Quelle  kcsan_test.c   Sprache: C

// 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>
 */

#define pr_fmt(fmt) "kcsan_test: " fmt

#include <kunit/test.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/jiffies.h>
#include <linux/kcsan-checks.h>
#include <linux/kernel.h>
#include <linux/mutex.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>

#define KCSAN_TEST_REQUIRES(test, cond) do {   \
 if (!(cond))      \
  kunit_skip((test), "Test requires: " #cond); \
} while (0)

#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++], "");
  }
 }

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 bool is_atomic = (ty & KCSAN_ACCESS_ATOMIC);
  const bool is_scoped = (ty & KCSAN_ACCESS_SCOPED);
  const char *const access_type_aux =
    (is_atomic && is_scoped) ? " (marked, reordered)"
    : (is_atomic   ? " (marked)"
       : (is_scoped   ? " (reordered)" : ""));

  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, "");
    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;
}

static __always_inline const struct expect_report *
__report_set_scoped(struct expect_report *r, int accesses)
{
 BUILD_BUG_ON(accesses > 3);

 if (accesses & 1)
  r->access[0].type |= KCSAN_ACCESS_SCOPED;
 else
  r->access[0].type &= ~KCSAN_ACCESS_SCOPED;

 if (accesses & 2)
  r->access[1].type |= KCSAN_ACCESS_SCOPED;
 else
  r->access[1].type &= ~KCSAN_ACCESS_SCOPED;

 return r;
}

__no_kcsan
static bool report_matches_any_reordered(struct expect_report *r)
{
 return __report_matches(__report_set_scoped(r, 0)) ||
        __report_matches(__report_set_scoped(r, 1)) ||
        __report_matches(__report_set_scoped(r, 2)) ||
        __report_matches(__report_set_scoped(r, 3));
}

#ifdef CONFIG_KCSAN_WEAK_MEMORY
/* Due to reordering accesses, any access may appear as "(reordered)". */
#define report_matches report_matches_any_reordered
#else
#define report_matches __report_matches
#endif

/* ===== 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 long __data_racy test_data_racy;
static DEFINE_SEQLOCK(test_seqlock);
static DEFINE_SPINLOCK(test_spinlock);
static DEFINE_MUTEX(test_mutex);

/*
 * 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); }

/*
 * Generates a delay and some accesses that enter the runtime but do not produce
 * data races.
 */
static noinline void test_delay(int iter)
{
 while (iter--)
  sink_value(READ_ONCE(test_sink));
}

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_data_racy_qualifier(void) { test_data_racy++; }

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);
}

/*
 * Scoped assertions do trigger anywhere in scope. However, the report should
 * still only point at the start of the 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);
}

static noinline void test_kernel_xor_1bit(void)
{
 /* Do not report data races between the read-writes. */
 kcsan_nestable_atomic_begin();
 test_var ^= 0x10000;
 kcsan_nestable_atomic_end();
}

#define TEST_KERNEL_LOCKED(name, acquire, release)  \
 static noinline void test_kernel_##name(void)  \
 {       \
  long *flag = &test_struct.val[0];  \
  long v = 0;     \
  if (!(acquire))     \
   return;     \
  while (v++ < 100) {    \
   test_var++;    \
   barrier();    \
  }      \
  release;     \
  test_delay(10);     \
 }

TEST_KERNEL_LOCKED(with_memorder,
     cmpxchg_acquire(flag, 0, 1) == 0,
     smp_store_release(flag, 0));
TEST_KERNEL_LOCKED(wrong_memorder,
     cmpxchg_relaxed(flag, 0, 1) == 0,
     WRITE_ONCE(*flag, 0));
TEST_KERNEL_LOCKED(atomic_builtin_with_memorder,
     __atomic_compare_exchange_n(flag, &v, 1, 0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED),
     __atomic_store_n(flag, 0, __ATOMIC_RELEASE));
TEST_KERNEL_LOCKED(atomic_builtin_wrong_memorder,
     __atomic_compare_exchange_n(flag, &v, 1, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED),
     __atomic_store_n(flag, 0, __ATOMIC_RELAXED));

/* ===== Test cases ===== */

/*
 * Tests that various barriers have the expected effect on internal state. Not
 * exhaustive on atomic_t operations. Unlike the selftest, also checks for
 * too-strict barrier instrumentation; these can be tolerated, because it does
 * not cause false positives, but at least we should be aware of such cases.
 */
static void test_barrier_nothreads(struct kunit *test)
{
#ifdef CONFIG_KCSAN_WEAK_MEMORY
 struct kcsan_scoped_access *reorder_access = ¤t->kcsan_ctx.reorder_access;
#else
 struct kcsan_scoped_access *reorder_access = NULL;
#endif
 arch_spinlock_t arch_spinlock = __ARCH_SPIN_LOCK_UNLOCKED;
 atomic_t dummy = ATOMIC_INIT(0);

 KCSAN_TEST_REQUIRES(test, reorder_access != NULL);
 KCSAN_TEST_REQUIRES(test, IS_ENABLED(CONFIG_SMP));

#define __KCSAN_EXPECT_BARRIER(access_type, barrier, order_before, name)   \
 do {           \
  reorder_access->type = (access_type) | KCSAN_ACCESS_SCOPED;   \
  reorder_access->size = sizeof(test_var);     \
  barrier;         \
  KUNIT_EXPECT_EQ_MSG(test, reorder_access->size,     \
        order_before ? 0 : sizeof(test_var),   \
        "improperly instrumented type=(" #access_type "): " name); \
 } while (0)
#define KCSAN_EXPECT_READ_BARRIER(b, o)  __KCSAN_EXPECT_BARRIER(0, b, o, #b)
#define KCSAN_EXPECT_WRITE_BARRIER(b, o) __KCSAN_EXPECT_BARRIER(KCSAN_ACCESS_WRITE, b, o, #b)
#define KCSAN_EXPECT_RW_BARRIER(b, o)    __KCSAN_EXPECT_BARRIER(KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE, b, o, #b)

 /*
 * Lockdep initialization can strengthen certain locking operations due
 * to calling into instrumented files; "warm up" our locks.
 */
 spin_lock(&test_spinlock);
 spin_unlock(&test_spinlock);
 mutex_lock(&test_mutex);
 mutex_unlock(&test_mutex);

 /* Force creating a valid entry in reorder_access first. */
 test_var = 0;
 while (test_var++ < 1000000 && reorder_access->size != sizeof(test_var))
  __kcsan_check_read(&test_var, sizeof(test_var));
 KUNIT_ASSERT_EQ(test, reorder_access->size, sizeof(test_var));

 kcsan_nestable_atomic_begin(); /* No watchpoints in called functions. */

 KCSAN_EXPECT_READ_BARRIER(mb(), true);
 KCSAN_EXPECT_READ_BARRIER(wmb(), false);
 KCSAN_EXPECT_READ_BARRIER(rmb(), true);
 KCSAN_EXPECT_READ_BARRIER(smp_mb(), true);
 KCSAN_EXPECT_READ_BARRIER(smp_wmb(), false);
 KCSAN_EXPECT_READ_BARRIER(smp_rmb(), true);
 KCSAN_EXPECT_READ_BARRIER(dma_wmb(), false);
 KCSAN_EXPECT_READ_BARRIER(dma_rmb(), true);
 KCSAN_EXPECT_READ_BARRIER(smp_mb__before_atomic(), true);
 KCSAN_EXPECT_READ_BARRIER(smp_mb__after_atomic(), true);
 KCSAN_EXPECT_READ_BARRIER(smp_mb__after_spinlock(), true);
 KCSAN_EXPECT_READ_BARRIER(smp_store_mb(test_var, 0), true);
 KCSAN_EXPECT_READ_BARRIER(smp_load_acquire(&test_var), false);
 KCSAN_EXPECT_READ_BARRIER(smp_store_release(&test_var, 0), true);
 KCSAN_EXPECT_READ_BARRIER(xchg(&test_var, 0), true);
 KCSAN_EXPECT_READ_BARRIER(xchg_release(&test_var, 0), true);
 KCSAN_EXPECT_READ_BARRIER(xchg_relaxed(&test_var, 0), false);
 KCSAN_EXPECT_READ_BARRIER(cmpxchg(&test_var, 0,  0), true);
 KCSAN_EXPECT_READ_BARRIER(cmpxchg_release(&test_var, 0,  0), true);
 KCSAN_EXPECT_READ_BARRIER(cmpxchg_relaxed(&test_var, 0,  0), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_read(&dummy), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_read_acquire(&dummy), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_set(&dummy, 0), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_set_release(&dummy, 0), true);
 KCSAN_EXPECT_READ_BARRIER(atomic_add(1, &dummy), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_add_return(1, &dummy), true);
 KCSAN_EXPECT_READ_BARRIER(atomic_add_return_acquire(1, &dummy), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_add_return_release(1, &dummy), true);
 KCSAN_EXPECT_READ_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add(1, &dummy), true);
 KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_acquire(1, &dummy), false);
 KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_release(1, &dummy), true);
 KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
 KCSAN_EXPECT_READ_BARRIER(test_and_set_bit(0, &test_var), true);
 KCSAN_EXPECT_READ_BARRIER(test_and_clear_bit(0, &test_var), true);
 KCSAN_EXPECT_READ_BARRIER(test_and_change_bit(0, &test_var), true);
 KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock(0, &test_var), true);
 KCSAN_EXPECT_READ_BARRIER(__clear_bit_unlock(0, &test_var), true);
 KCSAN_EXPECT_READ_BARRIER(arch_spin_lock(&arch_spinlock), false);
 KCSAN_EXPECT_READ_BARRIER(arch_spin_unlock(&arch_spinlock), true);
 KCSAN_EXPECT_READ_BARRIER(spin_lock(&test_spinlock), false);
 KCSAN_EXPECT_READ_BARRIER(spin_unlock(&test_spinlock), true);
 KCSAN_EXPECT_READ_BARRIER(mutex_lock(&test_mutex), false);
 KCSAN_EXPECT_READ_BARRIER(mutex_unlock(&test_mutex), true);

 KCSAN_EXPECT_WRITE_BARRIER(mb(), true);
 KCSAN_EXPECT_WRITE_BARRIER(wmb(), true);
 KCSAN_EXPECT_WRITE_BARRIER(rmb(), false);
 KCSAN_EXPECT_WRITE_BARRIER(smp_mb(), true);
 KCSAN_EXPECT_WRITE_BARRIER(smp_wmb(), true);
 KCSAN_EXPECT_WRITE_BARRIER(smp_rmb(), false);
 KCSAN_EXPECT_WRITE_BARRIER(dma_wmb(), true);
 KCSAN_EXPECT_WRITE_BARRIER(dma_rmb(), false);
 KCSAN_EXPECT_WRITE_BARRIER(smp_mb__before_atomic(), true);
 KCSAN_EXPECT_WRITE_BARRIER(smp_mb__after_atomic(), true);
 KCSAN_EXPECT_WRITE_BARRIER(smp_mb__after_spinlock(), true);
 KCSAN_EXPECT_WRITE_BARRIER(smp_store_mb(test_var, 0), true);
 KCSAN_EXPECT_WRITE_BARRIER(smp_load_acquire(&test_var), false);
 KCSAN_EXPECT_WRITE_BARRIER(smp_store_release(&test_var, 0), true);
 KCSAN_EXPECT_WRITE_BARRIER(xchg(&test_var, 0), true);
 KCSAN_EXPECT_WRITE_BARRIER(xchg_release(&test_var, 0), true);
 KCSAN_EXPECT_WRITE_BARRIER(xchg_relaxed(&test_var, 0), false);
 KCSAN_EXPECT_WRITE_BARRIER(cmpxchg(&test_var, 0,  0), true);
 KCSAN_EXPECT_WRITE_BARRIER(cmpxchg_release(&test_var, 0,  0), true);
 KCSAN_EXPECT_WRITE_BARRIER(cmpxchg_relaxed(&test_var, 0,  0), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_read(&dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_read_acquire(&dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_set(&dummy, 0), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_set_release(&dummy, 0), true);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_add(1, &dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return(1, &dummy), true);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_acquire(1, &dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_release(1, &dummy), true);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add(1, &dummy), true);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_acquire(1, &dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_release(1, &dummy), true);
 KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
 KCSAN_EXPECT_WRITE_BARRIER(test_and_set_bit(0, &test_var), true);
 KCSAN_EXPECT_WRITE_BARRIER(test_and_clear_bit(0, &test_var), true);
 KCSAN_EXPECT_WRITE_BARRIER(test_and_change_bit(0, &test_var), true);
 KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock(0, &test_var), true);
 KCSAN_EXPECT_WRITE_BARRIER(__clear_bit_unlock(0, &test_var), true);
 KCSAN_EXPECT_WRITE_BARRIER(arch_spin_lock(&arch_spinlock), false);
 KCSAN_EXPECT_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock), true);
 KCSAN_EXPECT_WRITE_BARRIER(spin_lock(&test_spinlock), false);
 KCSAN_EXPECT_WRITE_BARRIER(spin_unlock(&test_spinlock), true);
 KCSAN_EXPECT_WRITE_BARRIER(mutex_lock(&test_mutex), false);
 KCSAN_EXPECT_WRITE_BARRIER(mutex_unlock(&test_mutex), true);

 KCSAN_EXPECT_RW_BARRIER(mb(), true);
 KCSAN_EXPECT_RW_BARRIER(wmb(), true);
 KCSAN_EXPECT_RW_BARRIER(rmb(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_mb(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_wmb(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_rmb(), true);
 KCSAN_EXPECT_RW_BARRIER(dma_wmb(), true);
 KCSAN_EXPECT_RW_BARRIER(dma_rmb(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_mb__before_atomic(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_mb__after_atomic(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_mb__after_spinlock(), true);
 KCSAN_EXPECT_RW_BARRIER(smp_store_mb(test_var, 0), true);
 KCSAN_EXPECT_RW_BARRIER(smp_load_acquire(&test_var), false);
 KCSAN_EXPECT_RW_BARRIER(smp_store_release(&test_var, 0), true);
 KCSAN_EXPECT_RW_BARRIER(xchg(&test_var, 0), true);
 KCSAN_EXPECT_RW_BARRIER(xchg_release(&test_var, 0), true);
 KCSAN_EXPECT_RW_BARRIER(xchg_relaxed(&test_var, 0), false);
 KCSAN_EXPECT_RW_BARRIER(cmpxchg(&test_var, 0,  0), true);
 KCSAN_EXPECT_RW_BARRIER(cmpxchg_release(&test_var, 0,  0), true);
 KCSAN_EXPECT_RW_BARRIER(cmpxchg_relaxed(&test_var, 0,  0), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_read(&dummy), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_read_acquire(&dummy), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_set(&dummy, 0), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_set_release(&dummy, 0), true);
 KCSAN_EXPECT_RW_BARRIER(atomic_add(1, &dummy), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_add_return(1, &dummy), true);
 KCSAN_EXPECT_RW_BARRIER(atomic_add_return_acquire(1, &dummy), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_add_return_release(1, &dummy), true);
 KCSAN_EXPECT_RW_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add(1, &dummy), true);
 KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_acquire(1, &dummy), false);
 KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_release(1, &dummy), true);
 KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
 KCSAN_EXPECT_RW_BARRIER(test_and_set_bit(0, &test_var), true);
 KCSAN_EXPECT_RW_BARRIER(test_and_clear_bit(0, &test_var), true);
 KCSAN_EXPECT_RW_BARRIER(test_and_change_bit(0, &test_var), true);
 KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock(0, &test_var), true);
 KCSAN_EXPECT_RW_BARRIER(__clear_bit_unlock(0, &test_var), true);
 KCSAN_EXPECT_RW_BARRIER(arch_spin_lock(&arch_spinlock), false);
 KCSAN_EXPECT_RW_BARRIER(arch_spin_unlock(&arch_spinlock), true);
 KCSAN_EXPECT_RW_BARRIER(spin_lock(&test_spinlock), false);
 KCSAN_EXPECT_RW_BARRIER(spin_unlock(&test_spinlock), true);
 KCSAN_EXPECT_RW_BARRIER(mutex_lock(&test_mutex), false);
 KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&test_mutex), true);
 KCSAN_EXPECT_READ_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
 KCSAN_EXPECT_WRITE_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
 KCSAN_EXPECT_RW_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
 kcsan_nestable_atomic_end();
}

/* Simple test with normal data race. */
__no_kcsan
static void test_basic(struct kunit *test)
{
 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 },
  },
 };
 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)
{
 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) },
  },
 };
 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)
{
 struct expect_report expect_rw = {
  .access = {
   { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
   { test_kernel_read, &test_var, sizeof(test_var), 0 },
  },
 };
 struct expect_report expect_ww = {
  .access = {
   { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
   { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
  },
 };
 bool match_expect = false;

 test_kernel_write_nochange(); /* Reset value. */
 begin_test_checks(test_kernel_write_nochange, test_kernel_read);
 do {
  match_expect = report_matches(&expect_rw) || report_matches(&expect_ww);
 } 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)
{
 struct expect_report expect_rw = {
  .access = {
   { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
   { test_kernel_read, &test_var, sizeof(test_var), 0 },
  },
 };
 struct expect_report expect_ww = {
  .access = {
   { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
   { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
  },
 };
 bool match_expect = false;

 test_kernel_write_nochange_rcu(); /* Reset value. */
 begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read);
 do {
  match_expect = report_matches(&expect_rw) || report_matches(&expect_ww);
 } 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)
{
 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)
{
 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)
{
 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)
{
 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)
{
 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;

 KCSAN_TEST_REQUIRES(test, !IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS));

 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)
{
 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;

 KCSAN_TEST_REQUIRES(test, !IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS));

 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)
{
 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 },
  },
 };
 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);
}

/* Test the __data_racy type qualifier. */
__no_kcsan
static void test_data_racy_qualifier(struct kunit *test)
{
 bool match_never = false;

 begin_test_checks(test_kernel_data_racy_qualifier, test_kernel_data_racy_qualifier);
 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)
{
 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)
{
 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)
{
 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 },
  },
 };
 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 },
  },
 };
 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)
{
 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)
{
 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 },
  },
 };
 struct expect_report expect_inscope = {
  .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_inscope = false;

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

__no_kcsan
static void test_assert_exclusive_access_scoped(struct kunit *test)
{
 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 },
  },
 };
 struct expect_report expect_start2 = {
  .access = { expect_start1.access[0], expect_start1.access[0] },
 };
 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_inscope));
 KUNIT_EXPECT_TRUE(test, match_expect_start);
 KUNIT_EXPECT_FALSE(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);
}

__no_kcsan
static void test_1bit_value_change(struct kunit *test)
{
 struct expect_report expect = {
  .access = {
   { test_kernel_read, &test_var, sizeof(test_var), 0 },
   { test_kernel_xor_1bit, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
  },
 };
 bool match = false;

 begin_test_checks(test_kernel_read, test_kernel_xor_1bit);
 do {
  match = IS_ENABLED(CONFIG_KCSAN_PERMISSIVE)
    ? report_available()
    : report_matches(&expect);
 } while (!end_test_checks(match));
 if (IS_ENABLED(CONFIG_KCSAN_PERMISSIVE))
  KUNIT_EXPECT_FALSE(test, match);
 else
  KUNIT_EXPECT_TRUE(test, match);
}

__no_kcsan
static void test_correct_barrier(struct kunit *test)
{
 struct expect_report expect = {
  .access = {
   { test_kernel_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
   { test_kernel_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
  },
 };
 bool match_expect = false;

 test_struct.val[0] = 0; /* init unlocked */
 begin_test_checks(test_kernel_with_memorder, test_kernel_with_memorder);
 do {
  match_expect = report_matches_any_reordered(&expect);
 } while (!end_test_checks(match_expect));
 KUNIT_EXPECT_FALSE(test, match_expect);
}

__no_kcsan
static void test_missing_barrier(struct kunit *test)
{
 struct expect_report expect = {
  .access = {
   { test_kernel_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
   { test_kernel_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
  },
 };
 bool match_expect = false;

 test_struct.val[0] = 0; /* init unlocked */
 begin_test_checks(test_kernel_wrong_memorder, test_kernel_wrong_memorder);
 do {
  match_expect = report_matches_any_reordered(&expect);
 } while (!end_test_checks(match_expect));
 if (IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
  KUNIT_EXPECT_TRUE(test, match_expect);
 else
  KUNIT_EXPECT_FALSE(test, match_expect);
}

__no_kcsan
static void test_atomic_builtins_correct_barrier(struct kunit *test)
{
 struct expect_report expect = {
  .access = {
   { test_kernel_atomic_builtin_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
   { test_kernel_atomic_builtin_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
  },
 };
 bool match_expect = false;

 test_struct.val[0] = 0; /* init unlocked */
 begin_test_checks(test_kernel_atomic_builtin_with_memorder,
     test_kernel_atomic_builtin_with_memorder);
 do {
  match_expect = report_matches_any_reordered(&expect);
 } while (!end_test_checks(match_expect));
 KUNIT_EXPECT_FALSE(test, match_expect);
}

__no_kcsan
static void test_atomic_builtins_missing_barrier(struct kunit *test)
{
 struct expect_report expect = {
  .access = {
   { test_kernel_atomic_builtin_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
   { test_kernel_atomic_builtin_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
  },
 };
 bool match_expect = false;

 test_struct.val[0] = 0; /* init unlocked */
 begin_test_checks(test_kernel_atomic_builtin_wrong_memorder,
     test_kernel_atomic_builtin_wrong_memorder);
 do {
  match_expect = report_matches_any_reordered(&expect);
 } while (!end_test_checks(match_expect));
 if (IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
  KUNIT_EXPECT_TRUE(test, match_expect);
 else
  KUNIT_EXPECT_FALSE(test, match_expect);
}

/*
 * Generate thread counts for all test cases. Values generated are in interval
 * [2, 5] followed by exponentially increasing thread counts from 8 to 32.
 *
 * The thread counts are chosen to cover potentially interesting boundaries and
 * corner cases (2 to 5), and then stress the system with larger counts.
 */
static const void *nthreads_gen_params(const void *prev, char *desc)
{
 long nthreads = (long)prev;

 if (nthreads < 0 || nthreads >= 32)
  nthreads = 0; /* stop */
 else if (!nthreads)
  nthreads = 2; /* initial value */
 else if (nthreads < 5)
  nthreads++;
 else if (nthreads == 5)
  nthreads = 8;
 else
  nthreads *= 2;

 if (!preempt_model_preemptible() ||
     !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 long min_unused_cpus = preempt_model_none() ? 2 : 0;
  const long min_required_cpus = 2 + min_unused_cpus;

  if (num_online_cpus() < min_required_cpus) {
   pr_err_once("Too few online CPUs (%u < %ld) for test\n",
        num_online_cpus(), min_required_cpus);
   nthreads = 0;
  } else if (nthreads >= num_online_cpus() - min_unused_cpus) {
   /* Use negative value to indicate last param. */
   nthreads = -(num_online_cpus() - min_unused_cpus);
   pr_warn_once("Limiting number of threads to %ld (only %d online CPUs)\n",
         -nthreads, num_online_cpus());
  }
 }

 snprintf(desc, KUNIT_PARAM_DESC_SIZE, "threads=%ld", abs(nthreads));
 return (void *)nthreads;
}

#define KCSAN_KUNIT_CASE(test_name) KUNIT_CASE_PARAM(test_name, nthreads_gen_params)
static struct kunit_case kcsan_test_cases[] = {
 KUNIT_CASE(test_barrier_nothreads),
 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_data_racy_qualifier),
 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),
 KCSAN_KUNIT_CASE(test_1bit_value_change),
 KCSAN_KUNIT_CASE(test_correct_barrier),
 KCSAN_KUNIT_CASE(test_missing_barrier),
 KCSAN_KUNIT_CASE(test_atomic_builtins_correct_barrier),
 KCSAN_KUNIT_CASE(test_atomic_builtins_missing_barrier),
 {},
};

/* ===== End test cases ===== */

/* 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());
 timer_delete_sync(&timer);
 timer_destroy_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 (strstr(test->name, "nothreads"))
  return 0;

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

 if (WARN_ON(threads))
  goto err;

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

 nthreads = abs((long)test->param_value);
 if (WARN_ON(!nthreads))
  goto err;

 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 (strstr(test->name, "nothreads"))
  return;

 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();
}

__no_kcsan
static void register_tracepoints(void)
{
 register_trace_console(probe_console, NULL);
}

__no_kcsan
static void unregister_tracepoints(void)
{
 unregister_trace_console(probe_console, NULL);
}

static int kcsan_suite_init(struct kunit_suite *suite)
{
 register_tracepoints();
 return 0;
}

static void kcsan_suite_exit(struct kunit_suite *suite)
{
 unregister_tracepoints();
 tracepoint_synchronize_unregister();
}

static struct kunit_suite kcsan_test_suite = {
 .name = "kcsan",
 .test_cases = kcsan_test_cases,
 .init = test_init,
 .exit = test_exit,
 .suite_init = kcsan_suite_init,
 .suite_exit = kcsan_suite_exit,
};

kunit_test_suites(&kcsan_test_suite);

MODULE_DESCRIPTION("KCSAN test suite");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Marco Elver ");