1. A method of extending a processor system within an integrated circuit, the method comprising: executing program code within the processor system implemented within the integrated circuit, wherein the integrated circuit comprises a programmable fabric, and wherein the processor system is coupled to the programmable fabric; wherein a process-specific circuit implemented within the programmable fabric is unable to translate virtual memory addresses to physical memory addresses; the processor system storing a plurality of descriptors in a memory with each descriptor comprising a first physical memory address and a second physical memory address, wherein each of the plurality of descriptors specifies a different second physical memory address; wherein the processor system translates virtual memory addresses into the first and second physical memory addresses for the plurality of descriptors; for each descriptor of the plurality of descriptors, performing a process using the process-specific circuit implemented within the programmable fabric in lieu of using the processor system by operating on source data indicated by the first physical memory address and storing a result of the process at the second physical memory address of the descriptor.