UML for arm64

[Anton Ivanov]

On 22/06/2023 21:13, Benjamin Berg wrote:
> Hi,
> 
> On Thu, 2023-06-22 at 21:41 +0200, Johannes Berg wrote:
>> On Thu, 2023-06-22 at 13:22 -0600, Rob Herring wrote:
>>> I'm interested in getting UML working on Arm. Is anyone aware of any
>>> efforts to do this already?
>>
>> Not me ... But yeah, agree that it seems likely to require some
>> refactoring, even if _some_ degree of attempts were made to keep arch-
>> specific things there ...
>>
>> There might be a ton of arch-specific things in the ptrace code too
> 
> At least a lot of the register handling, but that will always be
> somewhat architecture specific.

In the arm case there may be some paging issues.

Arm pages are not necessarily 4096. I tried to implement non-4096 page support for UML a couple of years ago and gave up.

It will be nice if we manage to fix this. End of the day - UML uses mmap(), so it should be able to use page sizing which differs from the host one.

> 
>> ... , so perhaps it'd be easier to start with the seccomp-based model:
>>
>> https://patchwork.ozlabs.org/project/linux-um/list/?series=329466
>>
>> But that's not really done yet either.
> 
> Yes, though I have quite some updates locally that solve the security
> issues (i.e. prevent host syscalls from userspace). So, it does need
> rebasing and I am sure bugfixes, but I think it is getting into a
> pretty good shape overall.
> 
> Either way, the old patchset will give you a good idea about how it all
> works, the changes are mostly in the details. I am happy to push out a
> new version sooner rather than later if it might help with any efforts
> on your side.
> 
> Benjamin
> 
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Anton R. Ivanov
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