TY - GEN A1 - Ramsauer, Ralf A1 - Bulwahn, Lukas A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - The Sound of Silence: Mining Security Vulnerabilities from Secret Integration Channels in Open-Source Projects T2 - MiniDebConf Regensburg (MDC) 2021 Y1 - 2021 UR - https://gemmei.ftp.acc.umu.se/pub/debian-meetings/2021/MiniDebConf-Regensburg/sound-of-silence.webm CY - Regensburg ER - TY - GEN A1 - Ramsauer, Ralf A1 - Kiszka, Jan A1 - Mauerer, Wolfgang T1 - Building Mixed Criticality Linux Systems with the Jailhouse Hypervisor T2 - Embedded Lunux Conference + OpenIoTSummit, Portland, OR, 21.-23.02.2017 N2 - The partitioning hypervisor Jaihouse allows us to run safety critical and uncritical applications in parallel on a single SoC. We present our experiences when porting a safety and real-time critical existing application as a Jailhouse guest. It shows a novel and promising approach for implementing mixed-criticality applications with real-time requirement while not loosing the benefits of Linux. This is done by static partitioning of hardware resources; guests do not interfere. We will present a multicopter platform running the real-time critical flight stack in an isolated Jailhouse guest. This proves the practicability of Jailhouse as well as the suitability for real-time safety critical systems by porting an existing application to a Jailhouse cell. We stress its concept and show up current hardware limitations, like undesired behaviour and present possible workarounds and solutions. Y1 - 2017 UR - https://www.youtube.com/watch?v=pvs0fv-gnvw ER - TY - GEN A1 - Ramsauer, Ralf A1 - Duda, Sebastian A1 - Bulwahn, Lukas A1 - Mauerer, Wolfgang T1 - The list is our process! An analysis of the kernel’s email-based development process T2 - Embedded Linux Conference Europe, Lyon 28.10.2019 Y1 - 2019 UR - https://elinux.org/images/0/09/Pasta-elce19.pdf ER - TY - GEN A1 - Ramsauer, Ralf A1 - Duda, Sebastian A1 - Mauerer, Wolfgang A1 - Bulwahn, Lukas T1 - The list is our process: An analysis of the kernel’s email-based development process T2 - Linux Plumbers Conference, Lisbon September 9, 2019 Y1 - 2019 UR - https://www.youtube.com/watch?v=QG1YDQ1HOKE ER - TY - GEN A1 - Ramsauer, Ralf A1 - Kiszka, Jan A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - Implementierung gemischt kritischer Systeme durch statische Hardwarepartitionierung T2 - Frühjahrstreffen der Fachgruppen Betriebssysteme, Hannover, 2. März 2018 Y1 - 2018 UR - https://www.betriebssysteme.org/wp-content/uploads/2018/04/fgbs18-169.pdf ER - TY - GEN A1 - Ramsauer, Ralf A1 - Kiszka, Jan A1 - Mauerer, Wolfgang T1 - Spectre and Meltdown vs. Real-Time: How Much do Mitigations Cost? T2 - Embedded Linux Conference Europe 2018, October 22 - 24, 2018, Edinburgh, UK Y1 - 2018 UR - https://www.youtube.com/watch?v=nqU4j2M_Ul4 ER - TY - GEN A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - Quantifying Upstream Integration with PaStA T2 - LTSI Workshop @ ELC17 Y1 - 2017 ER - TY - GEN A1 - Mintel, Mario A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Scherzinger, Stefanie A1 - Mauerer, Wolfgang T1 - Fork à la carte für In-Memory-Datenbanken T2 - Frühjahrstreffen der Fachgruppen Betriebssysteme, Hamburg, 17. März 2022 Y1 - 2022 UR - https://www.lfdr.de/Publications/2022/FGBS_Spring22_Mintel.pdf ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - The List is the Process: Reliable Pre-Integration Tracking of Commits on Mailing Lists T2 - 2019 IEEE/ACM 41st International Conference on Software Engineering (ICSE), 25-31 May 2019, Montreal, QC, Canada N2 - A considerable corpus of research on software evolution focuses on mining changes in software repositories, but omits their pre-integration history. We present a novel method for tracking this otherwise invisible evolution of software changes on mailing lists by connecting all early revisions of changes to their final version in repositories. Since artefact modifications on mailing lists are communicated by updates to fragments (i.e., patches) only, identifying semantically similar changes is a non-trivial task that our approach solves in a language-independent way. We evaluate our method on high-profile open source software (OSS) projects like the Linux kernel, and validate its high accuracy using an elaborately created ground truth. Our approach can be used to quantify properties of OSS development processes, which is an essential requirement for using OSS in reliable or safety-critical industrial products, where certifiability and conformance to processes are crucial. The high accuracy of our technique allows, to the best of our knowledge, for the first time to quantitatively determine if an open development process effectively aligns with given formal process requirements. KW - commits KW - Data mining KW - Electronic mail KW - Linux KW - mailing lists KW - mining software repositories KW - Open source software KW - patches KW - Software engineering KW - Software maintenance KW - Software reliability Y1 - 2019 U6 - https://doi.org/10.1109/ICSE.2019.00088 SP - 807 EP - 818 PB - IEEE ER - TY - CHAP A1 - Mauerer, Wolfgang A1 - Ramsauer, Ralf A1 - Lucas, Edson R. F. A1 - Scherzinger, Stefanie T1 - Silentium! Run-Analyse-Eradicate the Noise out of the DB/OS Stack T2 - Datenbanksysteme für Business, Technologie und Web (BTW 2021): 13.-17. September 2021, Dresden, Deutschland N2 - When multiple tenants compete for resources, database performance tends to suffer. Yet there are scenarios where guaranteed sub-millisecond latencies are crucial, such as in real-time data processing, IoT devices, or when operating in safety-critical environments. In this paper, we study how to make query latencies deterministic in the face of noise (whether caused by other tenants or unrelated operating system tasks). We perform controlled experiments with an in-memory database engine in a multi-tenant setting, where we successively eradicate noisy interference from within the system software stack, to the point where the engine runs close to bare-metal on the underlying hardware. We show that we can achieve query latencies comparable to the database engine running as the sole tenant, but without noticeably impacting the workload of competing tenants. We discuss these results in the context of ongoing efforts to build custom operating systems for database workloads, and point out that for certain use cases, the margin for improvement is rather narrow. In fact, for scenarios like ours, existing operating systems might just be good enough, provided that they are expertly configured. We then critically discuss these findings in the light of a broader family of database systems (e.g., including disk-based), and how to extend the approach of this paper accordingly. Low-latency databases; tail latency; real-time databases; bounded-time query processing; DB-OS co-engineering KW - bounded-time query processing KW - DB-OS co-engineering KW - Low-latency databases KW - real-time databases KW - tail latency Y1 - 2021 U6 - https://doi.org/10.18420/btw2021-21 SP - 397 EP - 421 PB - Gesellschaft für Informatik ER - TY - INPR A1 - Ramsauer, Ralf A1 - Huber, Stefan A1 - Schwarz, Konrad A1 - Kiszka, Jan A1 - Mauerer, Wolfgang T1 - Static Hardware Partitioning on RISC-V - Shortcomings, Limitations, and Prospects N2 - On embedded processors that are increasingly equipped with multiple CPU cores, static hardware partitioning is an established means of consolidating and isolating workloads onto single chips. This architectural pattern is suitable for mixed-criticality workloads that need to satisfy both, real-time and safety requirements, given suitable hardware properties. In this work, we focus on exploiting contemporary virtualisation mechanisms to achieve freedom from interference respectively isolation between workloads. Possibilities to achieve temporal and spatial isolation-while maintaining real-time capabilities-include statically partitioning resources, avoiding the sharing of devices, and ascertaining zero interventions of superordinate control structures. This eliminates overhead due to hardware partitioning, but implies certain hardware capabilities that are not yet fully implemented in contemporary standard systems. To address such hardware limitations, the customisable and configurable RISC-V instruction set architecture offers the possibility of swift, unrestricted modifications. We present findings on the current RISC-V specification and its implementations that necessitate interventions of superordinate control structures. We identify numerous issues adverse to implementing our goal of achieving zero interventions respectively zero overhead: On the design level, and especially with regards to handling interrupts. Based on micro-benchmark measurements, we discuss the implications of our findings, and argue how they can provide a basis for future extensions and improvements of the RISC-V architecture. Y1 - 2022 U6 - https://doi.org/10.48550/arXiv.2208.02703 ER - TY - CHAP A1 - Fruth, Michael A1 - Scherzinger, Stefanie A1 - Mauerer, Wolfgang A1 - Ramsauer, Ralf ED - Nambiar, Raghunath ED - Poess, Meikel T1 - Tell-Tale Tail Latencies: Pitfalls and Perils in Database Benchmarking T2 - Performance evaluation and benchmarking, 13th TPC Technology Conference (TPCTC 2021): Copenhagen, Denmark, August 20, 2021, Revised Selected Papers N2 - The performance of database systems is usually characterised by their average-case (i.e., throughput) behaviour in standardised or de-facto standard benchmarks like TPC-X or YCSB. While tails of the latency (i.e., response time) distribution receive considerably less attention, they have been identified as a threat to the overall system performance: In large-scale systems, even a fraction of requests delayed can build up into delays perceivable by end users. To eradicate large tail latencies from database systems, the ability to faithfully record them, and likewise pinpoint them to the root causes, is imminently required. In this paper, we address the challenge of measuring tail latencies using standard benchmarks, and identify subtle perils and pitfalls. In particular, we demonstrate how Java-based benchmarking approaches can substantially distort tail latency observations, and discuss how the discovery of such problems is inhibited by the common focus on throughput performance. We make a case for purposefully re-designing database benchmarking harnesses based on these observations to arrive at faithful characterisations of database performance from multiple important angles. KW - Benchmark harness KW - Database benchmarks KW - Tail latencies Y1 - 2022 SN - 9783030944377 U6 - https://doi.org/10.1007/978-3-030-94437-7_8 SP - 119 EP - 134 PB - Springer CY - Cham, Switzerland ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Kiszka, Jan A1 - Mauerer, Wolfgang ED - Keil, Sophia ED - Lasch, Rainer ED - Lindner, Fabian ED - Lohmer, Jacob T1 - A Novel Software Architecture for Mixed Criticality Systems T2 - Digital Transformation in Semiconductor Manufacturing: Proceedings of the 1st and 2nd European Advances in Digital Transformation Conference, EADTC 2018, Zittau, Germany and EADTC 2019, Milan, Italy N2 - The advent of multi-core CPUs in nearly all embedded markets has prompted an architectural trend towards combining safety critical and uncritical software on single hardware units. We present a novel architecture for mixed criticality systems based on Linux that allows us to consolidate critical and uncritical parts onto a single hardware unit. CPU virtualisation extensions enable strict and static partitioning of hardware by direct assignment of resources, which allows us to boot additional operating systems or bare metal applications running aside Linux. The hypervisor Jailhouse is at the core of the architecture and ensures that the resulting domains may serve workloads of different criticality and can not interfere in an unintended way. This retains Linux’s feature-richness in uncritical parts, while frugal safety and real-time critical applications execute in isolated domains. Architectural simplicity is a central aspect of our approach and a precondition for reliable implementability and successful certification. While standard virtualisation extensions provided by current hardware seem to suffice for a straight forward implementation of our approach, there are a number of further limitations that need to be worked around. This paper discusses the arising issues, and evaluates the suitability of our approach for real-world safety and real-time critical scenarios. Y1 - 2020 U6 - https://doi.org/10.1007/978-3-030-48602-0_11 SP - 121 EP - 128 PB - Springer International Publishing CY - Cham ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Kiszka, Jan A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - Look Mum, no VM Exits! (Almost) T2 - Proceedings of the 13th Annual Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT '17) N2 - Multi-core CPUs are a standard component in many modern embedded systems. Their virtualisation extensions enable the isolation of services, and gain popularity to implement mixed-criticality or otherwise split systems. We present Jailhouse, a Linux-based, OS-agnostic partitioning hypervisor that uses novel architectural approaches to combine Linux, a powerful general-purpose system, with strictly isolated special-purpose components. Our design goals favour simplicity over features, establish a minimal code base, and minimise hypervisor activity. Direct assignment of hardware to guests, together with a deferred initialisation scheme, offloads any complex hardware handling and bootstrapping issues from the hypervisor to the general purpose OS. The hypervisor establishes isolated domains that directly access physical resources without the need for emulation or paravirtualisation. This retains, with negligible system overhead, Linux's feature-richness in uncritical parts, while frugal safety and real-time critical workloads execute in isolated, safe domains. KW - FOS: Computer and information sciences KW - Operating Systems (cs.OS) Y1 - 2017 UR - https://ospert2017.uni.lu/ U6 - https://doi.org/10.48550/arXiv.1705.06932 ER - TY - CHAP A1 - Picha, Petr A1 - Brada, Premek A1 - Ramsauer, Ralf A1 - Mauerer, Wolfgang T1 - Towards Architect’s Activity Detection through a Common Model for Project Pattern Analysis T2 - First International Workshop on the Social and Organization Dimensions of Software, 5-7 April 2017, Gothenburg, Sweden N2 - Software development projects leave a large amount of data in repositories of Application Lifecycle Management (ALM) tools. These data contain detailed histories of their respective projects, their results and decisions made along the way. Analysis of such data helps uncover various interesting facts about projects, e.g. their socio-technical structures and the actual (vs. purported) roles of team members. Based on experiences with tools supporting our research we are convinced that it is feasible to consolidate data from different ALM tools, tapping into the situation common in real-life projects. In this paper we report on our work towards a shared common data model and tool integration aimed at improved project analysis. We discuss how this can help in the identification of architects in the project organizational structures, their activity patterns and collaboration with other team roles. KW - data analysis KW - Data Models KW - project management KW - Software Architecture KW - software tools KW - team working Y1 - 2017 U6 - https://doi.org/10.1109/ICSAW.2017.46 SP - 175 EP - 178 PB - IEEE ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang ED - Wassermann, Tony T1 - Observing Custom Software Modifications: A Quantitative Approach of Tracking the Evolution of Patch Stacks T2 - Proceedings of the 12th International Symposium on Open Collaboration (OpenSym '16) N2 - Modifications to open-source software (OSS) are often provided in the form of "patch stacks" -- sets of changes (patches) that modify a given body of source code. Maintaining patch stacks over extended periods of time is problematic when the underlying base project changes frequently. This necessitates a continuous and engineering-intensive adaptation of the stack. Nonetheless, long-term maintenance is an important problem for changes that are not integrated into projects, for instance when they are controversial or only of value to a limited group of users. We present and implement a methodology to systematically examine the temporal evolution of patch stacks, track non-functional properties like integrability and maintainability, and estimate the eventual economic and engineering effort required to successfully develop and maintain patch stacks. Our results provide a basis for quantitative research on patch stacks, including statistical analyses and other methods that lead to actionable advice on the construction and long-term maintenance of custom extensions to OSS. KW - CADOS KW - collaboration KW - Linux KW - maintenance KW - patch stacks Y1 - 2016 U6 - https://doi.org/10.1145/2957792.2957810 SP - 1 EP - 4 PB - ACM CY - New York ER - TY - VIDEO A1 - Mauerer, Wolfgang A1 - Ramsauer, Ralf T1 - Torturing Git for Fun and Profit T2 - Microsoft Developer Meetup Regensburg 02.04.2019 N2 - In diesem Talk blicken Prof. Dr. Wolfgang Mauerer und Ralf Ramsauer unter die Haube des verteilten Versionskontrollsystems Git. Neben einer genauen Beschreibung der Strukturen und Plumbing APIs, mit denen Git intern Commits erzeugt und verknüpft, gehen die Vortragenden auch auf nützliche Features und Standards ein, welche die Kollaborition in großen Open-Source Projekten erleichtern. Y1 - 2019 UR - https://www.youtube.com/watch?v=CrUwmO4tvLI ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Bulwahn, Lukas A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang ED - Zhang, Yinqian ED - Sion, Radu T1 - The Sound of Silence : Mining Security Vulnerabilities from Secret Integration Channels in Open-Source Projects T2 - Proceedings of the 2020 ACM SIGSAC Conference on Cloud Computing Security Workshop: 09.11.2020, virtual event N2 - Public development processes are a key characteristic of open source projects. However, fixes for vulnerabilities are usually discussed privately among a small group of trusted maintainers, and integrated without prior public involvement. This is supposed to prevent early disclosure, and cope with embargo and non-disclosure agreement (NDA) rules. While regular development activities leave publicly available traces, fixes for vulnerabilities that bypass the standard process do not. We present a data-mining based approach to detect code fragments that arise from such infringements of the standard process. By systematically mapping public development artefacts to source code repositories, we can exclude regular process activities, and infer irregularities that stem from non-public integration channels. For the Linux kernel, the most crucial component of many systems, we apply our method to a period of seven months before the release of Linux 5.4. We find 29 commits that address 12 vulnerabilities. For these vulnerabilities, our approach provides a temporal advantage of 2 to 179 days to design exploits before public disclosure takes place, and fixes are rolled out. Established responsible disclosure approaches in open development processes are supposed to limit premature visibility of security vulnerabilities. However, our approach shows that, instead, they open additional possibilities to uncover such changes that thwart the very premise. We conclude by discussing implications and partial countermeasures. Y1 - 2020 SN - 9781450380843 U6 - https://doi.org/10.1145/3411495.3421360 SP - 147 EP - 157 PB - ACM CY - New York, NY, USA ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - System Software for Manufacturing Systems T2 - Proc. First European Advances in Digital Transformation Conference, (2018) Y1 - 2018 ER - TY - THES A1 - Ramsauer, Ralf T1 - OSS Architecture for Mixed-Criticality Systems BT - A Dual View from a Software and System Engineering Perspective N2 - Computer-based automation in industrial appliances led to a growing number of logically dependent, but physically separated embedded control units per appliance. Many of those components are safety-critical systems, and require adherence to safety standards, which is inconsonant with the relentless demand for features in those appliances. Features lead to a growing amount of control units per appliance, and to a increasing complexity of the overall software stack, being unfavourable for safety certifications. Modern CPUs provide means to revise traditional separation of concerns design primitives: the consolidation of systems, which yields new engineering challenges that concern the entire software and system stack. Multi-core CPUs favour economic consolidation of formerly separated systems with one efficient single hardware unit. Nonetheless, the system architecture must provide means to guarantee the freedom from interference between domains of different criticality. System consolidation demands for architectural and engineering strategies to fulfil requirements (e.g., real-time or certifiability criteria) in safety-critical environments. In parallel, there is an ongoing trend to substitute ordinary proprietary base platform software components by mature OSS variants for economic and engineering reasons. There are fundamental differences of processual properties in development processes of OSS and proprietary software. OSS in safety-critical systems requires development process assessment techniques to build an evidence-based fundament for certification efforts that is based upon empirical software engineering methods. In this thesis, I will approach from both sides: the software and system engineering perspective. In the first part of this thesis, I focus on the assessment of OSS components: I develop software engineering techniques that allow to quantify characteristics of distributed OSS development processes. I show that ex-post analyses of software development processes can be used to serve as a foundation for certification efforts, as it is required for safety-critical systems. In the second part of this thesis, I present a system architecture based on OSS components that allows for consolidation of mixed-criticality systems on a single platform. Therefore, I exploit virtualisation extensions of modern CPUs to strictly isolate domains of different criticality. The proposed architecture shall eradicate any remaining hypervisor activity in order to preserve realtime capabilities of the hardware by design, while guaranteeing strict isolation across domains. KW - real-time operating system KW - mixed-criticality KW - static hardware partitioning KW - development processes KW - development process reconstruction KW - quantitative software engineering Y1 - 2021 UR - https://www.repo.uni-hannover.de/bitstream/handle/123456789/11815/Dissertation_Ramsauer-Ralf.pdf?sequence=3&isAllowed=y PB - Leibniz Universität Hannover ER - TY - CHAP A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang T1 - Reliable Pre-Integration Tracking of Commits on Mailing Lists T2 - Invited Talk at Safety Summit at Embedded Linux Conference Europe (ELCE18) Y1 - 2018 CY - Edinburgh, Scotland ER - TY - INPR A1 - Ramsauer, Ralf A1 - Mauerer, Wolfgang T1 - Towards System-Level Quantum-Accelerator Integration N2 - Quantum computers are often treated as experimental add-ons that are loosely coupled to classical infrastructure through high-level interpreted languages and cloud-like orchestration. However, future deployments in both, high-performance computing (HPC) and embedded environments, will demand tighter integration for lower latencies, stronger determinism, and architectural consistency, as well as to implement error correction and other tasks that require tight quantum-classical interaction as generically as possible. We propose a vertically integrated quantum systems architecture that treats quantum accelerators and processing units as peripheral system components. A central element is the Quantum Abstraction Layer (QAL) at operating system kernel level. It aims at real-time, low-latency, and high-throughput interaction between quantum and classical resources, as well as robust low-level quantum operations scheduling and generic resource management. It can serve as blueprint for orchestration of low-level computational components "around" a QPU (and inside a quantum computer), and across different modalities. We present first results towards such an integrated architecture, including a virtual QPU model based on QEMU. The architecture is validated through functional emulation on three base architectures (x86_64, ARM64, and RISC-V), and timing-accurate FPGA-based simulations. This allows for a realistic evaluation of hybrid system performance and quantum advantage scenarios. Our work lays the ground for a system-level co-design methodology tailored for the next generation of quantum-classical computing. Y1 - 2025 U6 - https://doi.org/10.48550/arXiv.2507.19212 ER - TY - CHAP A1 - Bielmeier, Benno A1 - Ramsauer, Ralf A1 - Yoshida, Takahiro A1 - Mauerer, Wolfgang T1 - From Tracepoints to Timeliness: a Semi-Markov Framework for Predictive Runtime Analysis T2 - IEEE 31th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA), 20-22 August 2025, Singapore N2 - Detecting and resolving violations of temporal constraints in real-time systems is both, time-consuming and resource-intensive, particularly in complex software environments. Measurement-based approaches are widely used during development, but often are unable to deliver reliable predictions with limited data. This paper presents a hybrid method for worst-case execution time estimation, combining lightweight runtime tracing with probabilistic modelling. Timestamped system events are used to construct a semi-Markov chain, where transitions represent empirically observed timing between events. Execution duration is interpreted as time-to-absorption in the semi-Markov chain, enabling worst-case execution time estimation with fewer assumptions and reduced overhead. Empirical results from real-time Linux systems indicate that the method captures both regular and extreme timing behaviours accurately, even from short observation periods. The model supports holistic, low-intrusion analysis across system layers and remains interpretable and adaptable for practical use. Y1 - 2025 U6 - https://doi.org/10.1109/RTCSA66114.2025.00021 SP - 114 EP - 125 PB - IEEE ER - TY - JOUR A1 - Feilner, Markus A1 - Ramsauer, Ralf T1 - Open-Source-Wissenschaftler bereiten Software für das Quantencomputing vor JF - Linux-Magazin N2 - Um Software und Architekturen für das Quantencomputing zu entwickeln, zu definieren und zu testen, braucht man keinen Quantencomputer. Weil die teuer und rar sind, entschieden sich Wissenschaftler der OTH Regensburg dafür, sie einfach zu virtualisieren – mit messbarem Erfolg. KW - Linux KW - Quantencomputing KW - QuantumVM Y1 - 2025 UR - https://www.linux-magazin.de/ausgaben/2025/08/quantencomputing/ VL - 25 IS - 08 PB - Deloitte ER -