On Fri, Jul 24, 2015 at 11:19 AM, Navy <navych@xxxxxxx> wrote: > Hi > To my understanding, EXPORT_SYMBOL() is used to export a symbol in > kernel/modules. The the address of the all sysbols is in /proc/kallsyms. > Only symbols exported by EXPORT_SYMBOL() is listed its CRC information > in Module.symvers. So I think the CRC is the key to export a symbol. > I do an experiment: > > ---mdir > | > |---Mod1 > | |---mod1.c > | |---Makefile > | > |---Mod2 > |---mod2.c > |---Makefile > > mod1.c define function *void myfunc(void)* and exported by EXPORT_SYMBOL() > and the CRC info is showed in Module.symvers. mod2.c reference *myfunc* and > compiled successfully. BUT when mod2.ko is insmoded, "unknown symbol" is > complained. mod2.ko CAN'T BE INSMOD. Your Mod1 must be live before you load Mod2. When you load your module, the exported symbols would be present in a separate section in the elf file, you can see that using readelf, something like __ksymtab_. When the module is loaded these symbols are noted so that find_symbol can locate these. When you load a module dependent on those symbols, the load_module function would use the find_symbol to get that symbol. CRC would be checked in check_version after the symbol has been found, even then only if you have CONFIG_MODVERSIONS set in your config. > I solve this problem by the method in Documentation/kbuild/modules.txt and > heard this is a bug from kernel 2.6. > > Why this bug is not be fixed? > It's a long way from 2.6 now. can you send something about this "bug"? > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies -- ---P.K.S _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
