Videos: ELF

Note: the final, optional video is not included in the playlist.

On Linux and most Unix variants (but not Mac OS X), executables, object files, and shared libraries all use a format known as ELF (Executable and Linkable Format). These videos look at the kinds of problems that the representation must solve and the details of how programs and libraries are represented in ELF.

• ELF 1: Overview   3:00
  A general overview of ELF.

• ELF 2: Segments, sections, and headers   5:20
  More details on the way ELF represents run-time and link-time views of code.

• ELF 3: Using readelf   5:00
  A demonstration of using readelf to print a human-readable summary of the content of an ELF file.

• ELF 4: Reading ELF programmatically   5:04
  Diving into details of ELF by implementing a readelf-like program that report an ELF file’s type.

• ELF 5: Offsets vs. addresses   5:07
  A discussion of the ways that ELF content refers to other content in the same ELF file: either as a file offset, or as a (predicted) run-time address.

• ELF 6: Objects and linking   6:28
  How object files are linked at the ELF level to produce an ELF executable.

• ELF 7: Printing section names   4:55
  More details on ELF by extending the readelf-like program to list the sections in an ELF file, which especially demonstrates how to read strings (in this case, section names) from a string table.

• ELF 8: Position-independent code   3:19
  Why shared libraries need position-independent code and, at a high level, how position-independent code works.

• ELF 9: Implementing PIC variables   3:02
  Details on how variables are referenced in position-independent code and how that implementation is represented in ELF.

• ELF 10: Implementing PIC functions   2:53
  Details on how function calls are referenced in position-independent code and how that implementation is represented in ELF.

• ELF 11: Inspecting the symbol table   5:34
  More details on ELF by extending the readelf-like program to list the symbols in an ELF file.

• ELF 12: Inspecting relocations   0:57
  A brief investigation of the content of relocation sections—that is, the sections that relate variables and functions used by position-independent code to the places that they are used.

• ELF 13: Machine code section   3:24
  Examples of how machine code in a ELF file can be understood.

• Optional ELF 14: Some maps to ELF   6:54
  Explanation of some maps to help navigate ELF files in memory, which should help with the homework assignment.