Flexible and Efficient Instruction-Grained Run-Time Monitoring Using On-Chip Reconfigurable Fabric

This paper proposes Flex Core, a hybrid processor architecture where an on-chip reconfigurable fabric (FPGA) is tightly coupled with the main processing core. Flex Core provides an efficient platform that can support a broad range of run-time monitoring and bookkeeping techniques. Unlike using custom hardware, which is more efficient but often extremely difficult and expensive to incorporate into a modern microprocessor, the Flex Core architecture allows parallel monitoring and bookkeeping functions to be dynamically added to the processing core and adapt to application needs even after the chip has been fabricated. At the same time, Flex Core is far more efficient than software implementations because its fine-grained reconfigurable architecture closely matches bit level operations of typical monitoring schemes and allows monitoring schemes to operate in parallel to the monitored core. In fact, our experimental results show that monitoring on Flex Core can almost match the performance of full ASIC implementations. To evaluate the Flex Core architecture, we implemented an RTL prototype along with several extensions including uninitialized memory read checking, dynamic information flow tracking, array bound checking, and soft error checking. The prototypes demonstrate that the architecture can support a range of monitoring extensions with different characteristics in an efficient manner. Flex Core takes moderate silicon area and results in far better performance and energy efficiency than software.