File: test_kmod.c

package info (click to toggle)
linux 4.19.20-1
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 954,852 kB
  • sloc: ansic: 16,749,828; asm: 271,286; makefile: 38,257; sh: 32,808; perl: 27,671; python: 21,022; cpp: 5,063; yacc: 4,648; lex: 2,585; awk: 1,385; ruby: 25; sed: 5
file content (1238 lines) | stat: -rw-r--r-- 30,680 bytes parent folder | download | duplicates (2)
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
/*
 * kmod stress test driver
 *
 * Copyright (C) 2017 Luis R. Rodriguez <mcgrof@kernel.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or at your option any
 * later version; or, when distributed separately from the Linux kernel or
 * when incorporated into other software packages, subject to the following
 * license:
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of copyleft-next (version 0.3.1 or later) as published
 * at http://copyleft-next.org/.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

/*
 * This driver provides an interface to trigger and test the kernel's
 * module loader through a series of configurations and a few triggers.
 * To test this driver use the following script as root:
 *
 * tools/testing/selftests/kmod/kmod.sh --help
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kmod.h>
#include <linux/printk.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/device.h>

#define TEST_START_NUM_THREADS	50
#define TEST_START_DRIVER	"test_module"
#define TEST_START_TEST_FS	"xfs"
#define TEST_START_TEST_CASE	TEST_KMOD_DRIVER


static bool force_init_test = false;
module_param(force_init_test, bool_enable_only, 0644);
MODULE_PARM_DESC(force_init_test,
		 "Force kicking a test immediately after driver loads");

/*
 * For device allocation / registration
 */
static DEFINE_MUTEX(reg_dev_mutex);
static LIST_HEAD(reg_test_devs);

/*
 * num_test_devs actually represents the *next* ID of the next
 * device we will allow to create.
 */
static int num_test_devs;

/**
 * enum kmod_test_case - linker table test case
 *
 * If you add a  test case, please be sure to review if you need to se
 * @need_mod_put for your tests case.
 *
 * @TEST_KMOD_DRIVER: stress tests request_module()
 * @TEST_KMOD_FS_TYPE: stress tests get_fs_type()
 */
enum kmod_test_case {
	__TEST_KMOD_INVALID = 0,

	TEST_KMOD_DRIVER,
	TEST_KMOD_FS_TYPE,

	__TEST_KMOD_MAX,
};

struct test_config {
	char *test_driver;
	char *test_fs;
	unsigned int num_threads;
	enum kmod_test_case test_case;
	int test_result;
};

struct kmod_test_device;

/**
 * kmod_test_device_info - thread info
 *
 * @ret_sync: return value if request_module() is used, sync request for
 * 	@TEST_KMOD_DRIVER
 * @fs_sync: return value of get_fs_type() for @TEST_KMOD_FS_TYPE
 * @thread_idx: thread ID
 * @test_dev: test device test is being performed under
 * @need_mod_put: Some tests (get_fs_type() is one) requires putting the module
 *	(module_put(fs_sync->owner)) when done, otherwise you will not be able
 *	to unload the respective modules and re-test. We use this to keep
 *	accounting of when we need this and to help out in case we need to
 *	error out and deal with module_put() on error.
 */
struct kmod_test_device_info {
	int ret_sync;
	struct file_system_type *fs_sync;
	struct task_struct *task_sync;
	unsigned int thread_idx;
	struct kmod_test_device *test_dev;
	bool need_mod_put;
};

/**
 * kmod_test_device - test device to help test kmod
 *
 * @dev_idx: unique ID for test device
 * @config: configuration for the test
 * @misc_dev: we use a misc device under the hood
 * @dev: pointer to misc_dev's own struct device
 * @config_mutex: protects configuration of test
 * @trigger_mutex: the test trigger can only be fired once at a time
 * @thread_lock: protects @done count, and the @info per each thread
 * @done: number of threads which have completed or failed
 * @test_is_oom: when we run out of memory, use this to halt moving forward
 * @kthreads_done: completion used to signal when all work is done
 * @list: needed to be part of the reg_test_devs
 * @info: array of info for each thread
 */
struct kmod_test_device {
	int dev_idx;
	struct test_config config;
	struct miscdevice misc_dev;
	struct device *dev;
	struct mutex config_mutex;
	struct mutex trigger_mutex;
	struct mutex thread_mutex;

	unsigned int done;

	bool test_is_oom;
	struct completion kthreads_done;
	struct list_head list;

	struct kmod_test_device_info *info;
};

static const char *test_case_str(enum kmod_test_case test_case)
{
	switch (test_case) {
	case TEST_KMOD_DRIVER:
		return "TEST_KMOD_DRIVER";
	case TEST_KMOD_FS_TYPE:
		return "TEST_KMOD_FS_TYPE";
	default:
		return "invalid";
	}
}

static struct miscdevice *dev_to_misc_dev(struct device *dev)
{
	return dev_get_drvdata(dev);
}

static struct kmod_test_device *misc_dev_to_test_dev(struct miscdevice *misc_dev)
{
	return container_of(misc_dev, struct kmod_test_device, misc_dev);
}

static struct kmod_test_device *dev_to_test_dev(struct device *dev)
{
	struct miscdevice *misc_dev;

	misc_dev = dev_to_misc_dev(dev);

	return misc_dev_to_test_dev(misc_dev);
}

/* Must run with thread_mutex held */
static void kmod_test_done_check(struct kmod_test_device *test_dev,
				 unsigned int idx)
{
	struct test_config *config = &test_dev->config;

	test_dev->done++;
	dev_dbg(test_dev->dev, "Done thread count: %u\n", test_dev->done);

	if (test_dev->done == config->num_threads) {
		dev_info(test_dev->dev, "Done: %u threads have all run now\n",
			 test_dev->done);
		dev_info(test_dev->dev, "Last thread to run: %u\n", idx);
		complete(&test_dev->kthreads_done);
	}
}

static void test_kmod_put_module(struct kmod_test_device_info *info)
{
	struct kmod_test_device *test_dev = info->test_dev;
	struct test_config *config = &test_dev->config;

	if (!info->need_mod_put)
		return;

	switch (config->test_case) {
	case TEST_KMOD_DRIVER:
		break;
	case TEST_KMOD_FS_TYPE:
		if (info && info->fs_sync && info->fs_sync->owner)
			module_put(info->fs_sync->owner);
		break;
	default:
		BUG();
	}

	info->need_mod_put = true;
}

static int run_request(void *data)
{
	struct kmod_test_device_info *info = data;
	struct kmod_test_device *test_dev = info->test_dev;
	struct test_config *config = &test_dev->config;

	switch (config->test_case) {
	case TEST_KMOD_DRIVER:
		info->ret_sync = request_module("%s", config->test_driver);
		break;
	case TEST_KMOD_FS_TYPE:
		info->fs_sync = get_fs_type(config->test_fs);
		info->need_mod_put = true;
		break;
	default:
		/* __trigger_config_run() already checked for test sanity */
		BUG();
		return -EINVAL;
	}

	dev_dbg(test_dev->dev, "Ran thread %u\n", info->thread_idx);

	test_kmod_put_module(info);

	mutex_lock(&test_dev->thread_mutex);
	info->task_sync = NULL;
	kmod_test_done_check(test_dev, info->thread_idx);
	mutex_unlock(&test_dev->thread_mutex);

	return 0;
}

static int tally_work_test(struct kmod_test_device_info *info)
{
	struct kmod_test_device *test_dev = info->test_dev;
	struct test_config *config = &test_dev->config;
	int err_ret = 0;

	switch (config->test_case) {
	case TEST_KMOD_DRIVER:
		/*
		 * Only capture errors, if one is found that's
		 * enough, for now.
		 */
		if (info->ret_sync != 0)
			err_ret = info->ret_sync;
		dev_info(test_dev->dev,
			 "Sync thread %d return status: %d\n",
			 info->thread_idx, info->ret_sync);
		break;
	case TEST_KMOD_FS_TYPE:
		/* For now we make this simple */
		if (!info->fs_sync)
			err_ret = -EINVAL;
		dev_info(test_dev->dev, "Sync thread %u fs: %s\n",
			 info->thread_idx, info->fs_sync ? config->test_fs :
			 "NULL");
		break;
	default:
		BUG();
	}

	return err_ret;
}

/*
 * XXX: add result option to display if all errors did not match.
 * For now we just keep any error code if one was found.
 *
 * If this ran it means *all* tasks were created fine and we
 * are now just collecting results.
 *
 * Only propagate errors, do not override with a subsequent sucess case.
 */
static void tally_up_work(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;
	struct kmod_test_device_info *info;
	unsigned int idx;
	int err_ret = 0;
	int ret = 0;

	mutex_lock(&test_dev->thread_mutex);

	dev_info(test_dev->dev, "Results:\n");

	for (idx=0; idx < config->num_threads; idx++) {
		info = &test_dev->info[idx];
		ret = tally_work_test(info);
		if (ret)
			err_ret = ret;
	}

	/*
	 * Note: request_module() returns 256 for a module not found even
	 * though modprobe itself returns 1.
	 */
	config->test_result = err_ret;

	mutex_unlock(&test_dev->thread_mutex);
}

static int try_one_request(struct kmod_test_device *test_dev, unsigned int idx)
{
	struct kmod_test_device_info *info = &test_dev->info[idx];
	int fail_ret = -ENOMEM;

	mutex_lock(&test_dev->thread_mutex);

	info->thread_idx = idx;
	info->test_dev = test_dev;
	info->task_sync = kthread_run(run_request, info, "%s-%u",
				      KBUILD_MODNAME, idx);

	if (!info->task_sync || IS_ERR(info->task_sync)) {
		test_dev->test_is_oom = true;
		dev_err(test_dev->dev, "Setting up thread %u failed\n", idx);
		info->task_sync = NULL;
		goto err_out;
	} else
		dev_dbg(test_dev->dev, "Kicked off thread %u\n", idx);

	mutex_unlock(&test_dev->thread_mutex);

	return 0;

err_out:
	info->ret_sync = fail_ret;
	mutex_unlock(&test_dev->thread_mutex);

	return fail_ret;
}

static void test_dev_kmod_stop_tests(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;
	struct kmod_test_device_info *info;
	unsigned int i;

	dev_info(test_dev->dev, "Ending request_module() tests\n");

	mutex_lock(&test_dev->thread_mutex);

	for (i=0; i < config->num_threads; i++) {
		info = &test_dev->info[i];
		if (info->task_sync && !IS_ERR(info->task_sync)) {
			dev_info(test_dev->dev,
				 "Stopping still-running thread %i\n", i);
			kthread_stop(info->task_sync);
		}

		/*
		 * info->task_sync is well protected, it can only be
		 * NULL or a pointer to a struct. If its NULL we either
		 * never ran, or we did and we completed the work. Completed
		 * tasks *always* put the module for us. This is a sanity
		 * check -- just in case.
		 */
		if (info->task_sync && info->need_mod_put)
			test_kmod_put_module(info);
	}

	mutex_unlock(&test_dev->thread_mutex);
}

/*
 * Only wait *iff* we did not run into any errors during all of our thread
 * set up. If run into any issues we stop threads and just bail out with
 * an error to the trigger. This also means we don't need any tally work
 * for any threads which fail.
 */
static int try_requests(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;
	unsigned int idx;
	int ret;
	bool any_error = false;

	for (idx=0; idx < config->num_threads; idx++) {
		if (test_dev->test_is_oom) {
			any_error = true;
			break;
		}

		ret = try_one_request(test_dev, idx);
		if (ret) {
			any_error = true;
			break;
		}
	}

	if (!any_error) {
		test_dev->test_is_oom = false;
		dev_info(test_dev->dev,
			 "No errors were found while initializing threads\n");
		wait_for_completion(&test_dev->kthreads_done);
		tally_up_work(test_dev);
	} else {
		test_dev->test_is_oom = true;
		dev_info(test_dev->dev,
			 "At least one thread failed to start, stop all work\n");
		test_dev_kmod_stop_tests(test_dev);
		return -ENOMEM;
	}

	return 0;
}

static int run_test_driver(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;

	dev_info(test_dev->dev, "Test case: %s (%u)\n",
		 test_case_str(config->test_case),
		 config->test_case);
	dev_info(test_dev->dev, "Test driver to load: %s\n",
		 config->test_driver);
	dev_info(test_dev->dev, "Number of threads to run: %u\n",
		 config->num_threads);
	dev_info(test_dev->dev, "Thread IDs will range from 0 - %u\n",
		 config->num_threads - 1);

	return try_requests(test_dev);
}

static int run_test_fs_type(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;

	dev_info(test_dev->dev, "Test case: %s (%u)\n",
		 test_case_str(config->test_case),
		 config->test_case);
	dev_info(test_dev->dev, "Test filesystem to load: %s\n",
		 config->test_fs);
	dev_info(test_dev->dev, "Number of threads to run: %u\n",
		 config->num_threads);
	dev_info(test_dev->dev, "Thread IDs will range from 0 - %u\n",
		 config->num_threads - 1);

	return try_requests(test_dev);
}

static ssize_t config_show(struct device *dev,
			   struct device_attribute *attr,
			   char *buf)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;
	int len = 0;

	mutex_lock(&test_dev->config_mutex);

	len += snprintf(buf, PAGE_SIZE,
			"Custom trigger configuration for: %s\n",
			dev_name(dev));

	len += snprintf(buf+len, PAGE_SIZE - len,
			"Number of threads:\t%u\n",
			config->num_threads);

	len += snprintf(buf+len, PAGE_SIZE - len,
			"Test_case:\t%s (%u)\n",
			test_case_str(config->test_case),
			config->test_case);

	if (config->test_driver)
		len += snprintf(buf+len, PAGE_SIZE - len,
				"driver:\t%s\n",
				config->test_driver);
	else
		len += snprintf(buf+len, PAGE_SIZE - len,
				"driver:\tEMPTY\n");

	if (config->test_fs)
		len += snprintf(buf+len, PAGE_SIZE - len,
				"fs:\t%s\n",
				config->test_fs);
	else
		len += snprintf(buf+len, PAGE_SIZE - len,
				"fs:\tEMPTY\n");

	mutex_unlock(&test_dev->config_mutex);

	return len;
}
static DEVICE_ATTR_RO(config);

/*
 * This ensures we don't allow kicking threads through if our configuration
 * is faulty.
 */
static int __trigger_config_run(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;

	test_dev->done = 0;

	switch (config->test_case) {
	case TEST_KMOD_DRIVER:
		return run_test_driver(test_dev);
	case TEST_KMOD_FS_TYPE:
		return run_test_fs_type(test_dev);
	default:
		dev_warn(test_dev->dev,
			 "Invalid test case requested: %u\n",
			 config->test_case);
		return -EINVAL;
	}
}

static int trigger_config_run(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;
	int ret;

	mutex_lock(&test_dev->trigger_mutex);
	mutex_lock(&test_dev->config_mutex);

	ret = __trigger_config_run(test_dev);
	if (ret < 0)
		goto out;
	dev_info(test_dev->dev, "General test result: %d\n",
		 config->test_result);

	/*
	 * We must return 0 after a trigger even unless something went
	 * wrong with the setup of the test. If the test setup went fine
	 * then userspace must just check the result of config->test_result.
	 * One issue with relying on the return from a call in the kernel
	 * is if the kernel returns a possitive value using this trigger
	 * will not return the value to userspace, it would be lost.
	 *
	 * By not relying on capturing the return value of tests we are using
	 * through the trigger it also us to run tests with set -e and only
	 * fail when something went wrong with the driver upon trigger
	 * requests.
	 */
	ret = 0;

out:
	mutex_unlock(&test_dev->config_mutex);
	mutex_unlock(&test_dev->trigger_mutex);

	return ret;
}

static ssize_t
trigger_config_store(struct device *dev,
		     struct device_attribute *attr,
		     const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	int ret;

	if (test_dev->test_is_oom)
		return -ENOMEM;

	/* For all intents and purposes we don't care what userspace
	 * sent this trigger, we care only that we were triggered.
	 * We treat the return value only for caputuring issues with
	 * the test setup. At this point all the test variables should
	 * have been allocated so typically this should never fail.
	 */
	ret = trigger_config_run(test_dev);
	if (unlikely(ret < 0))
		goto out;

	/*
	 * Note: any return > 0 will be treated as success
	 * and the error value will not be available to userspace.
	 * Do not rely on trying to send to userspace a test value
	 * return value as possitive return errors will be lost.
	 */
	if (WARN_ON(ret > 0))
		return -EINVAL;

	ret = count;
out:
	return ret;
}
static DEVICE_ATTR_WO(trigger_config);

/*
 * XXX: move to kstrncpy() once merged.
 *
 * Users should use kfree_const() when freeing these.
 */
static int __kstrncpy(char **dst, const char *name, size_t count, gfp_t gfp)
{
	*dst = kstrndup(name, count, gfp);
	if (!*dst)
		return -ENOSPC;
	return count;
}

static int config_copy_test_driver_name(struct test_config *config,
				    const char *name,
				    size_t count)
{
	return __kstrncpy(&config->test_driver, name, count, GFP_KERNEL);
}


static int config_copy_test_fs(struct test_config *config, const char *name,
			       size_t count)
{
	return __kstrncpy(&config->test_fs, name, count, GFP_KERNEL);
}

static void __kmod_config_free(struct test_config *config)
{
	if (!config)
		return;

	kfree_const(config->test_driver);
	config->test_driver = NULL;

	kfree_const(config->test_fs);
	config->test_driver = NULL;
}

static void kmod_config_free(struct kmod_test_device *test_dev)
{
	struct test_config *config;

	if (!test_dev)
		return;

	config = &test_dev->config;

	mutex_lock(&test_dev->config_mutex);
	__kmod_config_free(config);
	mutex_unlock(&test_dev->config_mutex);
}

static ssize_t config_test_driver_store(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;
	int copied;

	mutex_lock(&test_dev->config_mutex);

	kfree_const(config->test_driver);
	config->test_driver = NULL;

	copied = config_copy_test_driver_name(config, buf, count);
	mutex_unlock(&test_dev->config_mutex);

	return copied;
}

/*
 * As per sysfs_kf_seq_show() the buf is max PAGE_SIZE.
 */
static ssize_t config_test_show_str(struct mutex *config_mutex,
				    char *dst,
				    char *src)
{
	int len;

	mutex_lock(config_mutex);
	len = snprintf(dst, PAGE_SIZE, "%s\n", src);
	mutex_unlock(config_mutex);

	return len;
}

static ssize_t config_test_driver_show(struct device *dev,
					struct device_attribute *attr,
					char *buf)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return config_test_show_str(&test_dev->config_mutex, buf,
				    config->test_driver);
}
static DEVICE_ATTR_RW(config_test_driver);

static ssize_t config_test_fs_store(struct device *dev,
				    struct device_attribute *attr,
				    const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;
	int copied;

	mutex_lock(&test_dev->config_mutex);

	kfree_const(config->test_fs);
	config->test_fs = NULL;

	copied = config_copy_test_fs(config, buf, count);
	mutex_unlock(&test_dev->config_mutex);

	return copied;
}

static ssize_t config_test_fs_show(struct device *dev,
				   struct device_attribute *attr,
				   char *buf)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return config_test_show_str(&test_dev->config_mutex, buf,
				    config->test_fs);
}
static DEVICE_ATTR_RW(config_test_fs);

static int trigger_config_run_type(struct kmod_test_device *test_dev,
				   enum kmod_test_case test_case,
				   const char *test_str)
{
	int copied = 0;
	struct test_config *config = &test_dev->config;

	mutex_lock(&test_dev->config_mutex);

	switch (test_case) {
	case TEST_KMOD_DRIVER:
		kfree_const(config->test_driver);
		config->test_driver = NULL;
		copied = config_copy_test_driver_name(config, test_str,
						      strlen(test_str));
		break;
	case TEST_KMOD_FS_TYPE:
		kfree_const(config->test_fs);
		config->test_driver = NULL;
		copied = config_copy_test_fs(config, test_str,
					     strlen(test_str));
		break;
	default:
		mutex_unlock(&test_dev->config_mutex);
		return -EINVAL;
	}

	config->test_case = test_case;

	mutex_unlock(&test_dev->config_mutex);

	if (copied <= 0 || copied != strlen(test_str)) {
		test_dev->test_is_oom = true;
		return -ENOMEM;
	}

	test_dev->test_is_oom = false;

	return trigger_config_run(test_dev);
}

static void free_test_dev_info(struct kmod_test_device *test_dev)
{
	vfree(test_dev->info);
	test_dev->info = NULL;
}

static int kmod_config_sync_info(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;

	free_test_dev_info(test_dev);
	test_dev->info =
		vzalloc(array_size(sizeof(struct kmod_test_device_info),
				   config->num_threads));
	if (!test_dev->info)
		return -ENOMEM;

	return 0;
}

/*
 * Old kernels may not have this, if you want to port this code to
 * test it on older kernels.
 */
#ifdef get_kmod_umh_limit
static unsigned int kmod_init_test_thread_limit(void)
{
	return get_kmod_umh_limit();
}
#else
static unsigned int kmod_init_test_thread_limit(void)
{
	return TEST_START_NUM_THREADS;
}
#endif

static int __kmod_config_init(struct kmod_test_device *test_dev)
{
	struct test_config *config = &test_dev->config;
	int ret = -ENOMEM, copied;

	__kmod_config_free(config);

	copied = config_copy_test_driver_name(config, TEST_START_DRIVER,
					      strlen(TEST_START_DRIVER));
	if (copied != strlen(TEST_START_DRIVER))
		goto err_out;

	copied = config_copy_test_fs(config, TEST_START_TEST_FS,
				     strlen(TEST_START_TEST_FS));
	if (copied != strlen(TEST_START_TEST_FS))
		goto err_out;

	config->num_threads = kmod_init_test_thread_limit();
	config->test_result = 0;
	config->test_case = TEST_START_TEST_CASE;

	ret = kmod_config_sync_info(test_dev);
	if (ret)
		goto err_out;

	test_dev->test_is_oom = false;

	return 0;

err_out:
	test_dev->test_is_oom = true;
	WARN_ON(test_dev->test_is_oom);

	__kmod_config_free(config);

	return ret;
}

static ssize_t reset_store(struct device *dev,
			   struct device_attribute *attr,
			   const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	int ret;

	mutex_lock(&test_dev->trigger_mutex);
	mutex_lock(&test_dev->config_mutex);

	ret = __kmod_config_init(test_dev);
	if (ret < 0) {
		ret = -ENOMEM;
		dev_err(dev, "could not alloc settings for config trigger: %d\n",
		       ret);
		goto out;
	}

	dev_info(dev, "reset\n");
	ret = count;

out:
	mutex_unlock(&test_dev->config_mutex);
	mutex_unlock(&test_dev->trigger_mutex);

	return ret;
}
static DEVICE_ATTR_WO(reset);

static int test_dev_config_update_uint_sync(struct kmod_test_device *test_dev,
					    const char *buf, size_t size,
					    unsigned int *config,
					    int (*test_sync)(struct kmod_test_device *test_dev))
{
	int ret;
	unsigned long new;
	unsigned int old_val;

	ret = kstrtoul(buf, 10, &new);
	if (ret)
		return ret;

	if (new > UINT_MAX)
		return -EINVAL;

	mutex_lock(&test_dev->config_mutex);

	old_val = *config;
	*(unsigned int *)config = new;

	ret = test_sync(test_dev);
	if (ret) {
		*(unsigned int *)config = old_val;

		ret = test_sync(test_dev);
		WARN_ON(ret);

		mutex_unlock(&test_dev->config_mutex);
		return -EINVAL;
	}

	mutex_unlock(&test_dev->config_mutex);
	/* Always return full write size even if we didn't consume all */
	return size;
}

static int test_dev_config_update_uint_range(struct kmod_test_device *test_dev,
					     const char *buf, size_t size,
					     unsigned int *config,
					     unsigned int min,
					     unsigned int max)
{
	int ret;
	unsigned long new;

	ret = kstrtoul(buf, 10, &new);
	if (ret)
		return ret;

	if (new < min || new > max)
		return -EINVAL;

	mutex_lock(&test_dev->config_mutex);
	*config = new;
	mutex_unlock(&test_dev->config_mutex);

	/* Always return full write size even if we didn't consume all */
	return size;
}

static int test_dev_config_update_int(struct kmod_test_device *test_dev,
				      const char *buf, size_t size,
				      int *config)
{
	int ret;
	long new;

	ret = kstrtol(buf, 10, &new);
	if (ret)
		return ret;

	if (new < INT_MIN || new > INT_MAX)
		return -EINVAL;

	mutex_lock(&test_dev->config_mutex);
	*config = new;
	mutex_unlock(&test_dev->config_mutex);
	/* Always return full write size even if we didn't consume all */
	return size;
}

static ssize_t test_dev_config_show_int(struct kmod_test_device *test_dev,
					char *buf,
					int config)
{
	int val;

	mutex_lock(&test_dev->config_mutex);
	val = config;
	mutex_unlock(&test_dev->config_mutex);

	return snprintf(buf, PAGE_SIZE, "%d\n", val);
}

static ssize_t test_dev_config_show_uint(struct kmod_test_device *test_dev,
					 char *buf,
					 unsigned int config)
{
	unsigned int val;

	mutex_lock(&test_dev->config_mutex);
	val = config;
	mutex_unlock(&test_dev->config_mutex);

	return snprintf(buf, PAGE_SIZE, "%u\n", val);
}

static ssize_t test_result_store(struct device *dev,
				 struct device_attribute *attr,
				 const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return test_dev_config_update_int(test_dev, buf, count,
					  &config->test_result);
}

static ssize_t config_num_threads_store(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return test_dev_config_update_uint_sync(test_dev, buf, count,
						&config->num_threads,
						kmod_config_sync_info);
}

static ssize_t config_num_threads_show(struct device *dev,
				       struct device_attribute *attr,
				       char *buf)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return test_dev_config_show_int(test_dev, buf, config->num_threads);
}
static DEVICE_ATTR_RW(config_num_threads);

static ssize_t config_test_case_store(struct device *dev,
				      struct device_attribute *attr,
				      const char *buf, size_t count)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return test_dev_config_update_uint_range(test_dev, buf, count,
						 &config->test_case,
						 __TEST_KMOD_INVALID + 1,
						 __TEST_KMOD_MAX - 1);
}

static ssize_t config_test_case_show(struct device *dev,
				     struct device_attribute *attr,
				     char *buf)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return test_dev_config_show_uint(test_dev, buf, config->test_case);
}
static DEVICE_ATTR_RW(config_test_case);

static ssize_t test_result_show(struct device *dev,
				struct device_attribute *attr,
				char *buf)
{
	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
	struct test_config *config = &test_dev->config;

	return test_dev_config_show_int(test_dev, buf, config->test_result);
}
static DEVICE_ATTR_RW(test_result);

#define TEST_KMOD_DEV_ATTR(name)		&dev_attr_##name.attr

static struct attribute *test_dev_attrs[] = {
	TEST_KMOD_DEV_ATTR(trigger_config),
	TEST_KMOD_DEV_ATTR(config),
	TEST_KMOD_DEV_ATTR(reset),

	TEST_KMOD_DEV_ATTR(config_test_driver),
	TEST_KMOD_DEV_ATTR(config_test_fs),
	TEST_KMOD_DEV_ATTR(config_num_threads),
	TEST_KMOD_DEV_ATTR(config_test_case),
	TEST_KMOD_DEV_ATTR(test_result),

	NULL,
};

ATTRIBUTE_GROUPS(test_dev);

static int kmod_config_init(struct kmod_test_device *test_dev)
{
	int ret;

	mutex_lock(&test_dev->config_mutex);
	ret = __kmod_config_init(test_dev);
	mutex_unlock(&test_dev->config_mutex);

	return ret;
}

static struct kmod_test_device *alloc_test_dev_kmod(int idx)
{
	int ret;
	struct kmod_test_device *test_dev;
	struct miscdevice *misc_dev;

	test_dev = vzalloc(sizeof(struct kmod_test_device));
	if (!test_dev)
		goto err_out;

	mutex_init(&test_dev->config_mutex);
	mutex_init(&test_dev->trigger_mutex);
	mutex_init(&test_dev->thread_mutex);

	init_completion(&test_dev->kthreads_done);

	ret = kmod_config_init(test_dev);
	if (ret < 0) {
		pr_err("Cannot alloc kmod_config_init()\n");
		goto err_out_free;
	}

	test_dev->dev_idx = idx;
	misc_dev = &test_dev->misc_dev;

	misc_dev->minor = MISC_DYNAMIC_MINOR;
	misc_dev->name = kasprintf(GFP_KERNEL, "test_kmod%d", idx);
	if (!misc_dev->name) {
		pr_err("Cannot alloc misc_dev->name\n");
		goto err_out_free_config;
	}
	misc_dev->groups = test_dev_groups;

	return test_dev;

err_out_free_config:
	free_test_dev_info(test_dev);
	kmod_config_free(test_dev);
err_out_free:
	vfree(test_dev);
	test_dev = NULL;
err_out:
	return NULL;
}

static void free_test_dev_kmod(struct kmod_test_device *test_dev)
{
	if (test_dev) {
		kfree_const(test_dev->misc_dev.name);
		test_dev->misc_dev.name = NULL;
		free_test_dev_info(test_dev);
		kmod_config_free(test_dev);
		vfree(test_dev);
		test_dev = NULL;
	}
}

static struct kmod_test_device *register_test_dev_kmod(void)
{
	struct kmod_test_device *test_dev = NULL;
	int ret;

	mutex_lock(&reg_dev_mutex);

	/* int should suffice for number of devices, test for wrap */
	if (num_test_devs + 1 == INT_MAX) {
		pr_err("reached limit of number of test devices\n");
		goto out;
	}

	test_dev = alloc_test_dev_kmod(num_test_devs);
	if (!test_dev)
		goto out;

	ret = misc_register(&test_dev->misc_dev);
	if (ret) {
		pr_err("could not register misc device: %d\n", ret);
		free_test_dev_kmod(test_dev);
		goto out;
	}

	test_dev->dev = test_dev->misc_dev.this_device;
	list_add_tail(&test_dev->list, &reg_test_devs);
	dev_info(test_dev->dev, "interface ready\n");

	num_test_devs++;

out:
	mutex_unlock(&reg_dev_mutex);

	return test_dev;

}

static int __init test_kmod_init(void)
{
	struct kmod_test_device *test_dev;
	int ret;

	test_dev = register_test_dev_kmod();
	if (!test_dev) {
		pr_err("Cannot add first test kmod device\n");
		return -ENODEV;
	}

	/*
	 * With some work we might be able to gracefully enable
	 * testing with this driver built-in, for now this seems
	 * rather risky. For those willing to try have at it,
	 * and enable the below. Good luck! If that works, try
	 * lowering the init level for more fun.
	 */
	if (force_init_test) {
		ret = trigger_config_run_type(test_dev,
					      TEST_KMOD_DRIVER, "tun");
		if (WARN_ON(ret))
			return ret;
		ret = trigger_config_run_type(test_dev,
					      TEST_KMOD_FS_TYPE, "btrfs");
		if (WARN_ON(ret))
			return ret;
	}

	return 0;
}
late_initcall(test_kmod_init);

static
void unregister_test_dev_kmod(struct kmod_test_device *test_dev)
{
	mutex_lock(&test_dev->trigger_mutex);
	mutex_lock(&test_dev->config_mutex);

	test_dev_kmod_stop_tests(test_dev);

	dev_info(test_dev->dev, "removing interface\n");
	misc_deregister(&test_dev->misc_dev);

	mutex_unlock(&test_dev->config_mutex);
	mutex_unlock(&test_dev->trigger_mutex);

	free_test_dev_kmod(test_dev);
}

static void __exit test_kmod_exit(void)
{
	struct kmod_test_device *test_dev, *tmp;

	mutex_lock(&reg_dev_mutex);
	list_for_each_entry_safe(test_dev, tmp, &reg_test_devs, list) {
		list_del(&test_dev->list);
		unregister_test_dev_kmod(test_dev);
	}
	mutex_unlock(&reg_dev_mutex);
}
module_exit(test_kmod_exit);

MODULE_AUTHOR("Luis R. Rodriguez <mcgrof@kernel.org>");
MODULE_LICENSE("GPL");