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Message-ID: <CABi2SkXcgB1Zjztqc1W4M-5j9z_wMCRaEtK-wLL3x9_qC1aGHQ@mail.gmail.com>
Date: Tue, 25 Feb 2025 16:12:40 -0800
From: Jeff Xu <jeffxu@...omium.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com, 
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Subject: 

On Tue, Feb 25, 2025 at 7:18 AM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> Jeff - looking further in this series, I asked for a couple things for this
> series which you've not provided:
>
> 1. Some assurance based on code that the kernel-side code doesn't rely on
>    VDSO/VVAR etc. mapping. I gave up waiting for this and went and checked
>    myself, it looks fine for arm64, x86-64. But it might have been nice had
>    you done it :) Apologies if you had and I just missed it.
>
Thanks for checking this.
Do ppc in kernel code unmap/remap  vdso ?

I am aware that userspace can remap/unmap special mappings, but I
don't know if the kernel will remap/unmap a special mapping. Could you
please point out the code ?


> 2. Tests - could you please add some tests to assert that mremap() fails
>    for VDSO for instance? You've edited an existing test for VDSO in x86 to
>    skip the test should this be enabled, but this is not the same as a self
>    test. And obviously doesn't cover arm64.
>
>    This should be relatively strightforward right? You already have code
>    for finding out whether VDSO is msealed, so just use that to see if you
>    skip, then attempt mremap(), mmap() over etc. + assert it fails.
>
>    Ideally these tests would cover all the cases you've changed.
>
It is not as easy.

The config is disabled by default. And I don't know a way to detect
KCONFIG  from selftest itself. Without this, I can't reasonably
determine the test result.