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Re: Systemtap userspace probing: status and roadmap?


Hi Jim,
   thanks for the reply.

Now the whole situation is more clear to me. I didn't know that
utrace/uprobe wasn't part of mainline kernel, I really look forward
for this to happen.

Is there any linux distro easy to try with that patches included?
Fedora 10? This way systemtap testing would be much easier in a VM,
for example.

Are there any plan to start the inclusion into mainline in the next
kernel releases?

Thanks

2008/11/4 Jim Keniston <jkenisto@us.ibm.com>:
> On Tue, 2008-11-04 at 19:31 +0100, Stefano Doni wrote:
>> Hi guys,
>>     first of all let me thank you for the efforts you give on this
>> wonderful tool! I'm a great fan of this project and of this kind of
>> tools in general, since I have a passion for performance analysis,
>> testing and tuning. I often read that the you are willing to hear some
>> feedback about what user wants, so I thought it would be nice to ask
>> you some question and share some whishes that a user can have about
>> such a good tool.
>>
>> I would like to know what is the current status of Systemtap user
>> space probing and what is the future roadmap (if such a thing exists).
>> For example, man stapprobes in my Ubuntu Intrepid tells me that only
>> "early prototype support" for user space probing is available.
>
> SystemTap does user-space probing the same way it does kernel probing:
> by generating and inserting a kernel module that implements the desired
> implementation.  Just as subsystems like kprobes and markers provide the
> infrastructure for kernel probing, utrace and uprobes provide the
> infrastructure for user-space probing.  A SystemTap script can include
> both kernel and user-space probes.
>
> Utrace-based probes are described under the heading "USER-SPACE" in
> stapprobes(5).  To probe a particular function or statement in a user
> program (i.e., using uprobes), you can do stuff like
>        probe process("/path/to/executable").function("funcname") ...
> You can also probe function returns by adding ".return" to the probe
> specification.
>
> Uprobes depends on utrace.  Neither utrace nor uprobes are in Linus's
> kernel.  Utrace is included with RHEL 5, or you can get a utrace patch
> for your kernel.org kernel at http://people.redhat.com/roland/utrace/ .
> Uprobes is packaged with SystemTap, in runtime/uprobes*/; stap will
> automatically build and insert uprobes.ko if your script uses uprobes
> (but again, you must be running a utrace-enabled kernel).
>
> Our intention is certainly for utrace and uprobes to be accepted
> upstream eventually, but I won't try to predict how/when that will
> happen.  Uprobes in particular is about to undergo some rework.
>
> Stap has been exploiting uprobes for only a few months, and we're still
> shaking out the bugs.  In fact, the 2.6.27-compatible version of uprobes
> was added to SystemTap just this week.  You're welcome to give it a try.
>
> Jim Keniston
> IBM Linux Technology Center
> uprobes maintainer
>
>


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