Determining IRQL level

Question

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.

Alex F · Accepted Answer · 2015-03-11T08:03:11.940

5

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.

edited Mar 11 '15 at 08:03

answered Mar 11 '15 at 07:53

Alex F

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Thanks for the answer. Is there any way to set the Irql Level for a function? – Reena Cyril Mar 11 '15 at 08:58
IRQL is not a function attribute. Every function starts on the same IRQL as its caller. There are many ways to change current IRQL, like `KeRaiseIrql` and different synchronization functions. – Alex F Mar 11 '15 at 09:09
Thanks Alex. Ive got the info I was looking for. – Reena Cyril Mar 11 '15 at 09:11
Note, this macro is useful on checked builds only. On a release build it's a NOP – SomeWittyUsername Mar 13 '15 at 15:06

Determining IRQL level

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