My reference was the "System V Application Binary Interface" itself (chapter 4). It's not that difficult to grok.

https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf

Just read the ELF specification. There is a header and everything else follows. There are a lot of explanations online, here is one: https://www.cs.cmu.edu/afs/cs/academic/class/15213-f00/docs/...