Re: Time to merge the pgoyette-compat branch

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

Well, there's been a lot of work since the last time I thought I was
ready for the merge.  Most importantly, a MP-safe mechanism was built
to prevent modules from being unloaded while their code was being
executed (or, perhaps, about-to-be-executed).  (A very big Thanks! to
riastradh@ for the suggestion, and for template code.)  Additionally,
all of the compat_netbsd32 machine-dependent code has been split out
from the main compat_netbsd32 module and into the version-specific
modules.

The file src/doc/TODO.compat-branch documents these and other work
done on the branch.

Once again, I'm (just about) ready for the big merge/commit, with just
some last-minute testing.  Any timely and constructive feedback will
be greatly appreciated and welcomed.

Assuming there aren't any show-stopper issues brought up during review,
I'd like to plan to commit in a couple of weeks.

Thanks in advance!




On Fri, 7 Sep 2018, Paul Goyette wrote:

> Folks,
>
> After several months of work, it's now (nearly) time to merge the
> pgoyette-compat branch.  (Yeah, I know that many/most of you don't
> "allow" modules into your environments in the first place, so none
> of this really affects you at all.)
>
>
> This branch includes the following major changes:
>
> * Separation of the single "monolithic" compat module into multiple
>  modules, one for each older version of NetBSD.
>
>  With this, you can load only as much compat code as you want, without
>  having to build a custom compat module.  (You still need a custom
>  kernel to start with, in order not to have all the compat code being
>  built-in.)  Sys-calls that are implemented in the compat module will
>  now load only the necessary compat code, rather than the entire
>  monolithic module.
>
> * Introduction of module "aliases".  In addition to its own name, a
>  module can now provide alias names.  This is useful for the
>  monolithic compat module, which now contains the functionality of
>  the many version-specific modules.  If you load the monolithic module,
>  its aliases will prevent you from also loading individual-version
>  compat modules.
>
> * Elimination of the limit on the number of "required" modules (or
>  "dependencies") for a module.  There was previously a limit of
>  MAXMODDEPS (value 10), with a statically-allocated array;  now the
>  array is dynamically allocated and expanded as needed.
>
> * Extraction of some COMPAT_xx code that was previously intertwined
>  with the main kernel build and not available in non-built-in modules.
>  One example of this is the COMPAT_70 code for rtsock (which bit me
>  when it was introduced, and was the main reason for undertaking the
>  work on this branch).
>
> * Removed linking of the .o kernel compat library into all kernels.
>  This caused problems, since the library included lots of compat
>  symbols, but did not include module linkage; attempts to subsequently
>  load some modules would fail due to multiply-defined symbols.
>
> * Reverting of some previous intentionally-introduced breakage in the
>  sysv_ipc module.  (The breakage was introduced to work-around the
>  above compat library issue.)
>
> Other activity is documented in src/doc/COMPAT-branch-notes file.
>
> There are a number of activities that still need to be worked on;  these
> are also listed in the src/doc/COMPAT-branch-notes file.  None of these
> activites should prevent merging of the branch, as the short-comings are
> already present on the mainline.
>
> I welcome any timely review and constructive feedback.  I'd like to get
> this committed sometime in the next two or three weeks if possible.
>
>
> +------------------+--------------------------+----------------------------+
> | Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:          |
> | (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee dot com   |
> | Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd dot org |
> +------------------+--------------------------+----------------------------+

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