USB Device Lister in Assembly (Linux)

This is a simple assembly program (x86 NASM) that lists USB devices connected to a Linux system by reading entries from the /sys/bus/usb/devices/ directory.

How It Works

The program:

1. Uses system calls to open and read the /sys/bus/usb/devices/ directory.
2. Reads each entry in the directory using the getdents syscall.
3. Prints the name of each entry (representing a USB device or related directory entry) to standard output.

Requirements

• Linux system (this code relies on Linux syscalls and directory structure).
• NASM (Netwide Assembler) for assembling the code.
• LD (Linker) for linking the assembled code.

Usage

1. Clone or Download this repository and navigate to the folder containing the assembly file (list_usb.asm).

2. Assemble and Link the code:

   nasm -f elf32 list_usb.asm -o list_usb.o
   ld -m elf_i386 list_usb.o -o list_usb

3. Run the Program:

   ./list_usb

4. Output:

   The program will display a list of entries from /sys/bus/usb/devices/, which should include USB devices connected to your system.

   Connected USB devices:
   Device: usb1
   Device: usb2
   Device: 1-1
   Device: 2-1
   

   Each entry represents a USB device or a related directory entry.

Code Explanation

System Calls Used

• open (syscall 5): Opens the /sys/bus/usb/devices/ directory for reading.
• getdents (syscall 141): Reads directory entries into a buffer.
• write (syscall 4): Outputs directory entry names to the console.
• close (syscall 6): Closes the directory when finished.

Program Flow

• Open Directory: The program starts by opening the /sys/bus/usb/devices/ directory.
• Read Entries: Using getdents, it reads entries into a buffer.
• Display Entries: For each entry in the buffer, the program writes the name to the console.
• Close Directory: After all entries are displayed, the directory is closed, and the program exits.

Notes

• This program is for educational purposes and demonstrates low-level programming and syscall usage in assembly.
• It lists all entries in the /sys/bus/usb/devices/ directory, which may include symbolic links and non-USB files depending on the system configuration.
• To retrieve detailed information about each device, consider using higher-level tools or programs, as assembly does not interpret device metadata.

License

This project is licensed under the MIT License - see the LICENSE file for details.

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Happy low-level programming!