Generic OS migration from Armv7-M to Armv8-M architecture

The purpose of this document is to list a set of requirements needed for migrating a generic OS kernel running on Armv7-M to the Armv8-M architecture.

List of requirements

If the same OS codebase is used for both Secure and Non Secure builds, it is suggested to put specific code targeted to the Non Secure build under a compile time switch, e.g. #if (DOMAIN_NS == 1U). The OS build system in this case needs to be amended accordingly to support this new switch.
If the OS implements stack limit checking, the PSPLIM register needs to be initialized and properly handled during thread context switch operations.
If the OS manipulates directly the Link Register, the default Link Register value used in Handler mode transitions needs to be differentiated between Secure and Non Secure builds, i.e. 0xFD and 0xBC, respectively.
If the OS manages the non-secure client identification, pelase check the Non-secure Client Extension Integration Guide.