linux-kernel - Re: [PATCH 00/32] kmsan: Enable on s390

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Message-ID: <7c222eff6c1baaa7647a9aa43a1ef19de9670230.camel@linux.ibm.com>
Date:   Thu, 16 Nov 2023 11:13:39 +0100
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>
Subject: Re: [PATCH 00/32] kmsan: Enable on s390

On Thu, 2023-11-16 at 09:42 +0100, Alexander Potapenko wrote:
> On Wed, Nov 15, 2023 at 9:34 PM Ilya Leoshkevich <iii@...ux.ibm.com>
> wrote:
> > 
> > Hi,
> > 
> > This series provides the minimal support for Kernel Memory
> > Sanitizer on
> > s390. Kernel Memory Sanitizer is clang-only instrumentation for
> > finding
> > accesses to uninitialized memory. The clang support for s390 has
> > already
> > been merged [1].
> > 
> > With this series, I can successfully boot s390 defconfig and
> > debug_defconfig with kmsan.panic=1. The tool found one real
> > s390-specific bug (fixed in master).
> > 
> > Best regards,
> > Ilya
> 
> Hi Ilya,
> 
> This is really impressive!
> Can you please share some instructions on how to run KMSAN in QEMU?
> I've never touched s390, but I'm assuming it should be possible?

I developed this natively (without cross-compilation or emulation,
just KVM), but I just gave the following a try on x86_64 and had some
success:

$ make LLVM=1 ARCH=s390 O=../linux-build-s390x-cross CC=clang-18
LD=s390x-linux-gnu-ld OBJCOPY=s390x-linux-gnu-objcopy debug_defconfig

$ make LLVM=1 ARCH=s390 O=../linux-build-s390x-cross CC=clang-18
LD=s390x-linux-gnu-ld OBJCOPY=s390x-linux-gnu-objcopy menuconfig

$ make LLVM=1 ARCH=s390 O=../linux-build-s390x-cross CC=clang-18
LD=s390x-linux-gnu-ld OBJCOPY=s390x-linux-gnu-objcopy -j24

$ qemu-system-s390x -M accel=tcg -smp 2 -m 4G -kernel ../linux-build-
s390x-cross/arch/s390/boot/bzImage -nographic -append 'root=/dev/vda1
rw console=ttyS1 nokaslr earlyprintk cio_ignore=all kmsan.panic=1' -
object rng-random,filename=/dev/urandom,id=rng0 -device virtio-rng-
ccw,rng=rng0

It's also possible to get a free s390 machine at [1].

[1] https://linuxone.cloud.marist.edu/oss