linux-kernel - Re: [RFC][PATCH 3/3] x86/entry, ORC: Teach objtool/unwind

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Date:   Fri, 8 May 2020 12:12:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, luto@...nel.org
Subject: Re: [RFC][PATCH 3/3] x86/entry, ORC: Teach objtool/unwind_orc about
 stack irq swizzles

On Thu, May 07, 2020 at 11:24:49PM +0200, Thomas Gleixner wrote:
> But over our IRC conversation I came up with a 3rd variant:
> 
>   For most of the vectors the indirect call overhead is just noise, so
>   we can run them through the ASM switcher, but for the resched IPI
>   we can just use a separate direct call stub in ASM.

Are we sure the rat-poison crap is noise for all the other system
vectors? I suppose it is for most since they'll do indirect calls
themselves anyway, right?

> I can live with that. I might have to pay up for Peter's headaches to
> teach objtool, but that's a different story. Let me check how many beers
> he owes me first ...

We're going to be so massively drunk if we ever settle that :-) For now
I'll just have to live with knowing more about the unwinders.