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Proceedings of the Bsdcon 2002 Conference
USENIX Association Proceedings of the BSDCon 2002 Conference San Francisco, California, USA February 11-14, 2002 THE ADVANCED COMPUTING SYSTEMS ASSOCIATION © 2002 by The USENIX Association All Rights Reserved For more information about the USENIX Association: Phone: 1 510 528 8649 FAX: 1 510 548 5738 Email: [email protected] WWW: http://www.usenix.org Rights to individual papers remain with the author or the author's employer. Permission is granted for noncommercial reproduction of the work for educational or research purposes. This copyright notice must be included in the reproduced paper. USENIX acknowledges all trademarks herein. Rethinking /devand devices in the UNIX kernel Poul-Henning Kamp <[email protected]> The FreeBSD Project Abstract An outstanding novelty in UNIX at its introduction was the notion of ‘‘a file is a file is a file and evenadevice is a file.’’ Going from ‘‘hardware only changes when the DEC Field engineer is here’’to‘‘my toaster has USB’’has put serious strain on the rather crude implementation of the ‘‘devices as files’’concept, an implementation which has survivedpractically unchanged for 30 years in most UNIX variants. Starting from a high-levelviewofdevices and the semantics that have grown around them overthe years, this paper takes the audience on a grand tour of the redesigned FreeBSD device-I/O system, to convey anoverviewofhow itall fits together,and to explain whythings ended up as theydid, howtouse the newfeatures and in particular hownot to. 1. Introduction tax and meaning, so that a program expecting a file name as a parameter can be passed a device name; There are really only twofundamental ways to concep- finally,special files are subject to the same protec- tualise I/O devices in an operating system: The usual tion mechanism as regular files. -
Introduction to Debugging the Freebsd Kernel
Introduction to Debugging the FreeBSD Kernel John H. Baldwin Yahoo!, Inc. Atlanta, GA 30327 [email protected], http://people.FreeBSD.org/˜jhb Abstract used either directly by the user or indirectly via other tools such as kgdb [3]. Just like every other piece of software, the The Kernel Debugging chapter of the FreeBSD kernel has bugs. Debugging a ker- FreeBSD Developer’s Handbook [4] covers nel is a bit different from debugging a user- several details already such as entering DDB, land program as there is nothing underneath configuring a system to save kernel crash the kernel to provide debugging facilities such dumps, and invoking kgdb on a crash dump. as ptrace() or procfs. This paper will give a This paper will not cover these topics. In- brief overview of some of the tools available stead, it will demonstrate some ways to use for investigating bugs in the FreeBSD kernel. FreeBSD’s kernel debugging tools to investi- It will cover the in-kernel debugger DDB and gate bugs. the external debugger kgdb which is used to perform post-mortem analysis on kernel crash dumps. 2 Kernel Crash Messages 1 Introduction The first debugging service the FreeBSD kernel provides is the messages the kernel prints on the console when the kernel crashes. When a userland application encounters a When the kernel encounters an invalid condi- bug the operating system provides services for tion (such as an assertion failure or a memory investigating the bug. For example, a kernel protection violation) it halts execution of the may save a copy of the a process’ memory current thread and enters a “panic” state also image on disk as a core dump. -
Process and Memory Management Commands
Process and Memory Management Commands This chapter describes the Cisco IOS XR software commands used to manage processes and memory. For more information about using the process and memory management commands to perform troubleshooting tasks, see Cisco ASR 9000 Series Aggregation Services Router Getting Started Guide. • clear context, on page 2 • dumpcore, on page 3 • exception coresize, on page 6 • exception filepath, on page 8 • exception pakmem, on page 12 • exception sparse, on page 14 • exception sprsize, on page 16 • follow, on page 18 • monitor threads, on page 25 • process, on page 29 • process core, on page 32 • process mandatory, on page 34 • show context, on page 36 • show dll, on page 39 • show exception, on page 42 • show memory, on page 44 • show memory compare, on page 47 • show memory heap, on page 50 • show processes, on page 54 Process and Memory Management Commands 1 Process and Memory Management Commands clear context clear context To clear core dump context information, use the clear context command in the appropriate mode. clear context location {node-id | all} Syntax Description location{node-id | all} (Optional) Clears core dump context information for a specified node. The node-id argument is expressed in the rack/slot/module notation. Use the all keyword to indicate all nodes. Command Default No default behavior or values Command Modes Administration EXEC EXEC mode Command History Release Modification Release 3.7.2 This command was introduced. Release 3.9.0 No modification. Usage Guidelines To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. -
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. -
Post Mortem Crash Analysis
Post Mortem Crash Analysis Johan Heander & Magnus Malmborn January 14, 2007 Abstract To improve the quality and reliability of embedded systems it is important to gather information about errors in units already sold and deployed. To achieve this, a system for transmitting error information from the customer back to the developers is needed, and the developers must also have a set of tools to analyze the error reports. The purpose of this master thesis was to develop a fully functioning demon- stration system for collection, transmission and interpretation of error reports from Axis network cameras using the Linux operating system. The system has been shown to handle both kernel and application errors and conducts automatic analysis of received data. It also uses standard HTTP protocol for all network transfers making it easy to use even on firewalled net- works. i ii Acknowledgement We would like to thank our LTH supervisor Jonas Skeppstedt for all he has taught us about computer science in general and operating systems and the C programming language in particular. We would also like to thank Mikael Starvik at Axis Communications for quickly providing us with all hardware and information we needed to complete this thesis, and for providing us with support during our implementation and writing. Finally we thank all the developers working at Axis Communications, many of whom have provided input and reflections on our work. iii iv Contents 1 Introduction 1 1.1 Problem description . 1 1.2 Problem analysis . 1 2 Background 3 2.1 Kernel crashes . 3 2.2 User space crashes . -
Advanced Openbsd Hardening
Advanced Hardening WrongunWrongun && DCDC JuneJune 20052005 ssh://root:[email protected] Lab Challenge JoinJoin thethe wifiwifi netnet andand sshssh intointo thethe boxbox usingusing thethe accountaccount specifiedspecified inin thethe footerfooter TryTry toto pwnpwn thethe boxbox byby addingadding anan accountaccount forfor yourselfyourself oror backdooringbackdooring sshdsshd ssh://root:[email protected] “Only one remote hole in the default install, in more than 8 years! “ ssh://root:[email protected] So OpenBSD is uber secure, right? Actually,Actually, nono …… TheThe defaultdefault installinstall hashas nothingnothing enabledenabled (except(except ssh)ssh) ““NoNo wonderwonder itit ’’ss secure,secure, itit ’’ss poweredpowered off!off! ”” SourceSource --onlyonly patchingpatching strategystrategy makesmakes itit difficultdifficult toto rollroll outout fixesfixes toto platformsplatforms w/ow/o compilerscompilers (i.e.(i.e. disklessdiskless firewalls,firewalls, etc.)etc.) ssh://root:[email protected] Brief History of OpenBSD Vulnerabilities 30 March 05: Bugs in the cp(4) stack can lead to memory exhaustion or processing of TCP segments with invalid SACK optio ns and cause a system crash. 14 Dec 04: On systems running sakmpd(8) it is possible for a local user to cause kernel memory corruption and system panic by setti ng psec(4) credentials on a socket 20 Sept 04: radius authentication, as implemented by ogin_radius(8) , was not checking the shared secret used for replies sent by the radius server. This could allow an attacker to spoof -
Ebook - Informations About Operating Systems Version: August 15, 2006 | Download
eBook - Informations about Operating Systems Version: August 15, 2006 | Download: www.operating-system.org AIX Internet: AIX AmigaOS Internet: AmigaOS AtheOS Internet: AtheOS BeIA Internet: BeIA BeOS Internet: BeOS BSDi Internet: BSDi CP/M Internet: CP/M Darwin Internet: Darwin EPOC Internet: EPOC FreeBSD Internet: FreeBSD HP-UX Internet: HP-UX Hurd Internet: Hurd Inferno Internet: Inferno IRIX Internet: IRIX JavaOS Internet: JavaOS LFS Internet: LFS Linspire Internet: Linspire Linux Internet: Linux MacOS Internet: MacOS Minix Internet: Minix MorphOS Internet: MorphOS MS-DOS Internet: MS-DOS MVS Internet: MVS NetBSD Internet: NetBSD NetWare Internet: NetWare Newdeal Internet: Newdeal NEXTSTEP Internet: NEXTSTEP OpenBSD Internet: OpenBSD OS/2 Internet: OS/2 Further operating systems Internet: Further operating systems PalmOS Internet: PalmOS Plan9 Internet: Plan9 QNX Internet: QNX RiscOS Internet: RiscOS Solaris Internet: Solaris SuSE Linux Internet: SuSE Linux Unicos Internet: Unicos Unix Internet: Unix Unixware Internet: Unixware Windows 2000 Internet: Windows 2000 Windows 3.11 Internet: Windows 3.11 Windows 95 Internet: Windows 95 Windows 98 Internet: Windows 98 Windows CE Internet: Windows CE Windows Family Internet: Windows Family Windows ME Internet: Windows ME Seite 1 von 138 eBook - Informations about Operating Systems Version: August 15, 2006 | Download: www.operating-system.org Windows NT 3.1 Internet: Windows NT 3.1 Windows NT 4.0 Internet: Windows NT 4.0 Windows Server 2003 Internet: Windows Server 2003 Windows Vista Internet: Windows Vista Windows XP Internet: Windows XP Apple - Company Internet: Apple - Company AT&T - Company Internet: AT&T - Company Be Inc. - Company Internet: Be Inc. - Company BSD Family Internet: BSD Family Cray Inc. -
OM-Cube Project
OM-Cube project V. Hiribarren, N. Marchand, N. Talfer [email protected] - [email protected] - [email protected] Abstract. The OM-Cube project is composed of several components like a minimal operating system, a multi- media player, a LCD display and an infra-red controller. They should be chosen to fit the hardware of an em- bedded system. Several other similar projects can provide information on the software that can be chosen. This paper aims to examine the different available tools to build the OM-Multimedia machine. The main purpose is to explore different ways to build an embedded system that fits the hardware and fulfills the project. 1 A Minimal Operating System The operating system is the core of the embedded system, and therefore should be chosen with care. Because of its popu- larity, a Linux based system seems the best choice, but other open systems exist and should be considered. After having elected a system, all unnecessary components may be removed to get a minimal operating system. 1.1 A Linux Operating System Using a Linux kernel has several advantages. As it’s a popular kernel, many drivers and documentation are available. Linux is an open source kernel; therefore it enables anyone to modify its sources and to recompile it. Using Linux in an embedded system requires adapting the kernel to the hardware and to the system needs. A simple method for building a Linux embed- ded system is to create a partition on a development host and to mount it on a temporary mount point. This partition is filled as one goes along and then, the final distribution is put on the target host [Fich02] [LFS]. -
UNIX X Command Tips and Tricks David B
SESUG Paper 122-2019 UNIX X Command Tips and Tricks David B. Horvath, MS, CCP ABSTRACT SAS® provides the ability to execute operating system level commands from within your SAS code – generically known as the “X Command”. This session explores the various commands, the advantages and disadvantages of each, and their alternatives. The focus is on UNIX/Linux but much of the same applies to Windows as well. Under SAS EG, any issued commands execute on the SAS engine, not necessarily on the PC. X %sysexec Call system Systask command Filename pipe &SYSRC Waitfor Alternatives will also be addressed – how to handle when NOXCMD is the default for your installation, saving results, and error checking. INTRODUCTION In this paper I will be covering some of the basics of the functionality within SAS that allows you to execute operating system commands from within your program. There are multiple ways you can do so – external to data steps, within data steps, and within macros. All of these, along with error checking, will be covered. RELEVANT OPTIONS Execution of any of the SAS System command execution commands depends on one option's setting: XCMD Enables the X command in SAS. Which can only be set at startup: options xcmd; ____ 30 WARNING 30-12: SAS option XCMD is valid only at startup of the SAS System. The SAS option is ignored. Unfortunately, ff NOXCMD is set at startup time, you're out of luck. Sorry! You might want to have a conversation with your system administrators to determine why and if you can get it changed. -
Linux Core Dumps
Linux Core Dumps Kevin Grigorenko [email protected] Many Interactions with Core Dumps systemd-coredump abrtd Process Crashes Ack! 4GB File! Most Interactions with Core Dumps Poof! Process Crashes systemd-coredump Nobody abrtd Looks core kdump not Poof! Kernel configured Crashes So what? ● Crashes are problems! – May be symptoms of security vulnerabilities – May be application bugs ● Data corruption ● Memory leaks – A hard crash kills outstanding work – Without automatic process restarts, crashes lead to service unavailability ● With restarts, a hacker may continue trying. ● We shouldn't be scared of core dumps. – When a dog poops inside the house, we don't just `rm -f $poo` or let it pile up, we try to figure out why or how to avoid it again. What is a core dump? ● It's just a file that contains virtual memory contents, register values, and other meta-data. – User land core dump: Represents state of a particular process (e.g. from crash) – Kernel core dump: Represents state of the kernel (e.g. from panic) and process data ● ELF-formatted file (like a program) User Land User Land Crash core Process 1 Process N Kernel Panic vmcore What is Virtual Memory? ● Virtual Memory is an abstraction over physical memory (RAM/swap) – Simplifies programming – User land: process isolation – Kernel/processor translate virtual address references to physical memory locations 64-bit Process Virtual 8GB RAM Address Space (16EB) (Example) 0 0 16 8 EB GB How much virtual memory is used? ● Use `ps` or similar tools to query user process virtual memory usage (in KB): – $ ps -o pid,vsz,rss -p 14062 PID VSZ RSS 14062 44648 42508 Process 1 Virtual 8GB RAM Memory Usage (VSZ) (Example) 0 0 Resident Page 1 Resident Page 2 16 8 EB GB Process 2 How much virtual memory is used? ● Virtual memory is broken up into virtual memory areas (VMAs), the sum of which equal VSZ and may be printed with: – $ cat /proc/${PID}/smaps 00400000-0040b000 r-xp 00000000 fd:02 22151273 /bin/cat Size: 44 kB Rss: 20 kB Pss: 12 kB.. -