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In computing, the 'Executable and Linking Format' ('ELF', formerly called 'Extensible Linking Format') is a common standard file format for executables, object code, shared libraries, and core dumps. First published in the System V Application Binary Interface specification, and later in the Tool Interface Standard, it was quickly accepted among different vendors of Unix systems. In 1999 it was chosen as the standard binary file format for Unix and Unix-like systems by the 86open project.
Today the ELF format has replaced executable formats such as a.out and COFF in the Linux, Solaris, IRIX, FreeBSD, NetBSD, and OpenBSD operating systems (DragonFly BSD was forked from FreeBSD after the switch to ELF). Because other formats are proprietary, platform-specific, or less extensible than ELF, some users hold that ELF outperforms other formats, whereas others may consider it a competitor to the other formats. ELF is also used in the Itanium version of OpenVMS, a non-UNIX-based operating system, as well as replacing the Portable Executable on BeOS Revision 4 and later for x86 based computers (PPC computers stayed with Preferred Executable Format, having never used Portable Executable), which are also not UNIX-based. The PlayStation Portable, PlayStation 2 and PlayStation 3 consoles also use ELF as their executable file format.

Contents

ELF file layout

Tools

See also

External links

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 or 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.

Tools

★ readelf is a Unix binary utility that displays information about one or more ELF files. A GPL implementation is provided by GNU Binutils.

★ elfdump is a Solaris command for viewing ELF information in an elf file.

★ objdump provides a wide range of information about ELF files and other object formats.

See also

★ Portable Executable (PE)

★ DWARF

★ Mach-O

External links

★ Tool Interface Standard (TIS) Executable and Linking Format (ELF) Specification Version 1.2 (May 1995)

★ ELF for the ARM Architecture

★ ELF-64 Object File Format Version 1.5 Draft 2 (May 1998)

★ Elf library routines

★ free ELF object file access library

★ ELFIO: a C++ library for reading and generating files in the ELF binary format.

★ ''How To Write Shared Libraries'' by Ulrich Drepper (2006-08-20)

★ ''An unsung hero: The hardworking ELF'' by Peter Seebach (2005-12-20)

★ ''LibElf and GElf — A Library to Manipulate ELF Files'' by Neelakanth Nadgir (August 2001)

★ ''The ELF Object File Format by Dissection'' by Eric Youngdale (1995-05-01)

★ ''A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux'' by Brian Raiter

★ FreeBSD Handbook — Binary formats

★ Description of the ELF binary format

★ elf(5) manual page

★ NetBSD ELF FAQ

★ view Sun's Linker and Libraries Guide