Scalable comparison of JavaScript V8 bytecode traces

Abstract

The comparison and alignment of runtime traces are essential, e.g., for semantic analysis or debugging. However, naive sequence alignment algorithms cannot address the needs of the modern web: (i) the bytecode generation process of V8 is not deterministic; (ii) bytecode traces are large.We present STRAC, a scalable and extensible tool tailored to compare bytecode traces generated by the V8 JavaScript engine. Given two V8 bytecode traces and a distance function between trace events, STRAC computes and provides the best alignment. The key insight is to split access between memory and disk. STRAC can identify semantically equivalent web pages and is capable of processing huge V8 bytecode traces whose order of magnitude matches today's web like https: //2019.splashcon.org, which generates approx. 150k of V8 bytecode instructions.

Augmenting Diffs With Runtime Information

“…Test suites may not execute programs exactly the same as they are executed in the field [43], [44]. Nevertheless, it is common to utilize the traces produced during the execution of test suites to understand program changes [43], [45].…”

CROW: Code Diversification for WebAssembly

“…SWAM is a WebAssembly interpreter that provides functionalities to capture the dynamic information of WebAssembly program executions including the stack/memory operations. We compute the DTW distances with STRAC [11].…”