L4Re

L4 Runtime Environment (L4Re) is a software platform for the L4 family of microkernels. It provides a user-space runtime that runs on top of a microkernel, offering a collection of services and servers that enable a flexible, modular operating system without a monolithic kernel. L4Re is used in embedded systems, research projects, and teaching environments to explore component-based OS design and systems architecture.

Architecture and components: L4Re adopts a component-based architecture in which core operating system services run as user-space servers. It provides facilities for memory management, interprocess communication, scheduling, and capability handling, along with device drivers, filesystems, networking, time services, and virtualization support. A component loader and interface libraries support dynamic composition and hot-swapping of modules, while security is based on capabilities and isolation between components. L4Re is designed to be portable across several L4 microkernel implementations and hardware architectures.

Development and usage: L4Re supplies tools and libraries for developing and deploying components, including runtime support for C and C++ code. It enables running multiple isolated servers in user space and can host virtualized guests or separate user environments. The environment emphasizes small trusted kernels with a modular user-space layer, making it suitable for research, education, and embedded deployments.

Applications and scope: L4Re is used for experiments with microkernel designs, real-time systems, and teaching platforms that demonstrate component-based OS principles. It is available as open-source software and has been applied on various L4-based platforms and architectures, reflecting its role as a flexible, portable runtime environment for microkernel research and development.