Commit f9ea6319 authored by Marco Elver's avatar Marco Elver Committed by Paul E. McKenney
Browse files

kcsan: Add atomic builtin test case 



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

Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 883957b1

kernel/kcsan/kcsan-test.c

+63 −0
Original line number Diff line number Diff line
@@ -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. */
@@ -852,6 +861,59 @@ static void test_seqlock_noreport(struct kunit *test) 
	KUNIT_EXPECT_FALSE(test, match_never);

}



/*

 * Test atomic builtins work and required instrumentation functions exist. We

 * also test that KCSAN understands they're atomic by racing with them via

 * test_kernel_atomic_builtins(), and expect no reports.

 *

 * The atomic builtins _SHOULD NOT_ be used in normal kernel code!

 */

static void test_atomic_builtins(struct kunit *test)

{

	bool match_never = false;



	begin_test_checks(test_kernel_atomic_builtins, test_kernel_atomic_builtins);

	do {

		long tmp;



		kcsan_enable_current();



		__atomic_store_n(&test_var, 42L, __ATOMIC_RELAXED);

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



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

		KUNIT_EXPECT_EQ(test, 20L, test_var);



		tmp = 20L;

		KUNIT_EXPECT_TRUE(test, __atomic_compare_exchange_n(&test_var, &tmp, 30L,

								    0, __ATOMIC_RELAXED,

								    __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, tmp, 20L);

		KUNIT_EXPECT_EQ(test, test_var, 30L);

		KUNIT_EXPECT_FALSE(test, __atomic_compare_exchange_n(&test_var, &tmp, 40L,

								     1, __ATOMIC_RELAXED,

								     __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, tmp, 30L);

		KUNIT_EXPECT_EQ(test, test_var, 30L);



		KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, 31L, __atomic_fetch_sub(&test_var, 1, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_and(&test_var, 0xf, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, 14L, __atomic_fetch_xor(&test_var, 0xf, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, 1L, __atomic_fetch_or(&test_var, 0xf0, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, 241L, __atomic_fetch_nand(&test_var, 0xf, __ATOMIC_RELAXED));

		KUNIT_EXPECT_EQ(test, -2L, test_var);



		__atomic_thread_fence(__ATOMIC_SEQ_CST);

		__atomic_signal_fence(__ATOMIC_SEQ_CST);



		kcsan_disable_current();



		match_never = report_available();

	} while (!end_test_checks(match_never));

	KUNIT_EXPECT_FALSE(test, match_never);

}



/*

 * Each test case is run with different numbers of threads. Until KUnit supports

 * passing arguments for each test case, we encode #threads in the test case
@@ -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),

	{},

};