Re: [PATCH 07/11] kasan: add compiler barriers to KUNIT_EXPECT_KASAN_FAIL
From: Andrey Konovalov <hidden>
Date: 2021-01-12 22:01:54
Also in:
linux-mm, lkml
On Tue, Jan 12, 2021 at 8:50 PM Andrey Konovalov [off-list ref] wrote:
On Tue, Jan 12, 2021 at 9:18 AM Alexander Potapenko [off-list ref] wrote:quoted
On Tue, Jan 5, 2021 at 7:28 PM Andrey Konovalov [off-list ref] wrote:quoted
It might not be obvious to the compiler that the expression must be executed between writing and reading to fail_data. In this case, the compiler might reorder or optimize away some of the accesses, and the tests will fail.Have you seen this happen in practice?Yes.quoted
Are these accesses to fail_data that are optimized (in which case we could make it volatile)?Yes. AFAIU compiler doesn't expect expression to change fail_data fields, no those accesses and checks are optimized away.
Ah, actually no, it reorders the expression and puts it after fail_data fields checks. That's why I put the barriers.
quoted
Note that compiler barriers won't probably help against removing memory accesses, they only prevent reordering.
But using WRITE/READ_ONCE() might also be a good idea, as technically the compiler can optimize away the accesses. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel