Research On VM Extension Based Software Debugging

With rapid development of computer architecture, sophisticated software systems are built to leverage the performance growth, but unfortunately at the cost of software reliability. As the functionality of software is becoming complex, software system's scale is increasing steadily and the potential bugs are hard to catch. So how to improve software reliability become a great challenge for software design and development.Nowadays, in the area of software reliability, for the large, complex, multi-task system, the architectural approach to support software debugging, automatic and intelligent fault diagnosis has the advantages of low cost and good performance, and thus becomes a hot spot on research.In order to support complex software system debugging we introduce a virtual machine architecture extension mechanism to support software debugging. Based on architecture extension we implement the full system log and replay technology and incremental data structure consistency check technology.Firstly we introduce the concept of software reliability and software debugging, and then analyze the research on software debugging and virtual machine, at last we introduce VM extension based software debugging framework.In order to achieve virtual machine architecture extension, we analyze the open-source simulator Bochs including four modules: CPU, memory, clock and interrupt system and I/O devices.In multi-task concurrent system, software fault is difficult to reproduce. In order to help reproduce the error in concurrent system we introduce a full system log and replay mechanism and present the principle and implementation of the three main modules: checkpoint, log and replay.Data structure consistency is crucial for the correctness of software, so a run-time consistency check on a system's data structure will help to the early detection of software fault and its localization. We propose an incremental data consistency check method which is based on an architectural extension. The incremental check can greatly reduce the run-time cost of consistency check. We explain the principle and implementation of the incremental check mechanism, and illustrate it by an example.