RE: pre-compiled modules

[David Smith <dsmith@redhat.com>]

Thanks for the response.  See stuff below.

On Tue, 2006-06-27 at 12:47 -0700, Stone, Joshua I wrote:
> On Tuesday, June 27, 2006 11:52 AM, David Smith wrote:
> >> Blatant modversions mismatches will be detected during the actual
> >> insertion attempt - IMO there is no need to make a dry run first.  We
> >> will need more self-protective code though for purposes of verifying
> >> module addresses.  Specifically, we need to find a kernel API routine
> >> that, given a module name, gives its loaded base address.
> > 
> > Hmm, I hadn't considered that.  Will this code go in the module itself
> > or go in the runtime?
> 
> Is there a difference?  The runtime is still compiled into the module,
> right?

Sorry, I meant to say: "Will this code go in the module itself or the
stpd daemon?"

> > To help move this along a bit, I've attached a patch that modifies the
> > systemtap front end to take 2 new options:
> > 
> >    -S         Save the compiled module in the current directory
> 
> I would prefer to see an option to specify the directory, instead of
> assuming $PWD.  You could always use '-S .', but some people might want
> to drop it somewhere else.  Another possibility instead of -S is to just
> extend the -m option to allow a path.

That's easy enough to add, but it seems like that 99% of the time I'd
want it to go in the current directory.

Anyone else got any opinions?

> >    -P PRE_COMPILED_MODULE
> >               Run pre-compiled module
> 
> Looks fine.
> 
> Have you thought about concurrent access to a precompiled module?  If
> you have a systemtap module foo.ko on a multi-user system, you might end
> up with a situation where multiple people want to run it at the same
> time.  Of course you can only insmod one at a time, if nothing else
> because of the naming issue.  

Hmm, no I hadn't considered that.  We've also got a similar but
different problem.  What happens when 2 users both compile two different
scripts called 'foo.stp' into 'foo.ko', then try to run them
concurrently?

I'm unsure of what we can do in either case.

-- 
David Smith
dsmith@redhat.com
Red Hat, Inc.
http://www.redhat.com
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