2.11BSD

This is my development fork of 2.11BSD UNIX for the PDP-11. However, this fork is set up with GitHub Workflows so we can test our changes to the kernel.

For more information about 2.11BSD, see https://wfjm.github.io/home/211bsd/

This repo was forked from bsdimp's 2.11BSD repo - thanks to him for making a tidy repo which I can work from.

Current modifications:

• Addition of IBV11-A driver for talking to GPIB devices. (major 27).

Patching

This tree started out at patch level 450, but appeared to have a couple of modifications to one or two files. I ended up merging my IBV11 driver to make it even more of a mess. Since the lowest patch level supported by my 2.11BSD-Action Github Action is 457, the patches were applied in the following way.

1. A branch called patch-base was made from main, at c507710 to create a temporary directory usr with symlinks to src -> ../ and include -> ../include. This allowed patches to be applied from a modern PC.
2. From patch-base, a new branch 451-457 was made which allowed me to apply patches 451 to 457, bringing the Git tree back into alignment with the lowest patch level available of my GitHub action. I was able to push this to GitHub and let the workflow run to verify that everything was compiling correctly.
3. Each individual patch was made in a new branch, taken from the previous, and pushed to GitHub to verify it can be built (i.e. 458 was taken from 451-457, and 459 was taken from 458). In each case, the patch_level variable was also bumped in this repos GitHub workflow to ensure the two trees would be compatible.
4. Once all patches were applied, I created a cleanup branch to remove the temporary directory usr to keep the tree clean.

There were a few patches which caused issues:

• 452 attempts to update the version header of share/lint/llib-lc from 1999-09-09 to 2001-02-22, but the copy in this tree was dated 2001-02-22.
• 459 attempts to update the contents of usr/doc/... which does not exist in this tree - these changes were removed from the patch file.
• 460 seems to break f77 builds, but this is fixed in 462, so I commented out the build for f77 until then.
• 476 was a confusing one. Mounting the file system of a 2.11BSD pl 476 image shows zero changes to sys/mdec/bruboot.s between the patchset applied to this repo and the patchset applied to the image, yet building bruboot.s results warning: unterminated literal errors on line 51, 52 and 100.

  $ curl -o ci.dsk.gz https://asjackson-211bsd-ci.s3.fr-par.scw.cloud/211bsd-ci-476.dsk.gz
  $ gzip -d ci.dsk.gz
  $ mkdir bsd
  $ bsd211fs ci.dsk bsd
  $ diff bsd/usr/src/sys/mdec/bruboot.s git/2.11BSD/sys/mdec/bruboot.s
  $ echo $?    # same if 0
  0
  $ rsync -av ~/git/2.11BSD/ bsd/usr/src/
  $ umount bsd
  $ ./pdp      # my script for booting pdp from ci.dsk
  ...
     # cd /usr/src/sys/mdec
     # make clean
     # make
     ...
     # [ $? -eq 0 ] && echo works on my local machine
     works on my local machine
  

  Eventually I realised mistake - like with 459, I had to remove the changes to use/doc/... but while doing so, accidentally removed the changeset to the Makefile for mdec. I'm leaving this in here to document my stupidity while applying these patches :-)

Related Stuff

I have also been working on the following related stuff:

• 2.11BSD-Distribution-Builder to produce installation / distribution files for the same set of patch levels.
• 2.11BSD-Action which allows GitHub workflows to perform testing against a 2.11BSD simulated PDP-11 - this also performs builds of all patch levels and provides .img files for each
• bnlisp A small lisp written in K&R C for 2.11BSD, dedicated to my friend bnl, written with lots of help from stylewarning