Fwd: ARM64 kernel crash

[Chris Ward]

Chris Ward
----- Forwarded by Chris Ward/UK/IBM on 12/16/2021 12:44 PM -----

From:   "Chris Ward" <tjcw01 at gmail.com>
To:     "Chris Ward" <tjcw at uk.ibm.com>
Date:   12/16/2021 12:22 PM
Subject:        [EXTERNAL] Fwd: ARM64 kernel crash



---------- Forwarded message ---------
From: Chris Ward <tjcw01 at gmail.com>
Date: Thu, 16 Dec 2021 at 10:16
Subject: Fwd: ARM64 kernel crash
To: <linux-arm-kernel at lists.infradead.org>


 I can build a new ARM kernel just fine, but I can't figure out how to
get this Xilinx chip to boot it. There is a tftpboot stage which I was
expecting to pull vmlinuz and initial ramdisk in, but the only things
in the tftpboot directory on the server is
tjcw:Downloads$ ssh cumulus.watson.ibm.com ls -l /tftpboot/cuttlefisharm1
total 24896
-rw-r--r-- 1 mohit mohit  8478220 Nov 24 13:14 image.ub
lrwxrwxrwx 1 mohit mohit       13 Nov  3 11:10 image.ub.cw -> 
image.ub.ubun
-rwxrwxrwx 1 mohit mohit 17010860 Nov  1 14:48 image.ub.peta
tjcw:Downloads$

and I don't think the image.ub is large enough to contain the kernel
and ramdisk.

Are there any other Xilinx users reading this who can tell me where to
put my newly-built kernel so that the boot process will boot it ?

---------- Forwarded message ---------
From: Robin Murphy <robin.murphy at arm.com>
Date: Wed, 15 Dec 2021 at 12:29
Subject: Re: ARM64 kernel crash
To: Mark Rutland <mark.rutland at arm.com>, <tjcw at cantab.net>
Cc: <linux-kernel at vger.kernel.org>, Chris Ward <tjcw01 at gmail.com>,
<linux-arm-kernel at lists.infradead.org>


On 2021-12-15 10:53, Mark Rutland wrote:
> Hi Chris,
>
> On Wed, Dec 15, 2021 at 07:36:34AM +0000, Chris Ward wrote:
>> Please personally cc me on answers/comments as I am not currently
>> subscribed to the LKML.
>> Trying again because I messed up the format badly the first time
>> round. Apologies for that.
>
> For arm/arm64 stuff, it's best to also Cc LAKML
> (linux-arm-kernel at lists.infradead.org). I've added that here, and for 
the
> benefit of others I've kept your entire mail as context. In future 
replies I
> will trim this.
>
> Please also note that kernel mailing list style is to reply inline (as 
I've don
> with this mail) rather than to top-post. That helps to keep discussions
> legible, and makes it possible to trim irrelevant context. Please keep 
any
> replies in kind with that style.
>
>> My team has a problem which is being bounced between Canonical support
>> and Xilinx support.
>> We are using kernel 5.4.0-xilinx-v2020.2 built from sources under
>> 
https://github.com/Xilinx/linux-xlnx 
 with a Ubuntu 20.04 userland on
>> an ARM64 embedded linux machine (i.e. not x86-64).
>
> Can you share the config used? e.g. was that `defconfig`, or something 
else?
>
>> When trying to set up a file system on a ramdisk, we get a kernel crash 
for
>> sizes of ramdisk larger than 2GB while trying to 'dd if=/dev/zero ...' 
in
>> preparation for issuing mkfs.

FWIW "larger than 2GB" immediately stands out as a massive red flag for
signed integer overflow leading to memory corruption *somewhere*, and
all the splats in the log below do look like they could simply be
fallout from that.

Building the vendor kernel with KASAN enabled might be another
worthwhile avenue of investigation - if that can flag up a wild memory
access at the point where it actually occurs, you've got more chance of
working backwards from there to the root cause.

Robin.


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