CS533 Concepts of Operating Systems Class 6 Micro-kernels Extensibility via Hardware or Software Based Protection

CS533 - Concepts of Operating Systems 2 Questions  What is the structure of a pure emulation library- based OS above a micro-kernel? o How are system calls handled?  What is the structure of a single-server based OS above a micro-kernel? o How are system calls handled?  What is the structure of a multi-server based OS above a micro-kernel? o How are system calls handled?

CS533 - Concepts of Operating Systems 3 Questions  What are the main sources of overhead in micro- kernel based OSs compared to monolithic OSs?  How does L3 address these overheads? o Do these optimizations completely solve the problem?  What minimal abstractions should a kernel provide?

CS533 - Concepts of Operating Systems 4 Questions  What is the motivation for modular operating systems? o Does this imply modules with hardware protection? o.. and what do I mean by hardware protection for modules?  What is the motivation for using hardware protection at module boundaries? o Does this imply message passing across module boundaries? o … what other alternatives do you have?  What is the motivation for using message-passing for inter-module communication?

CS533 - Concepts of Operating Systems 5 Questions  What is extensibility and how does micro-kernel- based OS structure help? o What other approaches are there?

CS533 - Concepts of Operating Systems 6 Questions  Why does Sandboxing slow down normal execution?  Why does it speed up inter-module communication compared to Mach?  What is a jump-table and why is it needed?  On balance is Sandboxing a win or loss? o compared to Mach? o compared to L3/L4?

CS533 - Concepts of Operating Systems 7 Questions  What exactly is a protection domain in SPIN?  How are module boundaries implemented in SPIN? o What implications does this have for kernel extensions?  How does extension code invoke SPIN’s core services, or code in other modules?  How do SPIN’s core services compare to those of micro-kernels?

CS533 - Concepts of Operating Systems 8 Questions  Does the SPIN approach slow down normal execution?  How does it speed up inter-module communication?  On balance is it a win or loss? o compared to Mach? o compared to L3/L4? o compared to Sandboxing?