DOCSLIB.ORG

Real Operating Systems Lecture #12

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Real Operating Systems Lecture #12 Real Operating Systems Lecture #12 Department of Computer Science and Technology University of Bedfordshire Written by David Goodwin, based on the lecture series of Dayou Li and the book Understanding Operating Systems 4thed. by I.M.Flynn and A.McIver McHoes (2006). Operating Systems, 2012 bg=white Real Operating Outline Systems Introduction Introduction DOS DOS Windows Windows Unix & Linux Unix & Linux Memory Management DOS Memory Management Windows DOS Linux Process Windows Management Linux DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating INTRODUCTION TO DIFFERENT Systems O/Ss Introduction DOS Windows Unix & Linux Memory Management DOS I Three typical operating systems Windows I Disk operating system (DOS) Linux I Windows Process Management I Unix/Linux DOS Windows Linux bg=white Real Operating DOS Systems Introduction I History DOS Windows I In 1980, IBM looked for an operating system for its Unix & Linux soon-to-be-released 6-bit personal computers Memory Management I Digital Research offered CP/M-86 DOS I Softech offered P-System Windows I MS Linux I MS also looked for OS for its 16-bit computers Process Management I Seattle Computer Products offered 86-DOS DOS I MS bought it and renamed it MS-DOS Windows Linux I IBM chose MS-DOS in 1981 and called it PC-DOS I MS-DOS evolved from v 1.0 to v 6.22 from 1981 to 1994 bg=white Real Operating DOS Systems I Features Introduction I Single user, stand-alone DOS desktop Windows I Command-line Unix & Linux I Commands are based on Memory words Management DOS I Examples Windows I COPY { copy a file Linux I DEL { delete a file Process Management I PRINT { print files on a DOS printer Windows I DIR { list files in this Linux directory I MD { make a new directory I CHKDSK { check the disk I COMP { compare two files bg=white Real Operating Layers of DOS Systems I Three layers: I Top layer { command processor Introduction DOS I Sends prompts to user Windows I Accepts commands Unix & Linux I Executes commands (including interpret commands to Memory machine language) Management I Issues responses DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating Layers of DOS Systems I I Middle layer { DOS kernel Introduction I A program containing routines that are needed for DOS interfacing disk Windows I Stored in MSDOS.SYS file Unix & Linux I Read to memory during initialisation time Memory Management DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating Layers of DOS Systems I I Bottom layer { BIOS (Basic Input/Output System) Introduction I Interfaces I/O devices such as printer, monitor and DOS keyboard Windows I Controls data flow to and from these devices Unix & Linux I Receive statues information about these devices Memory Management DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating WINDOWS Systems I History Introduction DOS I Initiative Windows I To allow users to not have to remember and use Unix & Linux system commands but via a user-friendly interface { Memory GUI Management DOS I Not a replacement of DOS Windows I Early versions (1985 to 1992) Linux I Windows 1.0 to 3.1 are only \interfaces" between GUI Process Management and DOS DOS I Single-user rather than networked Windows Linux I True O/S since 1992 I Windows 95 is first true O/S I Network O/S I Windows NT version 3.1 in 1993 led by David Cutler bg=white Real Operating WINDOWS - Design goals Systems I Extensibility { be easily enhanced to meet changes over time to support new hardware and software technologies Introduction I Privileged process and non-privileged processes DOS Windows I Kernel mode refers to the privileged mode of a Unix & Linux processor Memory I All instructions are allowed Management DOS I System memory is accessible Windows I Use mode refers to the non-privileged mode of a Linux processor Process Management I Only certain instructions are allowed DOS I System memory is not accessible Windows I O/S executes in kernel mode Linux I Application programs (protected subsystems) run in user mode I Modular structure I Drivers for new file systems, devices and networks I Objects { abstract data types bg=white Real Operating WINDOWS - Design goals Systems Introduction DOS Windows I Portability { ability for O/S to operate on different Unix & Linux machines that use different processors or configurations Memory Management I Code is modular DOS I Standard high-level programming language c/c++ is Windows used for implementation Linux I Hardware abstraction layer (HAL) providing isolation Process from hardware dependencies Management DOS I HAL abstracts hardware such as caches with a layer of Windows low-level software so that higher-level code needs no Linux change when moving from one platform to another bg=white Real Operating WINDOWS - Design goals Systems I Reliability { predictability in responding to error Introduction conditions, including hardware failures DOS Windows I Modular design Unix & Linux I NTFS to recover all types of errors Memory I US government-certifiable security Management I Virtual memory strategy to prevent one user from DOS Windows reading or modifying memory that is occupied by Linux another user Process Management I Compatibility { ability of an O/S to execute programs DOS written for other O/Ss Windows Linux I Execution environments for applications that differ from Win32 API I Source-level compatibility to POSIX (Portable Operating System Interface for Computer Environment) I Supporting already-existing file systems bg=white Real Operating WINDOWS - Design goals Systems Introduction DOS Windows I Performance { fast response times Unix & Linux I Crucial processes such as system calls and page faults Memory Management are tested and optimised DOS I LPC (local procedure call) to guarantee fast Windows communications among the protected subsystems Linux Process I Carefully designing the environment subsystems to Management ensure the speed of frequently used systems services DOS I Critical elements of Windows' networking software are Windows built in the privileged protion Linux bg=white Real Operating UNIX AND LINUX Systems Introduction DOS Windows Unix & Linux Memory Management I Advantages shared by Unix and Linux DOS I Portable Windows Linux I Powerful utilities Process I Device independent Management DOS Windows Linux bg=white Real Operating UNIX AND LINUX Systems I Evolution of UNIX Introduction DOS Windows Unix & Linux Memory Management DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating UNIX AND LINUX Systems I Evolution of LINUX Introduction DOS Windows Unix & Linux Memory Management DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating UNIX AND LINUX - Design goals Systems I Supporting software development I Keeping its algorithms as simple as possible Introduction DOS Windows Unix & Linux Memory Management DOS Windows Linux Process Management DOS Windows Linux bg=white Real Operating DOS MEMORY MANAGEMENT Systems I ROM and RAM Introduction DOS I ROM contains a section of BIOS for Windows starting up a computer Unix & Linux I RAM is mail memory where programs Memory are loaded Management DOS I Interrupt vectors Windows I BIOS interface Linux I DOS kernel Process Management I Buffer cache DOS I Installable drives Windows I Resident part of COMMAND.COM Linux I TSR I User memory I Transient part of COMMAND.COM I Reserved for BIOS bg=white Real Operating DOS MEMORY MANAGEMENT Systems I TPA allocation \policy" Introduction I Reason for allocating memory blocks in TPA for more DOS than one programs Windows I Improving efficiency when executing or accessing the Unix & Linux next program/file after executing one program Memory Management I \Policy" DOS I Dynamic allocation Windows Linux I Modification { modifying (normally giving more) memory blocks to a running program when it requires Process Management more for, e.g., I/O purposes DOS I Release of main memory{ after part of a program is Windows executed Linux I For .EXE files { allocating the max memory needed if TPA has enough free memory, otherwise, giving the min memory I For .COM files { allocating all memory it may need despite it will use or not bg=white Real Operating DOS MEMORY MANAGEMENT Systems I TPA allocation algorithms Introduction I First-fit was used in early version and Best-fit was used DOS in later version Windows I A block can be as small as 16 bytes (also known as Unix & Linux paragraph) and as large as the max available memory Memory Management (TPA) DOS I The first five bytes have special usage: Windows Linux I Byte 0 { indicator of the last block (90h if yes, 77h otherwise) Process Management I Byte 1{ indicator of status of the block (00h for busy) DOS I Byte 2 { pointer to PSP Windows I Bytes 3 and 4 { indicator of the number of paragraph Linux contained in the block I List of busy/free blocks I List is a data structure containing a head and a tail I An algorithm searches for a free block in the list for a file bg=white Real Operating WINDOWS MEMORY MANAGEMENT Systems I Memory manage challenge and solution I Challenge is to run programs written for Windows, DOS Introduction and POSIX without clashing each other in memory DOS Windows I Solution is to separate system memory and application Unix & Linux memory Memory I Example Management DOS I 4GB memory with 2GB each allocated for application Windows storage and system storage Linux Process Management DOS Windows Linux bg=white Real Operating WINDOWS MEMORY MANAGEMENT Systems I Virtual memory manager Introduction DOS I To allow applications
Load more

Recommended publications
  • A Survey on Architectures of Mobile Operating Systems: Challenges and Issues
    International Journal of Research Studies in Computer Science and Engineering (IJRSCSE) Volume 2, Issue 3, March 2015, PP 73-76 ISSN 2349-4840 (Print) & ISSN 2349-4859 (Online) www.arcjournals.org A Survey on Architectures of Mobile Operating Systems: Challenges and Issues Prof. Y. K. Sundara Krishna1 HOD, Dept. of Computer Science, Krishna University Mr. G K Mohan Devarakonda2 Research Scholar, Krishna University Abstract: In the early years of mobile evolution, Discontinued Platforms Current mobile devices are enabled only with voice services Platforms that allow the users to communicate with each other. Symbian OS Android But now a days, the mobile technology undergone Palm OS IOS various changes to a great extent so that the devices Maemo OS Windows Phone allows the users not only to communicate but also to Meego OS Firefox OS attain a variety of services such as video calls, faster Black Berry OS browsing services,2d and 3d games, Camera, 2.1 Symbian OS: This Operating system was Banking Services, GPS services, File sharing developed by NOKIA. services, Tracking Services, M-Commerce and so many. The changes in mobile technology may be due Architecture: to Operating System or Hardware or Network or Memory. This paper presents a survey on evolutions SYMBIAN OS GUI Library in mobile developments especially on mobile operating system Architectures, challenges and Issues in various mobile operating Systems. Application Engines JAVA VM 1. INTRODUCTION Servers (Operating System Services) A Mobile operating system is a System Software that is specifically designed to run on handheld devices Symbian OS Base (File Server, Kernel) such as Mobile Phones, PDA’s.
    [Show full text]
  • Virtual Memory
    Chapter 4 Virtual Memory Linux processes execute in a virtual environment that makes it appear as if each process had the entire address space of the CPU available to itself. This virtual address space extends from address 0 all the way to the maximum address. On a 32-bit platform, such as IA-32, the maximum address is 232 − 1or0xffffffff. On a 64-bit platform, such as IA-64, this is 264 − 1or0xffffffffffffffff. While it is obviously convenient for a process to be able to access such a huge ad- dress space, there are really three distinct, but equally important, reasons for using virtual memory. 1. Resource virtualization. On a system with virtual memory, a process does not have to concern itself with the details of how much physical memory is available or which physical memory locations are already in use by some other process. In other words, virtual memory takes a limited physical resource (physical memory) and turns it into an infinite, or at least an abundant, resource (virtual memory). 2. Information isolation. Because each process runs in its own address space, it is not possible for one process to read data that belongs to another process. This improves security because it reduces the risk of one process being able to spy on another pro- cess and, e.g., steal a password. 3. Fault isolation. Processes with their own virtual address spaces cannot overwrite each other’s memory. This greatly reduces the risk of a failure in one process trig- gering a failure in another process. That is, when a process crashes, the problem is generally limited to that process alone and does not cause the entire machine to go down.
    [Show full text]
  • Windows Command Prompt Cheatsheet
    Windows Command Prompt Cheatsheet - Command line interface (as opposed to a GUI - graphical user interface) - Used to execute programs - Commands are small programs that do something useful - There are many commands already included with Windows, but we will use a few. - A filepath is where you are in the filesystem • C: is the C drive • C:\user\Documents is the Documents folder • C:\user\Documents\hello.c is a file in the Documents folder Command What it Does Usage dir Displays a list of a folder’s files dir (shows current folder) and subfolders dir myfolder cd Displays the name of the current cd filepath chdir directory or changes the current chdir filepath folder. cd .. (goes one directory up) md Creates a folder (directory) md folder-name mkdir mkdir folder-name rm Deletes a folder (directory) rm folder-name rmdir rmdir folder-name rm /s folder-name rmdir /s folder-name Note: if the folder isn’t empty, you must add the /s. copy Copies a file from one location to copy filepath-from filepath-to another move Moves file from one folder to move folder1\file.txt folder2\ another ren Changes the name of a file ren file1 file2 rename del Deletes one or more files del filename exit Exits batch script or current exit command control echo Used to display a message or to echo message turn off/on messages in batch scripts type Displays contents of a text file type myfile.txt fc Compares two files and displays fc file1 file2 the difference between them cls Clears the screen cls help Provides more details about help (lists all commands) DOS/Command Prompt help command commands Source: https://technet.microsoft.com/en-us/library/cc754340.aspx.
    [Show full text]
  • Linux Physical Memory Analysis
    Linux Physical Memory Analysis Paul Movall International Business Machines Corporation 3605 Highway 52N, Rochester, MN Ward Nelson International Business Machines Corporation 3605 Highway 52N, Rochester, MN Shaun Wetzstein International Business Machines Corporation 3605 Highway 52N, Rochester, MN Abstract A significant amount of this information can alo be found in the /proc filesystem provided by the kernel. We present a tool suite for analysis of physical memory These /proc entries can be used to obtain many statis- usage within the Linux kernel environment. This tool tics including several related to memory usage. For ex- suite can be used to collect and analyze how the physi- ample, /proc/<pid>/maps can be used to display a pro- cal memory within a Linuxenvironment is being used. cess' virtual memory map. Likewise, the contents of / proc/<pid>/status can be used to retreive statistics about virtual memory usage as well as the Resident Set Size (RSS). Embedded subsystems are common in today's computer In most cases, this process level detail is sufficient to systems. These embedded subsystems range from the analyze memory usage. In systems that do not have very simple to the very complex. In such embedded sys- backing store, more details are often needed to analyze tems, memory is scarce and swap is non-existent. When memory usage. For example, it's useful to know which adapting Linux for use in this environment, we needed pages in a process' address map are resident, not just to keep a close eye on physical memory usage. how many. This information can be used to get some clues on the usage of a shared library.
    [Show full text]
  • Memory Protection at Option
    Memory Protection at Option Application-Tailored Memory Safety in Safety-Critical Embedded Systems – Speicherschutz nach Wahl Auf die Anwendung zugeschnittene Speichersicherheit in sicherheitskritischen eingebetteten Systemen Der Technischen Fakultät der Universität Erlangen-Nürnberg zur Erlangung des Grades Doktor-Ingenieur vorgelegt von Michael Stilkerich Erlangen — 2012 Als Dissertation genehmigt von der Technischen Fakultät Universität Erlangen-Nürnberg Tag der Einreichung: 09.07.2012 Tag der Promotion: 30.11.2012 Dekan: Prof. Dr.-Ing. Marion Merklein Berichterstatter: Prof. Dr.-Ing. Wolfgang Schröder-Preikschat Prof. Dr. Michael Philippsen Abstract With the increasing capabilities and resources available on microcontrollers, there is a trend in the embedded industry to integrate multiple software functions on a single system to save cost, size, weight, and power. The integration raises new requirements, thereunder the need for spatial isolation, which is commonly established by using a memory protection unit (MPU) that can constrain access to the physical address space to a fixed set of address regions. MPU-based protection is limited in terms of available hardware, flexibility, granularity and ease of use. Software-based memory protection can provide an alternative or complement MPU-based protection, but has found little attention in the embedded domain. In this thesis, I evaluate qualitative and quantitative advantages and limitations of MPU-based memory protection and software-based protection based on a multi-JVM. I developed a framework composed of the AUTOSAR OS-like operating system CiAO and KESO, a Java implementation for deeply embedded systems. The framework allows choosing from no memory protection, MPU-based protection, software-based protection, and a combination of the two.
    [Show full text]
  • Windows NT Architecture Previous Screen Gilbert Held Payoff Windows NT Is a Sophisticated Operating System for Workstations and Network Servers
    50-30-19 Windows NT Architecture Previous screen Gilbert Held Payoff Windows NT is a sophisticated operating system for workstations and network servers. This article helps network managers to understand the communications capability of workstations and servers running on Windows NT, and data base administrators to determine the suitability of this platform for a structured query language (SQL) data base server. Introduction Windows NT is a 32-bit, preemptive multitasking operating system that includes comprehensive networking capabilities and several levels of security. Microsoft markets two version of Windows NT: one for workstations—appropriately named Windows NT Workstation—and a second for servers—Windows NT Server. This article, which describes the workings of the NT architecture, collectively references both versions as Windows NT when information is applicable to both versions of the operating system. Similarly, it references a specific version of the operating system when the information presented is specific to either Windows NT Workstation or Windows NT Server. Architecture Windows NT consists of nine basic modules. The relationship of those modules to one another, as well as to the hardware platform on which the operating system runs, is illustrated in Exhibit 1. Windows NT Core Modules Hardware Abstraction Layer The hardware abstraction layer (HAL) is located directly above the hardware on which Windows NT operates. HAL actually represents a software module developed by hardware manufacturers that is bundled into Windows NT to allow it to operate on a specific hardware platform, such as Intel X86, DEC Alpha, or IBM PowerPC. HAL hides the specifics of the hardware platform from the rest of the operating system and represents the lowest level of Windows NT.
    [Show full text]
  • Mobile Systems
    CS 318 Principles of Operating Systems Fall 2017 Lecture 21: Mobile Systems Ryan Huang 11/30/17 CS 318 – Lecture 21 – Mobile Systems 2 Apply the security update immedidately! CS 318 – Lecture 21 – Mobile Systems Administrivia • Lab 4 deadline one week away • Groups of 2 students receive 2-day extra late hour • Groups of 3 students with 1 318 section student receive 1-day extra late-hour • Please, please don’t cheat • Homework 5 is released 11/30/17 CS 318 – Lecture 21 – Mobile Systems 4 Mobile Devices Become Ubiquitous Worldwide Devices Shipments by Device Type (Millions of Units) 3000 2500 2000 1500 1806.96 1879 1910 1959 1000 500 Google Nexus 6P 209.79 226 196 195 296.13 277 246 232 0 2013 2014 2015 2016 Traditional PCs Ultramobiles (Premium) Ultramobiles (Basic and Utility) Mobile Phones 5 History of Mobile OS (1) • Early “smart” devices are PDAs (touchscreen, Internet) • Symbian, first modern mobile OS - released in 2000 - run in Ericsson R380, the first ‘smartphone’ (mobile phone + PDA) - only support proprietary programs 11/30/17 CS 318 – Lecture 21 – Mobile Systems 6 History of Mobile OS (2) • Many smartphone and mobile OSes followed up - Kyocera 6035 running Palm OS (2001) • 8 MB non-expandable memory - Windows CE (2002) - Blackberry (2002) • was a prominent vendor • known for secure communications - Moto Q (2005) - Nokia N70 (2005) • 2-megapixel camera, bluetooth • 32 MB memory • Symbian OS • Java games 11/30/17 CS 318 – Lecture 21 – Mobile Systems 7 One More Thing… • Introduction of iPhone (2007) - revolutionize the smartphone industry - 4GB flash memory, 128 MB DRAM, multi-touch interface - runs iOS, initially only proprietary apps - App Store opened in 2008, allow third party apps 11/30/17 CS 318 – Lecture 21 – Mobile Systems 8 Android – An Unexpected Rival of iPhone • Android Inc.
    [Show full text]
  • Windows XP History and Versions
    Lecture 23: Windows XP History and Versions n Mid-80ies Microsoft and IBM cooperated to develop OS/2 n Windows XP is produced by Microsoft Co. n 1988 - Microsoft started to develop its own new technology (NT) OS n XP is multi-user, multi-process, preemptive multitasking OS, 30M lines of source code capable of running OS/2, Windows and Unix apps. Hired Dave Cutler - architect of DEC VAX/VMS to head the design n It is developed to support multiple platforms and targeted towards enterprise workstations and server market as well as n NT v. 3.1 first released commercially July 1993 desktops n NT v 4.0 adopted Windows 95 user interface, graphics code moved into kernel to improve performance n In today’s lecture n 2000 – improved networking and laptop support, support for plug-and- u XP’s predecessors, the history of XP design, XP versions play devices, support for more processors (up to 8) and memory, u design principles becomes true multi-user through terminal server u components n XP (released Oct 2001) – update for 2000 replacement for 95/98 F hardware abstraction layer u simplifies user interface, improved reliability, performance F executive improvements, partial 64-bit support F environmental subsystems n versions F file system u desktop: XP personal – 95/98 replacement, professional – advanced features like POSIX support, some network features 1 u server: .NET – support for web/print service, clusters, large memory2 and multiple processors Design goals Components n XP is microkernel-based, modular n security – NT was C-2 certified (US
    [Show full text]
  • Introduction to MS-DOS
    1.Introduction to MS-DOS : MS-DOS (Microsoft Disk Operating System) was the Microsoft-marketed version of the first widely-installed operating system in personal computers. It was essentially the same operating system that (Bill Gates's) young company developed for IBM as Personal Computer - Disk Operating System in 1981. Most users of either DOS system simply referred to their system as Disk Operating System. Like PC-DOS, MS-DOS was (and still is) a non-graphical line-oriented command- driven operating system, with a relatively simple interface but not overly "friendly" user interface. Its prompt to enter a command looks like this: C:\> MS-DOS does not care about anything called an icon, wallpaper or screen saver. Rather than being considered as a Graphical User Interface (GUI) MS-DOS is what is known as a command-line interface. You type commands on what is called the command line. MS-DOS is a single-user, single-tasking computer operating system. In spite of its very small size and relative simplicity, it is one of the most successful operating systems that has been developed to date. In DOS, a file name consists of eight character followed by a 3 character file extension. The size of a file is restricted to a 4 byte file descriptor, which limits a file’s maximum size to approximately 4 billion characters. The first release of DOS could not read or write to disk drives so users could only read and write to a floppy disc. DOS was not a state of the art operating system, even for its time.
    [Show full text]
  • Chapter 1. Origins of Mac OS X
    1 Chapter 1. Origins of Mac OS X "Most ideas come from previous ideas." Alan Curtis Kay The Mac OS X operating system represents a rather successful coming together of paradigms, ideologies, and technologies that have often resisted each other in the past. A good example is the cordial relationship that exists between the command-line and graphical interfaces in Mac OS X. The system is a result of the trials and tribulations of Apple and NeXT, as well as their user and developer communities. Mac OS X exemplifies how a capable system can result from the direct or indirect efforts of corporations, academic and research communities, the Open Source and Free Software movements, and, of course, individuals. Apple has been around since 1976, and many accounts of its history have been told. If the story of Apple as a company is fascinating, so is the technical history of Apple's operating systems. In this chapter,[1] we will trace the history of Mac OS X, discussing several technologies whose confluence eventually led to the modern-day Apple operating system. [1] This book's accompanying web site (www.osxbook.com) provides a more detailed technical history of all of Apple's operating systems. 1 2 2 1 1.1. Apple's Quest for the[2] Operating System [2] Whereas the word "the" is used here to designate prominence and desirability, it is an interesting coincidence that "THE" was the name of a multiprogramming system described by Edsger W. Dijkstra in a 1968 paper. It was March 1988. The Macintosh had been around for four years.
    [Show full text]
  • HALO: Post-Link Heap-Layout Optimisation
    HALO: Post-Link Heap-Layout Optimisation Joe Savage Timothy M. Jones University of Cambridge, UK University of Cambridge, UK [email protected] [email protected] Abstract 1 Introduction Today, general-purpose memory allocators dominate the As the gap between memory and processor speeds continues landscape of dynamic memory management. While these so- to widen, efficient cache utilisation is more important than lutions can provide reasonably good behaviour across a wide ever. While compilers have long employed techniques like range of workloads, it is an unfortunate reality that their basic-block reordering, loop fission and tiling, and intelligent behaviour for any particular workload can be highly subop- register allocation to improve the cache behaviour of pro- timal. By catering primarily to average and worst-case usage grams, the layout of dynamically allocated memory remains patterns, these allocators deny programs the advantages of largely beyond the reach of static tools. domain-specific optimisations, and thus may inadvertently Today, when a C++ program calls new, or a C program place data in a manner that hinders performance, generating malloc, its request is satisfied by a general-purpose allocator unnecessary cache misses and load stalls. with no intimate knowledge of what the program does or To help alleviate these issues, we propose HALO: a post- how its data objects are used. Allocations are made through link profile-guided optimisation tool that can improve the fixed, lifeless interfaces, and fulfilled by
    [Show full text]
  • Security in Ordinary Operating Systems
    39 C H A P T E R 4 Security in Ordinary Operating Systems In considering the requirements of a secure operating system,it is worth considering how far ordinary operating systems are from achieving these requirements. In this chapter, we examine the UNIX and Windows operating systems and show why they are fundamentally not secure operating systems. We first examine the history these systems, briefly describe their protection systems, then we show, using the requirements of a secure operating system defined in Chapter 2, why ordinary operating systems are inherently insecure. Finally, we examine common vulnerabilities in these systems to show the need for secure operating systems and the types of threats that they will have to overcome. 4.1 SYSTEM HISTORIES 4.1.1 UNIX HISTORY UNIX is a multiuser operating system developed by Dennis Ritchie and Ken Thompson at AT&T Bell Labs [266]. UNIX started as a small project to build an operating system to play a game on an available PDP-7 computer. However, UNIX grew over the next 10 to 15 years into a system with considerable mindshare, such that a variety of commercial UNIX efforts were launched. The lack of coherence in these efforts may have limited the market penetration of UNIX, but many vendors, even Microsoft, had their own versions. UNIX remains a significant operating system today, embodied in many systems, such as Linux, Sun Solaris, IBM AIX, the various BSD systems, etc. Recall from Chapter 3 that Bell Labs was a member of the Multics consortium. However, Bell Labs dropped out of the Multics project in 1969, primarily due to delays in the project.
    [Show full text]