===========================[ amd64 ABI ]========================

Get it: https://www.uclibc.org/docs/psABI-x86_64.pdf

Read sections 3.1 and 3.2; then sections 4 and 5.

On page 20 of the AMD64 ABI document, find how integer and pointer
arguments are passed to functions:

  If the class is INTEGER, the next available register of the sequence %rdi,
  %rsi, %rdx, %rcx, %r8 and %r9 is used.

Note that this is very different from the 32-bit Linux calling convention,
where arguments are pushed onto the stack and referenced off of %esp.

Look at Figure 3.3 on page 16 to see the layout of an amd64 stack frame.

Look at Figure 3.1 on page 12, which shows how different C types are represented.
This table is very important; not understanding these representations leads
to nasty surprises like integer overflows.

===========================[ i386 ABI ]========================

Get it from http://www.sco.com/developers/devspecs/abi386-4.pdf

Find the calling convention description and see that it is obeyed by
complied C code.