162 lines
3.4 KiB
Markdown
162 lines
3.4 KiB
Markdown
# Simple UEFI Operating System
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A minimal bootable UEFI operating system written in C that demonstrates basic UEFI functionality.
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## Features
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- **UEFI Boot**: Boots directly on UEFI firmware
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- **Console I/O**: Interactive keyboard input and screen output
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- **System Information**: Displays firmware details
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- **Simple Commands**: Interactive command interface
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## Requirements
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- GCC compiler
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- GNU-EFI library
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- QEMU with OVMF firmware
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- Make
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## Installation
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### On Debian/Ubuntu:
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```bash
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make install-deps
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```
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Or manually:
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```bash
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sudo apt-get install gnu-efi qemu-system-x86 ovmf gcc binutils make
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```
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### On Arch Linux:
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```bash
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sudo pacman -S gnu-efi qemu-system-x86 edk2-ovmf gcc binutils make
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```
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### On Fedora/RHEL:
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```bash
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sudo dnf install gnu-efi qemu-system-x86 edk2-ovmf gcc binutils make
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```
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## Building
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Build the UEFI application:
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```bash
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make
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```
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This will create `build/EFI/BOOT/BOOTX64.EFI`
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## Running
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Test with QEMU (no graphics mode):
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```bash
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make run
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```
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### QEMU Controls:
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- **Exit QEMU**: Press `Ctrl+A`, then `X`
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- **Shutdown OS**: Press `q` in the OS
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## Commands in the OS
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Once the OS boots, you can use these commands:
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- `h` - Display help
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- `i` - Display system information
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- `c` - Clear screen
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- `q` - Shutdown the system
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## Project Structure
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```
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.
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├── main.c # Main UEFI application source code
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├── Makefile # Build configuration
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└── README.md # This file
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```
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## How It Works
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1. **UEFI Entry Point**: The `efi_main` function is the entry point called by UEFI firmware
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2. **Initialization**: GNU-EFI library is initialized with the system table
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3. **Console Setup**: Output is configured and screen is cleared
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4. **Main Loop**: The OS enters a loop waiting for keyboard input
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5. **Command Processing**: User commands are processed and executed
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6. **Shutdown**: UEFI runtime services are used to shutdown the system
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## Building for Real Hardware
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To create a bootable USB drive:
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1. Build the project: `make`
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2. Format a USB drive with GPT and create an EFI partition (FAT32)
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3. Mount the EFI partition
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4. Copy `build/EFI/BOOT/BOOTX64.EFI` to `/EFI/BOOT/` on the USB drive
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5. Boot from the USB drive in UEFI mode
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**Warning**: Always backup your data before creating bootable media!
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## Cleaning
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Remove build artifacts:
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```bash
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make clean
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```
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## Troubleshooting
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### GNU-EFI headers not found
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Make sure GNU-EFI is installed. The headers are typically in `/usr/include/efi`.
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If installed in a different location, update the `EFI_INC` variable in the Makefile.
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### OVMF firmware not found
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OVMF files might be in different locations depending on your distribution:
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- `/usr/share/OVMF/`
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- `/usr/share/qemu/`
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- `/usr/share/edk2-ovmf/`
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Update the paths in the Makefile if needed.
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### QEMU crashes or fails to start
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Ensure you have QEMU with x86_64 support and OVMF firmware installed.
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## Technical Details
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- **Architecture**: x86_64
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- **Firmware Interface**: UEFI 2.x
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- **Development Library**: GNU-EFI
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- **Executable Format**: PE32+ (Portable Executable for EFI)
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- **Boot Protocol**: UEFI Boot Services
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## License
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This is a minimal educational example. Feel free to use and modify as needed.
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## Further Development
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Ideas for expansion:
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- File system support
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- Memory management
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- Graphics output
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- Network stack
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- Device drivers
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- Multi-tasking
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## Resources
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- [UEFI Specification](https://uefi.org/specifications)
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- [GNU-EFI Documentation](https://sourceforge.net/projects/gnu-efi/)
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- [OSDev Wiki](https://wiki.osdev.org/)
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