One of the main limitations of the original Detours library (besides the non-commercial restrictions) is the lack of support for kernel mode detours: the original library makes hard-coded calls to user mode APIs such as VirtualProtect and FlushInstructionCache that, obviously, are not exported to kernel mode drivers. Furthermore the library code that patches the application target code is integrated into the Detours disassembler implementation: this is NOT a good thing when you are patching the entry point of a keyboard ISR or of a crucial high-concurrency kernel function. In these cases it may be useful to run the disassembler and the patching code separately: applying the JMP patch may require, for example, some sort of intra-processor syncronization method (such as disabling the interrupts or raising the IRQL to HIGH_LEVEL) or of inter-processor synchronization (such as an hand-made IPI interrupt or more realistically a more practical equivalent such as an high-importance targeted DPC...).