A Unified Model for Context-Sensitive Program Analyses: The Blind Men and the Elephant

Context-sensitive methods of program analysis increase the precision of interprocedural analysis by achieving the effect of call inlining. These methods have been defined using different formalisms and hence appear as algorithms that are very different from each other. Some methods traverse a call graph top-down whereas some others traverse it bottom-up first and then top-down. Some define contexts explicitly whereas some do not. Some of them directly compute data flow values while some first compute summary functions and then use them to compute data flow values. Further, different methods place different kinds of restrictions on the data flow frameworks supported by them. As a consequence, it is difficult to compare the ideas behind these methods in spite of the fact that they solve essentially the same problem. We argue that these incomparable views are similar to those of blind men describing an elephant called context sensitivity, and make it difficult for a non-expert reader to form a coherent picture of context-sensitive data flow analysis. We bring out this whole-elephant view of context sensitivity in program analysis by proposing a unified model of context sensitivity which provides a clean separation between computation of contexts and computation of data flow values. Our model captures the essence of context sensitivity and defines simple soundness and precision criteria for context-sensitive methods. It facilitates declarative specifications of context-sensitive methods, insightful comparisons between them, and reasoning about their soundness and precision. We demonstrate this by instantiating our model to many known context-sensitive methods

Automatic static analysis of software performance

Performance is a critical component of software quality. Software performance can have drastic repercussions on an application, frustrating its users, breaking the functionality of its components, or even rendering it defenseless against hackers. Unfortunately, unlike in the program verification domain, robust analysis techniques for software performance are almost non-existent. In this thesis we formalize important classes of performance-related bugs and security vulnerabilities, and implement novel static analysis techniques for automatically detecting them in widely used open-source applications. Our tools are able to uncover 92 performance bugs and 47 security vulnerabilities, while analyzing hundreds of thousands of lines of code and reporting a modest amount of false positives. Our work opens a new avenue for research: the development of rigorous automatic analyses for effective software performance understanding, inspired by traditional research in functional verification.Computer Science

정적 분석기 사용자 편의성 증대에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 2. 이광근.정적 분석기의 사용자들이 흔히 겪는 세 가지 문제들 - 허위 경보, 진행정도 예측 불가, 대상 프로그램의 저작권 침해 우려 - 각각에 대한 해결책들을 제시한다. 첫 번째로, 분석기가 발생시킬 수 있는 다수의 허위 경보들을 보다 쉽게 걸러낼 수 있는 방법을 제시한다. 이 기술은 같은 발생 원인을 공유하는 경보들을 묶어, 그 중 대표 경보만을 사용자에게 제시함으로써 사용자가 허위여부를 판별해야 하는 경보 숫자를 줄인다. 둘째로, 복잡한 프로그램들에 대해서 분석이 오래 걸림에도 불구하고 진행율을 알 수 없었던 기존 문제에 대한 해결책을 제시한다. 마지막으 로, 암호화된 대상 프로그램에 대해 분석을 수행할 수 있는 방법을 제시함으로써 분석 서비스 사용시 발생할 수 있는 저작권 침해 가능성을 차단하는 해결책을 제 시한다. 본 논문에서는 위의 기술들을 엄밀히 정의하고 그 기술들이 실제 C 프로 그램 분석에서 성공적으로 적용될 수 있음을 실험적으로 보인다.As programs become larger and more complex, users of static analyzers often encounter three usability issues. Firstly, static analyzers often produce a large number of both true and false alarms that are tedious to classify manually. Secondly, users cannot but wait long time without any progress information during analysis. Lastly, copy-right concerns over software sources hinder extensive uses of static analyzers. In this dissertation, we present our solutions to the three usability issues. To reduce users' alarm-classification efforts, we propose a sound method for clustering static analysis alarms. Our method clusters alarms by discovering sound dependencies between them such that if the dominant alarms of a cluster turns out to be false, all the other alarms in the same cluster are guaranteed to be false. Once clusters are found, users only need to investigate their dominant alarms. Next, we present a progress indicator of static analyzers. Our technique first combines a semantic-based pre-analysis and a statistical method to approximate how a main analysis progresses in terms of lattice height of the abstract domain. Then, we use this information during the main analysis and estimate the analysis current progress. Lastly, we present a static analysis of encrypted programs to resolve users' copy-right concerns over software sources. Users have purchased expensive commercial static analyzers or outsource static analyses on their programs to analysis servers taking the risk of loss of copy-right. Our method allows program owners to encrypt and upload their programs to the static analysis service while the service provider can still analyze the encrypted programs without decrypting them. We have implemented all the methods on top of a realistic static analyzer for C programs and empirically proved that our methods effectively improve the usability.Chapter 1 Overview 1 1.1 Problems 1 1.2 Solutions 3 1.3 Outline 4 Chapter 2 Preliminaries 6 2.1 Concepts 6 2.2 Static Analyses We Use 9 2.2.1 Interval Analysis 9 2.2.2 Octagon Analysis 12 2.2.3 Pointer Analysis 13 Chapter 3 Method 1. Sound Non-statistical Alarm Clustering 14 3.1 Introduction 14 3.1.1 Problem 14 3.1.2 OurSolution 15 3.1.3 Examples 15 3.1.4 Contributions 18 3.1.5 Outline 19 3.2 AlarmClusteringFramework 19 3.2.1 Static Analysis 19 3.2.2 AlarmClustering 19 3.3 Alarm-Clustering Algorithms 24 3.3.1 Algorithm 1: Finding Minimal Dominant Alarms 26 3.3.2 Algorithm 2: Non-Minimal but Efficient 30 3.4 Instances 32 3.4.1 Setting : Baseline Analyzer 34 3.4.2 Clustering using Interval Domain 34 3.4.3 Clustering using Octagon Domain 36 3.4.4 Clustering using Symbolic Execution 39 3.5 Experiments 41 Chapter 4 Method 2. A Progress Bar for Static Analyzers 47 4.1 Introduction 47 4.2 Overall Approach to Progress Estimation 48 4.2.1 Static Analysis 49 4.2.2 ProgressEstimation 49 4.3 Setting 52 4.4 Details on Our Progress Estimation 53 4.4.1 The Height Function 54 4.4.2 Pre-analysis via Partial Flow-Sensitivity 55 4.4.3 Precise Estimation of the Final Height 57 4.5 Experiments 59 4.5.1 Setting 60 4.5.2 Results 60 4.5.3 Discussion 62 4.6 Application to Relational Analyses 63 Chapter 5 Method 3. Static Analysis with Set-closure in Secrecy 65 5.1 Introduction 65 5.2 Background 67 5.2.1 Homomorphic Encryption 68 5.2.2 TheBGV-type crypto system 70 5.2.3 Security Model 71 5.3 A Basic Construction of a Pointer Analysis in Secrecy 71 5.3.1 A Brief Review of a Pointer Analysis 72 5.3.2 The Pointer Analysis in Secrecy 72 5.4 Improvement of the Pointer Analysis in Secrecy 76 5.4.1 Problems of the Basic Approach 76 5.4.2 Overview of Improvement 77 5.4.3 Level-by-levelAnalysis 77 5.4.4 Ciphertext Packing 80 5.4.5 Randomization of Ciphertexts 83 5.5 Experimental Result 83 5.6 Discussion 84 Chapter 6 Related Works 86 6.1 Sound Non-statistical Alarm Clustering 86 6.2 A Progress Bar for StaticAnalyzers 87 6.3 Static Analysis with Set-closure in Secrecy 88 Chapter 7 Conclusions 89 Chapter 8 Appendix 100 A Proofs of Theorems 100 B Progress Graph 107 C Algorithms for the Pointer Analysis in Secrecy 110 초 록 113Docto

Software Techniques for Energy Efficient Memories

Ph.DDOCTOR OF PHILOSOPH

Computer Aided Verification

This open access two-volume set LNCS 10980 and 10981 constitutes the refereed proceedings of the 30th International Conference on Computer Aided Verification, CAV 2018, held in Oxford, UK, in July 2018. The 52 full and 13 tool papers presented together with 3 invited papers and 2 tutorials were carefully reviewed and selected from 215 submissions. The papers cover a wide range of topics and techniques, from algorithmic and logical foundations of verification to practical applications in distributed, networked, cyber-physical, and autonomous systems. They are organized in topical sections on model checking, program analysis using polyhedra, synthesis, learning, runtime verification, hybrid and timed systems, tools, probabilistic systems, static analysis, theory and security, SAT, SMT and decisions procedures, concurrency, and CPS, hardware, industrial applications

Late-bound code generation

Each time a function or method is invoked during the execution of a program, a stream of instructions is issued to some underlying hardware platform. But exactly what underlying hardware, and which instructions, is usually left implicit. However in certain situations it becomes important to control these decisions. For example, particular problems can only be solved in real-time when scheduled on specialised accelerators, such as graphics coprocessors or computing clusters. We introduce a novel operator for hygienically reifying the behaviour of a runtime function instance as a syntactic fragment, in a language which may in general differ from the source function definition. Translation and optimisation are performed by recursively invoked, dynamically dispatched code generators. Side-effecting operations are permitted, and their ordering is preserved. We compare our operator with other techniques for pragmatic control, observing that: the use of our operator supports lifting arbitrary mutable objects, and neither requires rewriting sections of the source program in a multi-level language, nor interferes with the interface to individual software components. Due to its lack of interference at the abstraction level at which software is composed, we believe that our approach poses a significantly lower barrier to practical adoption than current methods. The practical efficacy of our operator is demonstrated by using it to offload the user interface rendering of a smartphone application to an FPGA coprocessor, including both statically and procedurally defined user interface components. The generated pipeline is an application-specific, statically scheduled processor-per-primitive rendering pipeline, suitable for place-and-route style optimisation. To demonstrate the compatibility of our operator with existing languages, we show how it may be defined within the Python programming language. We introduce a transformation for weakening mutable to immutable named bindings, termed let-weakening, to solve the problem of propagating information pertaining to named variables between modular code generating units.Open Acces

Computer Aided Verification

This open access two-volume set LNCS 10980 and 10981 constitutes the refereed proceedings of the 30th International Conference on Computer Aided Verification, CAV 2018, held in Oxford, UK, in July 2018. The 52 full and 13 tool papers presented together with 3 invited papers and 2 tutorials were carefully reviewed and selected from 215 submissions. The papers cover a wide range of topics and techniques, from algorithmic and logical foundations of verification to practical applications in distributed, networked, cyber-physical, and autonomous systems. They are organized in topical sections on model checking, program analysis using polyhedra, synthesis, learning, runtime verification, hybrid and timed systems, tools, probabilistic systems, static analysis, theory and security, SAT, SMT and decisions procedures, concurrency, and CPS, hardware, industrial applications

Computer Aided Verification

This open access two-volume set LNCS 10980 and 10981 constitutes the refereed proceedings of the 30th International Conference on Computer Aided Verification, CAV 2018, held in Oxford, UK, in July 2018. The 52 full and 13 tool papers presented together with 3 invited papers and 2 tutorials were carefully reviewed and selected from 215 submissions. The papers cover a wide range of topics and techniques, from algorithmic and logical foundations of verification to practical applications in distributed, networked, cyber-physical, and autonomous systems. They are organized in topical sections on model checking, program analysis using polyhedra, synthesis, learning, runtime verification, hybrid and timed systems, tools, probabilistic systems, static analysis, theory and security, SAT, SMT and decisions procedures, concurrency, and CPS, hardware, industrial applications