About Shared Memory and Synchronization

Many drivers share memory with other components. For example:

·         Adjacent drivers in the same stack might share memory mapped for their device.

·         A driver might create a worker thread that uses context information or memory locations that are also accessed elsewhere in the driver.

·         A driver might need to share a buffer with a user-mode application.

In addition, any driver routines that are reentrant or can run concurrently might share memory.

In all such situations, the driver must ensure the integrity of the data by synchronizing access to the shared locations. The most appropriate synchronization technique depends on how the memory is used and which other components use it. For a complete description of the synchronization techniques for kernel-mode components, see “Locks, Deadlocks, and Synchronization,” which is listed in the Resources section at the end of this paper.

In addition, some drivers must share memory with user-mode components. User-mode components cannot allocate virtual memory in the system address space. Although it is possible to map system-space addresses into user space, drivers should avoid doing so for security reasons. Drivers and user-mode components must use other strategies for sharing memory.

“Managing User-Mode Interactions: Guidelines for Kernel-Mode Drivers” describes specific techniques for sharing buffers and section objects with user-mode components. This paper is listed in the Resources section at the end of this paper.