Linvail: A General-Purpose Platform for Shadow Execution of JavaScript

We present Linvail, a novel instrumentation platform for developing dynamic analyses of JavaScript programs. Linvail is particularly well-suited to implementing shadow executions which involve tagging runtime values with analysis-specific data. In contrast to existing instrumentation platforms, Linvail is capable of tracking both tagged objects and tagged primitive values during their entire life-time in a behavior-preserving manner. To demonstrate the expressiveness of our platform, we present the implementation of several state-of-the-art analyses. Our experiments demonstrate that Linvail's accuracy comes at the price of a performance overhead, but we believe that real-world applications will remain usable under analysis.