Making Drivers Pageable

Making Drivers Pageable

By default, the linker assigns names such as ".text" and ".data" to the code and data sections of a driver image file. When the driver is loaded, the I/O manager makes these sections nonpaged. A nonpaged section is always memory-resident.

A driver developer has the option to make designated parts of a driver pageable so that Windows can move these parts to the paging file when they are not in use. To make a code or data section pageable, the driver developer assigns a name that begins with "PAGE" to the section. The I/O manager checks the names of the sections when it loads a driver. If a section name begins with "PAGE", the I/O manager makes the section pageable.

Code that runs at IRQL >= DISPATCH_LEVEL must be memory-resident. That is, this code must be either in a nonpageable segment, or in a pageable segment that is locked in memory. If code that is running at IRQL >= DISPATCH_LEVEL causes a page fault, a bug check occurs. Drivers can use the PAGED_CODE macro to verify that pageable functions are called only at appropriate IRQLs.

If a code or data section is pageable, the driver can lock the section in memory by calling the MmLockPagableCodeSection or MmLockPagableDataSection routine. The section remains locked until the driver calls the MmUnlockPagableImageSection routine to unlock it. While the pageable section is locked, it behaves the same as a nonpaged section.

For information about how to assign names to code and data sections, see MmLockPagableCodeSection and MmLockPagableDataSection.

This section includes the following topics:

When Should Code and Data Be Pageable?

Making Driver Code or Data Pageable



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