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    Subject[PATCH 02/11] kasan: clarify HW_TAGS impact on TBI
    From
    Mention in the documentation that enabling CONFIG_KASAN_HW_TAGS
    always results in in-kernel TBI (Top Byte Ignore) being enabled.

    Also do a few minor documentation cleanups.

    Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    Link: https://linux-review.googlesource.com/id/Iba2a6697e3c6304cb53f89ec61dedc77fa29e3ae
    ---
    Documentation/dev-tools/kasan.rst | 16 +++++++++++-----
    1 file changed, 11 insertions(+), 5 deletions(-)

    diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
    index 0fc3fb1860c4..26c99852a852 100644
    --- a/Documentation/dev-tools/kasan.rst
    +++ b/Documentation/dev-tools/kasan.rst
    @@ -147,15 +147,14 @@ negative values to distinguish between different kinds of inaccessible memory
    like redzones or freed memory (see mm/kasan/kasan.h).

    In the report above the arrows point to the shadow byte 03, which means that
    -the accessed address is partially accessible.
    -
    -For tag-based KASAN this last report section shows the memory tags around the
    -accessed address (see `Implementation details`_ section).
    +the accessed address is partially accessible. For tag-based KASAN modes this
    +last report section shows the memory tags around the accessed address
    +(see the `Implementation details`_ section).

    Boot parameters
    ~~~~~~~~~~~~~~~

    -Hardware tag-based KASAN mode (see the section about different mode below) is
    +Hardware tag-based KASAN mode (see the section about various modes below) is
    intended for use in production as a security mitigation. Therefore it supports
    boot parameters that allow to disable KASAN competely or otherwise control
    particular KASAN features.
    @@ -305,6 +304,13 @@ reserved to tag freed memory regions.
    Hardware tag-based KASAN currently only supports tagging of
    kmem_cache_alloc/kmalloc and page_alloc memory.

    +If the hardware doesn't support MTE (pre ARMv8.5), hardware tag-based KASAN
    +won't be enabled. In this case all boot parameters are ignored.
    +
    +Note, that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI being
    +enabled. Even when kasan.mode=off is provided, or when the hardware doesn't
    +support MTE (but supports TBI).
    +
    What memory accesses are sanitised by KASAN?
    --------------------------------------------

    --
    2.29.2.729.g45daf8777d-goog
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