thinkphp/Assembly

Kick off Assembly

Assembly Language Courseware:

1. Introduction

• What is assembly language?
• Why learn assembly?
• Brief history of assembly languages

2. Setting Up the Environment

• Installing NASM
• Setting up a text editor
• Basic command-line usage for assembling and linking

3. NASM Syntax Basics

• Structure of a NASM program
• Comments, labels, and directives
• Basic instructions (MOV, ADD, SUB)

4. Number Representation

• Binary and hexadecimal systems
• Signed and unsigned integers
• Little-endian vs Big-endian

5. Memory and Registers

• CPU registers (general-purpose, segment, and special registers)
• Memory addressing modes
• Stack operations

6. Basic Arithmetic Operations

• Addition and subtraction
• Multiplication and division
• Bitwise operations

7. Adding Two Numbers: Step-by-Step

1. Program structure
2. Declaring variables
3. Moving data into registers
4. Performing addition
5. Storing the result
6. Displaying the result

8. Sample Program: Adding Two Numbers

• Walkthrough of a complete NASM program
• Explanation of each line of code
• Assembling and running the program

9. Debugging and Troubleshooting

• Common errors and how to fix them
• Using a debugger (e.g., GDB) with assembly code

10. Practice Exercises

- Modify the program to add three numbers
- Implement subtraction of two numbers
- Create a program that adds user input numbers

11. Advanced Topics (Optional)

- Floating-point arithmetic
- SIMD instructions for parallel addition
- Optimizing addition operations

12. Resources for Further Learning

- Recommended books and online tutorials
- Assembly language forums and communities

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Assembly x86-64

admin@ironman:~$ nasm -felf64 factorial.asm && gcc -std=c99 factorial.o factorial.c && ./a.out
admin@ironman:~$ nasm -felf64 maxofthree.asm && gcc maxofthree.o max.c && ./a.out

Adding Two Numbers in NASM

section .data
    prompt1 db "Enter the first number: ", 0
    prompt2 db "Enter the second number: ", 0
    fmt_input db "%ld", 0
    fmt_output db "The sum is: %ld", 10, 0

section .bss
    num1 resq 1
    num2 resq 1

section .text
    global main
    extern printf
    extern scanf

main:
    ; Prologue
    push rbp
    mov rbp, rsp

    ; Prompt for first number
    mov rdi, prompt1
    xor eax, eax
    call printf

    ; Read first number
    mov rdi, fmt_input
    mov rsi, num1
    xor eax, eax
    call scanf

    ; Prompt for second number
    mov rdi, prompt2
    xor eax, eax
    call printf

    ; Read second number
    mov rdi, fmt_input
    mov rsi, num2
    xor eax, eax
    call scanf

    ; Perform addition
    mov rax, [num1]
    add rax, [num2]

    ; Print result
    mov rdi, fmt_output
    mov rsi, rax
    xor eax, eax
    call printf

    ; Epilogue
    mov rsp, rbp
    pop rbp

    ; Exit program
    xor eax, eax
    ret   

Max of two numbers

default rel

section .data
    prompt1 db "Enter the first number: ", 0
    prompt2 db "Enter the second number: ", 0
    fmt_input db "%ld", 0
    fmt_output db "The maximum is: %ld", 10, 0

section .bss
    num1 resq 1
    num2 resq 1

section .text
    global main
    extern printf
    extern scanf

main:
    push rbp
    mov rbp, rsp

    ; Prompt and read first number
    lea rdi, [prompt1]
    xor eax, eax
    call printf

    lea rdi, [fmt_input]
    lea rsi, [num1]
    xor eax, eax
    call scanf

    ; Prompt and read second number
    lea rdi, [prompt2]
    xor eax, eax
    call printf

    lea rdi, [fmt_input]
    lea rsi, [num2]
    xor eax, eax
    call scanf

    ; Compare numbers and find max
    mov rax, [num1]
    mov rbx, [num2]
    cmp rax, rbx
    jge print_result  ; Jump if num1 >= num2
    mov rax, rbx      ; If num2 > num1, move num2 to rax

print_result:
    lea rdi, [fmt_output]
    mov rsi, rax
    xor eax, eax
    call printf

    mov rsp, rbp
    pop rbp

    xor eax, eax
    ret

Save the code to a file, e.g., max_numbers.asm
nasm -f elf64 max_numbers.asm
gcc max_numbers.o -o max_numbers -no-pie

Reference:

https://www.nasm.us/xdoc/2.15.05/html/nasmdoc0.html