Executable and Linkable Format

lastmod 2021-06-23created 2015-04-0417 edits

ELF (Executable and Linkable Format) is a standard file format for executables, object files, shared libraries, and core dumps. In 1999 it was chosen by the 86open project as the standard binary file format for x86-based Unix and Unix-like systems.

Executable image

How to using rpath

• Stackoverflow - Is there a way to inspect the current rpath on Linux?

#include <stdio.h>
#include <elf.h>
#include <link.h>

int main()
{
  const ElfW(Dyn) *dyn = _DYNAMIC;
  const ElfW(Dyn) *rpath = NULL;
  const char *strtab = NULL;
  for (; dyn->d_tag != DT_NULL; ++dyn) {
    if (dyn->d_tag == DT_RPATH) {
      rpath = dyn;
    } else if (dyn->d_tag == DT_STRTAB) {
      strtab = (const char *)dyn->d_un.d_val;
    }
  }

  if (strtab != NULL && rpath != NULL) {
    printf("RPATH: %s\n", strtab + rpath->d_un.d_val);
  }
  return 0;
}

Tutorials

Making our own executable packer

• [Recommended] Making our own executable packer ¹ (archive)

1. What's in a Linux executable?
2. Running an executable without exec
3. Position-independent code
4. ELF relocations
5. The simplest shared library
6. Loading multiple ELF objects
7. Dynamic symbol resolution
8. Dynamic linker speed and correctness
9. GDB scripting and Indirect functions
10. Safer memory-mapped structures
11. More ELF relocations
12. A no_std Rust binary
13. Thread-local storage

See also

• readelf
• Core dump
• a.out
• PE (Windows)
• AppImage
• elfcat

Favorite site

• Wikipedia (en) description of ELF
• Wrapping up the Linker - all the way to ELF and fromelf! ²
• ELF File Format ³
• SPARC Assembler Memory Map
• What is ELF? ⁴
• Executable and Linkable Format (ELF) ⁵

References