Re: [PATCH v3 24/37] x86: Introduce userspace API for CET enabling

[Peter Zijlstra]

On Fri, Nov 04, 2022 at 03:35:51PM -0700, Rick Edgecombe wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> 
> Add three new arch_prctl() handles:
> 
>  - ARCH_CET_ENABLE/DISABLE enables or disables the specified
>    feature. Returns 0 on success or an error.
> 
>  - ARCH_CET_LOCK prevents future disabling or enabling of the
>    specified feature. Returns 0 on success or an error
> 
> The features are handled per-thread and inherited over fork(2)/clone(2),
> but reset on exec().
> 
> This is preparation patch. It does not implement any features.

Urgh... so much for sharing with other architectures I suppose :/

The ARM64 BTI thing is very similar to IBT (except I think their
approach to the legacy bitmap is much saner).

Given that IBT isn't supported and needs the whole legacy bitmap mess,
do we really want to call this CET ? Why not just make a Shadow Stack
API and tackle IBT independently.