summaryrefslogtreecommitdiffstats
path: root/kernel/kcsan/kcsan-test.c
blob: 8a8ccaf4f38f30d478e0d3fb32812846e44254b3 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * KCSAN test with various race scenarious to test runtime behaviour. Since the
 * interface with which KCSAN's reports are obtained is via the console, this is
 * the output we should verify. For each test case checks the presence (or
 * absence) of generated reports. Relies on 'console' tracepoint to capture
 * reports as they appear in the kernel log.
 *
 * Makes use of KUnit for test organization, and the Torture framework for test
 * thread control.
 *
 * Copyright (C) 2020, Google LLC.
 * Author: Marco Elver <elver@google.com>
 */

#include <kunit/test.h>
#include <linux/jiffies.h>
#include <linux/kcsan-checks.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/seqlock.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/torture.h>
#include <linux/tracepoint.h>
#include <linux/types.h>
#include <trace/events/printk.h>

#ifdef CONFIG_CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE
#define __KCSAN_ACCESS_RW(alt) (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE)
#else
#define __KCSAN_ACCESS_RW(alt) (alt)
#endif

/* Points to current test-case memory access "kernels". */
static void (*access_kernels[2])(void);

static struct task_struct **threads; /* Lists of threads. */
static unsigned long end_time;       /* End time of test. */

/* Report as observed from console. */
static struct {
	spinlock_t lock;
	int nlines;
	char lines[3][512];
} observed = {
	.lock = __SPIN_LOCK_UNLOCKED(observed.lock),
};

/* Setup test checking loop. */
static __no_kcsan inline void
begin_test_checks(void (*func1)(void), void (*func2)(void))
{
	kcsan_disable_current();

	/*
	 * Require at least as long as KCSAN_REPORT_ONCE_IN_MS, to ensure at
	 * least one race is reported.
	 */
	end_time = jiffies + msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS + 500);

	/* Signal start; release potential initialization of shared data. */
	smp_store_release(&access_kernels[0], func1);
	smp_store_release(&access_kernels[1], func2);
}

/* End test checking loop. */
static __no_kcsan inline bool
end_test_checks(bool stop)
{
	if (!stop && time_before(jiffies, end_time)) {
		/* Continue checking */
		might_sleep();
		return false;
	}

	kcsan_enable_current();
	return true;
}

/*
 * Probe for console output: checks if a race was reported, and obtains observed
 * lines of interest.
 */
__no_kcsan
static void probe_console(void *ignore, const char *buf, size_t len)
{
	unsigned long flags;
	int nlines;

	/*
	 * Note that KCSAN reports under a global lock, so we do not risk the
	 * possibility of having multiple reports interleaved. If that were the
	 * case, we'd expect tests to fail.
	 */

	spin_lock_irqsave(&observed.lock, flags);
	nlines = observed.nlines;

	if (strnstr(buf, "BUG: KCSAN: ", len) && strnstr(buf, "test_", len)) {
		/*
		 * KCSAN report and related to the test.
		 *
		 * The provided @buf is not NUL-terminated; copy no more than
		 * @len bytes and let strscpy() add the missing NUL-terminator.
		 */
		strscpy(observed.lines[0], buf, min(len + 1, sizeof(observed.lines[0])));
		nlines = 1;
	} else if ((nlines == 1 || nlines == 2) && strnstr(buf, "bytes by", len)) {
		strscpy(observed.lines[nlines++], buf, min(len + 1, sizeof(observed.lines[0])));

		if (strnstr(buf, "race at unknown origin", len)) {
			if (WARN_ON(nlines != 2))
				goto out;

			/* No second line of interest. */
			strcpy(observed.lines[nlines++], "<none>");
		}
	}

out:
	WRITE_ONCE(observed.nlines, nlines); /* Publish new nlines. */
	spin_unlock_irqrestore(&observed.lock, flags);
}

/* Check if a report related to the test exists. */
__no_kcsan
static bool report_available(void)
{
	return READ_ONCE(observed.nlines) == ARRAY_SIZE(observed.lines);
}

/* Report information we expect in a report. */
struct expect_report {
	/* Access information of both accesses. */
	struct {
		void *fn;    /* Function pointer to expected function of top frame. */
		void *addr;  /* Address of access; unchecked if NULL. */
		size_t size; /* Size of access; unchecked if @addr is NULL. */
		int type;    /* Access type, see KCSAN_ACCESS definitions. */
	} access[2];
};

/* Check observed report matches information in @r. */
__no_kcsan
static bool report_matches(const struct expect_report *r)
{
	const bool is_assert = (r->access[0].type | r->access[1].type) & KCSAN_ACCESS_ASSERT;
	bool ret = false;
	unsigned long flags;
	typeof(*observed.lines) *expect;
	const char *end;
	char *cur;
	int i;

	/* Doubled-checked locking. */
	if (!report_available())
		return false;

	expect = kmalloc(sizeof(observed.lines), GFP_KERNEL);
	if (WARN_ON(!expect))
		return false;

	/* Generate expected report contents. */

	/* Title */
	cur = expect[0];
	end = &expect[0][sizeof(expect[0]) - 1];
	cur += scnprintf(cur, end - cur, "BUG: KCSAN: %s in ",
			 is_assert ? "assert: race" : "data-race");
	if (r->access[1].fn) {
		char tmp[2][64];
		int cmp;

		/* Expect lexographically sorted function names in title. */
		scnprintf(tmp[0], sizeof(tmp[0]), "%pS", r->access[0].fn);
		scnprintf(tmp[1], sizeof(tmp[1]), "%pS", r->access[1].fn);
		cmp = strcmp(tmp[0], tmp[1]);
		cur += scnprintf(cur, end - cur, "%ps / %ps",
				 cmp < 0 ? r->access[0].fn : r->access[1].fn,
				 cmp < 0 ? r->access[1].fn : r->access[0].fn);
	} else {
		scnprintf(cur, end - cur, "%pS", r->access[0].fn);
		/* The exact offset won't match, remove it. */
		cur = strchr(expect[0], '+');
		if (cur)
			*cur = '\0';
	}

	/* Access 1 */
	cur = expect[1];
	end = &expect[1][sizeof(expect[1]) - 1];
	if (!r->access[1].fn)
		cur += scnprintf(cur, end - cur, "race at unknown origin, with ");

	/* Access 1 & 2 */
	for (i = 0; i < 2; ++i) {
		const int ty = r->access[i].type;
		const char *const access_type =
			(ty & KCSAN_ACCESS_ASSERT) ?
				      ((ty & KCSAN_ACCESS_WRITE) ?
					       "assert no accesses" :
					       "assert no writes") :
				      ((ty & KCSAN_ACCESS_WRITE) ?
					       ((ty & KCSAN_ACCESS_COMPOUND) ?
							"read-write" :
							"write") :
					       "read");
		const char *const access_type_aux =
			(ty & KCSAN_ACCESS_ATOMIC) ?
				      " (marked)" :
				      ((ty & KCSAN_ACCESS_SCOPED) ? " (scoped)" : "");

		if (i == 1) {
			/* Access 2 */
			cur = expect[2];
			end = &expect[2][sizeof(expect[2]) - 1];

			if (!r->access[1].fn) {
				/* Dummy string if no second access is available. */
				strcpy(cur, "<none>");
				break;
			}
		}

		cur += scnprintf(cur, end - cur, "%s%s to ", access_type,
				 access_type_aux);

		if (r->access[i].addr) /* Address is optional. */
			cur += scnprintf(cur, end - cur, "0x%px of %zu bytes",
					 r->access[i].addr, r->access[i].size);
	}

	spin_lock_irqsave(&observed.lock, flags);
	if (!report_available())
		goto out; /* A new report is being captured. */

	/* Finally match expected output to what we actually observed. */
	ret = strstr(observed.lines[0], expect[0]) &&
	      /* Access info may appear in any order. */
	      ((strstr(observed.lines[1], expect[1]) &&
		strstr(observed.lines[2], expect[2])) ||
	       (strstr(observed.lines[1], expect[2]) &&
		strstr(observed.lines[2], expect[1])));
out:
	spin_unlock_irqrestore(&observed.lock, flags);
	kfree(expect);
	return ret;
}

/* ===== Test kernels ===== */

static long test_sink;
static long test_var;
/* @test_array should be large enough to fall into multiple watchpoint slots. */
static long test_array[3 * PAGE_SIZE / sizeof(long)];
static struct {
	long val[8];
} test_struct;
static DEFINE_SEQLOCK(test_seqlock);

/*
 * Helper to avoid compiler optimizing out reads, and to generate source values
 * for writes.
 */
__no_kcsan
static noinline void sink_value(long v) { WRITE_ONCE(test_sink, v); }

static noinline void test_kernel_read(void) { sink_value(test_var); }

static noinline void test_kernel_write(void)
{
	test_var = READ_ONCE_NOCHECK(test_sink) + 1;
}

static noinline void test_kernel_write_nochange(void) { test_var = 42; }

/* Suffixed by value-change exception filter. */
static noinline void test_kernel_write_nochange_rcu(void) { test_var = 42; }

static noinline void test_kernel_read_atomic(void)
{
	sink_value(READ_ONCE(test_var));
}

static noinline void test_kernel_write_atomic(void)
{
	WRITE_ONCE(test_var, READ_ONCE_NOCHECK(test_sink) + 1);
}

static noinline void test_kernel_atomic_rmw(void)
{
	/* Use builtin, so we can set up the "bad" atomic/non-atomic scenario. */
	__atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED);
}

__no_kcsan
static noinline void test_kernel_write_uninstrumented(void) { test_var++; }

static noinline void test_kernel_data_race(void) { data_race(test_var++); }

static noinline void test_kernel_assert_writer(void)
{
	ASSERT_EXCLUSIVE_WRITER(test_var);
}

static noinline void test_kernel_assert_access(void)
{
	ASSERT_EXCLUSIVE_ACCESS(test_var);
}

#define TEST_CHANGE_BITS 0xff00ff00

static noinline void test_kernel_change_bits(void)
{
	if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
		/*
		 * Avoid race of unknown origin for this test, just pretend they
		 * are atomic.
		 */
		kcsan_nestable_atomic_begin();
		test_var ^= TEST_CHANGE_BITS;
		kcsan_nestable_atomic_end();
	} else
		WRITE_ONCE(test_var, READ_ONCE(test_var) ^ TEST_CHANGE_BITS);
}

static noinline void test_kernel_assert_bits_change(void)
{
	ASSERT_EXCLUSIVE_BITS(test_var, TEST_CHANGE_BITS);
}

static noinline void test_kernel_assert_bits_nochange(void)
{
	ASSERT_EXCLUSIVE_BITS(test_var, ~TEST_CHANGE_BITS);
}

/* To check that scoped assertions do trigger anywhere in scope. */
static noinline void test_enter_scope(void)
{
	int x = 0;

	/* Unrelated accesses to scoped assert. */
	READ_ONCE(test_sink);
	kcsan_check_read(&x, sizeof(x));
}

static noinline void test_kernel_assert_writer_scoped(void)
{
	ASSERT_EXCLUSIVE_WRITER_SCOPED(test_var);
	test_enter_scope();
}

static noinline void test_kernel_assert_access_scoped(void)
{
	ASSERT_EXCLUSIVE_ACCESS_SCOPED(test_var);
	test_enter_scope();
}

static noinline void test_kernel_rmw_array(void)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(test_array); ++i)
		test_array[i]++;
}

static noinline void test_kernel_write_struct(void)
{
	kcsan_check_write(&test_struct, sizeof(test_struct));
	kcsan_disable_current();
	test_struct.val[3]++; /* induce value change */
	kcsan_enable_current();
}

static noinline void test_kernel_write_struct_part(void)
{
	test_struct.val[3] = 42;
}

static noinline void test_kernel_read_struct_zero_size(void)
{
	kcsan_check_read(&test_struct.val[3], 0);
}

static noinline void test_kernel_jiffies_reader(void)
{
	sink_value((long)jiffies);
}

static noinline void test_kernel_seqlock_reader(void)
{
	unsigned int seq;

	do {
		seq = read_seqbegin(&test_seqlock);
		sink_value(test_var);
	} while (read_seqretry(&test_seqlock, seq));
}

static noinline void test_kernel_seqlock_writer(void)
{
	unsigned long flags;

	write_seqlock_irqsave(&test_seqlock, flags);
	test_var++;
	write_sequnlock_irqrestore(&test_seqlock, flags);
}

static noinline void test_kernel_atomic_builtins(void)
{
	/*
	 * Generate concurrent accesses, expecting no reports, ensuring KCSAN
	 * treats builtin atomics as actually atomic.
	 */
	__atomic_load_n(&test_var, __ATOMIC_RELAXED);
}

/* ===== Test cases ===== */

/* Simple test with normal data race. */
__no_kcsan
static void test_basic(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	static const struct expect_report never = {
		.access = {
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	bool match_expect = false;
	bool match_never = false;

	begin_test_checks(test_kernel_write, test_kernel_read);
	do {
		match_expect |= report_matches(&expect);
		match_never = report_matches(&never);
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_TRUE(test, match_expect);
	KUNIT_EXPECT_FALSE(test, match_never);
}

/*
 * Stress KCSAN with lots of concurrent races on different addresses until
 * timeout.
 */
__no_kcsan
static void test_concurrent_races(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			/* NULL will match any address. */
			{ test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
			{ test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(0) },
		},
	};
	static const struct expect_report never = {
		.access = {
			{ test_kernel_rmw_array, NULL, 0, 0 },
			{ test_kernel_rmw_array, NULL, 0, 0 },
		},
	};
	bool match_expect = false;
	bool match_never = false;

	begin_test_checks(test_kernel_rmw_array, test_kernel_rmw_array);
	do {
		match_expect |= report_matches(&expect);
		match_never |= report_matches(&never);
	} while (!end_test_checks(false));
	KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check matches exist. */
	KUNIT_EXPECT_FALSE(test, match_never);
}

/* Test the KCSAN_REPORT_VALUE_CHANGE_ONLY option. */
__no_kcsan
static void test_novalue_change(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_write_nochange, test_kernel_read);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY))
		KUNIT_EXPECT_FALSE(test, match_expect);
	else
		KUNIT_EXPECT_TRUE(test, match_expect);
}

/*
 * Test that the rules where the KCSAN_REPORT_VALUE_CHANGE_ONLY option should
 * never apply work.
 */
__no_kcsan
static void test_novalue_change_exception(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

/* Test that data races of unknown origin are reported. */
__no_kcsan
static void test_unknown_origin(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
			{ NULL },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_write_uninstrumented, test_kernel_read);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
		KUNIT_EXPECT_TRUE(test, match_expect);
	else
		KUNIT_EXPECT_FALSE(test, match_expect);
}

/* Test KCSAN_ASSUME_PLAIN_WRITES_ATOMIC if it is selected. */
__no_kcsan
static void test_write_write_assume_atomic(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
			{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_write, test_kernel_write);
	do {
		sink_value(READ_ONCE(test_var)); /* induce value-change */
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC))
		KUNIT_EXPECT_FALSE(test, match_expect);
	else
		KUNIT_EXPECT_TRUE(test, match_expect);
}

/*
 * Test that data races with writes larger than word-size are always reported,
 * even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
 */
__no_kcsan
static void test_write_write_struct(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_write_struct, test_kernel_write_struct);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

/*
 * Test that data races where only one write is larger than word-size are always
 * reported, even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
 */
__no_kcsan
static void test_write_write_struct_part(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
			{ test_kernel_write_struct_part, &test_struct.val[3], sizeof(test_struct.val[3]), KCSAN_ACCESS_WRITE },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_write_struct, test_kernel_write_struct_part);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

/* Test that races with atomic accesses never result in reports. */
__no_kcsan
static void test_read_atomic_write_atomic(struct kunit *test)
{
	bool match_never = false;

	begin_test_checks(test_kernel_read_atomic, test_kernel_write_atomic);
	do {
		match_never = report_available();
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_FALSE(test, match_never);
}

/* Test that a race with an atomic and plain access result in reports. */
__no_kcsan
static void test_read_plain_atomic_write(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
			{ test_kernel_write_atomic, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
		},
	};
	bool match_expect = false;

	if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
		return;

	begin_test_checks(test_kernel_read, test_kernel_write_atomic);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

/* Test that atomic RMWs generate correct report. */
__no_kcsan
static void test_read_plain_atomic_rmw(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
			{ test_kernel_atomic_rmw, &test_var, sizeof(test_var),
				KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
		},
	};
	bool match_expect = false;

	if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
		return;

	begin_test_checks(test_kernel_read, test_kernel_atomic_rmw);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

/* Zero-sized accesses should never cause data race reports. */
__no_kcsan
static void test_zero_size_access(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
		},
	};
	const struct expect_report never = {
		.access = {
			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
			{ test_kernel_read_struct_zero_size, &test_struct.val[3], 0, 0 },
		},
	};
	bool match_expect = false;
	bool match_never = false;

	begin_test_checks(test_kernel_write_struct, test_kernel_read_struct_zero_size);
	do {
		match_expect |= report_matches(&expect);
		match_never = report_matches(&never);
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check. */
	KUNIT_EXPECT_FALSE(test, match_never);
}

/* Test the data_race() macro. */
__no_kcsan
static void test_data_race(struct kunit *test)
{
	bool match_never = false;

	begin_test_checks(test_kernel_data_race, test_kernel_data_race);
	do {
		match_never = report_available();
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_FALSE(test, match_never);
}

__no_kcsan
static void test_assert_exclusive_writer(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_assert_writer, test_kernel_write_nochange);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

__no_kcsan
static void test_assert_exclusive_access(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_assert_access, test_kernel_read);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

__no_kcsan
static void test_assert_exclusive_access_writer(struct kunit *test)
{
	const struct expect_report expect_access_writer = {
		.access = {
			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
		},
	};
	const struct expect_report expect_access_access = {
		.access = {
			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
		},
	};
	const struct expect_report never = {
		.access = {
			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
		},
	};
	bool match_expect_access_writer = false;
	bool match_expect_access_access = false;
	bool match_never = false;

	begin_test_checks(test_kernel_assert_access, test_kernel_assert_writer);
	do {
		match_expect_access_writer |= report_matches(&expect_access_writer);
		match_expect_access_access |= report_matches(&expect_access_access);
		match_never |= report_matches(&never);
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_TRUE(test, match_expect_access_writer);
	KUNIT_EXPECT_TRUE(test, match_expect_access_access);
	KUNIT_EXPECT_FALSE(test, match_never);
}

__no_kcsan
static void test_assert_exclusive_bits_change(struct kunit *test)
{
	const struct expect_report expect = {
		.access = {
			{ test_kernel_assert_bits_change, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
			{ test_kernel_change_bits, &test_var, sizeof(test_var),
				KCSAN_ACCESS_WRITE | (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) ? 0 : KCSAN_ACCESS_ATOMIC) },
		},
	};
	bool match_expect = false;

	begin_test_checks(test_kernel_assert_bits_change, test_kernel_change_bits);
	do {
		match_expect = report_matches(&expect);
	} while (!end_test_checks(match_expect));
	KUNIT_EXPECT_TRUE(test, match_expect);
}

__no_kcsan
static void test_assert_exclusive_bits_nochange(struct kunit *test)
{
	bool match_never = false;

	begin_test_checks(test_kernel_assert_bits_nochange, test_kernel_change_bits);
	do {
		match_never = report_available();
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_FALSE(test, match_never);
}

__no_kcsan
static void test_assert_exclusive_writer_scoped(struct kunit *test)
{
	const struct expect_report expect_start = {
		.access = {
			{ test_kernel_assert_writer_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
		},
	};
	const struct expect_report expect_anywhere = {
		.access = {
			{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
		},
	};
	bool match_expect_start = false;
	bool match_expect_anywhere = false;

	begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange);
	do {
		match_expect_start |= report_matches(&expect_start);
		match_expect_anywhere |= report_matches(&expect_anywhere);
	} while (!end_test_checks(match_expect_start && match_expect_anywhere));
	KUNIT_EXPECT_TRUE(test, match_expect_start);
	KUNIT_EXPECT_TRUE(test, match_expect_anywhere);
}

__no_kcsan
static void test_assert_exclusive_access_scoped(struct kunit *test)
{
	const struct expect_report expect_start1 = {
		.access = {
			{ test_kernel_assert_access_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	const struct expect_report expect_start2 = {
		.access = { expect_start1.access[0], expect_start1.access[0] },
	};
	const struct expect_report expect_inscope = {
		.access = {
			{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
		},
	};
	bool match_expect_start = false;
	bool match_expect_inscope = false;

	begin_test_checks(test_kernel_assert_access_scoped, test_kernel_read);
	end_time += msecs_to_jiffies(1000); /* This test requires a bit more time. */
	do {
		match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2);
		match_expect_inscope |= report_matches(&expect_inscope);
	} while (!end_test_checks(match_expect_start && match_expect_inscope));
	KUNIT_EXPECT_TRUE(test, match_expect_start);
	KUNIT_EXPECT_TRUE(test, match_expect_inscope);
}

/*
 * jiffies is special (declared to be volatile) and its accesses are typically
 * not marked; this test ensures that the compiler nor KCSAN gets confused about
 * jiffies's declaration on different architectures.
 */
__no_kcsan
static void test_jiffies_noreport(struct kunit *test)
{
	bool match_never = false;

	begin_test_checks(test_kernel_jiffies_reader, test_kernel_jiffies_reader);
	do {
		match_never = report_available();
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_FALSE(test, match_never);
}

/* Test that racing accesses in seqlock critical sections are not reported. */
__no_kcsan
static void test_seqlock_noreport(struct kunit *test)
{
	bool match_never = false;

	begin_test_checks(test_kernel_seqlock_reader, test_kernel_seqlock_writer);
	do {
		match_never = report_available();
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_FALSE(test, match_never);
}

/*
 * Test atomic builtins work and required instrumentation functions exist. We
 * also test that KCSAN understands they're atomic by racing with them via
 * test_kernel_atomic_builtins(), and expect no reports.
 *
 * The atomic builtins _SHOULD NOT_ be used in normal kernel code!
 */
static void test_atomic_builtins(struct kunit *test)
{
	bool match_never = false;

	begin_test_checks(test_kernel_atomic_builtins, test_kernel_atomic_builtins);
	do {
		long tmp;

		kcsan_enable_current();

		__atomic_store_n(&test_var, 42L, __ATOMIC_RELAXED);
		KUNIT_EXPECT_EQ(test, 42L, __atomic_load_n(&test_var, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, 42L, __atomic_exchange_n(&test_var, 20, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, 20L, test_var);

		tmp = 20L;
		KUNIT_EXPECT_TRUE(test, __atomic_compare_exchange_n(&test_var, &tmp, 30L,
								    0, __ATOMIC_RELAXED,
								    __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, tmp, 20L);
		KUNIT_EXPECT_EQ(test, test_var, 30L);
		KUNIT_EXPECT_FALSE(test, __atomic_compare_exchange_n(&test_var, &tmp, 40L,
								     1, __ATOMIC_RELAXED,
								     __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, tmp, 30L);
		KUNIT_EXPECT_EQ(test, test_var, 30L);

		KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, 31L, __atomic_fetch_sub(&test_var, 1, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_and(&test_var, 0xf, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, 14L, __atomic_fetch_xor(&test_var, 0xf, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, 1L, __atomic_fetch_or(&test_var, 0xf0, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, 241L, __atomic_fetch_nand(&test_var, 0xf, __ATOMIC_RELAXED));
		KUNIT_EXPECT_EQ(test, -2L, test_var);

		__atomic_thread_fence(__ATOMIC_SEQ_CST);
		__atomic_signal_fence(__ATOMIC_SEQ_CST);

		kcsan_disable_current();

		match_never = report_available();
	} while (!end_test_checks(match_never));
	KUNIT_EXPECT_FALSE(test, match_never);
}

/*
 * Each test case is run with different numbers of threads. Until KUnit supports
 * passing arguments for each test case, we encode #threads in the test case
 * name (read by get_num_threads()). [The '-' was chosen as a stylistic
 * preference to separate test name and #threads.]
 *
 * The thread counts are chosen to cover potentially interesting boundaries and
 * corner cases (range 2-5), and then stress the system with larger counts.
 */
#define KCSAN_KUNIT_CASE(test_name)                                            \
	{ .run_case = test_name, .name = #test_name "-02" },                   \
	{ .run_case = test_name, .name = #test_name "-03" },                   \
	{ .run_case = test_name, .name = #test_name "-04" },                   \
	{ .run_case = test_name, .name = #test_name "-05" },                   \
	{ .run_case = test_name, .name = #test_name "-08" },                   \
	{ .run_case = test_name, .name = #test_name "-16" }

static struct kunit_case kcsan_test_cases[] = {
	KCSAN_KUNIT_CASE(test_basic),
	KCSAN_KUNIT_CASE(test_concurrent_races),
	KCSAN_KUNIT_CASE(test_novalue_change),
	KCSAN_KUNIT_CASE(test_novalue_change_exception),
	KCSAN_KUNIT_CASE(test_unknown_origin),
	KCSAN_KUNIT_CASE(test_write_write_assume_atomic),
	KCSAN_KUNIT_CASE(test_write_write_struct),
	KCSAN_KUNIT_CASE(test_write_write_struct_part),
	KCSAN_KUNIT_CASE(test_read_atomic_write_atomic),
	KCSAN_KUNIT_CASE(test_read_plain_atomic_write),
	KCSAN_KUNIT_CASE(test_read_plain_atomic_rmw),
	KCSAN_KUNIT_CASE(test_zero_size_access),
	KCSAN_KUNIT_CASE(test_data_race),
	KCSAN_KUNIT_CASE(test_assert_exclusive_writer),
	KCSAN_KUNIT_CASE(test_assert_exclusive_access),
	KCSAN_KUNIT_CASE(test_assert_exclusive_access_writer),
	KCSAN_KUNIT_CASE(test_assert_exclusive_bits_change),
	KCSAN_KUNIT_CASE(test_assert_exclusive_bits_nochange),
	KCSAN_KUNIT_CASE(test_assert_exclusive_writer_scoped),
	KCSAN_KUNIT_CASE(test_assert_exclusive_access_scoped),
	KCSAN_KUNIT_CASE(test_jiffies_noreport),
	KCSAN_KUNIT_CASE(test_seqlock_noreport),
	KCSAN_KUNIT_CASE(test_atomic_builtins),
	{},
};

/* ===== End test cases ===== */

/* Get number of threads encoded in test name. */
static bool __no_kcsan
get_num_threads(const char *test, int *nthreads)
{
	int len = strlen(test);

	if (WARN_ON(len < 3))
		return false;

	*nthreads = test[len - 1] - '0';
	*nthreads += (test[len - 2] - '0') * 10;

	if (WARN_ON(*nthreads < 0))
		return false;

	return true;
}

/* Concurrent accesses from interrupts. */
__no_kcsan
static void access_thread_timer(struct timer_list *timer)
{
	static atomic_t cnt = ATOMIC_INIT(0);
	unsigned int idx;
	void (*func)(void);

	idx = (unsigned int)atomic_inc_return(&cnt) % ARRAY_SIZE(access_kernels);
	/* Acquire potential initialization. */
	func = smp_load_acquire(&access_kernels[idx]);
	if (func)
		func();
}

/* The main loop for each thread. */
__no_kcsan
static int access_thread(void *arg)
{
	struct timer_list timer;
	unsigned int cnt = 0;
	unsigned int idx;
	void (*func)(void);

	timer_setup_on_stack(&timer, access_thread_timer, 0);
	do {
		might_sleep();

		if (!timer_pending(&timer))
			mod_timer(&timer, jiffies + 1);
		else {
			/* Iterate through all kernels. */
			idx = cnt++ % ARRAY_SIZE(access_kernels);
			/* Acquire potential initialization. */
			func = smp_load_acquire(&access_kernels[idx]);
			if (func)
				func();
		}
	} while (!torture_must_stop());
	del_timer_sync(&timer);
	destroy_timer_on_stack(&timer);

	torture_kthread_stopping("access_thread");
	return 0;
}

__no_kcsan
static int test_init(struct kunit *test)
{
	unsigned long flags;
	int nthreads;
	int i;

	spin_lock_irqsave(&observed.lock, flags);
	for (i = 0; i < ARRAY_SIZE(observed.lines); ++i)
		observed.lines[i][0] = '\0';
	observed.nlines = 0;
	spin_unlock_irqrestore(&observed.lock, flags);

	if (!torture_init_begin((char *)test->name, 1))
		return -EBUSY;

	if (!get_num_threads(test->name, &nthreads))
		goto err;

	if (WARN_ON(threads))
		goto err;

	for (i = 0; i < ARRAY_SIZE(access_kernels); ++i) {
		if (WARN_ON(access_kernels[i]))
			goto err;
	}

	if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
		/*
		 * Without any preemption, keep 2 CPUs free for other tasks, one
		 * of which is the main test case function checking for
		 * completion or failure.
		 */
		const int min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0;
		const int min_required_cpus = 2 + min_unused_cpus;

		if (num_online_cpus() < min_required_cpus) {
			pr_err("%s: too few online CPUs (%u < %d) for test",
			       test->name, num_online_cpus(), min_required_cpus);
			goto err;
		} else if (nthreads > num_online_cpus() - min_unused_cpus) {
			nthreads = num_online_cpus() - min_unused_cpus;
			pr_warn("%s: limiting number of threads to %d\n",
				test->name, nthreads);
		}
	}

	if (nthreads) {
		threads = kcalloc(nthreads + 1, sizeof(struct task_struct *),
				  GFP_KERNEL);
		if (WARN_ON(!threads))
			goto err;

		threads[nthreads] = NULL;
		for (i = 0; i < nthreads; ++i) {
			if (torture_create_kthread(access_thread, NULL,
						   threads[i]))
				goto err;
		}
	}

	torture_init_end();

	return 0;

err:
	kfree(threads);
	threads = NULL;
	torture_init_end();
	return -EINVAL;
}

__no_kcsan
static void test_exit(struct kunit *test)
{
	struct task_struct **stop_thread;
	int i;

	if (torture_cleanup_begin())
		return;

	for (i = 0; i < ARRAY_SIZE(access_kernels); ++i)
		WRITE_ONCE(access_kernels[i], NULL);

	if (threads) {
		for (stop_thread = threads; *stop_thread; stop_thread++)
			torture_stop_kthread(reader_thread, *stop_thread);

		kfree(threads);
		threads = NULL;
	}

	torture_cleanup_end();
}

static struct kunit_suite kcsan_test_suite = {
	.name = "kcsan-test",
	.test_cases = kcsan_test_cases,
	.init = test_init,
	.exit = test_exit,
};
static struct kunit_suite *kcsan_test_suites[] = { &kcsan_test_suite, NULL };

__no_kcsan
static void register_tracepoints(struct tracepoint *tp, void *ignore)
{
	check_trace_callback_type_console(probe_console);
	if (!strcmp(tp->name, "console"))
		WARN_ON(tracepoint_probe_register(tp, probe_console, NULL));
}

__no_kcsan
static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
{
	if (!strcmp(tp->name, "console"))
		tracepoint_probe_unregister(tp, probe_console, NULL);
}

/*
 * We only want to do tracepoints setup and teardown once, therefore we have to
 * customize the init and exit functions and cannot rely on kunit_test_suite().
 */
static int __init kcsan_test_init(void)
{
	/*
	 * Because we want to be able to build the test as a module, we need to
	 * iterate through all known tracepoints, since the static registration
	 * won't work here.
	 */
	for_each_kernel_tracepoint(register_tracepoints, NULL);
	return __kunit_test_suites_init(kcsan_test_suites);
}

static void kcsan_test_exit(void)
{
	__kunit_test_suites_exit(kcsan_test_suites);
	for_each_kernel_tracepoint(unregister_tracepoints, NULL);
	tracepoint_synchronize_unregister();
}

late_initcall(kcsan_test_init);
module_exit(kcsan_test_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Marco Elver <elver@google.com>");