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References: <20220225123953.3251327-1-alexandre.ghiti@canonical.com>
In-Reply-To: <20220225123953.3251327-1-alexandre.ghiti@canonical.com>
From:   Marco Elver <elver@google.com>
Date:   Fri, 25 Feb 2022 14:05:42 +0100
Message-ID: <CANpmjNN304EZfFN2zobxKGXbXWXAfr92nP1KvtR7j-YqSFShvQ@mail.gmail.com>
Subject: Re: [PATCH -fixes v3 0/6] Fixes KASAN and other along the way
To:     Alexandre Ghiti <alexandre.ghiti@canonical.com>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Aleksandr Nogikh <nogikh@google.com>,
        Nick Hu <nickhu@andestech.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        kasan-dev@googlegroups.com
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On Fri, 25 Feb 2022 at 13:40, Alexandre Ghiti
<alexandre.ghiti@canonical.com> wrote:
>
> As reported by Aleksandr, syzbot riscv is broken since commit
> 54c5639d8f50 ("riscv: Fix asan-stack clang build"). This commit actually
> breaks KASAN_INLINE which is not fixed in this series, that will come later
> when found.
>
> Nevertheless, this series fixes small things that made the syzbot
> configuration + KASAN_OUTLINE fail to boot.
>
> Note that even though the config at [1] boots fine with this series, I
> was not able to boot the small config at [2] which fails because
> kasan_poison receives a really weird address 0x4075706301000000 (maybe a
> kasan person could provide some hint about what happens below in
> do_ctors -> __asan_register_globals):

asan_register_globals is responsible for poisoning redzones around
globals. As hinted by 'do_ctors', it calls constructors, and in this
case a compiler-generated constructor that calls
__asan_register_globals with metadata generated by the compiler. That
metadata contains information about global variables. Note, these
constructors are called on initial boot, but also every time a kernel
module (that has globals) is loaded.

It may also be a toolchain issue, but it's hard to say. If you're
using GCC to test, try Clang (11 or later), and vice-versa.