summaryrefslogtreecommitdiffstats
path: root/mm/nommu.c
blob: 00ffa974c90cc8126ee296847670c14bbd789c7f (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
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
/*
 *  linux/mm/nommu.c
 *
 *  Replacement code for mm functions to support CPU's that don't
 *  have any form of memory management unit (thus no virtual memory).
 *
 *  See Documentation/nommu-mmap.txt
 *
 *  Copyright (c) 2004-2005 David Howells <dhowells@redhat.com>
 *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
 *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
 *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
 */

#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/file.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/ptrace.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/mount.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/syscalls.h>

#include <asm/uaccess.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>

void *high_memory;
struct page *mem_map;
unsigned long max_mapnr;
unsigned long num_physpages;
unsigned long askedalloc, realalloc;
atomic_t vm_committed_space = ATOMIC_INIT(0);
int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
int sysctl_overcommit_ratio = 50; /* default is 50% */
int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
int heap_stack_gap = 0;

EXPORT_SYMBOL(mem_map);
EXPORT_SYMBOL(__vm_enough_memory);

/* list of shareable VMAs */
struct rb_root nommu_vma_tree = RB_ROOT;
DECLARE_RWSEM(nommu_vma_sem);

struct vm_operations_struct generic_file_vm_ops = {
};

EXPORT_SYMBOL(vfree);
EXPORT_SYMBOL(vmalloc_to_page);
EXPORT_SYMBOL(vmalloc_32);
EXPORT_SYMBOL(vmap);
EXPORT_SYMBOL(vunmap);

/*
 * Handle all mappings that got truncated by a "truncate()"
 * system call.
 *
 * NOTE! We have to be ready to update the memory sharing
 * between the file and the memory map for a potential last
 * incomplete page.  Ugly, but necessary.
 */
int vmtruncate(struct inode *inode, loff_t offset)
{
	struct address_space *mapping = inode->i_mapping;
	unsigned long limit;

	if (inode->i_size < offset)
		goto do_expand;
	i_size_write(inode, offset);

	truncate_inode_pages(mapping, offset);
	goto out_truncate;

do_expand:
	limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
	if (limit != RLIM_INFINITY && offset > limit)
		goto out_sig;
	if (offset > inode->i_sb->s_maxbytes)
		goto out;
	i_size_write(inode, offset);

out_truncate:
	if (inode->i_op && inode->i_op->truncate)
		inode->i_op->truncate(inode);
	return 0;
out_sig:
	send_sig(SIGXFSZ, current, 0);
out:
	return -EFBIG;
}

EXPORT_SYMBOL(vmtruncate);

/*
 * Return the total memory allocated for this pointer, not
 * just what the caller asked for.
 *
 * Doesn't have to be accurate, i.e. may have races.
 */
unsigned int kobjsize(const void *objp)
{
	struct page *page;

	if (!objp || !((page = virt_to_page(objp))))
		return 0;

	if (PageSlab(page))
		return ksize(objp);

	BUG_ON(page->index < 0);
	BUG_ON(page->index >= MAX_ORDER);

	return (PAGE_SIZE << page->index);
}

/*
 * The nommu dodgy version :-)
 */
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
	unsigned long start, int len, int write, int force,
	struct page **pages, struct vm_area_struct **vmas)
{
	int i;
	static struct vm_area_struct dummy_vma;

	for (i = 0; i < len; i++) {
		if (pages) {
			pages[i] = virt_to_page(start);
			if (pages[i])
				page_cache_get(pages[i]);
		}
		if (vmas)
			vmas[i] = &dummy_vma;
		start += PAGE_SIZE;
	}
	return(i);
}

EXPORT_SYMBOL(get_user_pages);

DEFINE_RWLOCK(vmlist_lock);
struct vm_struct *vmlist;

void vfree(void *addr)
{
	kfree(addr);
}

void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
{
	/*
	 * kmalloc doesn't like __GFP_HIGHMEM for some reason
	 */
	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
}

struct page * vmalloc_to_page(void *addr)
{
	return virt_to_page(addr);
}

unsigned long vmalloc_to_pfn(void *addr)
{
	return page_to_pfn(virt_to_page(addr));
}


long vread(char *buf, char *addr, unsigned long count)
{
	memcpy(buf, addr, count);
	return count;
}

long vwrite(char *buf, char *addr, unsigned long count)
{
	/* Don't allow overflow */
	if ((unsigned long) addr + count < count)
		count = -(unsigned long) addr;

	memcpy(addr, buf, count);
	return(count);
}

/*
 *	vmalloc  -  allocate virtually continguos memory
 *
 *	@size:		allocation size
 *
 *	Allocate enough pages to cover @size from the page level
 *	allocator and map them into continguos kernel virtual space.
 *
 *	For tight cotrol over page level allocator and protection flags
 *	use __vmalloc() instead.
 */
void *vmalloc(unsigned long size)
{
       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
}
EXPORT_SYMBOL(vmalloc);

void *vmalloc_node(unsigned long size, int node)
{
	return vmalloc(size);
}
EXPORT_SYMBOL(vmalloc_node);

/*
 *	vmalloc_32  -  allocate virtually continguos memory (32bit addressable)
 *
 *	@size:		allocation size
 *
 *	Allocate enough 32bit PA addressable pages to cover @size from the
 *	page level allocator and map them into continguos kernel virtual space.
 */
void *vmalloc_32(unsigned long size)
{
	return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
}

void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
{
	BUG();
	return NULL;
}

void vunmap(void *addr)
{
	BUG();
}

/*
 *  sys_brk() for the most part doesn't need the global kernel
 *  lock, except when an application is doing something nasty
 *  like trying to un-brk an area that has already been mapped
 *  to a regular file.  in this case, the unmapping will need
 *  to invoke file system routines that need the global lock.
 */
asmlinkage unsigned long sys_brk(unsigned long brk)
{
	struct mm_struct *mm = current->mm;

	if (brk < mm->start_brk || brk > mm->context.end_brk)
		return mm->brk;

	if (mm->brk == brk)
		return mm->brk;

	/*
	 * Always allow shrinking brk
	 */
	if (brk <= mm->brk) {
		mm->brk = brk;
		return brk;
	}

	/*
	 * Ok, looks good - let it rip.
	 */
	return mm->brk = brk;
}

#ifdef DEBUG
static void show_process_blocks(void)
{
	struct vm_list_struct *vml;

	printk("Process blocks %d:", current->pid);

	for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
		printk(" %p: %p", vml, vml->vma);
		if (vml->vma)
			printk(" (%d @%lx #%d)",
			       kobjsize((void *) vml->vma->vm_start),
			       vml->vma->vm_start,
			       atomic_read(&vml->vma->vm_usage));
		printk(vml->next ? " ->" : ".\n");
	}
}
#endif /* DEBUG */

static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
{
	struct vm_area_struct *vma;
	struct rb_node *n = nommu_vma_tree.rb_node;

	while (n) {
		vma = rb_entry(n, struct vm_area_struct, vm_rb);

		if (start < vma->vm_start)
			n = n->rb_left;
		else if (start > vma->vm_start)
			n = n->rb_right;
		else
			return vma;
	}

	return NULL;
}

static void add_nommu_vma(struct vm_area_struct *vma)
{
	struct vm_area_struct *pvma;
	struct address_space *mapping;
	struct rb_node **p = &nommu_vma_tree.rb_node;
	struct rb_node *parent = NULL;

	/* add the VMA to the mapping */
	if (vma->vm_file) {
		mapping = vma->vm_file->f_mapping;

		flush_dcache_mmap_lock(mapping);
		vma_prio_tree_insert(vma, &mapping->i_mmap);
		flush_dcache_mmap_unlock(mapping);
	}

	/* add the VMA to the master list */
	while (*p) {
		parent = *p;
		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);

		if (vma->vm_start < pvma->vm_start) {
			p = &(*p)->rb_left;
		}
		else if (vma->vm_start > pvma->vm_start) {
			p = &(*p)->rb_right;
		}
		else {
			/* mappings are at the same address - this can only
			 * happen for shared-mem chardevs and shared file
			 * mappings backed by ramfs/tmpfs */
			BUG_ON(!(pvma->vm_flags & VM_SHARED));

			if (vma < pvma)
				p = &(*p)->rb_left;
			else if (vma > pvma)
				p = &(*p)->rb_right;
			else
				BUG();
		}
	}

	rb_link_node(&vma->vm_rb, parent, p);
	rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
}

static void delete_nommu_vma(struct vm_area_struct *vma)
{
	struct address_space *mapping;

	/* remove the VMA from the mapping */
	if (vma->vm_file) {
		mapping = vma->vm_file->f_mapping;

		flush_dcache_mmap_lock(mapping);
		vma_prio_tree_remove(vma, &mapping->i_mmap);
		flush_dcache_mmap_unlock(mapping);
	}

	/* remove from the master list */
	rb_erase(&vma->vm_rb, &nommu_vma_tree);
}

/*
 * determine whether a mapping should be permitted and, if so, what sort of
 * mapping we're capable of supporting
 */
static int validate_mmap_request(struct file *file,
				 unsigned long addr,
				 unsigned long len,
				 unsigned long prot,
				 unsigned long flags,
				 unsigned long pgoff,
				 unsigned long *_capabilities)
{
	unsigned long capabilities;
	unsigned long reqprot = prot;
	int ret;

	/* do the simple checks first */
	if (flags & MAP_FIXED || addr) {
		printk(KERN_DEBUG
		       "%d: Can't do fixed-address/overlay mmap of RAM\n",
		       current->pid);
		return -EINVAL;
	}

	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
	    (flags & MAP_TYPE) != MAP_SHARED)
		return -EINVAL;

	if (PAGE_ALIGN(len) == 0)
		return addr;

	if (len > TASK_SIZE)
		return -EINVAL;

	/* offset overflow? */
	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
		return -EINVAL;

	if (file) {
		/* validate file mapping requests */
		struct address_space *mapping;

		/* files must support mmap */
		if (!file->f_op || !file->f_op->mmap)
			return -ENODEV;

		/* work out if what we've got could possibly be shared
		 * - we support chardevs that provide their own "memory"
		 * - we support files/blockdevs that are memory backed
		 */
		mapping = file->f_mapping;
		if (!mapping)
			mapping = file->f_dentry->d_inode->i_mapping;

		capabilities = 0;
		if (mapping && mapping->backing_dev_info)
			capabilities = mapping->backing_dev_info->capabilities;

		if (!capabilities) {
			/* no explicit capabilities set, so assume some
			 * defaults */
			switch (file->f_dentry->d_inode->i_mode & S_IFMT) {
			case S_IFREG:
			case S_IFBLK:
				capabilities = BDI_CAP_MAP_COPY;
				break;

			case S_IFCHR:
				capabilities =
					BDI_CAP_MAP_DIRECT |
					BDI_CAP_READ_MAP |
					BDI_CAP_WRITE_MAP;
				break;

			default:
				return -EINVAL;
			}
		}

		/* eliminate any capabilities that we can't support on this
		 * device */
		if (!file->f_op->get_unmapped_area)
			capabilities &= ~BDI_CAP_MAP_DIRECT;
		if (!file->f_op->read)
			capabilities &= ~BDI_CAP_MAP_COPY;

		if (flags & MAP_SHARED) {
			/* do checks for writing, appending and locking */
			if ((prot & PROT_WRITE) &&
			    !(file->f_mode & FMODE_WRITE))
				return -EACCES;

			if (IS_APPEND(file->f_dentry->d_inode) &&
			    (file->f_mode & FMODE_WRITE))
				return -EACCES;

			if (locks_verify_locked(file->f_dentry->d_inode))
				return -EAGAIN;

			if (!(capabilities & BDI_CAP_MAP_DIRECT))
				return -ENODEV;

			if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
			    ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
			    ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
			    ) {
				printk("MAP_SHARED not completely supported on !MMU\n");
				return -EINVAL;
			}

			/* we mustn't privatise shared mappings */
			capabilities &= ~BDI_CAP_MAP_COPY;
		}
		else {
			/* we're going to read the file into private memory we
			 * allocate */
			if (!(capabilities & BDI_CAP_MAP_COPY))
				return -ENODEV;

			/* we don't permit a private writable mapping to be
			 * shared with the backing device */
			if (prot & PROT_WRITE)
				capabilities &= ~BDI_CAP_MAP_DIRECT;
		}

		/* handle executable mappings and implied executable
		 * mappings */
		if (file->f_vfsmnt->mnt_flags & MNT_NOEXEC) {
			if (prot & PROT_EXEC)
				return -EPERM;
		}
		else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
			/* handle implication of PROT_EXEC by PROT_READ */
			if (current->personality & READ_IMPLIES_EXEC) {
				if (capabilities & BDI_CAP_EXEC_MAP)
					prot |= PROT_EXEC;
			}
		}
		else if ((prot & PROT_READ) &&
			 (prot & PROT_EXEC) &&
			 !(capabilities & BDI_CAP_EXEC_MAP)
			 ) {
			/* backing file is not executable, try to copy */
			capabilities &= ~BDI_CAP_MAP_DIRECT;
		}
	}
	else {
		/* anonymous mappings are always memory backed and can be
		 * privately mapped
		 */
		capabilities = BDI_CAP_MAP_COPY;

		/* handle PROT_EXEC implication by PROT_READ */
		if ((prot & PROT_READ) &&
		    (current->personality & READ_IMPLIES_EXEC))
			prot |= PROT_EXEC;
	}

	/* allow the security API to have its say */
	ret = security_file_mmap(file, reqprot, prot, flags);
	if (ret < 0)
		return ret;

	/* looks okay */
	*_capabilities = capabilities;
	return 0;
}

/*
 * we've determined that we can make the mapping, now translate what we
 * now know into VMA flags
 */
static unsigned long determine_vm_flags(struct file *file,
					unsigned long prot,
					unsigned long flags,
					unsigned long capabilities)
{
	unsigned long vm_flags;

	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
	vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
	/* vm_flags |= mm->def_flags; */

	if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
		/* attempt to share read-only copies of mapped file chunks */
		if (file && !(prot & PROT_WRITE))
			vm_flags |= VM_MAYSHARE;
	}
	else {
		/* overlay a shareable mapping on the backing device or inode
		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
		 * romfs/cramfs */
		if (flags & MAP_SHARED)
			vm_flags |= VM_MAYSHARE | VM_SHARED;
		else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
			vm_flags |= VM_MAYSHARE;
	}

	/* refuse to let anyone share private mappings with this process if
	 * it's being traced - otherwise breakpoints set in it may interfere
	 * with another untraced process
	 */
	if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
		vm_flags &= ~VM_MAYSHARE;

	return vm_flags;
}

/*
 * set up a shared mapping on a file
 */
static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
{
	int ret;

	ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
	if (ret != -ENOSYS)
		return ret;

	/* getting an ENOSYS error indicates that direct mmap isn't
	 * possible (as opposed to tried but failed) so we'll fall
	 * through to making a private copy of the data and mapping
	 * that if we can */
	return -ENODEV;
}

/*
 * set up a private mapping or an anonymous shared mapping
 */
static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
{
	void *base;
	int ret;

	/* invoke the file's mapping function so that it can keep track of
	 * shared mappings on devices or memory
	 * - VM_MAYSHARE will be set if it may attempt to share
	 */
	if (vma->vm_file) {
		ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
		if (ret != -ENOSYS) {
			/* shouldn't return success if we're not sharing */
			BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
			return ret; /* success or a real error */
		}

		/* getting an ENOSYS error indicates that direct mmap isn't
		 * possible (as opposed to tried but failed) so we'll try to
		 * make a private copy of the data and map that instead */
	}

	/* allocate some memory to hold the mapping
	 * - note that this may not return a page-aligned address if the object
	 *   we're allocating is smaller than a page
	 */
	base = kmalloc(len, GFP_KERNEL|__GFP_COMP);
	if (!base)
		goto enomem;

	vma->vm_start = (unsigned long) base;
	vma->vm_end = vma->vm_start + len;
	vma->vm_flags |= VM_MAPPED_COPY;

#ifdef WARN_ON_SLACK
	if (len + WARN_ON_SLACK <= kobjsize(result))
		printk("Allocation of %lu bytes from process %d has %lu bytes of slack\n",
		       len, current->pid, kobjsize(result) - len);
#endif

	if (vma->vm_file) {
		/* read the contents of a file into the copy */
		mm_segment_t old_fs;
		loff_t fpos;

		fpos = vma->vm_pgoff;
		fpos <<= PAGE_SHIFT;

		old_fs = get_fs();
		set_fs(KERNEL_DS);
		ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
		set_fs(old_fs);

		if (ret < 0)
			goto error_free;

		/* clear the last little bit */
		if (ret < len)
			memset(base + ret, 0, len - ret);

	} else {
		/* if it's an anonymous mapping, then just clear it */
		memset(base, 0, len);
	}

	return 0;

error_free:
	kfree(base);
	vma->vm_start = 0;
	return ret;

enomem:
	printk("Allocation of length %lu from process %d failed\n",
	       len, current->pid);
	show_free_areas();
	return -ENOMEM;
}

/*
 * handle mapping creation for uClinux
 */
unsigned long do_mmap_pgoff(struct file *file,
			    unsigned long addr,
			    unsigned long len,
			    unsigned long prot,
			    unsigned long flags,
			    unsigned long pgoff)
{
	struct vm_list_struct *vml = NULL;
	struct vm_area_struct *vma = NULL;
	struct rb_node *rb;
	unsigned long capabilities, vm_flags;
	void *result;
	int ret;

	/* decide whether we should attempt the mapping, and if so what sort of
	 * mapping */
	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
				    &capabilities);
	if (ret < 0)
		return ret;

	/* we've determined that we can make the mapping, now translate what we
	 * now know into VMA flags */
	vm_flags = determine_vm_flags(file, prot, flags, capabilities);

	/* we're going to need to record the mapping if it works */
	vml = kmalloc(sizeof(struct vm_list_struct), GFP_KERNEL);
	if (!vml)
		goto error_getting_vml;
	memset(vml, 0, sizeof(*vml));

	down_write(&nommu_vma_sem);

	/* if we want to share, we need to check for VMAs created by other
	 * mmap() calls that overlap with our proposed mapping
	 * - we can only share with an exact match on most regular files
	 * - shared mappings on character devices and memory backed files are
	 *   permitted to overlap inexactly as far as we are concerned for in
	 *   these cases, sharing is handled in the driver or filesystem rather
	 *   than here
	 */
	if (vm_flags & VM_MAYSHARE) {
		unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
		unsigned long vmpglen;

		for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
			vma = rb_entry(rb, struct vm_area_struct, vm_rb);

			if (!(vma->vm_flags & VM_MAYSHARE))
				continue;

			/* search for overlapping mappings on the same file */
			if (vma->vm_file->f_dentry->d_inode != file->f_dentry->d_inode)
				continue;

			if (vma->vm_pgoff >= pgoff + pglen)
				continue;

			vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
			vmpglen >>= PAGE_SHIFT;
			if (pgoff >= vma->vm_pgoff + vmpglen)
				continue;

			/* handle inexactly overlapping matches between mappings */
			if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
				if (!(capabilities & BDI_CAP_MAP_DIRECT))
					goto sharing_violation;
				continue;
			}

			/* we've found a VMA we can share */
			atomic_inc(&vma->vm_usage);

			vml->vma = vma;
			result = (void *) vma->vm_start;
			goto shared;
		}

		vma = NULL;

		/* obtain the address at which to make a shared mapping
		 * - this is the hook for quasi-memory character devices to
		 *   tell us the location of a shared mapping
		 */
		if (file && file->f_op->get_unmapped_area) {
			addr = file->f_op->get_unmapped_area(file, addr, len,
							     pgoff, flags);
			if (IS_ERR((void *) addr)) {
				ret = addr;
				if (ret != (unsigned long) -ENOSYS)
					goto error;

				/* the driver refused to tell us where to site
				 * the mapping so we'll have to attempt to copy
				 * it */
				ret = (unsigned long) -ENODEV;
				if (!(capabilities & BDI_CAP_MAP_COPY))
					goto error;

				capabilities &= ~BDI_CAP_MAP_DIRECT;
			}
		}
	}

	/* we're going to need a VMA struct as well */
	vma = kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
	if (!vma)
		goto error_getting_vma;

	memset(vma, 0, sizeof(*vma));
	INIT_LIST_HEAD(&vma->anon_vma_node);
	atomic_set(&vma->vm_usage, 1);
	if (file)
		get_file(file);
	vma->vm_file	= file;
	vma->vm_flags	= vm_flags;
	vma->vm_start	= addr;
	vma->vm_end	= addr + len;
	vma->vm_pgoff	= pgoff;

	vml->vma = vma;

	/* set up the mapping */
	if (file && vma->vm_flags & VM_SHARED)
		ret = do_mmap_shared_file(vma, len);
	else
		ret = do_mmap_private(vma, len);
	if (ret < 0)
		goto error;

	/* okay... we have a mapping; now we have to register it */
	result = (void *) vma->vm_start;

	if (vma->vm_flags & VM_MAPPED_COPY) {
		realalloc += kobjsize(result);
		askedalloc += len;
	}

	realalloc += kobjsize(vma);
	askedalloc += sizeof(*vma);

	current->mm->total_vm += len >> PAGE_SHIFT;

	add_nommu_vma(vma);

 shared:
	realalloc += kobjsize(vml);
	askedalloc += sizeof(*vml);

	vml->next = current->mm->context.vmlist;
	current->mm->context.vmlist = vml;

	up_write(&nommu_vma_sem);

	if (prot & PROT_EXEC)
		flush_icache_range((unsigned long) result,
				   (unsigned long) result + len);

#ifdef DEBUG
	printk("do_mmap:\n");
	show_process_blocks();
#endif

	return (unsigned long) result;

 error:
	up_write(&nommu_vma_sem);
	kfree(vml);
	if (vma) {
		fput(vma->vm_file);
		kfree(vma);
	}
	return ret;

 sharing_violation:
	up_write(&nommu_vma_sem);
	printk("Attempt to share mismatched mappings\n");
	kfree(vml);
	return -EINVAL;

 error_getting_vma:
	up_write(&nommu_vma_sem);
	kfree(vml);
	printk("Allocation of vma for %lu byte allocation from process %d failed\n",
	       len, current->pid);
	show_free_areas();
	return -ENOMEM;

 error_getting_vml:
	printk("Allocation of vml for %lu byte allocation from process %d failed\n",
	       len, current->pid);
	show_free_areas();
	return -ENOMEM;
}

/*
 * handle mapping disposal for uClinux
 */
static void put_vma(struct vm_area_struct *vma)
{
	if (vma) {
		down_write(&nommu_vma_sem);

		if (atomic_dec_and_test(&vma->vm_usage)) {
			delete_nommu_vma(vma);

			if (vma->vm_ops && vma->vm_ops->close)
				vma->vm_ops->close(vma);

			/* IO memory and memory shared directly out of the pagecache from
			 * ramfs/tmpfs mustn't be released here */
			if (vma->vm_flags & VM_MAPPED_COPY) {
				realalloc -= kobjsize((void *) vma->vm_start);
				askedalloc -= vma->vm_end - vma->vm_start;
				kfree((void *) vma->vm_start);
			}

			realalloc -= kobjsize(vma);
			askedalloc -= sizeof(*vma);

			if (vma->vm_file)
				fput(vma->vm_file);
			kfree(vma);
		}

		up_write(&nommu_vma_sem);
	}
}

int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
{
	struct vm_list_struct *vml, **parent;
	unsigned long end = addr + len;

#ifdef DEBUG
	printk("do_munmap:\n");
#endif

	for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next)
		if ((*parent)->vma->vm_start == addr &&
		    ((len == 0) || ((*parent)->vma->vm_end == end)))
			goto found;

	printk("munmap of non-mmaped memory by process %d (%s): %p\n",
	       current->pid, current->comm, (void *) addr);
	return -EINVAL;

 found:
	vml = *parent;

	put_vma(vml->vma);

	*parent = vml->next;
	realalloc -= kobjsize(vml);
	askedalloc -= sizeof(*vml);
	kfree(vml);

	update_hiwater_vm(mm);
	mm->total_vm -= len >> PAGE_SHIFT;

#ifdef DEBUG
	show_process_blocks();
#endif

	return 0;
}

/* Release all mmaps. */
void exit_mmap(struct mm_struct * mm)
{
	struct vm_list_struct *tmp;

	if (mm) {
#ifdef DEBUG
		printk("Exit_mmap:\n");
#endif

		mm->total_vm = 0;

		while ((tmp = mm->context.vmlist)) {
			mm->context.vmlist = tmp->next;
			put_vma(tmp->vma);

			realalloc -= kobjsize(tmp);
			askedalloc -= sizeof(*tmp);
			kfree(tmp);
		}

#ifdef DEBUG
		show_process_blocks();
#endif
	}
}

asmlinkage long sys_munmap(unsigned long addr, size_t len)
{
	int ret;
	struct mm_struct *mm = current->mm;

	down_write(&mm->mmap_sem);
	ret = do_munmap(mm, addr, len);
	up_write(&mm->mmap_sem);
	return ret;
}

unsigned long do_brk(unsigned long addr, unsigned long len)
{
	return -ENOMEM;
}

/*
 * Expand (or shrink) an existing mapping, potentially moving it at the
 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 *
 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 * This option implies MREMAP_MAYMOVE.
 *
 * on uClinux, we only permit changing a mapping's size, and only as long as it stays within the
 * hole allocated by the kmalloc() call in do_mmap_pgoff() and the block is not shareable
 */
unsigned long do_mremap(unsigned long addr,
			unsigned long old_len, unsigned long new_len,
			unsigned long flags, unsigned long new_addr)
{
	struct vm_list_struct *vml = NULL;

	/* insanity checks first */
	if (new_len == 0)
		return (unsigned long) -EINVAL;

	if (flags & MREMAP_FIXED && new_addr != addr)
		return (unsigned long) -EINVAL;

	for (vml = current->mm->context.vmlist; vml; vml = vml->next)
		if (vml->vma->vm_start == addr)
			goto found;

	return (unsigned long) -EINVAL;

 found:
	if (vml->vma->vm_end != vml->vma->vm_start + old_len)
		return (unsigned long) -EFAULT;

	if (vml->vma->vm_flags & VM_MAYSHARE)
		return (unsigned long) -EPERM;

	if (new_len > kobjsize((void *) addr))
		return (unsigned long) -ENOMEM;

	/* all checks complete - do it */
	vml->vma->vm_end = vml->vma->vm_start + new_len;

	askedalloc -= old_len;
	askedalloc += new_len;

	return vml->vma->vm_start;
}

/*
 * Look up the first VMA which satisfies  addr < vm_end,  NULL if none
 * - should be called with mm->mmap_sem at least readlocked
 */
struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{
	struct vm_list_struct *vml;

	for (vml = mm->context.vmlist; vml; vml = vml->next)
		if (addr >= vml->vma->vm_start && addr < vml->vma->vm_end)
			return vml->vma;

	return NULL;
}

EXPORT_SYMBOL(find_vma);

struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
			unsigned int foll_flags)
{
	return NULL;
}

struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
{
	return NULL;
}

int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
		unsigned long to, unsigned long size, pgprot_t prot)
{
	vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
	return 0;
}
EXPORT_SYMBOL(remap_pfn_range);

void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
{
}

unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
	unsigned long len, unsigned long pgoff, unsigned long flags)
{
	return -ENOMEM;
}

void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
{
}

void unmap_mapping_range(struct address_space *mapping,
			 loff_t const holebegin, loff_t const holelen,
			 int even_cows)
{
}
EXPORT_SYMBOL(unmap_mapping_range);

/*
 * Check that a process has enough memory to allocate a new virtual
 * mapping. 0 means there is enough memory for the allocation to
 * succeed and -ENOMEM implies there is not.
 *
 * We currently support three overcommit policies, which are set via the
 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
 *
 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 * Additional code 2002 Jul 20 by Robert Love.
 *
 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 *
 * Note this is a helper function intended to be used by LSMs which
 * wish to use this logic.
 */
int __vm_enough_memory(long pages, int cap_sys_admin)
{
	unsigned long free, allowed;

	vm_acct_memory(pages);

	/*
	 * Sometimes we want to use more memory than we have
	 */
	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
		return 0;

	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
		unsigned long n;

		free = global_page_state(NR_FILE_PAGES);
		free += nr_swap_pages;

		/*
		 * Any slabs which are created with the
		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
		 * which are reclaimable, under pressure.  The dentry
		 * cache and most inode caches should fall into this
		 */
		free += global_page_state(NR_SLAB_RECLAIMABLE);

		/*
		 * Leave the last 3% for root
		 */
		if (!cap_sys_admin)
			free -= free / 32;

		if (free > pages)
			return 0;

		/*
		 * nr_free_pages() is very expensive on large systems,
		 * only call if we're about to fail.
		 */
		n = nr_free_pages();

		/*
		 * Leave reserved pages. The pages are not for anonymous pages.
		 */
		if (n <= totalreserve_pages)
			goto error;
		else
			n -= totalreserve_pages;

		/*
		 * Leave the last 3% for root
		 */
		if (!cap_sys_admin)
			n -= n / 32;
		free += n;

		if (free > pages)
			return 0;

		goto error;
	}

	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
	/*
	 * Leave the last 3% for root
	 */
	if (!cap_sys_admin)
		allowed -= allowed / 32;
	allowed += total_swap_pages;

	/* Don't let a single process grow too big:
	   leave 3% of the size of this process for other processes */
	allowed -= current->mm->total_vm / 32;

	/*
	 * cast `allowed' as a signed long because vm_committed_space
	 * sometimes has a negative value
	 */
	if (atomic_read(&vm_committed_space) < (long)allowed)
		return 0;
error:
	vm_unacct_memory(pages);

	return -ENOMEM;
}

int in_gate_area_no_task(unsigned long addr)
{
	return 0;
}

struct page *filemap_nopage(struct vm_area_struct *area,
			unsigned long address, int *type)
{
	BUG();
	return NULL;
}

/*
 * Access another process' address space.
 * - source/target buffer must be kernel space
 */
int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
{
	struct vm_area_struct *vma;
	struct mm_struct *mm;

	if (addr + len < addr)
		return 0;

	mm = get_task_mm(tsk);
	if (!mm)
		return 0;

	down_read(&mm->mmap_sem);

	/* the access must start within one of the target process's mappings */
	vma = find_vma(mm, addr);
	if (vma) {
		/* don't overrun this mapping */
		if (addr + len >= vma->vm_end)
			len = vma->vm_end - addr;

		/* only read or write mappings where it is permitted */
		if (write && vma->vm_flags & VM_WRITE)
			len -= copy_to_user((void *) addr, buf, len);
		else if (!write && vma->vm_flags & VM_READ)
			len -= copy_from_user(buf, (void *) addr, len);
		else
			len = 0;
	} else {
		len = 0;
	}

	up_read(&mm->mmap_sem);
	mmput(mm);
	return len;
}