linux-kernel - Re: [PATCH v3 00/10] x86/ibt: FineIBT-BHI

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Message-ID: <20250220112710.GK34567@noisy.programming.kicks-ass.net>
Date: Thu, 20 Feb 2025 12:27:10 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, alyssa.milburn@...el.com,
	scott.d.constable@...el.com, joao@...rdrivepizza.com,
	andrew.cooper3@...rix.com, jpoimboe@...nel.org,
	jose.marchesi@...cle.com, hjl.tools@...il.com,
	ndesaulniers@...gle.com, samitolvanen@...gle.com, nathan@...nel.org,
	ojeda@...nel.org, kees@...nel.org, alexei.starovoitov@...il.com,
	mhiramat@...nel.org, jmill@....edu
Subject: Re: [PATCH v3 00/10] x86/ibt: FineIBT-BHI

On Wed, Feb 19, 2025 at 05:21:07PM +0100, Peter Zijlstra wrote:
> Hi all!
> 
> Having landed much of the previous series in tip/x86/core, I was hoping for an
> easy time landing the final two patches.. alas.
> 
> This whole FineIBT SYSCALL pivot thing showed up, which got me to develop the
> paranoid FineIBT variant. And because testing I added a cfi=warn knob, and then
> I migrated bhi to an option etc..
> 
> Then just as I was to post this stuff, Scott out-nerds me with a whole new
> instruction sequence. Which got me to rework the entire pile once again, and
> it is now another 10 patches again :/
> 
> Anyway, be warned, Scott loves overlapping instructions.
> 
> This is tested with:
> 
>   cfi=fineibt,warn
>   cfi=fineibt,warn,paranoid
>   cfi=fineibt,warn,bhi
>   cfi=fineibt,warn,paranoid,bhi
>   cfi=fineibt,paranoid,bhi
> 
> Also note that LKDTM's CFI_FORWARD_PROTO test will do a double splat for
> paranoid in warn/permissive mode, since both the caller and callee hash check
> will fail.
> 
> Also available at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/fineibt-bhi2

I've updated this tree with the latest version of the patches.

Notably, Kees, I've not taken your Reviewed-by tag for patches that saw
significant rework -- even when in response to your own feedback :)

(ud_type propagation is now gone)

I'll repost in a few days, to give people a chance to catch up.