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Message-ID: <19911588-f74d-4a7a-858c-2994c8614463@sirena.org.uk>
Date: Tue, 18 Jul 2023 20:10:35 +0100
From: Mark Brown <broonie@...nel.org>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH 02/35] prctl: Add flag for shadow stack writeability and
push/pop
On Tue, Jul 18, 2023 at 05:47:32PM +0000, Edgecombe, Rick P wrote:
> On Sun, 2023-07-16 at 22:50 +0100, Mark Brown wrote:
> > On arm64 the kernel can separately control if userspace is able to
> > pop
> > and push values directly onto the shadow stack via GCS push and pop
> > instructions, supporting many scenarios where userspace needs to
> > write
> > to the stack with less security exposure than full write access. Add
> > a
> > flag to allow this to be selected when changing the shadow stack
> > status.
> Is this correct? I thought Szabolcs was saying pop was always
> supported, but push was optional.
It's not, I wrote this right after looking at hypervisor controls which
do control push and pop.
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