Research On Dynamic Loading Mechanism For Embedded Application

The wide application of the embedded system needs good software system to support. The extensible ability of the system has already become one basic demand with the in-depth development of the embedded system. System needs urgently one mechanism which enable us to configure our system at runtime, that is to say we can add module dynamically when system at runtime. This kind of mechanism is dynamic loading mechanism that this thesis will study. Dynamic loading mechanism in this thesis is the mechanism that its application starts from scratch. So system only need a dynamic loading mechanism, which can load dynamically the module and configure the embedded systems which suit different uses.We have analyzed several kinds of loading modes existing at present in this thesis: the dynamic loading mode based on java, the dynamic loading mode of embedded Linux and the principle of the dynamic linking library in Windows. On this basis we have put forward the principle and the process of dynamic loading mechanism for embedded application.Loading is the process of loading modules from external memory or ROM or even from the host development environment into memory ready for running. Dynamic loading means loading at runtime– load modules when program needs. Dynamic loading mechanism use dynamic linking principle to make the system have the ability of dynamic loading and dynamic analyzing. Modules are linked to the system only when be called and carried out. Dynamic loading can be divided into three operations: download, load and unload. Download finishes the operation of downloading object modules from long-distance to native and load operation reads the contents of the module into memory and then analyzes all unresolved reference from outside the module. Unload the module from memory when it is no longer used.About this paper, firstly we takes the life cycle of the object module as main line, and through this line we place more emphasis on the process of loading, processing, executing and unloading of the module. Comparatively analyzed and discussed the background knowledge related with the dynamic loading technology and indicates the key points and development priorities of the loading technology are symbol management, symbol resolution and relocation. Secondly, a solution about these key points is presented. According to all these analyses, proposed a dynamically loaded embedded systems solution, described the relevant data structures and algorithms, designed and implemented the function prototype, and then advanced and validated the feasibility of this embedded software loading mechanism.