Symbolic execution cannot proceed if the number of iterations in the loop is known. We introduce loopextended symbolic execution, a generalization that broadens the coverage of symbolic results in programs withloops. Dynamic symbolic execution consists in executing the program, starting with arbitrary inputs, while performing a symbolic execution in parallel to collect sym. Mixed concrete and symbolic execution is an important technique for finding and understanding software bugs, including securityrelevant ones. I think symbolic execution can be used in many other interesting ways next. Pdf loopextended symbolic execution on binary programs. In this paper, we first propose a classification of multipath loops to understand the complexity of the loop execution, which is based on the variable updates on the loop conditions and the execution order of the loop paths. We introduce loopextended symbolic execution, a generalization that broadens the coverage of symbolic results in programs with loops. Section 4 gives our method for proving properties of java programs using symbolic execution and invariant generation and section 5 illustrates its application to the verification of several nontrivial java programs. Loopextended symbolic execution on binary programs eecs at. Symbolic execution as empirical studies tool web application security checker enhancement to abstractionbased static analysis program synthesis tool all of these take advantage of.
The second issue is the invocation of any outofline code or module calls. It introduces symbolic variables for the number of times each loop executes, and links these with features of a known input grammar such. The symbolic execution cannot identify of infeasible paths. Loop invariant symbolic execution for parallel programs. So i tapped to install the new software and after a little while got another notice that it had. Software security introducing symbolic execution youtube. In recent years, to maximize the value of software testing and analysis, we have proposed the methodology of cooperative software testing and analysis in short as cooperative testing and analysis to enable testing and analysis tools to cooperate with their users in the form of toolhuman cooperation, and enable one tool to cooperate with another tool in the form of tooltool cooperation. Using dynamic symbolic execution to improve deductive. Overview of our loop extended symbolic execution tool and accessory components. A good survey on symbolic execution for software testing is given in 2. We present cpasymexec, a tool for symbolic execution that is im.
Several extensions to classical symbolic execution and stateoftheart tools are discussed. One of them is called concolic execution a portmanteau of concrete and symbolic execution or dynamic symbolic execution. One problem in exploring code using symbolic execution is loop based path explosion. Several sophisticated loop unrolling strategies proposed in literature aim at performing an informed guess on when no useful information could be extracted from the loop such as the loopextended symbolic execution lese saxena et al. In this article, we give an overview of modern symbolic execution techniques, discuss their key. In proceedings of the 20 international conference on software engineering, icse, pages 212221, piscataway, nj, usa, 20. Finally, translating custom loops to use string functions can also impact native execution, as such functions can be implemented more eiciently, e. Resolving loop based path explosion during symbolic execution. Mar 02, 2009 however, existing symbolic execution techniques are limited to examining one execution path at a time, in which symbolic variables reflect only direct data dependencies.
Symbolic execution tree of function foobar given in figure 1. In proceedings of the eighteenth international sym posium on software testing and analysis, pages. Resolving loop based path explosion during symbolic execution shehbaz jaffer ashvin goel angela demke brown university of toronto abstract symbolic execution is a widely used method for testing device drivers and achieving high code coverage. Extended version, august 2011 3 2 system theoretic methods. Other forms of symbolic analysis of programs include bounded model checking which tools such as cbmc, escjava use and abstractionbased model checking which tools such as slam, blast use. The symbolic execution also known as symbolic evaluation technique is a specific type of symbolic analysis of programs.
Since 1975 there has been references to this concept, but it has become more popular in the last ten years with the new smt solvers and evolved versions of symbolic execution. A survey on loop problems for dynamic symbolic execution dse is given in. Importantly, we take a build security in mentality, considering techniques at each phase of the development cycle that can be used to strengthen the security of software systems. Recent years have witnessed a surge of interest in symbolic execution for software testing, due to its ability to generate highcoverage test suites and. Dse executes the program using concrete random inputs and collects the path condition on the side. On reaching a loop it iteratively solves the appropriate constraint system to find out which path through this loop to take, or, alternatively, whether to continue below the loop. Aug 30, 2016 importantly, we take a build security in mentality, considering techniques at each phase of the development cycle that can be used to strengthen the security of software systems. Techniques for verifying program assertions using symbolic execution exhibit a significant limitation. Citeseerx loopextended symbolic execution on binary programs. In computer science, symbolic execution also symbolic evaluation is a means of analyzing a program to determine what inputs cause each part of a program to execute. Several sophisticated loop unrolling strategies proposed in literature aim at performing an informed guess on when no useful information could be extracted from the loop such as the loop extended symbolic execution lese saxena et al. In this paper we propose a new symbolic execution technique, loopextended symbolic execution or lese for short, which gen. Software security basic symbolic execution youtube. The idea is to enhance the symbolic execution with the utilization of quantitative aspect of the shape, and to construct the exit state of the loop.
We introduce loop extended symbolic execution, a generalization that broadens the coverage of symbolic results in programs with loops. This is the full version of the extended abstract to appear in. The exit state is constrained by a set of numeric constraints containing normal symbolic variables in programs and instrumented symbolic variables on the shapes. Symbolic execution is a successful and very popular technique used in software verification and testing.
Loops are challenging structures for program analysis, especially when loops contain multiple paths with complex interleaving executions among these paths. For sequential programs, there is a way to overcome this limitation using loop invariants. The problem is that even a single loop can generate a huge number of different symbolic execution paths, corresponding to different number of loop iterations. An interpreter follows the program, assuming symbolic values for inputs rather than obtaining actual inputs as normal execution of the program would. In this article, we survey the main aspects of symbolic execution and discuss the most prominent. An interpreter follows the program, assuming symbolic values for inputs rather than obtaining. Citeseerx loopextended symbolic execution on binary.
And in this case in particular, the execution time property of a program cannot be reduced to. We introduce loop extended symbolic execution, a generalization that broadens the coverage of symbolic results in programs withloops. Symbolic execution the symbolic execution of a program is described in this section in an ideal sense, and then, in section 6, a particular practical system which has been built an ap proximation to the ideal is discussed. The problem with the overhead of a loop question is that it is overly reductionist. Improving coverage of test cases generated by symbolic. Loopextended symbolic execution on binary programs eecs. I concrete execution versus symbolic execution i symbolic execution tree i applications of symbolic execution. Loop extended symbolic execution on list manipulating. The technique infers a collection of constraint systems from the program and uses them to steer the symbolic execution towards the target. Loopextended symbolic execution on binary programs request pdf.
Lese, our main contribution, enhances symbolic execution for directly inputdependent data values, as in singlepath. A survey of symbolic execution techniques season lab. Intheloop, simulationbased testing, environment models, uav abstract software for autonomous systems is hard to test, given their. Softwareintheloop sil simulation represents the integration of compiled production source code into a mathematical model simulation, providing engineers with a practical, virtual simulation environment for the development and testing of detailed control strategies for large and complex systems. A bibliography of papers related to symbolic execution saswatanandsymexbib. Box 8718, beijing 80, china 1 introduction for many decades, the correctness of programs has been a concern for computer scientists and software engineers. Each execution state, labeled with an upper case letter, shows the statement to be executed, the symbolic store.
In this paper we propose a new symbolic execution technique, loopextended symbolic execution or. A key limitation of symbolic execution is in dealing with code containing loops. Loop extended symbolic execution on binary programs. Concolic execution and code coverage with triton salesforce. Loopextended symbolic execution on binary programs. We propose a new type of symbolic execution, loop extended symbolic execution or lese, which captures the effects of more related program executions than just a single path as in singlepath symbolic execution, by modeling the effects of loops. Directed symbolic execution department of computer science. Section 4 gives our method for proving properties of java programs using symbolic execution and invariant generation and section 5 illustrates its application to the. A bibliography of papers related to symbolic execution github. Christoph csallner, nikolai tillmann, and yannis smaragdakis. Many security and software testing applications require checking whether. On reaching a loop it iteratively solves the appropriate constraint system to find out which path through this loop to take, or, alternatively, whether to.
Efficient loop navigation for symbolic execution springerlink. Verification of java programs using symbolic execution and. It introduces symbolic variables for the number of times each loop executes, and links these with features of a known input grammar such as variablelength or repeating fields. Computing summaries of string loops in c for better testing. And in this case in particular, the execution time property of a program cannot be reduced to the sum of execution times of individual statements. However, existing symbolic execution techniques are limited to examining one execution path at a time, in which symbolic variables reflect only direct data dependencies. Optimizing symbolic execution for malware behavior. Prateek saxena, pongsin poosankam, stephen mccamant, and dawn song. While software analysis has been the subject of an extensive body of research in computer science, treatment of the topic in the control systems community has been less. Symbolic execution is a successful technique used in software verification and. Symbolic execution is a popular program analysis technique introduced in the mid. It introduces symbolic variables for the number of times each loop executes, and links these with features of a known input grammar such as variablelength or repeating.
Dynamic symbolic execution for invariant inference. You cant perfectly distribute aggegate properties of a program to individual statements. Software inthe loop sil simulation represents the integration of compiled production source code into a mathematical model simulation, providing engineers with a practical, virtual simulation environment for the development and testing of detailed control strategies for large and complex systems. The problem is that even a single loop can generate a huge number of different symbolic execution paths, corresponding to different number of loop iterations and taking various paths through the loop. At some point, symbolic execution will reach the edges of the application library, system, or assembly code calls in some cases, could pull in that code also e.
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