UEFI-Tuts

EFI for OS Development from scratch
THIS IS NO LONGER IN DEVELOPMENT. USE AT YOUR OWN RISK. THIS IS NOT AN OPERATING SYSTEM, JUST A BOOTLOADER.

LICENSE / COPYRIGHT

MIT License
Copyright (c) 2026 ThatOSDev 
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: 
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 

NOTES

• UPDATED NOTE (6-3-2024) --- GCC 13.2 has an issue compiling the GDT. There is a FIX. Add the Q to the end of both of the PUSH statements. pushq. This will allow newer GCC compiler versions to compile the code just fine.

• All code has been tested as working against GCC 11.2.0.

• I am now officially done with the OSDev world. This is here for anyone at their own risk.

• There are two tuts on how to use the GDT. Just showing that there is more then one way to "skin the cat".

• WARNING - This code is for teaching purposes only. It is not written for professional use. Some code is written in order to speed up teaching, and thus is not properly coded. You should rewrite the code for your own professional use.

• For video 33 ( which is Code 29 on Github ), I am using FASM. However, that code in that video is not guaranteed to be the same.

• Open source Tool to create an EFI based GPT Partitioned virtual HDD file. Big THANK YOU to Hamid Nazari for his hard work on creating this tool. The source code should work on all platforms and will make OS Development that much easier.

• You might have noticed in my re-uploaded code that I am using includes from the C standard. There is nothing wrong with that. So I am sharing that it does work in this re-uploaded code. The videos just show that you can do it without the standard C library headers.

• THE TUTORIALS ON YOUTUBE ARE WINDOWS BASED, BUT CODE SHOULD WORK IN LINUX AND MAC.

• UEFI 2.9 Specs PDF : https://uefi.org/specifications

• NOTICE : The 40 meg file is still there, and can now be used by MAC and Linux users. The 256 meg file is in the ZIP inside of the HOLD folder for those who want a larger drive.hdd file to play with. All Operating System users CAN use that size file too.

• The original HDD IMAGECREATOR software has been removed. It has been replaced with the new tool coded by Hamid Nazari.

BUILD INSTRCUTIONS

Linux, Mac, Windows
[https://codeberg.org/ThatOSDev/UEFI-Tuts/src/branch/master/BUILD.md)

READ THIS !!!

• THINGS YOU SHOULD KNOW BEFORE STARTING OS DEVELOPMENT
  • The C Language
  • Assembly Language
  • How to read Hex Code ( Example : 0x8664 )
  • How your Host Operating System works ( Such as windows or linux )
  • How your compiler works ( Such as GCC )
  • How to do research ( Don't be lazy )
• BEGINNER MISTAKES : https://wiki.osdev.org/Beginner_Mistakes

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