Porting Linux to the rVEX reconfigurable VLIW softcore

Abstract

This thesis describes the design and implementation of an FPGA-based hardware platform based on the rVEX VLIW softcore and the adaption of a Linux 2.0 no_mmu kernel to run on that platform. The rVEX is a runtime reconfigurable VLIW softcore processor. It supports various configurations that allow programs to run faster or more efficient. The rVEX core can switch between different configurations while it is running. Reconfigurations are typically performed by a software program that is running on a different processor. We discuss the concept of using an Operating System, running on the core itself, that monitors the execution of its tasks and orchestrates core reconfigurations during task switches. In addition to using statically found optimal configurations, performance counters could be added to the core that measure how efficient a program is running on the current core configuration. The OS could use that data to evaluate if another configuration would be beneficial. The implementation of the hardware platform and the porting of the Linux kernel represent the first steps in working towards that final goal. To support our Linux port, a vectored trap controller has been designed. Additionally, a debugging environment has been created by designing a hardware debug unit, implementing an RSP server program and adding rVEX support to the GNU debugger (GDB).