enthusi/riscv_asm_tools

A collection of small programs and tools fully written in RiscV 64bit assembly

This is for learning and fun. I restrict myself to actual syscalls and RiscV 64bit. All written for the GNU-as.

Currently implemented: cat, mandelbrot.

mandelbrot

This code creates a buffer, injects a BMP header, generates an RGB palette table and computes a mandelbrot graphic to be written as a BMP file in 2048x1024 pix as default. You can provide two integers as command line arguments for a specific x y size (new ATOI() asm code). ./mandelbrot 8192 4096 takes 10 seconds on my VisionFive2. -> 708 Bytes.

cat

This tool comes in several flavors, in order of creation/complexity.

cat_buf

Reads/writes into 1K buffer repeatedly over file, over all files -> 800 Bytes with C-ext: 768 Bytes

cat_mmap_full

uses mmap syscall to fetch each input file as a whole at once and then write it out, over all files -> 760 Bytes with C-ext: 696 Bytes

cat_mmap_full_elf

Same as cat_mmap_full but includes its own minmal(ish) ELF64 header -> 352 Bytes with C-ext: 288 Bytes

TODOs

• maybe add error handling to cat family
• mandelbrot using fork()

Notes/Warnings

• compressed instructions don't take x0 as second argument for mv anymore.
• GNU-as translates mv a0,zero into li a0,0 but will NOT compress it. Use li a0,0 straight away.