Processes and System Calls
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The Linux Kernel Module Programming Guide
The Linux Kernel Module Programming Guide Peter Jay Salzman Michael Burian Ori Pomerantz Copyright © 2001 Peter Jay Salzman 2007−05−18 ver 2.6.4 The Linux Kernel Module Programming Guide is a free book; you may reproduce and/or modify it under the terms of the Open Software License, version 1.1. You can obtain a copy of this license at http://opensource.org/licenses/osl.php. This book is distributed in the hope it will be useful, but without any warranty, without even the implied warranty of merchantability or fitness for a particular purpose. The author encourages wide distribution of this book for personal or commercial use, provided the above copyright notice remains intact and the method adheres to the provisions of the Open Software License. In summary, you may copy and distribute this book free of charge or for a profit. No explicit permission is required from the author for reproduction of this book in any medium, physical or electronic. Derivative works and translations of this document must be placed under the Open Software License, and the original copyright notice must remain intact. If you have contributed new material to this book, you must make the material and source code available for your revisions. Please make revisions and updates available directly to the document maintainer, Peter Jay Salzman <[email protected]>. This will allow for the merging of updates and provide consistent revisions to the Linux community. If you publish or distribute this book commercially, donations, royalties, and/or printed copies are greatly appreciated by the author and the Linux Documentation Project (LDP). -
Writing Your First Linux Kernel Module
Writing your first Linux kernel module Praktikum Kernel Programming University of Hamburg Scientific Computing Winter semester 2014/2015 Outline ● Before you start ● Hello world module ● Compile, load and unload ● User space VS. kernel space programing ● Summary Before you start ● Define your module’s goal ● Define your module behaviour ● Know your hardware specifications ○ If you are building a device driver you should have the manual ● Documentation ○ /usr/src/linux/Documentation ○ make { htmldocs | psdocs | pdfdocks | rtfdocks } ○ /usr/src/linux/Documentation/DocBook Role of the device driver ● Software layer between application and device “black boxes” ○ Offer abstraction ■ Make hardware available to users ○ Hide complexity ■ User does not need to know their implementation ● Provide mechanism not policy ○ Mechanism ■ Providing the flexibility and the ability the device supports ○ Policy ■ Controlling how these capabilities are being used Role of the device driver ● Policy-free characteristics ○ Synchronous and asynchronous operations ○ Exploit the full capabilities of the hardware ○ Often a client library is provided as well ■ Provides capabilities that do not need to be implemented inside the module Outline ● Before you start ● Hello world module ● Compile, load and unload ● User space VS. kernel space programing ● Summary Hello world module /* header files */ #include <linux/module.h> #include <linux/init.h> /* the initialization function */ /* the shutdown function */ static int __init hello_init(void) { static void __exit hello_exit(void) -
Name Synopsis Description
Perl version 5.10.0 documentation - vmsish NAME vmsish - Perl pragma to control VMS-specific language features SYNOPSIS use vmsish; use vmsish 'status';# or '$?' use vmsish 'exit'; use vmsish 'time'; use vmsish 'hushed'; no vmsish 'hushed'; vmsish::hushed($hush); use vmsish; no vmsish 'time'; DESCRIPTION If no import list is supplied, all possible VMS-specific features areassumed. Currently, there are four VMS-specific features available:'status' (a.k.a '$?'), 'exit', 'time' and 'hushed'. If you're not running VMS, this module does nothing. vmsish status This makes $? and system return the native VMS exit statusinstead of emulating the POSIX exit status. vmsish exit This makes exit 1 produce a successful exit (with status SS$_NORMAL),instead of emulating UNIX exit(), which considers exit 1 to indicatean error. As with the CRTL's exit() function, exit 0 is also mappedto an exit status of SS$_NORMAL, and any other argument to exit() isused directly as Perl's exit status. vmsish time This makes all times relative to the local time zone, instead of thedefault of Universal Time (a.k.a Greenwich Mean Time, or GMT). vmsish hushed This suppresses printing of VMS status messages to SYS$OUTPUT andSYS$ERROR if Perl terminates with an error status. and allowsprograms that are expecting "unix-style" Perl to avoid having to parseVMS error messages. It does not suppress any messages from Perlitself, just the messages generated by DCL after Perl exits. The DCLsymbol $STATUS will still have the termination status, but with ahigh-order bit set: EXAMPLE:$ perl -e"exit 44;" Non-hushed error exit%SYSTEM-F-ABORT, abort DCL message$ show sym $STATUS$STATUS == "%X0000002C" $ perl -e"use vmsish qw(hushed); exit 44;" Hushed error exit $ show sym $STATUS $STATUS == "%X1000002C" The 'hushed' flag has a global scope during compilation: the exit() ordie() commands that are compiled after 'vmsish hushed' will be hushedwhen they are executed. -
A Concurrent PASCAL Compiler for Minicomputers
512 Appendix A DIFFERENCES BETWEEN UCSD'S PASCAL AND STANDARD PASCAL The PASCAL language used in this book contains most of the features described by K. Jensen and N. Wirth in PASCAL User Manual and Report, Springer Verlag, 1975. We refer to the PASCAL defined by Jensen and Wirth as "Standard" PASCAL, because of its widespread acceptance even though no international standard for the language has yet been established. The PASCAL used in this book has been implemented at University of California San Diego (UCSD) in a complete software system for use on a variety of small stand-alone microcomputers. This will be referred to as "UCSD PASCAL", which differs from the standard by a small number of omissions, a very small number of alterations, and several extensions. This appendix provides a very brief summary Of these differences. Only the PASCAL constructs used within this book will be mentioned herein. Documents are available from the author's group at UCSD describing UCSD PASCAL in detail. 1. CASE Statements Jensen & Wirth state that if there is no label equal to the value of the case statement selector, then the result of the case statement is undefined. UCSD PASCAL treats this situation by leaving the case statement normally with no action being taken. 2. Comments In UCSD PASCAL, a comment appears between the delimiting symbols "(*" and "*)". If the opening delimiter is followed immediately by a dollar sign, as in "(*$", then the remainder of the comment is treated as a directive to the compiler. The only compiler directive mentioned in this book is (*$G+*), which tells the compiler to allow the use of GOTO statements. -
System Calls
System Calls What are they? ● Standard interface to allow the kernel to safely handle user requests – Read from hardware – Spawn a new process – Get current time – Create shared memory ● Message passing technique between – OS kernel (server) – User (client) Executing System Calls ● User program issues call ● Core kernel looks up call in syscall table ● Kernel module handles syscall action ● Module returns result of system call ● Core kernel forwards result to user Module is not Loaded... ● User program issues call ● Core kernel looks up call in syscall table ● Kernel module isn't loaded to handle action ● ... ● Where does call go? System Call Wrappers ● Wrapper calls system call if loaded – Otherwise returns an error ● Needs to be in a separate location so that the function can actually be called – Uses function pointer to point to kernel module implementation Adding System Calls ● You'll need to add and implement: – int start_elevator(void); – int issue_request(int, int, int); – int stop_elevator(void); ● As an example, let's add a call to printk an argument passed in: – int test_call(int); Adding System Calls ● Files to add (project files): – /usr/src/test_kernel/hello_world/test_call.c – /usr/src/test_kernel/hello_world/hello.c – /usr/src/test_kernel/hello_world/Makefile ● Files to modify (core kernel): – /usr/src/test_kernel/arch/x86/entry/syscalls/syscall_64.tbl – /usr/src/test_kernel/include/linux/syscalls.h – /usr/src/test_kernel/Makefile hello_world/test_call.c ● #include <linux/linkage.h> ● #include <linux/kernel.h> ● #include -
Shell Code for Beginners
Shell Code For Beginners Beenu Arora Site: www.BeenuArora.com Email: [email protected] ################################################################ # .___ __ _______ .___ # # __| _/____ _______| | __ ____ \ _ \ __| _/____ # # / __ |\__ \\_ __ \ |/ // ___\/ /_\ \ / __ |/ __ \ # # / /_/ | / __ \| | \/ <\ \___\ \_/ \/ /_/ \ ___/ # # \____ |(______/__| |__|_ \\_____>\_____ /\_____|\____\ # # \/ \/ \/ # # ___________ ______ _ __ # # _/ ___\_ __ \_/ __ \ \/ \/ / # # \ \___| | \/\ ___/\ / # # \___ >__| \___ >\/\_/ # # est.2007 \/ \/ forum.darkc0de.com # ################################################################ What is a shell Code? Shellcode is defined as a set of instructions injected and then executed by an exploited program. Shellcode is used to directly manipulate registers and the functionality of a exploited program. We can of course write shell codes in the high level language but would let you know later why they might not work for some cases, so assembly language is preferred for this. I would take an clean example of the exit() syscall used for exiting from a program. Many of you might be wondered to see why this being used is, the reason is the newer kernel don’t allow anymore the code execution from the stack so we have to use some C library wrapper or libc (responsible for providing us the malloc function). Usage at darker site: We write shellcode because we want the target program to function in a manner other than what was intended by the designer. One way to manipulate the program is to force it to make a system call or syscall. System calls in Linux are accomplished via software interrupts and are called with the int 0x80 instruction. -
Programming Project 5: User-Level Processes
Project 5 Operating Systems Programming Project 5: User-Level Processes Due Date: ______________________________ Project Duration: One week Overview and Goal In this project, you will explore user-level processes. You will create a single process, running in its own address space. When this user-level process executes, the CPU will be in “user mode.” The user-level process will make system calls to the kernel, which will cause the CPU to switch into “system mode.” Upon completion, the CPU will switch back to user mode before resuming execution of the user-level process. The user-level process will execute in its own “logical address space.” Its address space will be broken into a number of “pages” and each page will be stored in a frame in memory. The pages will be resident (i.e., stored in frames in physical memory) at all times and will not be swapped out to disk in this project. (Contrast this with “virtual” memory, in which some pages may not be resident in memory.) The kernel will be entirely protected from the user-level program; nothing the user-level program does can crash the kernel. Download New Files The files for this project are available in: http://www.cs.pdx.edu/~harry/Blitz/OSProject/p5/ Please retain your old files from previous projects and don’t modify them once you submit them. You should get the following files: Switch.s Runtime.s System.h System.c Page 1 Project 5 Operating Systems List.h List.c BitMap.h BitMap.c makefile FileStuff.h FileStuff.c Main.h Main.c DISK UserRuntime.s UserSystem.h UserSystem.c MyProgram.h MyProgram.c TestProgram1.h TestProgram1.c TestProgram2.h TestProgram2.c The following files are unchanged from the last project and you should not modify them: Switch.s Runtime.s System.h System.c -- except HEAP_SIZE has been modified List.h List.c BitMap.h BitMap.c The following files are not provided; instead you will modify what you created in the last project. -
An Introduction to Python
An Introduction to Python Day 1 Simon Mitchell [email protected] Why Python? * Clear code * Great beginner language * Powerful text manipulation * Wrangle large data files * Great compliment to other languages * Large user group * Supports many advanced features Warning: Spacing is important! Wrong: Error: Correct: No Error: Open A Terminal * Open a terminal: * Mac: cmd + space then type terminal and press enter * Windows: Start -> Program Files -> Accessories -> Command Prompt. * Type “python” (no quotes). Exit() to exit python. This is python Hello World Launch python Call the built in function print, which displays whatever comes after the command. Put any message in quotes after the print command. The command has finished and python is ready for the next command. >>> means tell me what to do now! Getting help - interactive Getting help – single command But usually just Google! If you got stuck on something, someone else probably has. Let’s get programming - Variables Set a variable with equals Display a variable by typing its name Variables can be text, numbers, boolean (True/ False) and many more things. Capitalization is important for True/ False Numeric Operators Add + Subtract – Multiply * Divide / Power ** Modulo (remainder) % Reassigning Variables Reassign with equals. (Same as assigning) ????? Warning! In some version of python division might not do what you expect. Integer division gives an integer result. Types of number Integer: Plus and minus. No decimal points or commas Float: Decimal points or scientific notation okay. 2e-2 = 2 x 10-2 Working With Numbers What is the minimum of these numbers: What is the maximum of these numbers: What type of variable is this? Remember that str(anything) makes that variable into a string: Working With Text Single or double quotes. -
CS 0449: Introduction to Systems Software
CS 0449: Introduction to Systems Software Jonathan Misurda Computer Science Department University of Pittsburgh [email protected] http://www.cs.pitt.edu/∼jmisurda Version 3, revision 1 Last modified: July 27, 2017 at 1:33 P.M. Copyright © 2017 by Jonathan Misurda This text is meant to accompany the course CS 0449 at the University of Pittsburgh. Any other use, commercial or otherwise, is prohibited without permission of the author. All rights reserved. Java is a registered trademark of Oracle Corporation. This reference is dedicated to the students of CS 0449, Fall 2007 (2081). Their patience in dealing with a changing course and feedback on the first version of this text was greatly appreciated. Contents Contents i List of Figures v List of Code Listings vii Preface ix 1 Pointers 1 1.1 Basic Pointers . 2 1.1.1 Fundamental Operations . 2 1.2 Passing Pointers to Functions . 4 1.3 Pointers, Arrays, and Strings . 5 1.3.1 Pointer Arithmetic . 6 1.4 Terms and Definitions . 7 2 Variables: Scope & Lifetime 8 2.1 Scope and Lifetime in C . 9 2.1.1 Global Variables . 11 2.1.2 Automatic Variables . 12 2.1.3 Register variables . 13 2.1.4 Static Variables . 13 2.1.5 Volatile Variables . 16 2.2 Summary Table . 17 2.3 Terms and Definitions . 17 ii Contents 3 Compiling & Linking: From Code to Executable 19 3.1 The Stages of Compilation . 19 3.1.1 The Preprocessor . 20 3.1.2 The Compiler . 21 3.1.3 The Linker . 22 3.2 Executable File Formats . -
Standardizing SAS Code for Quality Programs Clarence Wm
Standardizing SAS Code for Quality Programs Clarence Wm. Jackson, CQA, Change Manager City of Dallas, Communication and Information Services, Change Management Group Abstract and Introduction SAS software is a powerful programming system that allows even casual users to write very complicated solutions for business problems. It is free form, meaning that it has no syntactical constraints for defining the program structure, as is found in such programming languages as COBOL and ALC. However, the free form of SAS code can be a mixed blessing, where code maintenance is concemed. Whenever changes in the SAS code are required, if someone other than the original programmer has to make the changes, this may result in errors, lost productivity and a reduction in the consistency and overall quality of the program. This situation may be avoided by the implementation of appropriate standards for the writing of SAS programs. This paper will review industry standards for other programming languages, and will discuss how SAS code could be standardized. The paper also will review the benefits and opportunities for quality improvement. Standards Provide Basis for Quality What is a "Standard"? The American Heritage dictionary defines "standard" as "an acknowledged measure 0/ comparison/or quantitative or qualitative value; criterion; nonn; a degree or level 0/ requirement, excellence or attainment. " There are two categories of standards related to Information Technology, 'industry' and 'installation'. The industry standards are those set by a recognized standards organization meant to facilitate the efficient interchange of information between organizations and companies. The installation standards serve the purpose of providing guidelines for the efficient operation of a single installation or shop. -
Exit Legacy: Atos Syntel's Solution Accelerator for Faster, Cheaper
Exit Legacy: Atos Syntel’s Solution Accelerator for Faster, Cheaper, and Derisked Legacy Transformation Legacy software is embedded in customer organizations with extreme complexity. The problems with legacy applications are lack of agility, skills shortage, and high costs of ownership. In the new digital era, having IT systems that are agile, proactive, and flexible is the key to business growth. Customers typically face the following challenges while transforming their legacy applications: • Migration of legacy applications/systems is a time consuming and costly affair • A number of errors arise due to the manual method of execution • Generally migration is done for legacy technologies and finding the right resources is a challenge Legacy modernization provides solutions to all these problems and helps customers get into a non-legacy distributed platform with cloud adoption, and digital and analytics capabilities. Atos Syntel’s Exit Legacy portal hosts various solution accelerators that help in legacy modernization. With Exit Legacy, transforming your legacy is faster, risk-free, and cheaper. Exit Legacy: Atos Syntel’s Solution Accelerator for Faster, Cheaper, and Derisked Legacy Transformation BUSINESS Atos Syntel’s Solution BENEFITS Atos Syntel’s Exit Legacy portal is aligned to the modernization of project life cycles to ensure the • ~50% faster assessment modernization of the entire eco-system, instead of just application components or data. • ~50% reduction in manual Exit Legacy Tool Set efforts Inventory Analysis Tool: • ~50% costs -
Foreign Library Interface by Daniel Adler Dia Applications That Can Run on a Multitude of Plat- Forms
30 CONTRIBUTED RESEARCH ARTICLES Foreign Library Interface by Daniel Adler dia applications that can run on a multitude of plat- forms. Abstract We present an improved Foreign Function Interface (FFI) for R to call arbitary na- tive functions without the need for C wrapper Foreign function interfaces code. Further we discuss a dynamic linkage framework for binding standard C libraries to FFIs provide the backbone of a language to inter- R across platforms using a universal type infor- face with foreign code. Depending on the design of mation format. The package rdyncall comprises this service, it can largely unburden developers from the framework and an initial repository of cross- writing additional wrapper code. In this section, we platform bindings for standard libraries such as compare the built-in R FFI with that provided by (legacy and modern) OpenGL, the family of SDL rdyncall. We use a simple example that sketches the libraries and Expat. The package enables system- different work flow paths for making an R binding to level programming using the R language; sam- a function from a foreign C library. ple applications are given in the article. We out- line the underlying automation tool-chain that extracts cross-platform bindings from C headers, FFI of base R making the repository extendable and open for Suppose that we wish to invoke the C function sqrt library developers. of the Standard C Math library. The function is de- clared as follows in C: Introduction double sqrt(double x); We present an improved Foreign Function Interface The .C function from the base R FFI offers a call (FFI) for R that significantly reduces the amount of gate to C code with very strict conversion rules, and C wrapper code needed to interface with C.