I don't have any binary images, you'll have to build them (cross-compiled
from Linux). Side note: the "Pi on Fire" demo is a version of vmwOS and
binaries of that exist if you really want to try w/o building your own.
To run it you'll need to build "kernel.img" or "kernel7.img" and copy
the file over that file under /boot on a pre-existing Raspbian image.
Supported Features
Multi-tasking
Multi-core (partial)
Blocking-I/O
Memory protection (kernel/user)
ANSI art capable framebuffer
Full VFS filesystem layer with read/write
Abstraction layers for character and block devices
Executables:
Runs ARM -fPIC bFLT executables (cross-compiled from Linux).
Link against included "vlibc" C library.
bFLT generated using my own custom elf2bflt
that can be found in the github repository.
Filesystems:
romfs running on top of ramdisk.
dos33fs (1980s Apple II filesystem)
Software
Minimal shell
Minimal kilo-based editor with nano keybindings
Various other utilities (cp, rm, md5sum, truncate, cat, ls, ...)
Demoscene Demo
Pi On Fire which won 2nd
place at Demosplash 2019.
Documentation
There isn't much. If you are interested in some more details on the
implementation and future plans you can check out our paper about
this at MEMSYS'18.
"A Raspberry Pi Operating System for Exploring Advanced Memory System Concepts"
Was working on stdin/stdout redirection (and the dup2() syscall).
To get cat to work I have to implemented ICANON cannonical term support,
which is an amazing piece of unnecessarily complicated backwards compatability.
Midway through this I reached feature-parity with the Unixes of my youth,
as suddenly backspace wasn't working.
21 February 2020
Version 0.20 was finally released!
The VFS (virtual filesystem layer) is more or less complete.
There is full abstraction of the filesystem layer, with two
filesystems currently supported: romfs (read-only) and
the Apple II DOS3.3 filesystem with full write support.
In addition, proper block and character device support was added.
Currently ramdisk is the only block device and the console the only
character device, but the infrastructure is there for more. You can
open raw block devices, and you can use fcntl() to make stdin
non-blocking for games.
During this development a lot of utilities were added, and many fixes
were made to userspace programs and vlibc.
You can see a video demoing the new functionality here (sorry for the
weird timing in the video, vokoscreen and kdenlive don't work well together
and I don't have time to go back and re-do the video).
25 January 2020
Spent the week adding a VFS abstraction layer (virtual filesystem)
with the goal of allowing modular file system support. Major re-write
of file handling, fixing some bugs along the way. Will make things easier,
but the 6502 coder in me hates taking a block_read() call and replacing it
with something like file->inode->sb->block.ops->read().
15 January 2020
Fixed some more bugs with editor which were primarily in vlibc.
Including one really bad memmove() issue that is probably the reason
the framebuffer console was so unstable.
The memory corruption bug was indeed due to the bss being corrupted
(the relocations were accidentally being written there).
14 January 2020
Working on getting a simple editor going.
Used the kilo-based example
here.
This led to fixing up vlibc (fixing various bugs [mostly in printf],
but also adding bare-bones malloc() support.
Also the syntax-highlighting had complex enough C that gcc kept generating
relocated variables, so this led to getting relocation of bFLT variables
at load-time going.
That all mostly seems to work, but now the editor is crashing again
for reasons that seem unrelated. The heap and/or bss is getting
corrupted somehow and it's trying to dereference a string.
9 November 2019
The Pi On Fire Demo using VMWos won 2nd place
in the modern demo competition at Demosplash.
30 October 2019
Work on a demoscene demo that will run on vmwos! Because of this some
changes have been made. Full background
44.1kHz/16-bit audio playing is now supported via DMA.
There is now a syscall to sync a framebuffer (so graphics can be done
from userspace).
Also floating point is now enabled by the kernel (though userspace by
default doesn't use it).
6 October 2018
A paper about vmwOS won the "Chair's Choice" award at the MEMSYS'18 conference.
You can read the paper here.
15 May 2018
When trying to debug a student project ended up adding minimal PWM audio
support. For now all it does is beep (though you can use control-G
to make the beep happen).
This was a pain, as the PWM interface is not documented well.
12 April 2018
Work in progress on multicore support. It actually can start all four
CPUs, but I don't have locks in the console so the output gets all run
together.
6 April 2018
Have framebuffer support mostly working again (though still slow).
Amazingly works on pi3, despite the fact I can't get the temperature/mailbox
to work still.
27 March 2018
Pi-3B+ support added.
25 March 2018
Have MMU memory protection (kernel vs user) finally working, at least on
Pi3. Having issues with enabling cache on the Pi3 though.
23 March 2018
Have bflt binary support finally working.
7 March 2018
Code should now work on both Pi2 and Pi3 models now. You might need
recent firmware on all models, as it assumes a 48MHz UART clock now.
A huge host of changes had to be made to get it to run on the newer machines
and firmware. The biggest was writing a device-tree parser.
There was also a really tricky to debug issue where the aplus DRAM was
initializing to zero but the pi3 was initializing to 555555 and some
code was accidentally being setup properly due to this.
20 May 2016
Finally have blocking I/O working! Look at this sysinfo update,
notice that the system is spending most of its time in the idle thread.
This is because console_read() and sleep() both block, putting processes
to sleep and the idle thread finally gets to run.
Here's a before shot showing that it didn't idle previously.
Also note that we leak memory and processes (i.e. processes aren't
freed after an exit() ). Need to fix that.
17 May 2016
Finally implemented enough syscalls (and subdirectory support) that
ll now runs under my OS. Had to manually
generate PIC assembly code, which wasn't fun.
13 May 2016
Demo of the 0.13 release in action:
Relive the 1990s: the framebuffer console has been extensively tested
and supports enough ANSI control characters to display
most BBS ANSI art.
April 2015
Version 0.10 showing classic AB multitasking support:
An EeePC acting as a terminal for a Raspberry Pi Model A+
running VMWos:
The local royalty was unimpressed by the A/B multitasking demo:
Performance Numbers
Some results when trying to get maximum memset() performance.
Raspberry Pi A+/B BCM2835 700MHz LPDDR2 RAM
Each test is 16 repetitions of a 1MB memset()
1-byte is just a simple loop, one byte at a time.
4-byte is a simple loop, writing an int at a time.
64-byte uses the arm "stm" instruction to write 64B at a time.
