Non-Interference Analysis for Mixed Criticality Code 
in Avionics Systems






Critical, Static Analysis, Assembler Assertions


The increased reliance on digital flight 
control systems within military aircraft is placing 
heavy demands on resources within aircraft. In 
particular systems currently have dedicated processors, which 
are replicated for fault tolerance. If one 
system fails then an aircraft often needs 
to be grounded until the system is 
fixed or replaced, thus significantly reducing the 
effective mean time between failures. Future aircraft 
system procurement is expected to utilise a 
new form of modular architecture which will 
aid a reduction in hardware requirements and 
significantly increase the mean time between failures. 
However, the architectures being put forward only 
provide for hardware partitioning, and there is 
little protection for safety-critical processes from interference 
by rogue processes within the same hardware 
partition. This paper puts forward a mixed 
static/dynamic approach for assuring software partitioning of 
processes within a single hardware partition. This 
will allow both safety-critical and non-critical applications 
to coexist in the same hardware partition, 
whilst ensuring that non-critical code can never 
corrupt a safety-related component. Such an approach 
is a necessity in modular avionics if 
all processes are not to be classified 
and developed as safety critical.