From: Marco Elver <elver@google.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Alexander Potapenko <glider@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev@googlegroups.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 08/11] kasan: docs: update HW_TAGS implementation details section
Date: Fri, 12 Mar 2021 16:09:37 +0100 [thread overview]
Message-ID: <YEuEMajjvbyByzJA@elver.google.com> (raw)
In-Reply-To: <ee2caf4c138cc1fd239822c2abefd5af6c057744.1615559068.git.andreyknvl@google.com>
On Fri, Mar 12, 2021 at 03:24PM +0100, Andrey Konovalov wrote:
> Update the "Implementation details" section for HW_TAGS KASAN:
>
> - Punctuation, readability, and other minor clean-ups.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
> ---
> Documentation/dev-tools/kasan.rst | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index 5873d80cc1fd..2744ae6347c6 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -270,35 +270,35 @@ memory.
> Hardware tag-based KASAN
> ~~~~~~~~~~~~~~~~~~~~~~~~
>
> -Hardware tag-based KASAN is similar to the software mode in concept, but uses
> +Hardware tag-based KASAN is similar to the software mode in concept but uses
> hardware memory tagging support instead of compiler instrumentation and
> shadow memory.
>
> Hardware tag-based KASAN is currently only implemented for arm64 architecture
> and based on both arm64 Memory Tagging Extension (MTE) introduced in ARMv8.5
> -Instruction Set Architecture, and Top Byte Ignore (TBI).
> +Instruction Set Architecture and Top Byte Ignore (TBI).
>
> Special arm64 instructions are used to assign memory tags for each allocation.
> Same tags are assigned to pointers to those allocations. On every memory
> -access, hardware makes sure that tag of the memory that is being accessed is
> -equal to tag of the pointer that is used to access this memory. In case of a
> -tag mismatch a fault is generated and a report is printed.
> +access, hardware makes sure that the tag of the memory that is being accessed is
> +equal to the tag of the pointer that is used to access this memory. In case of a
> +tag mismatch, a fault is generated, and a report is printed.
>
> Hardware tag-based KASAN uses 0xFF as a match-all pointer tag (accesses through
> -pointers with 0xFF pointer tag aren't checked). The value 0xFE is currently
> +pointers with the 0xFF pointer tag are not checked). The value 0xFE is currently
> reserved to tag freed memory regions.
>
> -Hardware tag-based KASAN currently only supports tagging of
> -kmem_cache_alloc/kmalloc and page_alloc memory.
> +Hardware tag-based KASAN currently only supports tagging of slab 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.
> +If the hardware does not support MTE (pre ARMv8.5), hardware tag-based KASAN
> +will not be enabled. In this case, all KASAN 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
> +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 does not
> support MTE (but supports TBI).
>
> -Hardware tag-based KASAN only reports the first found bug. After that MTE tag
> +Hardware tag-based KASAN only reports the first found bug. After that, MTE tag
> checking gets disabled.
>
> Shadow memory
> --
> 2.31.0.rc2.261.g7f71774620-goog
>
next prev parent reply other threads:[~2021-03-12 15:09 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 14:24 [PATCH v2 01/11] kasan: docs: clean up sections Andrey Konovalov
2021-03-12 14:24 ` [PATCH v2 02/11] kasan: docs: update overview section Andrey Konovalov
2021-03-12 15:07 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 03/11] kasan: docs: update usage section Andrey Konovalov
2021-03-12 15:07 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 04/11] kasan: docs: update error reports section Andrey Konovalov
2021-03-12 15:08 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 05/11] kasan: docs: update boot parameters section Andrey Konovalov
2021-03-12 15:08 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 06/11] kasan: docs: update GENERIC implementation details section Andrey Konovalov
2021-03-12 15:08 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 07/11] kasan: docs: update SW_TAGS " Andrey Konovalov
2021-03-12 15:09 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 08/11] kasan: docs: update HW_TAGS " Andrey Konovalov
2021-03-12 15:09 ` Marco Elver [this message]
2021-03-12 14:24 ` [PATCH v2 09/11] kasan: docs: update shadow memory section Andrey Konovalov
2021-03-12 15:09 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 10/11] kasan: docs: update ignoring accesses section Andrey Konovalov
2021-03-12 15:10 ` Marco Elver
2021-03-12 14:24 ` [PATCH v2 11/11] kasan: docs: update tests section Andrey Konovalov
2021-03-12 15:11 ` Marco Elver
2021-03-12 15:06 ` [PATCH v2 01/11] kasan: docs: clean up sections Marco Elver
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