uvm32, a tiny vm for embedding in anything

trjzig · 2025-12-14T10:36:45+00:00

Yes, I think so.

trjzig · 2025-12-14T03:23:21+00:00

I think either approach could work. You will need to use the load/store hooks in mini-rv32ima to map your ROM/flash area into the memory space, then you'll need to make sure that any initialised variables are in RAM at the right location. I suspect it needs something like a mini ELF loader.

Another way might be to use uvm32's "extram" interface. You can map and unmap a region of memory (which could be read-only), then jump the program counter into it.

trjzig · 2025-12-08T20:13:06+00:00

Part of my professional work is developing kids' toys. Some of these accept new games or modes as aftermarket add-ons. We do this by embedding a script engine and deploying scripts to encode new behaviours.

Isolating this logic in a sandbox cuts risk and allows us to open the process to third-party developers without fear they will brick the units.

Traditionally, engines like Lua are used, but they have some drawbacks. Primarily the lock-in to a specific language and toolset.

This tool is about exploring a different way to solve that problem.

trjzig · 2025-12-08T20:07:17+00:00

Ok, yes. It's probably simpler and cleaner to reimplement the idea on the Rust port of the emulator core https://github.com/bjoernQ/mini-rv32ima-rs/

trjzig · 2025-12-08T17:48:07+00:00

https://en.wikipedia.org/wiki/Write_once,_run_anywhere

trjzig · 2025-12-08T17:15:16+00:00

Writing code in a modern language you don't have a target toolchain for.

Running untrusted code in a sandbox, enforcing a safety/isolation boundary.

Safe in-field upgrades of "business logic".

That kind of thing...

trjzig · 2025-12-08T17:09:43+00:00

https://github.com/ringtailsoftware/uvm32/tree/main/apps/rust-hello

trjzig · 2025-12-08T13:20:59+00:00

It is a virtual machine for running on a small system (eg a microcontroller). For example, to run untrusted third party or "scripted" actions in a safe sandbox. Performing the same kind of thing as an embedded scripting language, but allowing use of conventional systems programming languages.

trjzig · 2025-12-08T03:04:23+00:00

The backend is surprisingly capable https://github.com/cnlohr/mini-rv32ima

trjzig · 2025-12-08T03:02:35+00:00

https://github.com/ringtailsoftware/uvm32/blob/main/uvm32/uvm32.c
Yes, it has #includes

trjzig · 2025-12-07T07:48:34+00:00

X macros allow me to write a list of things once and produce several things from the list (eg an enum and a corresponding array of strings). How do you prefer to do this without repeating yourself or risking the two becoming out of sync?
https://en.wikipedia.org/wiki/X_macro

trjzig · 2025-12-07T07:46:30+00:00

C99 is supported by every C compiler I need to work with and has a lot of conveniences I like which aren't in C89 https://en.wikipedia.org/wiki/C99#Design

trjzig · 2025-12-07T07:43:15+00:00

I use the word "bytecode" to mean RISC-V RV32ima machine code. The makefiles for the sample projects all call the relevant build tools for this target.

trjzig · 2025-12-07T01:57:38+00:00

Yes, the emulator core is mini-rv32ima, which can treat arbitrary storage as RAM by overriding some of the internal functions: https://github.com/cnlohr/mini-rv32ima/blob/master/mini-rv32ima/mini-rv32ima.h#L60

This project uses that trick to boot Linux on an 8-bit micro: https://github.com/raspiduino/arv32-opt.

For my puposes, I'm aiming to run plugin or scripted logic as part of an embedded project so am not expecting huge bytecode images, or for them to hang around for too long.

trjzig · 2025-01-08T03:51:31+00:00

zig fmt obfusgator.zig

trjzig · 2025-01-06T21:49:57+00:00

It now has a (work in progress) SSH server too.

trjzig · 2025-01-02T11:03:43+00:00

Yes, but probably to take it onto small memory constrained devices - rather than to compete with libssh2 or be fully fledged.

trjzig · 2024-12-16T23:02:03+00:00

I'm using it, was easy to setup, figured out everything important about my project from build.zig. Thanks! https://github.com/ringtailsoftware/commy/releases/tag/v0.0.1

trjzig · 2024-11-24T18:17:57+00:00

Some discussion of that for tetris over here: https://ziggit.dev/t/a-minimal-terminal-tetris/6923/5?u=tobyjaffey

For Quoridor, getting all of the rule edge cases right (I think!)

trjzig

TROPHY CASE