linux-kernel - Re: [RFC PATCH 06/10] x86/entry: add CFI hint undwarf annotations

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Date:   Thu, 1 Jun 2017 09:28:58 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        live-patching@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.cz>, Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC PATCH 06/10] x86/entry: add CFI hint undwarf annotations

On Thu, Jun 01, 2017 at 09:23:58AM -0500, Josh Poimboeuf wrote:
> On Thu, Jun 01, 2017 at 07:03:18AM -0700, Andy Lutomirski wrote:
> > On Wed, May 31, 2017 at 10:44 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > Just to make sure I understand this, if we unwind from...
> > 
> > > @@ -112,6 +114,7 @@ For 32-bit we have the following conventions - kernel is built with
> > >         movq %rdx, 12*8+\offset(%rsp)
> > >         movq %rsi, 13*8+\offset(%rsp)
> > 
> > ...here..., will objtool think that rdx and rsi (etc) still live in
> > their respective regs, or will it find them in the on-stack data given
> > by CFI_REGS?  If the former, how does undwarf deal with the
> > corresponding pops?
> 
> It will find them in their respective registers, which is fine because
> they haven't been clobbered yet.

Sorry, I hit send too soon.  Which pops are you referring to?

-- 
Josh