This commit is contained in:
Michael Zhang 2023-02-04 03:13:22 -06:00
commit 13bc0fc2f9
12 changed files with 687 additions and 0 deletions

1
.envrc Normal file
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use flake

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.gitignore vendored Normal file
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/target
.direnv
result*
*.o

390
Cargo.lock generated Normal file
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10
Cargo.toml Normal file
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[package]
name = "riscv64-emulator"
version = "0.1.0"
edition = "2021"
[dependencies]
anyhow = "1.0.68"
clap = { version = "4.1.4", features = ["derive"] }
goblin = "0.6.0"
scroll = "0.11.0"

4
Makefile Normal file
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CC := riscv64-unknown-linux-gnu-gcc
main.o: main.c
$(CC) -o $@ $<

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flake.lock Normal file
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{
"nodes": {
"fenix": {
"inputs": {
"nixpkgs": "nixpkgs",
"rust-analyzer-src": "rust-analyzer-src"
},
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"narHash": "sha256-5Tvd/8kFl+jQ+uYqam/Q1ZRWLNrkF97zRX/l0pUitpU=",
"owner": "nix-community",
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},
"original": {
"owner": "nix-community",
"repo": "fenix",
"type": "github"
}
},
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"type": "github"
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},
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"owner": "nixos",
"repo": "nixpkgs",
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"repo": "nixpkgs",
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"owner": "nixos",
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"flake-utils": "flake-utils",
"nixpkgs": "nixpkgs_2"
}
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"flake": false,
"locked": {
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"narHash": "sha256-Y7VnQlwTckCG4ia1zHSxF1mYKfNjfWUlzRyoLTbLn5U=",
"owner": "rust-lang",
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"root": "root",
"version": 7
}

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flake.nix Normal file
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{
inputs = { fenix.url = "github:nix-community/fenix"; };
outputs = { self, nixpkgs, flake-utils, fenix }:
flake-utils.lib.eachDefaultSystem (system:
let
pkgs = import nixpkgs {
inherit system;
overlays = [ fenix.overlays.default ];
};
toolchain = pkgs.fenix.stable;
targetPkgs = pkgs.pkgsCross.riscv64;
in rec {
legacyPackages = pkgs;
devShell = pkgs.mkShell {
inputsFrom = [ ];
packages = (with pkgs; [
cargo-watch
cargo-deny
cargo-edit
targetPkgs.stdenv.cc
(qemu.override {
hostCpuTargets = [ "${targetPkgs.system}-user" ];
})
]) ++ (with toolchain; [ cargo rustc rustfmt clippy ]);
};
});
}

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main.c Normal file
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#include <stdio.h>
int main() {
printf("Hello, world!\n");
}

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rustfmt.toml Normal file
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max_width = 80
tab_spaces = 2

102
src/emulator.rs Normal file
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use std::collections::HashMap;
use anyhow::Result;
use goblin::elf::Elf;
use scroll::{Endian, Pread};
// IMPORTANT PAGES IN THE RISC-V SPEC
// https://riscv.org/wp-content/uploads/2017/05/riscv-spec-v2.2.pdf
//
// - 103 (Ch. 19) - Instruction Set Listings (Opcodes)
use crate::instruction::Instruction;
pub type Address = u64;
pub struct Emulator<'a> {
contents: &'a [u8],
elf: Elf<'a>,
endianness: Endian,
program_counter: u64,
registers: [u64; 32],
memory_map: HashMap<Address, &'a [u8]>,
}
impl<'a> Emulator<'a> {
pub fn new(contents: &'a [u8]) -> Result<Self> {
let elf = Elf::parse(&contents)?;
let endianness = elf.header.endianness()?;
Ok(Emulator {
contents,
elf,
endianness,
program_counter: 0,
registers: [0; 32],
memory_map: HashMap::new(),
})
}
pub fn run(&mut self) -> Result<()> {
// Set up memory segments
for program_header in self.elf.program_headers.iter() {
let start = program_header.p_offset as usize;
let end = start + program_header.p_memsz as usize;
let memory_slice = &self.contents[start..end];
self.memory_map.insert(program_header.p_vaddr, memory_slice);
}
println!("Elf entrypoint: 0x{:x?}", self.elf.entry);
self.program_counter = self.elf.entry;
self.step()?;
self.step()?;
Ok(())
}
fn step(&mut self) -> Result<()> {
let instruction = self.decode_instruction_at(self.program_counter)?;
self.program_counter += instruction.len as u64;
Ok(())
}
fn decode_instruction_at(&self, addr: Address) -> Result<Instruction> {
let data = self.read_memory_at(addr, 2).unwrap();
let data_num = data.pread_with::<u16>(0, self.endianness)?;
// If the instruction has 11 at the end, it's longer
if data_num & 0b11 == 0b11 {
let data = self.read_memory_at(addr, 4).unwrap();
let data_num = data.pread_with::<u32>(0, self.endianness)?;
println!("{:b}", data_num);
// TODO: If the instruction ends with 11111, it's longer
// JAL
if data_num & 0b1111111 == 0b1101111 {
return Ok(Instruction { len: 4 });
}
} else {
println!("{:b}", data_num);
}
todo!()
}
/// Read n bytes from addr
// TODO: Could speed this up massively
fn read_memory_at(&self, addr: Address, n: usize) -> Option<&[u8]> {
for (memory_addr, memory_slice) in self.memory_map.iter() {
if addr >= *memory_addr && addr < memory_addr + memory_slice.len() as u64
{
let start = (addr - *memory_addr) as usize;
let end = (start + n) as usize;
return Some(&memory_slice[start..end]);
}
}
None
}
}

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src/instruction.rs Normal file
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#[derive(Debug)]
pub struct Instruction {
/// The number of bytes in this instruction
pub len: usize,
}
#[derive(Debug)]
pub enum Op {}

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src/main.rs Normal file
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mod emulator;
mod instruction;
use std::fs::File;
use std::io::Read;
use std::path::PathBuf;
use anyhow::Result;
use clap::Parser;
use crate::emulator::Emulator;
#[derive(Debug, Parser)]
struct Opt {
input_path: PathBuf,
}
fn main() -> Result<()> {
let opt = Opt::parse();
println!("Hello, world! {opt:?}");
let contents = {
let mut contents = Vec::new();
let mut file = File::open(&opt.input_path)?;
file.read_to_end(&mut contents)?;
contents
};
let mut emulator = Emulator::new(&contents)?;
emulator.run()?;
Ok(())
}