Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.34 as permitted sender) client-ip=23.128.96.34;
MIME-Version: 1.0
References: <20231121220155.1217090-1-iii@linux.ibm.com> <20231121220155.1217090-24-iii@linux.ibm.com>
In-Reply-To: <20231121220155.1217090-24-iii@linux.ibm.com>
From:   Alexander Potapenko <glider@google.com>
Date:   Fri, 8 Dec 2023 17:56:29 +0100
Message-ID: <CAG_fn=UBt2A75bOgZmh7q_dS08d0PD8wJRHpoJyUDXRPRk_exA@mail.gmail.com>
Subject: Re: [PATCH v2 23/33] s390/boot: Add the KMSAN runtime stub
To:     Ilya Leoshkevich <iii@linux.ibm.com>
Cc:     Alexander Gordeev <agordeev@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Marco Elver <elver@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-s390@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Sven Schnelle <svens@linux.ibm.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, Nov 21, 2023 at 11:02=E2=80=AFPM Ilya Leoshkevich <iii@linux.ibm.co=
m> wrote:
>
> It should be possible to have inline functions in the s390 header
> files, which call kmsan_unpoison_memory(). The problem is that these
> header files might be included by the decompressor, which does not
> contain KMSAN runtime, causing linker errors.
>
> Not compiling these calls if __SANITIZE_MEMORY__ is not defined -
> either by changing kmsan-checks.h or at the call sites - may cause
> unintended side effects, since calling these functions from an
> uninstrumented code that is linked into the kernel is valid use case.
>
> One might want to explicitly distinguish between the kernel and the
> decompressor. Checking for a decompressor-specific #define is quite
> heavy-handed, and will have to be done at all call sites.
>
> A more generic approach is to provide a dummy kmsan_unpoison_memory()
> definition. This produces some runtime overhead, but only when building
> with CONFIG_KMSAN. The benefit is that it does not disturb the existing
> KMSAN build logic and call sites don't need to be changed.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>