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105
README.md
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@ -2,8 +2,8 @@
*Bootstrap post-collapse technology*
Collapse OS is a collection of programs, tools and documentation that allows
you to assemble an OS that can:
Collapse OS is a z80 kernel and a collection of programs, tools and
documentation that allows you to assemble an OS that can:
1. Run on an extremely minimal and improvised architecture.
2. Communicate through a improvised serial interface linked to some kind of
@ -20,7 +20,23 @@ manage to build and install Collapse OS without external resources (i.e.
internet) on a machine of her design, built from scavenged parts with low-tech
tools.
See the "Goals" section below for details.
## Status
The project is progressing well! Highlights:
* Has a shell that can poke memory, I/O, call arbitrary code from memory.
* Can "upload" code from serial link into memory and execute it.
* Can manage multiple "block devices"
* Can read SD cards as block devices
* A z80 assembler, written in z80 that is self-assembling and can assemble the
whole project. 4K binary, uses less than 16K of memory to assemble the kernel
or itself.
* Extremely flexible: Kernel parts are written as loosely knit modules that
are bound through glue code. This makes the kernel adaptable to many unforseen
situations.
* A typical kernel binary of less than 2K (but size vary wildly depending on
parts you include).
* Built with minimal tooling: only [libz80][libz80] is needed
## Why?
@ -78,26 +94,6 @@ enough to steadily improve your technological situation, build more
sophisticated machines from more sophisticated scavenged parts and, who knows,
in a couple of decades, build a new IC fab (or bring an old one back to life).
## Status
The project is progressing well and I already have a working shell (see `doc`
to see what it can do) on a classic RC2014. Highlights:
* Extremely flexible: Kernel parts are written as loosely knit modules that
are bound through glue code. This makes the kernel adaptable to many unforseen
situations.
* 2K binary (but size vary wildly depending on what parts you include. 2K is
for a shell using all parts).
* Built with minimal tooling: only [scas][scas] is needed
* Can read and write to memory through shell
* Can run arbitrary routine from arbitrary address with arbitrary arguments
from shell.
* Can "upload" code from serial link into memory and execute it.
* Can manage multiple "block devices"
* Can read SD cards as block devices
* A z80 assembler written in z80 that is progressing well and should soon be
able to replace `scas`.
## Organisation of this repository
There's very little done so far, but here's how it's organized:
@ -107,40 +103,49 @@ There's very little done so far, but here's how it's organized:
* `recipes`: collection of recipes that assemble parts together on a specific
machine.
* `doc`: User guide for when you've successfully installed Collapse OS.
* `tools`: Tools for working with Collapse OS from "modern" environments. Mostly
development tools, but also contains emulated zasm, which is
necessary to build Collapse OS from a non-Collapse OS machine.
Each folder has a README with more details.
## Roadmap
Such a vast project involves quite a lot of fiddling and I can't really have a
precise roadmap, only a general direction:
The roadmap used to be really hazy, but with the first big goal (that was to
have a self-assembling system) reached, the feasability of the project is much
more likely and the horizon is clearing out.
The primary target for Collapse OS is the z80 architecture. There's a good
amount of great z80-related hacks all around the internet, and the z80 CPU is
very scavenge-friendly: it's been (and is) included in tons of devices.
As of now, that self-assembling system is hard to use outside of an emulated
environment, so the first goal is to solidify what I have.
After a good proof of concept is done in z80, then more architectures can be
added into the mix. I have the intuition that we can mix AVR and z80 in a very
elegant minimal and powerful machine and it would be great if a Collapse OS
spawn could be built for such machine.
1. Error out gracefully in ZASM. It can compile almost any valid code that scas
can, but it has undfined behavior on invalid code and that make it very hard
to use.
2. Make shell, CFS, etc. convenient enough to use so that I can easily assemble
code on an SD card and write the binary to that same SD card from within a
RC2014.
I'm planning to go forward with this project by doing three things:
After that, then it's the longer term goals:
1. Gather knowledge and hone skills.
2. Build useful parts of code to be assembled into an OS by the user.
3. Write "recipes", examples of assembly on real machines using parts I wrote
to serve as a guide for post-collapse assembly.
1. Get out of the serial link: develop display drivers for a vga output card
that I have still to cobble up together, then develop input driver for some
kind of PS/2 interface card I'll have to cobble up together.
2. Add support for writing to flash/eeprom from the RC2014.
3. Add support for floppy storage.
4. Add support for all-RAM systems through bootloading from storage.
Recipes should contain both "pre-collapse" instructions (how to build Collapse
OS from a "modern" system) and "post-collapse" instructions (how to build
Collapse OS from itself).
Then comes the even longer term goals, that is, widen support for all kind of
machines and peripherals. It's worth mentionning, however, that supporting
*specific* peripherals isn't on the roadmap. There's too many of them out there
and most peripheral post-collapse will be cobbled-up together anyway.
Initially, we of course only have "pre-collapse" instructions, but as tooling
improve, the "post-collapse" part will become more and more complete. When we
have complete "post-collapse" recipes, we can call it a win.
The goal is to give good starting point for as many *types* of peripherals
possible.
If you're interested in being part of this project, I have no idea how to
include you, but please, let me know, we'll manage something.
It's also important to keep in mind that the goal of this OS is to program
microcontrollers, so the type of peripherals it needs to support is limited
to whatever is needed to interact with storage, serial links, display and
receive text, do bit banging.
## Open questions
@ -172,14 +177,14 @@ First, because I think there are more scavenge-friendly 8-bit chips around than
scavenge-friendly 16-bit or 32-bit chips.
Second, because those chips will be easier to replicate in a post-collapse fab.
If the first chips we're able to create post-collapse are low-powered, we might
as well design a system that works well on low-powered chips.
The z80 has 9000 transistors. 9000! Compared to the millions we have in any
modern CPU, that's nothing! If the first chips we're able to create
post-collapse have a low transistor count, we might as well design a system
that works well on simpler chips.
That being said, nothing stops the project from including the capability of
programming an ARM or RISC-V chip.
That being said, the MSP430 seems like a really nice and widely used chip...
### Prior art
I've spent some time doing software archeology and see if something that was
@ -212,4 +217,4 @@ sound more or less crazy to you than what you've been reading in this text so
far?), I will probably need help to pull this off.
[searle]: http://searle.hostei.com/grant/z80/SimpleZ80.html
[scas]: https://github.com/KnightOS/scas
[libz80]: https://github.com/ggambetta/libz80

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doc/emulate.md
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@ -2,7 +2,7 @@
The quickest way to give Collapse OS a whirl is to use `tools/emul` which is
built around [libz80][libz80]. Everything is set up, you just have to run
`make`.
`make`, then `shell/shell`.
To emulate something at a lower level, I recommend using Alan Cox's [RC2014
emulator][rc2014-emul]. It runs Collapse OS fine but you have to write the
@ -13,13 +13,13 @@ A working Makefile for a project with a glue code being called `main.asm` could
look like:
TARGET = os.bin
PARTS = ~/collapseos/parts
ZASM = ~/collapseos/tools/emul/zasm/zasm
ROM = os.rom
.PHONY: all
all: $(ROM)
$(TARGET): main.asm
scas -o $@ -L map -I $(PARTS) $<
$(ZASM) < $< > $@
$(ROM): $(TARGET)
cp $< $@

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doc/glue-code.md
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@ -1,15 +1,16 @@
# Writing the glue code
Collapse OS is not an OS, it's a meta OS. It supplies parts that you're expected
to glue together in a "glue code" asm file. Here is what a minimal glue code
for a shell on a Classic [RC2014][rc2014] with an ACIA link would look like:
Collapse OS's kernel code is loosely knit. It supplies parts that you're
expected to glue together in a "glue code" asm file. Here is what a minimal
glue code for a shell on a Classic [RC2014][rc2014] with an ACIA link would
look like:
; The RAM module is selected on A15, so it has the range 0x8000-0xffff
RAMSTART .equ 0x8000
RAMEND .equ 0xffff
ACIA_CTL .equ 0x80 ; Control and status. RS off.
ACIA_IO .equ 0x81 ; Transmit. RS on.
.equ RAMSTART 0x8000
.equ RAMEND 0xffff
.equ ACIA_CTL 0x80 ; Control and status. RS off.
.equ ACIA_IO 0x81 ; Transmit. RS on.
jr init
@ -29,18 +30,28 @@ for a shell on a Classic [RC2014][rc2014] with an ACIA link would look like:
jp shellLoop
#include "core.asm"
ACIA_RAMSTART .equ RAMSTART
.equ ACIA_RAMSTART RAMSTART
#include "acia.asm"
SHELL_RAMSTART .equ ACIA_RAMEND
.equ SHELL_RAMSTART ACIA_RAMEND
.define SHELL_GETC call aciaGetC
.define SHELL_PUTC call aciaPutC
.define SHELL_IO_GETC call aciaGetC
SHELL_EXTRA_CMD_COUNT .equ 0
.equ SHELL_EXTRA_CMD_COUNT 0
#include "shell.asm"
Once this is written, building it is easy:
Once this is written, building it is easy:
scas -o collapseos.bin -I /path/to/parts glue.asm
zasm < glue.asm > collapseos.bin
## Building zasm
Collapse OS has its own assembler written in z80 assembly. We call it
[zasm][zasm]. Even on a "modern" machine, it is that assembler that is used,
but because it is written in z80 assembler, it needs to be emulated (with
[libz80][libz80]).
So, the first step is to build zasm. Open `tools/emul/README.md` and follow
instructions there.
## Platform constants
@ -106,7 +117,7 @@ effective, only works for one table per part. But it's often enough.
For example, to define extra commands in the shell:
[...]
SHELL_EXTRA_CMD_COUNT .equ 2
.equ SHELL_EXTRA_CMD_COUNT 2
#include "shell.asm"
.dw myCmd1, myCmd2
[...]
@ -118,3 +129,5 @@ and this much depends on the part you select. But if you want a shell, you will
usually end it with `shellLoop`, which never returns.
[rc2014]: https://rc2014.co.uk/
[zasm]: ../tools/emul/README.md
[libz80]: https://github.com/ggambetta/libz80

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doc/load-run-code.md
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@ -16,7 +16,7 @@ machine:
(we must always return at the end of code that we call with `call`). This will
increase a number at memory address `0xa100`. First, compile it:
scas -o tosend.bin tosend.asm
zasm < tosend.asm > tosend.bin
Now, we'll send that code to address `0xa000`:
@ -108,8 +108,8 @@ like (important fact: `jp <addr>` uses 3 bytes):
It then becomes easy to build yourself a predictable and stable jump header,
something you could call `jumptable.inc`:
JUMP_PRINTSTR .equ 0x03
JUMP_ACIAPUTC .equ 0x06
.equ JUMP_PRINTSTR 0x03
.equ JUMP_ACIAPUTC 0x06
You can then include that file in your "user" code, like this:

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tools/emul/README.md
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@ -1,10 +1,22 @@
# emul
This is an emulator for a virtual machine that is suitable for running Collapse
OS. The goal of this machine is not to emulate real hardware, but rather to
serve as a development platform. What we do here is we emulate the z80 part,
the 64K memory space and then hook some fake I/Os to stdin, stdout and a small
storage device that is suitable for Collapse OS's filesystem to run on.
This folder contains a couple of tools running under the [libz80][libz80]
emulator.
## Build
First, make sure that the `libz80` git submodule is checked out. If not, run
`git submodule init && git submodule update`.
After that, you can run `make` and it builds all tools.
## shell
Running `shell/shell` runs the shell in an emulated machine. The goal of this
machine is not to simulate real hardware, but rather to serve as a development
platform. What we do here is we emulate the z80 part, the 64K memory space and
then hook some fake I/Os to stdin, stdout and a small storage device that is
suitable for Collapse OS's filesystem to run on.
Through that, it becomes easier to develop userspace applications for Collapse
OS.
@ -13,26 +25,35 @@ We don't try to emulate real hardware to ease the development of device drivers
because so far, I don't see the advantage of emulation versus running code on
the real thing.
## Bootstrapped binary
## zasm
The file `zasm/zasm.bin` is a compiled binary for `apps/zasm/glue.asm`. It is
`zasm/zasm` is `apps/zasm` wrapped in an emulator. It is quite central to the
Collapse OS project because it's used to assemble everything, including itself!
The program takes no parameter. It reads source code from stdin and spits
binary in stdout. It supports includes and had both `apps/` and `kernel` folder
packed into a CFS that was statically included in the executable at compile
time.
The file `zasm/zasm.bin` is a compiled binary for `apps/zasm/glue.asm` and
`zasm/kernel.bin` is a compiled binary for `tools/emul/zasm/glue.asm`. It is
used to bootstrap the assembling process so that no assembler other than zasm
is required to build Collapse OS.
This binary is fed to libz80 to produce the `zasm/zasm` "modern" binary and
once you have that, you can recreate `zasm/zasm.bin`.
once you have that, you can recreate `zasm/zasm.bin` and `zasm/kernel.bin`.
This is why it's included as a binary in the repo, but yes, it's redundant with
the source code.
## Usage
Those binaries can be updated with the `make updatebootstrap` command. If they
are up-to date and that zasm isn't broken, this command should output the same
binary as before.
First, make sure that the `libz80` git submodule is checked out. If not, run
`git submodule init && git submodule update`.
## runbin
The Makefile in this folder has multiple targets that all use libz80 as its
core. For example, `make shell` will build `./shell`, a vanilla Collapse OS
shell. `make zasm` will build a `./zasm` executable, and so on.
This is a very simple tool that reads binary z80 code from stdin, loads it in
memory starting at address 0 and then run the code until it halts. The exit
code of the program is the value of `A` when the program halts.
See documentation is corresponding source files for usage documentation of
each target.
This is used for unit tests.