kcsan: Add atomic builtin test case

Adds test case to kcsan-test module, to test atomic builtin
instrumentation works.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/kcsan/kcsan-test.c b/kernel/kcsan/kcsan-test.c
index fed6fcb..721180c 100644 (file)
--- a/kernel/kcsan/kcsan-test.c
+++ b/kernel/kcsan/kcsan-test.c
@@ -390,6 +390,15 @@ static noinline void test_kernel_seqlock_writer(void)
        write_sequnlock_irqrestore(&test_seqlock, flags);
 }
 
+static noinline void test_kernel_atomic_builtins(void)
+{
+       /*
+        * Generate concurrent accesses, expecting no reports, ensuring KCSAN
+        * treats builtin atomics as actually atomic.
+        */
+       __atomic_load_n(&test_var, __ATOMIC_RELAXED);
+}
+
 /* ===== Test cases ===== */
 
 /* Simple test with normal data race. */
@@ -853,6 +862,59 @@ static void test_seqlock_noreport(struct kunit *test)
 }
 
 /*
+ * Test atomic builtins work and required instrumentation functions exist. We
+ * also test that KCSAN understands they're atomic by racing with them via
+ * test_kernel_atomic_builtins(), and expect no reports.
+ *
+ * The atomic builtins _SHOULD NOT_ be used in normal kernel code!
+ */
+static void test_atomic_builtins(struct kunit *test)
+{
+       bool match_never = false;
+
+       begin_test_checks(test_kernel_atomic_builtins, test_kernel_atomic_builtins);
+       do {
+               long tmp;
+
+               kcsan_enable_current();
+
+               __atomic_store_n(&test_var, 42L, __ATOMIC_RELAXED);
+               KUNIT_EXPECT_EQ(test, 42L, __atomic_load_n(&test_var, __ATOMIC_RELAXED));
+
+               KUNIT_EXPECT_EQ(test, 42L, __atomic_exchange_n(&test_var, 20, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, 20L, test_var);
+
+               tmp = 20L;
+               KUNIT_EXPECT_TRUE(test, __atomic_compare_exchange_n(&test_var, &tmp, 30L,
+                                                                   0, __ATOMIC_RELAXED,
+                                                                   __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, tmp, 20L);
+               KUNIT_EXPECT_EQ(test, test_var, 30L);
+               KUNIT_EXPECT_FALSE(test, __atomic_compare_exchange_n(&test_var, &tmp, 40L,
+                                                                    1, __ATOMIC_RELAXED,
+                                                                    __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, tmp, 30L);
+               KUNIT_EXPECT_EQ(test, test_var, 30L);
+
+               KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, 31L, __atomic_fetch_sub(&test_var, 1, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_and(&test_var, 0xf, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, 14L, __atomic_fetch_xor(&test_var, 0xf, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, 1L, __atomic_fetch_or(&test_var, 0xf0, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, 241L, __atomic_fetch_nand(&test_var, 0xf, __ATOMIC_RELAXED));
+               KUNIT_EXPECT_EQ(test, -2L, test_var);
+
+               __atomic_thread_fence(__ATOMIC_SEQ_CST);
+               __atomic_signal_fence(__ATOMIC_SEQ_CST);
+
+               kcsan_disable_current();
+
+               match_never = report_available();
+       } while (!end_test_checks(match_never));
+       KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+/*
  * Each test case is run with different numbers of threads. Until KUnit supports
  * passing arguments for each test case, we encode #threads in the test case
  * name (read by get_num_threads()). [The '-' was chosen as a stylistic
@@ -891,6 +953,7 @@ static struct kunit_case kcsan_test_cases[] = {
        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),
        {},
 };