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authorMarco Elver <elver@google.com>2024-05-02 16:12:17 +0200
committerPaul E. McKenney <paulmck@kernel.org>2024-05-07 11:39:50 -0700
commit31f605a308e627f06e4e6ab77254473f1c90f0bf (patch)
tree40f60c986dd9199d0c12cc967206130237cca3aa /kernel/kcsan
parent39cd87c4eb2b893354f3b850f916353f2658ae6f (diff)
kcsan, compiler_types: Introduce __data_racy type qualifier
Based on the discussion at [1], it would be helpful to mark certain variables as explicitly "data racy", which would result in KCSAN not reporting data races involving any accesses on such variables. To do that, introduce the __data_racy type qualifier: struct foo { ... int __data_racy bar; ... }; In KCSAN-kernels, __data_racy turns into volatile, which KCSAN already treats specially by considering them "marked". In non-KCSAN kernels the type qualifier turns into no-op. The generated code between KCSAN-instrumented kernels and non-KCSAN kernels is already huge (inserted calls into runtime for every memory access), so the extra generated code (if any) due to volatile for few such __data_racy variables are unlikely to have measurable impact on performance. Link: https://lore.kernel.org/all/CAHk-=wi3iondeh_9V2g3Qz5oHTRjLsOpoy83hb58MVh=nRZe0A@mail.gmail.com/ [1] Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Marco Elver <elver@google.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/kcsan')
-rw-r--r--kernel/kcsan/kcsan_test.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index 015586217875..0c17b4c83e1c 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -304,6 +304,7 @@ 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);
@@ -358,6 +359,8 @@ 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);
@@ -1009,6 +1012,19 @@ static void test_data_race(struct kunit *test)
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)
{
@@ -1424,6 +1440,7 @@ static struct kunit_case kcsan_test_cases[] = {
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),