DuskOS

Dusk OS is a minimal Forth-based OS which is designed for minimal and undefined hardware. It is pitched as an early end of civilization project, although I don't know how much computing I'll be worrying about. It is interesting to me as a minimal OS project which is designed to run on minimal hardware. I wanted to look through the tour which can be found here: https://duskos.org/.

I built Dusk for Risc-V by cloing the git:

$ git clone https://git.sr.ht/\~vdupras/duskos

then building the Risc-V deployment:

$ cd duskos/deploy/riscv

$ make

$ make emul

I have previously setup Risc-V toolchains and qemu (Risc V Emulation) so this was pretty painless. I'm unsure if the deployment requires the gcc toolchain, but I'm pretty sure it doesn't.

Anyway, running this boots into DuskOS giving the prompt:

Dusk OS

134KB used 15MB free ok

Dusk works by providing free memory, I can check my current address:

here .x

800a65dc ok

I can see that Dusk was bootstrapped into address 0x8000_0000, which is consistent with my previous work with bare-metal Risc-V on this machine.

I can write hex to my free memory:

$cafebabe here !

 ok

here @ .x

cafebabe ok

here dump

:800a65dc beba feca 0000 0000 0000 0000 0000 0000 ................

:800a65ec 0000 0000 0000 0000 0000 0000 0000 0000 ................

:800a65fc 0000 0000 0000 0000 0000 0000 0000 0000 ................

:800a660c 0000 0000 0000 0000 0000 0000 0000 0000 ................

:800a661c 0000 0000 0000 0000 0000 0000 0000 0000 ................

:800a662c 0000 0000 0000 0000 0000 0000 0000 0000 ................

:800a663c 0000 0000 0000 0000 0000 0000 0000 0000 ................

:800a664c 0000 0000 0000 0000 0000 0000 0000 0000 ................

 ok

Dusk mostly supports C. I can load the C word with needs comp/c. and then compile a word using C:

:c int add54(int n){return n+54;}

5 add54 .

59 ok

Errors in the C code are handled with just an immediate error message:

:c int add54(int n){return n+54}

File: (none)

Line no: 1 token: }

wrong character ok

This is from missing the semicolon. Dusk features builtin assemblers. I haven't stumbled onto the word to get documentation yet, but I can load the assembler/dissassembler: needs asm/riscv and needs asm/riscvd.

Disassembling my add function:

' add54 dis

800ced6c addi   xRSP, xRSP, -4                    ffc10113

800ced70 sw     xRA, xRSP[0]                      00112023

800ced74 addi   xPSP, xPSP, -4                    ffc18193

800ced78 sw     xW, xPSP[0]                       0041a023

800ced7c lw     xW, xPSP[0]                       0001a203

800ced80 addi   x11, xZERO, 54 -> $00000036       03600593

800ced84 add    xW, xW, x11                       00b20233

800ced88 mv     xAcmp, xW                         00020e13

800ced8c mv     xBcmp, xZERO                      00000e93

800ced90 mv     x11, xPSP                         00018593

800ced94 addi   x11, x11, 4                       00458593

800ced98 mv     xAcmp, x11                        00058e13

800ced9c mv     xBcmp, xZERO                      00000e93

800ceda0 mv     xPSP, x11                         00058193

800ceda4 lw     xRA, xRSP[0]                      00012083

800ceda8 addi   xRSP, xRSP, 4                     00410113

 ok

It loads the top value of the stack into xW, loads 54 into x11 and then pushes the result onto the stack.

I can also use the assembler to define new words:

code add53 53 i) +, exit,

 ok

' add53 dis

800d27b4 addi   x11, xZERO, 53 -> $00000035       03500593

800d27b8 add    xW, xW, x11                       00b20233

800d27bc mv     xAcmp, xW                         00020e13

800d27c0 mv     xBcmp, xZERO                      00000e93

800d27c4 ret                                      00008067

800d27c8 ???                                      00000000

800d27cc ???                                      00000000

800d27d0 ???                                      00000000

At this point I have to figure some graphics which are not running on my qemu setup. They seem interesting to play with. I some further ideas about run-time compiling which I want to play with implementing.

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DuskOS