Show HN: A DOS-like hobby OS written in Rust and x86 assembly

To try it out, simply build the project yourself from source, or use attached bootable ISO image of the system (in Releases on Github) and run it in QEMU.

https://blog.vxn.dev/rou2exos-rusted-edition

github.com

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207 points

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krustowski

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14 days ago

61 comments

rollcat ・ 13 days ago

Memory-safe language. x86_64, with Arm on the roadmap. Networking stack. Boots from a CD and via multiboot. Your hobby project wipes the floor with DOS.

  • pvg ・ 13 days ago

    Whoa there. Gotta run Doom and BASIC to compete with DOS. That is the officially recognized DOS-Kármán line.

    • rollcat ・ 13 days ago

      DOOM required DOS 5.0. rou2exOS is only the second take. Watch this area ;)

    • pjmlp ・ 13 days ago

      Borland languages and xBase ecosystem as well

    • jdsully ・ 13 days ago

      Nobody cares about Lotus 1-2-3 support any longer :)

      • jmspring ・ 13 days ago
        ・ 3 more

        What about Wordstar?

        • RoyTyrell ・ 12 days ago

          The text editor JOE has a WordStar mode.

        • hans_castorp ・ 13 days ago

          WordPerfect was better anyway :) (SCNR)

    • mycall ・ 13 days ago

      also, can't be a dos with the 'dir' command.

      • krustowski ・ 13 days ago
        ・ 9 more

        Afaik there is a 'DIR' command in MS-DOS. Anyway, what would be a better command to list a directory? I could think of 'ls' maybe

        • onre ・ 13 days ago
          ・ 6 more

          I would most likely end up with something like this:

            CAT          CATalogue - output the contents of current directory
  RM           to Raster Memory - load contents of named file in framebuffer
  MV           Make Virtual - map the file into memory and output the address
  LS           Load System - attempt to reboot using the named file as the kernel
  CD           Create Directory - self-explanatory
  SH           System Halt - immediately stop all processing
          ...and so on.
          • OccamsMirror ・ 13 days ago

            I suggest:

                RM           Relocate me - you could also use the "-rf" flag to relative fuzzy matching, for instance `rm -rf tmp` to find any temp-like folder near your current location. Pretty standard stuff.
    CD           Clear data - `cd -L /temp` would "liquidate" the directory.
            This would be a much simpler command interface.
          • anyfoo ・ 13 days ago

            Very good design. Implements only the essential tasks an operator would need with concise and well-known mnemonics. I’m sure this will be immediately intuitive to anyone, with no potential for mistakes whatsoever.

          • stuaxo ・ 12 days ago

            CAT was on the Amstrad CPC.

        • pjmlp ・ 13 days ago

          As someone old enough to have started on MS-DOS 3.3, dir has been there all time.

        • rzzzt ・ 13 days ago

          CATALOG, DSPFLR, Get-ChildItem

      • guestbest ・ 13 days ago
        ・ 2 more

        It would seem to logically follow that a Disk Operating System would have a directory list utility for disks like ‘dir’. It was there in the first version called 86 DOS.

        https://en.m.wikipedia.org/wiki/86-DOS

        • AndrewDavis ・ 13 days ago

          `dir` was also in CP/M. Though it didn't have a concept of a file hierarchy, so it listed all files on the disk (but did support supplying a pattern to filter against).

  • MoonGhost ・ 13 days ago

    > Rust and x86 assembly

    then

    > Memory-safe language.

    What's the point? Looks like today Rust is like 3D printing was. As if it makes something better. Printing was hyped and advertised by printers sellers and manufacturers. Finally they run out of money.

    As for project, it's cool if compatible with old soft. Otherwise suitable mostly for education and masochism. Long way to become practical anyway even if it gets traction.

    • whytevuhuni ・ 13 days ago

      The idea of Rust is not that it is 100% safe, but rather that it is able to encapsulate unsafety and divide the program in two parts:

      - unsafe code plus modules that support it (the "trusted base")

      - all the rest

      Rust's promise is that there is no way to trigger any undefined behavior from bugs happening in "all the rest" of the code. If that code makes for more than 95% of the total, then that's a huge win compared to a completely unsafe language.

      Also, Rust's support for inline assembly is in my opinion better than C's, it's much easier to specify and figure out the constraints on the boundary between Rust/assembly.

    • unchar1 ・ 13 days ago

      You can write memory safe code in any language, but having a machine i.e. the Rust compiler check it for you is less error-prone than if a human does it.

      Also if you look at the repo, only 3% of the codebase is in Assembly. IMO if >95% project is in Rust, you can definitely claim it's a Rust project.

      • PaulDavisThe1st ・ 12 days ago

        Finally, a positive comment about Rust that I can 100% agree with :)

    • krustowski ・ 13 days ago

      Well, the point is to experiment with Rust no_std+no_main environment while trying to educate myself on how the things work under the hood. The project itself is part "just" a rewritten system (from C to Rust), and part an enhancement of such system furthermore. It lacks the external program execution though yet.

mct ・ 13 days ago

I love that the networking stack uses SLIP and slattach(1)!

I was playing with a toy TCP/IP stack, and decided using SLIP over a pty on Linux was a great way to interface with the kernel. Unfortunately it looks like macOS previously shipped with slattach(1) a very long time ago, but no longer does.

I'm curios if other people have used SLIP on macOS to get a dead-simple, cross-platform API to the networking stack?

The alternative would be to use tun/tap on Linux and utun on macOS, but SLIP would be so much nicer.

OhNotAPaper ・ 13 days ago

Out of curiosity, why x86? Is it the preponderance of resources? The weird instruction format? The complexity of the boot sequence? Are you specifically trying to mimic DOS?

> A support for the ARM architecture (aarch) is coming soon too.

Wow! How do you support a DOS-like OS across multiple architectures when DOS itself is tightly tied to interactions among the program, the system code, and the architecture?

  • anyfoo ・ 13 days ago

    I have not looked at this project, but my guess would be: x86 is a widely available platform that, because of its history and relentless compatibility, contains a lot of legacy interfaces that make implement a very simple, thin-layer and “DOS-like OS” without the need to parse device trees, set up MMUs, deal with complex busses like PCI(e) and so on.

    It is much harder to bootstrap a simple OS in ARM, and it won’t stay very simple unless you accept significantly more limitations than you would under x86. (For example, you can’t do very much with the MMU off on ARM, and you also don’t have convenient BIOS interfaces that allow you to, say, read a sector, or wait for a keypress, with just a few lines of assembly).

  • krustowski ・ 13 days ago

    The x86 arch is used because this system iteration derives from the first one, which relies on BIOS interrupts and inline assembly in Turbo C. I am not trying to mimic (MS-)DOS exclusively, but both systems are highly inspired by it.

    IMO multiple archs could be supported as Rust compiler allows the target arch specification, so one would build a specific target before the build itself.

mixmastamyk ・ 13 days ago

I would have preferred something like this to the current UEFI environment and shell, a FLOSS 64-bit DOS-like. A cool retro boot manager and diagnostic env perhaps.

Could this run from an efi system partition? Seems to support fat12, what about gpt?

Does it poke video hardware like DOS, or have a terminal like output?

  • krustowski ・ 13 days ago

    Booting from an EFI system partition has not been tested yet. FAT12 is the only filesystem (ok, there is a memdisk implementation, but it won't work now) supported, so GPT is not supported at the moment too (yet). Kinda aiming for FAT32 implementation to be the very next implemented (flash disks are usually FAT32 iirc). Not sure about the last question: the OS utilizes/directly writes to the VGA buffer in memory, the provided resolution is 80x25 by GRUB.

    • mixmastamyk ・ 13 days ago

      So MBR partitions? Or no partitions, like from a floppy? Or perhaps it doesn’t know because grub handles that part.

      • krustowski ・ 13 days ago

        For FAT12, it reads the first sector (0 or bootsector) of the floppy provided to gather information like bytes per sector, reserved sectors count, LBA of the root directory, etc.

Toritori12 ・ 13 days ago

Good job OP, what a missed opportunity to say: "just a hobby, won't be big and professional like Linux" (:

pndy ・ 13 days ago

Are you planning adding support for Czech diacritics?

  • krustowski ・ 13 days ago

    I am not at the moment. The goal is to keep this iteration in English for now. The first iteration was in Czech in the beginning though.

DrNosferatu ・ 13 days ago

DOS-like but not DOS-compatible, correct?

  • krustowski ・ 13 days ago

    You are right. The first iteration however is 16bit and is very close to MS-DOS in terms of compatibility. Moreover, any OS that can handle simple disk I/O ops could be considered a DOS system too, innit?

    • leeter ・ 13 days ago

      Correct, there is a difference between MS-DOS and IBM-PC compatible and a DOS (ex: all the DOSes that existed for Amiga/Apple II/Commodore etc). There are many DOSes (and even MSDOSes, because yay early PC era incompatibilities!), but there is a very dubious list of things needed to be MS-DOS and IBM-PC compatible. You can probably do it if you're willing to setup a hypervisor and emulate some hardware.

      NGL one of my long term projects was/is something exactly like this but UEFI and secure boot. The idea being to use the VM extensions to create IBM-PC and DOS compatible environments. For anything using DPMI[1] I'd probably do the same trick as Win95 did and just replace it with my own implementation so it's not too overburdened with layers.

      [1] https://en.wikipedia.org/wiki/DOS_Protected_Mode_Interface

      • JdeBP ・ 13 days ago
        ・ 2 more

        A version of (say) FreeDOS that was layered on top of the EFI API instead of PC98 firmware interrupts would be quite interesting. That would be a major architectural change to most of the programs, of course. But one would have provided the EFI Shell with essentially a complete suite of MS-DOS (albeit not PC-DOS or DR-DOS) commands. That could probably be quite easily ported to (say) ARM whereas the original still has x86isms.

        On the other hand, did you see https://github.com/FlyGoat/csmwrap when it came up a few weeks ago?

        * https://news.ycombinator.com/item?id=44101828

        There are already projects to provide replacements for the vanished Compatibility Support Module.

        • leeter ・ 13 days ago

          I did see that and for people that need that specific functionality it seemed like a good solution.

          My goal was more "What if DOS hadn't ended and but kept up support for modern hardware" along with emulation of common things in DOS gaming. So for example you would be able to set up a PIV that mapped certain resources directly or emulated them depending on the need.

          Could I use DOSBox for this... yes, but this is a "why not" sort of thing. I figured it would be a good excuse to learn OS dev. But life has kept me busy for now.

    • snvzz ・ 13 days ago

      The 16bit one also looks fun[0] and would run on old PCs the new one does not. Have you considered open sourcing that one?

      0. https://krusty.space/projects/rourexos/

      • krustowski ・ 13 days ago

        NGL, the codebase of the first iteration is pretty much a mess. It had been written in my mid-teenage years, so the C code is not very consistent across the project. There is a filesystem prototype written in Go as well... Also, it is quite complex to even compile RoureXOS: it needs Borland TCC and TASM (ca 1989 btw) to properly build a 16bit executable(s). It is feasible to compile it using DOSBox though. Maybe some day I could open source that one repository too.

  • DrNosferatu ・ 13 days ago

    ...meaning MS-DOS compatible :)

    I.e.: runs Alley Cat and Dune 2 - and Doom.

    • JdeBP ・ 13 days ago

      And prevents Lotus 1-2-3 from running? (-:

      • vardump ・ 13 days ago

        That's the litmus test. No version of DOS is complete until Lotus 1-2-3 no longer runs.

m00dy ・ 13 days ago

it needs event queue to support async runtimes.

  • krustowski ・ 12 days ago

    How about the event loop in its completeness?

ta12653421 ・ 12 days ago

Can it run Crysis??

:-))

jmmv ・ 13 days ago

I don’t understand: what makes this “DOS-like”? Not even the command names match DOS, except for dir and cls, and the architecture and feature set are completely different.

  • klank ・ 13 days ago

    The original blog post has more details: https://krusty.space/projects/rourexos/

    Ultimately, it's an eye of the beholder type thing, but it seems very fair to call it DOS-like to me. The DOS inspiration is pretty blatant all throughout it from its aesthetic, commands (more than just dir and cls is shared), booting from a 1.44 floppy, etc. And if you are coming from a primarily windows computing background, then "DOS-like" is entirely appropriate to me.

    It looks like a fun project.

    • jmmv ・ 13 days ago

      Ah yes, the first version does indeed sound DOS-like. The second one diverges quite a bit though.

      Fun project indeed.

      • krustowski ・ 12 days ago

        You are right, it goes way ahead the first iteration. I call it DOS-like because of its resemblance to the Text mode-only operating systems (and to MS-DOS especially). On the other hand, it shares very little as the architecture, command set, or hardware utilization approach are concerned when compared to MS-DOS.