CSC2108 Lazy Abstraction on Software Model Checking Wai Sum Mong

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

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

Abstract-check-refine Loop

Abstraction State region

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

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

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

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

Architecture of BLAST

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

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

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