My little toy operating system from last year runs in 16-bit Real Mode (like DOS). Since I’ve recently figured out how to switch to 64-bit Long Mode right after BIOS boot, I now have a little program that performs this switch on my toy OS. It will load and run any x86-64 program, assuming it’s freestanding, a flat binary, and small enough (< 128 KiB code, only uses the first 2 MiB of memory).

Here I’m running a little C program (compiled using normal GCC, no Watcom trickery):

https://movq.de/v/b27ced6dcb/los86%2D64.mp4

https://movq.de/v/b27ced6dcb/c.png

Next steps could include:

• Use Rust instead of C for that 64-bit program?
  
• Provide interrupt service routines. (At the moment, it just keeps interrupts disabled.)

Seeing this run on real hardware is so satisfying, even if it’s just a small example. 😅

https://movq.de/v/ec46b8cf99/netbook.mp4

@movq@www.uninformativ.de It’d be cool if you could get µ (Mu) running in your little toyOS 🤣 You’d technically only have to swap out the syscall() builtin for whatever your toy OS supports 🤔

@prologic@twtxt.net That might be a challenge, at least in 16-bit Real Mode: The OS follows the model of COM files on DOS, i.e. the size of the binary cannot exceed 64 KiB and heap+stack of the running program will have to fit into that same 64 KiB. 😅 (The memory layout is very rigid, each process gets such a 64 KiB slice.)

And in 64-bit Long Mode, there is no “kernel” yet. The thing in the video is literally just a small bare-metal program.

But some day, maybe. 😃

@movq@www.uninformativ.de Oh that’s fine, Mu can compile to native code and so far binaries. at least on macOS are in the order of Kb in size 😂

@prologic@twtxt.net Oh! 🤔

@movq@www.uninformativ.de I think I can get binaries even smaller with a bit more work and effort 🤔 But yeah still working on the native code generation (at least for macOS targets)