FuzixOS: Because Small Is Beautiful

This is the initial public tree for the FuzixOS project. It is not yet useful although you can build and boot it and run test application code. A lot of work is needed on the utilities and libraries yet.

FUZIX

FUZIX is a fusion of various elements from the assorted UZI forks and branches beaten together into some kind of semi-coherent platform and then extended from V7 to somewhere in the SYS3 to SYS5.x world with bits of POSIX thrown in for good measure. Various learnings and tricks from ELKS and from OMU also got blended in

What does FUZIX have over UZI

Support for multiple processes in banked memory (as per UZI180) but with Minix style chmem and efficient use of bank allocations.
Support for multiple processes via hard disk or non mappable RAM drive switching (as per UZI, UZIX).
The ability to run single tasking on small devices, for bring up and for standalone tool execution
Support for "real" swapping combined with banked memory.
Proper sane off_t and lseek
Normal dev_t
30 character filenames
Proper sane time_t
System 5 signals (half baked)
Posix termios (does all the original UZI tty did but much can be added)
Blocking on carrier for terminals
Optimisations to avoid bogus uarea copying compared to UZI180
More modern system call API: 3 argument open, mkdir, rmdir, rename, chroot (with correct .. semantics), fchdir, fchmod, fchown, fstat, fcntl, setpgrp, sighold and friends, waitpid, setpgrp, nice O_NDELAY, O_CLOEXEC, F_SETFL, F_DUPFD etc
Address validation checks on all syscall copies
Builds with a modern ANSI C compiler (SDCC)
Core code can be built for 6809 and 6502 so should be far more portable
Core architecture designed to support building and maintaining multiple target machines without forking each one
Helpers to make many bits of implementation wrappers to core code
Lots more bugs right now

What does UZI have over FUZIX

Can run in 64K of RAM (32K kernel/32K user). FUZIX would need banked ROM or similar to pull this off.

What do the UZI branches have that FUZIX has not yet integrated

Minimal TCP/IP (UZIX 2.0). Unfortunately the original TCP was never released openly.
Symbolic links (UZIX)
Various clever fusions of syscalls that may save a few bytes (UZIX)
setprio (UZIX)
Rather crude loadable drivers (UZIX)
Use of __naked and __asm for Z80 specific bits to avoid more .S files than are needed (UMZIX)

Plus OMU has a really clever function passing trick for open/creat and friends, while UMZIX has a neat unified "make anything" function.

What Key Features Are Missing Still

ptrace, core dumps, ulimit
root reserved disk blocks
banked executables
TCP/IP
select/poll()
Z180 banking support
/dev/tty alias
Support for > 32MB filesystems (but first figure out how to fsck a giant fs on a slow 8bit micro!)
Uptime
Smarter scheduler
Optimisations for disk block/inode allocator (2.11BSD)
CP/M emulator has not yet been ported to FUZIX syscall API

Tool Issues

No useful 8086 compiler option (started work on pcc 8086 but help needed)
6809 gcc and cc65 don't have long long 64bit (for sane time_t)
SDCC has long long bugs and gaps
SDCC can generate ROMmable binaries but not banked ones
SDCC has no register passing function call support, and for some stuff it really shows
SDCC generates quite bloaty small applications. Needs research on how to improve.
None of the above have an O88 style common sequence compressor

Platforms

Z80Pack - used as a dev and test environment for both large swapping mulitprocess and for small single tasking
Amstrad NC100 - real hardware sanity check

Various other platforms are partly filled out to sanity check assumptions and start making progress on them. The main need there is now to tackle all the billion different ways of interfacing the floppy controllers.