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Date: Sun, 9 Feb 2020 17:43:40 -0800
From: Kees Cook <>
To: Peter Zijlstra <>
Cc: Andy Lutomirski <>,
	Kristen Carlson Accardi <>,,,,,,,,,
Subject: Re: [RFC PATCH 06/11] x86: make sure _etext includes function

On Fri, Feb 07, 2020 at 10:24:23AM +0100, Peter Zijlstra wrote:
> On Thu, Feb 06, 2020 at 12:02:36PM -0800, Andy Lutomirski wrote:
> > Also, in the shiny new era of
> > Intel-CPUs-can’t-handle-Jcc-spanning-a-cacheline, function alignment
> > may actually matter.
> *groan*, indeed. I just went and looked that up. I missed this one in
> all the other fuss :/
> So per:
> the toolchain mitigations only work if the offset in the ifetch window
> (32 bytes) is preserved. Which seems to suggest we ought to align all
> functions to 32byte before randomizing it, otherwise we're almost
> guaranteed to change this offset by the act of randomizing.

Wheee! This sounds like in needs to be fixed generally, yes? (And I see
"FUNCTION_ALIGN" macro is currently 16 bytes...

Kees Cook

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