Odin: on-demand instrumentation with on-the-fly recompilation

Instrumentation is vital to fuzzing. It provides fuzzing directions and helps detect covert bugs, yet its overhead greatly reduces the fuzzing throughput. To reduce the overhead, compilers compromise instrumentation correctness for better optimization, or seek convoluted runtime support to remove unused probes during fuzzing. In this paper, we propose Odin, an on-demand instrumentation framework to instrument C/C++ programs correctly and flexibly. When instrumentation requirement changes during fuzzing, Odin first locates the changed code fragment, then re-instruments, re-optimizes, and re-compiles the small fragment on-the-fly. Consequently, with a minuscule compilation overhead, the runtime overhead of unused probes is reduced. Its architecture ensures correctness in instrumentation, optimized code generation, and low latency in recompilation. Experiments show that Odin delivers the performance of compiler-based static instrumentation while retaining the flexibility of binary-based dynamic instrumentation. When applied to coverage instrumentation, Odin reduces the coverage collection overhead by 3× and 17× compared to LLVM SanitizerCoverage and DynamoRIO, respectively.