Research On Reversible Debugging Based On Xen Virtual Machine

With the booming software industry, size and complexity of software are increasing. In process of software development, it's more difficult to debug. Using ordinary debugging methods, we will encounter two problems. First, some software bug can't be reproduced, since the external environment changes. Second, the system state has changed when we find result caused by the error. It's time-consuming to restart the program. In this paper, we present a new debugging method to solve these problems. This method combines the deterministic recording and replaying technology and the reversible debugging technology.First, we introduce present situation of the deterministic recording and replaying technology and the reversible debugging technology. Then, we discuss how to solve the problems using these technologies. There are two parts of work in the paper, how to implement deterministic recording and replaying system and how to implement reversible debugging by introducing checkpoint mechanism.In research to implement deterministic recording and replaying system, we discuss what information is needed and how to record. We also design a file format to save these records. We add a module in the Xen hypervisor to record the non-deterministic event of the DomU virtual machine, and to replay the running process of DomU using these records.To implement the reversible debugging system, we discuss how to add partial replaying function by introduce checkpoint mechanism, and how to modify the GDB debugger to support reversible debugging.The statistics of experiment shows the reversible debugging method in this paper can reproduce the whole running process, execute and debug the virtual machine reversely. It's only introduces a reasonable performance loss and space consumption.