1. A computer-implemented system for designing a configurable processor, the system comprising: hardware generation means for, based on a user-defined specification, generating a description of a hardware implementation of the processor; and software generation means for, based on the user-defined specification, generating software development tools specific to the hardware implementation; wherein the user-defined specification includes a user-defined specification of a processor exception and when a processor instruction raises the exception; and the hardware generation means includes user-defined exception support generating means for generating hardware supporting the user-defined specification of the processor exception as part of the processor hardware implementation.