Re: Random ideas about systemtap dependencies

[Roland McGrath <roland at redhat dot com>]

A general answer is that systemtap is intended to have many flavors of
probes, with the level of things like kprobes being an implementation
detail used by some probes.  The present prevalence of kprobes in the
implementation of systemtap probes will not necessarily always be the case.

Specifically, are you talking about compiling with -pg?  I can see making
that work with a special-purpose mcount (a little per-machine work there)
that looks up PC locations in a table of probeable spots.  I think the work
required in integrating that with the translator is mainly in getting all
the exact PC locations that mcount will be looking up.  From the kernel
build one needs to glean this static list of potential probe sites, and
then jigger the translator to resolve each "entry" probe to the correct
statically chosen PC for the named function.  With that, the existing
machinery for things like target variable access should do fine working
from the correct PC.  Of course, only function entry probes can be
supported this way.

So in short, it's doable and fits fine into the larger scheme of things.
There is a fair bit of work you'd have to do, but it doesn't inherently
clash with what we're doing.


Thanks,
Roland