In computing, the Executable and Linkable Format (ELF, formerly called Extensible Linking Format) is a common standard file format for. Introduction. This marks the first of several blog posts that will focus on Executable and Linkable Format (ELF) files. In this series, we’ll introduce. Section Type, executable by the CPU, Desc. code, , no, for storing data. bss, no, for storing program data. debug, no. 4 – Documentation / Reference.

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Note that depending on the formaat, you may have more sections like this. First published in the System V application binary interface Application Binary Interface specification, [1] and later in the Tool Interface Standard, [2] it was quickly accepted among different vendors of Unix systems. This field is used for several purposes, depending on the type of section.

ELF – OSDev Wiki

Dynamically linked libraries are also called shared objects. That’s where your uninitialized arrays and variable are, and the loader ‘knows’ they should be filled with zeroes This byte is set to either 1 or 2 to signify or bit format, respectively. GOT entries dedicated to dynamically linked global variables. Anatomy of an alleged failure”.

Identifies the attributes of the section. Executable Formats Microsoft 16 bit: The project progressed and in mid, SCO began developing lxrunan open-source compatibility layer able to run Linux binaries on OpenServerUnixWareand Solaris.

Note that depending on whether your file is a linkable or an executable file, the headers in the ELF file won’t be the same: In the files you will be working with, there will always be one text header and one data header.


In it was chosen as the standard binary file format for Unix and Unix-like systems on x86 by the 86open project. Unix System Laboratories [1]: Identifies the type of the segment. This page has been accessedtimes. The reason for this alignment is to prevent the mapping of two different segments within a single memory page. File offset of the Program Header Table.

Lazarus, Blockbuster, and North Korea. In the normal case of a Unix executable one or more sections are enclosed in one segment.

Privacy policy About eLinux. Anr page was last modified on 25 Septemberat The most relevant sections for this project are 1. In order to use readelf so that we can display the contents of the ELF header for a given executable, we can use the following command: This page was last edited on 27 Octoberat This byte is set to either 1 or 2 to signify little or big endiannessrespectively.

Articles needing cleanup from November All pages needing cleanup Articles with sections that need to be turned into prose from November Webarchive template wayback links. Size of segment in memory. Related Posts Muhstik Botnet Reloaded: Sun Microsystems began officially supporting lxrun for Solaris in early[22] and later moved to integrated support of the Linux binary format via Solaris Containers for Linux Applications.

In order to display sections using readelf, we can use the following command: The ELF header defines whether executalbe use or bit addresses.

Executable and Linkable Format

Identifies the target operating system ABI. Relocation becomes handy when you need to load, for example, modules or drivers.

Sections comprise all information needed for linking a target object file in order to build a working executable.


That means, however, that a part of the code is mapped twice, but with different permissions. Consequently, ELF first appeared in Solaris 2. Turns out I liked the uncertainty better”.

OS / Linux – Executable and Linkable Format (ELF)

The main disadvantage, executzble, is that the program becomes less portable because the program depends on many different shared libraries.

They’ll be to appear starting at virtual address 0x for the program to work properly.

E32Image file format on Symbian OS 9. Dynamic Linking is when the OS gives a program shared libraries if it needs them. Number of Section Headers.

Why focus on ELF? While it has some drawbacks e. Unlike many proprietary executable file formats, ELF is very flexible and extensible, and it is not bound to any particular processor or Instruction set architecture architecture.

You can create a library with GCC:. Navigation menu Personal tools Log in Request account. Today, ELF is considered the standard format on Unix-alike systems. It usually follows the file header immediately, making the offset 0x34 or 0x40 for and bit ELF executables, respectively. The text header will be the first program header and the data header will be the second program header.

Retrieved 27 April Here, we have symbol tables and relocation: The ‘flags’ will tell you what’s actually available in the ELF file. Some of common types are the following. Archived from the original on