https://github.com/helyousfi/nasm

https://github.com/helyousfi/nasm

Last synced: 7 months ago
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• Host: GitHub
• URL: https://github.com/helyousfi/nasm
• Owner: helyousfi
• Created: 2024-09-29T15:32:49.000Z (about 1 year ago)
• Default Branch: main
• Last Pushed: 2024-10-03T15:25:29.000Z (about 1 year ago)
• Last Synced: 2025-02-26T20:37:17.419Z (7 months ago)
• Language: Assembly
• Size: 48.8 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: readme.md

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README

          

# 86 Architecture

## BIOS

- BIOS is firmware embedded on a motherboard that initializes hardware components and prepares the system for booting an operating system.

- A bootloader is a small program that loads the operating system into memory when the computer starts up.

![32architecture](https://github.com/user-attachments/assets/a6da0e28-ee22-4ddf-9c94-540c463a7580)

# Registers

![image](https://github.com/user-attachments/assets/8066da44-ef01-4a39-9a0c-19a2f9271db3)

## EIP

EIP (Extended Instruction Pointer) is a 32-bit register in the x86 architecture.

It holds the memory address of the next instruction that the CPU will execute.

## FSM

The FSM (Flag Status Register) in x86 architecture is a special register that contains flags indicating the status of the CPU after an arithmetic or logical operation.

## The main internal bus

The main internal bus in a computer system refers to the set of pathways (wires) used to transfer data, addresses, and control signals between the CPU, memory, and other peripherals. 

# Special Purpose Registers

![2](https://github.com/user-attachments/assets/c5ea8319-c35d-477b-a23a-527d989f0db6)

# Assemble the program

nasm -f elf32 hello.asm -o hello.o

# Link the object files

ld -m elf_i386 -s -o hello hello.o

## 1. nasm -f elf32 hello.asm -o hello.o

    - nasm: Assembler for x86 assembly language.

    - -f elf32: Specifies the output format. elf32 indicates a 32-bit ELF (Executable and Linkable Format) object file. Since hello.asm is likely a 32-bit assembly program, the elf32 format is appropriate.

    

In short, this command assembles the hello.asm file into an object file hello.o using the 32-bit ELF format.

## 2. ld -m elf_i386 -o hello hello.o

    ld: The linker command. It links the object files produced by the assembler into an executable file.

    -m elf_i386: Specifies the target format for the linker. elf_i386 tells ld to create a 32-bit ELF executable for the i386 architecture.

    -o hello: Specifies the name of the final output executable file. In this case, the executable will be named hello.

    hello.o: The input object file that was produced in the previous step (hello.o). This file contains the machine code generated from hello.asm.

    

# Syscalls

![system calls-Programming Ethical Hacker Way by sandeep saini](https://github.com/user-attachments/assets/9d81ec4a-45ed-454b-80e6-75b088a8bb3b)

# Standard File Descriptors:

![image](https://github.com/user-attachments/assets/be5adc43-5250-4560-ad72-09d503d989b2)

# Resources 

https://www.linuxjournal.com/article/4048

https://www.youtube.com/watch?v=busHtSyx2-w&list=PLetF-YjXm-sCH6FrTz4AQhfH6INDQvQSn&index=3