Kernel symbol table

insmod Use the common kernel symbol table to resolve undefined symbols in the module .

The common kernel symbol table contains all the global kernel entries （ Functions and variables ） The address of , This is necessary to implement a modular driver .

Module stacking technology ： New modules can use symbols derived from our own modules , In this way, we can stack new modules on top of other modules .

One module needs to export symbols to other modules , Use the following macros ：

EXPORT_SYMBOL(name);

EXPORT_SYMBOL_GPL(name); # Exported modules can only be GPL Module use under license

Symbols must be exported in the global part of the module file , Cannot export... In a function , Because the above macro is extended to the declaration of a special variable , This variable must be global .