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

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Date:   Thu, 1 Dec 2016 21:28:37 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
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 06/13/2016, 11:58 PM, Josh Poimboeuf wrote:
> 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.

This has beaten us for way too long, so we are at the state we want to
have the DWARF generation for asm in a very close future. So may I ask
you again to send me what you have now? If not, I will start working on
it from scratch to have something rather soon :).

thanks,
-- 
js
suse labs