Excellent series for learning the basic of ELF file format internals
Part 1: https://intezer.com/blog/research/executable-linkable-format-101-part1-sections-segments/
Part 2: https://intezer.com/blog/malware-analysis/executable-linkable-format-101-part-2-symbols/
Part 3: https://intezer.com/blog/malware-analysis/executable-and-linkable-format-101-part-3-relocations/
Part 4: https://intezer.com/blog/malware-analysis/executable-linkable-format-101-part-4-dynamic-linking/

