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ساختمان سیستم عامل:فصل دوم Operating System Concepts – 8th Edition, Silberschatz, Galvin and Gagne ©2009 فصل دوم :ساختمان سیستم عامل سرویس های سیستم عامل واسط های کاربری سیستم عامل فراخوانی های سیستم ()System Calls انواع فراخوانی های سیستم برنامه های سیستم طراحی و پیاده سازی سیستم عامل ساختمان سیستم عامل ماشین های مجازی ()Virtual Machines Operating System Debugging Operating System Generation System Boot Silberschatz, Galvin and Gagne ©2009 2.2 Operating System Concepts – 8th Edition اهداف توصیف سرویس هایی که یک سیستم عامل برای کاربران ،پردازه ها و سیستم ها مهیا می کند توضیح ساختارهای متفاوت سیستم عامل ها تشریح نحوه نصب ( ،)installشخص ی سازی ( )customizationو چگونگی شروع کار ( )bootسیستم عامل Silberschatz, Galvin and Gagne ©2009 2.3 Operating System Concepts – 8th Edition سرویس های سیستم عامل برای کاربر واسط کاربری -تقریبا همه سیستم عاملها واسط کاربری دارند: به صورت خط فرمان ) ،Command-Line (CLIواسط کاربری گرافیکی ) Graphics User Interface (GUIیا Batch اجرای برنامه -سیستم باید برنامه را در حافظه بارگذاری کند ،اجرا نماید و اجرا را خاتمه دهد (در حالت عادی و غیر عادی) عملیات ورودی/خروجی -یک برنامه در حال اجرا ممکن است به ( I/Oخواندن فایل یا دستگاه ) نیاز داشته باشد File-system manipulation read and write files and directories ،create and delete ، Search ،list file Information ،permission management Silberschatz, Galvin and Gagne ©2009 2.4 Operating System Concepts – 8th Edition یک دید ازسرویس های سیستم عامل Operating System Concepts – 8th Edition 2.5 Silberschatz, Galvin and Gagne ©2009 سرویس های سیستم عامل برای کاربر (ادامه) ارتباطات ( -)Communicationsپردازه ها نیاز به تبادل اطالعات دارند (بر روی یک کامپیوتر یا مابین چند کامپیوتر بر روی یک شبکه) ارتباطات ممکن است توسط حافظه مشترک ( )shared memoryیا با ردوبدل پیغام ( message )passingکه با ارسال بسته ها ( )packetsبر روی شبکه (توسط سیستم عامل) صورت می گیرد تشخیص خطاها ( -)Error detectionسیستم عامل باید از خطاهای ممکن در سیستم آگاهی داشته باشد ممکن است در ،CPUسخت افزار حافظه ،دستگاههای I/Oو یا برنامه کاربر رخ دهند. برای هر نوع از خطاها OS ،باید فعالیت مناسب را انجام دهد تا یک پردازش درست و سازگار ( correct )and consistent computingداشته باشیم. Debugging facilities can greatly enhance the user’s and programmer’s abilities to efficiently use the system Silberschatz, Galvin and Gagne ©2009 2.6 Operating System Concepts – 8th Edition سرویس های سیستم عامل برای سیستم (ادامه) مجموعه ای از سرویس ها در سیستم عامل برای استفاده بهینه از منابع مورد استفاده قرار می گیرند تخصیص منابع ( - )Resource Allocationزمانی که چندین کاربرو کاردرحال اجرای همروند هستند ،منابع به هریک ازآنها باید تخصیص داده شود - Accountingمدیریت روند و میزان استفاده کاربران از سیستم و منابع موجود در آن حفاظت و امنیت ()Protection and Security حفاظت ( :)Protectionبیمه می کند که تمامی دسترس یها به سیستم تحت کنترل باشد امنیت ( :)Securityسیستم در مقابل عوامل خارجی نیازمند تشخیص هویت ( )Authenticationکاربران می باشد و حتی باید در مقابل دسترس ی های غیرمعتبراز طریق دستگاه های خارجی I/Oنیزاز سیستم دفاع نماید Silberschatz, Galvin and Gagne ©2009 2.7 Operating System Concepts – 8th Edition )سرویس های سیستم عامل برای سیستم (ادامه یا مفسر،Command Line Interface (CLI) ، واسط های خط فرمان ) اجازه می دهد به طور مستقیم فرمان ها بهCommand Interpreter( فرمان سیستم داده شود در برخی زمانها به،در برخی سیستمها در هسته سیستم عامل پیاده میشود عنوان یک برنامه سیستم – در بعض ی سیستم عامل ها برای سالیق مختلف موارد مختلف پیاده می شود )Shells( پوسته 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 Operating System Concepts – 8th Edition 2.8 Silberschatz, Galvin and Gagne ©2009 واسط های کاربری سیستم عامل )GUI( واسط کاربری گرافیکی )User-friendly desktop interface( میز کاری واسط کاربری کاربر پسند mouse, keyboard, and monitor . را نشان می دهند... وactions ،programs ،files هاIcons . به وجود آمدXerox PARC برای اولین بار در سیستم . را شامل می شوندGUI وCLI تعداد زیادی از سیستم های امروزی هر دو واسط Microsoft Windows is GUI with CLI “command” shell Apple Mac OS X as “Aqua” GUI interface with UNIX kernel underneath and shells available 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( فراخوانی های سیستم واسط برنامه نویس ی که امکان فراخوانی سرویس های سیستم عامل در برنامه ها را فراهم می آورد . مهیا می گردندC++ یاC ) مانندhigh-level language( معموال برای یک زبان سطح باال ) سطح باال به نامApplication Program Interface( در بیشتر مواقع برنامه ها از طریق یک واسط برنامه نویس ی . استفاده می کنندSystem call به جای استفاده مستقیم ازAPI APIs are Win32 API for Windows POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X) Java API for the Java virtual machine (JVM) Operating System Concepts – 8th Edition 2.12 Silberschatz, Galvin and Gagne ©2009 System Calls مثال ها برای کپی محتوای یک فایل به یک فایل دیگرSystem call روند فراخوانی Operating System Concepts – 8th Edition 2.13 Silberschatz, Galvin and Gagne ©2009 Example of Standard API ReadFile() Win32 API — a function for reading from a file A description of the parameters passed to ReadFile() HANDLE file—the file to be read LPVOID buffer—a buffer where the data will be read into and written from DWORD bytesToRead—the number of bytes to be read into the buffer LPDWORD bytesRead—the number of bytes read during the last read 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 یک عدد نسبت داده می شودsystem call معموال به هر . شامل یک جدول می شود که بر اساس این عدد شاخص گذاری شده استsystem call واسط The system call interface invokes intended system call in OS kernel and returns status of the system call and any return values The caller need know nothing about how the system call is implemented Just needs to obey API and understand what OS will do as a result call Most details of OS interface hidden from programmer by API 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 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 Often, more information is required than simply identity of desired system call Exact type and amount of information vary according to OS and call Three general methods used to pass parameters to the OS Simplest: pass the parameters in registers In some cases, may be more parameters than registers Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register This approach taken by Linux and Solaris Parameters placed, or pushed, onto the stack by the program and popped off the stack by the operating system 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 Process control File management Device management Information maintenance Communications Protection Operating System Concepts – 8th Edition 2.20 Silberschatz, Galvin and Gagne ©2009 Examples of Windows and Unix System Calls Operating System Concepts – 8th Edition 2.21 Silberschatz, Galvin and Gagne ©2009 MS-DOS execution (a) At system startup (b) running a program Operating System Concepts – 8th Edition 2.22 Silberschatz, Galvin and Gagne ©2009 FreeBSD Running Multiple Programs Operating System Concepts – 8th Edition 2.23 Silberschatz, Galvin and Gagne ©2009 )System Programs( برنامه های سیستم System programs provide a convenient environment for program development and execution. The can be divided into: File manipulation Status information File modification Programming language support Program loading and execution Communications Application programs Most users’ view of the operation system is defined by system programs, not the actual system calls Operating System Concepts – 8th Edition 2.24 Silberschatz, Galvin and Gagne ©2009 )System Programs( برنامه های سیستم Provide a convenient environment for program development and execution Some of them are simply user interfaces to system calls; others are considerably more complex File management - Create, delete, copy, rename, print, dump, list, and generally manipulate files and directories Status information Some ask the system for info - date, time, amount of available memory, disk space, number of users Others provide detailed performance, logging, and debugging information Typically, these programs format and print the output to the terminal or other output devices Some systems implement a registry - used to store and retrieve configuration information Operating System Concepts – 8th Edition 2.25 Silberschatz, Galvin and Gagne ©2009 )System Programs( برنامه های سیستم File modification Text editors to create and modify files Special commands to search contents of files or perform transformations of the text Programming-language support - Compilers, assemblers, debuggers and interpreters sometimes provided Program loading and execution- Absolute loaders, relocatable loaders, linkage editors, and overlay-loaders, debugging systems for higher-level and machine language Communications - Provide the mechanism for creating virtual connections among processes, users, and computer systems Allow users to send messages to one another’s screens, browse web pages, send electronic-mail messages, log in remotely, transfer files from one machine to another Operating System Concepts – 8th Edition 2.26 Silberschatz, Galvin and Gagne ©2009 طراحی و پیاده سازی سیستم عامل Design and Implementation of OS not “solvable”, but some approaches have proven successful Internal structure of different Operating Systems can vary widely Start by defining goals and specifications Affected by choice of hardware, type of system User goals and System goals User goals – operating system should be convenient to use, easy to learn, reliable, safe, and fast System goals – operating system should be easy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficient Operating System Concepts – 8th Edition 2.27 Silberschatz, Galvin and Gagne ©2009 طراحی و پیاده سازی سیستم عامل Important principle to separate Policy: What will be done? Mechanism: How to do it? Mechanisms determine how to do something, policies decide what will be done The separation of policy from mechanism is a very important principle, it allows maximum flexibility if policy decisions are to be changed later Operating System Concepts – 8th Edition 2.28 Silberschatz, Galvin and Gagne ©2009 ساختمان ساده MS-DOS – written to provide the most functionality in the least space Not divided into modules Although MS-DOS has some structure, its interfaces and levels of functionality are not well separated Operating System Concepts – 8th Edition 2.29 Silberschatz, Galvin and Gagne ©2009 MS-DOS )Layer Structure( ساختمان الیه ای Operating System Concepts – 8th Edition 2.30 Silberschatz, Galvin and Gagne ©2009 رویکرد الیه ای ()Layered Approach سیستم عامل به تعدادی الیه ( )layerیا سطح ( )levelتقسیم بندی می شود .هر الیه بر روی الیه پایین تر ساخته می شود .پایین ترین الیه (الیه )0سخت افزار است و باالترین الیه (الیه )Nواسط کاربر است. با توجه به پیاده سازی مبتنی بر پیمانه ها ( ،)modularityهر الیه از توابع یا عملیات و سرویس های الیه های پایین تر استفاده می کند. Silberschatz, Galvin and Gagne ©2009 2.31 Operating System Concepts – 8th Edition Traditional UNIX System Structure Operating System Concepts – 8th Edition 2.32 Silberschatz, Galvin and Gagne ©2009 UNIX UNIX – limited by hardware functionality, the original UNIX operating system had limited structuring. The UNIX OS consists of two separable parts Systems programs The kernel Consists of everything below the system-call interface and above the physical hardware Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level Operating System Concepts – 8th Edition 2.33 Silberschatz, Galvin and Gagne ©2009 Layered Operating System Operating System Concepts – 8th Edition 2.34 Silberschatz, Galvin and Gagne ©2009 Microkernel System Structure Moves as much from the kernel into “user” space Communication takes place between user modules using message passing Benefits: Easier to extend a microkernel Easier to port the operating system to new architectures More reliable (less code is running in kernel mode) More secure Detriments: Performance overhead of user space to kernel space communication Operating System Concepts – 8th Edition 2.35 Silberschatz, Galvin and Gagne ©2009 Mac OS X Structure Operating System Concepts – 8th Edition 2.36 Silberschatz, Galvin and Gagne ©2009 Modules Most modern operating systems implement kernel modules Uses object-oriented approach Each core component is separate Each talks to the others over known interfaces Each is loadable as needed within the kernel Overall, similar to layers but with more flexible Operating System Concepts – 8th Edition 2.37 Silberschatz, Galvin and Gagne ©2009 Solaris Modular Approach Operating System Concepts – 8th Edition 2.38 Silberschatz, Galvin and Gagne ©2009 Virtual Machines A virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardware A virtual machine provides an interface identical to the underlying bare hardware The operating system host creates the illusion that a process has its own processor and (virtual memory) Each guest provided with a (virtual) copy of underlying computer Operating System Concepts – 8th Edition 2.39 Silberschatz, Galvin and Gagne ©2009 Virtual Machines History and Benefits First appeared commercially in IBM mainframes in 1972 Fundamentally, multiple execution environments (different operating systems) can share the same hardware Protect from each other Some sharing of file can be permitted, controlled Commutate with each other, other physical systems via networking Useful for development, testing Consolidation of many low-resource use systems onto fewer busier systems “Open Virtual Machine Format”, standard format of virtual machines, allows a VM to run within many different virtual machine (host) platforms Operating System Concepts – 8th Edition 2.40 Silberschatz, Galvin and Gagne ©2009 Virtual Machines (Cont) Non-virtual Machine Virtual Machine (a) Nonvirtual machine Operating System Concepts – 8th Edition (b) virtual machine 2.41 Silberschatz, Galvin and Gagne ©2009 Para-virtualization Presents guest with system similar but not identical to hardware Guest must be modified to run on paravirtualized hardwareF Guest can be an OS, or in the case of Solaris 10 applications running in containers Operating System Concepts – 8th Edition 2.42 Silberschatz, Galvin and Gagne ©2009 Solaris 10 with Two Containers Operating System Concepts – 8th Edition 2.43 Silberschatz, Galvin and Gagne ©2009 VMware Architecture Operating System Concepts – 8th Edition 2.44 Silberschatz, Galvin and Gagne ©2009 The Java Virtual Machine Operating System Concepts – 8th Edition 2.45 Silberschatz, Galvin and Gagne ©2009 Operating-System Debugging Debugging is finding and fixing errors, or bugs OSes generate log files containing error information Failure of an application can generate core dump file capturing memory of the process Operating system failure can generate crash dump file containing kernel memory Beyond crashes, performance tuning can optimize system performance Kernighan’s Law: “Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.” DTrace tool in Solaris, FreeBSD, Mac OS X allows live instrumentation on production systems Probes fire when code is executed, capturing state data and sending it to consumers of those probes Operating System Concepts – 8th Edition 2.46 Silberschatz, Galvin and Gagne ©2009 Solaris 10 dtrace Following System Call Operating System Concepts – 8th Edition 2.47 Silberschatz, Galvin and Gagne ©2009 Operating System Generation Operating systems are designed to run on any of a class of machines; the system must be configured for each specific computer site SYSGEN program obtains information concerning the specific configuration of the hardware system Booting – starting a computer by loading the kernel Bootstrap program – code stored in ROM that is able to locate the kernel, load it into memory, and start its execution Operating System Concepts – 8th Edition 2.48 Silberschatz, Galvin and Gagne ©2009 System Boot Operating system must be made available to hardware so hardware can start it Small piece of code – bootstrap loader, locates the kernel, loads it into memory, and starts it Sometimes two-step process where boot block at fixed location loads bootstrap loader When power initialized on system, execution starts at a fixed memory location Firmware Operating System Concepts – 8th Edition used to hold initial boot code 2.49 Silberschatz, Galvin and Gagne ©2009 پایان فصل دوم Operating System Concepts – 8th Edition, Silberschatz, Galvin and Gagne ©2009