Hellfire framework (HellfireFW) presents a design flow for the design of MPSoC based critical embedded systems. Health-care electronics, security equipment and space aircraft are examples of such systems that, besides presenting typical embedded system's constraints, bring new design challenges as their restrictions are even tighter in terms of area, power consumption and high-performance in distributed computing involving real-time processing requirement. In this paper, we present the Hellfire framework, which offers an integrated tool-flow in which design space exploration (DSE), OS customization and static and dynamic application mapping are highly automated. The designer can develop embedded sequential and parallel applications while evaluating how design decisions impact in overall system behavior, in terms of static and dynamic task mapping, performance, deadline miss ratio, communication traffic and energy consumption. Results show that: i) our solution is suitable for hard real-time critical embedded systems, in terms of real-time scheduling and OS overhead; ii) an accurate analysis of critical embedded applications in terms of deadline miss ratio can be done using HellfireFW; iii) designer can better decide which architecture is more suitable for the application; iv) different HW/SW solutions by configuring both the RTOS and the HW platform can be simulated.