11.12.4 Resolving Symbols

Symbol references within CodeGuard Security segments, and between CodeGuard Security segments, will be processed normally. If access entry points have been specified in a code address reference or in a function call reference, they will be resolved to specific offsets in the access entry tables. This mechanism allows the linker to resolve references to boot or secure functions that are defined only in terms of their access entry slot number, and is the key to supporting independently-linked applications.

Interrupt service routines designated for the boot or secure segments will be installed as a vector in slot 16 of the appropriate segment. Unused slots in the access entry tables are resolved to the unused function handler if one has been defined. Some DSC devices use slot 32 for interrupt service routines.

Note: The linker implements the security model in terms of memory allocation, but does not enforce a security policy. For example, references to a function defined in a secure segment from a lower privileged segment are permitted. Therefore it is possible to successfully link an application that fails at runtime due to CodeGuard Security hardware protection. This should be a relatively uncommon occurrence, since in practice strict CodeGuard Security protection implies independently-linked application segments.