In Figure 1, Preinitialized Environments for Authorized Programs are being used in cross-memory mode. A TCB has performed a program call into the address space where environments have been initialized. The user code running as the target of the program call uses the CELAAUTH macro to call a C/C++ routine within the address space. The CELAAUTH services locate an available environment, including an LAA, in which to run the routine. The address of the LAA is placed in PSALAA and STCBLAA before calling the routine. If the routine requires an additional DLL to be loaded, CELAAUTH queues a request to the worker task, which performs the load and returns the load information. If the TCB is preempted, the LAA address can be restored to PSALAA from STCBLAA when the TCB is re-dispatched.
