Safety Critical Products: GMART
|A complete safety critical line|
Hills Software offers a complete
safety critical product line that
GMART—Green Hills Software’s Minimal Ada Run-Time product—is designed from the ground up to be certifiable to DO-178B Level A, the highest level within the FAA’s commercial avionics safety critical standard. GMART is also designed to support the established safety-critical SPARK language subset. Support for SPARK means that the GMART product is a no run-time, run-time kernel.
SPARK defines a language subset that is fully deterministic as well as statically verifiable to be logically correct. The subset removed those language features that would not be verifiable or are non-deterministic in their behavior. Ada tasking has been completely removed due to the nondeterminism of its full form. For the same reason, protected objects and types have been removed.
Dynamic memory allocation and deallocation have also been removed to avoid run time memory creep and prevent memory fragmentation that may occur in deallocation. To support this restriction, access types are disallowed. General exceptions have been removed since their propagation to a handler can not be statically evaluated. A single global handler is supported to allow for a more graceful system shutdown should an error occur at run time. Generics are disallowed since only physical instances of software modules can be statically proven to be correct.
More easily certified
using the SPARK subset removes some
generally useful language features,
the resulting program is likely
simpler and easier to certify to
safety critical standards. Removing
these language features also allows
the Ada Run Time System (RTS) to be
simplified and optimized for this
subset. Thus the GMART RTS is
smaller and faster than
general-purpose full Ada RTSes.
GMART is available as a bare machine Ada RTS or integrated with the INTEGRITY-178B partitioned RTOS. As a bare RTS, GMART provides an extremely small and fast single application execution environment. As a kernel within an INTEGRITY-178B partition, GMART provides all the advantages of the bare model with the added feature of potentially running multiple applications on the same single processor.