lilium-usi

Default USI for LiliumOS.

The USI Provides the following interfaces:

• Wrapper libraries for SCI functions (syscalls) exposed by the kernel,
• Functions from the ISO 9899 (C99 through C23),
• Unwind utilities, including the default exception handler,
• Interfaces with the runtime linker, and
• Additional API Support for interacting with the userspace.

Build instructions

Simple Build

If you have lilium build tools installed, you can just build using make. This builds the default configuration (see below). The configuration can then be installed with make install or make install-strip (SYSROOT may be set here to modify the base of the install directory)

Make builds can be customized by setting various variables on the command line. However, for more complex setups, it is recommended to use the autotools build instead.

Variables that can be set:

• ARCH: The architecture to build for. Defaults to the x86_64 (Note: In the future, the host architecture will be detected)
• TARGET: The full target to build for. Defaults to $(ARCH)-lilium-std. Note that overriding this does not override ARCH, which can cause constitency issues. It is recommended not to set this unless you want to change the build type.
• CC: Path to the C compiler (expected to be compatible with gcc or clang). Defaults to $(TARGET)-cc, which must be found in $PATH
• CXX: Path to the C++ compiler (expected to be compatible with gcc or clang). Defaults to $(TARGET)-c++, which must be found in $PATH
• AS: Path to the assembler (expected to be compatible with GNU AS). Defaults to $(TARGET)-as, which must be found in $PATH
• AR: Path to the archiver. Defaults to $(TARGET)-ar, which must be found in $PATH
• CFLAGS: Additional flags for the C compiler. Defaults to -O2 -g
• CXXFLAGS: Additional flags to the C++ compiler. Defaults to -O2 -g
• CPPFLAGS: Additional flags to the C Preprocessor (for both C and C++ source files)
• ASFLAGS: Additional flags to the assembler.
• LDFLAGS: Additional flags to the link wrapper (when building shared objects)
• enabled_subsystems: Subsystem wrapper libraries to build. Can be used to select subsystems without disabling userspace libraries. Defaults to all USI libraries
• enabled_libraries: All libraries to build. Note that overriding this will ignore the enabled_subsystems variable. Defaults to all subsystems set in enabled_subsystems plus all userspace libraries
• build_shared: Builds shared objects and dynamic linking support.
• build_static: Builds static libraries
  • Set build_static=pic to build static libraries with Position Independnt Code. Otherwise, static libraries are built with PIC if shared libraries are enabled, and PIE if shared libraries are disabled
• SYSROOT: Modifies the base directory for installs. Defaults to empty
• prefix: Install prefix (inside SYSROOT). Defaults to /usr
  • Other variables for the installdirs spec are provided and can be overriden.

Autotools

When considerable configuration is used, it is recommended to use autotools to build instead of make. When running configure, the build directory must not be the same as the source directory, and must not be a parent directory. It must either be a subdirectory like build or an unrelated directory.

Note that the target for autotools must be specified explicitly when cross-compiling. Only lilium targets are supported. An error is issued for non-lilium kernels, and a warning is issued for non-standard environments.

All of the variables above can be set when building for makefile, and additionally can be configured for ./configure:

• CC, CXX, AS, AR, CFLAGS, CXXFLAGS, CPPFLAGS, ASFLAGS, and LDFLAGS can all be set as environment variables for ./configure
• --with-sysroot sets the default sysroot
• --enable-subsystems=list sets the subsystem wrapper libraries to build
  • --disable-subsystems disables all subsystems
• --enable-libraries sets the userspace libraries to build excluding subsystem wrapper libraries
  • --disable-libraries disables all userspace libraries and only builds subsystems
• --enable-shared/--disable-shared controls whether or not shared libraries and dynamic linking support should be built by default
• --enable-static/--disabale-static controls whether or not static libraries should be built by default: --enable-static=pic causes static libraries to be built with PIC enabled, even if shared libraries are disabled

License

Copyright (C) 2025 Lilium Mantainers

This software is dual licensed under the terms of the MIT and Apache 2.0 Licenses. You may use this software under the terms of the either License, at your option.

Unless you state otherwise, if you intentionally submit any contribution subject to copyright for inclusion in this repository, you agree to allow the mantainers to release that contribution under the above dual license, and with the following Public API Notice.

LiliumOS Public API notice

Note: The below does not apply to any public API which is defined by a standard authored by a 3rd party.

It is believed by the authors of this software that the Public API exposed by this software and which are intended to be useful to programs written and built against this software are not subject to copyright. In the event this assessment is wrong, the authors disclaim all copyright, to the greatest extent allowed by law, to the Public API and, to the extent that such copyright cannot be disclaimed, the Public API portions of this software are released under the following license, which you may use for those portions alone instead of the License for the software as a whole:

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted. THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

The Public API of a library includes the names and types of functions, structure fields, macros, and other definitions that are intended to be exposed publically, but does not include any intentionally private definitions (such as those in bits/ headers or most things prefixed with a reserved identifier that are not documented publically) or the source code used to provide the functionality of those interfaces.

The Above Notice shall not be taken to provide any license to any patent, whether or not held by the authors, that may apply to the Public API or to the implementation, including such parts of the implementation that are necessary to provide the functionality of the Public API.