Comment 0 for bug 2069534

Hi,

Linux 6.8 kernel fails to boot on ARM64 when any Linux command line param is more than 140 characters.

Test Machine
=============

Rockchip RK3399 based RockPro64 with latest u-boot 2024.07-rc3 in EFI mode booting grubaa64.efi

Reproduced on
==============
Ubuntu 22.04.4 with Linux HWE Proposed 6.8
Ubuntu 24.04 with Linux 6.8

Works on
=========
Ubuntu 22.04.4 with Linux 5.15, 6.6, 6.7, 6.9

Steps to reproduce
====================

1. Install Ubuntu 24.04 which comes with Linux 6.8 by default or Ubuntu 22.04.4 install Linux HWE 6.8 from https://launchpad.net/~canonical-kernel-team/+archive/ubuntu/proposed?field.series_filter=jammy

2. Edit /boot/grub/grub.cfg and add the following param to any boot entry with Linux 6.8

testparam=f081c381e7b54edcba27e5f790d47911a4cc3e726d8d256878d3df9175c020e0f081c381e7b54edcba27e5f790d47911a4cc3e726d8d256878d3df9175c020e0f081c381e7b5

3. Reboot the machine and select the boot entry in grub with the testparam as above.

4. Observe kernel never boots.

Cause
========

After bisecting the kernel, I found that the bug was introduced in Linux 6.8-rc1 ( and released in Linux 6.8 ) with commit

commit dc3f5aae06381b43bc9d0d416bd15ee1682940e9
Author: Ard Biesheuvel <email address hidden>
Date: Wed Nov 29 12:16:12 2023 +0100

    arm64: idreg-override: Avoid parameq() and parameqn()

This got fixed with Linux 6.9-rc1 and released in Linux 6.9 as part of rework

commit e223a449125571daa62debd8249fa4fc2da0a961
Author: Ard Biesheuvel <email address hidden>
Date: Wed Feb 14 13:28:50 2024 +0100

    arm64: idreg-override: Move to early mini C runtime

That got merged to Linux 6.9-rc1 with commit

commit 6d75c6f40a03c97e1ecd683ae54e249abb9d922b
Merge: fe46a7dd189e 1ef21fcd6a50
Author: Linus Torvalds <email address hidden>
Date: Thu Mar 14 15:35:42 2024 -0700

    Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Fix Options
=============

Option 1.
For Linux 6.8 the safest fix would be to revert

commit dc3f5aae06381b43bc9d0d416bd15ee1682940e9
Author: Ard Biesheuvel <email address hidden>
Date: Wed Nov 29 12:16:12 2023 +0100

    arm64: idreg-override: Avoid parameq() and parameqn()

Option 2.
Unless Ubuntu Team is interested in bringing the whole Mini C Runtime rework to Linux 6.8 with

commit 6d75c6f40a03c97e1ecd683ae54e249abb9d922b
Merge: fe46a7dd189e 1ef21fcd6a50
Author: Linus Torvalds <email address hidden>
Date: Thu Mar 14 15:35:42 2024 -0700

    Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Please revert the change in Linux 6.8

Thanks