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Nội dung Text: Bài giảng Hệ điều hành nâng cao - Chapter 2: Operating - System Structures
- Chapter 2: Operating-System Structures
Operating System Concepts – 8th Edition
Operating System Concepts – 8th Edition 2.1 Silberschatz, Galvin and Gagne ©2009
- Chapter 2: Operating-System Structures
s Operating System Services
s User Operating System Interface
s System Calls
s Types of System Calls
s System Programs
s Operating System Design and Implementation
s Operating System Structure
s Virtual Machines
s Operating System Debugging
s Operating System Generation
s System Boot
Operating System Concepts – 8th Edition 2.2 Silberschatz, Galvin and Gagne ©2009
- Objectives
s To describe the services an operating system provides to users,
processes, and other systems
s To discuss the various ways of structuring an operating system
s To explain how operating systems are installed and customized and
how they boot
Operating System Concepts – 8th Edition 2.3 Silberschatz, Galvin and Gagne ©2009
- Operating System Services
s Operating systems provide an environment for execution of programs and
services to programs and users
s One set of operating-system services provides functions that are helpful to the
user:
q User interface - Almost all operating systems have a user interface (UI).
4 Varies between Command-Line (CLI), Graphics User Interface (GUI),
Batch
q Program execution - The system must be able to load a program into
memory and to run that program, end execution, either normally or
abnormally (indicating error)
q I/O operations - A running program may require I/O, which may involve a
file or an I/O device
q File-system manipulation - The file system is of particular interest.
Programs need to read and write files and directories, create and delete
them, search them, list file Information, permission management.
Operating System Concepts – 8th Edition 2.4 Silberschatz, Galvin and Gagne ©2009
- Operating System Services (Cont.)
q Communications – Processes may exchange information, on the
same computer or between computers over a network
4 Communications may be via shared memory or through message
passing (packets moved by the OS)
q Error detection – OS needs to be constantly aware of possible
errors
4 May occur in the CPU and memory hardware, in I/O devices, in
user program
4 For each type of error, OS should take the appropriate action to
ensure correct and consistent computing
4 Debugging facilities can greatly enhance the user’s and
programmer’s abilities to efficiently use the system
Operating System Concepts – 8th Edition 2.5 Silberschatz, Galvin and Gagne ©2009
- Operating System Services (Cont.)
s Another set of OS functions exists for ensuring the efficient operation of the
system itself via resource sharing
q Resource allocation - When multiple users or multiple jobs running
concurrently, resources must be allocated to each of them
4 Many types of resources - Some (such as CPU cycles, main memory,
and file storage) may have special allocation code, others (such as I/O
devices) may have general request and release code
q Accounting - To keep track of which users use how much and what kinds
of computer resources
q Protection and security - The owners of information stored in a multiuser
or networked computer system may want to control use of that information,
concurrent processes should not interfere with each other
4 Protection involves ensuring that all access to system resources is
controlled
4 Security of the system from outsiders requires user authentication,
extends to defending external I/O devices from invalid access attempts
4 If a system is to be protected and secure, precautions must be
instituted throughout it. A chain is only as strong as its weakest link.
Operating System Concepts – 8th Edition 2.6 Silberschatz, Galvin and Gagne ©2009
- A View of Operating System Services
Operating System Concepts – 8th Edition 2.7 Silberschatz, Galvin and Gagne ©2009
- User Operating System Interface - CLI
s Command Line Interface (CLI) or command interpreter allows direct
command entry
4 Sometimes implemented in kernel, sometimes by systems
program
4 Sometimes multiple flavors implemented – shells
4 Primarily fetches a command from user and executes it
– Sometimes commands built-in, sometimes just names of
programs
» If the latter, adding new features doesn’t require shell
modification
Operating System Concepts – 8th Edition 2.8 Silberschatz, Galvin and Gagne ©2009
- User Operating System Interface - GUI
s User-friendly desktop metaphor interface
q Usually mouse, keyboard, and monitor
q Icons represent files, programs, actions, etc
q Various mouse buttons over objects in the interface cause various
actions (provide information, options, execute function, open directory
(known as a folder)
q Invented at Xerox PARC
s Many systems now include both CLI and GUI interfaces
q Microsoft Windows is GUI with CLI “command” shell
q Apple Mac OS X as “Aqua” GUI interface with UNIX kernel underneath
and shells available
q Solaris is CLI with optional GUI interfaces (Java Desktop, KDE)
Operating System Concepts – 8th Edition 2.9 Silberschatz, Galvin and Gagne ©2009
- Bourne Shell Command Interpreter
Operating System Concepts – 8th Edition 2.10 Silberschatz, Galvin and Gagne ©2009
- The Mac OS X GUI
Operating System Concepts – 8th Edition 2.11 Silberschatz, Galvin and Gagne ©2009
- System Calls
s Programming interface to the services provided by the OS
s Typically written in a high-level language (C or C++)
s Mostly accessed by programs via a high-level Application Program
Interface (API) rather than direct system call use
s Three most common APIs are Win32 API for Windows, POSIX API for
POSIX-based systems (including virtually all versions of UNIX, Linux,
and Mac OS X), and Java API for the Java virtual machine (JVM)
s Why use APIs rather than system calls?
(Note that the system-call names used throughout this text are
generic)
Operating System Concepts – 8th Edition 2.12 Silberschatz, Galvin and Gagne ©2009
- Example of System Calls
s System call sequence to copy the contents of one file to another file
Operating System Concepts – 8th Edition 2.13 Silberschatz, Galvin and Gagne ©2009
- Example of Standard API
s Consider the ReadFile() function in the
s Win32 API—a function for reading from a file
s A description of the parameters passed to ReadFile()
q HANDLE file—the file to be read
q LPVOID buffer—a buffer where the data will be read into and written from
q DWORD bytesToRead—the number of bytes to be read into the buffer
q LPDWORD bytesRead—the number of bytes read during the last read
q LPOVERLAPPED ovl—indicates if overlapped I/O is being used
Operating System Concepts – 8th Edition 2.14 Silberschatz, Galvin and Gagne ©2009
- System Call Implementation
s Typically, a number associated with each system call
q System-call interface maintains a table indexed according to these
numbers
s The system call interface invokes intended system call in OS kernel
and returns status of the system call and any return values
s The caller need know nothing about how the system call is
implemented
q Just needs to obey API and understand what OS will do as a result
call
q Most details of OS interface hidden from programmer by API
4 Managed by run-time support library (set of functions built into
libraries included with compiler)
Operating System Concepts – 8th Edition 2.15 Silberschatz, Galvin and Gagne ©2009
- API – System Call – OS Relationship
Operating System Concepts – 8th Edition 2.16 Silberschatz, Galvin and Gagne ©2009
- Standard C Library Example
s C program invoking printf() library call, which calls write() system call
Operating System Concepts – 8th Edition 2.17 Silberschatz, Galvin and Gagne ©2009
- System Call Parameter Passing
s Often, more information is required than simply identity of desired
system call
q Exact type and amount of information vary according to OS and
call
s Three general methods used to pass parameters to the OS
q Simplest: pass the parameters in registers
4 In some cases, may be more parameters than registers
q Parameters stored in a block, or table, in memory, and address of
block passed as a parameter in a register
4 This approach taken by Linux and Solaris
q Parameters placed, or pushed, onto the stack by the program and
popped off the stack by the operating system
q Block and stack methods do not limit the number or length of
parameters being passed
Operating System Concepts – 8th Edition 2.18 Silberschatz, Galvin and Gagne ©2009
- Parameter Passing via Table
Operating System Concepts – 8th Edition 2.19 Silberschatz, Galvin and Gagne ©2009
- Types of System Calls
s Process control
q end, abort
q load, execute
q create process, terminate process
q get process attributes, set process attributes
q wait for time
q wait event, signal event
q allocate and free memory
s File management
q create file, delete file
q open, close file
q read, write, reposition
q get and set file attributes
Operating System Concepts – 8th Edition 2.20 Silberschatz, Galvin and Gagne ©2009
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