Kernel loading technology/LKM technology

Many desktop operating systems, such as Linux, provide LKM (LoadableKernelModule) to dynamically extend their kernels. When a module is installed in the kernel, it becomes a part of the kernel and does not undergo real-time security checks, running at full speed. In embedded Linux systems, the main issues with LKM are the need for storage modules to occupy additional space and the security of loaded modules. The security issues of modules can be solved through software protection technology.

Oikawa et al. proposed a dynamic core module (DKMs) technology similar to LKM in 1996. Like LKM, DKMs are stored in the form of files and can be dynamically loaded and unloaded during system operation. DKMs are managed by a user layer DKM server, not by the kernel. When the core requires a certain module, the DKM server is responsible for loading the corresponding DKM; When the core memory resources are scarce, the DKM server is responsible for uninstalling an unused DKM. The disadvantage is that all DKMs are stored on the local system, taking up a lot of valuable storage space.

Unlike Oikawa’s method, Chang DaWei et al. proposed the Operating System Portal framework (OSP) method in 2003. This method stores the core modules on a remote server with sufficient resources, and is managed by the server-side tool OSPortal. It is also responsible for processing requests from the client (embedded system kernel), dynamically selecting and connecting modules according to the requests, and then transmitting them to the client through the network. Due to the management and connection of modules being on the server side, it can save a lot of resource space for the client.