Seg‐Fault How‐To
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University of California at Berkeley College of Engineering Department of Electrical Engineering and Computer Science
University of California at Berkeley College of Engineering Department of Electrical Engineering and Computer Science EECS 61C, Fall 2003 Lab 2: Strings and pointers; the GDB debugger PRELIMINARY VERSION Goals To learn to use the gdb debugger to debug string and pointer programs in C. Reading Sections 5.1-5.5, in K&R GDB Reference Card (linked to class page under “resources.”) Optional: Complete GDB documentation (http://www.gnu.org/manual/gdb-5.1.1/gdb.html) Note: GDB currently only works on the following machines: • torus.cs.berkeley.edu • rhombus.cs.berkeley.edu • pentagon.cs.berkeley.edu Please ssh into one of these machines before starting the lab. Basic tasks in GDB There are two ways to start the debugger: 1. In EMACS, type M-x gdb, then type gdb <filename> 2. Run gdb <filename> from the command line The following are fundamental operations in gdb. Please make sure you know the gdb commands for the following operations before you proceed. 1. How do you run a program in gdb? 2. How do you pass arguments to a program when using gdb? 3. How do you set a breakpoint in a program? 4. How do you set a breakpoint which which only occurs when a set of conditions is true (eg when certain variables are a certain value)? 5. How do you execute the next line of C code in the program after a break? 1 6. If the next line is a function call, you'll execute the call in one step. How do you execute the C code, line by line, inside the function call? 7. -
User's Manual
rBOX610 Linux Software User’s Manual Disclaimers This manual has been carefully checked and believed to contain accurate information. Axiomtek Co., Ltd. assumes no responsibility for any infringements of patents or any third party’s rights, and any liability arising from such use. Axiomtek does not warrant or assume any legal liability or responsibility for the accuracy, completeness or usefulness of any information in this document. Axiomtek does not make any commitment to update the information in this manual. Axiomtek reserves the right to change or revise this document and/or product at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of Axiomtek Co., Ltd. Trademarks Acknowledgments Axiomtek is a trademark of Axiomtek Co., Ltd. ® Windows is a trademark of Microsoft Corporation. Other brand names and trademarks are the properties and registered brands of their respective owners. Copyright 2014 Axiomtek Co., Ltd. All Rights Reserved February 2014, Version A2 Printed in Taiwan ii Table of Contents Disclaimers ..................................................................................................... ii Chapter 1 Introduction ............................................. 1 1.1 Specifications ...................................................................................... 2 Chapter 2 Getting Started ...................................... -
LTIB Quick Start: Targeting the Coldfire Mcf54418tower Board By: Soledad Godinez and Jaime Hueso Guadalajara Mexico
Freescale Semiconductor Document Number: AN4426 Application Note Rev. 0, December 2011 LTIB Quick Start: Targeting the ColdFire MCF54418Tower Board by: Soledad Godinez and Jaime Hueso Guadalajara Mexico Contents 1 Introduction 1 Introduction................................................................1 The purpose of this document is to indicate step-by-step how 2 LTIB..........................................................................1 to accomplish these tasks: • Install the BSP on a host development system. 2.1 Introduction....................................................1 • Run Linux Target Image Builder (LTIB) to build target 2.2 Installing the BSP...........................................2 images. • Boot Linux on the ColdFire MCF54418 Tower board. 2.3 Running LTIB................................................7 3 Target deployment .................................................13 This document is a guide for people who want to properly set up the Freescale Linux Target Image Builder (LTIB) for the 3.1 The Tower kit ..............................................13 ColdFire MCF54418 Tower Board Support Package (BSP). 3.2 Constructing the Tower kit...........................15 3.3 Programming U-boot, kernel, and root file system.............................................16 2 LTIB 3.4 Configuring U-boot......................................24 3.5 Running.......................................................25 4 Conclusions.............................................................26 2.1 Introduction Freescale GNU/Linux -
Compiling and Debugging Basics
Compiling and Debugging Basics Service CoSiNus IMFT P. Elyakime H. Neau A. Pedrono A. Stoukov Avril 2015 Outline ● Compilers available at IMFT? (Fortran, C and C++) ● Good practices ● Debugging Why? Compilation errors and warning Run time errors and wrong results Fortran specificities C/C++ specificities ● Basic introduction to gdb, valgrind and TotalView IMFT - CoSiNus 2 Compilers on linux platforms ● Gnu compilers: gcc, g++, gfortran ● Intel compilers ( 2 licenses INPT): icc, icpc, ifort ● PGI compiler fortran only (2 licenses INPT): pgf77, pgf90 ● Wrappers mpich2 for MPI codes: mpicc, mpicxx, mpif90 IMFT - CoSiNus 3 Installation ● Gnu compilers: included in linux package (Ubuntu 12.04 LTS, gcc/gfortran version 4.6.3) ● Intel and PGI compilers installed on a centralized server (/PRODCOM), to use it: source /PRODCOM/bin/config.sh # in bash source /PRODCOM/bin/config.csh # in csh/tcsh ● Wrappers mpich2 installed on PRODCOM: FORTRAN : mympi intel # (or pgi or gnu) C/C++ : mympi intel # (or gnu) IMFT - CoSiNus 4 Good practices • Avoid too long source files! • Use a makefile if you have more than one file to compile • In Fortran : ” implicit none” mandatory at the beginning of each program, module and subroutine! • Use compiler’s check options IMFT - CoSiNus 5 Why talk about debugging ? Yesterday, my program was running well: % gfortran myprog.f90 % ./a.out % vmax= 3.3e-2 And today: % gfortran myprog.f90 % ./a.out % Segmentation fault Yet I have not changed anything… Because black magic is not the reason most often, debugging could be helpful! (If you really think that the cause of your problem is evil, no need to apply to CoSiNus, we are not God!) IMFT - CoSiNus 6 Debugging Methodical process to find and fix flows in a code. -
A Type-Checking Preprocessor for Cilk 2, a Multithreaded C Language
A Typechecking Prepro cessor for Cilk a Multithreaded C Language by Rob ert C Miller Submitted to the Department of Electrical Engineering and Computer Science in partial fulllment of the requirements for the degrees of Bachelor of Science in Computer Science and Engineering and Master of Engineering in Electrical Engineering and Computer Science at the Massachusetts Institute of Technology May Copyright Massachusetts Institute of Technology All rights reserved Author ::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::: Department of Electrical Engineering and Computer Science May Certied by ::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::: Charles E Leiserson Thesis Sup ervisor Accepted by ::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::: F R Morgenthaler Chairman Department Committee on Graduate Theses A Typechecking Prepro cessor for Cilk a Multithreaded C Language by Rob ert C Miller Submitted to the Department of Electrical Engineering and Computer Science on May in partial fulllment of the requirements for the degrees of Bachelor of Science in Computer Science and Engineering and Master of Engineering in Electrical Engineering and Computer Science Abstract This thesis describ es the typechecking optimizing translator that translates Cilk a C ex tension language for multithreaded parallel programming into C The CilktoC translator is based on CtoC a to ol I developed that parses type checks analyzes and regenerates a C program With a translator based on CtoC -
Lecture 15 15.1 Paging
CMPSCI 377 Operating Systems Fall 2009 Lecture 15 Lecturer: Emery Berger Scribe: Bruno Silva,Jim Partan 15.1 Paging In recent lectures, we have been discussing virtual memory. The valid addresses in a process' virtual address space correspond to actual data or code somewhere in the system, either in physical memory or on the disk. Since physical memory is fast and is a limited resource, we use the physical memory as a cache for the disk (another way of saying this is that the physical memory is \backed by" the disk, just as the L1 cache is \backed by" the L2 cache). Just as with any cache, we need to specify our policies for when to read a page into physical memory, when to evict a page from physical memory, and when to write a page from physical memory back to the disk. 15.1.1 Reading Pages into Physical Memory For reading, most operating systems use demand paging. This means that pages are only read from the disk into physical memory when they are needed. In the page table, there is a resident status bit, which says whether or not a valid page resides in physical memory. If the MMU tries to get a physical page number for a valid page which is not resident in physical memory, it issues a pagefault to the operating system. The OS then loads that page from disk, and then returns to the MMU to finish the translation.1 In addition, many operating systems make some use of pre-fetching, which is called pre-paging when used for pages. -
NASM for Linux
1 NASM for Linux Microprocessors II 2 NASM for Linux Microprocessors II NASM Package nasm package available as source or as executables Typically /usr/bin/nasm and /usr/bin/ndisasm Assembly NASM Linux requires elf format for object files ELF = Executable and Linking Format Typical header size = 330h bytes for nasm −f elf [−o <output>] <filename> Linking Linux Object files can be linked with gcc gcc [−options] <filename.o> [other_files.o] Disassembly View executable as 32-bit assembly code ndisasm −e 330h –b 32 a.out | less objdump –d a.out | less Fall 2007 Hadassah College Dr. Martin Land Fall 2007 Hadassah College Dr. Martin Land 3 NASM for Linux Microprocessors II 4 NASM for Linux Microprocessors II gcc Stages Example — 1 Stages of Gnu C compilation factorial2.c #include <math.h> main #include <stdio.h> sets j = 12 main() Source Translation Assembly Object Executable calls factorial 10,000,000 times Code Unit Code Code File { int times; prog.c prog.i prog.s prog.o a.out int i , j = 12; preprocess compile assemble link for (times = 0 ; times < 10000000 ; ++times){ i = factorial(j); gcc -E } gcc -S printf("%d\n",i); gcc -c } gcc int factorial(n) int n; factorial calculates n! by recursion { if (n == 0) return 1; else return n * factorial(n-1); } Fall 2007 Hadassah College Dr. Martin Land Fall 2007 Hadassah College Dr. Martin Land 5 NASM for Linux Microprocessors II 6 NASM for Linux Microprocessors II Example — 2 Example — 3 ~/gcc$ gcc factorial2.c Compile program as separate files produces executable a.out factorial2a.c ~/gcc$ time a.out main() { 479001600 int times; int i,j=12; for (times = 0 ; times < 10000000 ; ++times){ real 0m9.281s i = factorial(j); factorial2b.c } #include <math.h> printf("%d\n",i); user 0m8.339s #include <stdio.h> } sys 0m0.008s int factorial(n) int n; { Program a.out runs in 8.339 seconds on 300 MHz if (n == 0) Pentium II return 1; else return n * factorial(n-1); } Fall 2007 Hadassah College Dr. -
N2429 V 1 Function Failure Annotation
ISO/IEC JTC 1/SC 22/WG14 N2429 September 23, 2019 v 1 Function failure annotation Niall Douglas Jens Gustedt ned Productions Ltd, Ireland INRIA & ICube, Université de Strasbourg, France We have been seeing an evolution in proposals for the best syntax for describing how to mark how a function fails, such that compilers and linkers can much better optimise function calls than at present. These papers were spurred by [WG21 P0709] Zero-overhead deterministic exceptions, which proposes deterministic exception handling for C++, whose implementation could be very compatible with C code. P0709 resulted in [WG21 P1095] Zero overhead deterministic failure – A unified mecha- nism for C and C++ which proposed a C syntax and exception-like mechanism for supporting C++ deterministic exceptions. That was responded to by [WG14 N2361] Out-of-band bit for exceptional return and errno replacement which proposed an even wider reform, whereby the most popular idioms for function failure in C code would each gain direct calling convention support in the compiler. This paper synthesises all of the proposals above into common proposal, and does not duplicate some of the detail in the above papers for brevity and clarity. It hews closely to what [WG14 N2361] proposes, but with different syntax, and in addition it shows how the corresponding C++ features can be constructed on top of it, without loosing call compatibility with C. Contents 1 Introduction 2 1.1 Differences between WG14 N2361 and WG21 P1095 . .3 2 Proposed Design 4 2.1 errno-related function failure editions . .5 2.2 When to choose which edition . -
Memory Management
Memory management Virtual address space ● Each process in a multi-tasking OS runs in its own memory sandbox called the virtual address space. ● In 32-bit mode this is a 4GB block of memory addresses. ● These virtual addresses are mapped to physical memory by page tables, which are maintained by the operating system kernel and consulted by the processor. ● Each process has its own set of page tables. ● Once virtual addresses are enabled, they apply to all software running in the machine, including the kernel itself. ● Thus a portion of the virtual address space must be reserved to the kernel Kernel and user space ● Kernel might not use 1 GB much physical memory. ● It has that portion of address space available to map whatever physical memory it wishes. ● Kernel space is flagged in the page tables as exclusive to privileged code (ring 2 or lower), hence a page fault is triggered if user-mode programs try to touch it. ● In Linux, kernel space is constantly present and maps the same physical memory in all processes. ● Kernel code and data are always addressable, ready to handle interrupts or system calls at any time. ● By contrast, the mapping for the user-mode portion of the address space changes whenever a process switch happens Kernel virtual address space ● Kernel address space is the area above CONFIG_PAGE_OFFSET. ● For 32-bit, this is configurable at kernel build time. The kernel can be given a different amount of address space as desired. ● Two kinds of addresses in kernel virtual address space – Kernel logical address – Kernel virtual address Kernel logical address ● Allocated with kmalloc() ● Holds all the kernel data structures ● Can never be swapped out ● Virtual addresses are a fixed offset from their physical addresses. -
The C-- Language Reference Manual
The C-- Language Reference Manual Simon Peyton Jones Thomas Nordin Dino Oliva Pablo Nogueira Iglesias April 23, 1998 Contents 1 Introduction 3 2 Syntax definition 3 2.1 General ......................................... 3 2.2 Comments........................................ 6 2.3 Names.......................................... 6 2.4 Namescope....................................... 6 2.5 The import and export declarations ........................ 6 2.6 Constants ....................................... 7 2.6.1 Integer and floating point numbers . ...... 7 2.6.2 Characters and strings . ... 7 3 Fundamental concepts in C-- 7 3.1 Memory......................................... 7 3.2 Datasegment ..................................... 8 3.3 Codesegment..................................... 8 3.4 Types .......................................... 8 3.5 Local variables (or registers) . ......... 8 3.6 Addresses ....................................... 9 3.7 Names.......................................... 9 3.8 Foreign language interface . ....... 9 4 Data layout directives 9 4.1 Labels.......................................... 10 4.2 Initialisation.................................. ..... 10 4.3 Alignment....................................... 12 1 5 Procedures 12 5.1 Proceduredefinition..... ...... ..... ...... ...... .. ..... 12 5.2 Statements...................................... 13 5.2.1 skip; ..................................... 13 5.2.2 Declaration ................................... 13 5.2.3 Assignment................................... 13 5.2.4 -
Lesson 01 Programming with C
Lesson 01 Programming with C Pijushkanti Panigrahi What is C ? • The C is a programming Language, developed by Dennis Ritchie for creating system applications that directly interact with the hardware devices such as drivers, kernels, etc. • C programming is considered as the base for other programming languages, that is why it is known as mother language. • C is famous for its Compactness. • C language is case sensitive. 2 Features It can be defined by the following ways: Mother language System programming language Procedure-oriented programming language Structured programming language Mid-level programming language 3 1) C as a mother language ? • C language is considered as the mother language of all the modern programming languages because most of the compilers, JVMs, Kernels, etc. are written in C language , and most of the programming languages follow C syntax, for example, C++, Java, C#, etc. • It provides the core concepts like the array , strings , functions , file handling , etc . that are being used in many languages like C++ , Java , C# , etc. 4 2) C as a system programming language • A system programming language is used to create system software. • C language is a system programming language because it can be used to do low-level programming (for example driver and kernel) . • It is generally used to create hardware devices, OS, drivers, kernels, etc. For example, Linux kernel is written in C. 5 3) C as a procedural language • A procedure is known as a function, method, routine, subroutine, etc. A procedural language specifies a series of steps for the program to solve the problem. -
ENCM 335 Fall 2018 Lab 3 for the Week of October 1
page 1 of 11 ENCM 335 Fall 2018 Lab 3 for the Week of October 1 Steve Norman Department of Electrical & Computer Engineering University of Calgary September 2018 Lab instructions and other documents for ENCM 335 can be found at https://people.ucalgary.ca/~norman/encm335fall2018/ Administrative details Each student must hand in their own assignment Later in the course, you may be allowed to work in pairs on some assignments. Due Dates The Due Date for this assignment is 3:30pm Friday, October 5. The Late Due Date is 3:30pm Tuesday, October 9 (not Monday the 8th, because that is a holiday). The penalty for handing in an assignment after the Due Date but before the Late Due Date is 3 marks. In other words, X/Y becomes (X{3)/Y if the assignment is late. There will be no credit for assignments turned in after the Late Due Date; they will be returned unmarked. Marking scheme A 4 marks B 8 marks C unmarked D 2 marks E 8 marks F 2 marks G 4 marks total 28 marks How to package and hand in your assignments Please see the information in the Lab 1 instructions. Function interface comments, continued For Lab 2, you were asked to read a document called \Function Interface Com- ments". ENCM 335 Fall 2018 Lab 3 page 2 of 11 Figure 1: Sketch of a program with a function to find the average element value of an array of ints. The function can be given only one argument, and the function is supposed to work correctly for whatever number of elements the array has.