summaryrefslogtreecommitdiffstats
path: root/ipc/shm.c
blob: dca90489e3b0f7b9cfd189b593eeee1d3c0f197e (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
/*
 * linux/ipc/shm.c
 * Copyright (C) 1992, 1993 Krishna Balasubramanian
 *	 Many improvements/fixes by Bruno Haible.
 * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
 * Fixed the shm swap deallocation (shm_unuse()), August 1998 Andrea Arcangeli.
 *
 * /proc/sysvipc/shm support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
 * BIGMEM support, Andrea Arcangeli <andrea@suse.de>
 * SMP thread shm, Jean-Luc Boyard <jean-luc.boyard@siemens.fr>
 * HIGHMEM support, Ingo Molnar <mingo@redhat.com>
 * Make shmmax, shmall, shmmni sysctl'able, Christoph Rohland <cr@sap.com>
 * Shared /dev/zero support, Kanoj Sarcar <kanoj@sgi.com>
 * Move the mm functionality over to mm/shmem.c, Christoph Rohland <cr@sap.com>
 *
 */

#include <linux/config.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/shmem_fs.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/ptrace.h>
#include <linux/seq_file.h>

#include <asm/uaccess.h>

#include "util.h"

#define shm_flags	shm_perm.mode

static struct file_operations shm_file_operations;
static struct vm_operations_struct shm_vm_ops;

static struct ipc_ids shm_ids;

#define shm_lock(id)	((struct shmid_kernel*)ipc_lock(&shm_ids,id))
#define shm_unlock(shp)	ipc_unlock(&(shp)->shm_perm)
#define shm_get(id)	((struct shmid_kernel*)ipc_get(&shm_ids,id))
#define shm_buildid(id, seq) \
	ipc_buildid(&shm_ids, id, seq)

static int newseg (key_t key, int shmflg, size_t size);
static void shm_open (struct vm_area_struct *shmd);
static void shm_close (struct vm_area_struct *shmd);
#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it);
#endif

size_t	shm_ctlmax = SHMMAX;
size_t 	shm_ctlall = SHMALL;
int 	shm_ctlmni = SHMMNI;

static int shm_tot; /* total number of shared memory pages */

void __init shm_init (void)
{
	ipc_init_ids(&shm_ids, 1);
	ipc_init_proc_interface("sysvipc/shm",
				"       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime\n",
				&shm_ids,
				sysvipc_shm_proc_show);
}

static inline int shm_checkid(struct shmid_kernel *s, int id)
{
	if (ipc_checkid(&shm_ids,&s->shm_perm,id))
		return -EIDRM;
	return 0;
}

static inline struct shmid_kernel *shm_rmid(int id)
{
	return (struct shmid_kernel *)ipc_rmid(&shm_ids,id);
}

static inline int shm_addid(struct shmid_kernel *shp)
{
	return ipc_addid(&shm_ids, &shp->shm_perm, shm_ctlmni);
}



static inline void shm_inc (int id) {
	struct shmid_kernel *shp;

	if(!(shp = shm_lock(id)))
		BUG();
	shp->shm_atim = get_seconds();
	shp->shm_lprid = current->tgid;
	shp->shm_nattch++;
	shm_unlock(shp);
}

/* This is called by fork, once for every shm attach. */
static void shm_open (struct vm_area_struct *shmd)
{
	shm_inc (shmd->vm_file->f_dentry->d_inode->i_ino);
}

/*
 * shm_destroy - free the struct shmid_kernel
 *
 * @shp: struct to free
 *
 * It has to be called with shp and shm_ids.sem locked,
 * but returns with shp unlocked and freed.
 */
static void shm_destroy (struct shmid_kernel *shp)
{
	shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
	shm_rmid (shp->id);
	shm_unlock(shp);
	if (!is_file_hugepages(shp->shm_file))
		shmem_lock(shp->shm_file, 0, shp->mlock_user);
	else
		user_shm_unlock(shp->shm_file->f_dentry->d_inode->i_size,
						shp->mlock_user);
	fput (shp->shm_file);
	security_shm_free(shp);
	ipc_rcu_putref(shp);
}

/*
 * remove the attach descriptor shmd.
 * free memory for segment if it is marked destroyed.
 * The descriptor has already been removed from the current->mm->mmap list
 * and will later be kfree()d.
 */
static void shm_close (struct vm_area_struct *shmd)
{
	struct file * file = shmd->vm_file;
	int id = file->f_dentry->d_inode->i_ino;
	struct shmid_kernel *shp;

	down (&shm_ids.sem);
	/* remove from the list of attaches of the shm segment */
	if(!(shp = shm_lock(id)))
		BUG();
	shp->shm_lprid = current->tgid;
	shp->shm_dtim = get_seconds();
	shp->shm_nattch--;
	if(shp->shm_nattch == 0 &&
	   shp->shm_flags & SHM_DEST)
		shm_destroy (shp);
	else
		shm_unlock(shp);
	up (&shm_ids.sem);
}

static int shm_mmap(struct file * file, struct vm_area_struct * vma)
{
	file_accessed(file);
	vma->vm_ops = &shm_vm_ops;
	shm_inc(file->f_dentry->d_inode->i_ino);
	return 0;
}

static struct file_operations shm_file_operations = {
	.mmap	= shm_mmap
};

static struct vm_operations_struct shm_vm_ops = {
	.open	= shm_open,	/* callback for a new vm-area open */
	.close	= shm_close,	/* callback for when the vm-area is released */
	.nopage	= shmem_nopage,
#if defined(CONFIG_NUMA) && defined(CONFIG_SHMEM)
	.set_policy = shmem_set_policy,
	.get_policy = shmem_get_policy,
#endif
};

static int newseg (key_t key, int shmflg, size_t size)
{
	int error;
	struct shmid_kernel *shp;
	int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT;
	struct file * file;
	char name[13];
	int id;

	if (size < SHMMIN || size > shm_ctlmax)
		return -EINVAL;

	if (shm_tot + numpages >= shm_ctlall)
		return -ENOSPC;

	shp = ipc_rcu_alloc(sizeof(*shp));
	if (!shp)
		return -ENOMEM;

	shp->shm_perm.key = key;
	shp->shm_flags = (shmflg & S_IRWXUGO);
	shp->mlock_user = NULL;

	shp->shm_perm.security = NULL;
	error = security_shm_alloc(shp);
	if (error) {
		ipc_rcu_putref(shp);
		return error;
	}

	if (shmflg & SHM_HUGETLB) {
		/* hugetlb_zero_setup takes care of mlock user accounting */
		file = hugetlb_zero_setup(size);
		shp->mlock_user = current->user;
	} else {
		sprintf (name, "SYSV%08x", key);
		file = shmem_file_setup(name, size, VM_ACCOUNT);
	}
	error = PTR_ERR(file);
	if (IS_ERR(file))
		goto no_file;

	error = -ENOSPC;
	id = shm_addid(shp);
	if(id == -1) 
		goto no_id;

	shp->shm_cprid = current->tgid;
	shp->shm_lprid = 0;
	shp->shm_atim = shp->shm_dtim = 0;
	shp->shm_ctim = get_seconds();
	shp->shm_segsz = size;
	shp->shm_nattch = 0;
	shp->id = shm_buildid(id,shp->shm_perm.seq);
	shp->shm_file = file;
	file->f_dentry->d_inode->i_ino = shp->id;
	if (shmflg & SHM_HUGETLB)
		set_file_hugepages(file);
	else
		file->f_op = &shm_file_operations;
	shm_tot += numpages;
	shm_unlock(shp);
	return shp->id;

no_id:
	fput(file);
no_file:
	security_shm_free(shp);
	ipc_rcu_putref(shp);
	return error;
}

asmlinkage long sys_shmget (key_t key, size_t size, int shmflg)
{
	struct shmid_kernel *shp;
	int err, id = 0;

	down(&shm_ids.sem);
	if (key == IPC_PRIVATE) {
		err = newseg(key, shmflg, size);
	} else if ((id = ipc_findkey(&shm_ids, key)) == -1) {
		if (!(shmflg & IPC_CREAT))
			err = -ENOENT;
		else
			err = newseg(key, shmflg, size);
	} else if ((shmflg & IPC_CREAT) && (shmflg & IPC_EXCL)) {
		err = -EEXIST;
	} else {
		shp = shm_lock(id);
		if(shp==NULL)
			BUG();
		if (shp->shm_segsz < size)
			err = -EINVAL;
		else if (ipcperms(&shp->shm_perm, shmflg))
			err = -EACCES;
		else {
			int shmid = shm_buildid(id, shp->shm_perm.seq);
			err = security_shm_associate(shp, shmflg);
			if (!err)
				err = shmid;
		}
		shm_unlock(shp);
	}
	up(&shm_ids.sem);

	return err;
}

static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_ds *in, int version)
{
	switch(version) {
	case IPC_64:
		return copy_to_user(buf, in, sizeof(*in));
	case IPC_OLD:
	    {
		struct shmid_ds out;

		ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
		out.shm_segsz	= in->shm_segsz;
		out.shm_atime	= in->shm_atime;
		out.shm_dtime	= in->shm_dtime;
		out.shm_ctime	= in->shm_ctime;
		out.shm_cpid	= in->shm_cpid;
		out.shm_lpid	= in->shm_lpid;
		out.shm_nattch	= in->shm_nattch;

		return copy_to_user(buf, &out, sizeof(out));
	    }
	default:
		return -EINVAL;
	}
}

struct shm_setbuf {
	uid_t	uid;
	gid_t	gid;
	mode_t	mode;
};	

static inline unsigned long copy_shmid_from_user(struct shm_setbuf *out, void __user *buf, int version)
{
	switch(version) {
	case IPC_64:
	    {
		struct shmid64_ds tbuf;

		if (copy_from_user(&tbuf, buf, sizeof(tbuf)))
			return -EFAULT;

		out->uid	= tbuf.shm_perm.uid;
		out->gid	= tbuf.shm_perm.gid;
		out->mode	= tbuf.shm_flags;

		return 0;
	    }
	case IPC_OLD:
	    {
		struct shmid_ds tbuf_old;

		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
			return -EFAULT;

		out->uid	= tbuf_old.shm_perm.uid;
		out->gid	= tbuf_old.shm_perm.gid;
		out->mode	= tbuf_old.shm_flags;

		return 0;
	    }
	default:
		return -EINVAL;
	}
}

static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminfo64 *in, int version)
{
	switch(version) {
	case IPC_64:
		return copy_to_user(buf, in, sizeof(*in));
	case IPC_OLD:
	    {
		struct shminfo out;

		if(in->shmmax > INT_MAX)
			out.shmmax = INT_MAX;
		else
			out.shmmax = (int)in->shmmax;

		out.shmmin	= in->shmmin;
		out.shmmni	= in->shmmni;
		out.shmseg	= in->shmseg;
		out.shmall	= in->shmall; 

		return copy_to_user(buf, &out, sizeof(out));
	    }
	default:
		return -EINVAL;
	}
}

static void shm_get_stat(unsigned long *rss, unsigned long *swp) 
{
	int i;

	*rss = 0;
	*swp = 0;

	for (i = 0; i <= shm_ids.max_id; i++) {
		struct shmid_kernel *shp;
		struct inode *inode;

		shp = shm_get(i);
		if(!shp)
			continue;

		inode = shp->shm_file->f_dentry->d_inode;

		if (is_file_hugepages(shp->shm_file)) {
			struct address_space *mapping = inode->i_mapping;
			*rss += (HPAGE_SIZE/PAGE_SIZE)*mapping->nrpages;
		} else {
			struct shmem_inode_info *info = SHMEM_I(inode);
			spin_lock(&info->lock);
			*rss += inode->i_mapping->nrpages;
			*swp += info->swapped;
			spin_unlock(&info->lock);
		}
	}
}

asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf)
{
	struct shm_setbuf setbuf;
	struct shmid_kernel *shp;
	int err, version;

	if (cmd < 0 || shmid < 0) {
		err = -EINVAL;
		goto out;
	}

	version = ipc_parse_version(&cmd);

	switch (cmd) { /* replace with proc interface ? */
	case IPC_INFO:
	{
		struct shminfo64 shminfo;

		err = security_shm_shmctl(NULL, cmd);
		if (err)
			return err;

		memset(&shminfo,0,sizeof(shminfo));
		shminfo.shmmni = shminfo.shmseg = shm_ctlmni;
		shminfo.shmmax = shm_ctlmax;
		shminfo.shmall = shm_ctlall;

		shminfo.shmmin = SHMMIN;
		if(copy_shminfo_to_user (buf, &shminfo, version))
			return -EFAULT;
		/* reading a integer is always atomic */
		err= shm_ids.max_id;
		if(err<0)
			err = 0;
		goto out;
	}
	case SHM_INFO:
	{
		struct shm_info shm_info;

		err = security_shm_shmctl(NULL, cmd);
		if (err)
			return err;

		memset(&shm_info,0,sizeof(shm_info));
		down(&shm_ids.sem);
		shm_info.used_ids = shm_ids.in_use;
		shm_get_stat (&shm_info.shm_rss, &shm_info.shm_swp);
		shm_info.shm_tot = shm_tot;
		shm_info.swap_attempts = 0;
		shm_info.swap_successes = 0;
		err = shm_ids.max_id;
		up(&shm_ids.sem);
		if(copy_to_user (buf, &shm_info, sizeof(shm_info))) {
			err = -EFAULT;
			goto out;
		}

		err = err < 0 ? 0 : err;
		goto out;
	}
	case SHM_STAT:
	case IPC_STAT:
	{
		struct shmid64_ds tbuf;
		int result;
		memset(&tbuf, 0, sizeof(tbuf));
		shp = shm_lock(shmid);
		if(shp==NULL) {
			err = -EINVAL;
			goto out;
		} else if(cmd==SHM_STAT) {
			err = -EINVAL;
			if (shmid > shm_ids.max_id)
				goto out_unlock;
			result = shm_buildid(shmid, shp->shm_perm.seq);
		} else {
			err = shm_checkid(shp,shmid);
			if(err)
				goto out_unlock;
			result = 0;
		}
		err=-EACCES;
		if (ipcperms (&shp->shm_perm, S_IRUGO))
			goto out_unlock;
		err = security_shm_shmctl(shp, cmd);
		if (err)
			goto out_unlock;
		kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
		tbuf.shm_segsz	= shp->shm_segsz;
		tbuf.shm_atime	= shp->shm_atim;
		tbuf.shm_dtime	= shp->shm_dtim;
		tbuf.shm_ctime	= shp->shm_ctim;
		tbuf.shm_cpid	= shp->shm_cprid;
		tbuf.shm_lpid	= shp->shm_lprid;
		if (!is_file_hugepages(shp->shm_file))
			tbuf.shm_nattch	= shp->shm_nattch;
		else
			tbuf.shm_nattch = file_count(shp->shm_file) - 1;
		shm_unlock(shp);
		if(copy_shmid_to_user (buf, &tbuf, version))
			err = -EFAULT;
		else
			err = result;
		goto out;
	}
	case SHM_LOCK:
	case SHM_UNLOCK:
	{
		shp = shm_lock(shmid);
		if(shp==NULL) {
			err = -EINVAL;
			goto out;
		}
		err = shm_checkid(shp,shmid);
		if(err)
			goto out_unlock;

		if (!capable(CAP_IPC_LOCK)) {
			err = -EPERM;
			if (current->euid != shp->shm_perm.uid &&
			    current->euid != shp->shm_perm.cuid)
				goto out_unlock;
			if (cmd == SHM_LOCK &&
			    !current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur)
				goto out_unlock;
		}

		err = security_shm_shmctl(shp, cmd);
		if (err)
			goto out_unlock;
		
		if(cmd==SHM_LOCK) {
			struct user_struct * user = current->user;
			if (!is_file_hugepages(shp->shm_file)) {
				err = shmem_lock(shp->shm_file, 1, user);
				if (!err) {
					shp->shm_flags |= SHM_LOCKED;
					shp->mlock_user = user;
				}
			}
		} else if (!is_file_hugepages(shp->shm_file)) {
			shmem_lock(shp->shm_file, 0, shp->mlock_user);
			shp->shm_flags &= ~SHM_LOCKED;
			shp->mlock_user = NULL;
		}
		shm_unlock(shp);
		goto out;
	}
	case IPC_RMID:
	{
		/*
		 *	We cannot simply remove the file. The SVID states
		 *	that the block remains until the last person
		 *	detaches from it, then is deleted. A shmat() on
		 *	an RMID segment is legal in older Linux and if 
		 *	we change it apps break...
		 *
		 *	Instead we set a destroyed flag, and then blow
		 *	the name away when the usage hits zero.
		 */
		down(&shm_ids.sem);
		shp = shm_lock(shmid);
		err = -EINVAL;
		if (shp == NULL) 
			goto out_up;
		err = shm_checkid(shp, shmid);
		if(err)
			goto out_unlock_up;

		if (current->euid != shp->shm_perm.uid &&
		    current->euid != shp->shm_perm.cuid && 
		    !capable(CAP_SYS_ADMIN)) {
			err=-EPERM;
			goto out_unlock_up;
		}

		err = security_shm_shmctl(shp, cmd);
		if (err)
			goto out_unlock_up;

		if (shp->shm_nattch){
			shp->shm_flags |= SHM_DEST;
			/* Do not find it any more */
			shp->shm_perm.key = IPC_PRIVATE;
			shm_unlock(shp);
		} else
			shm_destroy (shp);
		up(&shm_ids.sem);
		goto out;
	}

	case IPC_SET:
	{
		if (copy_shmid_from_user (&setbuf, buf, version)) {
			err = -EFAULT;
			goto out;
		}
		if ((err = audit_ipc_perms(0, setbuf.uid, setbuf.gid, setbuf.mode)))
			return err;
		down(&shm_ids.sem);
		shp = shm_lock(shmid);
		err=-EINVAL;
		if(shp==NULL)
			goto out_up;
		err = shm_checkid(shp,shmid);
		if(err)
			goto out_unlock_up;
		err=-EPERM;
		if (current->euid != shp->shm_perm.uid &&
		    current->euid != shp->shm_perm.cuid && 
		    !capable(CAP_SYS_ADMIN)) {
			goto out_unlock_up;
		}

		err = security_shm_shmctl(shp, cmd);
		if (err)
			goto out_unlock_up;
		
		shp->shm_perm.uid = setbuf.uid;
		shp->shm_perm.gid = setbuf.gid;
		shp->shm_flags = (shp->shm_flags & ~S_IRWXUGO)
			| (setbuf.mode & S_IRWXUGO);
		shp->shm_ctim = get_seconds();
		break;
	}

	default:
		err = -EINVAL;
		goto out;
	}

	err = 0;
out_unlock_up:
	shm_unlock(shp);
out_up:
	up(&shm_ids.sem);
	goto out;
out_unlock:
	shm_unlock(shp);
out:
	return err;
}

/*
 * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
 *
 * NOTE! Despite the name, this is NOT a direct system call entrypoint. The
 * "raddr" thing points to kernel space, and there has to be a wrapper around
 * this.
 */
long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
{
	struct shmid_kernel *shp;
	unsigned long addr;
	unsigned long size;
	struct file * file;
	int    err;
	unsigned long flags;
	unsigned long prot;
	unsigned long o_flags;
	int acc_mode;
	void *user_addr;

	if (shmid < 0) {
		err = -EINVAL;
		goto out;
	} else if ((addr = (ulong)shmaddr)) {
		if (addr & (SHMLBA-1)) {
			if (shmflg & SHM_RND)
				addr &= ~(SHMLBA-1);	   /* round down */
			else
#ifndef __ARCH_FORCE_SHMLBA
				if (addr & ~PAGE_MASK)
#endif
					return -EINVAL;
		}
		flags = MAP_SHARED | MAP_FIXED;
	} else {
		if ((shmflg & SHM_REMAP))
			return -EINVAL;

		flags = MAP_SHARED;
	}

	if (shmflg & SHM_RDONLY) {
		prot = PROT_READ;
		o_flags = O_RDONLY;
		acc_mode = S_IRUGO;
	} else {
		prot = PROT_READ | PROT_WRITE;
		o_flags = O_RDWR;
		acc_mode = S_IRUGO | S_IWUGO;
	}
	if (shmflg & SHM_EXEC) {
		prot |= PROT_EXEC;
		acc_mode |= S_IXUGO;
	}

	/*
	 * We cannot rely on the fs check since SYSV IPC does have an
	 * additional creator id...
	 */
	shp = shm_lock(shmid);
	if(shp == NULL) {
		err = -EINVAL;
		goto out;
	}
	err = shm_checkid(shp,shmid);
	if (err) {
		shm_unlock(shp);
		goto out;
	}
	if (ipcperms(&shp->shm_perm, acc_mode)) {
		shm_unlock(shp);
		err = -EACCES;
		goto out;
	}

	err = security_shm_shmat(shp, shmaddr, shmflg);
	if (err) {
		shm_unlock(shp);
		return err;
	}
		
	file = shp->shm_file;
	size = i_size_read(file->f_dentry->d_inode);
	shp->shm_nattch++;
	shm_unlock(shp);

	down_write(&current->mm->mmap_sem);
	if (addr && !(shmflg & SHM_REMAP)) {
		user_addr = ERR_PTR(-EINVAL);
		if (find_vma_intersection(current->mm, addr, addr + size))
			goto invalid;
		/*
		 * If shm segment goes below stack, make sure there is some
		 * space left for the stack to grow (at least 4 pages).
		 */
		if (addr < current->mm->start_stack &&
		    addr > current->mm->start_stack - size - PAGE_SIZE * 5)
			goto invalid;
	}
		
	user_addr = (void*) do_mmap (file, addr, size, prot, flags, 0);

invalid:
	up_write(&current->mm->mmap_sem);

	down (&shm_ids.sem);
	if(!(shp = shm_lock(shmid)))
		BUG();
	shp->shm_nattch--;
	if(shp->shm_nattch == 0 &&
	   shp->shm_flags & SHM_DEST)
		shm_destroy (shp);
	else
		shm_unlock(shp);
	up (&shm_ids.sem);

	*raddr = (unsigned long) user_addr;
	err = 0;
	if (IS_ERR(user_addr))
		err = PTR_ERR(user_addr);
out:
	return err;
}

asmlinkage long sys_shmat(int shmid, char __user *shmaddr, int shmflg)
{
	unsigned long ret;
	long err;

	err = do_shmat(shmid, shmaddr, shmflg, &ret);
	if (err)
		return err;
	force_successful_syscall_return();
	return (long)ret;
}

/*
 * detach and kill segment if marked destroyed.
 * The work is done in shm_close.
 */
asmlinkage long sys_shmdt(char __user *shmaddr)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma, *next;
	unsigned long addr = (unsigned long)shmaddr;
	loff_t size = 0;
	int retval = -EINVAL;

	down_write(&mm->mmap_sem);

	/*
	 * This function tries to be smart and unmap shm segments that
	 * were modified by partial mlock or munmap calls:
	 * - It first determines the size of the shm segment that should be
	 *   unmapped: It searches for a vma that is backed by shm and that
	 *   started at address shmaddr. It records it's size and then unmaps
	 *   it.
	 * - Then it unmaps all shm vmas that started at shmaddr and that
	 *   are within the initially determined size.
	 * Errors from do_munmap are ignored: the function only fails if
	 * it's called with invalid parameters or if it's called to unmap
	 * a part of a vma. Both calls in this function are for full vmas,
	 * the parameters are directly copied from the vma itself and always
	 * valid - therefore do_munmap cannot fail. (famous last words?)
	 */
	/*
	 * If it had been mremap()'d, the starting address would not
	 * match the usual checks anyway. So assume all vma's are
	 * above the starting address given.
	 */
	vma = find_vma(mm, addr);

	while (vma) {
		next = vma->vm_next;

		/*
		 * Check if the starting address would match, i.e. it's
		 * a fragment created by mprotect() and/or munmap(), or it
		 * otherwise it starts at this address with no hassles.
		 */
		if ((vma->vm_ops == &shm_vm_ops || is_vm_hugetlb_page(vma)) &&
			(vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) {


			size = vma->vm_file->f_dentry->d_inode->i_size;
			do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
			/*
			 * We discovered the size of the shm segment, so
			 * break out of here and fall through to the next
			 * loop that uses the size information to stop
			 * searching for matching vma's.
			 */
			retval = 0;
			vma = next;
			break;
		}
		vma = next;
	}

	/*
	 * We need look no further than the maximum address a fragment
	 * could possibly have landed at. Also cast things to loff_t to
	 * prevent overflows and make comparisions vs. equal-width types.
	 */
	while (vma && (loff_t)(vma->vm_end - addr) <= size) {
		next = vma->vm_next;

		/* finding a matching vma now does not alter retval */
		if ((vma->vm_ops == &shm_vm_ops || is_vm_hugetlb_page(vma)) &&
			(vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff)

			do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
		vma = next;
	}

	up_write(&mm->mmap_sem);
	return retval;
}

#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it)
{
	struct shmid_kernel *shp = it;
	char *format;

#define SMALL_STRING "%10d %10d  %4o %10u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
#define BIG_STRING   "%10d %10d  %4o %21u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"

	if (sizeof(size_t) <= sizeof(int))
		format = SMALL_STRING;
	else
		format = BIG_STRING;
	return seq_printf(s, format,
			  shp->shm_perm.key,
			  shp->id,
			  shp->shm_flags,
			  shp->shm_segsz,
			  shp->shm_cprid,
			  shp->shm_lprid,
			  is_file_hugepages(shp->shm_file) ? (file_count(shp->shm_file) - 1) : shp->shm_nattch,
			  shp->shm_perm.uid,
			  shp->shm_perm.gid,
			  shp->shm_perm.cuid,
			  shp->shm_perm.cgid,
			  shp->shm_atim,
			  shp->shm_dtim,
			  shp->shm_ctim);
}
#endif