On Fri, May 20, 2022 at 11:15AM +0800, Kefeng Wang wrote:
> As "kcsan: Support detecting a subset of missing memory barriers"[1]
> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
> more missing memory barrier, but arm64 don't have KCSAN instrumentation
> for barriers, so the new selftest test_barrier() and test cases for
> memory barrier instrumentation in kcsan_test module will fail, even
> panic on selftest.
>
> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
> defined the final instrumented version of these barriers, which will
> fix the above issues.
>
> Note, barrier instrumentation that can be disabled via __no_kcsan with
> appropriate compiler-support (and not just with objtool help), see
> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
> objtool support exists"), it adds disable_sanitizer_instrumentation to
> __no_kcsan attribute which will remove all sanitizer instrumentation fully
> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
>
> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@xxxxxxxxxx/
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/barrier.h | 12 ++++++------
> include/asm-generic/barrier.h | 4 ++++
> 2 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
> index 9f3e2c3d2ca0..2cfc4245d2e2 100644
> --- a/arch/arm64/include/asm/barrier.h
> +++ b/arch/arm64/include/asm/barrier.h
> @@ -50,13 +50,13 @@
> #define pmr_sync() do {} while (0)
> #endif
>
> -#define mb() dsb(sy)
> -#define rmb() dsb(ld)
> -#define wmb() dsb(st)
> +#define __mb() dsb(sy)
> +#define __rmb() dsb(ld)
> +#define __wmb() dsb(st)
>
> -#define dma_mb() dmb(osh)
> -#define dma_rmb() dmb(oshld)
> -#define dma_wmb() dmb(oshst)
> +#define __dma_mb() dmb(osh)
> +#define __dma_rmb() dmb(oshld)
> +#define __dma_wmb() dmb(oshst)
>
> #define io_stop_wc() dgh()
>
> diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
> index fd7e8fbaeef1..18863c50e9ce 100644
> --- a/include/asm-generic/barrier.h
> +++ b/include/asm-generic/barrier.h
> @@ -38,6 +38,10 @@
> #define wmb() do { kcsan_wmb(); __wmb(); } while (0)
> #endif
>
> +#ifdef __dma_mb
> +#define dma_mb() do { kcsan_mb(); __dma_mb(); } while (0)
> +#endif
The asm-generic changes might want to go into a separate patch, along
with the generic definition of dma_mb() if there's no __dma_mb, as
mentioned in the other email.
Thanks,
-- Marco
