Operating Systems: A Modern Perspective, Chapter 3

Operating System Organization 3 Operating System Organization Operating Systems: A Modern Perspective, Chapter 3

Purpose of an OS Coordinate Use of the Abstractions Processes Create the Abstractions Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 OS Requirements Provide resource abstractions Process abstraction of CPU/memory use Address space Thread abstraction of CPU within address space Resource abstraction “Anything a process can request that can block the process if it is unavailable” NT uses “object abstraction” to reference resources File abstraction of secondary storage use Operating Systems: A Modern Perspective, Chapter 3

OS Requirements (cont) Provide resource abstractions Manage resource sharing Time/space-multiplexing Exclusive use of a resource Isolation Managed sharing Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Abstraction & Sharing Program State Process Program State Process Libraries Program State Process OS Services Abstraction Manage sharing ROM Routines Processor(s) Main Memory Devices Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 OS Design Constraints Performance Protection and security Correctness Maintainability Commercial factors Standards and open systems Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Performance The OS is an overhead function  should not use too much of machine’s resources Minimum functionality is to implement abstractions Additional function must be traded off against performance DOS: one process UNIX: low level file system Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Protection & Security Multiprogramming  resource sharing Therefore, need software-controlled resource isolation Security policy: Sharing strategy chosen by computer’s owner Protection mechanism: Tool to implement a family of security policies Operating Systems: A Modern Perspective, Chapter 3

Correctness & Maintainability Security depends on correct operation of software  trusted vs untrusted software Maintainability relates to ability of software to be changed If either is sufficiently important, can limit the function of the OS Guiding a manned spaceship Managing a nuclear reactor Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 OS Functions Device management Process, thread, and resource management Memory management File management Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Device Management Device-Independent Part Device-Dependent Part Device-Dependent Part Device-Dependent Part … Device Device Device Operating Systems: A Modern Perspective, Chapter 3

Process, Thread, and Resource Management Abstraction Process Abstraction Generic Resource Manager Multiprogramming Other … Primary Memory Abstract Resources Processor Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Memory Management Isolation & Sharing Virtual Memory Block Allocation Process Manager Primary Memory Storage Devices Operating Systems: A Modern Perspective, Chapter 3

Exclusive Access to a Resource Processor Process A Process B A’s Protected Object Supervisor Program Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Processor Modes Mode bit: Supervisor or User mode Supervisor mode Can execute all machine instructions Can reference all memory locations User mode Can only execute a subset of instructions Can only reference a subset of memory locations Operating Systems: A Modern Perspective, Chapter 3

Operating Systems: A Modern Perspective, Chapter 3 Kernels The part of the OS critical to correct operation (trusted software) Executes in supervisor mode The trap instruction is used to switch from user to supervisor mode, entering the OS Operating Systems: A Modern Perspective, Chapter 3

Supervisor and User Memory Space User Process Supervisor Process Supervisor Space Operating Systems: A Modern Perspective, Chapter 3

Procedure Call and Message Passing Operating Systems send(…, A, …); receive(…, B, …); receive(…A, …); … send(…, B, …); send/receive call(…); trap return; Operating Systems: A Modern Perspective, Chapter 3

System Call Using the trap Instruction … fork(); Trap Table Kernel fork() { … trap N_SYS_FORK() } sys_fork() sys_fork() { /* system function */ … return; } Operating Systems: A Modern Perspective, Chapter 3

A Thread Performing a System Call User Space Kernel Space Thread fork(); sys_fork() { } Operating Systems: A Modern Perspective, Chapter 3

Basic Operating System Organization File Manager Process, Thread & Resource Manager Memory Manager Device Manager Processor(s) Main Memory Devices Operating Systems: A Modern Perspective, Chapter 3

The UNIX Architecture … … Interactive User Libraries Commands Application Programs … OS System Call Interface Trap Table Device Driver Monolithic Kernel Module Process Management Memory Management File Management Device Mgmt Infrastructure Device Driver … Driver Interface Device Driver Operating Systems: A Modern Perspective, Chapter 3

Microkernel Organization Process Process Libraries Process User Supervisor Server Server Server Device Drivers Microkernel Processor(s) Main Memory Devices Operating Systems: A Modern Perspective, Chapter 3

Windows NT Organization Process Process T T Process T T T T Libraries T T T Process Management Memory Management File Management Device Mgmt Infrastructure Subsystem Subsystem Subsystem User Supervisor I/O Subsystem NT Executive NT Kernel Hardware Abstraction Layer Processor(s) Main Memory Devices Operating Systems: A Modern Perspective, Chapter 3

Monitoring the Kernel Process Process Process Libraries Subsystem Task Manager T Process T T T T Libraries T T T pview pstat Subsystem Subsystem Subsystem User Supervisor I/O Subsystem NT Executive NT Kernel Hardware Abstraction Layer Processor(s) Main Memory Devices Operating Systems: A Modern Perspective, Chapter 3