windowsdevice-driverirql

Determining IRQL level

How can the IRQL Level of a piece of driver code be determined. PAGED_CODE() macro specifies that the piece of code can be run in an IRQL level less than DISPATCH_LEVEL.But haw can the exact IRQL Level be determined.

Solution

  • KeGetCurrentIrql function returns the current IRQL:

    KIRQL KeGetCurrentIrql(void);

    PAGED_CODE macro uses this function by the following way:

    #define PAGED_CODE() \
    if (KeGetCurrentIrql() > APC_LEVEL) { \
        KdPrint(( "EX: Pageable code called at IRQL %d\n", KeGetCurrentIrql() )); \
        ASSERT(FALSE); \
    }

    This macro should be placed to any pageable function, it crashes the driver in the case when the function is called at IRQL that doesn't allow paging.