Re: What is a tapset?

[Jim Keniston <jkenisto at us dot ibm dot com>]

On Thu, 2005-07-21 at 13:16, Frank Ch. Eigler wrote:
> Jim Keniston <jkenisto@us.ibm.com> writes:
> 
> > [...]
> 
> (Oops, I meant to credit jkenisto within the list of embedded-C
> inspirations.)

You mentioned "and others," so you're covered. :-)  I can't remember who
first suggested the %{ ... %} idea.

> 
> 
> > [...]
> > > I thought joining the two concepts [aliases & prologues] made some
> > > sense.  If prologues were a separately declared widget without a
> > > distinct name, then the user would not have a marker in the script
> > > source that tells apart the case where a prologue is being pulled
> > > in vs. one where one's not.
> 
> > Since we're trying to be "safe," I assume the author/user of an
> > end-user script will be able to specify which tapset (set of predefined
> > probepoints+prologues) his script refers to.   [...]
> 
> You mean via an explicit "use" or something?  I guess that may be
> possible, but it goes against the philosophy of implicit but
> unambiguous mechanisms.
> 

Let's see what develops.  We can add the explicit-"use" thing if it
turns out to be desirable.

...
> 
> 
> > [...]
> > Not one that anyone has bought into, but we're creative.  I suggested
> > the ability to name handlers some time ago.  [...]
> 
> Interesting ideas.
> 
> > Then a user could refer to that handler as (say)
> > kernel.syscall("read"):trace instead of having to write his own
> > handler to trace that function.
> 
> This is not that different from defining an ordinary (nested) alias:
> 
> alias kernel.syscall("read") = ....
> alias kernel.syscall("read").trace = kernel.syscall("read") { print ... }
> 
> > You might refer to all handlers named "trace"
> > for all system-call entry points as kernel.syscall(*).entry:trace. 
> 
> Depending on wildcard matching mechanisms, this could work with
> the existing alias mechanism:
> 
> probe kernel.syscall("*").trace { /* empty */ }

So this would have the effect of pulling in the predefined trace() code
-- just like any other "prologue" code -- into an otherwise empty
handler?  (Well, in this case, "*" implies pulling a set of predefined
trace() blocks into a corresponding set of handlers.)  Works for me.

> 
> 
> > [...]
> > This syntax could be used in the command line ("Enable the following
> > predefined handlers") on in an .stp file  [...]
> 
> The command line equivalent could be:
> 
> stap -e 'probe kernel.syscall("*").trace {}'
> 
> If such empty probe handler bodies become commonplace, we could
> teach the parser to make the body optional.

That'd be nice.

> 
> 
> - FChE
> 

Looks good to me.

Jim