How to Implement Lightweight Threads
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A Practical UNIX Capability System
A Practical UNIX Capability System Adam Langley <[email protected]> 22nd June 2005 ii Abstract This report seeks to document the development of a capability security system based on a Linux kernel and to follow through the implications of such a system. After defining terms, several other capability systems are discussed and found to be excellent, but to have too high a barrier to entry. This motivates the development of the above system. The capability system decomposes traditionally monolithic applications into a number of communicating actors, each of which is a separate process. Actors may only communicate using the capabilities given to them and so the impact of a vulnerability in a given actor can be reasoned about. This design pattern is demonstrated to be advantageous in terms of security, comprehensibility and mod- ularity and with an acceptable performance penality. From this, following through a few of the further avenues which present themselves is the two hours traffic of our stage. Acknowledgments I would like to thank my supervisor, Dr Kelly, for all the time he has put into cajoling and persuading me that the rest of the world might have a trick or two worth learning. Also, I’d like to thank Bryce Wilcox-O’Hearn for introducing me to capabilities many years ago. Contents 1 Introduction 1 2 Terms 3 2.1 POSIX ‘Capabilities’ . 3 2.2 Password Capabilities . 4 3 Motivations 7 3.1 Ambient Authority . 7 3.2 Confused Deputy . 8 3.3 Pervasive Testing . 8 3.4 Clear Auditing of Vulnerabilities . 9 3.5 Easy Configurability . -
Tutorials Point, Simply Easy Learning
Tutorials Point, Simply Easy Learning UML Tutorial Tutorialspoint.com UNIX is a computer Operating System which is capable of handling activities from multiple users at the same time. Unix was originated around in 1969 at AT&T Bell Labs by Ken Thompson and Dennis Ritchie. This tutorial gives an initial push to start you with UNIX. For more detail kindly check tutorialspoint.com/unix What is Unix ? The UNIX operating system is a set of programs that act as a link between the computer and the user. The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel. Users communicate with the kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel. Unix was originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. There are various Unix variants available in the market. Solaris Unix, AIX, UP Unix and BSD are few examples. Linux is also a flavour of Unix which is freely available. Several people can use a UNIX computer at the same time; hence UNIX is called a multiuser system. A user can also run multiple programs at the same time; hence UNIX is called multitasking. Unix Architecture: Here is a basic block diagram of a UNIX system: 1 | P a g e Tutorials Point, Simply Easy Learning The main concept that unites all versions of UNIX is the following four basics: Kernel: The kernel is the heart of the operating system. -
Ultimate++ Forum Probably with These Two Variables You Could Try to Integrate D-BUS
Subject: DBus integration -- need help Posted by jlfranks on Thu, 20 Jul 2017 15:30:07 GMT View Forum Message <> Reply to Message We are trying to add a DBus server to existing large U++ application that runs only on Linux. I've converted from X11 to GTK for Upp project config to be compatible with GIO dbus library. I've created a separate thread for the DBus server and ran into problems with event loop. I've gutted my DBus server code of everything except what is causing an issue. DBus GIO examples use GMainLoop in order for DBus to service asynchronous events. Everything compiles and runs except the main UI is not longer visible. There must be a GTK main loop already running and I've stepped on it with this code. Is there a way for me to obtain a pointer to the UI main loop and use it with my DBus server? How/where can I do that? Code snipped example as follows: ---- code snippet ---- myDBusServerMainThread() { //========================================================== ===== // // Enter main service loop for this thread // while (not needsExit ()) { // colaborate with join() GMainLoop *loop; loop = g_main_loop_new(NULL, FALSE); g_main_loop_run(loop); } } Subject: Re: DBus integration -- need help Posted by Klugier on Thu, 20 Jul 2017 22:30:17 GMT View Forum Message <> Reply to Message Hello, You could try use following methods of Ctrl to obtain gtk & gdk handlers: GdkWindow *gdk() const { return top ? top->window->window : NULL; } GtkWindow *gtk() const { return top ? (GtkWindow *)top->window : NULL; } Page 1 of 3 ---- Generated from Ultimate++ forum Probably with these two variables you could try to integrate D-BUS. -
Fundamentals of Xlib Programming by Examples
Fundamentals of Xlib Programming by Examples by Ross Maloney Contents 1 Introduction 1 1.1 Critic of the available literature . 1 1.2 The Place of the X Protocol . 1 1.3 X Window Programming gotchas . 2 2 Getting started 4 2.1 Basic Xlib programming steps . 5 2.2 Creating a single window . 5 2.2.1 Open connection to the server . 6 2.2.2 Top-level window . 7 2.2.3 Exercises . 10 2.3 Smallest Xlib program to produce a window . 10 2.3.1 Exercises . 10 2.4 A simple but useful X Window program . 11 2.4.1 Exercises . 12 2.5 A moving window . 12 2.5.1 Exercises . 15 2.6 Parts of windows can disappear from view . 16 2.6.1 Testing overlay services available from an X server . 17 2.6.2 Consequences of no server overlay services . 17 2.6.3 Exercises . 23 2.7 Changing a window’s properties . 23 2.8 Content summary . 25 3 Windows and events produce menus 26 3.1 Colour . 26 3.1.1 Exercises . 27 i CONTENTS 3.2 A button to click . 29 3.3 Events . 33 3.3.1 Exercises . 37 3.4 Menus . 37 3.4.1 Text labelled menu buttons . 38 3.4.2 Exercises . 43 3.5 Some events of the mouse . 44 3.6 A mouse behaviour application . 55 3.6.1 Exercises . 58 3.7 Implementing hierarchical menus . 58 3.7.1 Exercises . 67 3.8 Content summary . 67 4 Pixmaps 68 4.1 The pixmap resource . -
Unit V Algorithm for Booting the UNIX System
Unit V Algorithm for booting the UNIX system : As we’ve noted, the boot process begins when the instructions stored in the computer’s permanent, nonvolatile memory (referred to colloquially as the BIOS, ROM,NVRAM, and so on) are executed. This storage location for the initial boot instructions is generically referred to as firmware (in contrast to “software,” but reflecting the fact that the instructions constitute a program[2]). These instructions are executed automatically when the power is turned on or the system is reset, although the exact sequence of events may vary according to the values of stored parameters.[3] The firmware instructions may also begin executing in response to a command entered on the system console (as we’ll see in a bit). However they are initiated, these instructions are used to locate and start up the system’s boot program , which in turn starts the Unix operating system. The boot program is stored in a standard location on a bootable device. For a normal boot from disk, for example, the boot program might be located in block 0 of the root disk or, less commonly, in a special partition on the root disk. In the same way, the boot program may be the second file on a bootable tape or in a designated location on a remote file server in the case of a network boot of a diskless workstation. There is usually more than one bootable device on a system. The firmware program may include logic for selecting the device to boot from, often in the form of a list of potential devices to examine. -
Introduction to Asynchronous Programming
Introduction to Asynchronous Programming In this document we introduce an asynchronous model for concurrent programming. For certain appli- cations, an asynchronous model may yield performance benefits over traditional multithreading. Much of the material presented in this document is taken from Dave Peticola’s excellent introduction to Twisted1, a Python framework for asynchronous programming. 1 The Models We will start by reviewing two (hopefully) familiar models in order to contrast them with the asynchronous model. By way of illustration we will imagine a program that consists of three conceptually distinct tasks which must be performed to complete the program. Note I am using task in the non-technical sense of something that needs to be done. The first model we will look at is the single-threaded synchronous model, in Figure 1 below: Figure 1: The single-threaded synchronous model This is the simplest style of programming. Each task is performed one at a time, with one finishing completely before another is started. And if the tasks are always performed in a definite order, the imple- mentation of a later task can assume that all earlier tasks have finished without errors, with all their output available for use — a definite simplification in logic. We can contrast the single-threaded synchronous model with the multi-threaded synchronous model illustrated in Figure 2. In this model, each task is performed in a separate thread of control. The threads are managed by the operating system and may, on a system with multiple processors or multiple cores, run truly concurrently, 1http://krondo.com/?page_id=1327 1 CS168 Async Programming Figure 2: The threaded model or may be interleaved together on a single processor. -
Thread Scheduling in Multi-Core Operating Systems Redha Gouicem
Thread Scheduling in Multi-core Operating Systems Redha Gouicem To cite this version: Redha Gouicem. Thread Scheduling in Multi-core Operating Systems. Computer Science [cs]. Sor- bonne Université, 2020. English. tel-02977242 HAL Id: tel-02977242 https://hal.archives-ouvertes.fr/tel-02977242 Submitted on 24 Oct 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Ph.D thesis in Computer Science Thread Scheduling in Multi-core Operating Systems How to Understand, Improve and Fix your Scheduler Redha GOUICEM Sorbonne Université Laboratoire d’Informatique de Paris 6 Inria Whisper Team PH.D.DEFENSE: 23 October 2020, Paris, France JURYMEMBERS: Mr. Pascal Felber, Full Professor, Université de Neuchâtel Reviewer Mr. Vivien Quéma, Full Professor, Grenoble INP (ENSIMAG) Reviewer Mr. Rachid Guerraoui, Full Professor, École Polytechnique Fédérale de Lausanne Examiner Ms. Karine Heydemann, Associate Professor, Sorbonne Université Examiner Mr. Etienne Rivière, Full Professor, University of Louvain Examiner Mr. Gilles Muller, Senior Research Scientist, Inria Advisor Mr. Julien Sopena, Associate Professor, Sorbonne Université Advisor ABSTRACT In this thesis, we address the problem of schedulers for multi-core architectures from several perspectives: design (simplicity and correct- ness), performance improvement and the development of application- specific schedulers. -
Qcontext, and Supporting Multiple Event Loop Threads in QEMU
IBM Linux Technology Center QContext, and Supporting Multiple Event Loop Threads in QEMU Michael Roth [email protected] © 2006 IBM Corporation IBM Linux Technology Center QEMU Threading Model Overview . Historically (earlier this year), there were 2 main types of threads in QEMU: . vcpu threads – handle execution of guest code, and emulation of hardware access (pio/mmio) and other trapped instructions . QEMU main loop (iothread) – everything else (mostly) GTK/SDL/VNC UIs QMP/HMP management interfaces Clock updates/timer callbacks for devices device I/O on behalf of vcpus © 2006 IBM Corporation IBM Linux Technology Center QEMU Threading Model Overview . All core qemu code protected by global mutex . vcpu threads in KVM_RUN can run concurrently thanks to address space isolation, but attempt to acquire global mutex immediately after an exit . Iothread requires global mutex whenever it's active © 2006 IBM Corporation IBM Linux Technology Center High contention as threads or I/O scale vcpu 1 vcpu 2 vcpu n iothread . © 2006 IBM Corporation IBM Linux Technology Center QEMU Thread Types . vcpu threads . iothread . virtio-blk-dataplane thread Drives a per-device AioContext via aio_poll Handles event fd callbacks for virtio-blk virtqueue notifications and linux_aio completions Uses port of vhost's vring code, doesn't (currently) use core QEMU code, doesn't require global mutex Will eventually re-use QEMU block layer code © 2006 IBM Corporation IBM Linux Technology Center QEMU Block Layer Features . Multiple image format support . Snapshots . Live Block Copy . Live Block migration . Drive-mirroring . Disk I/O limits . Etc... © 2006 IBM Corporation IBM Linux Technology Center More dataplane in the future . -
The Design and Use of the ACE Reactor an Object-Oriented Framework for Event Demultiplexing
The Design and Use of the ACE Reactor An Object-Oriented Framework for Event Demultiplexing Douglas C. Schmidt and Irfan Pyarali g fschmidt,irfan @cs.wustl.edu Department of Computer Science Washington University, St. Louis 631301 1 Introduction create concrete event handlers by inheriting from the ACE Event Handler base class. This class specifies vir- This article describes the design and implementation of the tual methods that handle various types of events, such as Reactor pattern [1] contained in the ACE framework [2]. The I/O events, timer events, signals, and synchronization events. Reactor pattern handles service requests that are delivered Applications that use the Reactor framework create concrete concurrently to an application by one or more clients. Each event handlers and register them with the ACE Reactor. service of the application is implemented by a separate event Figure 1 shows the key components in the ACE Reactor. handler that contains one or more methods responsible for This figure depicts concrete event handlers that implement processing service-specific requests. In the implementation of the Reactor pattern described in this paper, event handler dispatching is performed REGISTERED 2: accept() by an ACE Reactor.TheACE Reactor combines OBJECTS 5: recv(request) 3: make_handler() the demultiplexing of input and output (I/O) events with 6: process(request) other types of events, such as timers and signals. At Logging Logging Logging Logging Handler Acceptor LEVEL thecoreoftheACE Reactor implementation is a syn- LEVEL Handler Handler chronous event demultiplexer, such as select [3] or APPLICATION APPLICATION Event Event WaitForMultipleObjects [4]. When the demulti- Event Event Handler Handler Handler plexer indicates the occurrence of designated events, the Handler ACE Reactor automatically dispatches the method(s) of 4: handle_input() 1: handle_input() pre-registered event handlers, which perform application- specified services in response to the events. -
Embedded Systems Supporting by Different Operating Systems
A Survey: Embedded Systems Supporting By Different Operating Systems Qamar Jabeen, Fazlullah Khan, Muhammad Tahir, Shahzad Khan, Syed Roohullah Jan Department of Computer Science, Abdul Wali Khan University Mardan [email protected], [email protected] -------------------------------------------------------------------------------------------------------------------------------------- Abstract: In these days embedded systems used in industrial, commercial system have an important role in different areas. e.g Mobile Phones and different Fields and applications like Network type of Network Bridges are embedded embedded system , Real-time embedded used by telecommunication systems for systems which supports the mission- giving better requirements to their users. critical domains, mostly having the time We use digital cameras, MP3 players, DVD constraints, Stand-alone systems which players are the example of embedded includes the network router etc. A great consumer electronics. In our daily life its deployment in the processors made for provided us efficiency and flexibility and completing the demanding needs of the many features which includes microwave users. There is also a large-scale oven, washing machines dishwashers. deployment occurs in sensor networks for Embedded system are also used in providing the advance facilities, for medical, transportation and also used in handled such type of embedded systems wireless sensor network area respectively a specific operating system must provide. medical imaging, vital signs, automobile This paper presents some software electric vehicles and Wi-Fi modules. infrastructures that have the ability of supporting such types of embedded systems. 1. Introduction: Embedded system are computer systems designed for specific purpose, to increase functionality and reliability for achieving a specific task, like general Figure 1: Taxonomy of Embedded Software’s purpose computer system it does not use for multiple tasks. -
Events Vs. Threads COS 316: Principles of Computer System Design
Events vs. Threads COS 316: Principles of Computer System Design Amit Levy & Wyatt Lloyd Two Abstractions for Supporting Concurrency Problem: computationally light applications with large state-space ● How to support graphical interfaces with many possible interactions in each state? ● How to scale servers to handle many simultaneous requests? Corollary: how do we best utilize the CPU in I/O-bound workloads? ● Ideally, CPU should not be a bottleneck for saturating I/O Threads Event Event Event Event Event Wait for event Wait for event Wait for event ... Wait for event Wait for event Wait for event ... Wait for event Wait for event Wait for event ... Threads ● One thread per sequence of related I/O operations ○ E.g. one thread per client TCP connection ● When next I/O isn’t ready, block thread until it is ○ i.e. return to event handler instead of blocking for next event ● State machine is implicit in the sequential program ○ E.g., parse HTTP request, then send DB query, then read file from disk, then send HTTP response ● Only keeping track of relevant next I/O operations ● Any shared state must be synchronized ○ E.g. with locks, channels, etc ● In theory, scale by having a thread per connection Events Event Event Event Event Event Handle event kind A Wait for any event Handle event kind B Events ● Single “event-loop” waits for the next event (of any kind) ● When event arrives, handle it “to completion” ○ i.e. return to event handler instead of blocking for next event ● Event loop keeps track of state machine explicitly ○ How to handle an event depends on which state I’m in ○ E.g. -
Qt Event Loop, Networking and I/O API
Qt event loop, networking and I/O API Thiago Macieira, Qt Core Maintainer San Francisco, November 2013 Who am I? • Open Source developer for 15 years • C++ developer for 13 years • Software Architect at Intel’s Open Source Technology Center (OTC) • Maintainer of two modules in the Qt Project ‒ QtCore and QtDBus • MBA and double degree in Engineering • Previously, led the “Qt Open Governance” project 2 © 2013 Intel Agenda • The event loop • Event loops and threads • Networking and I/O 3 © 2013 Intel The Event Loop Classes relating to the event loop • QAbstractEventDispatcher • QEventLoop • QCoreApplication • QTimer & QBasicTimer • QSocketNotifier & QWinEventNotifer • QThread 5 © 2013 Intel What an event loop does • While !interrupted: • If there are new events, dispatch them • Wait for more events • Event loops are the inner core of modern applications ‒ Headless servers and daemons, GUI applications, etc. ‒ Everything but shell tools and file-processing tools 6 © 2013 Intel Qt event loop feature overview • Receives and translates GUI • Integrates with: events ‒ Generic Unix select(2) ‒ NSEvents (on Mac) ‒ Glib ‒ MSG (on Windows) ‒ Mac’s CFRunLoop ‒ BPS events (on Blackberry) ‒ Windows’s WaitForMultipleObjects ‒ X11 events (using XCB) • Services timers ‒ Wayland events ‒ With coarse timer support ‒ Many others • Polls sockets • Manages the event queue (priority queue) • Polls Windows events • Allows for event filtering • Thread-safe waking up 7 © 2013 Intel QAbstractEventDispatcher • Each thread has one instance • Only of interest if you’re