Cross-Memory Services

Kernel processes must be provided with a valid cross-memory descriptor to access address regions outside the kernel global address space or kernel process address space. For example, if a kernel process is to access data from a user-mode process, the system call using the process must obtain a cross-memory descriptor for the user-mode region to be accessed.

Calling the xmattach or xmattach64 kernel service provides a descriptor that can then be made available to the kernel process.

The kernel process should then call the xmemin and xmemout kernel services to access the targeted cross-memory data area. When the kernel process has completed its operation on the memory area, the cross-memory descriptor must be detached by using the xmdetach kernel service.