User:Imate900/32-bit assembler bare bones: Difference between revisions
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{{Rating|2}}{{Template:Kernel designs}} |
<!--{{Rating|2}}{{Template:Kernel designs}}--> |
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''This tutorial will teach you how to make a 32-bit Assembly kernel.'' |
''This tutorial will teach you how to make a 32-bit Assembly kernel.'' |
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== GRUB == |
== GRUB == |
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All we need is something like this (Nasm): |
All we need is something like this (Nasm): |
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< |
<syntaxhighlight lang="asm"> |
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%define MBOOT_MAGIC 0x1badb002 |
%define MBOOT_MAGIC 0x1badb002 |
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%define MBOOT_FLAGS 0x00010002 |
%define MBOOT_FLAGS 0x00010002 |
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align 4, db 0 |
align 4, db 0 |
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end_of_file: |
end_of_file: |
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</syntaxhighlight> |
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</source> |
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Link with: |
Link with: |
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< |
<syntaxhighlight lang="bash"> |
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nasm -f bin kernel.asm |
nasm -f bin kernel.asm |
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</syntaxhighlight> |
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</source> |
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Make sure you have a GRUB entry... |
Make sure you have a GRUB entry... |
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== Without GRUB == |
== Without GRUB == |
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If your bootloader loads flat binary images and gives you protected mode for you, use this code as a basis: |
If your bootloader loads flat binary images and gives you protected mode for you, use this code as a basis: |
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< |
<syntaxhighlight lang="asm"> |
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_start: |
_start: |
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; Write kernel here. It might be good to load a new GDT. |
; Write kernel here. It might be good to load a new GDT. |
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string: db "Hello world!", 0 |
string: db "Hello world!", 0 |
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</syntaxhighlight> |
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</source> |
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If you start out in real mode, remember to switch to [[Protected Mode]]. |
If you start out in real mode, remember to switch to [[Protected Mode]]. |
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Good luck writing your 32-bit Assembly kernel! '''But''', there ''ARE'' catch-yas! |
Good luck writing your 32-bit Assembly kernel! '''But''', there ''ARE'' catch-yas! |
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*As soon as possible, load a new GDT. |
*As soon as possible, load a new GDT. |
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*You must not depend on the BIOS to do everything for you. Most |
*You must not depend on the BIOS to do everything for you. Most prominent are disk access, printing to the screen (this tutorial has a way to printing: writing to 0xb8000) and reading keys from the keyboard. No BIOS ints will help and only cause a GPF. |
Latest revision as of 06:16, 9 June 2024
This tutorial will teach you how to make a 32-bit Assembly kernel.
Preface
Most OSes are in C, but you may consider it in Assembly. This is moderate-easy, and requires knowing GRUB and Assembly.
GRUB
All we need is something like this (Nasm):
%define MBOOT_MAGIC 0x1badb002
%define MBOOT_FLAGS 0x00010002
bits 32
org 0x100000
align 4, db 0
header:
dd MBOOT_MAGIC
dd MBOOT_FLAGS
dd 0 - MBOOT_MAGIC - MBOOT_FLAGS
dd header
dd __entry_point
dd end_of_file
dd end_of_file
dd __entry_point
align 0, db 0
__entry_point:
mov edi, 0xB8000
mov esi, string
mov ah, 0x0F
.displaying:
lodsb
stosw
or al, al
jnz .displaying
jmp short $
string: db "Hello world!", 0
align 4, db 0
end_of_file:
Link with:
nasm -f bin kernel.asm
Make sure you have a GRUB entry...
title Assembler Barebones kernel (hd0,0)/boot/kernel.bin
Now, reboot, and enjoy!
Without GRUB
If your bootloader loads flat binary images and gives you protected mode for you, use this code as a basis:
_start:
; Write kernel here. It might be good to load a new GDT.
mov edi, 0xB8000
mov esi, string
mov ah, 0x0F
.displaying:
lodsb
stosw
or al, al
jnz .displaying
jmp short $
string: db "Hello world!", 0
If you start out in real mode, remember to switch to Protected Mode.
Postface
Good luck writing your 32-bit Assembly kernel! But, there ARE catch-yas!
- As soon as possible, load a new GDT.
- You must not depend on the BIOS to do everything for you. Most prominent are disk access, printing to the screen (this tutorial has a way to printing: writing to 0xb8000) and reading keys from the keyboard. No BIOS ints will help and only cause a GPF.