This directory contains libraries and example applications for developing Tock apps that sit above the kernel.
If you have not yet done so, it might be a good idea to start with the TockOS getting started guide, which will lead you through the installation of some tools that will be useful for developing and deploying applications on TockOS. In particular, it will give you a rust environment (required to install
tockloader, which you need to deploy applications on most boards.
And it will of course give you a board with TockOS installed which you can use to run the applications found in this repository.
So, if you haven't been there before, just head over there until it sends you back here.
Clone this repository.
$ git clone https://github.com/tock/libtock-c $ cd libtock-c
The main requirement to build the C applications in this repository is having cross compilers for embedded targets. You will need an
arm-none-eabitoolchain for Cortex-M targets.
$ brew tap ARMmbed/homebrew-formulae && brew update && brew install ARMmbed/homebrew-formulae/arm-none-eabi-gcc
Ubuntu (18.04LTS or later):
$ sudo apt install gcc-arm-none-eabi
$ sudo pacman -Syu arm-none-eabi-gcc arm-none-eabi-newlib
$ sudo dnf install arm-none-eabi-newlib arm-none-eabi-gcc-cs
Optional: libtock-c also includes support for building for RISC-V targets. These are not included by default since obtaining the toolchain can be difficult (as of July 2022). You will need a RISC-V toolchain that supports rv32 targets (64 bit toolchains support rv32 if compiled with multilib support). Some toolchains that can work:
To actually build for the RISC-V targets, add
RISCV=1to the make command:
$ make RISCV=1
$ brew tap riscv/riscv && brew update && brew install riscv-gnu-toolchain
Ubuntu (21.10 or later):
$ sudo apt install gcc-riscv64-unknown-elf picolibc-riscv64-unknown-elf
Ubuntu (21.04 or earlier):
Unfortunately, older Ubuntu does not provide a package for RISC-V libc. We have created a .deb file you can use to install a suitable libc based on newlib:
$ wget http://cs.virginia.edu/~bjc8c/archive/newlib_3.3.0-1_amd64.deb $ sudo dpkg -i newlib_3.3.0-1_amd64.deb
If you would rather compile your own newlib-based libc, follow the steps below. Section newlib-nano describes some extra config options to build a size optimised newlib.
# Download newlib 3.3 from https://sourceware.org/newlib/ $ wget ftp://sourceware.org/pub/newlib/newlib-3.3.0.tar.gz $ tar -xvf newlib-3.3.0.tar.gz $ cd newlib-3.3.0 # Disable stdlib for building $ export CFLAGS=-nostdlib # Run configure $ ./configure --disable-newlib-supplied-syscalls --with-gnu-ld --with-newlib --enable-languages=c --target=riscv64-unknown-elf --host=x86 --disable-multi-lib --prefix /usr # Build and then install $ make -j8 $ sudo make install
Alternatively, you may use a pre-compiled toolchain that we created with Crosstool-NG.
$ wget http://www.cs.virginia.edu/~bjc8c/archive/gcc-riscv64-unknown-elf-8.3.0-ubuntu.zip (or https://alpha.mirror.svc.schuermann.io/files/2023-08-17_gcc-riscv64-unknown-elf-8.3.0-ubuntu.zip) $ unzip gcc-riscv64-unknown-elf-8.3.0-ubuntu.zip # add gcc-riscv64-unknown-elf-8.3.0-ubuntu/bin to your `$PATH` variable.
$ sudo pacman -Syu riscv64-elf-gcc riscv32-elf-newlib arm-none-eabi-newlib riscv64-elf-newlib
dnf does not contain the
riscv-gnu-toolchain, an alternative is to compile from source. Start with some of the tools we need to compile the source.
$ sudo dnf install make automake gcc gcc-c++ kernel-devel texinfo expat expat-devel $ sudo dnf group install "Development Tools" "C Development Tools and Libraries"
riscv-gnu-toolchain, summarised instructions as stated here
$ git clone https://github.com/riscv/riscv-gnu-toolchain $ cd riscv-gnu-toolchain/
Note: add /opt/riscv/bin to your PATH, then,
$ ./configure --prefix=/opt/riscv --enable-multilib
--enable-multilibensures that "the multilib compiler will have the prefix riscv64-unknown-elf- or riscv64-unknown-linux-gnu- but will be able to target both 32-bit and 64-bit systems."
$ sudo make [might need elevated privileges writing to `/opt/`]
$ sudo make linux
you can also build
riscv64-unknown-linux-gnu, which can be useful with tock where
After the the source has been compiled and copied to
/opt/riscv/binhas appended to the PATH, the toolchain is ready to be used.
newlib can require a large amount of memory, especially for printing. If this is a concern you can instead use a more size optimised version. As of August 2020 there are a few options for this.
- See if the version of newlib from your distro already has the flags below enabled. If it does it's already size optimsed.
- See if your distro pacakges a newlib-nano (Debian does this) that will already include the flags below.
- See if your distro packages picolibc, which is a optimised fork of newlib.
- You can compile newlib with these extra flags:
--enable-newlib-reent-small \ --disable-newlib-fvwrite-in-streamio \ --disable-newlib-fseek-optimization \ --disable-newlib-wide-orient \ --enable-newlib-nano-malloc \ --disable-newlib-unbuf-stream-opt \ --enable-lite-exit \ --enable-newlib-global-atexit \ --enable-newlib-nano-formatted-io
Optional: libtock-c also includes support for building RISC-V targets with the LLVM clang compiler. If you have a compatible clang toolchain, you can add
CLANG=1to the make command to use clang instead of the default GCC.
$ make RISCV=1 CLANG=1
This support is only included for RISC-V targets as Cortex-M targets require the FDPIC support only present in GCC.
You will also need an up-to-date version of elf2tab. The build system will install and update this automatically for you, but you'll need Rust's cargo installed. If you have followed the getting started guide, everything should be in place.
You will also likely need Tockloader, a tool for programming apps onto boards. If you haven't installed it during the TockOS getting started guide:
$ pip3 install tockloader
$ pip3 install tockloader --user
Compiling and Running Applications
To compile all the examples, switch to the
examples directory and execute the
$ cd examples $ ./build_all.sh
This will install
elf2tab if it is not yet installed and compile all the
examples for cortex-m0, cortex-m3, cortex-m4, cortex-m7, and rv32imac. It does
this because the compiler emits slightly (or significantly) different
instructions for each variant. When installing the application,
will select the correct version for the architecture of the board being
The build process will ultimately create a
tab file (a "Tock Application
Bundle") for each example application. The
tab contains the executable code
for the supported architectures and can be deployed to a board using
tockloader. For example to one of the Nordic development boards:
$ tockloader install --board nrf52dk --jlink blink/build/blink.tab Installing apps on the board... Using known arch and jtag-device for known board nrf52dk Finished in 2.567 seconds
You can remove an application with
$ tockloader uninstall --board nrf52dk --jlink blink
or remove all installed applications with
$ tockloader uninstall --board nrf52dk --jlink
Tock applications are designed to be generic and run on any Tock-compatible
board. However, compiled applications typically depend on specific drivers,
which not all boards provide. For example, some applications expect an IEEE
802.15.4 radio interface which not all boards support. If you load an
application onto a board that does not support every driver/system call it uses,
some system calls will return error codes (
The next step is to read the overview that describes how applications in TockOS are structured and then look at some of the examples in detail. The description of the compilation environment may also be of interest.
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
We welcome contributions from all.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.