linux-kernel - Re: [PATCH v3 2/2] arm64: kcsan: Support detecting more missing memory barriers

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Date:   Mon, 23 May 2022 10:23:59 +0200
From:   Marco Elver <elver@...gle.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 2/2] arm64: kcsan: Support detecting more missing
 memory barriers

On Mon, 23 May 2022 at 03:50, Kefeng Wang <wangkefeng.wang@...wei.com> 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 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 for Clang 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@google.com/
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>

Acked-by: Marco Elver <elver@...gle.com>

> ---
>  arch/arm64/include/asm/barrier.h | 12 ++++++------
>  1 file changed, 6 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()
>
> --
> 2.35.3
>