Estimating the Cost of Native Method Calls for Resource-bounded Functional Programming Languages

AbstractWe address the problem of applying resource-bounded functional programming languages in practice on object-oriented virtual machines which include calls to native methods coded in low-level languages without garbage collection support. We consider the application of a functional language with a high-level type system which incorporates measures of heap space consumption in types on such an execution platform. We supplement the syntactic type inference procedure of the functional language with a separate analysis which estimates the costs of memory leaks incurred by calls to garbage collection-ignorant functions

Mobile resource guarantees (evaluation paper)

This paper summarises the main outcomes of the Mobile Resource Guarantees (MRG) project, which focused on a proof-carrying-code (PCC) infrastructure for resources to be applied to mobile code. MRG was a three year project funded by the EC under the FET proactive initiative on Global Computing. We give an overview of the projects\u2019 results, discuss the lessons learnt from it and introduce follow-up work in new projects that will build on these results

Do you have space for dessert? a verified space cost semantics for CakeML programs

Garbage collectors relieve the programmer from manual memory management, but lead to compiler-generated machine code that can behave differently (e.g. out-of-memory errors) from the source code. To ensure that the generated code behaves exactly like the source code, programmers need a way to answer questions of the form: what is a sufficient amount of memory for my program to never reach an out-of-memory error? This paper develops a cost semantics that can answer such questions for CakeML programs. The work described in this paper is the first to be able to answer such questions with proofs in the context of a language that depends on garbage collection. We demonstrate that positive answers can be used to transfer liveness results proved for the source code to liveness guarantees about the generated machine code. Without guarantees about space usage, only safety results can be transferred from source to machine code. Our cost semantics is phrased in terms of an abstract intermediate language of the CakeML compiler, but results proved at that level map directly to the space cost of the compiler-generated machine code. All of the work described in this paper has been developed in the HOL4 theorem prover

Software Engineering with Incomplete Information

Information may be the common currency of the universe, the stuff of creation. As the physicist John Wheeler claimed, we get ``it from bit''. Measuring information, however, is a hard problem. Knowing the meaning of information is a hard problem. Directing the movement of information is a hard problem. This hardness comes when our information about information is incomplete. Yet we need to offer decision making guidance, to the computer or developer, when facing this incompleteness. This work addresses this insufficiency within the universe of software engineering. This thesis addresses the first problem by demonstrating that obtaining the relative magnitude of information flow is computationally less expensive than an exact measurement. We propose ranked information flow, or RIF, where different flows are ordered according to their FlowForward, a new measure designed for ease of ordering. To demonstrate the utility of FlowForward, we introduce information contour maps: heatmapped callgraphs of information flow within software. These maps serve multiple engineering uses, such as security and refactoring. By mixing a type system with RIF, we address the problem of meaning. Information security is a common concern in software engineering. We present OaST, the world's first gradual security type system that replaces dynamic monitoring with information theoretic risk assessment. OaST now contextualises FlowForward within a formally verified framework: secure program components communicate over insecure channels ranked by how much information flows through them. This context helps the developer interpret the flows and enables security policy discovery, adaptation and refactoring. Finally, we introduce safestrings, a type-based system for controlling how the information embedded within a string moves through a program. This takes a structural approach, whereby a string subtype is a more precise, information limited, subset of string, ie a string that contains an email address, rather than anything else

Pre-deployment Analysis of Smart Contracts -- A Survey

Smart contracts are programs that execute transactions involving independent parties and cryptocurrencies. As programs, smart contracts are susceptible to a wide range of errors and vulnerabilities. Such vulnerabilities can result in significant losses. Furthermore, by design, smart contract transactions are irreversible. This creates a need for methods to ensure the correctness and security of contracts pre-deployment. Recently there has been substantial research into such methods. The sheer volume of this research makes articulating state-of-the-art a substantial undertaking. To address this challenge, we present a systematic review of the literature. A key feature of our presentation is to factor out the relationship between vulnerabilities and methods through properties. Specifically, we enumerate and classify smart contract vulnerabilities and methods by the properties they address. The methods considered include static analysis as well as dynamic analysis methods and machine learning algorithms that analyze smart contracts before deployment. Several patterns about the strengths of different methods emerge through this classification process

Dynamic Assembly for System Adaptability, Dependability, and Assurance

(DASASA) ProjectAuthor-contributed print ite

Offline compression for on-chip RAM

ManuscriptWe present offline RAM compression, an automated source-to-source transformation that reduces a program's data size. Statically allocated scalars, pointers, structures, and arrays are encoded and packed based on the results of a whole-program analysis in the value set and pointer set domains. We target embedded software written in C that relies heavily on static memory allocation and runs on Harvard-architecture microcontrollers supporting just a few KB of on-chip RAM. On a collection of embedded applications for AVR microcontrollers, our transformation reduces RAM usage by an average of 12%, in addition to a 10% reduction through a dead-data elimination pass that is also driven by our whole-program analysis, for a total RAM savings of 22%. We also developed a technique for giving developers access to a flexible spectrum of tradeoffs between RAM consumption, ROM consumption, and CPU efficiency. This technique is based on a model for estimating the cost/benefit ratio of compressing each variable and then selectively compressing only those variables that present a good value proposition in terms of the desired tradeoffs