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Date:   Fri, 31 Jul 2020 15:21:27 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Marco Elver <elver@google.com>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Walter Wu <walter-zh.wu@mediatek.com>,
        Elena Petrova <lenaptr@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: Re: [PATCH 2/4] kasan, arm64: don't instrument functions that enable
 kasan
Message-ID: <20200731142126.GE29569@gaia>
References: <cover.1596199677.git.andreyknvl@google.com>
 <55d432671a92e931ab8234b03dc36b14d4c21bfb.1596199677.git.andreyknvl@google.com>
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On Fri, Jul 31, 2020 at 03:20:39PM +0200, Andrey Konovalov wrote:
> This patch prepares Software Tag-Based KASAN for stack tagging support.
> 
> With stack tagging enabled, KASAN tags stack variable in each function
> in its prologue. In start_kernel() stack variables get tagged before KASAN
> is enabled via setup_arch()->kasan_init(). As the result the tags for
> start_kernel()'s stack variables end up in the temporary shadow memory.
> Later when KASAN gets enabled, switched to normal shadow, and starts
> checking tags, this leads to false-positive reports, as proper tags are
> missing in normal shadow.
> 
> Disable KASAN instrumentation for start_kernel(). Also disable it for
> arm64's setup_arch() as a precaution (it doesn't have any stack variables
> right now).
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

For arm64:

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