linux-kernel - Re: [PATCH 5/5] kasan: Extend KASAN mode kernel parameter

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Message-ID: <YUipcLV5CZ4x1i+1@arm.com>
Date:   Mon, 20 Sep 2021 16:32:00 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH 5/5] kasan: Extend KASAN mode kernel parameter

On Mon, Sep 13, 2021 at 09:14:24AM +0100, Vincenzo Frascino wrote:
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index 21dc03bc10a4..7f43e603bfbe 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -194,14 +194,20 @@ additional boot parameters that allow disabling KASAN or controlling features:
>  
>  - ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
>  
> -- ``kasan.mode=sync`` or ``=async`` controls whether KASAN is configured in
> -  synchronous or asynchronous mode of execution (default: ``sync``).
> +- ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
> +  is configured in synchronous, asynchronous or asymmetric mode of
> +  execution (default: ``sync``).
>    Synchronous mode: a bad access is detected immediately when a tag
>    check fault occurs.
>    Asynchronous mode: a bad access detection is delayed. When a tag check
>    fault occurs, the information is stored in hardware (in the TFSR_EL1
>    register for arm64). The kernel periodically checks the hardware and
>    only reports tag faults during these checks.
> +  Asymmetric mode: a bad access is detected immediately when a tag
> +  check fault occurs during a load operation and its detection is
> +  delayed during a store operation. For the store operations the kernel
> +  periodically checks the hardware and only reports tag faults during
> +  these checks.

Nitpick: I'd simply refer to the sync/async which already describe what
the kernel and hardware does, something like the tag checks synchronous
on reads and asynchronous on writes.

Otherwise:

Reviewed-by: Catalin Marinas <catalin.marinas@....com>