The present disclosure discloses a debug unit, comprising: a write register configured to store kernel write data written by a kernel of a processor, wherein the processor is communicatively coupled to a debugger configured to read the kernel write data, wherein the kernel write data is associated with a kernel write flag bit to indicate data validity of the kernel write data; and a control unit including circuitry configured to control access to the write register by the kernel of the processor and the debugger based on data validity indicated by the kernel write flag bit. The present disclosure further discloses a corresponding processor including the debug unit, a corresponding debugger communicatively coupled to the processor, and a corresponding debug system including the processor coupled to the debugger.