An extensible RISC-V assembler written in Rust. The goal of this project is to provide a platform for experimentation with the RISC-V architecture by having an assembler that allows for quick iteration of tiny programs compiled into flat binaries, and of instruction sets defined in simple to edit TOML 0.5 files.

USAGE:
    rvasm [FLAGS] [OPTIONS] [--] [input_file]

FLAGS:
    -h, --help       Prints help information
    -b, --binary     In addition to writing a file, print the assembly in binary to the terminal
    -V, --version    Prints version information
    -v, --verbose    Enable additional output

OPTIONS:
    -a, --arch <arch>                  RISC-V variant to assemble for, like RV32IMZamZifencei (finds config files in
                                       standard path) [default: RV32I]
    -c, --cfg <cfg>...                 Additional config file paths to parse
    -s, --string <input_string>        Input string instead of file, all semicolons are replaced by newlines
    -o, --output-file <output_file>    Output (assembled) file path
    -f, --format <output_format>       Output file format (only `flat` binary is supported) [default: flat]

ARGS:
    <input_file>    Input file path

For example, if you have a file sample1.s:

addi s0, s1, 2+2

You can assemble it by using the command rvasm sample1.s -o sample1.bin. This is the equivalent of options: rvasm sample1.s -o sample1.bin -a RV32I -f flat

If you'd like to peek into the binary representation of instructions (only 32-bit ILEN supported now), you can invoke rvasm like this:

rvasm -s "addi s0, s1, 2+2" -b

Which will produce the following output:

Binary assembly:
00000000010001001000010000010011 
Warning: no output file specified so none was created.

Which displays the 32-bit instructions as 32 binary digits, rightmost one is the LSB and leftmost is MSB. (Swapped around from the actual little endian byte encoding for readability)

Create a copy of cfg/help.toml and follow the comments to define instruction formats and specific encodings. You can also take a look at the included RV32I definition in cfg/rv32i.toml.

Apart from the instructions defined in the TOML files, the assembler supports a few directives:

• $ - replaced by current PC value
• .org ADDRESS - sets the internal PC value and output file position to ADDRESS
• .equ NAME VAL/.define NAME VAL - defines constants that can be used in expressions instead of integers
• .label: - labels starting with a dot are local to the scope of their parent label