Do you know the bug of EXPORT_SYMBOL()

Greg KH greg at
Fri Jul 24 13:10:18 EDT 2015

On Fri, Jul 24, 2015 at 01:49:42PM +0800, Navy 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.

Use 'modprobe' after "properly" installing the kernel modules to the
correct location, and then all will be fine.

greg k-h

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