linux-kernel - Re: [PATCH v4 08/10] x86: BHI stubs

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Message-ID: <202502251031.90B499810@keescook>
Date: Tue, 25 Feb 2025 10:31:26 -0800
From: Kees Cook <kees@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, 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, alexei.starovoitov@...il.com, mhiramat@...nel.org,
	jmill@....edu
Subject: Re: [PATCH v4 08/10] x86: BHI stubs

On Tue, Feb 25, 2025 at 09:52:12AM +0100, Peter Zijlstra wrote:
> On Mon, Feb 24, 2025 at 11:01:02AM -0800, Kees Cook wrote:
> 
> > On Mon, Feb 24, 2025 at 01:37:11PM +0100, Peter Zijlstra wrote:
> > > 
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > 
> > Did this commit log go missing?
> 
> Nah, it never had one.
> 
> How does this sound?
> 
> ---
> 
> Add an array of code thunks, to be called from the FineIBT preamble,
> clobbering the first 'n' argument registers for speculative execution.
> 
> Notably the 0th entry will clobber no argument registers and will never
> be used, it exists so the array can be naturally indexed, while the 7th
> entry will clobber all the 6 argument registers and also RSP in order to
> mess up stack based arguments.
> 

Yes, this reads well. Thanks!

Reviewed-by: Kees Cook <kees@...nel.org>


-- 
Kees Cook