Commercial off-the-shelf (COTS) microcontrollers can be useful for non-critical processing on spaceborne platforms. Many of these microprocessors are inexpensive and consume little power. However, the software running on these processors is vulnerable to radiation upsets, which can cause unpredictable program execution or corrupt data. Space missions cannot allow these errors to interrupt functionality or destroy gathered data. As a result, several techniques have been developed to reduce the effect of these upsets. Some proposed techniques involve altering the processor hardware, which is impossible for a COTS device. Alternately, the software running on the microcontroller can be modified to detect or correct data corruption. There have been several proposed approaches for software mitigation. Some take advantage of advanced architectural features, others modify software by hand, and still others focus their techniques on specific microarchitectures. However, these approaches do not consider the limited resources of microcontrollers and are difficult to use across multiple platforms. This thesis explores fully automated software-based mitigation to improve the reliability of microcontrollers and microcontroller software in a high radiation environment. Several difficulties associated with automating software protection in the compilation step are also discussed. Previous mitigation techniques are examined, resulting in the creation of COAST (COmpiler-Assisted Software fault Tolerance), a tool that automatically applies software protection techniques to user code. Hardened code has been verified by a fault injection campaign; the mean work to failure increased, on average, by 21.6x. When tested in a neutron beam, the neutron cross sections of programs decreased by an average of 23x, and the average mean work to failure increased by 5.7x.

Dans cette thèse, nous décrivons la conception et l'implémentation d'une plate-forme logicielle de spéculation de threads, ou fils d'exécution, appelée VMAD, pour "Virtual Machine for Advanced Dynamic analysis and transformation", et dont la fonction principale est d'être capable de paralléliser de manière spéculative un nid de boucles séquentiel de différentes façons, en ré-ordonnançant ses itérations. La transformation à appliquer est sélectionnée au cours de l'exécution avec pour objectifs de minimiser le nombre de retours arrières et de maximiser la performance. Nous effectuons des transformations de code en appliquant le modèle polyédrique que nous avons adapté à la parallélisation spéculative au cours de l'exécution. Pour cela, nous construisons au préalable un patron de code qui est "patché" par notre "runtime", ou support d'exécution logiciel, selon des informations de profilage collectées sur des échantillons du temps d'exécution. L'adaptabilité est assurée en considérant des tranches de code de tailles différentes, qui sont exécutées successivement, chacune étant parallélisée différemment, ou exécutée en séquentiel, selon le comportement des accès à la mémoire observé. Nous montrons, sur plusieurs programmes que notre plate-forme offre de bonnes performances, pour des codes qui n'auraient pas pu être traités efficacement par les systèmes spéculatifs de threads proposés précédemment. / In this thesis, we present a Thread-Level Speculation (TLS) framework whose main feature is to speculatively parallelize a sequential loop nest in various ways, to maximize performance. We perform code transformations by applying the polyhedral model that we adapted for speculative and runtime code parallelization. For this purpose, we designed a parallel code pattern which is patched by our runtime system according to the profiling information collected on some execution samples. We show on several benchmarks that our framework yields good performance on codes which could not be handled efficiently by previously proposed TLS systems.

Decompilation or reverse compilation is the process of translating low-level machine-readable code into high-level human-readable code. The problem is non-trivial due to the amount of information lost during compilation, but it can be divided into several smaller problems which may be solved independently. This report explores the feasibility of composing a decompilation pipeline from independent components, and the potential of exposing those components to the end-user. The components of the decompilation pipeline are conceptually grouped into three modules. Firstly, the front-end translates a source language (e.g. x86 assembly) into LLVM IR; a platform-independent low-level intermediate representation. Secondly, the middle-end structures the LLVM IR by identifying high-level control flow primitives (e.g. pre-test loops, 2-way conditionals). Lastly, the back-end translates the structured LLVM IR into a high-level target programming language (e.g. Go). The control flow analysis stage of the middle-end uses subgraph isomorphism search algorithms to locate control flow primitives in CFGs, both of which are described using Graphviz DOT files. The decompilation pipeline has been proven capable of recovering nested pre-test and post-test loops (e.g. while, do-while), and 1-way and 2-way conditionals (e.g. if, if-else) from LLVM IR. Furthermore, the data-driven design of the control flow analysis stage facilitates extensions to identify new control flow primitives. There is huge potential for future development. The Go output could be made more idiomatic by extending the post-processing stage, using components such as Grind by Russ Cox which moves variable declarations closer to their usage. The language-agnostic aspects of the design will be validated by implementing components in other languages; e.g. data flow analysis in Haskell. Additional back-ends (e.g. Python output) will be implemented to verify that the general decompilation tasks (e.g. control flow analysis, data flow analysis) are handled by the middle-end. / <p>BSc dissertation written during an ERASMUS exchange from Uppsala University to the University of Portsmouth.</p>

This work discusses about CodAl language and Codasip framework. It describes LLVM compiling platform, LLVM IR and its possible optimizations. The result of this work is creation and implementation a proposal of global scheduling dependence on profile as extension in LLVM.

This thesis concerns the issue of completness detection of instruction set description for the LLVM compiler, or the ability of a compiler to generate target program for every valid source program in the appropriate high-level programming language. On the basis of regular tree grammar theory and several scietific theses that also concern this issue, formal tool for inclusion checking of two grammars. Furthermore a method for automatic extraction of the two grammars from the instruction set description has been devised, as a result of which the tool can be used for checking completeness of instruction selection. In combination with checking completeness of the legalization process of the LLVM compiler, which preceeds the instruction selection, it should be feaseable to check completeness of most compiler parts dependent on the target architecture.

Presented is implementation of algorithm for alias analysis, which was integrated into LLVM framework. Properties and limitations of various alias analysis algorithms are discussed. Demonstrated are different approaches to working with predicates and integration of these principles with LLVM. One of the outcomes of this master's thesis is design and implementation of algorithm for profile guided if-conversion.

This paper describes methods and procedures used for code analysis and transformation. It contains basic information of a science discipline called reverse engineering and its use in information technologies. The primary objective is a construction of a generic reverse compiler or decompiler, i.e. tool that can recompile from binary form (optionally from symbolic machine code) to a high level language. This operation is highly dependent on the concrete instruction set and processor architecture. This problem is solved with description of semantic of each instruction by a special language designed for this use. The output is the high level language code and is functionally equivalent to the input. The program is therefore able to work with each instruction set and code written by it can be transformed into the chosen high level language. This proposal is implemented in practice as a part of project Lissom. Generic decompiler is completely new idea. The thesis contains entirely new techniques from theory of compilers and optimizations made by the author.

This thesis deals with source-code migration of high-level programming languages using decompilation. A migration tool developed within the thesis is built on top of the middle-end and back-end parts of Lissom project decompiler. Several compilers generating LLVM IR code from input languages are discussed. Compilers suitable for integration to the migration tool were chosen. Compiled LLVM IR code is an input of the decompiler's optimizing middle-end. The output from the migration tool is a code in the C language or Python-like language generated by the back-end of the decompiler. The input languages are Fortran and its dialects, C/C++/Objective-C/Objective-C++, and D. The thesis describes problems connected with migration of these languages, their solutions, and ways to improve quality and readability of the produced source code.

In the presence of ionizing particles and other high-energy atomic sources, many electronic and computer systems fail. Single event upsets (SEUs) can be mitigated through hardware and/or software methods. Previous research at BYU has introduced COAST, a compiler-based tool that can automatically add software protection schemes to improve fault coverage of programs. This thesis will expand on the work already done with the COAST project by proving its effectiveness across multiple platforms and benchmarks. The ability to automatically add fault protection to arbitrary user programs will be very valuable for many application designers. The results presented herein show that mean work to failure (MWTF) of an application can increase from 1.2x – 36x when protected by COAST. In addition to the results based on bare metal applications, in this thesis we will show that it is both possible and profitable to protect a real-time operating system with COAST. We present experimental results which show that our protection scheme gives a 2x – 100x improvement in MWTF. We also present a fault injection framework that allows for rapid and reliable testing of multiple protection schemes across different benchmarks. The code setup used in this paper is publicly available. We make it public in the hope that it will be useful for others doing similar research to have a concrete starting point.

WebAssembly has become the fourth official web language, along with HTML, CSS and JavaScript since 2019. WebAssembly allows web browsers to execute existing programs or libraries written in other languages, such as C/C++ and Rust. In addition, WebAssembly evolves to be part of edge-cloud computing platforms. Despite being designed with security as a premise, WebAssembly is not exempt from vulnerabilities. Therefore, potential vulnerabilities and flaws are included in its distribution and execution, highlighting a software monoculture problem. On the other hand, while software diversity has been shown to mitigate monoculture, no diversification approach has been proposed for WebAssembly. This work proposes software diversity as a preemptive solution to mitigate software monoculture for WebAssembly. Besides, we provide implementations for our approaches, including a generic LLVM superdiversifier that potentially extends our ideas to other programming languages. We empirically demonstrate the impact of our approach by providing Randomization and Multivariant Execution (MVE) for WebAssembly. Our results show that our approaches can provide an automated end-to-end solution for the diversification of WebAssembly programs. The main contributions of this work are: We highlight the lack of diversification techniques for WebAssembly through an exhaustive literature review. We provide randomization and multivariant execution for WebAssembly with the implementation of two tools, CROW and MEWE respectively. We include constant inferring as a new code transformation to generate software diversification for WebAssembly. We empirically demonstrate the impact of our technique by evaluating the static and dynamic behavior of the generated diversification. Our approaches harden observable properties commonly used to conduct attacks, such as static code analysis, execution traces, and execution time. / WebAssembly har sedan 2019 blivit det fjärde officiella webbspråket, tillsammans med HTML, CSS och JavaScript sedan 2019. Detta nya språk tillåter webbläsaren att köra befintliga program eller bibliotek skrivna på andra språk, såsom C/C++ och Rust. Dessutom utvecklas WebAssembly för att vara en del av edge-cloud dator -beräkningsplattformar. Trots att WebAssembly är designatd med säkerhet i fokus som en premiss är det inte undantaget från sårbarheter. Därför ingår potentiella sårbarheter och brister i dess distribution och exekvering, vilket belyser ett av problemen med mjukvarumonokultur. MÅ andra sidan, medan mångfald av programvara har visat sig mildra monokultur, har ingen diversifieringsmetod föreslagits för WebAssembly. Denna avhandling föreslår en mångfald av programvara som en förebyggande lösning med syfte att minska programvarumonokultur för WebAssembly. Dessutom tillhandahåller vi implementeringar för våra tillvägagångssätt, däriblandinklusive en generisk LLVM- superdiversifierare som potentiellt utökar våra idéer till andra programmeringsspråk. Vi visar effekten av vårt tillvägagångssätt empiriskt genom att tillhandahålla rRandomisering och mMultivariante Exekvering (MVE) för WebAssembly. Våra resultat visar att våra tillvägagångssätt kan ge en automatiserad end-to-end lösning för diversifiering av program i WebAssembly. Detta arbetes viktigaste bidragen från detta arbete är: Vi lyfter fram bristen på diversifieringstekniker för WebAssembly genom en uttömmande litteraturgenomgång. Vi tillhandahåller en implementationeringen av två verktyg, CROW och MEWE, som genomför tillhandahåller randomisering och multivariant exekvering för WebAssembly. Vi inkluderar “constant inferring” som en ny kod-transformation för att generera mjukvarudiversifiering för WebAssembly. Vi demonstrerar empiriskt effekten av vår teknik genom att utvärdera det statiska och dynamiska beteendet hos den genererade diversifieringen. Våra metoder härdar mot observerbara egenskaper som vanligtvis används för att utföra attacker, som statisk kodanalys, exekveringsspår och exekveringstid. / <p>QC 20220909</p>