rprobes + Function return probes status

[Frank Ch. Eigler]

Rick Salmon Vishwanath <maveriickk@yahoo.com> writes:

> [...]  I am basically looking for a maechanism that would let me log
> the arguments of a function call(jprobes-like) and the return value
> of the function(kretprobes-like) simultaneously. [...]

Currently, this requires two separate probes, with the first
triggering near function entry to save incoming parameters, and the
second triggering upon function return.  This can be done now with
some combination of jprobes & kretprobes, if that is your kind of
poison, or alternately in systemtap script.  In each case, the tricky
part is saving the incoming parameters, then finding them again, while
dodging obstacles like recursion and concurrency.  This part has to be
done manually right now.

The systemtap translator is planned to support performing the
save/restore automagically (bug #1382), so that a single specially
marked "return" probe would have transparent access to the saved
copies of parameters.

- FChE