Embedded systems require low overhead security approaches to ensure that they are protected from attacks. In this paper, we propose a hardware-based approach to secure the operation of an embedded processor instruction-by-instruction, where deviations from expected program behavior are detected within the execution of an instruction. These security-enabled embedded processors provide effective defenses against common attacks, such as stack smashing. Previous work in this area has focused on monitoring a single task on a CPU while here we present a novel hardware monitoring system that can monitor multiple active tasks in an operating-system-based platform. The hardware monitor is able to track context switches that occur in the operating system and ensure that monitoring is performed continuously, thus ensuring system security. We present the design of our system and results obtained from a prototype implementation of the system on an Altera DE4 FPGA board. We demonstrate in hardware that applications can be monitored at the instruction level without execution slowdown and stack smashing attacks can be defeated using our system.