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

On Fri, Nov 04, 2022 at 03:35:51PM -0700, Rick Edgecombe wrote:

From: "Kirill A. Shutemov" <redacted>

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.