asm-x86

x86 Assembly (Intel) (Elite)

When to use

• You need to read/write x86 assembly for performance or low-level debugging.

• You need to understand calling conventions, stack frames, and registers.

Calling Convention Reference

Convention	Platform	Args	Return	Caller-saved	Callee-saved
cdecl	x86 Linux/Windows	Stack (right-to-left)	eax	eax,ecx,edx	ebx,esi,edi,ebp
System V AMD64	x64 Linux/macOS	rdi,rsi,rdx,rcx,r8,r9	rax	r10,r11	rbx,r12–r15,rbp
Microsoft x64	x64 Windows	rcx,rdx,r8,r9	rax	rax,rcx,rdx,r8,r9,r10,r11	rbx,rdi,rsi,r12–r15,rbp

Workflow

1. Establish context

• Architecture (x86/x64), OS, calling convention, toolchain.

• Identify the function boundary (prologue/epilogue).

2. Read control flow

• Trace prologue (stack frame setup) and epilogue (teardown).

• Identify register saving/restoring patterns.

3. Trace data flow

• Track values through registers and memory operands.

• Note sign/zero extension issues (movzx/movsx).

4. Debug effectively

• Minimal repro, disassembly (objdump -d, gdb, windbg).

• Set breakpoints at function entry; inspect registers and stack.

5. Safety review

• Check alignment (stack 16-byte aligned before call on x64).

• Look for buffer overflows, off-by-one stack usage.

• Watch for UB and platform-specific behavior.

Self-check

• Calling convention identified and respected.

• Stack frame alignment verified (x64: 16-byte aligned before call).

• Caller-saved vs callee-saved registers correctly handled.

• Data flow traced for all inputs/outputs of the function.

• Debugger used to confirm hypothesis before declaring fix.

Outputs

• Calling convention and stack frame summary.

• Debugging checklist (gdb/lldb/windbg commands).

• "What to inspect" list (registers/stack/memory).