FBT provides a probe at the boundary of most functions in the kernel. The boundary of a function is crossed by entering the function and by returning from the function. FBT thus provides two functions for every function in the kernel: one upon entry to the function, and one upon return from the function. These probes are named entry and return, respectively. The function name, and module name are specified as part of the probe. All FBT probes specify a function name and module name.