Lecture 4: Operating System Structures Joe McCarthy CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Outline More examples fork, pipe, dup2 Chapter 2: Operating Systems Structures Next time Chapter 3: Processes CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures More examples C++ programs using fork(), pipe(), dup2() testpipe[0-2].cpp Send “hello” through pipe to STDOUT Differences: hardcoded string vs. arg, write() vs execlp() pipedup2[a-d].cpp Using system calls to do ‘ps –A | tr a-z A-Z’ Differences Parent vs. child calling ps vs. tr Using read() & write() vs. execlp() for tr Linked from prog1b assignment page: http://courses.washington.edu/css430/joemcc/prog/prog1b.html CSS 430: Operating Systems - OS Structures

Chapter 2: OS Structures Operating System Services User Operating System Interface System Calls Types of System Calls System Programs Operating System Design and Implementation Operating System Structure Virtual Machines Operating System Debugging Operating System Generation System Boot Material derived, in part, from Operating Systems Concepts with Java, 8th Ed. © 2009 Silberschatz, Galvin & Gagne CSS 430: Operating Systems - OS Structures

A View of Operating System Services CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures System Calls Programming interface to the services provided by the OS Typically written in a high-level language (C or C++) Mostly accessed by programs via a high-level Application Program Interface (API) rather than direct system call use 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) Why use APIs rather than system calls? (Note that the system-call names used throughout this text are generic) CSS 430: Operating Systems - OS Structures

Example of System Calls System call sequence to copy the contents of one file to another file CSS 430: Operating Systems - OS Structures

Example of System Calls System call sequence to copy the contents of one file to another file CSS 430: Operating Systems - OS Structures

Example of Standard API Consider the ReadFile() function in the 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 CSS 430: Operating Systems - OS Structures

API – System Call – OS Relationship CSS 430: Operating Systems - OS Structures

Standard C Library Example printf() library call  write() system call CSS 430: Operating Systems - OS Structures

System Call Parameter Passing Often, more information is required than simply identity of desired system call Exact type & amount of information vary according to OS & call Three general methods used to pass parameters to the OS CSS 430: Operating Systems - OS Structures

System Call Parameter Passing Often, more information is required than simply identity of desired system call Exact type & amount of information vary according to OS & 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 CSS 430: Operating Systems - OS Structures

Parameter Passing via Table CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Types of System Calls Process control File management Device management Status Information Communications Protection CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Process Control CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Process Control End, abort Load, execute Create process, terminate process Get process attributes, set process attributes Wait for time Wait for event, signal event Allocate memory, free memory CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures File Management CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures File Management Create file, delete file Open, close Read, write, reposition Get file attributes, set file attributes CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Device Management CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Device Management Request device, release device Read, write, reposition Get device attributes, set device attributes Logically attach (mount) or detach (unmount) devices CSS 430: Operating Systems - OS Structures

Information Maintenance CSS 430: Operating Systems - OS Structures

Information Maintenance Get time or date, set time or date Get system data, set system data Get process, file or device attributes Set process, file or device attributes CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Communications CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Communications Create, delete communication connection Send, receive messages Transfer status information Attach or detach remote devices CSS 430: Operating Systems - OS Structures

Windows & Unix System Calls CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures MS-DOS execution (a) At system startup (b) running a program CSS 430: Operating Systems - OS Structures

FreeBSD Running Multiple Programs CSS 430: Operating Systems - OS Structures

OS Design & Implementation Important distinction: Policy: What will be done? Mechanism: How to do it? Benefits: Maximum flexibility Policy changes need not entail mechanism changes & vice versa CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Simple Structure MS-DOS Goal: most functionality in the least space Not divided into modules Interfaces & levels of functionality not well separated CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Layered Approach Modularity: Each layer (level) uses functions & services only from layer(s) directly below Provides functions & services only to layer(s) directly above CSS 430: Operating Systems - OS Structures

Layered Approach to Networking CSS 430: Operating Systems - OS Structures

Traditional UNIX System Structure CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures UNIX Two components Systems programs ls, rm, cp, mv, ps, grep, wc, … The kernel 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 CSS 430: Operating Systems - OS Structures

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 CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Mac OS X Structure CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures 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 CSS 430: Operating Systems - OS Structures

Solaris Modular Approach CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures 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 is provided with a (virtual) copy of underlying computer. CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Virtual Machines (a) Nonvirtual machine (b) virtual machine CSS 430: Operating Systems - OS Structures

Solaris 10 with Two Containers CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures VMware Architecture CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Java Java consists of: Programming language specification Application programming interface (API) Virtual machine specification CSS 430: Operating Systems - OS Structures

The Java Development Kit CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures Cloud Computing CSS 430: Operating Systems - OS Structures

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CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures

The Cost of Convenience CSS 430: Operating Systems - OS Structures

CSS 430: Operating Systems - OS Structures For next time Readings Chapters 3: Processes CSS 430: Operating Systems - OS Structures