Re: [DynInst_API:] Stackwalking in a mutatee

[Marc Brünink <marc@xxxxxxxxxx>]

Thanks for your fast reply!

I tried to use setInstrStackFrames before and it did not work. I just tried again to make sure I did not do a stupid mistake. Still does not work. 

I can get a backtrace of the instrumentation. I succeed in getting a nice backtrace of all instrumentation functions. However, I fail to get a backtrace of the actual application. It stops somewhere in DYNINSTstaticHeap. I get something like

	my_super_instrumentation_function_1
	my_super_instrumentation_function_2
	DYNINSTstaticHeap_16M_anyHeap_...

I understand why this happens. However, I am still searching for a nice and clean solution.

I will continue to try a couple of things. Especially, I want to try to walk the stack starting at the frame which was active before I called any of the instrumentation functions. This would be good enough. Not sure whether it will work though.

In the meantime I am more than grateful for any other ideas.


Marc


On Aug 29, 2013, at 1:00 AM, Matthew LeGendre wrote:

> 
> It's been several years since I tried doing 1st-party stackwalks from an 
> instrumented mutatee and things may have changed.  But the last time I did 
> this you could add a call to
> 
>   BPatch::setInstrStackFrames(true);
> 
> before you insert instrumentation.  This would cause Dyninst to generate 
> stack frames around generated instrumentation.  That adds runtime 
> overhead, but also gives a stack walker sufficient information to walk out 
> of the instrumentation.
> 
> 
> I believe there's also efforts underway to have Dyninst start updating 
> existing DWARF stack unwinding information as it instruments and relocates 
> code.  But I'm not sure where those efforts stand or when they'd appear in 
> a released Dyninst.  Someone from the Dyninst team would have to comment.
> 
> -Matt
> 
> On Wed, 28 Aug 2013, Marc Brünink wrote:
>> Dear all,
>> 
>> short version:
>> What is the appropriate way to walk the stack in a mutatee?
>> 
>> long version:
>> StackwalkerAPI implements basic stack walking. Some code in Dyninst 
>> implements the additional tweaks necessary to handle the complexity added by 
>> instrumentation. Thus, we can still perform a third party stackwalk of 
>> instrumented code.
>> 
>> But how do I perform a first party stackwalk in the mutatee? The problem is 
>> that only the mutator knows about all this additional Dyninst features, e.g. 
>> which code got relocated, etc.
>> 
>> I suppose this is a very common problem. However, at the moment I fail to 
>> find a nice, clean, and easy way to walk the stack in the mutatee.
>> Before I dive into this in more detail, let me ask a simple question:
>> 
>> Is there an obvious way to walk the stack in the mutatee which I just don't 
>> know about? Or do I have to manually make sure the FrameSteppers etc. in my 
>> mutatee are up-to-date?
>> 
>> Marc
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