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.