RISC-V Emulator and Linux System from Scratch

Discussion of the corresponding blog post: https://news.ycombinator.com/item?id=49553988

Slight tangent: I made a similar but simpler project that runs DOOM on a custom RISC-V emulator: https://github.com/lalitshankarch/rvcore

Emulation of RISC-V in software;

container2wasm has TinyEmu for RISC-V.

dearchap/tinyemu: https://github.com/dearchap/tinyemu

Qemu also supports 32bit and 64bit RISC-V: "RISC-V System emulator — QEMU documentation" https://www.qemu.org/docs/master/system/target-riscv.html

Emu86 emulates RISC-V in Python and also WASM now IIRC: https://news.ycombinator.com/item?id=41899475 .. https://github.com/gcallah/Emu86/blob/master/assembler/virtu... :

  class RISCVMachine(VirtualMachine):

Also:

(Box96/Box64 emulates x86 on ARM64 and RISC-V; e.g. Portal)

From https://news.ycombinator.com/item?id=44979868 :

> openhwgroup has open Verilog implementations of RISC-V cores from 2 stages through 6 stages that will boot Linux: https://github.com/openhwgroup

>"Source Code

/lib contains the entire rv32ima instruction set emulator code as well as a minimal set of emulated devices"

The author of this GitHub repository is not lying when he says "minimal" -- basically it's an emulated 8250 UART, and that's it!

(Unless of course you count RAM (ram.hpp) and MMU (mmu.hpp) as "devices", in which case the emulated device count is three, as opposed to one...)

Now, that's not a bad thing... in fact, that's a very very good thing, an excellent thing in fact!

This whole project is brilliant!

But, let's truly understand its brilliance.

By writing this project the way it has been written, the author has stripped away somewhere between 1.5 to 2 million lines of QEMU source code (estimates put the lines of code in QEMU somewhere between these numbers), and replaced it with something far, far simpler to understand -- a decrease in the orders of magnitude of lines of code -- with a corresponding orders of magnitude increase of any given programmer's ability to understand the code.

Phrased another way:

"The learning curve for a programmer to understand a given piece of Open Source Software in a fixed time interval is approximately inversely proportional to its lines of code (LOC)."

The above repository, by reducing the lines of code necessary for an emulator to run Linux to its absolute, barest, vanilla minimum, correspondingly allows students (and future students!) of emulators to get a foothold on understanding what's going on under the hood, while having to wrestle with the least amount of lines of code (or close to it!) necessary to gain this understanding.

Well done! (And, a brilliant idea to only emulate a 8250 UART, by the way!)

    // Load the Linux Kernel to the start of the RAM   
    ram.write(0x00, LinuxKernel);   

lol