Project architecture

1. File system organization

The distribution is subdivided in several folders in order to efficiently organize files and logically separate them into different sections. Kaya is a layered OS, so each Phase has been confined in a sub-distribution own hierarchy, in order to ease interchanges between different implementation of the same layer and to underline that opportunity. In addition to this, each Phase has the common unix-like directory organization:

• phaseN/
  • src/: Phase N source code and a test programs;
  • obj/: Phase N objects files;
  • include/: Phase N library headers;
• include/: system common definitions: constants and macro (const.h), types and data structures (types.h);
• dev/: uMPS virtual devices files;
• doc/: documentation root containing various developers informations about project internals and development process.

2. Source modules organization

2.1. Phase 1

Following the evident logical division between two entities that we had to instantiate - processes and semaphores -, we opted for a two-modules subdivision:

• pcb.c: collects primitive functions for PCBs initialization/ allocation/ deallocation, process queue/ tree maintenance;
• st.c: collects primitive functions for SD tree initialization and PCB enqueueing to/dequeueing from semaphores.

2.2. Phase 2

Nucleus modular division reflects main objectives of the operating system: hardware interface, process alternation, low-level synchronization primitives and exception handling routines. Let's see such division in detail:

• initial.c implements main() and exports the nucleus’s global variables (e.g. process count, device descriptors, etc.);
• interrupts.c implements the device interrupt exception handler. Processes all the device interrupts, including Interval Timer interrupts, converting device interrupts into V operations on the appropriate semaphores;
• exception.c implements the TLB program trap and syscall/breakpoint exception handlers;
• dispatcher.c implements Kaya’s process dispatcher and deadlock detector;
• scheduler.c implements Kaya’s process configurable scheduler;
• tools.c implements some kernel utilties and debugging tools.