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Single Binary Opt-In: POOL_NX_OPTIN

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To build a single driver binary that runs both in Windows 8 and in earlier versions of Windows, use the POOL_NX_OPTIN opt-in mechanism. This is a porting aid for third-party hardware vendors who supply a single driver binary to support multiple Windows versions.

To use this opt-in mechanism, do the following:

  • Define POOL_NX_OPTIN = 1 for all source files that you want to opt-in. To do this, include the following preprocessor definition in the appropriate property page for your driver project:

    C_DEFINES=$(C_DEFINES) -DPOOL_NX_OPTIN=1

  • In your DriverEntry (or equivalent) routine, include the following function call:

    ExInitializeDriverRuntime(DrvRtPoolNxOptIn);

    This call must occur before the driver makes any allocations that use the NonPagedPool pool type or makes any calls to the ExInitializeNPagedLookasideList routine. ExInitializeDriverRuntime is a force inline function and can be called on Windows 8 or later versions of Windows.

For most drivers, these two tasks are sufficient to enable the opt-in mechanism for the single driver binary.

Implementation details

POOL_NX_OPTIN works by replacing NonPagedPool with a global POOL_TYPE variable, ExDefaultNonPagedPoolType, which is initialized either to NonPagedPoolNx (for Windows 8 and later versions of Windows) or to NonPagedPoolExecute (for earlier versions of Windows). This opt-in mechanism enables your kernel-mode driver to run both on Windows 8, with the enhanced protection of NX pool, and on earlier versions of Windows, which do not support NX pool. The macro that converts instances of the NonPagedPool constant name to NonPagedPoolNx also converts instances of NonPagedPoolCacheAligned to NonPagedPoolNxCacheAligned.

Support for static libraries (.lib projects)

You can use the POOL_NX_OPTIN opt-in mechanism for a .lib project, but projects that link to the .lib generally must also use POOL_NX_OPTIN. At a minimum, the project that implements the DriverEntry routine must contain the following function call:

ExInitializeDriverRuntime(DrvRtPoolNxOptIn);