linux-kernel - Re: [PATCH 4/7] objtool: Add support for return trampoline call

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Date:   Sat, 4 Apr 2020 09:22:32 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Julien Thierry <jthierry@...hat.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH 4/7] objtool: Add support for return trampoline call

On Sat, Apr 04, 2020 at 03:32:18PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 03, 2020 at 05:46:20PM +0200, Peter Zijlstra wrote:
> > On Fri, Apr 03, 2020 at 10:17:57AM -0500, Josh Poimboeuf wrote:
> > > Peter, I think my previous idea for UNWIND_HINT_ADJUST stack_add=8 would
> > > work here?
> > 
> > Yes, it would.
> 
> Sorry, I have reconsidered. While it will shut up objtool, it will not
> 'work'. That is, the ORC data generated will not correctly unwind.
> 
> I'll try and write a longer email tonight.

Right, that's what I've been trying to say.  The ORC data will be
non-deterministic unless we unroll the loop.  Or did you mean something
else?

-- 
Josh