linux-kernel - Re: CET shadow stack app compatibility

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Date:   Tue, 15 Nov 2022 19:45:03 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc:     "Torvalds, Linus" <torvalds@...ux-foundation.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: CET shadow stack app compatibility

On Tue, Nov 15, 2022 at 05:04:40PM +0000, Edgecombe, Rick P wrote:
> > ELF bits should not, must not, be called CET. API, not CET, Compiler
> > features, also not CET.
> 
> So the arch_prctl()s can't be shared between shadow stack and IBT? They
> don't have to be, but this is a new thing after a fair amount of
> earlier discussion.

I would very strongly suggest IBT not use that interface and instead we
follow ARM64 BTI's lead -- such that application developers don't go
insane trying to use two nearly identical solutions.

I mean, the toolchain folks made a godawefull mess of things, but we
don't have to.