Fwd: ARM64 kernel crash

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

From:   "Chris Ward" <redacted>
To:     "Chris Ward" <redacted>
Date:   12/16/2021 12:22 PM
Subject:        [EXTERNAL] Fwd: ARM64 kernel crash



---------- Forwarded message ---------
From: Chris Ward <redacted>
Date: Thu, 16 Dec 2021 at 10:16
Subject: Fwd: ARM64 kernel crash
To: <redacted>


 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@arm.com>
Date: Wed, 15 Dec 2021 at 12:29
Subject: Re: ARM64 kernel crash
To: Mark Rutland <mark.rutland@arm.com>, <redacted>
Cc: <redacted>, Chris Ward <redacted>,
[off-list ref]


On 2021-12-15 10:53, Mark Rutland wrote:

Hi Chris,

On Wed, Dec 15, 2021 at 07:36:34AM +0000, Chris Ward wrote:

quoted

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@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.

quoted

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

quoted

an ARM64 embedded linux machine (i.e. not x86-64).

Can you share the config used? e.g. was that `defconfig`, or something 

else?

quoted

When trying to set up a file system on a ramdisk, we get a kernel crash 

for

quoted

sizes of ramdisk larger than 2GB while trying to 'dd if=/dev/zero ...' 

in

quoted

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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