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 /* ===== Test cases ===== */
419 /* Simple test with normal data race. */
421 static void test_basic(struct kunit *test)
423 const struct expect_report expect = {
425 { test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
426 { test_kernel_read, &test_var, sizeof(test_var), 0 },
429 static const struct expect_report never = {
431 { test_kernel_read, &test_var, sizeof(test_var), 0 },
432 { test_kernel_read, &test_var, sizeof(test_var), 0 },
435 bool match_expect = false;
436 bool match_never = false;
438 begin_test_checks(test_kernel_write, test_kernel_read);
440 match_expect |= report_matches(&expect);
441 match_never = report_matches(&never);
442 } while (!end_test_checks(match_never));
443 KUNIT_EXPECT_TRUE(test, match_expect);
444 KUNIT_EXPECT_FALSE(test, match_never);
448 * Stress KCSAN with lots of concurrent races on different addresses until
452 static void test_concurrent_races(struct kunit *test)
454 const struct expect_report expect = {
456 /* NULL will match any address. */
457 { test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
458 { test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(0) },
461 static const struct expect_report never = {
463 { test_kernel_rmw_array, NULL, 0, 0 },
464 { test_kernel_rmw_array, NULL, 0, 0 },
467 bool match_expect = false;
468 bool match_never = false;
470 begin_test_checks(test_kernel_rmw_array, test_kernel_rmw_array);
472 match_expect |= report_matches(&expect);
473 match_never |= report_matches(&never);
474 } while (!end_test_checks(false));
475 KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check matches exist. */
476 KUNIT_EXPECT_FALSE(test, match_never);
479 /* Test the KCSAN_REPORT_VALUE_CHANGE_ONLY option. */
481 static void test_novalue_change(struct kunit *test)
483 const struct expect_report expect = {
485 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
486 { test_kernel_read, &test_var, sizeof(test_var), 0 },
489 bool match_expect = false;
491 begin_test_checks(test_kernel_write_nochange, test_kernel_read);
493 match_expect = report_matches(&expect);
494 } while (!end_test_checks(match_expect));
495 if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY))
496 KUNIT_EXPECT_FALSE(test, match_expect);
498 KUNIT_EXPECT_TRUE(test, match_expect);
502 * Test that the rules where the KCSAN_REPORT_VALUE_CHANGE_ONLY option should
506 static void test_novalue_change_exception(struct kunit *test)
508 const struct expect_report expect = {
510 { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
511 { test_kernel_read, &test_var, sizeof(test_var), 0 },
514 bool match_expect = false;
516 begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read);
518 match_expect = report_matches(&expect);
519 } while (!end_test_checks(match_expect));
520 KUNIT_EXPECT_TRUE(test, match_expect);
523 /* Test that data races of unknown origin are reported. */
525 static void test_unknown_origin(struct kunit *test)
527 const struct expect_report expect = {
529 { test_kernel_read, &test_var, sizeof(test_var), 0 },
533 bool match_expect = false;
535 begin_test_checks(test_kernel_write_uninstrumented, test_kernel_read);
537 match_expect = report_matches(&expect);
538 } while (!end_test_checks(match_expect));
539 if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
540 KUNIT_EXPECT_TRUE(test, match_expect);
542 KUNIT_EXPECT_FALSE(test, match_expect);
545 /* Test KCSAN_ASSUME_PLAIN_WRITES_ATOMIC if it is selected. */
547 static void test_write_write_assume_atomic(struct kunit *test)
549 const struct expect_report expect = {
551 { test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
552 { test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
555 bool match_expect = false;
557 begin_test_checks(test_kernel_write, test_kernel_write);
559 sink_value(READ_ONCE(test_var)); /* induce value-change */
560 match_expect = report_matches(&expect);
561 } while (!end_test_checks(match_expect));
562 if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC))
563 KUNIT_EXPECT_FALSE(test, match_expect);
565 KUNIT_EXPECT_TRUE(test, match_expect);
569 * Test that data races with writes larger than word-size are always reported,
570 * even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
573 static void test_write_write_struct(struct kunit *test)
575 const struct expect_report expect = {
577 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
578 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
581 bool match_expect = false;
583 begin_test_checks(test_kernel_write_struct, test_kernel_write_struct);
585 match_expect = report_matches(&expect);
586 } while (!end_test_checks(match_expect));
587 KUNIT_EXPECT_TRUE(test, match_expect);
591 * Test that data races where only one write is larger than word-size are always
592 * reported, even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
595 static void test_write_write_struct_part(struct kunit *test)
597 const struct expect_report expect = {
599 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
600 { test_kernel_write_struct_part, &test_struct.val[3], sizeof(test_struct.val[3]), KCSAN_ACCESS_WRITE },
603 bool match_expect = false;
605 begin_test_checks(test_kernel_write_struct, test_kernel_write_struct_part);
607 match_expect = report_matches(&expect);
608 } while (!end_test_checks(match_expect));
609 KUNIT_EXPECT_TRUE(test, match_expect);
612 /* Test that races with atomic accesses never result in reports. */
614 static void test_read_atomic_write_atomic(struct kunit *test)
616 bool match_never = false;
618 begin_test_checks(test_kernel_read_atomic, test_kernel_write_atomic);
620 match_never = report_available();
621 } while (!end_test_checks(match_never));
622 KUNIT_EXPECT_FALSE(test, match_never);
625 /* Test that a race with an atomic and plain access result in reports. */
627 static void test_read_plain_atomic_write(struct kunit *test)
629 const struct expect_report expect = {
631 { test_kernel_read, &test_var, sizeof(test_var), 0 },
632 { test_kernel_write_atomic, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
635 bool match_expect = false;
637 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
640 begin_test_checks(test_kernel_read, test_kernel_write_atomic);
642 match_expect = report_matches(&expect);
643 } while (!end_test_checks(match_expect));
644 KUNIT_EXPECT_TRUE(test, match_expect);
647 /* Test that atomic RMWs generate correct report. */
649 static void test_read_plain_atomic_rmw(struct kunit *test)
651 const struct expect_report expect = {
653 { test_kernel_read, &test_var, sizeof(test_var), 0 },
654 { test_kernel_atomic_rmw, &test_var, sizeof(test_var),
655 KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
658 bool match_expect = false;
660 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
663 begin_test_checks(test_kernel_read, test_kernel_atomic_rmw);
665 match_expect = report_matches(&expect);
666 } while (!end_test_checks(match_expect));
667 KUNIT_EXPECT_TRUE(test, match_expect);
670 /* Zero-sized accesses should never cause data race reports. */
672 static void test_zero_size_access(struct kunit *test)
674 const struct expect_report expect = {
676 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
677 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
680 const struct expect_report never = {
682 { test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
683 { test_kernel_read_struct_zero_size, &test_struct.val[3], 0, 0 },
686 bool match_expect = false;
687 bool match_never = false;
689 begin_test_checks(test_kernel_write_struct, test_kernel_read_struct_zero_size);
691 match_expect |= report_matches(&expect);
692 match_never = report_matches(&never);
693 } while (!end_test_checks(match_never));
694 KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check. */
695 KUNIT_EXPECT_FALSE(test, match_never);
698 /* Test the data_race() macro. */
700 static void test_data_race(struct kunit *test)
702 bool match_never = false;
704 begin_test_checks(test_kernel_data_race, test_kernel_data_race);
706 match_never = report_available();
707 } while (!end_test_checks(match_never));
708 KUNIT_EXPECT_FALSE(test, match_never);
712 static void test_assert_exclusive_writer(struct kunit *test)
714 const struct expect_report expect = {
716 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
717 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
720 bool match_expect = false;
722 begin_test_checks(test_kernel_assert_writer, test_kernel_write_nochange);
724 match_expect = report_matches(&expect);
725 } while (!end_test_checks(match_expect));
726 KUNIT_EXPECT_TRUE(test, match_expect);
730 static void test_assert_exclusive_access(struct kunit *test)
732 const struct expect_report expect = {
734 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
735 { test_kernel_read, &test_var, sizeof(test_var), 0 },
738 bool match_expect = false;
740 begin_test_checks(test_kernel_assert_access, test_kernel_read);
742 match_expect = report_matches(&expect);
743 } while (!end_test_checks(match_expect));
744 KUNIT_EXPECT_TRUE(test, match_expect);
748 static void test_assert_exclusive_access_writer(struct kunit *test)
750 const struct expect_report expect_access_writer = {
752 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
753 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
756 const struct expect_report expect_access_access = {
758 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
759 { test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
762 const struct expect_report never = {
764 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
765 { test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
768 bool match_expect_access_writer = false;
769 bool match_expect_access_access = false;
770 bool match_never = false;
772 begin_test_checks(test_kernel_assert_access, test_kernel_assert_writer);
774 match_expect_access_writer |= report_matches(&expect_access_writer);
775 match_expect_access_access |= report_matches(&expect_access_access);
776 match_never |= report_matches(&never);
777 } while (!end_test_checks(match_never));
778 KUNIT_EXPECT_TRUE(test, match_expect_access_writer);
779 KUNIT_EXPECT_TRUE(test, match_expect_access_access);
780 KUNIT_EXPECT_FALSE(test, match_never);
784 static void test_assert_exclusive_bits_change(struct kunit *test)
786 const struct expect_report expect = {
788 { test_kernel_assert_bits_change, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
789 { test_kernel_change_bits, &test_var, sizeof(test_var),
790 KCSAN_ACCESS_WRITE | (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) ? 0 : KCSAN_ACCESS_ATOMIC) },
793 bool match_expect = false;
795 begin_test_checks(test_kernel_assert_bits_change, test_kernel_change_bits);
797 match_expect = report_matches(&expect);
798 } while (!end_test_checks(match_expect));
799 KUNIT_EXPECT_TRUE(test, match_expect);
803 static void test_assert_exclusive_bits_nochange(struct kunit *test)
805 bool match_never = false;
807 begin_test_checks(test_kernel_assert_bits_nochange, test_kernel_change_bits);
809 match_never = report_available();
810 } while (!end_test_checks(match_never));
811 KUNIT_EXPECT_FALSE(test, match_never);
815 static void test_assert_exclusive_writer_scoped(struct kunit *test)
817 const struct expect_report expect_start = {
819 { test_kernel_assert_writer_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
820 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
823 const struct expect_report expect_anywhere = {
825 { test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
826 { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
829 bool match_expect_start = false;
830 bool match_expect_anywhere = false;
832 begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange);
834 match_expect_start |= report_matches(&expect_start);
835 match_expect_anywhere |= report_matches(&expect_anywhere);
836 } while (!end_test_checks(match_expect_start && match_expect_anywhere));
837 KUNIT_EXPECT_TRUE(test, match_expect_start);
838 KUNIT_EXPECT_TRUE(test, match_expect_anywhere);
842 static void test_assert_exclusive_access_scoped(struct kunit *test)
844 const struct expect_report expect_start1 = {
846 { test_kernel_assert_access_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
847 { test_kernel_read, &test_var, sizeof(test_var), 0 },
850 const struct expect_report expect_start2 = {
851 .access = { expect_start1.access[0], expect_start1.access[0] },
853 const struct expect_report expect_inscope = {
855 { test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
856 { test_kernel_read, &test_var, sizeof(test_var), 0 },
859 bool match_expect_start = false;
860 bool match_expect_inscope = false;
862 begin_test_checks(test_kernel_assert_access_scoped, test_kernel_read);
863 end_time += msecs_to_jiffies(1000); /* This test requires a bit more time. */
865 match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2);
866 match_expect_inscope |= report_matches(&expect_inscope);
867 } while (!end_test_checks(match_expect_start && match_expect_inscope));
868 KUNIT_EXPECT_TRUE(test, match_expect_start);
869 KUNIT_EXPECT_TRUE(test, match_expect_inscope);
873 * jiffies is special (declared to be volatile) and its accesses are typically
874 * not marked; this test ensures that the compiler nor KCSAN gets confused about
875 * jiffies's declaration on different architectures.
878 static void test_jiffies_noreport(struct kunit *test)
880 bool match_never = false;
882 begin_test_checks(test_kernel_jiffies_reader, test_kernel_jiffies_reader);
884 match_never = report_available();
885 } while (!end_test_checks(match_never));
886 KUNIT_EXPECT_FALSE(test, match_never);
889 /* Test that racing accesses in seqlock critical sections are not reported. */
891 static void test_seqlock_noreport(struct kunit *test)
893 bool match_never = false;
895 begin_test_checks(test_kernel_seqlock_reader, test_kernel_seqlock_writer);
897 match_never = report_available();
898 } while (!end_test_checks(match_never));
899 KUNIT_EXPECT_FALSE(test, match_never);
903 * Test atomic builtins work and required instrumentation functions exist. We
904 * also test that KCSAN understands they're atomic by racing with them via
905 * test_kernel_atomic_builtins(), and expect no reports.
907 * The atomic builtins _SHOULD NOT_ be used in normal kernel code!
909 static void test_atomic_builtins(struct kunit *test)
911 bool match_never = false;
913 begin_test_checks(test_kernel_atomic_builtins, test_kernel_atomic_builtins);
917 kcsan_enable_current();
919 __atomic_store_n(&test_var, 42L, __ATOMIC_RELAXED);
920 KUNIT_EXPECT_EQ(test, 42L, __atomic_load_n(&test_var, __ATOMIC_RELAXED));
922 KUNIT_EXPECT_EQ(test, 42L, __atomic_exchange_n(&test_var, 20, __ATOMIC_RELAXED));
923 KUNIT_EXPECT_EQ(test, 20L, test_var);
926 KUNIT_EXPECT_TRUE(test, __atomic_compare_exchange_n(&test_var, &tmp, 30L,
929 KUNIT_EXPECT_EQ(test, tmp, 20L);
930 KUNIT_EXPECT_EQ(test, test_var, 30L);
931 KUNIT_EXPECT_FALSE(test, __atomic_compare_exchange_n(&test_var, &tmp, 40L,
934 KUNIT_EXPECT_EQ(test, tmp, 30L);
935 KUNIT_EXPECT_EQ(test, test_var, 30L);
937 KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED));
938 KUNIT_EXPECT_EQ(test, 31L, __atomic_fetch_sub(&test_var, 1, __ATOMIC_RELAXED));
939 KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_and(&test_var, 0xf, __ATOMIC_RELAXED));
940 KUNIT_EXPECT_EQ(test, 14L, __atomic_fetch_xor(&test_var, 0xf, __ATOMIC_RELAXED));
941 KUNIT_EXPECT_EQ(test, 1L, __atomic_fetch_or(&test_var, 0xf0, __ATOMIC_RELAXED));
942 KUNIT_EXPECT_EQ(test, 241L, __atomic_fetch_nand(&test_var, 0xf, __ATOMIC_RELAXED));
943 KUNIT_EXPECT_EQ(test, -2L, test_var);
945 __atomic_thread_fence(__ATOMIC_SEQ_CST);
946 __atomic_signal_fence(__ATOMIC_SEQ_CST);
948 kcsan_disable_current();
950 match_never = report_available();
951 } while (!end_test_checks(match_never));
952 KUNIT_EXPECT_FALSE(test, match_never);
956 * Generate thread counts for all test cases. Values generated are in interval
957 * [2, 5] followed by exponentially increasing thread counts from 8 to 32.
959 * The thread counts are chosen to cover potentially interesting boundaries and
960 * corner cases (2 to 5), and then stress the system with larger counts.
962 static const void *nthreads_gen_params(const void *prev, char *desc)
964 long nthreads = (long)prev;
966 if (nthreads < 0 || nthreads >= 32)
967 nthreads = 0; /* stop */
969 nthreads = 2; /* initial value */
970 else if (nthreads < 5)
972 else if (nthreads == 5)
977 if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
979 * Without any preemption, keep 2 CPUs free for other tasks, one
980 * of which is the main test case function checking for
981 * completion or failure.
983 const long min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0;
984 const long min_required_cpus = 2 + min_unused_cpus;
986 if (num_online_cpus() < min_required_cpus) {
987 pr_err_once("Too few online CPUs (%u < %ld) for test\n",
988 num_online_cpus(), min_required_cpus);
990 } else if (nthreads >= num_online_cpus() - min_unused_cpus) {
991 /* Use negative value to indicate last param. */
992 nthreads = -(num_online_cpus() - min_unused_cpus);
993 pr_warn_once("Limiting number of threads to %ld (only %d online CPUs)\n",
994 -nthreads, num_online_cpus());
998 snprintf(desc, KUNIT_PARAM_DESC_SIZE, "threads=%ld", abs(nthreads));
999 return (void *)nthreads;
1002 #define KCSAN_KUNIT_CASE(test_name) KUNIT_CASE_PARAM(test_name, nthreads_gen_params)
1003 static struct kunit_case kcsan_test_cases[] = {
1004 KCSAN_KUNIT_CASE(test_basic),
1005 KCSAN_KUNIT_CASE(test_concurrent_races),
1006 KCSAN_KUNIT_CASE(test_novalue_change),
1007 KCSAN_KUNIT_CASE(test_novalue_change_exception),
1008 KCSAN_KUNIT_CASE(test_unknown_origin),
1009 KCSAN_KUNIT_CASE(test_write_write_assume_atomic),
1010 KCSAN_KUNIT_CASE(test_write_write_struct),
1011 KCSAN_KUNIT_CASE(test_write_write_struct_part),
1012 KCSAN_KUNIT_CASE(test_read_atomic_write_atomic),
1013 KCSAN_KUNIT_CASE(test_read_plain_atomic_write),
1014 KCSAN_KUNIT_CASE(test_read_plain_atomic_rmw),
1015 KCSAN_KUNIT_CASE(test_zero_size_access),
1016 KCSAN_KUNIT_CASE(test_data_race),
1017 KCSAN_KUNIT_CASE(test_assert_exclusive_writer),
1018 KCSAN_KUNIT_CASE(test_assert_exclusive_access),
1019 KCSAN_KUNIT_CASE(test_assert_exclusive_access_writer),
1020 KCSAN_KUNIT_CASE(test_assert_exclusive_bits_change),
1021 KCSAN_KUNIT_CASE(test_assert_exclusive_bits_nochange),
1022 KCSAN_KUNIT_CASE(test_assert_exclusive_writer_scoped),
1023 KCSAN_KUNIT_CASE(test_assert_exclusive_access_scoped),
1024 KCSAN_KUNIT_CASE(test_jiffies_noreport),
1025 KCSAN_KUNIT_CASE(test_seqlock_noreport),
1026 KCSAN_KUNIT_CASE(test_atomic_builtins),
1030 /* ===== End test cases ===== */
1032 /* Concurrent accesses from interrupts. */
1034 static void access_thread_timer(struct timer_list *timer)
1036 static atomic_t cnt = ATOMIC_INIT(0);
1040 idx = (unsigned int)atomic_inc_return(&cnt) % ARRAY_SIZE(access_kernels);
1041 /* Acquire potential initialization. */
1042 func = smp_load_acquire(&access_kernels[idx]);
1047 /* The main loop for each thread. */
1049 static int access_thread(void *arg)
1051 struct timer_list timer;
1052 unsigned int cnt = 0;
1056 timer_setup_on_stack(&timer, access_thread_timer, 0);
1060 if (!timer_pending(&timer))
1061 mod_timer(&timer, jiffies + 1);
1063 /* Iterate through all kernels. */
1064 idx = cnt++ % ARRAY_SIZE(access_kernels);
1065 /* Acquire potential initialization. */
1066 func = smp_load_acquire(&access_kernels[idx]);
1070 } while (!torture_must_stop());
1071 del_timer_sync(&timer);
1072 destroy_timer_on_stack(&timer);
1074 torture_kthread_stopping("access_thread");
1079 static int test_init(struct kunit *test)
1081 unsigned long flags;
1085 spin_lock_irqsave(&observed.lock, flags);
1086 for (i = 0; i < ARRAY_SIZE(observed.lines); ++i)
1087 observed.lines[i][0] = '\0';
1088 observed.nlines = 0;
1089 spin_unlock_irqrestore(&observed.lock, flags);
1091 if (!torture_init_begin((char *)test->name, 1))
1094 if (WARN_ON(threads))
1097 for (i = 0; i < ARRAY_SIZE(access_kernels); ++i) {
1098 if (WARN_ON(access_kernels[i]))
1102 nthreads = abs((long)test->param_value);
1103 if (WARN_ON(!nthreads))
1106 threads = kcalloc(nthreads + 1, sizeof(struct task_struct *), GFP_KERNEL);
1107 if (WARN_ON(!threads))
1110 threads[nthreads] = NULL;
1111 for (i = 0; i < nthreads; ++i) {
1112 if (torture_create_kthread(access_thread, NULL, threads[i]))
1128 static void test_exit(struct kunit *test)
1130 struct task_struct **stop_thread;
1133 if (torture_cleanup_begin())
1136 for (i = 0; i < ARRAY_SIZE(access_kernels); ++i)
1137 WRITE_ONCE(access_kernels[i], NULL);
1140 for (stop_thread = threads; *stop_thread; stop_thread++)
1141 torture_stop_kthread(reader_thread, *stop_thread);
1147 torture_cleanup_end();
1150 static struct kunit_suite kcsan_test_suite = {
1152 .test_cases = kcsan_test_cases,
1156 static struct kunit_suite *kcsan_test_suites[] = { &kcsan_test_suite, NULL };
1159 static void register_tracepoints(struct tracepoint *tp, void *ignore)
1161 check_trace_callback_type_console(probe_console);
1162 if (!strcmp(tp->name, "console"))
1163 WARN_ON(tracepoint_probe_register(tp, probe_console, NULL));
1167 static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
1169 if (!strcmp(tp->name, "console"))
1170 tracepoint_probe_unregister(tp, probe_console, NULL);
1174 * We only want to do tracepoints setup and teardown once, therefore we have to
1175 * customize the init and exit functions and cannot rely on kunit_test_suite().
1177 static int __init kcsan_test_init(void)
1180 * Because we want to be able to build the test as a module, we need to
1181 * iterate through all known tracepoints, since the static registration
1184 for_each_kernel_tracepoint(register_tracepoints, NULL);
1185 return __kunit_test_suites_init(kcsan_test_suites);
1188 static void kcsan_test_exit(void)
1190 __kunit_test_suites_exit(kcsan_test_suites);
1191 for_each_kernel_tracepoint(unregister_tracepoints, NULL);
1192 tracepoint_synchronize_unregister();
1195 late_initcall(kcsan_test_init);
1196 module_exit(kcsan_test_exit);
1198 MODULE_LICENSE("GPL v2");
1199 MODULE_AUTHOR("Marco Elver <elver@google.com>");