How to Resolve – insmod: ERROR: could not insert module hello.ko: Unknown symbol in module – unknown symbol class_unregister

We tried to write a simple class driver framework which will create a directory in /sys/class, we were able to compile the code but got the following error while trying to install the driver as,

 $ sudo insmod hello.ko 
insmod: ERROR: could not insert module hello.ko: Unknown symbol in module 
$ dmesg

[ 7514.340407] hello: Unknown symbol __class_register (err 0)
[ 7514.340436] hello: Unknown symbol class_unregister (err 0) 

Solution :

The function __class_create is exported only for GPL modules (exported with EXPORT_SYMBOL_GPL). So, you need to use a GPL license with MODULE_LICENSE macro to make use of that function.

Hence if you append your driver code with

 MODULE_LICENSE("GPL"); 

and recompile driver and try insmod again, it will definately work and you will not get such errors.

Reference – https://stackoverflow.com/questions/29578931/unknown-symbol-class-create-err-0

Android Android Commands Android Java Applications Application Libraries Application Stack / User Interface Bash / Shell Scripts Commands and Packages Compilation Content Management System - CMS Core Kernel C Programs Development & Build Development Environment Setup Errors & Failures Flutter git Go Language Programs Hardware Platforms HTML JAVA Programs Kernel & Device Drivers Linux, OS Concepts and Networking Linux Device Drivers Linux Host, Ubuntu, SysAdmin Linux Kernel Linux Networking Middleware Libraries, HAL Monetization / Google AdSense Multimedia - Audio, Video, Images NDK / Middleware / HAL OS Concepts PHP Programming Languages RaspberryPi Scripting and Automation Search Engine Optimisation ( SEO ) Social Media Socurce Code Management ( SCM ) System Administration, Security Testing and Debugging Uncategorized User Interface Web design and development Wordpress Yocto / Bitbake / Openembedded

Leave a Reply / Ask Question