linux-kernel - Re: [PATCH v4 1/4] x86/ibt: factor out cfi and fineibt offset

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Message-ID: <6F9EF5C3-4CAE-4C5E-B70E-F73462AC7CA0@zytor.com>
Date: Tue, 04 Mar 2025 06:52:53 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Peter Zijlstra <peterz@...radead.org>,
        Menglong Dong <menglong8.dong@...il.com>
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Subject: Re: [PATCH v4 1/4] x86/ibt: factor out cfi and fineibt offset

On March 4, 2025 1:42:20 AM PST, Peter Zijlstra <peterz@...radead.org> wrote:
>On Tue, Mar 04, 2025 at 03:47:45PM +0800, Menglong Dong wrote:
>> We don't have to select FUNCTION_ALIGNMENT_32B, so the
>> worst case is to increase ~2.2%.
>> 
>> What do you think?
>
>Well, since I don't understand what you need this for at all, I'm firmly
>on the side of not doing this.
>
>What actual problem is being solved with this meta data nonsense? Why is
>it worth blowing up our I$ footprint over.
>
>Also note, that if you're going to be explaining this, start from
>scratch, as I have absolutely 0 clues about BPF and such.

I would appreciate such information as well. The idea seems dubious on the surface.