kcsan: Introduce KCSAN_ACCESS_ASSERT access type
The KCSAN_ACCESS_ASSERT access type may be used to introduce dummy reads
and writes to assert certain properties of concurrent code, where bugs
could not be detected as normal data races.
For example, a variable that is only meant to be written by a single
CPU, but may be read (without locking) by other CPUs must still be
marked properly to avoid data races. However, concurrent writes,
regardless if WRITE_ONCE() or not, would be a bug. Using
kcsan_check_access(&x, sizeof(x), KCSAN_ACCESS_ASSERT) would allow
catching such bugs.
To support KCSAN_ACCESS_ASSERT the following notable changes were made:
* If an access is of type KCSAN_ASSERT_ACCESS, disable various filters
that only apply to data races, so that all races that KCSAN observes are
reported.
* Bug reports that involve an ASSERT access type will be reported as
"KCSAN: assert: race in ..." instead of "data-race"; this will help
more easily distinguish them.
* Update a few comments to just mention 'races' where we do not always
mean pure data races.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/kcsan/kcsan.h b/kernel/kcsan/kcsan.h
index 8492da4..50078e7 100644
--- a/kernel/kcsan/kcsan.h
+++ b/kernel/kcsan/kcsan.h
@@ -40,6 +40,13 @@ enum kcsan_counter_id {
KCSAN_COUNTER_DATA_RACES,
/*
+ * Total number of ASSERT failures due to races. If the observed race is
+ * due to two conflicting ASSERT type accesses, then both will be
+ * counted.
+ */
+ KCSAN_COUNTER_ASSERT_FAILURES,
+
+ /*
* Number of times no watchpoints were available.
*/
KCSAN_COUNTER_NO_CAPACITY,