Introduction and Overview

Transcription

1 Introduction and Overview Instructor: Adam C. Champion, Ph.D. CSE 2431: Introduction to Operating Systems Reading: Chapters 1 2, [OSC] (except Sections ) 1

2 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 2

3 Info About Me Adam Champion Ph.D., OSU, 2017 Research interests: Mobile systems, networks, security, analytics Computer networking & wireless communications Parallel and distributed systems More: 3

4 More about you? How do you handle the scenario where there is no response from apps? Do you know where variables in a program are stored? What are system calls? Any examples? How do you organize your files? 4

5 Course Objectives Understand functions and structures of operating systems Processes & Synchronization Memory System File Systems I/O Systems Understand issues in the design of operating systems 5

6 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 6

7 What is an OS? (1) System and Application Programs OS Hardware Providing Services: Abstraction Convenience Standardization Resource Management: Allocation Reclamation Protection Virtualization Program that acts as an intermediary between system/app programs and the computer hardware 7

8 What is an OS? (2) Resources Allocation Reclamation Protection Virtualization Examples: CPUs Memory I/O devices 8

9 What is an OS? (3) Resources Allocation Reclamation Protection Virtualization Example: Voluntary at runtime Implied at termination Preemptive 9

10 What is an OS? (4) Resources Allocation Reclamation Protection Virtualization Protect resources from unauthorized accesses Related to reliability & security 10

11 What is an OS? (5) Resources Allocation Reclamation Protection Virtualization Examples: Virtual memory Timeshared CPU 11

12 What is an OS? (6) Resources Allocation Reclamation Protection Virtualization Group discussion Topic: Real life analogies of Operating Systems? 5-6 students per group 3 minutes discussion 12

13 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 13

14 History of Operating Systems First generation: Vacuum tubes and plug boards (no OS) Second generation: Transistors, batch systems Third generation: ICs and multiprogramming Fourth generation: 1980 present Personal computers, mobile devices, sensors 14

15 First Generation: (no OS) ENIAC (Source: Wikipedia) 15

16 The First Computer Bug Source: Wikipedia 16

17 History of Operating Systems ( ) Early batch system Single user Secure Programmer/user as the operator But low CPU utilization: slow mechanical I/O devices 17

18 History of Operating Systems ( ) Multiprogramming system Three jobs in memory: 3rd generation Spooling: use disk as a very large buffer for input/output devices Timesharing: quick response time 18

19 History of Operating Systems (1980 present) Mainframe operating systems Server operating systems Multiprocessor operating systems Personal computer operating systems Real-time operating systems Embedded operating systems Smart card operating systems 19

20 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 20

21 A Basic (Single CPU) Computer System 21

22 Typical PC (Intel-based) Computer Structure 22

23 Typical Memory Storage Structure 100 msec Magnetic tape TB When you program, have you thought about Registers? Disks? 23

24 Moving-Head Disk Mechanism 24

25 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 25

26 A Peek Into Unix Application Libraries Portable OS Layer User space/level Kernel space/level Machine-dependent layer 26

27 Unix: Application Application (E.g., emacs) Libraries Written by programmer Compiled by programmer Uses function calls Portable OS Layer Machine-dependent layer 27

28 Unix: Libraries Application Libraries (e.g., stdio.h) Portable OS Layer Written by elves Provided pre-compiled Defined in headers Input to linker (compiler) Invoked like functions May be resolved when program is loaded Machine-dependent layer 28

29 Typical Unix OS Structure Application Libraries Portable OS Layer Machine-dependent layer System calls (read(), open(), etc.) All high-level code 29

30 Typical Unix OS Structure Application Libraries Portable OS Layer Machine-dependent layer Bootstrap System initialization Interrupt and exception I/O device driver Memory management Kernel/user mode switching Processor management 30

31 Discussion What will future Operating Systems look like? years from now? What are the problems for current OSes? How can future OSes fix them? What features will future OSes have? What are the criteria to evaluate the OSes? 31

32 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 32

33 Questions? Why kernel and user mode? How? 33

34 Why Kernel Mode? Services that need to be provided at kernel level System calls: file open, close, read and write Control the CPU so that users won t stuck by running while ( 1 ) ; Protection: Keep user programs from crashing OS Keep user programs from crashing each other How do we achieve these? 34

35 How to Provide Kernel Mode? CPU mode bit added to computer hardware to indicate the current CPU mode: 0 (kernel) or 1 (user). When an interrupt occurs, CPU hardware switches to the kernel mode. Switching to user mode (from kernel mode) done by setting CPU mode bit (by an instruction). Exception/Interrupt/Fault kernel user Set user mode Privileged instructions can be executed only in kernel mode. 35

36 Outline Course Information What is an OS? History of OSes Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS Major Components 36

37 Three Interrupt Classes Interrupts caused by hardware failures Power outage Memory parity error Interrupts caused by external events: Reset I/O devices Interrupts caused by executed instructions Exceptions System calls 37

38 Interrupts by External Events Reset IRQ 1 IRQ 0 Timer 38

39 Exceptions: caused by errors during instruction execution: Address Error: a reference to a nonexistent or illegal memory address; Reserved Instruction: An instruction with undefined opcode field or a privileged instruction in User mode; Integer Overflow: An integer instruction results in a two s complement overflow; Floating Point Error: e.g., divide by zero, overflow, underflow; Special instructions: Interrupts Caused by Instruction Execution MIPS processors: Syscall instruction executed Intel processors: INT n instruction executed 39

40 Hardware Handling of Interrupts Save the addresses of the interrupted instruction Transfer control to the appropriate interrupt service routine (software) Sets CPU to kernel mode May do some security checks here 40

41 System Call Steps Example: read(fd,buffer,nbytes) 41

42 OS Major Components Process Management Resource Management CPU Memory I/O Devices File System Bootstrap Design Issues 1. Efficiency 2. Fairness 3. Sharing 4. Protection 42

43 Process Management (1) What is a process? Is it a program? In short: it is a program that is executing What does a process need? CPU time, memory, files, and I/O devices 43

44 Process Management (2) How to create/terminate processes? fork() execve() kill() exit() What else from OS? Process synchronization Process communication Deadlock handling 44

45 CPU Management Responsibilities CPU scheduling Allocation for multiple CPUs Issues: CPU utilization Fairness Deadlock free 45

46 Memory Management Why? Multiple programs in limited memory Responsibilities: Track memory usage Allocation/De-allocation Transfer from and to secondary storage 46

47 I/O Devices Why? Too many details Too many different devices Responsibilities Improve I/O efficiency & utilization General interfaces Extensible for specific hardware devices SCSI device driver SCSI device controller Kernel Kernel I/O Subsystem Keyboard device driver Keyboard device controller ATAPI device driver ATAPI device controller SCSI devices Keyboard devices ATAPI devices 47

48 File System Example 48

49 File System Why? A easy way for users/apps to manipulate information How to create/open/close/delete files/directories? open() close() link() unlink() 49

50 Summary Course Overview What is an OS? History of OS Hardware Review A Typical UNIX Dual-Mode CPU Operations Interrupts and System Calls OS major components 50