Re: UML for arm64

From: Richard Weinberger <richard@nod.at>
To: Benjamin Berg <benjamin@sipsolutions.net>
Cc: Johannes Berg <johannes@sipsolutions.net>, robh <robh@kernel.org>,
	 anton ivanov <anton.ivanov@cambridgegreys.com>,
	 linux-um <linux-um@lists.infradead.org>,
	 Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: UML for arm64
Date: Thu, 22 Jun 2023 22:23:30 +0200 (CEST)	[thread overview]
Message-ID: <889626017.12829920.1687465410834.JavaMail.zimbra@nod.at> (raw)
In-Reply-To: <69707b721698594f96899c050871bcbb3594a9a1.camel@sipsolutions.net>

[CC'ing Al]

----- Ursprüngliche Mail -----
> Von: "Benjamin Berg" <benjamin@sipsolutions.net>
> An: "Johannes Berg" <johannes@sipsolutions.net>, "robh" <robh@kernel.org>, "richard" <richard@nod.at>, "anton ivanov"
> <anton.ivanov@cambridgegreys.com>
> CC: "linux-um" <linux-um@lists.infradead.org>
> Gesendet: Donnerstag, 22. Juni 2023 22:13:56
> Betreff: Re: UML for arm64

> 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

I think Al did some work in the past to support archs other than x86.
It was not arm64, though. ppc or sparc IIRC. Maybe he has some input.

> At least a lot of the register handling, but that will always be
> somewhat architecture specific.
> 
>> ... , 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.

I think reviving the seccomp patch set is a good idea in any case.
Maybe it is even a way to allow SMP support.

Thanks,
//richard

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