1 // SPDX-License-Identifier: GPL-2.0
3 * KCSAN test with various race scenarious to test runtime behaviour. Since the
4 * interface with which KCSAN's reports are obtained is via the console, this is
5 * the output we should verify. For each test case checks the presence (or
6 * absence) of generated reports. Relies on 'console' tracepoint to capture
7 * reports as they appear in the kernel log.
9 * Makes use of KUnit for test organization, and the Torture framework for test
12 * Copyright (C) 2020, Google LLC.
13 * Author: Marco Elver <elver@google.com>
16 #define pr_fmt(fmt) "kcsan_test: " fmt
18 #include <kunit/test.h>
19 #include <linux/jiffies.h>
20 #include <linux/kcsan-checks.h>
21 #include <linux/kernel.h>
22 #include <linux/sched.h>
23 #include <linux/seqlock.h>
24 #include <linux/spinlock.h>
25 #include <linux/string.h>
26 #include <linux/timer.h>
27 #include <linux/torture.h>
28 #include <linux/tracepoint.h>
29 #include <linux/types.h>
30 #include <trace/events/printk.h>
32 #ifdef CONFIG_CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE
33 #define __KCSAN_ACCESS_RW(alt) (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE)
35 #define __KCSAN_ACCESS_RW(alt) (alt)
38 /* Points to current test-case memory access "kernels". */
39 static void (*access_kernels[2])(void);
41 static struct task_struct **threads; /* Lists of threads. */
42 static unsigned long end_time; /* End time of test. */
44 /* Report as observed from console. */
50 .lock = __SPIN_LOCK_UNLOCKED(observed.lock),
53 /* Setup test checking loop. */
54 static __no_kcsan inline void
55 begin_test_checks(void (*func1)(void), void (*func2)(void))
57 kcsan_disable_current();
60 * Require at least as long as KCSAN_REPORT_ONCE_IN_MS, to ensure at
61 * least one race is reported.
63 end_time = jiffies + msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS + 500);
65 /* Signal start; release potential initialization of shared data. */
66 smp_store_release(&access_kernels[0], func1);
67 smp_store_release(&access_kernels[1], func2);
70 /* End test checking loop. */
71 static __no_kcsan inline bool
72 end_test_checks(bool stop)
74 if (!stop && time_before(jiffies, end_time)) {
75 /* Continue checking */
80 kcsan_enable_current();
85 * Probe for console output: checks if a race was reported, and obtains observed
89 static void probe_console(void *ignore, const char *buf, size_t len)
95 * Note that KCSAN reports under a global lock, so we do not risk the
96 * possibility of having multiple reports interleaved. If that were the
97 * case, we'd expect tests to fail.
100 spin_lock_irqsave(&observed.lock, flags);
101 nlines = observed.nlines;
103 if (strnstr(buf, "BUG: KCSAN: ", len) && strnstr(buf, "test_", len)) {
105 * KCSAN report and related to the test.
107 * The provided @buf is not NUL-terminated; copy no more than
108 * @len bytes and let strscpy() add the missing NUL-terminator.
110 strscpy(observed.lines[0], buf, min(len + 1, sizeof(observed.lines[0])));
112 } else if ((nlines == 1 || nlines == 2) && strnstr(buf, "bytes by", len)) {
113 strscpy(observed.lines[nlines++], buf, min(len + 1, sizeof(observed.lines[0])));
115 if (strnstr(buf, "race at unknown origin", len)) {
116 if (WARN_ON(nlines != 2))
119 /* No second line of interest. */
120 strcpy(observed.lines[nlines++], "<none>");
125 WRITE_ONCE(observed.nlines, nlines); /* Publish new nlines. */
126 spin_unlock_irqrestore(&observed.lock, flags);
129 /* Check if a report related to the test exists. */
131 static bool report_available(void)
133 return READ_ONCE(observed.nlines) == ARRAY_SIZE(observed.lines);
136 /* Report information we expect in a report. */
137 struct expect_report {
138 /* Access information of both accesses. */
140 void *fn; /* Function pointer to expected function of top frame. */
141 void *addr; /* Address of access; unchecked if NULL. */
142 size_t size; /* Size of access; unchecked if @addr is NULL. */
143 int type; /* Access type, see KCSAN_ACCESS definitions. */
147 /* Check observed report matches information in @r. */
149 static bool report_matches(const struct expect_report *r)
151 const bool is_assert = (r->access[0].type | r->access[1].type) & KCSAN_ACCESS_ASSERT;
154 typeof(observed.lines) expect;
159 /* Doubled-checked locking. */
160 if (!report_available())
163 /* Generate expected report contents. */
167 end = &expect[0][sizeof(expect[0]) - 1];
168 cur += scnprintf(cur, end - cur, "BUG: KCSAN: %s in ",
169 is_assert ? "assert: race" : "data-race");
170 if (r->access[1].fn) {
174 /* Expect lexographically sorted function names in title. */
175 scnprintf(tmp[0], sizeof(tmp[0]), "%pS", r->access[0].fn);
176 scnprintf(tmp[1], sizeof(tmp[1]), "%pS", r->access[1].fn);
177 cmp = strcmp(tmp[0], tmp[1]);
178 cur += scnprintf(cur, end - cur, "%ps / %ps",
179 cmp < 0 ? r->access[0].fn : r->access[1].fn,
180 cmp < 0 ? r->access[1].fn : r->access[0].fn);
182 scnprintf(cur, end - cur, "%pS", r->access[0].fn);
183 /* The exact offset won't match, remove it. */
184 cur = strchr(expect[0], '+');
191 end = &expect[1][sizeof(expect[1]) - 1];
192 if (!r->access[1].fn)
193 cur += scnprintf(cur, end - cur, "race at unknown origin, with ");
196 for (i = 0; i < 2; ++i) {
197 const int ty = r->access[i].type;
198 const char *const access_type =
199 (ty & KCSAN_ACCESS_ASSERT) ?
200 ((ty & KCSAN_ACCESS_WRITE) ?
201 "assert no accesses" :
202 "assert no writes") :
203 ((ty & KCSAN_ACCESS_WRITE) ?
204 ((ty & KCSAN_ACCESS_COMPOUND) ?
208 const char *const access_type_aux =
209 (ty & KCSAN_ACCESS_ATOMIC) ?
211 ((ty & KCSAN_ACCESS_SCOPED) ? " (scoped)" : "");
216 end = &expect[2][sizeof(expect[2]) - 1];
218 if (!r->access[1].fn) {
219 /* Dummy string if no second access is available. */
220 strcpy(cur, "<none>");
225 cur += scnprintf(cur, end - cur, "%s%s to ", access_type,
228 if (r->access[i].addr) /* Address is optional. */
229 cur += scnprintf(cur, end - cur, "0x%px of %zu bytes",
230 r->access[i].addr, r->access[i].size);
233 spin_lock_irqsave(&observed.lock, flags);
234 if (!report_available())
235 goto out; /* A new report is being captured. */
237 /* Finally match expected output to what we actually observed. */
238 ret = strstr(observed.lines[0], expect[0]) &&
239 /* Access info may appear in any order. */
240 ((strstr(observed.lines[1], expect[1]) &&
241 strstr(observed.lines[2], expect[2])) ||
242 (strstr(observed.lines[1], expect[2]) &&
243 strstr(observed.lines[2], expect[1])));
245 spin_unlock_irqrestore(&observed.lock, flags);
249 /* ===== Test kernels ===== */
251 static long test_sink;
252 static long test_var;
253 /* @test_array should be large enough to fall into multiple watchpoint slots. */
254 static long test_array[3 * PAGE_SIZE / sizeof(long)];
258 static DEFINE_SEQLOCK(test_seqlock);
261 * Helper to avoid compiler optimizing out reads, and to generate source values
265 static noinline void sink_value(long v) { WRITE_ONCE(test_sink, v); }
267 static noinline void test_kernel_read(void) { sink_value(test_var); }
269 static noinline void test_kernel_write(void)
271 test_var = READ_ONCE_NOCHECK(test_sink) + 1;
274 static noinline void test_kernel_write_nochange(void) { test_var = 42; }
276 /* Suffixed by value-change exception filter. */
277 static noinline void test_kernel_write_nochange_rcu(void) { test_var = 42; }
279 static noinline void test_kernel_read_atomic(void)
281 sink_value(READ_ONCE(test_var));
284 static noinline void test_kernel_write_atomic(void)
286 WRITE_ONCE(test_var, READ_ONCE_NOCHECK(test_sink) + 1);
289 static noinline void test_kernel_atomic_rmw(void)
291 /* Use builtin, so we can set up the "bad" atomic/non-atomic scenario. */
292 __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED);
296 static noinline void test_kernel_write_uninstrumented(void) { test_var++; }
298 static noinline void test_kernel_data_race(void) { data_race(test_var++); }
300 static noinline void test_kernel_assert_writer(void)
302 ASSERT_EXCLUSIVE_WRITER(test_var);
305 static noinline void test_kernel_assert_access(void)
307 ASSERT_EXCLUSIVE_ACCESS(test_var);
310 #define TEST_CHANGE_BITS 0xff00ff00
312 static noinline void test_kernel_change_bits(void)
314 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
316 * Avoid race of unknown origin for this test, just pretend they
319 kcsan_nestable_atomic_begin();
320 test_var ^= TEST_CHANGE_BITS;
321 kcsan_nestable_atomic_end();
323 WRITE_ONCE(test_var, READ_ONCE(test_var) ^ TEST_CHANGE_BITS);
326 static noinline void test_kernel_assert_bits_change(void)
328 ASSERT_EXCLUSIVE_BITS(test_var, TEST_CHANGE_BITS);
331 static noinline void test_kernel_assert_bits_nochange(void)
333 ASSERT_EXCLUSIVE_BITS(test_var, ~TEST_CHANGE_BITS);
336 /* To check that scoped assertions do trigger anywhere in scope. */
337 static noinline void test_enter_scope(void)
341 /* Unrelated accesses to scoped assert. */
342 READ_ONCE(test_sink);
343 kcsan_check_read(&x, sizeof(x));
346 static noinline void test_kernel_assert_writer_scoped(void)
348 ASSERT_EXCLUSIVE_WRITER_SCOPED(test_var);
352 static noinline void test_kernel_assert_access_scoped(void)
354 ASSERT_EXCLUSIVE_ACCESS_SCOPED(test_var);
358 static noinline void test_kernel_rmw_array(void)
362 for (i = 0; i < ARRAY_SIZE(test_array); ++i)
366 static noinline void test_kernel_write_struct(void)
368 kcsan_check_write(&test_struct, sizeof(test_struct));
369 kcsan_disable_current();
370 test_struct.val[3]++; /* induce value change */
371 kcsan_enable_current();
374 static noinline void test_kernel_write_struct_part(void)
376 test_struct.val[3] = 42;
379 static noinline void test_kernel_read_struct_zero_size(void)
381 kcsan_check_read(&test_struct.val[3], 0);
384 static noinline void test_kernel_jiffies_reader(void)
386 sink_value((long)jiffies);
389 static noinline void test_kernel_seqlock_reader(void)
394 seq = read_seqbegin(&test_seqlock);
395 sink_value(test_var);
396 } while (read_seqretry(&test_seqlock, seq));
399 static noinline void test_kernel_seqlock_writer(void)
403 write_seqlock_irqsave(&test_seqlock, flags);
405 write_sequnlock_irqrestore(&test_seqlock, flags);
408 static noinline void test_kernel_atomic_builtins(void)
411 * Generate concurrent accesses, expecting no reports, ensuring KCSAN
412 * treats builtin atomics as actually atomic.
414 __atomic_load_n(&test_var, __ATOMIC_RELAXED);
417 static noinline void test_kernel_xor_1bit(void)
419 /* Do not report data races between the read-writes. */
420 kcsan_nestable_atomic_begin();
422 kcsan_nestable_atomic_end();
425 /* ===== Test cases ===== */
427 /* Simple test with normal data race. */
429 static void test_basic(struct kunit *test)
431 const struct expect_report expect = {
433 { test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
434 { test_kernel_read, &test_var, sizeof(test_var), 0 },
437 static const struct expect_report never = {
439 { test_kernel_read, &test_var, sizeof(test_var), 0 },
440 { test_kernel_read, &test_var, sizeof(test_var), 0 },
443 bool match_expect = false;
444 bool match_never = false;
446 begin_test_checks(test_kernel_write, test_kernel_read);
448 match_expect |= report_matches(&expect);
449 match_never = report_matches(&never);
450 } while (!end_test_checks(match_never));
451 KUNIT_EXPECT_TRUE(test, match_expect);
452 KUNIT_EXPECT_FALSE(test, match_never);
456 * Stress KCSAN with lots of concurrent races on different addresses until
460 static void test_concurrent_races(struct kunit *test)
462 const struct expect_report expect = {
464 /* NULL will match any address. */
465 { test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
466 { test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(0) },
469 static const struct expect_report never = {
471 { test_kernel_rmw_array, NULL, 0, 0 },
472 { test_kernel_rmw_array, NULL, 0, 0 },
475 bool match_expect = false;
476 bool match_never = false;
478 begin_test_checks(test_kernel_rmw_array, test_kernel_rmw_array);
480 match_expect |= report_matches(&expect);
481 match_never |= report_matches(&never);
482 } while (!end_test_checks(false));
483 KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check matches exist. */
484 KUNIT_EXPECT_FALSE(test, match_never);
487 /* Test the KCSAN_REPORT_VALUE_CHANGE_ONLY option. */
489 static void test_novalue_change(struct kunit *test)
491 const struct expect_report expect = {
493 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
494 { test_kernel_read, &test_var, sizeof(test_var), 0 },
497 bool match_expect = false;
499 begin_test_checks(test_kernel_write_nochange, test_kernel_read);
501 match_expect = report_matches(&expect);
502 } while (!end_test_checks(match_expect));
503 if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY))
504 KUNIT_EXPECT_FALSE(test, match_expect);
506 KUNIT_EXPECT_TRUE(test, match_expect);
510 * Test that the rules where the KCSAN_REPORT_VALUE_CHANGE_ONLY option should
514 static void test_novalue_change_exception(struct kunit *test)
516 const struct expect_report expect = {
518 { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
519 { test_kernel_read, &test_var, sizeof(test_var), 0 },
522 bool match_expect = false;
524 begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read);
526 match_expect = report_matches(&expect);
527 } while (!end_test_checks(match_expect));
528 KUNIT_EXPECT_TRUE(test, match_expect);
531 /* Test that data races of unknown origin are reported. */
533 static void test_unknown_origin(struct kunit *test)
535 const struct expect_report expect = {
537 { test_kernel_read, &test_var, sizeof(test_var), 0 },
541 bool match_expect = false;
543 begin_test_checks(test_kernel_write_uninstrumented, test_kernel_read);
545 match_expect = report_matches(&expect);
546 } while (!end_test_checks(match_expect));
547 if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
548 KUNIT_EXPECT_TRUE(test, match_expect);
550 KUNIT_EXPECT_FALSE(test, match_expect);
553 /* Test KCSAN_ASSUME_PLAIN_WRITES_ATOMIC if it is selected. */
555 static void test_write_write_assume_atomic(struct kunit *test)
557 const struct expect_report expect = {
559 { test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
560 { test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
563 bool match_expect = false;
565 begin_test_checks(test_kernel_write, test_kernel_write);
567 sink_value(READ_ONCE(test_var)); /* induce value-change */
568 match_expect = report_matches(&expect);
569 } while (!end_test_checks(match_expect));
570 if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC))
571 KUNIT_EXPECT_FALSE(test, match_expect);
573 KUNIT_EXPECT_TRUE(test, match_expect);
577 * Test that data races with writes larger than word-size are always reported,
578 * even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
581 static void test_write_write_struct(struct kunit *test)
583 const struct expect_report expect = {
585 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
586 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
589 bool match_expect = false;
591 begin_test_checks(test_kernel_write_struct, test_kernel_write_struct);
593 match_expect = report_matches(&expect);
594 } while (!end_test_checks(match_expect));
595 KUNIT_EXPECT_TRUE(test, match_expect);
599 * Test that data races where only one write is larger than word-size are always
600 * reported, even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
603 static void test_write_write_struct_part(struct kunit *test)
605 const struct expect_report expect = {
607 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
608 { test_kernel_write_struct_part, &test_struct.val[3], sizeof(test_struct.val[3]), KCSAN_ACCESS_WRITE },
611 bool match_expect = false;
613 begin_test_checks(test_kernel_write_struct, test_kernel_write_struct_part);
615 match_expect = report_matches(&expect);
616 } while (!end_test_checks(match_expect));
617 KUNIT_EXPECT_TRUE(test, match_expect);
620 /* Test that races with atomic accesses never result in reports. */
622 static void test_read_atomic_write_atomic(struct kunit *test)
624 bool match_never = false;
626 begin_test_checks(test_kernel_read_atomic, test_kernel_write_atomic);
628 match_never = report_available();
629 } while (!end_test_checks(match_never));
630 KUNIT_EXPECT_FALSE(test, match_never);
633 /* Test that a race with an atomic and plain access result in reports. */
635 static void test_read_plain_atomic_write(struct kunit *test)
637 const struct expect_report expect = {
639 { test_kernel_read, &test_var, sizeof(test_var), 0 },
640 { test_kernel_write_atomic, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
643 bool match_expect = false;
645 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
648 begin_test_checks(test_kernel_read, test_kernel_write_atomic);
650 match_expect = report_matches(&expect);
651 } while (!end_test_checks(match_expect));
652 KUNIT_EXPECT_TRUE(test, match_expect);
655 /* Test that atomic RMWs generate correct report. */
657 static void test_read_plain_atomic_rmw(struct kunit *test)
659 const struct expect_report expect = {
661 { test_kernel_read, &test_var, sizeof(test_var), 0 },
662 { test_kernel_atomic_rmw, &test_var, sizeof(test_var),
663 KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
666 bool match_expect = false;
668 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
671 begin_test_checks(test_kernel_read, test_kernel_atomic_rmw);
673 match_expect = report_matches(&expect);
674 } while (!end_test_checks(match_expect));
675 KUNIT_EXPECT_TRUE(test, match_expect);
678 /* Zero-sized accesses should never cause data race reports. */
680 static void test_zero_size_access(struct kunit *test)
682 const struct expect_report expect = {
684 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
685 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
688 const struct expect_report never = {
690 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
691 { test_kernel_read_struct_zero_size, &test_struct.val[3], 0, 0 },
694 bool match_expect = false;
695 bool match_never = false;
697 begin_test_checks(test_kernel_write_struct, test_kernel_read_struct_zero_size);
699 match_expect |= report_matches(&expect);
700 match_never = report_matches(&never);
701 } while (!end_test_checks(match_never));
702 KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check. */
703 KUNIT_EXPECT_FALSE(test, match_never);
706 /* Test the data_race() macro. */
708 static void test_data_race(struct kunit *test)
710 bool match_never = false;
712 begin_test_checks(test_kernel_data_race, test_kernel_data_race);
714 match_never = report_available();
715 } while (!end_test_checks(match_never));
716 KUNIT_EXPECT_FALSE(test, match_never);
720 static void test_assert_exclusive_writer(struct kunit *test)
722 const struct expect_report expect = {
724 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
725 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
728 bool match_expect = false;
730 begin_test_checks(test_kernel_assert_writer, test_kernel_write_nochange);
732 match_expect = report_matches(&expect);
733 } while (!end_test_checks(match_expect));
734 KUNIT_EXPECT_TRUE(test, match_expect);
738 static void test_assert_exclusive_access(struct kunit *test)
740 const struct expect_report expect = {
742 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
743 { test_kernel_read, &test_var, sizeof(test_var), 0 },
746 bool match_expect = false;
748 begin_test_checks(test_kernel_assert_access, test_kernel_read);
750 match_expect = report_matches(&expect);
751 } while (!end_test_checks(match_expect));
752 KUNIT_EXPECT_TRUE(test, match_expect);
756 static void test_assert_exclusive_access_writer(struct kunit *test)
758 const struct expect_report expect_access_writer = {
760 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
761 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
764 const struct expect_report expect_access_access = {
766 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
767 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
770 const struct expect_report never = {
772 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
773 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
776 bool match_expect_access_writer = false;
777 bool match_expect_access_access = false;
778 bool match_never = false;
780 begin_test_checks(test_kernel_assert_access, test_kernel_assert_writer);
782 match_expect_access_writer |= report_matches(&expect_access_writer);
783 match_expect_access_access |= report_matches(&expect_access_access);
784 match_never |= report_matches(&never);
785 } while (!end_test_checks(match_never));
786 KUNIT_EXPECT_TRUE(test, match_expect_access_writer);
787 KUNIT_EXPECT_TRUE(test, match_expect_access_access);
788 KUNIT_EXPECT_FALSE(test, match_never);
792 static void test_assert_exclusive_bits_change(struct kunit *test)
794 const struct expect_report expect = {
796 { test_kernel_assert_bits_change, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
797 { test_kernel_change_bits, &test_var, sizeof(test_var),
798 KCSAN_ACCESS_WRITE | (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) ? 0 : KCSAN_ACCESS_ATOMIC) },
801 bool match_expect = false;
803 begin_test_checks(test_kernel_assert_bits_change, test_kernel_change_bits);
805 match_expect = report_matches(&expect);
806 } while (!end_test_checks(match_expect));
807 KUNIT_EXPECT_TRUE(test, match_expect);
811 static void test_assert_exclusive_bits_nochange(struct kunit *test)
813 bool match_never = false;
815 begin_test_checks(test_kernel_assert_bits_nochange, test_kernel_change_bits);
817 match_never = report_available();
818 } while (!end_test_checks(match_never));
819 KUNIT_EXPECT_FALSE(test, match_never);
823 static void test_assert_exclusive_writer_scoped(struct kunit *test)
825 const struct expect_report expect_start = {
827 { test_kernel_assert_writer_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
828 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
831 const struct expect_report expect_anywhere = {
833 { test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
834 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
837 bool match_expect_start = false;
838 bool match_expect_anywhere = false;
840 begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange);
842 match_expect_start |= report_matches(&expect_start);
843 match_expect_anywhere |= report_matches(&expect_anywhere);
844 } while (!end_test_checks(match_expect_start && match_expect_anywhere));
845 KUNIT_EXPECT_TRUE(test, match_expect_start);
846 KUNIT_EXPECT_TRUE(test, match_expect_anywhere);
850 static void test_assert_exclusive_access_scoped(struct kunit *test)
852 const struct expect_report expect_start1 = {
854 { test_kernel_assert_access_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
855 { test_kernel_read, &test_var, sizeof(test_var), 0 },
858 const struct expect_report expect_start2 = {
859 .access = { expect_start1.access[0], expect_start1.access[0] },
861 const struct expect_report expect_inscope = {
863 { test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
864 { test_kernel_read, &test_var, sizeof(test_var), 0 },
867 bool match_expect_start = false;
868 bool match_expect_inscope = false;
870 begin_test_checks(test_kernel_assert_access_scoped, test_kernel_read);
871 end_time += msecs_to_jiffies(1000); /* This test requires a bit more time. */
873 match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2);
874 match_expect_inscope |= report_matches(&expect_inscope);
875 } while (!end_test_checks(match_expect_start && match_expect_inscope));
876 KUNIT_EXPECT_TRUE(test, match_expect_start);
877 KUNIT_EXPECT_TRUE(test, match_expect_inscope);
881 * jiffies is special (declared to be volatile) and its accesses are typically
882 * not marked; this test ensures that the compiler nor KCSAN gets confused about
883 * jiffies's declaration on different architectures.
886 static void test_jiffies_noreport(struct kunit *test)
888 bool match_never = false;
890 begin_test_checks(test_kernel_jiffies_reader, test_kernel_jiffies_reader);
892 match_never = report_available();
893 } while (!end_test_checks(match_never));
894 KUNIT_EXPECT_FALSE(test, match_never);
897 /* Test that racing accesses in seqlock critical sections are not reported. */
899 static void test_seqlock_noreport(struct kunit *test)
901 bool match_never = false;
903 begin_test_checks(test_kernel_seqlock_reader, test_kernel_seqlock_writer);
905 match_never = report_available();
906 } while (!end_test_checks(match_never));
907 KUNIT_EXPECT_FALSE(test, match_never);
911 * Test atomic builtins work and required instrumentation functions exist. We
912 * also test that KCSAN understands they're atomic by racing with them via
913 * test_kernel_atomic_builtins(), and expect no reports.
915 * The atomic builtins _SHOULD NOT_ be used in normal kernel code!
917 static void test_atomic_builtins(struct kunit *test)
919 bool match_never = false;
921 begin_test_checks(test_kernel_atomic_builtins, test_kernel_atomic_builtins);
925 kcsan_enable_current();
927 __atomic_store_n(&test_var, 42L, __ATOMIC_RELAXED);
928 KUNIT_EXPECT_EQ(test, 42L, __atomic_load_n(&test_var, __ATOMIC_RELAXED));
930 KUNIT_EXPECT_EQ(test, 42L, __atomic_exchange_n(&test_var, 20, __ATOMIC_RELAXED));
931 KUNIT_EXPECT_EQ(test, 20L, test_var);
934 KUNIT_EXPECT_TRUE(test, __atomic_compare_exchange_n(&test_var, &tmp, 30L,
937 KUNIT_EXPECT_EQ(test, tmp, 20L);
938 KUNIT_EXPECT_EQ(test, test_var, 30L);
939 KUNIT_EXPECT_FALSE(test, __atomic_compare_exchange_n(&test_var, &tmp, 40L,
942 KUNIT_EXPECT_EQ(test, tmp, 30L);
943 KUNIT_EXPECT_EQ(test, test_var, 30L);
945 KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED));
946 KUNIT_EXPECT_EQ(test, 31L, __atomic_fetch_sub(&test_var, 1, __ATOMIC_RELAXED));
947 KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_and(&test_var, 0xf, __ATOMIC_RELAXED));
948 KUNIT_EXPECT_EQ(test, 14L, __atomic_fetch_xor(&test_var, 0xf, __ATOMIC_RELAXED));
949 KUNIT_EXPECT_EQ(test, 1L, __atomic_fetch_or(&test_var, 0xf0, __ATOMIC_RELAXED));
950 KUNIT_EXPECT_EQ(test, 241L, __atomic_fetch_nand(&test_var, 0xf, __ATOMIC_RELAXED));
951 KUNIT_EXPECT_EQ(test, -2L, test_var);
953 __atomic_thread_fence(__ATOMIC_SEQ_CST);
954 __atomic_signal_fence(__ATOMIC_SEQ_CST);
956 kcsan_disable_current();
958 match_never = report_available();
959 } while (!end_test_checks(match_never));
960 KUNIT_EXPECT_FALSE(test, match_never);
964 static void test_1bit_value_change(struct kunit *test)
966 const struct expect_report expect = {
968 { test_kernel_read, &test_var, sizeof(test_var), 0 },
969 { test_kernel_xor_1bit, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
974 begin_test_checks(test_kernel_read, test_kernel_xor_1bit);
976 match = IS_ENABLED(CONFIG_KCSAN_PERMISSIVE)
978 : report_matches(&expect);
979 } while (!end_test_checks(match));
980 if (IS_ENABLED(CONFIG_KCSAN_PERMISSIVE))
981 KUNIT_EXPECT_FALSE(test, match);
983 KUNIT_EXPECT_TRUE(test, match);
987 * Generate thread counts for all test cases. Values generated are in interval
988 * [2, 5] followed by exponentially increasing thread counts from 8 to 32.
990 * The thread counts are chosen to cover potentially interesting boundaries and
991 * corner cases (2 to 5), and then stress the system with larger counts.
993 static const void *nthreads_gen_params(const void *prev, char *desc)
995 long nthreads = (long)prev;
997 if (nthreads < 0 || nthreads >= 32)
998 nthreads = 0; /* stop */
1000 nthreads = 2; /* initial value */
1001 else if (nthreads < 5)
1003 else if (nthreads == 5)
1008 if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
1010 * Without any preemption, keep 2 CPUs free for other tasks, one
1011 * of which is the main test case function checking for
1012 * completion or failure.
1014 const long min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0;
1015 const long min_required_cpus = 2 + min_unused_cpus;
1017 if (num_online_cpus() < min_required_cpus) {
1018 pr_err_once("Too few online CPUs (%u < %ld) for test\n",
1019 num_online_cpus(), min_required_cpus);
1021 } else if (nthreads >= num_online_cpus() - min_unused_cpus) {
1022 /* Use negative value to indicate last param. */
1023 nthreads = -(num_online_cpus() - min_unused_cpus);
1024 pr_warn_once("Limiting number of threads to %ld (only %d online CPUs)\n",
1025 -nthreads, num_online_cpus());
1029 snprintf(desc, KUNIT_PARAM_DESC_SIZE, "threads=%ld", abs(nthreads));
1030 return (void *)nthreads;
1033 #define KCSAN_KUNIT_CASE(test_name) KUNIT_CASE_PARAM(test_name, nthreads_gen_params)
1034 static struct kunit_case kcsan_test_cases[] = {
1035 KCSAN_KUNIT_CASE(test_basic),
1036 KCSAN_KUNIT_CASE(test_concurrent_races),
1037 KCSAN_KUNIT_CASE(test_novalue_change),
1038 KCSAN_KUNIT_CASE(test_novalue_change_exception),
1039 KCSAN_KUNIT_CASE(test_unknown_origin),
1040 KCSAN_KUNIT_CASE(test_write_write_assume_atomic),
1041 KCSAN_KUNIT_CASE(test_write_write_struct),
1042 KCSAN_KUNIT_CASE(test_write_write_struct_part),
1043 KCSAN_KUNIT_CASE(test_read_atomic_write_atomic),
1044 KCSAN_KUNIT_CASE(test_read_plain_atomic_write),
1045 KCSAN_KUNIT_CASE(test_read_plain_atomic_rmw),
1046 KCSAN_KUNIT_CASE(test_zero_size_access),
1047 KCSAN_KUNIT_CASE(test_data_race),
1048 KCSAN_KUNIT_CASE(test_assert_exclusive_writer),
1049 KCSAN_KUNIT_CASE(test_assert_exclusive_access),
1050 KCSAN_KUNIT_CASE(test_assert_exclusive_access_writer),
1051 KCSAN_KUNIT_CASE(test_assert_exclusive_bits_change),
1052 KCSAN_KUNIT_CASE(test_assert_exclusive_bits_nochange),
1053 KCSAN_KUNIT_CASE(test_assert_exclusive_writer_scoped),
1054 KCSAN_KUNIT_CASE(test_assert_exclusive_access_scoped),
1055 KCSAN_KUNIT_CASE(test_jiffies_noreport),
1056 KCSAN_KUNIT_CASE(test_seqlock_noreport),
1057 KCSAN_KUNIT_CASE(test_atomic_builtins),
1058 KCSAN_KUNIT_CASE(test_1bit_value_change),
1062 /* ===== End test cases ===== */
1064 /* Concurrent accesses from interrupts. */
1066 static void access_thread_timer(struct timer_list *timer)
1068 static atomic_t cnt = ATOMIC_INIT(0);
1072 idx = (unsigned int)atomic_inc_return(&cnt) % ARRAY_SIZE(access_kernels);
1073 /* Acquire potential initialization. */
1074 func = smp_load_acquire(&access_kernels[idx]);
1079 /* The main loop for each thread. */
1081 static int access_thread(void *arg)
1083 struct timer_list timer;
1084 unsigned int cnt = 0;
1088 timer_setup_on_stack(&timer, access_thread_timer, 0);
1092 if (!timer_pending(&timer))
1093 mod_timer(&timer, jiffies + 1);
1095 /* Iterate through all kernels. */
1096 idx = cnt++ % ARRAY_SIZE(access_kernels);
1097 /* Acquire potential initialization. */
1098 func = smp_load_acquire(&access_kernels[idx]);
1102 } while (!torture_must_stop());
1103 del_timer_sync(&timer);
1104 destroy_timer_on_stack(&timer);
1106 torture_kthread_stopping("access_thread");
1111 static int test_init(struct kunit *test)
1113 unsigned long flags;
1117 spin_lock_irqsave(&observed.lock, flags);
1118 for (i = 0; i < ARRAY_SIZE(observed.lines); ++i)
1119 observed.lines[i][0] = '\0';
1120 observed.nlines = 0;
1121 spin_unlock_irqrestore(&observed.lock, flags);
1123 if (!torture_init_begin((char *)test->name, 1))
1126 if (WARN_ON(threads))
1129 for (i = 0; i < ARRAY_SIZE(access_kernels); ++i) {
1130 if (WARN_ON(access_kernels[i]))
1134 nthreads = abs((long)test->param_value);
1135 if (WARN_ON(!nthreads))
1138 threads = kcalloc(nthreads + 1, sizeof(struct task_struct *), GFP_KERNEL);
1139 if (WARN_ON(!threads))
1142 threads[nthreads] = NULL;
1143 for (i = 0; i < nthreads; ++i) {
1144 if (torture_create_kthread(access_thread, NULL, threads[i]))
1160 static void test_exit(struct kunit *test)
1162 struct task_struct **stop_thread;
1165 if (torture_cleanup_begin())
1168 for (i = 0; i < ARRAY_SIZE(access_kernels); ++i)
1169 WRITE_ONCE(access_kernels[i], NULL);
1172 for (stop_thread = threads; *stop_thread; stop_thread++)
1173 torture_stop_kthread(reader_thread, *stop_thread);
1179 torture_cleanup_end();
1182 static struct kunit_suite kcsan_test_suite = {
1184 .test_cases = kcsan_test_cases,
1188 static struct kunit_suite *kcsan_test_suites[] = { &kcsan_test_suite, NULL };
1191 static void register_tracepoints(struct tracepoint *tp, void *ignore)
1193 check_trace_callback_type_console(probe_console);
1194 if (!strcmp(tp->name, "console"))
1195 WARN_ON(tracepoint_probe_register(tp, probe_console, NULL));
1199 static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
1201 if (!strcmp(tp->name, "console"))
1202 tracepoint_probe_unregister(tp, probe_console, NULL);
1206 * We only want to do tracepoints setup and teardown once, therefore we have to
1207 * customize the init and exit functions and cannot rely on kunit_test_suite().
1209 static int __init kcsan_test_init(void)
1212 * Because we want to be able to build the test as a module, we need to
1213 * iterate through all known tracepoints, since the static registration
1216 for_each_kernel_tracepoint(register_tracepoints, NULL);
1217 return __kunit_test_suites_init(kcsan_test_suites);
1220 static void kcsan_test_exit(void)
1222 __kunit_test_suites_exit(kcsan_test_suites);
1223 for_each_kernel_tracepoint(unregister_tracepoints, NULL);
1224 tracepoint_synchronize_unregister();
1227 late_initcall(kcsan_test_init);
1228 module_exit(kcsan_test_exit);
1230 MODULE_LICENSE("GPL v2");
1231 MODULE_AUTHOR("Marco Elver <elver@google.com>");