Control and Status Registers (CSR)

Overview

Control and Status Registers (CSRs) are registers that control processor operation and hold processor state. In the ProcessorFuzz work, CSRs are treated as a compact architectural signal for observing when execution reaches a new processor state.

Use in processor fuzzing

ProcessorFuzz introduces a CSR-transition coverage metric for hardware fuzzing of processors. The key idea is that a new transition in CSR values counts as a coverage increase. Because CSRs control and hold processor state, transitions in their values are used as evidence that the processor has entered a new state.