question about module and undeinfed symbols.

question about module and undeinfed symbols.

[Sylvain]

Hello,

I have a problem of undefined symbol, that prevents me from loading
the module I wrote.

The function that is "undifined", is actually defined within the
kernel code, and I wanted it to be exported with "export_symbol"
macro. After re-compiling, the variable is actually presents in
/proc/kallsyms.  (but with type == 't'  -> section text, but not
global according to proc file..)

if I tried to compile a module using this variable, i got a warning
"undefined symbol", and for this reason, the module refuses to be
loaded with "insmod".

What I dont understand is the following:
The fonction printk, is also undifened and exported with the same
macro "export_symbol". but compilation doesnt complain about it!!

Am I missing a step somewhere?!
Thanks for any help,

sylvain

Re: question about module and undeinfed symbols.

[Jan Engelhardt]

>The fonction printk, is also undifened and exported with the same
>macro "export_symbol". but compilation doesnt complain about it!!

#include <linux/kernel.h>

>Am I missing a step somewhere?!


Jan Engelhardt
-- 
Gesellschaft für Wissenschaftliche Datenverarbeitung
Am Fassberg, 37077 Göttingen, www.gwdg.de

Re: question about module and undeinfed symbols.

[Sylvain]

Hi Jan,

thanks you for you response, unfortunatly it appears not to work better :/

I think the problem is isolated, I notices that System.map doesnt
contain same information for my function:
there is the line "c010d480 T myFunction"
but no entry: __ksymtab_myFunction nor __kstrtab_myFunction, 

A warning appear during kernel compilation, on the line: 
EXPORT_SYMBOL(myFunction):

warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'
parameter names (without types) in function declaration
data definition has no type of storage classe

seems to me really weird :/

Sylvain


On Sun, 14 Nov 2004 19:48:37 +0100 (MET), Jan Engelhardt
<jengelh@linux01.gwdg.de> wrote:
> 
> >The fonction printk, is also undifened and exported with the same
> >macro "export_symbol". but compilation doesnt complain about it!!
> 
> #include <linux/kernel.h>
> 
> >Am I missing a step somewhere?!
> 
> 
> Jan Engelhardt
> --
> Gesellschaft für Wissenschaftliche Datenverarbeitung
> Am Fassberg, 37077 Göttingen, www.gwdg.de
>

Re: question about module and undeinfed symbols.

[Jan Engelhardt]

>A warning appear during kernel compilation, on the line:
>EXPORT_SYMBOL(myFunction):

That should have been a semicolon (;) not a colon (:).

To access a symbol in the "kernel" (i.e. bzImage) from a module, it needs to be
exported via the already-mentioned EXPORT_SYMBOL(). From kernel to kernel,
there is nothing needed.

>warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'

#include <linux/module.h> to get the EXPORT_SYMBOLs and stuff.

>parameter names (without types) in function declaration
>data definition has no type of storage classe
>
>> #include <linux/kernel.h>

I mean, it's not done with ONE include file. Even for simple modules (like
http://linux01.org:2222/f/oops_ko.tbz2) you already need a handful of includes.

And "small" (~400 lines) modules like my kernel-based tty logger interface
already takes 16 lines o' include.



Jan Engelhardt
-- 
Gesellschaft für Wissenschaftliche Datenverarbeitung
Am Fassberg, 37077 Göttingen, www.gwdg.de