Branch bitstream [Machine Instruction-level System Tracing]

Tracing is an approach used for debugging and profiling software. Conventional approach to create traces is to instrument program´s code tapping data out from an execution. An original execution is mixed with tracing routines. In consequent, a program in production state and development state are not identical. In addition, instrumentation code adds execution overhead and increases error probability to a traced program. Branch Bitstream (BB) aims to solve aforementioned drawbacks by partitioning tracing routines to an execution environment instead. Traces are generated without modifying a program. A trace-driven simulator uses a trace file and a program to perfectly reconstruct pre vious execution. This work implemented this concept in QEMU 0.14 for TCT architecture. Linux 3.0.0-rc7 booting was used as a profiling example. Emulation overhead is 2 times longer than one without BB in the current implementation.