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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=I1uFp8IeY8Fnde7gaXz6xC0+QbudmeaaxYy0UL7lMjM=; b=UHg8KmM9SmQvx6/MLJw42Nv1PabppYP4onp2LzmVn54uOOzd0QUreeIuTZ9A4oqfG+ T0nm9OyYc8hueX3bssC++pVFOcAyKsRUVvKQrzZqLBrHzeErMtiTfxbevDL132Brabma kk+eDcnOZHiev6B2rMool7cvIN0WdbK4IC5i/0yrf2YoFpWL0bIi2I7dLT+2mNDqgv5R BJi5EITd3r2O5Cm6Q2kIQl7TwD7+zH5e3LuUCw2UUtV8pBOtqB5IX7Nsvn3kjYGr8iP5 WX6s3DUKpUEu25WRZQbaRjC5RnBu3xTRPKunv+RozyTdcpFCg3vPBtNmjqvjdclguVOU W+oA== X-Gm-Message-State: AOAM530A2yxEaeeTcxt85iYBpl7zOgYMaVBI3eA1Dp+JwMK/5nyAciNq dBcu7OHubq6cpIjc5KWfan6oCHi9oMI7UYKvKyTQzQ== X-Google-Smtp-Source: ABdhPJzwOStEEZx2yraMS2XL2XwXeh2/2X2VOF+J3d8QppfLSpf8mqZ+yEW3g1VSyQXH/vxLYX5UgeOTEYKTjsVrsmk= X-Received: by 2002:a05:620a:983:: with SMTP id x3mr14661120qkx.231.1611236987731; Thu, 21 Jan 2021 05:49:47 -0800 (PST) MIME-Version: 1.0 References: <20210119111319.GH1551@shell.armlinux.org.uk> <20210119114341.GI1551@shell.armlinux.org.uk> <20210119123659.GJ1551@shell.armlinux.org.uk> <20210119194827.GL1551@shell.armlinux.org.uk> <20210121131444.GP1551@shell.armlinux.org.uk> In-Reply-To: <20210121131444.GP1551@shell.armlinux.org.uk> From: Dmitry Vyukov Date: Thu, 21 Jan 2021 14:49:35 +0100 Message-ID: Subject: Re: Arm + KASAN + syzbot To: Russell King - ARM Linux admin X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_084951_762103_C8A01AEE X-CRM114-Status: GOOD ( 30.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Arnd Bergmann , Linus Walleij , Krzysztof Kozlowski , syzkaller , kasan-dev , Hailong Liu , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 21, 2021 at 2:14 PM Russell King - ARM Linux admin wrote: > > On Tue, Jan 19, 2021 at 07:48:27PM +0000, Russell King - ARM Linux admin wrote: > > My knowledge about this is limited to qemu being used for KVM. > > > > Firstly, there is are no block devices except for MTD, USB, or CF > > based block devices in the Versatile Express hardware. So, the DTB > > contains no block devices. > > > > In your first case above, it is likely that QEMU modifies the passed > > DTB to add PCIe devices to describe a virtio block device. > > > > In this case, because QEMU has no visibility of the appended DTB, it > > can't modify it, so the kernel only knows about devices found on the > > real hardware. Hence, any of the "special" virtio devices that QEMU > > use likely won't be found. > > > > I'm not sure how QEMU adds those (you're probably in a better position > > than I to boot using your first method, grab a copy of the DTB that > > the booted kernel used from /sys/firmware/fdt, and use dtc to turn it > > back into a dts and see what the changes are. > > > > I suspect you'll find that there's a new PCIe controller been added > > by QEMU, behind which will be a load of virtio devices for things like > > network and the "vda" block device. > > It may also be of relevance that 5.9 + a revert of the font changes > boots for me under KVM, but 5.10 does not. > > The font changes were: > 6735b4632def Fonts: Support FONT_EXTRA_WORDS macros for built-in fonts > > 5.10-rc1 similarly does not, but bisecting that brings me to: > 316cdaa1158a net: add option to not create fall-back tunnels in root-ns as well > > which seems entirely unrelated, and looks like a false outcome. > > I've tried going back to 5.10 and turning off CONFIG_STRICT_KERNEL_RWX. > Still doesn't boot. > > I've tried reverting the changes to the decompressor between 5.9 and > 5.10. Still doesn't boot. > > Asking for a memory dump in ELF coredump format of the guest doesn't give > anything useful - I can see that the kernel has been decompressed, but > the BSS is completely uninitialised. It looks like the LPAE page tables > have been initialised. > > The PC value in the ELF coredump seems to be spinning through a large > amount of memory (physical address) and the CPSR is 0x197, which > suggests it's taken an abort without any vectors setup. > > I'm currently struggling to find a way to debug what's going on. I wonder if qemu has some kind of tracing that may be useful in such cases. Some googling shows this, which seems that it can give a trace of all PCs (which is a reasonable feature to have), it may show where things go wrong: https://rwmj.wordpress.com/2016/03/17/tracing-qemu-guest-execution/ https://github.com/qemu/qemu/blob/master/docs/devel/tracing.txt But I never used such heavy-weight artillery myself. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel