The following commit has been merged into the locking/core branch of tip:
Commit-ID: f9ea63193135473ed6b6ff06f016eb6248100041
Gitweb: https://git.kernel.org/tip/f9ea63193135473ed6b6ff06f016eb6248100041
Author: Marco Elver <elver@xxxxxxxxxx>
AuthorDate: Fri, 03 Jul 2020 15:40:31 +02:00
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 24 Aug 2020 15:09:31 -07:00
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@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/kcsan/kcsan-test.c | 63 ++++++++++++++++++++++++++++++++++++++-
1 file changed, 63 insertions(+)
diff --git a/kernel/kcsan/kcsan-test.c b/kernel/kcsan/kcsan-test.c
index fed6fcb..721180c 100644
--- 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),
{},
};
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