A Framework for Practical Dynamic Software Updating

Dynamic software updating (DSU) enables a program to be patched on the fly without being shutdown. This paper addresses the practicality problem of the recent research on DSU systems, and presents Replus, a new DSU system that balances practicality and functionality. Replus aims to retain backward binary compatibility and support multi-threaded programs. In addition, it does not require customers to have developer-level software knowledge. More importantly, without specific compiler support, Replus can patch programs that are difficult to be updated at runtime, as well as programs that may incur an indefinite delay in DSU. The key technique of our solution is to update the stack elements for the patched program using two new mechanisms: Immediate Stack Updating, which immediately updates the stack of a thread, and timely stack updating, which only updates the stack frames of the necessary functions without affecting others. Replus also develops an Instruction Level Updating mechanism, which is more efficient for certain security patches. We used popular server applications as test suites to evaluate the effectiveness of Replus. The experimental results demonstrated that Replus can successfully update all the test suites with negligible impact on application performance.