Re: Move kern_ctf to the dtrace module?

[Paul Goyette <paul%whooppee.com@localhost>]

It was suggested to me in private Email that perhaps the file 
sys/kern/kern_ctf.c should be moved out of src/sys and into "the 
module's [source] directory."

I'd rather not move the file into src/external/..../dtrace/dev/fbt/ 
because kern_ctf.c and the existing file both include some headers with 
the same name, but expecting different files to be included!  (dtrace 
provides its own versions of sys/kobj.h and sys/kobj_impl.h headers.)

We generally don't put actual source files into src/sys/modules/* but it 
might be appropriate in this case.

Either way, I'm not really happy about using file-specific CPP_FLAGS in 
sys/modules/dtrace/fbt/Makefile but the only other way to make this work 
would be to create a dtrace_fbt_ctf module, on which dtrace_fbt would 
depend.  This introduces an additional layer of module-autoload, and 
would occupy a slightly larger in-memory footprint, but should not have 
any other impact.

So, questions to be answered:

* Where should sys/kern/kern_ctf.c reside?
* Should kern_ctf.c be a separate (sub)module?

Any thoughts?

On Tue, 13 Sep 2016, Paul Goyette wrote:

> On Mon, 12 Sep 2016, Paul Goyette wrote:
>
> > Currently, if you include KDTRACE_HOOKS in your kernel, we automatically 
> > include src/sys/kern/kern_ctf.[co] in the resulting kernel.
> >
> > kern_ctf defines only one global symbol, mod_ctf_get(), according to the 
> > generated netbsd.map file, and there are no references anywhere else in the 
> > kernel to this routine;  the only reference is within the sub-module 
> > dtrace_fbt.kmod
> >
> > I would like to suggest that kern_ctf be removed from the kernel, and added 
> > to the dtrace_fbt module.  And, since kern_ctf references stuff in 
> > net/zlib.c, the dtrace_fbt module should depend on zlib module.  And 
> > finally, the ktrace_hooks dependency can be removed from the zlib.c line in 
> > net/files.net
> >
> > The bottom line is that zlib code won't be included in kernels that don't 
> > need it, yet will still be available when using dtrace (which is only 
> > available as a module).
> >
> >
> > If I don't see any significant objections, I'll post diffs in a day or so 
> > before making any commits.
>
> Diffs are attached here.
>
> I plan to commit within the next couple of days...
>
>
>
> +------------------+--------------------------+------------------------+
> | Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
> | (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
> | Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
> +------------------+--------------------------+------------------------+

+------------------+--------------------------+------------------------+
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
+------------------+--------------------------+------------------------+