diff options
| author | Marco Elver <elver@google.com> | 2020-02-25 15:32:58 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-03-25 09:56:00 -0700 |
| commit | 44656d3dc4f0dc20010d054f27397a4a1469fabf (patch) | |
| tree | 3cc0c8938304bb29992524788e001270d1afb4ca /kernel/kcsan/debugfs.c | |
| parent | 2402d0eae589a31ee7b1774cb220d84d0f5605b4 (diff) | |
kcsan: Add current->state to implicitly atomic accesses
Add volatile current->state to list of implicitly atomic accesses. This
is in preparation to eventually enable KCSAN on kernel/sched (which
currently still has KCSAN_SANITIZE := n).
Since accesses that match the special check in atomic.h are rare, it
makes more sense to move this check to the slow-path, avoiding the
additional compare in the fast-path. With the microbenchmark, a speedup
of ~6% is measured.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/kcsan/debugfs.c')
| -rw-r--r-- | kernel/kcsan/debugfs.c | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c index 2ff196123977..72ee188ebc54 100644 --- a/kernel/kcsan/debugfs.c +++ b/kernel/kcsan/debugfs.c @@ -74,25 +74,34 @@ void kcsan_counter_dec(enum kcsan_counter_id id) */ static noinline void microbenchmark(unsigned long iters) { + const struct kcsan_ctx ctx_save = current->kcsan_ctx; + const bool was_enabled = READ_ONCE(kcsan_enabled); cycles_t cycles; + /* We may have been called from an atomic region; reset context. */ + memset(¤t->kcsan_ctx, 0, sizeof(current->kcsan_ctx)); + /* + * Disable to benchmark fast-path for all accesses, and (expected + * negligible) call into slow-path, but never set up watchpoints. + */ + WRITE_ONCE(kcsan_enabled, false); + pr_info("KCSAN: %s begin | iters: %lu\n", __func__, iters); cycles = get_cycles(); while (iters--) { - /* - * We can run this benchmark from multiple tasks; this address - * calculation increases likelyhood of some accesses - * overlapping. Make the access type an atomic read, to never - * set up watchpoints and test the fast-path only. - */ - unsigned long addr = - iters % (CONFIG_KCSAN_NUM_WATCHPOINTS * PAGE_SIZE); - __kcsan_check_access((void *)addr, sizeof(long), KCSAN_ACCESS_ATOMIC); + unsigned long addr = iters & ((PAGE_SIZE << 8) - 1); + int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC : + (!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0); + __kcsan_check_access((void *)addr, sizeof(long), type); } cycles = get_cycles() - cycles; pr_info("KCSAN: %s end | cycles: %llu\n", __func__, cycles); + + WRITE_ONCE(kcsan_enabled, was_enabled); + /* restore context */ + current->kcsan_ctx = ctx_save; } /* |