Re: cannot insmod owlsm.o ?

sarnoldat_private

On Mon, Apr 07, 2003 at 10:06:18AM -0400, Yale Wu wrote:
> I'v compiled kernel 2.4.20 with LSM patched and selected LSM support.
> After reboot with new kernel, I compiled owlsm.c "gcc -D__KERNEL__ -DMODULE -c owlsm.c".
> It outputs owlsm.o successfully. But when I use "insmod owlsm.o", it tells me 
> owlsm.o: unresolved symbol unregister_security
> owlsm.o: unresolved symbol mod_reg_security
> owlsm.o: unresolved symbol mod_unreg_security
> owlsm.o: unresolved symbol register_security

Chances are very good that if you run:
$ grep register_security /proc/ksyms
c016ccc0 register_security_R7df42fa6
c016cd70 unregister_security_R1f060df4

You'll see some "modversions" symbol mangling appended to the name of
the symbols your kernel actually exports. modversions was an unfortunate
attempt to provide a way binary modules wouldn't need to be recompiled
as frequently. Sadly, it is completely insufficient for this purpose
and winds up just causing problems.

The easy way to solve this problem is to re-run the kernel configure
scripts (make config, make menuconfig, make xconfig, whatever) and
select the olwsm module for building as a module. Then, the Makefiles
will properly handle the modversions and include paths and the like.
Just run "make modules; sudo make modules_install" after turning on
owlsm support, and the owlsm module should be placed in /lib/modules/
somewhere.

The hard way to solve the problem is to look at the Makefiles and
re-create how they call GCC, so you can call GCC by hand the same way
they do.

And, if you would like to understand how modversions works, I suggest
reading chapter 11 of the book Linux Device Drivers, 2nd edition. It is
available for free on http://www.ora.com/, thanks to the good people at
O'Reilly. (Buy the printed version. It is well worth the cost. :)

I hope this helps.

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