linux-kernel - Re: [RFC PATCH v1.9 07/14] x86/stacktrace: add function for detecting reliable stack traces

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Message-ID: <20160613215855.66xvswctxdy2bbrj@treble>
Date:	Mon, 13 Jun 2016 16:58:55 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Miroslav Benes <mbenes@...e.cz>, Jiri Kosina <jikos@...nel.org>,
	Jessica Yu <jeyu@...hat.com>, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org, Vojtech Pavlik <vojtech@...e.com>
Subject: Re: [RFC PATCH v1.9 07/14] x86/stacktrace: add function for
 detecting reliable stack traces

On Thu, Jun 09, 2016 at 10:31:01AM +0200, Jiri Slaby wrote:
> On 04/12/2016, 05:56 PM, Josh Poimboeuf wrote:
> >> We had been using unwinder for over a decade in SUSE but it stopped
> >> working for assembly recently (for obvious reasons). So having a working
> >> and reliable unwinder again is one of the top priorities for us.
> > 
> > Since you already have an unwinder in SUSE, it sounds like what you need
> > most urgently is DWARF generation support in objtool so that your
> > unwinder will work again for asm code, right?  The kernel already emits
> > DWARF today (for C code), so an upstream unwinder isn't needed first.
> 
> Right, that's exact.
> 
> > That's high on my TODO list, and the coding is probably 70-80% done.  I
> > don't want to hold up progress...  But I don't really feel comfortable
> > passing the code off because it's quite a big feature with some major
> > changes to objtool.  Being the objtool author, I want to make sure to
> > give it my full attention.
> 
> Sure. There is going to be no pressure to merge the v1 of the changes.
> But it would be nice to see what you have now so that we can start
> reviewing and proposing patches on the top of what you have :).

The code is still quite a mess and doesn't even work yet.  I think it
would be counterproductive for everybody if I were to share it at this
stage.

> > I'm spread quite thin at the moment but I do hope to have v1 of those
> > patches soon, hopefully May-ish.
> 
> So I hope we will see something we can start working on now. I can
> really dedicate one-man hours to that work.

I do appreciate your offer to help.  Hopefully soon I'll get it to at
least a decently working and halfway readable state, and then I'll post
it.  Then any help will be much appreciated.

-- 
Josh