RISC V binutils

How to get binutils source files

RISC-V binutils must be build manually, so first you'll need to get sources.

The source files are stored in GitHub repository in the RISC-V's riscv-gnu-toolchain project. Use git to get a local clone of the repository (--recursive option is required to get all submodules):

git clone --recursive https://github.com/riscv/riscv-gnu-toolchain

In case if submodules were not initialized automatically (their folders contain only .git file), set them manually from the project root:

cd riscv-gnu-toolchain
git submodule foreach 'git reset --hard'

You can face problem with cloning "qemu" submodule. It is not required for the most of our usage cases, thus this can be ignored.

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How to build binutils

This cheat-sheet is based on GitHub README. See it if you have any problem or need more information.

# Install prerequisites
sudo apt-get install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev gawk build-essential \
    bison flex texinfo gperf libtool patchutils bc zlib1g-dev libexpat-dev

# For convenience, you can proceed the build from project root
cd riscv-gnu-toolchain

# Create a directory where the binutils will be installed (can be any)
mkdir bin

# Create a directory for a build process (can be any), enter it
mkdir build && cd build

# Configure build (configures for RV64GC by default) using script from the project root.
# Set absolute path of destination binutils directory ("bin") for "prefix" flag
../configure --prefix=/riscv-gnu-toolchain/bin

# Make sources (can dump a lot of info). Paralleling can be archieved by specifying "-j NUMBER_OF_WORKERS" flag.
# Note: environment variables $CXX ($CC) should point to compiler supporting at least C++11 by default.
make

# Install (can dump a lot of info, usually requires sudo)
sudo make install

# Update $PATH variable to have binaries available
export PATH=$PATH:/riscv-gnu-toolchain/bin/bin
setenv PATH $PATH:/riscv-gnu-toolchain/bin/bin

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Create a RISC-V binary with binutils

• Create a file with assembler code and save it as <test name>.s

Note: Specify __start: before the first instruction of your program. This is required by mipt-mips to find a starting point of execution.

• Generate an object file:

riscv64-unknown-elf-as <test name>.s -o <test name>.o

• Convert the object file into the binary file:

riscv64-unknown-elf-ld <test name>.o -o <test name>.out

• (optional) Look the content of .out using (pay attention only to .text section):

riscv64-unknown-elf-objdump -D <test name>.out

Note that in addition to assembler this RISC-V GNU toolchain also includes C and C++ cross-compiler, so you can also build C/C++ code into a RISC-V binary on regular x86 machines.