Most synchronous exception VSR table entries will point to a default
exception VSR which is responsible for handling all exceptions in a
generic manner. The default VSR simply saves the CPU state, makes any
adjustments to the CPU state that is necessary, and calls
cyg_hal_exception_handler().
cyg_hal_exception_handler() needs to pass the
exception on to some handling code. There are two basic destinations:
enter GDB or pass the exception up to eCos. Exactly which
destination is taken depends on the configuration. When the GDB stubs are
included then the exception is passed to them, otherwise it is passed
to eCos.
If an eCos application has been loaded by RedBoot then the VSR table
entries will all point into RedBoot's exception VSR, and will
therefore enter GDB if an exception occurs. If the eCos application
wants to handle an exception itself, it needs to replace the the VSR
table entry with one pointing to its own VSR. It can do this with the
HAL_VSR_SET_TO_ECOS_HANDLER() macro.