Future Challenges of the Genode project

This document compiles various ideas to pursue in the context of Genode. It is meant as source of inspiration for individuals who are interested in getting involved with the project and for students who want to base their student research projects on Genode.

Applications and library infrastructure

GNU Privacy Guard

The GNU Privacy Guard (GNUPG) is the most widely used Free-Software implementation of the OpenGPG standard. It comprises a rich set of tools for encryption and key management. For many forthcoming application scenarios of Genode such as package management and email communication, GNUPG is crucial. Hence, it should be ported to Genode. Such a port may leverage Genode's fine-grained component architecture to strongly separate network-exposed functionality, the storage of key material, and the cryptographic functions.

VNC server implementing Genode's framebuffer session interface

With Input and Framebuffer, Genode provides two low-level interfaces used by interactive applications. For example, the Nitpicker GUI server uses these interfaces as a client and, in turn, exports multiple virtual Framebuffer and Input interfaces to its clients. This enables a highly modular use of applications such as the nesting of GUIs. By implementing the Framebuffer and Input interfaces with a VNC server implementation, all graphical workloads of Genode would become available over the network. One immediate application of this implementation is the remote testing of graphical Genode applications running on a headless server.

Interfacing with the SAFE network

The SAFE network is an attempt to fix many shortcomings of the internet - in particular with respect to privacy and freedom - at an architectural level. It is a peer-to-peer communication and storage network that does not depend on single point of failure or control. It is intriguing to explore the opportunity of integrating support for the SAFE network not merely as an application but integrated in the operating system, i.e., in the form of Genode components or a set of Genode VFS plugins.

Tiled window manager

At Genode Labs, we pursue the goal to shape Genode into an general-purpose operating system suitable for productive work. The feature set needed to achieve this goal largely depends on the tools and applications daily used by the Genode engineers. As one particularly important tool for being highly productive, we identified a tiled user interface. Currently, all developers at Genode Labs embrace either the Ion3 window manager or the tiled Terminator terminal emulator. Hence, we desire to have a similar mode of user interaction on Genode as well. The goal of this challenge is to identify the most important usage patters and the implementation of a tiled GUI that multiplexes the framebuffer into a set of tiled and tabbed virtual framebuffers.

Related to this work, the low-level Framebuffer and Input interfaces should be subject to a revision, for example for enabling the flexible change of framebuffer sizes as needed by a tiled user interface.

Interactive sound switchbox based on Genode's Audio_out session interface

Since version 10.05, Genode features a highly flexible configuration concept that allows the arbitrary routing of session requests throughout the hierarchic process structure. Even though primarily designed for expressing mandatory-access control rules, the concept scales far beyond this use case. For example, it can be used to run an arbitrary number of processes implementing the same interface and connecting the different interface implementations. One special case of this scenario is a chain of audio filters with each using the Audio_out session interface for both roles client and server. Combined with the Nitpicker GUI server and Genode's support for real-time priorities, this base techniques enable the creation of flexible audio mixer / switchboard applications, which require dedicated frameworks (e.g., Jack audio) on traditional operating systems. The goal of this project is to create a showcase implementation demonstrating the feasibility for creating high-quality audio applications on Genode. Furthermore, we wish for feedback regarding the current design of our bulk streaming interface when used for low-latency applications.

Graphical on-target IPC tracing tool using Qt

Analysing the interaction of components of a multi-server operating system such as Genode is important to discover bottlenecks of the system and for debugging highly complex usage scenarios involving many processes. Currently, Genode handles this problem with two approaches. First, Genode's recursive structure enables the integration of a subsystem in a basic OS setup featuring only those drivers and components used for the particular subsystem. After the successful integration of such a subsystem, it can be embedded into a far more complex application scenario without any changes. With this approach, the subject to analyse can be kept at a reasonable level at integration time. For debugging purposes, the current approach is using the debugging facilities of the respective base platforms (e.g., using GDB on Linux, the Fiasco kernel debugger, the OKL4 kernel debugger).

However, in many cases, bottlenecks do not occur when integrating individual sub systems but after integrating multiple of such subsystems into a large application scenario. For such scenarios, existing debugging methodologies do not scale. A tool is desired that is able to capture the relationships between processes of a potentially large process hierarchy, to display communication and control flows between those processes, and to visualize the interaction of threads with the kernel's scheduler.

Since Qt is available natively on Genode, the creation of both offline and on-target analysis tools has become feasible. The first step of this project is creating an interactive on-target tool, that displays the interaction of communicating threads as captured on the running system. The tool should work on a selected kernel that provides a facility for tracing IPC messages.

Ports of popular software

Genode features a ports mechanism to cleanly integrate 3rd-party software. Thanks to the C runtime, the flexible per-component VFS, the standard C++ library, and the Noux runtime (for UNIX software), porting software to Genode is relatively straight forward. The porting guide explains the typical steps. A wish list of software that we'd like to have available on Genode is available at http://usr.sysret.de/jws/genode/porting_wishlist.html.

Application frameworks and runtime environments

OpenJDK

OpenJDK is the reference implementation of the Java programming language and hosts an enormous ecosystem of application software. The goal of this line of work is the ability to run this software directly on Genode. The centerpiece of OpenJDK is Hotspot - the Java virtual machine implementation, which must be ported to Genode. The initial port should suffice to execute simple example programs that operate on textual input. Since Genode has the FreeBSD libc readily available, OpenJDK's existing POSIX backends can be reused. The next step is the creation of Genode-specific native classes that bridge the gap between the Java world and Genode, in particular the glue code to run graphical applications as clients of Genode's GUI server. Since OpenJDK has been ported to numerous platforms (such as Haiku), there exists a comforting number of implementations that can be taken as reference.

Android's ART VM natively on Genode

ART is a Java virtual machine that is used for executing applications on Android. By running ART directly on Genode, the Linux kernel could be removed from the trusted computing base of Android, facilitating the use of this mobile OS in high-assurance settings.

Rust bindings for the Genode API

Rust is a low-level systems programming language that ensures memory safety without employing a garbage collector. It thereby challenges C++ as the go-to programming language for high-performance and low-level code. Since version 16.05, Genode supports the use of the Rust programming language within components. However, to unleash the potential of this combination, Genode's API must become available to native Rust code. The intermediate goal of this project is the implementation of an example server, e.g., a component that provides a terminal-session interface. Thereby, we will encounter the problems of bootstrapping and configuration of the component, the provisioning of signal handlers and session objects, and memory management.

Go language runtime

Go is a popular language in particular for web applications. In the past, there were numerous attempts to make the Go runtime available on Genode but so far, none of those undertakings have landed in the official Genode source tree. To goal of this project is the hosting of Go-written applications - in particular networking applications - as Genode components. The topic comprises work on the tool-chain and build-system integration, the porting the runtime libraries, and the glue between the Go and Genode environments.

Combination of CAmkES with Genode

CAmkES is a component framework for seL4. In contrast to Genode, which is a dynamic system, CAmkES-based systems are defined at design time and remain fixed at runtime. Hence, CAmkES and Genode can be seen as the opposite ends of component-based used-land architectures. The goal of this project is to build a bridge between both projects with the potential to cross-pollinate the respective communities. Among the principal approaches are embedding of a single CAmkES component as a Genode component (e.g., an individual device driver), the hosting of a dynamic Genode system as a component within a CAmkES system, or the hosting of a CAmkES system composition as a Genode subsystem.

Runtime for the D programming language

The D systems programming language was designed to overcome many gripes that exists with C++. In particular, it introduces a sane syntax for meta programming, supports unit tests, and contract-based programming. These features make D a compelling language to explore when implementing OS components. Even though D is a compiled language, it comes with a runtime providing support for exception handling and garbage collection. The goal of the project is to explore the use of D for Genode programs, porting the runtime to Genode, adapting the Genode build system to accommodate D programs, and interfacing D programs with other Genode components written in C++.

Using Haskell as systems-development language

The goal of this project is the application of functional programming i.e., Haskell, for the implementation of low-level Genode components. Implementing critical functionalities in such a high-level language instead of a classical systems language such as C or C++ would pave the way towards analyzing such components with formal methods.

The use of Haskell for systems development was pioneered by the House Project. A more recent development is HalVM - a light-weight OS runtime for Xen that is based on Haskell.

Virtualization

VirtualBox on top of KVM on Linux

Genode's version of VirtualBox replaces the original in-kernel VirtualBox hypervisor by the virtualization mechanism of the NOVA hypervisor or the Muen separation kernel. Those mechanisms look very similar the KVM interface of the Linux kernel. It should in principle be possible to re-target Genode's version of VirtualBox to KVM. This way, VirtualBox and Qemu/KVM-based virtual machines could co-exist on the same system, which is normally not possible. Also, complex Genode scenarios (like Turmvilla) could be prototyped on GNU/Linux.

VirtualBox on top of seL4

The seL4 microkernel is a modern microkernel that undergoes formal verification to prove the absence of bugs. Since version 4.0, the kernel supports virtualization support on x86-based hardware. Genode has experimental support for seL4 that allows almost all Genode components to be used on top of this kernel. VirtualBox is an exception because it closely interacts with the underlying kernel (like NOVA) to attain good performance. We have shown that VirtualBox can be executed within a protection domain of the NOVA microhypervisor. The goal of this project is the application of this approach to the virtualization interface of seL4. The result will be a VM hosting environment that ensures the separation of virtual machines via the formally verified seL4 kernel.

Xen as kernel for Genode

Using Xen as kernel for Genode would clear the way to remove the overly complex Linux OS from the trusted computing base of Xen guests OSes.

Xen is a hypervisor that can host multiple virtual machines on one physical machine. For driving physical devices and for virtual-machine management, Xen relies on a privileged guest OS called Dom0. Currently, Linux is the predominant choice to be used as Dom0, which implicates a trusted computing base of millions of lines of code for the other guest OSes.

Even though Xen was designed as hypervisor, a thorough analysis done by Julian Stecklina concludes that Xen qualifies well as a kernel for Genode. For example, Julian implemented a version of Genode's IPC framework that utilizes Xen's communication mechanisms (event channels and shared memory).

Genode as virtualization layer for Qubes OS

Qubes OS is a desktop operating system that follows the principle of security through compartmentalization. In spirit, it is closely related to Genode. In contrast Genode's clean-slate approach of building a fine-grained multi-component system, Qubes employs Xen-based virtual machines as sandboxing mechanism. In version 3.0, Qubes introduced a Hypervisor Abstraction Layer, which decouples Qubes from the underlying virtualization platform. This exploration project pursues the goal of replacing Xen by Genode as virtualization layer for Qubes.

Qemu

As we use Qemu as primary testing platform for most of the kernels, a port of Qemu to Genode is needed in order to move our regular work flows to Genode as development platform. The basic prerequisites namely libSDL and a C runtime are already available such that this porting work seems to be feasible. In our context, the ia32, amd64, and ARM platforms are of most interest. Note that the project does not have the immediate goal of using hardware-based virtualization. However, if there is interest, the project bears the opportunity to explore the provisioning of the KVM interface based on Genode's VFS plugin concept.

Device drivers

Isochronous USB devices

Genode's USB driver supports bulk and interrupt endpoints. Thereby, most USB devices like USB storage, user input, printers, and networking devices can be used. However, multi-media devices such as cameras or audio equipment use isochronous endpoints, which are not supported. The goal of this line of work is the support of these devices in Genode. The topic touches the USB driver, the USB session interface, an example implementation of a USB client driver (using the session interface) for a device of choice, and - potentially - the enhancement of Genode's USB-pass-through mechanism for VirtualBox.

Sound on the Raspberry Pi

The goal of this project is a component that uses the Raspberry Pi's PWM device to implement Genode's audio-out-session interface. Since Genode's version of libSDL already supports this interface as audio backend, the new driver will make the sound of all SDL-based games available on the Raspberry Pi.

Framebuffer for UEFI and Coreboot

By moving away from the legacy BIOS boot mechanism, it is time to reconsider closely related traditional approaches such as the use of the VESA BIOS extensions for accessing the frame buffer. On UEFI or Coreboot systems, there exist alternative ways to initialize and access the framebuffer in a hardware-independent way. On the course of this project, we will explore the available options and create dedicated Genode driver components that use the modern mechanisms. For reference, the current state of Genode's UEFI support is documented in Issue 2242.

Data Plane Development Kit (DPDK)

Genode utilizes the network device drivers of the iPXE project, which perform reasonably well for everyday use cases but are obviously not designated for high-performance networking. The DPDK is a vendor-supported suite of network device drivers that is specifically developed for high-performance applications. It presents an attractive alternative to iPXE-based drivers. This project has the goal to make DPDK drivers available as a Genode component.

Platforms

Microkernelizing Linux

Thanks to Genode's generic interfaces for I/O access as provided by core, all Genode device drivers including drivers ported from Linux and gPXE can be executed as user-level components on all supported microkernels. However, so far, we have not enabled the use of these device drivers on Linux as base platform. The goal of this project is the systematic replacement of in-kernel Linux device drivers by Genode processes running in user space, effectively reducing the Linux kernel to a runtime for Genode's core process. But moving drivers to Genode processes is just the beginning. By employing further Genode functionality such as its native GUI, lwIP, and Noux, many protocol stacks can effectively be removed from the Linux kernel.

The goal of this project is to evaluate how small the Linux kernel can get when used as a microkernel.

Support for the HelenOS/SPARTAN kernel

HelenOS is a microkernel-based multi-server OS developed at the university of Prague. It is based on the SPARTAN microkernel, which runs on a wide variety of CPU architectures including Sparc, MIPS, and PowerPC. This broad platform support makes SPARTAN an interesting kernel to look at alone. But a further motivation is the fact that SPARTAN does not follow the classical L4 road, providing a kernel API that comes with an own terminology and different kernel primitives. This makes the mapping of SPARTAN's kernel API to Genode a challenging endeavour and would provide us with feedback regarding the universality of Genode's internal interfaces. Finally, this project has the potential to ignite a further collaboration between the HelenOS and Genode communities.

Support for the XNU kernel (Darwin)

XNU is the kernel used by Darwin and Mac OS X. It is derived from the MACH microkernel and extended with a UNIX-like syscall API. Because the kernel is used for Mac OS X, it could represent an industry-strength base platform for Genode supporting all CPU features as used by Mac OS X.

Linux process containers for supporting Genode`s resource trading

Even though the Linux version of Genode is primarily meant as a development platform, there exist interesting opportunities to explore when combining Genode with Linux, in particular Linux' process containers. Linux process containers provide a mechanism to partition physical resources, foremost CPU time, between Linux processes. This raises the interesting question of whether this mechanism could be used for a proper implementation of Genode's resource trading on Linux. Process containers introduction...

Optimizations

Low-latency audio streaming

Genode comes with an audio streaming interface called Audio_out session. It is based on a shared-memory packet stream accompanied with asynchronous data-flow signals. For real-time audio processing involving chains of Genode components, streams of audio data must be carried at low latency, imposing constraints to buffer sizes and the modes of operation of the audio mixer and audio drivers. The goal of this project is to create a holistic design of the whole chain of audio processing, taking thread-scheduling into account. A particular challenge is the mixed output of real-time (small buffer, low latency) and non-real-time (larger buffer to compensate jitter, higher latency) audio sources.

De-privileging the VESA graphics driver

The VESA graphics driver executes the graphics initialization code provided by the graphics card via an x86 emulator. To initialize a graphics mode, this code needs to access device hardware. Currently, we permit access to all device registers requested by the graphics-card's code. These devices include the system timer, the PCI configuration registers, and the interrupt controller, which are critical for the proper operating of the kernel. The goal of this work is to restrict the permissions of the VESA driver to a minimum by virtualizing all devices but the actual graphics card.