Initial commit, working

.gitignore

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+# Build directory
+build/
+
+# Object files
+*.o
+*.so
+*.efi
+*.EFI
+
+# Editor files
+*.swp
+*.swo
+*~
+.vscode/
+.idea/
+
+# OS files
+.DS_Store
+Thumbs.db

Makefile

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+# Makefile for UEFI Operating System
+
+# Architecture
+ARCH = x86_64
+
+# Compiler and tools
+CC = gcc
+LD = ld
+OBJCOPY = objcopy
+
+# Directories
+SRC_DIR = .
+BUILD_DIR = build
+EFI_DIR = $(BUILD_DIR)/EFI/BOOT
+IMAGE_DIR = $(BUILD_DIR)/image
+
+# GNU-EFI paths (common locations)
+EFI_INC = /usr/include/efi
+EFI_INCLUDES = -I$(EFI_INC) -I$(EFI_INC)/$(ARCH) -I$(EFI_INC)/protocol
+EFI_LDS = /usr/lib/elf_$(ARCH)_efi.lds
+EFI_CRT_OBJS = /usr/lib/crt0-efi-$(ARCH).o
+EFI_LIB_PATHS = -L/usr/lib
+
+# Compiler flags
+CFLAGS = -ffreestanding -fno-stack-protector -fpic \
+         -fshort-wchar -mno-red-zone -Wall -Wextra \
+         $(EFI_INCLUDES) -DEFI_FUNCTION_WRAPPER
+
+# Linker flags
+LDFLAGS = -nostdlib -znocombreloc -T $(EFI_LDS) -shared \
+          -Bsymbolic $(EFI_LIB_PATHS) $(EFI_CRT_OBJS)
+
+# Libraries
+LIBS = -lefi -lgnuefi
+
+# Target
+TARGET = BOOTX64.EFI
+TARGET_SO = bootx64.so
+OBJ = $(BUILD_DIR)/main.o
+
+# QEMU settings
+QEMU = qemu-system-x86_64
+
+# Try to find OVMF firmware (different locations on different distros)
+OVMF_CODE := $(shell \
+	if [ -f /usr/share/OVMF/OVMF_CODE_4M.fd ]; then \
+		echo /usr/share/OVMF/OVMF_CODE_4M.fd; \
+	elif [ -f /usr/share/OVMF/OVMF_CODE.fd ]; then \
+		echo /usr/share/OVMF/OVMF_CODE.fd; \
+	elif [ -f /usr/share/qemu/OVMF_CODE.fd ]; then \
+		echo /usr/share/qemu/OVMF_CODE.fd; \
+	elif [ -f /usr/share/edk2-ovmf/x64/OVMF_CODE.fd ]; then \
+		echo /usr/share/edk2-ovmf/x64/OVMF_CODE.fd; \
+	else \
+		echo /usr/share/OVMF/OVMF_CODE.fd; \
+	fi)
+
+OVMF_VARS_TEMPLATE := $(shell \
+	if [ -f /usr/share/OVMF/OVMF_VARS_4M.fd ]; then \
+		echo /usr/share/OVMF/OVMF_VARS_4M.fd; \
+	elif [ -f /usr/share/OVMF/OVMF_VARS.fd ]; then \
+		echo /usr/share/OVMF/OVMF_VARS.fd; \
+	elif [ -f /usr/share/qemu/OVMF_VARS.fd ]; then \
+		echo /usr/share/qemu/OVMF_VARS.fd; \
+	elif [ -f /usr/share/edk2-ovmf/x64/OVMF_VARS.fd ]; then \
+		echo /usr/share/edk2-ovmf/x64/OVMF_VARS.fd; \
+	else \
+		echo /usr/share/OVMF/OVMF_VARS.fd; \
+	fi)
+
+QEMU_FLAGS = -machine q35 \
+             -drive if=pflash,format=raw,readonly=on,file=$(OVMF_CODE) \
+             -drive if=pflash,format=raw,file=$(BUILD_DIR)/OVMF_VARS.fd \
+             -drive format=raw,file=fat:rw:$(BUILD_DIR) \
+             -net none \
+             -nographic
+
+# Phony targets
+.PHONY: all clean run setup install-deps
+
+# Default target
+all: setup $(EFI_DIR)/$(TARGET)
+
+# Create necessary directories
+setup:
+	@mkdir -p $(BUILD_DIR)
+	@mkdir -p $(EFI_DIR)
+	@mkdir -p $(IMAGE_DIR)
+
+# Compile source files
+$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c
+	@echo "Compiling $<..."
+	$(CC) $(CFLAGS) -c $< -o $@
+
+# Link to create shared object
+$(BUILD_DIR)/$(TARGET_SO): $(OBJ)
+	@echo "Linking $@..."
+	$(LD) $(LDFLAGS) $(OBJ) -o $@ $(LIBS)
+
+# Convert to EFI application
+$(EFI_DIR)/$(TARGET): $(BUILD_DIR)/$(TARGET_SO)
+	@echo "Creating EFI application..."
+	$(OBJCOPY) -j .text -j .sdata -j .data -j .dynamic \
+	           -j .dynsym -j .rel -j .rela -j .reloc \
+	           --target=efi-app-$(ARCH) $< $@
+	@echo "Build complete: $@"
+
+# Run with QEMU
+run: all
+	@echo "Starting QEMU..."
+	@echo "Using OVMF firmware: $(OVMF_CODE)"
+	@if [ ! -f $(BUILD_DIR)/OVMF_VARS.fd ]; then \
+		echo "Creating OVMF_VARS.fd from template..."; \
+		cp $(OVMF_VARS_TEMPLATE) $(BUILD_DIR)/OVMF_VARS.fd 2>/dev/null || \
+		dd if=/dev/zero of=$(BUILD_DIR)/OVMF_VARS.fd bs=1M count=64 2>/dev/null; \
+	fi
+	@echo "================================================"
+	@echo "QEMU is starting in nographic mode"
+	@echo "To exit QEMU: Press Ctrl+A, then X"
+	@echo "In the OS: Press 'q' to shutdown"
+	@echo "================================================"
+	$(QEMU) $(QEMU_FLAGS)
+
+# Clean build artifacts
+clean:
+	@echo "Cleaning build directory..."
+	rm -rf $(BUILD_DIR)
+	@echo "Clean complete."
+
+# Install dependencies (for Debian/Ubuntu)
+install-deps:
+	@echo "Installing dependencies..."
+	sudo apt-get update
+	sudo apt-get install -y gnu-efi qemu-system-x86 ovmf gcc binutils make
+	@echo "Dependencies installed."
+
+# Help target
+help:
+	@echo "UEFI Operating System Makefile"
+	@echo ""
+	@echo "Targets:"
+	@echo "  all          - Build the UEFI application (default)"
+	@echo "  run          - Build and run with QEMU"
+	@echo "  clean        - Remove build artifacts"
+	@echo "  install-deps - Install required dependencies (Debian/Ubuntu)"
+	@echo "  help         - Display this help message"
+	@echo ""
+	@echo "Usage:"
+	@echo "  make              # Build the OS"
+	@echo "  make run          # Build and run in QEMU"
+	@echo "  make clean        # Clean build files"
+	@echo "  make install-deps # Install dependencies"

README.md

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

main.c

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+#include <efi.h>
+#include <efilib.h>
+
+EFI_STATUS
+EFIAPI
+efi_main(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
+{
+    EFI_STATUS Status;
+    EFI_INPUT_KEY Key;
+    
+    // Initialize the GNU-EFI library
+    InitializeLib(ImageHandle, SystemTable);
+    
+    // Clear the screen
+    uefi_call_wrapper(ST->ConOut->ClearScreen, 1, ST->ConOut);
+    
+    // Set text color to light green
+    uefi_call_wrapper(ST->ConOut->SetAttribute, 2, ST->ConOut, 
+                     EFI_TEXT_ATTR(EFI_LIGHTGREEN, EFI_BLACK));
+    
+    // Print welcome messages
+    Print(L"================================================\n\r");
+    Print(L"  Welcome to Simple UEFI Operating System!\n\r");
+    Print(L"================================================\n\r");
+    Print(L"\n\r");
+    Print(L"System Information:\n\r");
+    Print(L"  UEFI Firmware Vendor: %s\n\r", ST->FirmwareVendor);
+    Print(L"  UEFI Firmware Revision: %d.%d\n\r", 
+          ST->FirmwareRevision >> 16, ST->FirmwareRevision & 0xFFFF);
+    Print(L"\n\r");
+    
+    // Display some runtime services info
+    Print(L"Available Services:\n\r");
+    Print(L"  - Console Input/Output: Active\n\r");
+    Print(L"  - Runtime Services: Active\n\r");
+    Print(L"  - Boot Services: Active\n\r");
+    Print(L"\n\r");
+    
+    // Simple command loop
+    Print(L"Commands:\n\r");
+    Print(L"  'h' - Display help\n\r");
+    Print(L"  'i' - Display system info\n\r");
+    Print(L"  'c' - Clear screen\n\r");
+    Print(L"  'q' - Shutdown\n\r");
+    Print(L"\n\r");
+    Print(L"Press a key to start...\n\r");
+    
+    while (TRUE) {
+        // Wait for key press
+        Status = uefi_call_wrapper(ST->ConIn->ReadKeyStroke, 2, 
+                                   ST->ConIn, &Key);
+        
+        if (EFI_ERROR(Status)) {
+            continue;
+        }
+        
+        // Handle commands
+        if (Key.UnicodeChar == L'q' || Key.UnicodeChar == L'Q') {
+            Print(L"\n\rShutting down...\n\r");
+            // Reset the system
+            uefi_call_wrapper(RT->ResetSystem, 4, EfiResetShutdown, 
+                            EFI_SUCCESS, 0, NULL);
+        }
+        else if (Key.UnicodeChar == L'h' || Key.UnicodeChar == L'H') {
+            Print(L"\n\r=== Help ===\n\r");
+            Print(L"This is a minimal UEFI operating system.\n\r");
+            Print(L"It demonstrates basic UEFI functionality.\n\r");
+            Print(L"\n\r");
+        }
+        else if (Key.UnicodeChar == L'i' || Key.UnicodeChar == L'I') {
+            Print(L"\n\r=== System Info ===\n\r");
+            Print(L"Firmware Vendor: %s\n\r", ST->FirmwareVendor);
+            Print(L"Firmware Revision: %d.%d\n\r", 
+                  ST->FirmwareRevision >> 16, ST->FirmwareRevision & 0xFFFF);
+            Print(L"UEFI Specification: %d.%d\n\r",
+                  ST->Hdr.Revision >> 16, ST->Hdr.Revision & 0xFFFF);
+            Print(L"\n\r");
+        }
+        else if (Key.UnicodeChar == L'c' || Key.UnicodeChar == L'C') {
+            uefi_call_wrapper(ST->ConOut->ClearScreen, 1, ST->ConOut);
+            Print(L"Screen cleared. Press 'h' for help.\n\r");
+        }
+        else if (Key.UnicodeChar >= 32 && Key.UnicodeChar < 127) {
+            // Echo printable characters
+            Print(L"%c", Key.UnicodeChar);
+        }
+        else if (Key.UnicodeChar == L'\r') {
+            Print(L"\n\r> ");
+        }
+    }
+    
+    return EFI_SUCCESS;
+}