XtratuM is a bare-metal

hypervisor A hypervisor, also known as a virtual machine monitor (VMM) or virtualizer, is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called ...

specially designed for embedded

real-time Real-time, realtime, or real time may refer to: Computing * Real-time computing, hardware and software systems subject to a specified time constraint * Real-time clock, a computer clock that keeps track of the current time * Real-time Control Syst ...

systems available for the

instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...

s LEON2/3/4 ( SPARC v8),

ARM In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between ...

v7 and V8 processors (TMS570, R5, A9, A52, A53) and RISC-V processor. It was initially developed by the

Universidad Politécnica de Valencia The Polytechnic University of Valencia (; , ), shortened to UPV, is a Spanish university located in Valencia, with a focus on science, technology, and arts. It was founded in 1968 as the Higher Polytechnic School of Valencia and became a univers ...

(Spain). XtratuM was released as

free and open-source software Free and open-source software (FOSS) is software available under a license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term encompassing free ...

, subject to the requirements of the

GNU General Public License The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first ...

(GPL), version 2 or any later. A new version of XtratuM from scratch (XtratuM New Generation XNG) is commercialized b
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under a proprietary license. It has been qualified for critical systems. XtratuM is a hypervisor designed for embedded systems to meet safety critical real-time requirements. It provides a framework to run several

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s (or real-time executives) in a robust partitioned environment. XtratuM can be used to build a MILS (Multiple Independent Levels of Security) architecture.

History

The name XtratuM derives from the word

stratum In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ...

. In geology and related fields it means: :Layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. In order to stress the tight relation with Linux and the open-source movements, the “S” was replaced by “X”. XtratuM would be the first layer of software (the one closest to the hardware), which provides a solid basis for the rest of the system. XtratuM 1.0 was initially designed as a substitution of the

RTLinux RTLinux is a hard realtime real-time operating system (RTOS) microkernel that runs the entire Linux operating system as a fully preemptive process. The hard real-time property makes it possible to control robots, data acquisition systems, man ...

HAL (

Hardware Abstraction Layer Hardware abstractions are sets of routines in software that provide programs with access to hardware resources through programming interfaces. The programming interface allows all devices in a particular class ''C'' of hardware devices to be acc ...

) to meet temporal and spatial partitioning requirements. The goal was to virtualize the essential hardware devices to execute several OSes concurrently, with at least one of these OSes being a RTOS. The other hardware devices (including booting) were left to a special domain, named root domain. After this experience, it was redesigned to be independent of Linux and bootable. The result of this is XtratuM 2.0 which is type 1 hypervisor that uses para-virtualization. The para-virtualized operations are as close to the hardware as possible. Therefore, porting an operating system that already works on the native system is a simple task: replace some parts of the operating system HAL with the corresponding hypercalls.

Overview

The design of a

for critical

embedded system An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is e ...

s follows these criteria: * Strong temporal isolation: fixed cyclic scheduler. * Strong spatial isolation: all partitions are executed in processor user mode, and do not share memory. * Basic resource virtualization: clock and timers, interrupts, memory,

CPU A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, log ...

and special devices. * Real-time scheduling policy for partition scheduling. * Efficient context switch for partitions. * Deterministic hypercalls (hypervisor system calls). * Health monitoring support. * Robust and efficient inter-partition communication mechanisms (sampling and queuing ports). * Low overhead. * Small size. * Static system definition via configuration file (XML). In the case of embedded systems, particularly avionics systems, the

ARINC 653 ARINC 653 (Avionics Application Software Standard Interface) is a software specification for space and time partitioning in safety-critical avionics real-time operating systems (RTOS). It allows the hosting of multiple applications of different s ...

standard defines a partitioning scheme. Although this standard was not designed to describe how a hypervisor must operate, some parts of the model are quite close to the functionality provided by a hypervisor. The XtratuM API and internal operations resemble the

standard. XtratuM is not an

compliant system. The standard relies on the idea of a

separation kernel A separation kernel is a type of security kernel used to simulate a distributed environment. The concept was introduced by John Rushby in a 1981 paper.John Rushby, "The Design and Verification of Secure Systems," Eighth ACM Symposium on Operating ...

defining both the API and operations of the partitions and also how the threads or processes are managed inside each partition. XtratuM hypervisor supports the LEON 2/LEON 3/LEON 4 ( SPARCv8) and Cortex R4/Cortex R5/Cortex A9 (ARMv7) architectures. XtratuM support as execution environments: * XAL (XtratuM Abstraction Layer) for bare-C applications * POSIX PSE51 Partikle RTOS * ARINC-653 P1 compliant LITHOS RTOS * ARINC-653 P4 compliant uLITHOS runtime * Ada Ravenscar profile ORK+ *

RTEMS Real-Time Executive for Multiprocessor Systems (RTEMS), formerly Real-Time Executive for Missile Systems, and then Real-Time Executive for Military Systems, is a real-time operating system (RTOS) designed for embedded systems. It is free and open ...

* Linux

References

External links

XtratuM Official Page

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{{Virtualization software Free virtualization software Virtualization software for Linux

History

Overview

See also

References

External links