US Patent 7934063 Invoking externally assisted calls from an isolated environment

A method of invoking power processor element (PPE) serviced C library functions on a synergistic processing element (SPE) running in isolated mode. When the SPE initiates a PPE-serviced function, an SPE stub routine allocates a parameter buffer in an open area of a local store (LS) memory within the SPE. The LS memory includes an open area accessible to the PPE, and an isolated area inaccessible to the PPE. The SPE stub routine copies function parameters corresponding to the PPE-serviced function to a buffer within the open area of the LS memory, and writes a message word, which contains an identification variable of the PPE-serviced function and a location variable of the function parameters, to the open area. When execution is temporarily suspended on the SPE, the PPE reads the message word from the open area of the LS memory and executes the PPE-serviced function.