Cycle-sensitive register coverage guiding
Cycle-sensitive register coverage guiding is an RTL fuzzing technique described in the paper DifuzzRTL: Differential Fuzz Testing to Find CPU Bugs and used in DIFUZZRTL. The paper presents it as one of several methods introduced to account for the distinctive characteristics of RTL CPU designs.[1][2]
Context in DIFUZZRTL
The broader DIFUZZRTL system is an RTL fuzzer for automatically discovering CPU RTL bugs. Its main fuzzing strategy is register-coverage guided fuzzing, which the paper says is designed to efficiently and correctly identify state transitions in the finite-state behavior of RTL designs.[3] Within that framework, cycle-sensitive register coverage guiding is listed as an additional RTL-specific technique.[2]
What the evidence supports
From the available evidence, the following is directly supported:
- The technique is part of DIFUZZRTL's design.[2]
- It is intended for RTL fuzzing of CPU implementations.[1][2]
- It is motivated by the unique characteristics of RTL designs.[2]
- It appears alongside other DIFUZZRTL mechanisms such as asynchronous interrupt event handling, a unified CPU input format with Tilelink protocols, and drop-in-replacement designs for supporting multiple CPU RTLs.[2]
Scope of available detail
The provided evidence is limited to the paper abstract, so it does not specify the exact algorithm, data structures, or heuristics used by cycle-sensitive register coverage guiding. A more detailed description would require full-text evidence beyond the abstract.[2]
[1]: See citation "DIFUZZRTL is an RTL fuzzer for automatically discovering unknown CPU RTL bugs." [2]: See citation "DifuzzRTL includes cycle-sensitive register coverage guiding as an RTL-specific technique." [3]: See citation "DIFUZZRTL develops register-coverage guided fuzzing to identify RTL state transitions."