linux-kernel - Re: [RFC][PATCH 6/6] objtool: Add IBT validation / fixups

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Message-ID: <20220209114519.GA65516@worktop.programming.kicks-ass.net>
Date:   Wed, 9 Feb 2022 12:45:19 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        joao@...rdrivepizza.com, hjl.tools@...il.com,
        andrew.cooper3@...rix.com, linux-kernel@...r.kernel.org,
        ndesaulniers@...gle.com, samitolvanen@...gle.com
Subject: Re: [RFC][PATCH 6/6] objtool: Add IBT validation / fixups

On Wed, Feb 09, 2022 at 12:41:41PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 08, 2022 at 03:43:27PM -0800, Kees Cook wrote:

> > Why have the kernel do that work at every boot when it can be known at
> > link time?
> 
> I have patches that write a 4 byte #UD there instead of a nop. That
> would make !IBT hardware splat as well when it hits a sealed function
> (and in that case actually having those extra ENDBR generated is a
> bonus).
> 
> Anyway, I have some newer patches and some hardware, except it's a NUC
> and working with those things is a royal pain in the arse since they
> don't have serial. I finally did get XHCI debug port working, but
> there's no XDBC grub support, so now I managed to boot a dead kernel and
> the thing is a brick until I can be arsed to connect a keybaord and
> screen to it again :-(
> 
> KVM/qemu has no IBT support merged yet, so I can't use that either.

FWIW, those patches live here:

  git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/wip.ibt