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Re: user instruction tracing patch?
On Fri, 2007-11-16 at 16:24 -0500, Frank Ch. Eigler wrote:
> Hi -
>
> On Fri, Nov 16, 2007 at 01:07:47PM -0800, Jim Keniston wrote:
> > [...]
> > Sorry, I still don't get it then. Given
> > probe program("/bin/vi").function("malloc") if (mp) { .. }
> > if some handler executes
> > mp = 1;
> > how does stap know which instance(s) of vi to probe?
>
> None of this exists yet, but it should work similarly to kprobes
> where lack of probe point qualification means "all of them". So
>
> probe program("/bin/vi").function("malloc") { }
>
> would be a request to probe all running (and forseeably, any future)
> copies of vi. To filter further, I imagine additional qualifiers such
> as ".pid(NUM)", ".uid(NUM)". These are all to identify the potential
> probing target processes.
In the above examples, if NUM could be a variable name, then I think
we're in business... especially if it could be a set of pids or uids
(implemented as, or perhaps explicitly, an associative array?). (I can
always dream...)
> The conditional enable/disable stuff is intended to be orthogonal.
> They do not create or destroy probing targets/opportunities, merely
> turn them on or off.
>
> - FChE
Jim