linux-kernel - Re: [PATCH v7 4/7] mseal, system mappings: enable arm64

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Message-ID: <ea970928-ccea-4314-9cde-b64fa1a7824e@lucifer.local>
Date: Wed, 26 Feb 2025 05:25:59 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Jeff Xu <jeffxu@...omium.org>
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
        torvalds@...ux-foundation.org, vbabka@...e.cz, Liam.Howlett@...cle.com,
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Subject: Re: [PATCH v7 4/7] mseal, system mappings: enable arm64

On Tue, Feb 25, 2025 at 02:26:50PM -0800, Jeff Xu wrote:
> On Mon, Feb 24, 2025 at 10:20 PM Lorenzo Stoakes
> <lorenzo.stoakes@...cle.com> wrote:
> >
> > On Mon, Feb 24, 2025 at 10:52:43PM +0000, jeffxu@...omium.org wrote:
> > > From: Jeff Xu <jeffxu@...omium.org>
> > >
> > > Provide support for CONFIG_MSEAL_SYSTEM_MAPPINGS on arm64, covering
> > > the vdso, vvar, and compat-mode vectors and sigpage mappings.
> > >
> > > Production release testing passes on Android and Chrome OS.
> >
> > This is pretty limited (yes yes I know android is massive etc. but we must
> > account for all the weird and wonderful arm64 devices out there in context of
> > upstream :)
> >
> > Have you looking through all arm64-code relating to vdso, vvar, compat-mode
> > vectors, sigpage mapping and ensured nothing kernel-side relies upon relocation?
> > Some arches actually seem to want to do this. Pretty sure PPC does... so a bit
> > nervous of that.
> >
> Can you please point out where PPC munmap/mremap the vdso ?
>
> Previously, when you mentioned that, I thought you meant user space in
> PPC, I didn't realize that you meant that kernel code in PPC.  I
> tried, but didn't find anything, hence asking.

Jeff, please stick to replying to review. 'Have you looking through all
arm64-code'.

I ended up doing this myself yesterday and found no issues, as with x86-64.

I said I'm _pretty sure_ PPC does this. Liam mentioned something about
it. We can discuss it, and I can find specifics if + when you try to add
this to PPC.

Please try to respect my time...

>
> Thanks.
> -Jeff