[lttng-dev] Getting function names with lttng-ust-cyg-profile.so

[Matthew Khouzam]

On 13-09-10 03:00 AM, Woegerer, Paul wrote:
> Hi Alexandre,
>
> For trivial examples you can go with 'nm -CS' (or the like), but when
> you start to use liblttng-ust-cyg-profile.so in combination with shared
> objects you will need to record base address information as well (to
> allow you map a virtual memory address at a given point in time to
> offset and path of a shared object (or executable)).
>
> That is one of the reasons why I have submitted:
> http://lists.lttng.org/pipermail/lttng-dev/2013-August/021264.html
This is a very interesting approach, +1 from me on that.
>
> Thanks,
> Paul
>
> On 09/10/2013 01:44 AM, Mathieu Desnoyers wrote:
>> We might want to investigate doing a side-program that gathers the
>> executables on the system, and lookup the symbols from the ELF. We could
>> save those in a bin/ subdirectory of a CTF trace. All we need is
>> instrumentation of the dynamic linker, and to know the executable names
>> associated with PIDs. There is a UST feature request for dynamic linker
>> instrumentation.
>>
>> Thanks,
>>
>> Mathieu
>>
>> * Alexandre Montplaisir (alexmonthy at voxpopuli.im) wrote:
>>> Hi all,
>>>
>>> I've recently started playing with liblttng-ust-cyg-profile.so (aka,
>>> getting UST events from -finstrument-functions), and I have to say it's
>>> pretty nifty! I haven't done any benchmarks, but it's certainly faster
>>> than the typical printf() that people use with it...
>>>
>>> However, in the resulting trace, one only gets the addresses of the
>>> functions. I understand how it's relatively "easy" for the seasoned user
>>> to use nm or addr2line to get the actual function names, but would it
>>> possible - and how hard would it be - to have this information (function
>>> names) directly in the trace?
>>>
>>>
>>> I'm trying to leverage this feature in Eclipse TMF to display a call
>>> stack for such UST traces. And to be honest, displaying a call stack
>>> with only the function addresses is completely useless, we need the
>>> function names.
>>>
>>> We could have the user import a text file (which he can generate with
>>> "nm appname > file.txt" for example). But then he needs the original
>>> binary, which he might not have. And that binary needs to be compiled
>>> with debugging symbols. If the function name information was already in
>>> the trace, it would make the user experience much better, and our job
>>> much easier! ;)
>>>
>>>
>>> Thoughts?
>>>
>>> Thanks,
>>> Alex
>>>
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>