🐛 Debugging Assembly Programs

Debugging Assembly means knowing exactly what the CPU’s doing at every step. You track registers, flags, memory, and instructions to catch bugs or weird behavior.

Since Assembly is low-level, even small mistakes can cause big headaches. Using tools and techniques to trace execution is key to avoid going insane.

🛠️ Common Debugging Techniques

step through instructions — execute line-by-line to watch changes
inspect registers — check values in eax, ebx, ecx, edx, etc.
watch memory — monitor data in buffers and stack
use breakpoints — pause execution at specific points
check flags — zero, carry, sign flags affect conditional jumps

🔍 Why Debugging Is Critical

Assembly language is unforgiving. One wrong register or an incorrect jump can cause crashes, data corruption, or totally unpredictable behavior. Debugging helps you verify each CPU instruction does exactly what you intended. Without careful debugging, your code might run but produce subtle bugs that are insanely hard to track down later.

📚 Example: Simple Add with Debug Comments

section .text
    global _start

_start:
    mov eax, 10       ; Load 10 into eax
    mov ebx, 5        ; Load 5 into ebx
    add eax, ebx      ; eax = eax + ebx (should be 15)
    ; Debug: Check eax here

    mov ecx, eax      ; Move result to ecx
    sub ecx, 3        ; ecx = ecx - 3 (should be 12)
    ; Debug: Check ecx here

    mov eax, 1        ; sys_exit
    int 0x80

⚠️ Example: Faulty Code with Bug

section .text
    global _start

_start:
    mov eax, 10
    mov ebx, 0
    div ebx          ; BUG: Division by zero crash
    mov eax, 1
    int 0x80

Debug trace will appear here...

💡 Pro Tip: Use tools like gdb, edb-debugger, or radare2 to step through Assembly code interactively.