aboutsummaryrefslogtreecommitdiff
path: root/lib/dma-debug.c
blob: 66ce414891330964aacb48dee8079138034cad3d (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
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
/*
 * Copyright (C) 2008 Advanced Micro Devices, Inc.
 *
 * Author: Joerg Roedel <joerg.roedel@amd.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */

#include <linux/scatterlist.h>
#include <linux/dma-mapping.h>
#include <linux/stacktrace.h>
#include <linux/dma-debug.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/slab.h>

#include <asm/sections.h>

#define HASH_SIZE       1024ULL
#define HASH_FN_SHIFT   13
#define HASH_FN_MASK    (HASH_SIZE - 1)

enum {
	dma_debug_single,
	dma_debug_page,
	dma_debug_sg,
	dma_debug_coherent,
};

#define DMA_DEBUG_STACKTRACE_ENTRIES 5

struct dma_debug_entry {
	struct list_head list;
	struct device    *dev;
	int              type;
	phys_addr_t      paddr;
	u64              dev_addr;
	u64              size;
	int              direction;
	int		 sg_call_ents;
	int		 sg_mapped_ents;
#ifdef CONFIG_STACKTRACE
	struct		 stack_trace stacktrace;
	unsigned long	 st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
#endif
};

typedef bool (*match_fn)(struct dma_debug_entry *, struct dma_debug_entry *);

struct hash_bucket {
	struct list_head list;
	spinlock_t lock;
} ____cacheline_aligned_in_smp;

/* Hash list to save the allocated dma addresses */
static struct hash_bucket dma_entry_hash[HASH_SIZE];
/* List of pre-allocated dma_debug_entry's */
static LIST_HEAD(free_entries);
/* Lock for the list above */
static DEFINE_SPINLOCK(free_entries_lock);

/* Global disable flag - will be set in case of an error */
static u32 global_disable __read_mostly;

/* Global error count */
static u32 error_count;

/* Global error show enable*/
static u32 show_all_errors __read_mostly;
/* Number of errors to show */
static u32 show_num_errors = 1;

static u32 num_free_entries;
static u32 min_free_entries;
static u32 nr_total_entries;

/* number of preallocated entries requested by kernel cmdline */
static u32 req_entries;

/* debugfs dentry's for the stuff above */
static struct dentry *dma_debug_dent        __read_mostly;
static struct dentry *global_disable_dent   __read_mostly;
static struct dentry *error_count_dent      __read_mostly;
static struct dentry *show_all_errors_dent  __read_mostly;
static struct dentry *show_num_errors_dent  __read_mostly;
static struct dentry *num_free_entries_dent __read_mostly;
static struct dentry *min_free_entries_dent __read_mostly;
static struct dentry *filter_dent           __read_mostly;

/* per-driver filter related state */

#define NAME_MAX_LEN	64

static char                  current_driver_name[NAME_MAX_LEN] __read_mostly;
static struct device_driver *current_driver                    __read_mostly;

static DEFINE_RWLOCK(driver_name_lock);

static const char *type2name[4] = { "single", "page",
				    "scather-gather", "coherent" };

static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE",
				   "DMA_FROM_DEVICE", "DMA_NONE" };

/* little merge helper - remove it after the merge window */
#ifndef BUS_NOTIFY_UNBOUND_DRIVER
#define BUS_NOTIFY_UNBOUND_DRIVER 0x0005
#endif

/*
 * The access to some variables in this macro is racy. We can't use atomic_t
 * here because all these variables are exported to debugfs. Some of them even
 * writeable. This is also the reason why a lock won't help much. But anyway,
 * the races are no big deal. Here is why:
 *
 *   error_count: the addition is racy, but the worst thing that can happen is
 *                that we don't count some errors
 *   show_num_errors: the subtraction is racy. Also no big deal because in
 *                    worst case this will result in one warning more in the
 *                    system log than the user configured. This variable is
 *                    writeable via debugfs.
 */
static inline void dump_entry_trace(struct dma_debug_entry *entry)
{
#ifdef CONFIG_STACKTRACE
	if (entry) {
		pr_warning("Mapped at:\n");
		print_stack_trace(&entry->stacktrace, 0);
	}
#endif
}

static bool driver_filter(struct device *dev)
{
	struct device_driver *drv;
	unsigned long flags;
	bool ret;

	/* driver filter off */
	if (likely(!current_driver_name[0]))
		return true;

	/* driver filter on and initialized */
	if (current_driver && dev && dev->driver == current_driver)
		return true;

	/* driver filter on, but we can't filter on a NULL device... */
	if (!dev)
		return false;

	if (current_driver || !current_driver_name[0])
		return false;

	/* driver filter on but not yet initialized */
	drv = dev->driver;
	if (!drv)
		return false;

	/* lock to protect against change of current_driver_name */
	read_lock_irqsave(&driver_name_lock, flags);

	ret = false;
	if (drv->name &&
	    strncmp(current_driver_name, drv->name, NAME_MAX_LEN - 1) == 0) {
		current_driver = drv;
		ret = true;
	}

	read_unlock_irqrestore(&driver_name_lock, flags);

	return ret;
}

#define err_printk(dev, entry, format, arg...) do {			\
		error_count += 1;					\
		if (driver_filter(dev) &&				\
		    (show_all_errors || show_num_errors > 0)) {		\
			WARN(1, "%s %s: " format,			\
			     dev ? dev_driver_string(dev) : "NULL",	\
			     dev ? dev_name(dev) : "NULL", ## arg);	\
			dump_entry_trace(entry);			\
		}							\
		if (!show_all_errors && show_num_errors > 0)		\
			show_num_errors -= 1;				\
	} while (0);

/*
 * Hash related functions
 *
 * Every DMA-API request is saved into a struct dma_debug_entry. To
 * have quick access to these structs they are stored into a hash.
 */
static int hash_fn(struct dma_debug_entry *entry)
{
	/*
	 * Hash function is based on the dma address.
	 * We use bits 20-27 here as the index into the hash
	 */
	return (entry->dev_addr >> HASH_FN_SHIFT) & HASH_FN_MASK;
}

/*
 * Request exclusive access to a hash bucket for a given dma_debug_entry.
 */
static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry,
					   unsigned long *flags)
{
	int idx = hash_fn(entry);
	unsigned long __flags;

	spin_lock_irqsave(&dma_entry_hash[idx].lock, __flags);
	*flags = __flags;
	return &dma_entry_hash[idx];
}

/*
 * Give up exclusive access to the hash bucket
 */
static void put_hash_bucket(struct hash_bucket *bucket,
			    unsigned long *flags)
{
	unsigned long __flags = *flags;

	spin_unlock_irqrestore(&bucket->lock, __flags);
}

static bool exact_match(struct dma_debug_entry *a, struct dma_debug_entry *b)
{
	return ((a->dev_addr == b->dev_addr) &&
		(a->dev == b->dev)) ? true : false;
}

static bool containing_match(struct dma_debug_entry *a,
			     struct dma_debug_entry *b)
{
	if (a->dev != b->dev)
		return false;

	if ((b->dev_addr <= a->dev_addr) &&
	    ((b->dev_addr + b->size) >= (a->dev_addr + a->size)))
		return true;

	return false;
}

/*
 * Search a given entry in the hash bucket list
 */
static struct dma_debug_entry *__hash_bucket_find(struct hash_bucket *bucket,
						  struct dma_debug_entry *ref,
						  match_fn match)
{
	struct dma_debug_entry *entry, *ret = NULL;
	int matches = 0, match_lvl, last_lvl = 0;

	list_for_each_entry(entry, &bucket->list, list) {
		if (!match(ref, entry))
			continue;

		/*
		 * Some drivers map the same physical address multiple
		 * times. Without a hardware IOMMU this results in the
		 * same device addresses being put into the dma-debug
		 * hash multiple times too. This can result in false
		 * positives being reported. Therefore we implement a
		 * best-fit algorithm here which returns the entry from
		 * the hash which fits best to the reference value
		 * instead of the first-fit.
		 */
		matches += 1;
		match_lvl = 0;
		entry->size         == ref->size         ? ++match_lvl : 0;
		entry->type         == ref->type         ? ++match_lvl : 0;
		entry->direction    == ref->direction    ? ++match_lvl : 0;
		entry->sg_call_ents == ref->sg_call_ents ? ++match_lvl : 0;

		if (match_lvl == 4) {
			/* perfect-fit - return the result */
			return entry;
		} else if (match_lvl > last_lvl) {
			/*
			 * We found an entry that fits better then the
			 * previous one
			 */
			last_lvl = match_lvl;
			ret      = entry;
		}
	}

	/*
	 * If we have multiple matches but no perfect-fit, just return
	 * NULL.
	 */
	ret = (matches == 1) ? ret : NULL;

	return ret;
}

static struct dma_debug_entry *bucket_find_exact(struct hash_bucket *bucket,
						 struct dma_debug_entry *ref)
{
	return __hash_bucket_find(bucket, ref, exact_match);
}

static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
						   struct dma_debug_entry *ref,
						   unsigned long *flags)
{

	unsigned int max_range = dma_get_max_seg_size(ref->dev);
	struct dma_debug_entry *entry, index = *ref;
	unsigned int range = 0;

	while (range <= max_range) {
		entry = __hash_bucket_find(*bucket, &index, containing_match);

		if (entry)
			return entry;

		/*
		 * Nothing found, go back a hash bucket
		 */
		put_hash_bucket(*bucket, flags);
		range          += (1 << HASH_FN_SHIFT);
		index.dev_addr -= (1 << HASH_FN_SHIFT);
		*bucket = get_hash_bucket(&index, flags);
	}

	return NULL;
}

/*
 * Add an entry to a hash bucket
 */
static void hash_bucket_add(struct hash_bucket *bucket,
			    struct dma_debug_entry *entry)
{
	list_add_tail(&entry->list, &bucket->list);
}

/*
 * Remove entry from a hash bucket list
 */
static void hash_bucket_del(struct dma_debug_entry *entry)
{
	list_del(&entry->list);
}

/*
 * Dump mapping entries for debugging purposes
 */
void debug_dma_dump_mappings(struct device *dev)
{
	int idx;

	for (idx = 0; idx < HASH_SIZE; idx++) {
		struct hash_bucket *bucket = &dma_entry_hash[idx];
		struct dma_debug_entry *entry;
		unsigned long flags;

		spin_lock_irqsave(&bucket->lock, flags);

		list_for_each_entry(entry, &bucket->list, list) {
			if (!dev || dev == entry->dev) {
				dev_info(entry->dev,
					 "%s idx %d P=%Lx D=%Lx L=%Lx %s\n",
					 type2name[entry->type], idx,
					 (unsigned long long)entry->paddr,
					 entry->dev_addr, entry->size,
					 dir2name[entry->direction]);
			}
		}

		spin_unlock_irqrestore(&bucket->lock, flags);
	}
}
EXPORT_SYMBOL(debug_dma_dump_mappings);

/*
 * Wrapper function for adding an entry to the hash.
 * This function takes care of locking itself.
 */
static void add_dma_entry(struct dma_debug_entry *entry)
{
	struct hash_bucket *bucket;
	unsigned long flags;

	bucket = get_hash_bucket(entry, &flags);
	hash_bucket_add(bucket, entry);
	put_hash_bucket(bucket, &flags);
}

static struct dma_debug_entry *__dma_entry_alloc(void)
{
	struct dma_debug_entry *entry;

	entry = list_entry(free_entries.next, struct dma_debug_entry, list);
	list_del(&entry->list);
	memset(entry, 0, sizeof(*entry));

	num_free_entries -= 1;
	if (num_free_entries < min_free_entries)
		min_free_entries = num_free_entries;

	return entry;
}

/* struct dma_entry allocator
 *
 * The next two functions implement the allocator for
 * struct dma_debug_entries.
 */
static struct dma_debug_entry *dma_entry_alloc(void)
{
	struct dma_debug_entry *entry;
	unsigned long flags;

	spin_lock_irqsave(&free_entries_lock, flags);

	if (list_empty(&free_entries)) {
		pr_err("DMA-API: debugging out of memory - disabling\n");
		global_disable = true;
		spin_unlock_irqrestore(&free_entries_lock, flags);
		return NULL;
	}

	entry = __dma_entry_alloc();

	spin_unlock_irqrestore(&free_entries_lock, flags);

#ifdef CONFIG_STACKTRACE
	entry->stacktrace.max_entries = DMA_DEBUG_STACKTRACE_ENTRIES;
	entry->stacktrace.entries = entry->st_entries;
	entry->stacktrace.skip = 2;
	save_stack_trace(&entry->stacktrace);
#endif

	return entry;
}

static void dma_entry_free(struct dma_debug_entry *entry)
{
	unsigned long flags;

	/*
	 * add to beginning of the list - this way the entries are
	 * more likely cache hot when they are reallocated.
	 */
	spin_lock_irqsave(&free_entries_lock, flags);
	list_add(&entry->list, &free_entries);
	num_free_entries += 1;
	spin_unlock_irqrestore(&free_entries_lock, flags);
}

int dma_debug_resize_entries(u32 num_entries)
{
	int i, delta, ret = 0;
	unsigned long flags;
	struct dma_debug_entry *entry;
	LIST_HEAD(tmp);

	spin_lock_irqsave(&free_entries_lock, flags);

	if (nr_total_entries < num_entries) {
		delta = num_entries - nr_total_entries;

		spin_unlock_irqrestore(&free_entries_lock, flags);

		for (i = 0; i < delta; i++) {
			entry = kzalloc(sizeof(*entry), GFP_KERNEL);
			if (!entry)
				break;

			list_add_tail(&entry->list, &tmp);
		}

		spin_lock_irqsave(&free_entries_lock, flags);

		list_splice(&tmp, &free_entries);
		nr_total_entries += i;
		num_free_entries += i;
	} else {
		delta = nr_total_entries - num_entries;

		for (i = 0; i < delta && !list_empty(&free_entries); i++) {
			entry = __dma_entry_alloc();
			kfree(entry);
		}

		nr_total_entries -= i;
	}

	if (nr_total_entries != num_entries)
		ret = 1;

	spin_unlock_irqrestore(&free_entries_lock, flags);

	return ret;
}
EXPORT_SYMBOL(dma_debug_resize_entries);

/*
 * DMA-API debugging init code
 *
 * The init code does two things:
 *   1. Initialize core data structures
 *   2. Preallocate a given number of dma_debug_entry structs
 */

static int prealloc_memory(u32 num_entries)
{
	struct dma_debug_entry *entry, *next_entry;
	int i;

	for (i = 0; i < num_entries; ++i) {
		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
		if (!entry)
			goto out_err;

		list_add_tail(&entry->list, &free_entries);
	}

	num_free_entries = num_entries;
	min_free_entries = num_entries;

	pr_info("DMA-API: preallocated %d debug entries\n", num_entries);

	return 0;

out_err:

	list_for_each_entry_safe(entry, next_entry, &free_entries, list) {
		list_del(&entry->list);
		kfree(entry);
	}

	return -ENOMEM;
}

static ssize_t filter_read(struct file *file, char __user *user_buf,
			   size_t count, loff_t *ppos)
{
	char buf[NAME_MAX_LEN + 1];
	unsigned long flags;
	int len;

	if (!current_driver_name[0])
		return 0;

	/*
	 * We can't copy to userspace directly because current_driver_name can
	 * only be read under the driver_name_lock with irqs disabled. So
	 * create a temporary copy first.
	 */
	read_lock_irqsave(&driver_name_lock, flags);
	len = scnprintf(buf, NAME_MAX_LEN + 1, "%s\n", current_driver_name);
	read_unlock_irqrestore(&driver_name_lock, flags);

	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
}

static ssize_t filter_write(struct file *file, const char __user *userbuf,
			    size_t count, loff_t *ppos)
{
	char buf[NAME_MAX_LEN];
	unsigned long flags;
	size_t len;
	int i;

	/*
	 * We can't copy from userspace directly. Access to
	 * current_driver_name is protected with a write_lock with irqs
	 * disabled. Since copy_from_user can fault and may sleep we
	 * need to copy to temporary buffer first
	 */
	len = min(count, (size_t)(NAME_MAX_LEN - 1));
	if (copy_from_user(buf, userbuf, len))
		return -EFAULT;

	buf[len] = 0;

	write_lock_irqsave(&driver_name_lock, flags);

	/*
	 * Now handle the string we got from userspace very carefully.
	 * The rules are:
	 *         - only use the first token we got
	 *         - token delimiter is everything looking like a space
	 *           character (' ', '\n', '\t' ...)
	 *
	 */
	if (!isalnum(buf[0])) {
		/*
		 * If the first character userspace gave us is not
		 * alphanumerical then assume the filter should be
		 * switched off.
		 */
		if (current_driver_name[0])
			pr_info("DMA-API: switching off dma-debug driver filter\n");
		current_driver_name[0] = 0;
		current_driver = NULL;
		goto out_unlock;
	}

	/*
	 * Now parse out the first token and use it as the name for the
	 * driver to filter for.
	 */
	for (i = 0; i < NAME_MAX_LEN - 1; ++i) {
		current_driver_name[i] = buf[i];
		if (isspace(buf[i]) || buf[i] == ' ' || buf[i] == 0)
			break;
	}
	current_driver_name[i] = 0;
	current_driver = NULL;

	pr_info("DMA-API: enable driver filter for driver [%s]\n",
		current_driver_name);

out_unlock:
	write_unlock_irqrestore(&driver_name_lock, flags);

	return count;
}

static const struct file_operations filter_fops = {
	.read  = filter_read,
	.write = filter_write,
	.llseek = default_llseek,
};

static int dma_debug_fs_init(void)
{
	dma_debug_dent = debugfs_create_dir("dma-api", NULL);
	if (!dma_debug_dent) {
		pr_err("DMA-API: can not create debugfs directory\n");
		return -ENOMEM;
	}

	global_disable_dent = debugfs_create_bool("disabled", 0444,
			dma_debug_dent,
			&global_disable);
	if (!global_disable_dent)
		goto out_err;

	error_count_dent = debugfs_create_u32("error_count", 0444,
			dma_debug_dent, &error_count);
	if (!error_count_dent)
		goto out_err;

	show_all_errors_dent = debugfs_create_u32("all_errors", 0644,
			dma_debug_dent,
			&show_all_errors);
	if (!show_all_errors_dent)
		goto out_err;

	show_num_errors_dent = debugfs_create_u32("num_errors", 0644,
			dma_debug_dent,
			&show_num_errors);
	if (!show_num_errors_dent)
		goto out_err;

	num_free_entries_dent = debugfs_create_u32("num_free_entries", 0444,
			dma_debug_dent,
			&num_free_entries);
	if (!num_free_entries_dent)
		goto out_err;

	min_free_entries_dent = debugfs_create_u32("min_free_entries", 0444,
			dma_debug_dent,
			&min_free_entries);
	if (!min_free_entries_dent)
		goto out_err;

	filter_dent = debugfs_create_file("driver_filter", 0644,
					  dma_debug_dent, NULL, &filter_fops);
	if (!filter_dent)
		goto out_err;

	return 0;

out_err:
	debugfs_remove_recursive(dma_debug_dent);

	return -ENOMEM;
}

static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)
{
	struct dma_debug_entry *entry;
	unsigned long flags;
	int count = 0, i;

	local_irq_save(flags);

	for (i = 0; i < HASH_SIZE; ++i) {
		spin_lock(&dma_entry_hash[i].lock);
		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
			if (entry->dev == dev) {
				count += 1;
				*out_entry = entry;
			}
		}
		spin_unlock(&dma_entry_hash[i].lock);
	}

	local_irq_restore(flags);

	return count;
}

static int dma_debug_device_change(struct notifier_block *nb, unsigned long action, void *data)
{
	struct device *dev = data;
	struct dma_debug_entry *uninitialized_var(entry);
	int count;

	if (global_disable)
		return 0;

	switch (action) {
	case BUS_NOTIFY_UNBOUND_DRIVER:
		count = device_dma_allocations(dev, &entry);
		if (count == 0)
			break;
		err_printk(dev, entry, "DMA-API: device driver has pending "
				"DMA allocations while released from device "
				"[count=%d]\n"
				"One of leaked entries details: "
				"[device address=0x%016llx] [size=%llu bytes] "
				"[mapped with %s] [mapped as %s]\n",
			count, entry->dev_addr, entry->size,
			dir2name[entry->direction], type2name[entry->type]);
		break;
	default:
		break;
	}

	return 0;
}

void dma_debug_add_bus(struct bus_type *bus)
{
	struct notifier_block *nb;

	if (global_disable)
		return;

	nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
	if (nb == NULL) {
		pr_err("dma_debug_add_bus: out of memory\n");
		return;
	}

	nb->notifier_call = dma_debug_device_change;

	bus_register_notifier(bus, nb);
}

/*
 * Let the architectures decide how many entries should be preallocated.
 */
void dma_debug_init(u32 num_entries)
{
	int i;

	if (global_disable)
		return;

	for (i = 0; i < HASH_SIZE; ++i) {
		INIT_LIST_HEAD(&dma_entry_hash[i].list);
		spin_lock_init(&dma_entry_hash[i].lock);
	}

	if (dma_debug_fs_init() != 0) {
		pr_err("DMA-API: error creating debugfs entries - disabling\n");
		global_disable = true;

		return;
	}

	if (req_entries)
		num_entries = req_entries;

	if (prealloc_memory(num_entries) != 0) {
		pr_err("DMA-API: debugging out of memory error - disabled\n");
		global_disable = true;

		return;
	}

	nr_total_entries = num_free_entries;

	pr_info("DMA-API: debugging enabled by kernel config\n");
}

static __init int dma_debug_cmdline(char *str)
{
	if (!str)
		return -EINVAL;

	if (strncmp(str, "off", 3) == 0) {
		pr_info("DMA-API: debugging disabled on kernel command line\n");
		global_disable = true;
	}

	return 0;
}

static __init int dma_debug_entries_cmdline(char *str)
{
	int res;

	if (!str)
		return -EINVAL;

	res = get_option(&str, &req_entries);

	if (!res)
		req_entries = 0;

	return 0;
}

__setup("dma_debug=", dma_debug_cmdline);
__setup("dma_debug_entries=", dma_debug_entries_cmdline);

static void check_unmap(struct dma_debug_entry *ref)
{
	struct dma_debug_entry *entry;
	struct hash_bucket *bucket;
	unsigned long flags;

	if (dma_mapping_error(ref->dev, ref->dev_addr)) {
		err_printk(ref->dev, NULL, "DMA-API: device driver tries "
			   "to free an invalid DMA memory address\n");
		return;
	}

	bucket = get_hash_bucket(ref, &flags);
	entry = bucket_find_exact(bucket, ref);

	if (!entry) {
		err_printk(ref->dev, NULL, "DMA-API: device driver tries "
			   "to free DMA memory it has not allocated "
			   "[device address=0x%016llx] [size=%llu bytes]\n",
			   ref->dev_addr, ref->size);
		goto out;
	}

	if (ref->size != entry->size) {
		err_printk(ref->dev, entry, "DMA-API: device driver frees "
			   "DMA memory with different size "
			   "[device address=0x%016llx] [map size=%llu bytes] "
			   "[unmap size=%llu bytes]\n",
			   ref->dev_addr, entry->size, ref->size);
	}

	if (ref->type != entry->type) {
		err_printk(ref->dev, entry, "DMA-API: device driver frees "
			   "DMA memory with wrong function "
			   "[device address=0x%016llx] [size=%llu bytes] "
			   "[mapped as %s] [unmapped as %s]\n",
			   ref->dev_addr, ref->size,
			   type2name[entry->type], type2name[ref->type]);
	} else if ((entry->type == dma_debug_coherent) &&
		   (ref->paddr != entry->paddr)) {
		err_printk(ref->dev, entry, "DMA-API: device driver frees "
			   "DMA memory with different CPU address "
			   "[device address=0x%016llx] [size=%llu bytes] "
			   "[cpu alloc address=0x%016llx] "
			   "[cpu free address=0x%016llx]",
			   ref->dev_addr, ref->size,
			   (unsigned long long)entry->paddr,
			   (unsigned long long)ref->paddr);
	}

	if (ref->sg_call_ents && ref->type == dma_debug_sg &&
	    ref->sg_call_ents != entry->sg_call_ents) {
		err_printk(ref->dev, entry, "DMA-API: device driver frees "
			   "DMA sg list with different entry count "
			   "[map count=%d] [unmap count=%d]\n",
			   entry->sg_call_ents, ref->sg_call_ents);
	}

	/*
	 * This may be no bug in reality - but most implementations of the
	 * DMA API don't handle this properly, so check for it here
	 */
	if (ref->direction != entry->direction) {
		err_printk(ref->dev, entry, "DMA-API: device driver frees "
			   "DMA memory with different direction "
			   "[device address=0x%016llx] [size=%llu bytes] "
			   "[mapped with %s] [unmapped with %s]\n",
			   ref->dev_addr, ref->size,
			   dir2name[entry->direction],
			   dir2name[ref->direction]);
	}

	hash_bucket_del(entry);
	dma_entry_free(entry);

out:
	put_hash_bucket(bucket, &flags);
}

static void check_for_stack(struct device *dev, void *addr)
{
	if (object_is_on_stack(addr))
		err_printk(dev, NULL, "DMA-API: device driver maps memory from"
				"stack [addr=%p]\n", addr);
}

static inline bool overlap(void *addr, unsigned long len, void *start, void *end)
{
	unsigned long a1 = (unsigned long)addr;
	unsigned long b1 = a1 + len;
	unsigned long a2 = (unsigned long)start;
	unsigned long b2 = (unsigned long)end;

	return !(b1 <= a2 || a1 >= b2);
}

static void check_for_illegal_area(struct device *dev, void *addr, unsigned long len)
{
	if (overlap(addr, len, _text, _etext) ||
	    overlap(addr, len, __start_rodata, __end_rodata))
		err_printk(dev, NULL, "DMA-API: device driver maps memory from kernel text or rodata [addr=%p] [len=%lu]\n", addr, len);
}

static void check_sync(struct device *dev,
		       struct dma_debug_entry *ref,
		       bool to_cpu)
{
	struct dma_debug_entry *entry;
	struct hash_bucket *bucket;
	unsigned long flags;

	bucket = get_hash_bucket(ref, &flags);

	entry = bucket_find_contain(&bucket, ref, &flags);

	if (!entry) {
		err_printk(dev, NULL, "DMA-API: device driver tries "
				"to sync DMA memory it has not allocated "
				"[device address=0x%016llx] [size=%llu bytes]\n",
				(unsigned long long)ref->dev_addr, ref->size);
		goto out;
	}

	if (ref->size > entry->size) {
		err_printk(dev, entry, "DMA-API: device driver syncs"
				" DMA memory outside allocated range "
				"[device address=0x%016llx] "
				"[allocation size=%llu bytes] "
				"[sync offset+size=%llu]\n",
				entry->dev_addr, entry->size,
				ref->size);
	}

	if (entry->direction == DMA_BIDIRECTIONAL)
		goto out;

	if (ref->direction != entry->direction) {
		err_printk(dev, entry, "DMA-API: device driver syncs "
				"DMA memory with different direction "
				"[device address=0x%016llx] [size=%llu bytes] "
				"[mapped with %s] [synced with %s]\n",
				(unsigned long long)ref->dev_addr, entry->size,
				dir2name[entry->direction],
				dir2name[ref->direction]);
	}

	if (to_cpu && !(entry->direction == DMA_FROM_DEVICE) &&
		      !(ref->direction == DMA_TO_DEVICE))
		err_printk(dev, entry, "DMA-API: device driver syncs "
				"device read-only DMA memory for cpu "
				"[device address=0x%016llx] [size=%llu bytes] "
				"[mapped with %s] [synced with %s]\n",
				(unsigned long long)ref->dev_addr, entry->size,
				dir2name[entry->direction],
				dir2name[ref->direction]);

	if (!to_cpu && !(entry->direction == DMA_TO_DEVICE) &&
		       !(ref->direction == DMA_FROM_DEVICE))
		err_printk(dev, entry, "DMA-API: device driver syncs "
				"device write-only DMA memory to device "
				"[device address=0x%016llx] [size=%llu bytes] "
				"[mapped with %s] [synced with %s]\n",
				(unsigned long long)ref->dev_addr, entry->size,
				dir2name[entry->direction],
				dir2name[ref->direction]);

out:
	put_hash_bucket(bucket, &flags);
}

void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
			size_t size, int direction, dma_addr_t dma_addr,
			bool map_single)
{
	struct dma_debug_entry *entry;

	if (unlikely(global_disable))
		return;

	if (unlikely(dma_mapping_error(dev, dma_addr)))
		return;

	entry = dma_entry_alloc();
	if (!entry)
		return;

	entry->dev       = dev;
	entry->type      = dma_debug_page;
	entry->paddr     = page_to_phys(page) + offset;
	entry->dev_addr  = dma_addr;
	entry->size      = size;
	entry->direction = direction;

	if (map_single)
		entry->type = dma_debug_single;

	if (!PageHighMem(page)) {
		void *addr = page_address(page) + offset;

		check_for_stack(dev, addr);
		check_for_illegal_area(dev, addr, size);
	}

	add_dma_entry(entry);
}
EXPORT_SYMBOL(debug_dma_map_page);

void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
			  size_t size, int direction, bool map_single)
{
	struct dma_debug_entry ref = {
		.type           = dma_debug_page,
		.dev            = dev,
		.dev_addr       = addr,
		.size           = size,
		.direction      = direction,
	};

	if (unlikely(global_disable))
		return;

	if (map_single)
		ref.type = dma_debug_single;

	check_unmap(&ref);
}
EXPORT_SYMBOL(debug_dma_unmap_page);

void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
		      int nents, int mapped_ents, int direction)
{
	struct dma_debug_entry *entry;
	struct scatterlist *s;
	int i;

	if (unlikely(global_disable))
		return;

	for_each_sg(sg, s, mapped_ents, i) {
		entry = dma_entry_alloc();
		if (!entry)
			return;

		entry->type           = dma_debug_sg;
		entry->dev            = dev;
		entry->paddr          = sg_phys(s);
		entry->size           = sg_dma_len(s);
		entry->dev_addr       = sg_dma_address(s);
		entry->direction      = direction;
		entry->sg_call_ents   = nents;
		entry->sg_mapped_ents = mapped_ents;

		if (!PageHighMem(sg_page(s))) {
			check_for_stack(dev, sg_virt(s));
			check_for_illegal_area(dev, sg_virt(s), sg_dma_len(s));
		}

		add_dma_entry(entry);
	}
}
EXPORT_SYMBOL(debug_dma_map_sg);

static int get_nr_mapped_entries(struct device *dev,
				 struct dma_debug_entry *ref)
{
	struct dma_debug_entry *entry;
	struct hash_bucket *bucket;
	unsigned long flags;
	int mapped_ents;

	bucket       = get_hash_bucket(ref, &flags);
	entry        = bucket_find_exact(bucket, ref);
	mapped_ents  = 0;

	if (entry)
		mapped_ents = entry->sg_mapped_ents;
	put_hash_bucket(bucket, &flags);

	return mapped_ents;
}

void debug_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
			int nelems, int dir)
{
	struct scatterlist *s;
	int mapped_ents = 0, i;

	if (unlikely(global_disable))
		return;

	for_each_sg(sglist, s, nelems, i) {

		struct dma_debug_entry ref = {
			.type           = dma_debug_sg,
			.dev            = dev,
			.paddr          = sg_phys(s),
			.dev_addr       = sg_dma_address(s),
			.size           = sg_dma_len(s),
			.direction      = dir,
			.sg_call_ents   = nelems,
		};

		if (mapped_ents && i >= mapped_ents)
			break;

		if (!i)
			mapped_ents = get_nr_mapped_entries(dev, &ref);

		check_unmap(&ref);
	}
}
EXPORT_SYMBOL(debug_dma_unmap_sg);

void debug_dma_alloc_coherent(struct device *dev, size_t size,
			      dma_addr_t dma_addr, void *virt)
{
	struct dma_debug_entry *entry;

	if (unlikely(global_disable))
		return;

	if (unlikely(virt == NULL))
		return;

	entry = dma_entry_alloc();
	if (!entry)
		return;

	entry->type      = dma_debug_coherent;
	entry->dev       = dev;
	entry->paddr     = virt_to_phys(virt);
	entry->size      = size;
	entry->dev_addr  = dma_addr;
	entry->direction = DMA_BIDIRECTIONAL;

	add_dma_entry(entry);
}
EXPORT_SYMBOL(debug_dma_alloc_coherent);

void debug_dma_free_coherent(struct device *dev, size_t size,
			 void *virt, dma_addr_t addr)
{
	struct dma_debug_entry ref = {
		.type           = dma_debug_coherent,
		.dev            = dev,
		.paddr          = virt_to_phys(virt),
		.dev_addr       = addr,
		.size           = size,
		.direction      = DMA_BIDIRECTIONAL,
	};

	if (unlikely(global_disable))
		return;

	check_unmap(&ref);
}
EXPORT_SYMBOL(debug_dma_free_coherent);

void debug_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
				   size_t size, int direction)
{
	struct dma_debug_entry ref;

	if (unlikely(global_disable))
		return;

	ref.type         = dma_debug_single;
	ref.dev          = dev;
	ref.dev_addr     = dma_handle;
	ref.size         = size;
	ref.direction    = direction;
	ref.sg_call_ents = 0;

	check_sync(dev, &ref, true);
}
EXPORT_SYMBOL(debug_dma_sync_single_for_cpu);

void debug_dma_sync_single_for_device(struct device *dev,
				      dma_addr_t dma_handle, size_t size,
				      int direction)
{
	struct dma_debug_entry ref;

	if (unlikely(global_disable))
		return;

	ref.type         = dma_debug_single;
	ref.dev          = dev;
	ref.dev_addr     = dma_handle;
	ref.size         = size;
	ref.direction    = direction;
	ref.sg_call_ents = 0;

	check_sync(dev, &ref, false);
}
EXPORT_SYMBOL(debug_dma_sync_single_for_device);

void debug_dma_sync_single_range_for_cpu(struct device *dev,
					 dma_addr_t dma_handle,
					 unsigned long offset, size_t size,
					 int direction)
{
	struct dma_debug_entry ref;

	if (unlikely(global_disable))
		return;

	ref.type         = dma_debug_single;
	ref.dev          = dev;
	ref.dev_addr     = dma_handle;
	ref.size         = offset + size;
	ref.direction    = direction;
	ref.sg_call_ents = 0;

	check_sync(dev, &ref, true);
}
EXPORT_SYMBOL(debug_dma_sync_single_range_for_cpu);

void debug_dma_sync_single_range_for_device(struct device *dev,
					    dma_addr_t dma_handle,
					    unsigned long offset,
					    size_t size, int direction)
{
	struct dma_debug_entry ref;

	if (unlikely(global_disable))
		return;

	ref.type         = dma_debug_single;
	ref.dev          = dev;
	ref.dev_addr     = dma_handle;
	ref.size         = offset + size;
	ref.direction    = direction;
	ref.sg_call_ents = 0;

	check_sync(dev, &ref, false);
}
EXPORT_SYMBOL(debug_dma_sync_single_range_for_device);

void debug_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
			       int nelems, int direction)
{
	struct scatterlist *s;
	int mapped_ents = 0, i;

	if (unlikely(global_disable))
		return;

	for_each_sg(sg, s, nelems, i) {

		struct dma_debug_entry ref = {
			.type           = dma_debug_sg,
			.dev            = dev,
			.paddr          = sg_phys(s),
			.dev_addr       = sg_dma_address(s),
			.size           = sg_dma_len(s),
			.direction      = direction,
			.sg_call_ents   = nelems,
		};

		if (!i)
			mapped_ents = get_nr_mapped_entries(dev, &ref);

		if (i >= mapped_ents)
			break;

		check_sync(dev, &ref, true);
	}
}
EXPORT_SYMBOL(debug_dma_sync_sg_for_cpu);

void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
				  int nelems, int direction)
{
	struct scatterlist *s;
	int mapped_ents = 0, i;

	if (unlikely(global_disable))
		return;

	for_each_sg(sg, s, nelems, i) {

		struct dma_debug_entry ref = {
			.type           = dma_debug_sg,
			.dev            = dev,
			.paddr          = sg_phys(s),
			.dev_addr       = sg_dma_address(s),
			.size           = sg_dma_len(s),
			.direction      = direction,
			.sg_call_ents   = nelems,
		};
		if (!i)
			mapped_ents = get_nr_mapped_entries(dev, &ref);

		if (i >= mapped_ents)
			break;

		check_sync(dev, &ref, false);
	}
}
EXPORT_SYMBOL(debug_dma_sync_sg_for_device);

static int __init dma_debug_driver_setup(char *str)
{
	int i;

	for (i = 0; i < NAME_MAX_LEN - 1; ++i, ++str) {
		current_driver_name[i] = *str;
		if (*str == 0)
			break;
	}

	if (current_driver_name[0])
		pr_info("DMA-API: enable driver filter for driver [%s]\n",
			current_driver_name);


	return 1;
}
__setup("dma_debug_driver=", dma_debug_driver_setup);