dtrace vs module unloading

[Andriy Gapon]

It seems that FreeBSD DTrace currently does not track module loading / unloading
at all.  dtrace_module_loaded/dtrace_module_unloaded are both under ifdef sun.

I think that this is a root cause of e.g. fbt probes for some functions
remaining after a module that provides the functions is unloaded.

It looks like currently we do not post any event when a module gets loaded /
unloaded.  Perhaps this is one of the factors in current situation.
OTOH, in Solaris they just have some dtrace hooks in the form of function
pointers directly in the module handling code (equivalent of our kern_linker).

-- 
Andriy Gapon