Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220827213009.44316-1-alexander.sverdlin@nokia.com>
In-Reply-To: <20220827213009.44316-1-alexander.sverdlin@nokia.com>
From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Wed, 31 Aug 2022 11:30:53 +0200
Message-ID: <CACRpkdYgZK1oaceme6-EEuV3F=m1L5B3Y8t6z7Yxrx842dgrFw@mail.gmail.com>
Subject: Re: [PATCH] ARM: kasan: Only map modules if CONFIG_KASAN_VMALLOC=n
To:     Alexander A Sverdlin <alexander.sverdlin@nokia.com>
Cc:     kasan-dev@googlegroups.com,
        Lecopzer Chen <lecopzer.chen@mediatek.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Russell King <linux@armlinux.org.uk>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Sat, Aug 27, 2022 at 11:32 PM Alexander A Sverdlin
<alexander.sverdlin@nokia.com> wrote:

> -       create_mapping((void *)MODULES_VADDR, (void *)(PKMAP_BASE + PMD_SIZE));
> +       if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) && IS_ENABLED(CONFIG_MODULES))
> +               create_mapping((void *)MODULES_VADDR, (void *)(MODULES_END));

So the way I understand it is that modules are first and foremost loaded into
the area MODULES_VADDR .. MODULES_END, and then after that is out,
they get loaded into VMALLOC. See arch/arm/kernel/module.c, module_alloc().

If you do this, how are the addresses between MODULES_VADDR..MODULES_END
shadowed when using CONFIG_KASAN_VMALLOC?

> +       create_mapping((void *)PKMAP_BASE, (void *)(PKMAP_BASE + PMD_SIZE));

(Splitting this in two steps if probably good in any case.)

Pls keep me on CC for Kasan ARM patches, thanks! (Maybe I should add some
MAINTAINERS blurb.)

Yours,
Linus Walleij