Assembly Tutorial

This will be a basic assembly tutorial focusing on how to assemble the JIT function x86 instructions.

Until the fortunate arrival of that glorious day, I recommend these excellent tutorials:

• A fundamental introduction to x86 assembly programming
• Guide to x86 Assembly, and the same with AT&T syntax
• Say hello to x86_64 Assembly
• GNU Assembler Examples
• Where the top of the stack is on x86
• Stack frame layout on x86-64

Notes

• Passing arguments
• Function call ABIs
• Assembler Tools
• Debuggers

Passing arguments

In 64-bit x86 code, you pass the first few parameters in registers.

Exactly which registers you use depends on the CPU arch and how the OS uses it.

On x86-64 Linux the first six parameters go into:

rdi, rsi, rdx, rcx, r8, r9

On Windows x64, the first four parameters go into:

rcx, rdx, r8, r9

On 32-bit x86 systems parameters are passed on the stack.

Function call ABIs

x86-32 Windows uses various ABIs for function calls. Win32 uses “stdcall” as the default, function arguments are passed on the stack in reverse order.

x86-32 Linux can use “stdcall”.

x86-64 Linux uses “System V ABI” for function calls. Pass arguments in registers.

Assembler Tools

• nasm
• gas, GNU Assembler
• Online x86 and x64 Intel Instruction Assembler

Debuggers

• gdb (Linux)
• hopper (Mac)