Implementing upcall from secure to non-secure mode by injecting exception into non-secure mode

摘要

A computer system that does not natively support non-maskable interrupts (NMIs) implements NMI-like functionality in a secure monitor. The computer system detects a high priority interrupt and determines whether or not interrupts are enabled or disabled. If interrupts are enabled, the computer system injects an exception into a currently executing thread of system software operating at the second privilege level, and an exception handler processes the exception like a standard exception. If interrupts are disabled, the computer system saves the current system state (e.g., the current program counter and CPU state) and values of one or more exception handling registers in temporary storage and injects an exception into the currently executing thread of the system software, and the exception handler processes the exception in a special manner.

主权项

1. A non-transitory computer readable medium comprising instructions to be executed in a computer system operating at multiple privilege levels including a first privilege level and a second privilege level that is lower than the first privilege level, wherein high priority and standard priority interrupts are generated in the computer system, for carrying out a method of handling a high priority interrupt at the first privilege level, said method comprising:
detecting a high priority interrupt; determining whether or not interrupts are enabled or disabled; if the interrupts are enabled, injecting an exception into a currently executing thread of system software operating at the second privilege level; and if the interrupts are disabled, saving current system state and values of one or more exception handling registers in temporary storage and injecting an exception into the currently executing thread of the system software.