
	}
	foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
	return (error);
}

static int
shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
    int flags, struct thread *td)
{
	struct shmfd *shmfd;
	void *rl_cookie;
	int error;

	shmfd = fp->f_data;
	foffset_lock_uio(fp, uio, flags);
	rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
	    uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
#ifdef MAC
	error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
	if (error)
		return (error);
#endif
	error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
	rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
	foffset_unlock_uio(fp, uio, flags);
	return (error);
}

static int
shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
    int flags, struct thread *td)
{
	struct shmfd *shmfd;
	void *rl_cookie;
	int error;

	shmfd = fp->f_data;
#ifdef MAC
	error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
	if (error)
		return (error);
#endif
	foffset_lock_uio(fp, uio, flags);
	if ((flags & FOF_OFFSET) == 0) {
		rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
		    &shmfd->shm_mtx);
	} else {
		rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
		    uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
	}

	error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
	rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
	foffset_unlock_uio(fp, uio, flags);
	return (error);
}

static int
shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
    struct thread *td)
{
	struct shmfd *shmfd;
#ifdef MAC
	int error;
#endif

	shmfd = fp->f_data;
#ifdef MAC
	error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
	if (error)
		return (error);
#endif
	return (shm_dotruncate(shmfd, length));
}

static int
shm_ioctl(struct file *fp, u_long com, void *data,
    struct ucred *active_cred, struct thread *td)
{

	return (EOPNOTSUPP);
}

static int
shm_poll(struct file *fp, int events, struct ucred *active_cred,
    struct thread *td)
{

	return (EOPNOTSUPP);
}

static int
shm_kqfilter(struct file *fp, struct knote *kn)
{

	return (EOPNOTSUPP);
}

static int
shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
    struct thread *td)
{
	struct shmfd *shmfd;
#ifdef MAC
	int error;
#endif

	shmfd = fp->f_data;

#ifdef MAC
	error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
	if (error)
		return (error);
#endif
	
	/*
	 * Attempt to return sanish values for fstat() on a memory file
	 * descriptor.
	 */
	bzero(sb, sizeof(*sb));
	sb->st_blksize = PAGE_SIZE;
	sb->st_size = shmfd->shm_size;
	sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
	mtx_lock(&shm_timestamp_lock);
	sb->st_atim = shmfd->shm_atime;
	sb->st_ctim = shmfd->shm_ctime;
	sb->st_mtim = shmfd->shm_mtime;
	sb->st_birthtim = shmfd->shm_birthtime;
	sb->st_mode = S_IFREG | shmfd->shm_mode;		/* XXX */
	sb->st_uid = shmfd->shm_uid;
	sb->st_gid = shmfd->shm_gid;
	mtx_unlock(&shm_timestamp_lock);
	sb->st_dev = shm_dev_ino;
	sb->st_ino = shmfd->shm_ino;

	return (0);
}

static int
shm_close(struct file *fp, struct thread *td)
{
	struct shmfd *shmfd;

	shmfd = fp->f_data;
	fp->f_data = NULL;
	shm_drop(shmfd);

	return (0);
}

static int
shm_dotruncate(struct shmfd *shmfd, off_t length)
{
	vm_object_t object;
	vm_page_t m, ma[1];
	vm_pindex_t idx, nobjsize;
	vm_ooffset_t delta;
	int base, rv;

	object = shmfd->shm_object;
	VM_OBJECT_WLOCK(object);
	if (length == shmfd->shm_size) {
		VM_OBJECT_WUNLOCK(object);
		return (0);
	}
	nobjsize = OFF_TO_IDX(length + PAGE_MASK);

	/* Are we shrinking?  If so, trim the end. */
	if (length < shmfd->shm_size) {
		/*
		 * Disallow any requests to shrink the size if this
		 * object is mapped into the kernel.
		 */
		if (shmfd->shm_kmappings > 0) {
			VM_OBJECT_WUNLOCK(object);
			return (EBUSY);
		}

		/*
		 * Zero the truncated part of the last page.
		 */
		base = length & PAGE_MASK;
		if (base != 0) {
			idx = OFF_TO_IDX(length);
retry:
			m = vm_page_lookup(object, idx);
			if (m != NULL) {
				if (vm_page_sleep_if_busy(m, "shmtrc"))
					goto retry;
			} else if (vm_pager_has_page(object, idx, NULL, NULL)) {
				m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
				if (m == NULL) {
					VM_OBJECT_WUNLOCK(object);
					VM_WAIT;
					VM_OBJECT_WLOCK(object);
					goto retry;
				} else if (m->valid != VM_PAGE_BITS_ALL) {
					ma[0] = m;
					rv = vm_pager_get_pages(object, ma, 1,
					    0);
					m = vm_page_lookup(object, idx);
				} else
					/* A cached page was reactivated. */
					rv = VM_PAGER_OK;
				vm_page_lock(m);
				if (rv == VM_PAGER_OK) {
					vm_page_deactivate(m);
					vm_page_unlock(m);
					vm_page_xunbusy(m);
				} else {
					vm_page_free(m);
					vm_page_unlock(m);
					VM_OBJECT_WUNLOCK(object);
					return (EIO);
				}
			}
			if (m != NULL) {
				pmap_zero_page_area(m, base, PAGE_SIZE - base);
				KASSERT(m->valid == VM_PAGE_BITS_ALL,
				    ("shm_dotruncate: page %p is invalid", m));
				vm_page_dirty(m);
				vm_pager_page_unswapped(m);
			}
		}
		delta = ptoa(object->size - nobjsize);

		/* Toss in memory pages. */
		if (nobjsize < object->size)
			vm_object_page_remove(object, nobjsize, object->size,
			    0);

		/* Toss pages from swap. */
		if (object->type == OBJT_SWAP)
			swap_pager_freespace(object, nobjsize, delta);

		/* Free the swap accounted for shm */
		swap_release_by_cred(delta, object->cred);
		object->charge -= delta;
	} else {
		/* Attempt to reserve the swap */
		delta = ptoa(nobjsize - object->size);
		if (!swap_reserve_by_cred(delta, object->cred)) {
			VM_OBJECT_WUNLOCK(object);
			return (ENOMEM);
		}
		object->charge += delta;
	}
	shmfd->shm_size = length;
	mtx_lock(&shm_timestamp_lock);
	vfs_timestamp(&shmfd->shm_ctime);
	shmfd->shm_mtime = shmfd->shm_ctime;
	mtx_unlock(&shm_timestamp_lock);
	object->size = nobjsize;
	VM_OBJECT_WUNLOCK(object);
	return (0);
}

/*
 * shmfd object management including creation and reference counting
 * routines.
 */
static struct shmfd *
shm_alloc(struct ucred *ucred, mode_t mode)
{
	struct shmfd *shmfd;
	int ino;

	shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
	shmfd->shm_size = 0;
	shmfd->shm_uid = ucred->cr_uid;
	shmfd->shm_gid = ucred->cr_gid;
	shmfd->shm_mode = mode;
	shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
	    shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
	KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
	shmfd->shm_object->pg_color = 0;
	VM_OBJECT_WLOCK(shmfd->shm_object);
	vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
	vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
	VM_OBJECT_WUNLOCK(shmfd->shm_object);
	vfs_timestamp(&shmfd->shm_birthtime);
	shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
	    shmfd->shm_birthtime;
	ino = alloc_unr(shm_ino_unr);
	if (ino == -1)
		shmfd->shm_ino = 0;
	else
		shmfd->shm_ino = ino;
	refcount_init(&shmfd->shm_refs, 1);
	mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
	rangelock_init(&shmfd->shm_rl);
#ifdef MAC
	mac_posixshm_init(shmfd);
	mac_posixshm_create(ucred, shmfd);
#endif

	return (shmfd);
}

static struct shmfd *
shm_hold(struct shmfd *shmfd)
{

	refcount_acquire(&shmfd->shm_refs);
	return (shmfd);
}

static void
shm_drop(struct shmfd *shmfd)
{

	if (refcount_release(&shmfd->shm_refs)) {
#ifdef MAC
		mac_posixshm_destroy(shmfd);
#endif
		rangelock_destroy(&shmfd->shm_rl);
		mtx_destroy(&shmfd->shm_mtx);
		vm_object_deallocate(shmfd->shm_object);
		if (shmfd->shm_ino != 0)
			free_unr(shm_ino_unr, shmfd->shm_ino);
		free(shmfd, M_SHMFD);
	}
}

/*
 * Determine if the credentials have sufficient permissions for a
 * specified combination of FREAD and FWRITE.
 */
static int
shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
{
	accmode_t accmode;
	int error;

	accmode = 0;
	if (flags & FREAD)
		accmode |= VREAD;
	if (flags & FWRITE)
		accmode |= VWRITE;
	mtx_lock(&shm_timestamp_lock);
	error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
	    accmode, ucred, NULL);
	mtx_unlock(&shm_timestamp_lock);
	return (error);
}

/*
 * Dictionary management.  We maintain an in-kernel dictionary to map
 * paths to shmfd objects.  We use the FNV hash on the path to store
 * the mappings in a hash table.
 */
static void
shm_init(void *arg)
{

	mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
	sx_init(&shm_dict_lock, "shm dictionary");
	shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
	shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL);
	KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized"));
	shm_dev_ino = devfs_alloc_cdp_inode();
	KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
}
SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);

static struct shmfd *
shm_lookup(char *path, Fnv32_t fnv)
{
	struct shm_mapping *map;

	LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
		if (map->sm_fnv != fnv)
			continue;
		if (strcmp(map->sm_path, path) == 0)
			return (map->sm_shmfd);
	}

	return (NULL);
}

static void
shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
{
	struct shm_mapping *map;

	map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
	map->sm_path = path;
	map->sm_fnv = fnv;
	map->sm_shmfd = shm_hold(shmfd);
	shmfd->shm_path = path;
	LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
}

static int
shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
{
	struct shm_mapping *map;
	int error;

	LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
		if (map->sm_fnv != fnv)
			continue;
		if (strcmp(map->sm_path, path) == 0) {
#ifdef MAC
			error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
			if (error)
				return (error);
#endif
			error = shm_access(map->sm_shmfd, ucred,
			    FREAD | FWRITE);
			if (error)
				return (error);
			map->sm_shmfd->shm_path = NULL;
			LIST_REMOVE(map, sm_link);
			shm_drop(map->sm_shmfd);
			free(map->sm_path, M_SHMFD);
			free(map, M_SHMFD);
			return (0);
		}
	}

	return (ENOENT);
}

/* System calls. */
int
sys_shm_open(struct thread *td, struct shm_open_args *uap)
{
	struct filedesc *fdp;
	struct shmfd *shmfd;
	struct file *fp;
	char *path;
	Fnv32_t fnv;
	mode_t cmode;
	int fd, error;

#ifdef CAPABILITY_MODE
	/*
	 * shm_open(2) is only allowed for anonymous objects.
	 */
	if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON))
		return (ECAPMODE);
#endif

	if ((uap->flags & O_ACCMODE) != O_RDONLY &&
	    (uap->flags & O_ACCMODE) != O_RDWR)
		return (EINVAL);

	if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
		return (EINVAL);

	fdp = td->td_proc->p_fd;
	cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;

	error = falloc(td, &fp, &fd, O_CLOEXEC);
	if (error)
		return (error);

	/* A SHM_ANON path pointer creates an anonymous object. */
	if (uap->path == SHM_ANON) {
		/* A read-only anonymous object is pointless. */
		if ((uap->flags & O_ACCMODE) == O_RDONLY) {
			fdclose(fdp, fp, fd, td);
			fdrop(fp, td);
			return (EINVAL);
		}
		shmfd = shm_alloc(td->td_ucred, cmode);
	} else {
		path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
		error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
#ifdef KTRACE
		if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
			ktrnamei(path);
#endif
		/* Require paths to start with a '/' character. */
		if (error == 0 && path[0] != '/')
			error = EINVAL;
		if (error) {
			fdclose(fdp, fp, fd, td);
			fdrop(fp, td);
			free(path, M_SHMFD);
			return (error);
		}

		fnv = fnv_32_str(path, FNV1_32_INIT);
		sx_xlock(&shm_dict_lock);
		shmfd = shm_lookup(path, fnv);
		if (shmfd == NULL) {
			/* Object does not yet exist, create it if requested. */
			if (uap->flags & O_CREAT) {
#ifdef MAC
				error = mac_posixshm_check_create(td->td_ucred,
				    path);
				if (error == 0) {
#endif
					shmfd = shm_alloc(td->td_ucred, cmode);
					shm_insert(path, fnv, shmfd);
#ifdef MAC
				}
#endif
			} else {
				free(path, M_SHMFD);
				error = ENOENT;
			}
		} else {
			/*
			 * Object already exists, obtain a new
			 * reference if requested and permitted.
			 */
			free(path, M_SHMFD);
			if ((uap->flags & (O_CREAT | O_EXCL)) ==
			    (O_CREAT | O_EXCL))
				error = EEXIST;
			else {
#ifdef MAC
				error = mac_posixshm_check_open(td->td_ucred,
				    shmfd, FFLAGS(uap->flags & O_ACCMODE));
				if (error == 0)
#endif
				error = shm_access(shmfd, td->td_ucred,
				    FFLAGS(uap->flags & O_ACCMODE));
			}

			/*
			 * Truncate the file back to zero length if
			 * O_TRUNC was specified and the object was
			 * opened with read/write.
			 */
			if (error == 0 &&
			    (uap->flags & (O_ACCMODE | O_TRUNC)) ==
			    (O_RDWR | O_TRUNC)) {
#ifdef MAC
				error = mac_posixshm_check_truncate(
					td->td_ucred, fp->f_cred, shmfd);
				if (error == 0)
#endif
					shm_dotruncate(shmfd, 0);
			}
			if (error == 0)
				shm_hold(shmfd);
		}
		sx_xunlock(&shm_dict_lock);

		if (error) {
			fdclose(fdp, fp, fd, td);
			fdrop(fp, td);
			return (error);
		}
	}

	finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);

	td->td_retval[0] = fd;
	fdrop(fp, td);

	return (0);
}

int
sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
{
	char *path;
	Fnv32_t fnv;
	int error;

	path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
	error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
	if (error) {
		free(path, M_TEMP);
		return (error);
	}
#ifdef KTRACE
	if (KTRPOINT(curthread, KTR_NAMEI))
		ktrnamei(path);
#endif
	fnv = fnv_32_str(path, FNV1_32_INIT);
	sx_xlock(&shm_dict_lock);
	error = shm_remove(path, fnv, td->td_ucred);
	sx_xunlock(&shm_dict_lock);
	free(path, M_TEMP);

	return (error);
}

/*
 * mmap() helper to validate mmap() requests against shm object state
 * and give mmap() the vm_object to use for the mapping.
 */
int
shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
    vm_object_t *obj)
{

	/*
	 * XXXRW: This validation is probably insufficient, and subject to
	 * sign errors.  It should be fixed.
	 */
	if (foff >= shmfd->shm_size ||
	    foff + objsize > round_page(shmfd->shm_size))
		return (EINVAL);

	mtx_lock(&shm_timestamp_lock);
	vfs_timestamp(&shmfd->shm_atime);
	mtx_unlock(&shm_timestamp_lock);
	vm_object_reference(shmfd->shm_object);
	*obj = shmfd->shm_object;
	return (0);
}

static int
shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
    struct thread *td)
{
	struct shmfd *shmfd;
	int error;

	error = 0;
	shmfd = fp->f_data;
	mtx_lock(&shm_timestamp_lock);
	/*
	 * SUSv4 says that x bits of permission need not be affected.
	 * Be consistent with our shm_open there.
	 */
#ifdef MAC
	error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
	if (error != 0)
		goto out;
#endif
	error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
	    shmfd->shm_gid, VADMIN, active_cred, NULL);
	if (error != 0)
		goto out;
	shmfd->shm_mode = mode & ACCESSPERMS;
out:
	mtx_unlock(&shm_timestamp_lock);
	return (error);
}

static int
shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
    struct thread *td)
{
	struct shmfd *shmfd;
	int error;

	error = 0;
	shmfd = fp->f_data;
	mtx_lock(&shm_timestamp_lock);
#ifdef MAC
	error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
	if (error != 0)
		goto out;
#endif
	if (uid == (uid_t)-1)
		uid = shmfd->shm_uid;
	if (gid == (gid_t)-1)
                 gid = shmfd->shm_gid;
	if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
	    (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
	    (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
		goto out;
	shmfd->shm_uid = uid;
	shmfd->shm_gid = gid;
out:
	mtx_unlock(&shm_timestamp_lock);
	return (error);
}

/*
 * Helper routines to allow the backing object of a shared memory file
 * descriptor to be mapped in the kernel.
 */
int
shm_map(struct file *fp, size_t size, off_t offset, void **memp)
{
	struct shmfd *shmfd;
	vm_offset_t kva, ofs;
	vm_object_t obj;
	int rv;

	if (fp->f_type != DTYPE_SHM)
		return (EINVAL);
	shmfd = fp->f_data;
	obj = shmfd->shm_object;
	VM_OBJECT_WLOCK(obj);
	/*
	 * XXXRW: This validation is probably insufficient, and subject to
	 * sign errors.  It should be fixed.
	 */
	if (offset >= shmfd->shm_size ||
	    offset + size > round_page(shmfd->shm_size)) {
		VM_OBJECT_WUNLOCK(obj);
		return (EINVAL);
	}

	shmfd->shm_kmappings++;
	vm_object_reference_locked(obj);
	VM_OBJECT_WUNLOCK(obj);

	/* Map the object into the kernel_map and wire it. */
	kva = vm_map_min(kernel_map);
	ofs = offset & PAGE_MASK;
	offset = trunc_page(offset);
	size = round_page(size + ofs);
	rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
	    VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
	    VM_PROT_READ | VM_PROT_WRITE, 0);
	if (rv == KERN_SUCCESS) {
		rv = vm_map_wire(kernel_map, kva, kva + size,
		    VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
		if (rv == KERN_SUCCESS) {
			*memp = (void *)(kva + ofs);
			return (0);
		}
		vm_map_remove(kernel_map, kva, kva + size);
	} else
		vm_object_deallocate(obj);

	/* On failure, drop our mapping reference. */
	VM_OBJECT_WLOCK(obj);
	shmfd->shm_kmappings--;
	VM_OBJECT_WUNLOCK(obj);

	return (vm_mmap_to_errno(rv));
}

/*
 * We require the caller to unmap the entire entry.  This allows us to
 * safely decrement shm_kmappings when a mapping is removed.
 */
int
shm_unmap(struct file *fp, void *mem, size_t size)
{
	struct shmfd *shmfd;
	vm_map_entry_t entry;
	vm_offset_t kva, ofs;
	vm_object_t obj;
	vm_pindex_t pindex;
	vm_prot_t prot;
	boolean_t wired;
	vm_map_t map;
	int rv;

	if (fp->f_type != DTYPE_SHM)
		return (EINVAL);
	shmfd = fp->f_data;
	kva = (vm_offset_t)mem;
	ofs = kva & PAGE_MASK;
	kva = trunc_page(kva);
	size = round_page(size + ofs);
	map = kernel_map;
	rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
	    &obj, &pindex, &prot, &wired);
	if (rv != KERN_SUCCESS)
		return (EINVAL);
	if (entry->start != kva || entry->end != kva + size) {
		vm_map_lookup_done(map, entry);
		return (EINVAL);
	}
	vm_map_lookup_done(map, entry);
	if (obj != shmfd->shm_object)
		return (EINVAL);
	vm_map_remove(map, kva, kva + size);
	VM_OBJECT_WLOCK(obj);
	KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
	shmfd->shm_kmappings--;
	VM_OBJECT_WUNLOCK(obj);
	return (0);
}

void
shm_path(struct shmfd *shmfd, char *path, size_t size)
{

	if (shmfd->shm_path == NULL)
		return;
	sx_slock(&shm_dict_lock);
	if (shmfd->shm_path != NULL)
		strlcpy(path, shmfd->shm_path, size);
	sx_sunlock(&shm_dict_lock);
}
OpenPOWER on IntegriCloud