For building your own software, OpenRISC is supported by a 32-bit GNU toolchain offering C and C++ support. The toolchain is available in several forms, depending on your use case:

  • or1k-elf for bare metal use, based on the newlib library.

  • or1k-linux-uclibc for Linux application use, based on the uClibc library.

  • or1k-linux-musl for Linux application use, based on the musl library. (recommended over uClibc)

  • or1k-rtems* for building software that runs on the RTEMS operating system.

To run multiple applications in parallel and to use their rich features there is an up-to-date support for a few operating systems:

  • Linux is a widely used general purpose operating system.

  • RTEMS is a real-time operating system for embedded systems.

Baremetal Software

A cross-compiler toolchain is used to compile your software code for the OpenRISC processor. The toolchain is executed on the the host computer and generates a program or library that can be executed on the processor then. There is a baremetal toolchain that is based on the Newlib C library. Other toolchains to compile programs to be run on an operating system can be found below.

Basic Tool and Compiler Support

Some basic tools form an actual toolchain:

  • Binutils: Binutils contains tools needed for linking programs and libraries, compiling assembler code etc. The binutils distribution contains support for OpenRISC (or1k). Beside this a development repository is used to test new features before submitting it to the binutils project.

  • GCC: GCC is the compiler that translates C/C++ to programs or libraries. The GCC project does not support OpenRISC by default, but instead it is required to build GCC from our own cloned repository.

  • GDB: The debugger is used to find and fix bugs in programs running on the target platform. The GDB project does not support OpenRISC by default, but instead our cloned repository must be used.

Newlib Toolchain

Newlib is a C library for embedded systems. Our baremetal toolchain or1k-elf is built on it. The library provides the basic functions like printf and memory allocation. The libgloss is the part of newlib that does the actual hardware handling: It configures the processor, the UART and sets the stack according to the available physical memory. For this it depends on some external symbols, which are defined by board libraries and may be overwritten.

Beside the basic C library functionality, the libgloss port for OpenRISC defines some helper functions for exception and interrupt handling, timers and other peripherals. The latest releases and documentation can be found on the or1k-elf newlib website.

Operating Systems



musl Toolchain

The musl toolchain is the preferred toolchain for build programs that should run on Linux. The exceptions to this is software that depend on extensions only found in glibc. For example, building Debian requires glibc.

You can download prebuilt toolchains here or build it yourself following these instructions.


The RTEMS port was dead for a few years, but has been re-established in 2014 during a Google Summer of Code project. The student documented his work in his blog and the work is part of the RTEMS project now.