Subject: Re: foo_init()s in main() [was: CVS commit: src/sys]
To: None <tech-kern@NetBSD.org>
From: Terry Moore <firstname.lastname@example.org>
Date: 11/22/2005 17:30:16
I worked with an embedded operating system some years ago that did
There was a "module configuration" file which listed
prerequisites. Modules could be requested by name or by "tag", and
modules could claim to satisfy a requirement (allowing things to be
Then each module that wanted initialization services had a macro that
specified an init function (by name). The name got mangled in a
recognizable way and put into the symbol table. The build process
would link twice, once to get the symbols (ld -r or equiv), scan to
find the magic symbols, and use the module topological sort to build
an init vector.
This seemed better than implicit initialization, because there are
subtle problems with cycles in the initialization graph, which are
more readily resolved by an engineer than by a machine.
Anyway, the result was a system without a main() function, which made
updates and modular additions really easy. LKM-like things were
faked by calling the INIT-entry point (of course the things you
depended on had to be in the kernel, and it was your job to make sure
of that; this was in the late 80s).
So I can recommend this approach, for whatever it's worth.
At 05:20 PM 11/22/2005 -0500, Steven M. Bellovin wrote:
>In message <20051122215324.GB24186@netbsd.org>, Bill Studenmund writes:
> >How do you think we should encode dependencies? I agree that the FreeBSD
> >way is uncentralized. However someone who studies the whole system can
> >tune it so that things get loaded in the right order (just pick the right
> >set of "FIRST", "SECOND", and so on). How would we do that w/o the master
> >list of values?
>Thinking out loud -- something like rc.d uses?
> --Steven M. Bellovin, http://www.cs.columbia.edu/~smb