function::u_register - Linux


The function::u_register command in Linux is designed to register user-defined functions in the kernel. It facilitates the creation and use of custom functions that can be seamlessly integrated into various kernel modules and applications. This command empowers developers to extend the functionality of the kernel by defining their own specialized functions.


function::u_register [-h] [-s SIZE] [-n NAME] [-u] [-r] func


  • -h: Displays the help message and usage information.
  • -s SIZE: Specifies the size of the function in bytes. If not provided, a default value is used.
  • -n NAME: Assigns a name to the function. This name can be used to refer to the function later.
  • -u: Marks the function as user-defined. By default, all registered functions are marked as kernel-defined.
  • -r: Requests the removal of the registered function.


1. Registering a function:

function::u_register -s 1024 -n my_function my_function.o

2. Unregistering a function:

function::u_register -r my_function

3. Registering a function as user-defined:

function::u_register -u -s 512 -n my_ud_function my_ud_function.o

Common Issues

  • Function not found: Ensure that the specified function file exists and is accessible.
  • Insufficient size: The size specified using the -s option must be adequate for the function’s needs. Adjust the size accordingly.
  • Duplicate function name: Each function must have a unique name. If a duplicate name is provided, the registration will fail.


function::u_register can be integrated with other kernel modules or applications to extend their functionality. For instance, a custom function can be registered to handle a specific type of hardware interrupt or to perform specialized computations within the kernel.

Related Commands

  • sysfs: Interface for exporting kernel objects to the user space file system.
  • kobject: Framework for creating and managing kernel objects.
  • module: Allows the creation and management of loadable kernel modules.