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Clarify OpenSBI components explanation.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
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Damien Le Moal
2019-02-07 18:11:41 +09:00
committed by Anup Patel
parent 76c759df6a
commit 7b3da0ef0d
1 changed files with 45 additions and 31 deletions
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README.md
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@@ -1,39 +1,52 @@
RISC-V Open Source Supervisor Binary Interface (OpenSBI)
========================================================
The **RISC-V Supervisor Binary Interface (SBI)** is a recommended interface
The **RISC-V Supervisor Binary Interface (SBI)** is the recommended interface
between:
1. A platform specific firmware running in M-mode and a general purpose OS,
hypervisor or bootloader running in S-mode or HS-mode.
2. A hypervisor running in HS-mode and a general purpose OS or bootloader
executed in VS-mode.
1. A platform specific firmware running in M-mode and bootloader, hypervisor or
a general purpose OS executing in S-mode or HS-mode.
2. A hypervisor running in HS-mode and a bootloader or a general purpose OS
executing in 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
The goal of the OpenSBI project is to provide an open-source reference
implementation of the RISC-V SBI specifications for platform specific firmwares
executing in M-mode (case 1 mentioned above). OpenSBI implementation can be
easily extended by RISC-V platform and system-on-chip vendors to fit a
particular hardware configuration.
OpenSBI provides three different components:
1. *libsbi.a* - A generic OpenSBI static library
2. *libplatsbi.a* - A platform specific OpenSBI static library, that is,
libsbi.a plus platform specific hooks
3. *firmwares* - Platform specific bootable firmware binaries
The main component of OpenSBI is provided in the form of a platform independent
static library **libsbi.a** implementing the SBI interface. A firmware or
bootloader implementation can link against this library to ensure conformance
with the SBI interface specifications. *libsbi.a* also defines an interface for
integrating with platform specific operations provided by the platform firmware
implementation (e.g. console access functions, inter-processor interrupts
control, etc).
Building and Installing the generic OpenSBI static library
----------------------------------------------------------
To illustrate the use of *libsbi.a* library, OpenSBI also provides a set of
platform specific support examples. For each example, a platform
specific static library *libplatsbi.a* can be compiled. This library implements
SBI calls processing by integrating *libsbi.a* with necessary platform dependent
hardware manipulation functions. For all supported platforms, OpenSBI also
provides several runtime firmware examples built using the platform
*libplatsbi.a*. These example firmwares can be used to replace the legacy
*riskv-pk* bootloader (aka BBL) and enable the use of well known bootloaders
such as [U-Boot].
*libsbi.a* can be natively compiled or cross-compiled on a host with a
different base architecture than RISC-V.
Building and Installing OpenSBI Platform Independent Library
------------------------------------------------------------
OpenSBI platform independent static library *libsbi.a* can be natively compiled
or cross-compiled on a host with a different base architecture than RISC-V.
For cross-compiling, the environment variable *CROSS_COMPILE* must be defined
to specify the name prefix of the RISC-V compiler toolchain executables, 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:
To build *libsbi.a* simply execute:
```
make
```
@@ -58,18 +71,18 @@ path, run:
make I=<install_directory> install
```
Building and Installing the platform specific static library and firmwares
--------------------------------------------------------------------------
Building and Installing a Reference Platform Static Library and Firmwares
-------------------------------------------------------------------------
The platform specific *libplatsbi.a* static library and the platform firmwares
are only built if the *PLATFORM=<platform_subdir>* argument is specified on
the make command line. *<platform_subdir>* must specify the relative path from
OpenSBI code directory to one of the leaf directories under the *platform*
directory. For example, to compile the platform library and firmwares for QEMU
RISC-V *virt* machine, *<platform_subdir>* should be *qemu/virt*.
When the *PLATFORM=<platform_subdir>* argument is specified on the make command
line, the platform specific static library *libplatsbi.a* and firmware examples
are built for the platform *<platform_subdir>* present in the directory
*platform* in OpenSBI top directory. For example, to compile the platform
library and firmware examples for QEMU RISC-V *virt* machine,
*<platform_subdir>* should be *qemu/virt*.
To build *libsbi.a*, *libplatsbi.a* and the firmwares for a specific platform,
run:
To build *libsbi.a*, *libplatsbi.a* and the firmwares for one of the supported
platform, run:
```
make PLATFORM=<platform_subdir>
```
@@ -144,11 +157,11 @@ Detailed documentation of various aspects of OpenSBI can be found under the
*docs* directory. The documentation covers the following topics.
* [Contribution Guideline]: Guideline for contributing code to OpenSBI project
* [Platform Support Guide]: Guideline for implementing support for new platforms
* [Library Usage]: API documentation of OpenSBI static library *libsbi.a*
* [Platform Support Guide]: Guideline for implementing support for new platforms
* [Platform Documentation]: Documentation of the platforms currently supported.
* [Firmware Documentation]: Documentation for the different types of firmware
build supported by OpenSBI.
examples build supported by OpenSBI.
OpenSBI source code is also well documented. For source level documentation,
doxygen style is used. Please refer to [Doxygen manual] for details on this
@@ -191,11 +204,12 @@ make I=<install_directory> install_docs
*refman.pdf* will be installed under *<install_directory>/docs*.
[Github]: https://github.com/riscv/riscv-sbi-doc
[U-Boot]: https://www.denx.de/wiki/U-Boot/SourceCode
[COPYING.BSD]: COPYING.BSD
[SPDX]: http://spdx.org/licenses/
[Contribution Guideline]: docs/contributing.md
[Platform Support Guide]: docs/platform_guide.md
[Library Usage]: docs/library_usage.md
[Platform Support Guide]: docs/platform_guide.md
[Platform Documentation]: docs/platform/platform.md
[Firmware Documentation]: docs/firmware/fw.md
[Doxygen manual]: http://www.stack.nl/~dimitri/doxygen/manual.html