browserbox

Browserbox is a risc-v emulator built with Zig to run in WASM.

# prerequisites
mise use -g zig@0.16.0        # or any install of zig 0.16.0
brew install wasmer

# build: native emulator, wasm32-wasi emulator, and the RISC-V ELF test programs
mkdir -p asm/elf
zig build # -> zig-out/bin/browserbox, zig-out/bin/browserbox.wasm, asm/elf/*.elf

# test: unit tests + run every ELF in asm/elf through the emulator
zig build test

# run fibonocci natively
zig build run -- --elf asm/elf/fibonocci.elf
./zig-out/bin/browserbox --elf asm/elf/fibonocci.elf

# run fibonocci in the wasm emulator under wasmer
wasmer run zig-out/bin/browserbox.wasm --volume .:/app --cwd /app -- --elf /app/asm/elf/fibonocci.elf

Instruction set support

Freestanding builds targeting riscv64 with c, m, a, f, d subtracted (see build.zig) should work.

Set	Status	Notes
RV32I base	✅ all 40	ecall / ebreak decode but execute as no-ops that don't advance PC
RV64I *W + ld / sd / lwu	✅ all 12
Zifencei (fence, fence.i)	✅	no-ops, single-hart
Zicsr (csrr[wsc], csrr[wsc]i)	✅	S-mode CSRs only: sstatus sie stvec sscratch sepc scause stval sip satp
Sv39 paging	✅
Privileged (mret, sret, uret, wfi)	⚠️	decoded, panic on execute
M (mul / div)	❌	parser panics on unknown funct7
A (atomics)	❌
F / D (float)	❌
C (compressed)	❌