arXiv subjects

Christoph Lüth

Publications and source records attributed to Christoph Lüth.

6 recordsLinked to original sources

arXiv2025

Accurate and Extensible Symbolic Execution of Binary Code based on Formal ISA Semantics

Symbolic execution is an SMT-based software verification and testing technique. Symbolic execution requires tracking performed computations during software simulation to reason about branches in the software under test. The prevailing approach on symbolic execution of binary code tracks computations by transforming the code to be tested to an architecture-independent IR and then symbolically executes this IR. However, the resulting IR must be semantically equivalent to the binary code, making this process complex and error-prone. The semantics of the binary code are specified by the targeted ISA, commonly given in natural language and requiring a manual implementation of the transformation to an IR. In recent years, the use of formal languages to describe ISA semantics in a machine-readable way has gained increased popularity. We investigate the utilization of such formal semantics for symbolic execution of binary code, achieving an accurate representation of instruction semantics. We present a prototype for the RISC-V ISA and conduct a case study to demonstrate that it can be easily extended to additional instructions. Furthermore, we perform an experimental comparison with prior work which resulted in the discovery of five previously unknown bugs in the ISA implementation of the popular IR-based symbolic executor angr.

cs.SE↗

arXiv2024

How Deduction Systems Can Help You To Verify Stability Properties

Mathematical proofs are a cornerstone of control theory, and it is important to get them right. Deduction systems can help with this by mechanically checking the proofs. However, the structure and level of detail at which a proof is represented in a deduction system differ significantly from a proof read and written by mathematicians and engineers, hampering understanding and adoption of these systems. This paper aims at helping to bridge the gap between machine-checked proofs and proofs in engineering and mathematics by presenting a machine-checked proof for stability using Lyapunov's theorem in a human-readable way. The structure of the proof is analyzed in detail, and potential benefits of such a proof are discussed, such as generalizability, reusability and increased trust in correctness.

eess.SY↗

arXiv2023

Deriving Rewards for Reinforcement Learning from Symbolic Behaviour Descriptions of Bipedal Walking

Generating physical movement behaviours from their symbolic description is a long-standing challenge in artificial intelligence (AI) and robotics, requiring insights into numerical optimization methods as well as into formalizations from symbolic AI and reasoning. In this paper, a novel approach to finding a reward function from a symbolic description is proposed. The intended system behaviour is modelled as a hybrid automaton, which reduces the system state space to allow more efficient reinforcement learning. The approach is applied to bipedal walking, by modelling the walking robot as a hybrid automaton over state space orthants, and used with the compass walker to derive a reward that incentivizes following the hybrid automaton cycle. As a result, training times of reinforcement learning controllers are reduced while final walking speed is increased. The approach can serve as a blueprint how to generate reward functions from symbolic AI and reasoning.

cs.RO↗

arXiv2022

Analytic Estimation of Region of Attraction of an LQR Controller for Torque Limited Simple Pendulum

Linear-quadratic regulators (LQR) are a well known and widely used tool in control theory for both linear and nonlinear dynamics. For nonlinear problems, an LQR-based controller is usually only locally viable, thus, raising the problem of estimating the region of attraction (ROA). The need for good ROA estimations becomes especially pressing for underactuated systems, as a failure of controls might lead to unsafe and unrecoverable system states. Known approaches based on optimization or sampling, while working well, might be too slow in time critical applications and are hard to verify formally. In this work, we propose a novel approach to estimate the ROA based on the analytic solutions to linear ODEs for the torque limited simple pendulum. In simulation and physical experiments, we compared our approach to a Lyapunov-sampling baseline approach and found that our approach was faster to compute, while yielding ROA estimations of similar phase space area.

cs.RO↗

arXiv2017

Interactive Proof Presentations with Cobra

We present Cobra, a modern proof presentation framework, leveraging cutting-edge presentation technology together with a state of the art interactive theorem prover to present formalized mathematics as active documents. Cobra provides both an easy way to present proofs and a novel approach to auditorium interaction. The presentation is checked live by the theorem prover, and moreover allows for live changes both by the presenter and the audience.

cs.LO↗

arXiv2013

Proceedings 10th International Workshop On User Interfaces for Theorem Provers

This EPTCS volume collects the post-proceedings of the 10th International Workshop On User Interfaces for Theorem Provers (UITP 2012), held as part of the Conferences on Intelligent Computer Mathematics (CICM 2012) in Bremen on July 11th 2012. The UITP workshop series aims at bringing together reasearchers interested in designing, developing and evaluating interfaces for interactive proof systems, such as theorem provers, formal method tools, and other tools manipulating and presenting mathematical formulae. Started in 1995, it can look back on seventeen years of history by now. The papers in the present volume give a good indication of the range of questions currently addressed in the UITP community; this ranges from interface design (Windsteiger; Dunchev et al) to using technologies such as machine learning to assist the user (Komendantskaya et al). The web features prominently (Tankink), and new technology necessitates changes right down to the very basic modes of interaction (Wenzel) - the old REPL (read, evaluate, print, loop) mode of interaction can not take advantage of modern technology, such as the web and multi-core machines.

cs.LO↗