1. CSC2108 Lazy Abstraction on Software Model Checking Wai Sum Mong

2. Survey of BLAST Berkeley Lazy Abstraction Software Verification Tool –A software model checker for C programs –The goal is to check whether the program obeys the “API rules” Same goal as SLAM (Microsoft) –Based on the abstract-check-refine approach Lazy Abstraction –Integrates and possibly optimizes the abstract-check-refine approach

3. Problem Statement Check whether the lines labeled by ERROR are reachable Static analysis assert(0); - runtime

4. Abstract-check-refine Loop

5. Abstraction State region

6. Lazy Abstraction Integrates the three steps Try to reuse the works Two Principles –On-the-fly Abstraction –On-demand Refinement

7. On-the-fly Abstraction Some regions are never visited Abstract only when needed

8. On-demand Refinement Why check the same region again? Add new predicates only when needed Reuse the partial answer

9. Implementation Control Flow automaton Verification –Forward Search (abstract post) –Backward Counterexample Analysis (concrete pred)

10. Architecture of BLAST

11. BLAST Only checked on device driver Predicates –Support integers only so far No support on multithreading programs in the current release

12. Using BLAST Not a good experience Experiments –Very simple linklist package Error Limitations –Pointer –Multithreaded programs –C source code as input (C library functions?)

13. Conclusion Theoretically, optimizes the checking process Similar to SLAM, except lazy abstraction –No access to SLAM –Cannot evaluate so far