Abstract

Memory access instrumentation is fundamental to many applications such as software transactional memory systems, profiling tools and race detectors. In this talk I present a technique to efficiently instrument memory accesses in x86 machine code to support software transactional memory and profiling. The two primary options in building such an instrumentation system are static and dynamic binary rewriting: the former instruments binaries at link time before execution, while the latter binary rewriting instruments binaries at runtime. Static binary rewriting offers extremely low overhead but is hampered by the limits of static analysis. Dynamic binary rewriting is able to use runtime information but typically incurs higher overhead. In this talk I discuss an alternative: hybrid binary rewriting. Hybrid binary rewriting is built around the idea of a persistent instrumentation cache (PIC) that is associated with a binary and contains instrumented code from it. It supports two execution modes when using instrumentation: active and passive modes. In the active execution mode, a dynamic binary rewriting engine (PIN) is used to intercept execution, and generate instrumentation into the PIC , which is an on-disk file. This execution mode can take full advantage of runtime information. Later, passive execution can be used where instrumented code is executed out of the PIC and uninstrumented code directly from the native binary, leading to overheads similar to that of static binary rewriting.