RISC-V Open Source Supervisor Binary Interface (OpenSBI)

The RISC-V Supervisor Binary Interface (SBI) is a recommended interface between:

1. A platform specific firmware (M-mode) and a general purpose OS or hypervisor or bootloader (S-mode or HS-mode).
2. A hypervisor (HS-mode) and a general purpose OS or bootloader (VS-mode)

The RISC-V SBI specification is maintained as an independent project by the RISC-V Foundation in Github

OpenSBI aims to provides an open-source and extensible implementation of the RISC-V SBI specification for case 1 mentioned above. OpenSBI implementation can be easily extended by RISC-V platform or System-on-Chip vendors to fit a particular hadware configuration.

OpenSBI provides three components:

1. libsbi.a - A generic OpenSBI static library
2. libplatsbi.a - Platform specific OpenSBI static library, that is, libsbi.a plus platform specific hooks
3. firmwares - Platform specific bootable firmware binaries

Building and Installing generic libsbi.a

For cross-compiling, the environment variable CROSS_COMPILE must be defined to specify the toolchain executable name prefix, e.g. riscv64-unknown-elf- if the gcc executable used is riscv64-unknown-elf-gcc.

To build the generic OpenSBI library libsbi.a, simply execute:

make

All compiled binaries will be placed in the build directory. To specify an alternate build directory target, run:

make O=<build_directory>

To generate files to be installed for using libsbi.a in other projects, run:

make install

This will create the install directory with all necessary include files and binary files under it. To specify an alternate installation directory, run:

make I=<install_directory> install

Building and Installing platform specific libsbi.a and firmwares

The libplatsbi.a and firmware files are only built if the PLATFORM=<platform_subdir> argument is specified on make command lines. <platform_subdir> must specify the path to one of the leaf directories under the platform directory. For example, to compile the library and firmware for QEMU RISC-V virt machine, <platform_subdir> should be qemu/virt.

To build libsbi, libplatsbi, and firmwares for a specific platform, run:

make PLATFORM=<platform_subdir>
or
make PLATFORM=<platform_subdir> O=<build_directory>

To install libsbi, headers, libplatsbi, and firmwares, run:

make PLATFORM=<platform_subdir> install
or
make PLATFORM=<platform_subdir> I=<install_directory> install

In addition, platform specific make command-line options to top-level make , such as PLATFORM_ or FW_ can also be specified. These options are described under docs/platform/<platform_name>.md and docs/firmware/<firmware_name>.md.

Documentation

A more detailed documenation is under the docs directory and organized as follows.

• docs/contributing.md - Guidelines for contributing to OpenSBI project
• docs/platform_guide.md - Guidelines for adding new platform support
• docs/library_usage.md - Guidelines for using the static library
• docs/platform/<platform_name>.md - Documentation for the platform <platform_name>
• docs/firmware/<firmware_name>.md - Documentation for the firmware <firmware_name>

The source code is also well documented. For source level documentation, doxygen style is used. Please refer to [Doxygen manual] (http://www.stack.nl/~dimitri/doxygen/manual.html) for details on this format.

The Doxygen can be installed on your debian build system using following:

sudo apt-get install doxygen doxygen-latex doxygen-doc doxygen-gui graphviz

To build a consolidated refman.pdf of all documenation, run:

make docs
or
make O=<build_directory> docs

NOTE: refman.pdf will be available under <build_directory>/docs/latex.

To install a consolidated refman.pdf of all documenation, run:

make install_docs
or
make I=<install_directory> install_docs

NOTE: refman.pdf will be installed under <install_directory>/docs.