[PATCH v2] arm64: compat: Implement misalignment fixups for multiword loads

[Arnd Bergmann]

On Tue, Aug 16, 2022 at 10:29 PM Ard Biesheuvel <ardb at kernel.org> wrote:
>
> Thanks for chiming in.
>
> At this point, it is really up to the maintainers to decide whether
> the maintenance burden is worth it. The code itself seems pretty
> uncontroversial afaict.
>
> Might other distros be in a similar situation? Or is this specific to Debian?

My guess is that this is the most prominent on Debian: Many others including
have discontinued or reduced support for 32-bit builds across architectures:
Ubuntu only supports "Core" with fewer packages on Raspberry Pi 2 but
not desktop or server, Opensuse Leap and Tumbleweed both distributes a
lot of board specific images but you have to know where to look as the main
page only advertises amd64/i686/arm64/ppc64le/s390x, Fedora stopped
entirely.

Android may be an interesting distro here: there are still a lot of phones
running a pure 32-bit userland on Cortex-A53/A55 CPUs, and there are a
large number of applications built for this. As far as I can tell, they tend to
run 32-bit kernels as well, but that is not going to work on newer processors
starting with Cortex-A76 big cores or Cortex-A510 little cores.

archlinuxarm supports 32-bit and 64-bit machines equally, but they
apparently avoid the build service problem by using distcc with
x86-to-arm cross compilers, and they don't seem to support
their 32-bit images on 64-bit hardware/kernel.

https://hub.docker.com/search?q=&source=verified&type=image&architecture=arm&image_filter=official
lists 98 "official" arm32 images plus countless ones in other categories.
I think these are popular in memory-constrained cloud hosting
setups on arm64, so the Alpine based images are probably the most
interesting ones because of their size, but they would run under
someone else's kernel.

        Arnd