- Executable and Linkable Format
Infobox file format
name = ELF
extension = none, .o, .so, .elf
Unix System Laboratories
genre = Binary,
executable, object, shared libraries, core dump
container for =
contained by =
extended from =
extended to = In
computing, the Executable and Linking Format (ELF, formerly called Extensible Linking Format) is a common standard file formatfor executables, object code, shared libraries, and core dumps. First published in the System VApplication Binary Interface specification, [" [http://www.caldera.com/developers/devspecs/gabi41.pdf System V Application Binary Interface] " Edition 4.1 (1997-03-18)] and later in the Tool Interface Standard, [Tool Interface Standard (TIS) " [http://x86.ddj.com/ftp/manuals/tools/elf.pdf Executable and Linking Format (ELF) Specification] Version 1.2" (May 1995)] it was quickly accepted among different vendors of Unixsystems. In 1999 it was chosen as the standard binary file format for Unix and Unix-likesystems on x86 by the 86openproject.
Unlike many other proprietary executable file formats, ELF is very flexible and extensible, and it is not bound to any particular processor or architecture. This has allowed it to be adopted by many different operating systems on many different platforms.
The ELF format has replaced older executable formats such as a.out and
COFFin many Unix-likeoperating systems such as Linux, Solaris, IRIX, FreeBSD, NetBSD, OpenBSD, DragonFly BSD, Syllable, and HP-UX(except for 32-bit PA-RISC programs which continue to use SOM). ELF has also seen some adoption in non-Unix operating systems, such as the Itanium version of OpenVMS, and BeOSRevision 4 and later for x86 based computers (where it replaced the Portable Executableformat; the PowerPCversion stayed with Preferred Executable Format). The PlayStation Portable, PlayStation 2, PlayStation 3, Wiiand GP2Xconsoles also use ELF. AmigaOS 4.0 and MorphOSalso running on PowerPC machines, use ELF. On the Amiga platform the ELF executable has replaced the previous EHF (Extended Hunk Format) which was used on Amigas equipped with PPC processor expansion cards. The Symbian OSv9 uses E32Image [" [http://wiki.forum.nokia.com/index.php/E32Image Symbian OS executable file format] "] format that is based on ELF file format.
Sony Ericsson(for example, the W800i, W610, K790, etc.), some Siemens(SGOLD and SGOLD2 platforms: from Siemens C65 to S75 and BenQ-Siemens E71/EL71) and Motorola(for example, the E398, SLVR L7, v360, v3i and all phone LTE2 which has the patch apply) phones can run ELF files through the use of a patch that adds assembly code to the main firmware(Known as the "ELFPack", in the underground moddingculture).
The ELF file format is also used as a generic object and executable format for binary images used with embedded processorsFact|date=June 2008.
ELF file layout
Each ELF file is made up of one ELF header, followed by file data. The file data can include:
* Program header table, describing zero or more segments
* Section header table, describing zero or more sections
* Data referred to by entries in the program header table, or the section header table
The segments contain information that is necessary for runtime execution of the file, while sections contain important data for linking and relocation. Each byte in the entire file is taken by no more than one section at a time, but there can be orphan bytes, which are not covered by a section. In the normal case of a Unix executable one or more sections are enclosed in one segment.
readelfis a Unix binary utility that displays information about one or more ELF files. A GPL implementation is provided by
elfdumpis a Solaris command for viewing ELF information in an elf file.
provides a wide range of information about ELF files and other object formats.
** " [http://www.linux-foundation.org/spec/book/ELF-generic/ELF-generic/book1.html Generic ELF Specification] " (an update document, not the complete ELF spec)
** " [http://www.caldera.com/developers/devspecs/gabi41.pdf System V Application Binary Interface] " Edition 4.1 (1997-03-18)
** " [http://www.caldera.com/developers/gabi/2003-12-17/contents.html System V ABI Update] " (December 2003)
** " [http://downloads.openwatcom.org/ftp/devel/docs/elf-64-gen.pdf ELF-64 Object File Format] " Version 1.5 Draft 2 (May 1998)
** " [http://www.linux-foundation.org/spec/book/ELF-AMD64/ELF-AMD64/book1.html ELF Specification for the AMD64 Architecture] "
** " [http://www.x86-64.org/documentation/abi.pdf System V ABI, AMD64 Supplement] "
* ARM [ [http://www.arm.com/products/DevTools/ABI.html Application Binary Interface (ABI) for the ARM Architecture] ] :
** " [http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044b/IHI0044B_aaelf.pdf ELF for the ARM Architecture] "
** " [http://www.linux-foundation.org/spec/book/ELF-IA32/ELF-IA32/book1.html ELF Specification for the IA32 Architecture] "
** " [http://www.caldera.com/developers/devspecs/abi386-4.pdf System V ABI, IA32 Supplement] "
** " [http://www.linux-foundation.org/spec/book/ELF-IA64/ELF-IA64/book1.html ELF Specification for the IA64 Architecture] "
** " [http://refspecs.freestandards.org/IA64conventions.pdf Itanium Software Conventions and Runtime Guide] " (September 2000)
** " [http://www.linux-foundation.org/spec/book/ELF-M32R/ELF-M32R/book1.html ELF Specification for the M32R Architecture] "
** " [http://www.linux-m32r.org/cmn/m32r/M32R-elf-abi.pdf M32R ELF ABI Supplement] " Version 1.2 (2004-08-26)
** " [http://www.caldera.com/developers/devspecs/mipsabi.pdf System V ABI, MIPS RISC Processor Supplement] "
** " [http://sources.redhat.com/ml/binutils/2003-06/msg00436.html MIPS EABI documentation] " (2003-06-11)
** " [http://www.uclibc.org/cgi-bin/viewcvs.cgi/trunk/docs/psABI-m8-16.pdf?rev=10808 Motorola 8 and 16 bit Embedded ABI] "
** " [http://devresource.hp.com/drc/STK/docs/refs/elf-pa.pdf Processor-Specific ELF Supplement for PA-RISC] "
** " [http://devresource.hp.com/drc/STK/docs/archive/pa64rt.pdf 64-bit PA-RISC Run-time Architecture] " Version 3.3 (1997-10-06)
** " [http://www.linux-foundation.org/spec/book/ELF-PPC32/ELF-PPC32/book1.html ELF Specification for the PPC32 Architecture] "
** " [http://refspecs.freestandards.org/elf/elfspec_ppc.pdf System V ABI, PPC Supplement]
** " [http://ftp.twaren.net/Unix/Sourceware/binutils/ppc-docs/ppc-eabi-1995-01.pdf PowerPC Embedded Application Binary Interface] 32-Bit Implementation" (1995-10-01)
** " [http://www.linux-foundation.org/spec/book/ELF-PPC64/ELF-PPC64/book1.html ELF Specification for the PPC64 Architecture] "
** " [http://www.linuxbase.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html 64-bit PowerPC ELF Application Binary Interface Supplement] " Version 1.9 (2004)
** " [http://www.sparc.org/standards/psABI3rd.pdf System V ABI, SPARC Supplement] "
** " [http://www.linux-foundation.org/spec/book/ELF-S390/ELF-S390/book1.html ELF Specification for the S390 Architecture] "
** " [http://www.linux-foundation.org/spec/ELF/zSeries/lzsabi0_s390/book1.html S/390 ELF ABI Supplement]
** " [http://www.linux-foundation.org/spec/book/ELF-S390X/ELF-S390X/book1.html ELF Specification for the S390X Architecture] "
** " [http://www.linux-foundation.org/spec/ELF/zSeries/lzsabi0_zSeries.pdf zSeries ELF ABI Supplement] "
* Symbian OS 9:
** " [http://wiki.forum.nokia.com/index.php/E32Image_file_format_on_Symbian_OS_9 E32Image file format on Symbian OS 9] "
86open was a project to form consensus on a common
binary fileformat for Unixand Unix-like operating systems on the common PC compatible x86 architecture, so as to encourage software developers to port to the architecture. [cite web
url = http://www.telly.org/86open-faq
title = 86Open Frequently-Asked Questions
accessdate = 2007-06-06
last = Leibovitch
first = Evan
date = 1997-12-23]
The format eventually chosen was ELF, specifically the Linux implementation of ELF, after it had turned out to be a "de facto" standard supported by all involved vendors and operating systems.
The group started email discussions in 1997 and first met in person at the
Santa Cruz Operationoffices on 1997-08-22.
The steering committee was
Marc Ewing, Dion Johnson, Evan Leibovitch, Bruce Perens, Andrew Roach, Bryan Sparks and Linus Torvalds. Other people on the project were Tim Bird, Keith Bostic, Chuck Cranor, Michael Davidson, Chris G. Demetriou, Ulrich Drepper, Don Dugger, Steve Ginzburg, Jon "maddog" Hall, Ron Holt, Jordan Hubbard, Dave Jensen, Kean Johnston, Andrew Josey, Robert Lipe, Bela Lubkin, Tim Marsland, Greg Page, Ronald Joe Record, Tim Ruckle, Joel Silverstein, Chia-pi Tien and Erik Troan. Operating systems and companies represented were BeOS, BSDI, FreeBSD, Linux, NetBSD, SCO and SunSoft, Inc..
The project progressed and in mid-1998, SCO began assisting in the development of
lxrun, an open-source compatibility layercapable of running Linux binaries on OpenServer, UnixWare, and Solaris. SCO announced official support of lxrun at LinuxWorldin March 1999. Sun Microsystemsbegan officially supporting lxrunfor Solaris in early 1999, [cite web
url = http://www.mavetju.org/mail/view_message.php?list=freebsd-emulation&id=361608
title = Bulletin on status of 86open at SCO
accessdate = 2008-05-06
last = Record
first = Ronald
date = 1998-05-21] and has since moved to integrated support of the Linux binary format via
Solaris Containers for Linux Applications.
With the BSDs having long supported Linux binaries and the main
x86Unix vendors having added support for the format, the project decided that Linux ELF was the format chosen by the industry and "declare [d] itself dissolved" on July 25, 1999. [cite web
url = http://www.telly.org/86open/
title = The86open Project - FINAL UPDATE
accessdate = 2007-05-06
last = Leibovitch
first = Evan
date = 1999-07-25]
DWARF- Debug With Attributed Record Format
Application binary interface
title = Linkers and Loaders
John R. Levine
month = October
year = 1999
publisher = Morgan-Kauffman
isbn = 1-55860-496-0
title = How To Write Shared Libraries
version = 4.0
date = 2006-08-20
url = http://people.redhat.com/drepper/dsohowto.pdf
accessdate = 2007-06-20
* " [http://www-128.ibm.com/developerworks/power/library/pa-spec12/ An unsung hero: The hardworking ELF] " by Peter Seebach (2005-12-20)
* " [http://developers.sun.com/solaris/articles/elf.html LibElf and GElf — A Library to Manipulate ELF Files] " by Neelakanth Nadgir (August 2001)
* " [http://www.linuxjournal.com/node/1060/print The ELF Object File Format by Dissection] " by Eric Youngdale (1995-05-01)
* " [http://www.muppetlabs.com/~breadbox/software/tiny/teensy.html A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux] " by Brian Raiter
* [http://www.phrack.org/issues.html?issue=61&id=8#article ELF relocation into non-relocatable objects] by Julien Vanegue (2003-08-13)
* [http://www.phrack.org/issues.html?issue=63&id=9#article Embedded ELF debugging without ptrace] by the ELFsh team (2005-08-01)
* [http://ou800doc.caldera.com/en/man/html.3elf/CONTENTS.html Elf library routines]
* [http://www.mr511.de/software/english.html LGPL ELF object file access library]
* [http://elfio.sourceforge.net/ ELFIO: a C++ library for reading and generating files in the ELF binary format.]
* [http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/binary-formats.html FreeBSD Handbook — Binary formats]
* [http://www.cs.ucdavis.edu/~haungs/paper/node10.html Description of the ELF binary format]
* [http://www.freebsd.org/cgi/man.cgi?query=elf&sektion=5 FreeBSD elf(5) manual page]
* [http://www.netbsd.org/Documentation/elf.html NetBSD ELF FAQ]
* [http://docs.sun.com/app/docs/doc/802-6319/6ia12qkfn?l=en&a=view Sun's Linker and Libraries Guide]
* [http://www.eresi-project.org The ERESI project : reverse engineering on ELF-based operating systems]
* [http://www.linuxtoday.com/developer/1999072600605PS Linux Today article on 86open] July 26, 1999
* [http://lists.debian.org/debian-announce/1997/msg00028.html Announcement of 86open on Debian Announce mailing list] October 10, 1997,
* [http://www.groklaw.net/pdf/IBM-835-Exhibit_184.pdf Declaration of Ulrich Drepper (PDF)] in
The SCO Groupvs IBM, September 19, 2006
* [http://www.groklaw.net/articlebasic.php?story=20060813114048520 86open and ELF discussion] on
Groklaw, August 13, 2006
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