IrqlExApcLte3 rule (wdm)

  • Article

The IrqlExApcLte3 rule specifies that the driver calls the following executive support routines only at IRQL <= APC_LEVEL.

Drivers that have errors related to IRQL can cause serious problems and could cause a computer to crash.

Driver model: WDM

Bug check(s) found with this rule: Bug Check 0xC4: DRIVER_VERIFIER_DETECTED_VIOLATION (0x20007), Bug Check 0xA: IRQL_NOT_LESS_OR_EQUAL

Example

The following code violates this rule:

NTSTATUS
DispatchRequest (
    _In_ PDEVICE_REQUEST DeviceRequest
    )
{  
    KIRQL OldIrql;
    KSPIN_LOCK SpinLock;
    NTSTATUS Status;
    ...

    KeInitializeSpinLock(&SpinLock);

    //
    // KeAcquireSpinLock sets IRQL to DISPATCH_LEVEL and the previous IRQL is 
    // written to OldIrql after the lock is acquired.
    //

    KeAcquireSpinLock(&SpinLock, &OldIrql);
    ...

    Status = ProcessRequest(DeviceRequest);

    //
    // KeReleaseSpinLock sets IRQL to the OldIrql returned by KeAcquireSpinLock.
    //

    KeReleaseSpinLock(&SpinLock, &OldIrql);
    ...
}

NTSTATUS
ProcessRequest (
    _In_ PDEVICE_REQUEST DeviceRequest
    )
{
    ERESOURCE Resource;
    NTSTATUS Status;
    ...

    Resource = DeviceRequest->GetTableLock();

    //
    // RULE VIOLATION! - ExAcquireSharedStarveExclusive can be called only at 
    //                   IRQL <= APC_LEVEL. 
    //

    if(!ExAcquireSharedStarveExclusive(&Resource, FALSE)) {
        return STATUS_UNSUCCESSFUL;
    }

    ...

    ExReleaseResourceLite(&Resource);
    ...
    return Status;
}

How to test

At compile time

Run Static Driver Verifier and specify the IrqlExApcLte3 rule.

Use the following steps to run an analysis of your code:
  1. Prepare your code (use role type declarations).
  2. Run Static Driver Verifier.
  3. View and analyze the results.

For more information, see Using Static Driver Verifier to Find Defects in Drivers.
At run time

Run Driver Verifier and select the DDI compliance checking option.

Applies to

ExAcquireResourceExclusiveLite ExAcquireResourceSharedLite ExAcquireSharedStarveExclusive ExAcquireSharedWaitForExclusive ExConvertExclusiveToSharedLite ExDeleteResourceLite

See also

Managing Hardware Priorities Preventing Errors and Deadlocks While Using Spin Locks