The lib/payload.c file contains routines for completing the basic
initialisation of a payload before any application main program can be
invoked. These routines are called by the start-up routine but
are implemented in C for convenience.
init_bss Initialises the .bss section of the payload so that
uninitialised global and static variables have a well-defined
initial value of zero.
relocate_data Copies the contents of the payload's .data section to
writable memory so that mutable data structures can be