pGNAT : the Ravenscar cross compiler for the Gurkh Project

Abstract

Concurrency has greatly simplified the design of embedded software, but the gain in design simplicity is offset by the complexity of system implementation. The Ravenscar profile of Ada95 defines safe tasking constructs that enable the use of deterministic concurrency. The translation of these high-level constructs by the compiler to deterministic object code is dependent on both the underlying operating system and the system operation platform. The commonly available open-source development tools for compiling Ravenscar compliant Ada95 assume that the operating system is implemented as software. A hardware implemented run-time kernel requires a radical rethink of the execution architecture because operating system calls have to be routed from the host processor running the tasks to the hardware implemented kernel RavenHaRT. The redesigned compiler pGNAT is based on the open-source GNAT compiler and uses the GCC back end to cross compile application code to PowerPC object code. The GNAT run-time library (GNARL) is modified to support the use of RavenHaRT. This thesis presents the technical challenges faced and the modifications carried out for generating RavenHaRT compatible, Ravenscar compliant object code.