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kcsan: Introduce scoped ASSERT_EXCLUSIVE macros

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Introduce ASSERT_EXCLUSIVE_*_SCOPED(), which provide an intuitive
interface to use the scoped-access feature, without having to explicitly
mark the start and end of the desired scope. Basing duration of the
checks on scope avoids accidental misuse and resulting false positives,
which may be hard to debug. See added comments for usage.

The macros are implemented using __attribute__((__cleanup__(func))),
which is supported by all compilers that currently support KCSAN.

Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Marco Elver
2020-03-25 17:41:58 +01:00
committed by Paul E. McKenney
parent 9967683ce5
commit d8949ef1d9
3 changed files with 89 additions and 3 deletions
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16
kernel/kcsan/debugfs.c
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@@ -110,6 +110,7 @@ static noinline void microbenchmark(unsigned long iters)
*/
static long test_dummy;
static long test_flags;
static long test_scoped;
static noinline void test_thread(unsigned long iters)
{
const long CHANGE_BITS = 0xff00ff00ff00ff00L;
@@ -120,7 +121,8 @@ static noinline void test_thread(unsigned long iters)
memset(&current->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
pr_info("KCSAN: %s begin | iters: %lu\n", __func__, iters);
pr_info("test_dummy@%px, test_flags@%px\n", &test_dummy, &test_flags);
pr_info("test_dummy@%px, test_flags@%px, test_scoped@%px,\n",
&test_dummy, &test_flags, &test_scoped);
cycles = get_cycles();
while (iters--) {
@@ -141,6 +143,18 @@ static noinline void test_thread(unsigned long iters)
test_flags ^= CHANGE_BITS; /* generate value-change */
__kcsan_check_write(&test_flags, sizeof(test_flags));
BUG_ON(current->kcsan_ctx.scoped_accesses.prev);
{
/* Should generate reports anywhere in this block. */
ASSERT_EXCLUSIVE_WRITER_SCOPED(test_scoped);
ASSERT_EXCLUSIVE_ACCESS_SCOPED(test_scoped);
BUG_ON(!current->kcsan_ctx.scoped_accesses.prev);
/* Unrelated accesses. */
__kcsan_check_access(&cycles, sizeof(cycles), 0);
__kcsan_check_access(&cycles, sizeof(cycles), KCSAN_ACCESS_ATOMIC);
}
BUG_ON(current->kcsan_ctx.scoped_accesses.prev);
}
cycles = get_cycles() - cycles;