8.4.1.2 Software

The mechanisms by which the physical processor can enter Monitor mode from the Normal world are tightly controlled, and are all viewed as exceptions to the Monitor mode software. Software executing a dedicated instruction can trigger entry to monitor, the Secure Monitor Call (SMC) instruction, or by a subset of the hardware exception mechanisms. Configuration of the IRQ, external Data Abort, and external Prefetch Abort exceptions can cause the processor to switch to Monitor mode.

The software executed within Monitor mode is implementation-defined, but it generally saves the state of the current world and restores the state of the world at the location to which it switches. It then performs a return-from-exception to restart processing in the restored world.

See the following figure.