Insmod gives unsresolved symbol

Insmod gives unsresolved symbol

[Amit Kulkarni]

Hi 

I am trying to write a device driver which calls
certain functions/variables from the kernel 
(e.g. ipv4_explicit_null from
/usr/src/linux/net/mpls/mpls_init.c )

But when I try to insert the module using insmod it
gives me an error saying unresolved symbol
ipv4_explicit_null

thinking the kernel did not export the said symbol  I
added EXPORT_SYMBOL(ipv4_explicit_null) in the file
mpls_init.c 
Now I can see the symbol in System.map
but my problem still persists. 

Am I exporting symbols properly or is there anything
else that needs to be done .

please advise 
thanks in anticipation,
amit

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Re: Insmod gives unsresolved symbol

[Tommy Reynolds]

[-- Attachment #1: Type: text/plain, Size: 1714 bytes --]

It was a dark and stormy night.  Suddenly "Amit Kulkarni" <amitncsu@yahoo.com> wrote:

> Hi 
> 
> I am trying to write a device driver which calls
> certain functions/variables from the kernel 
> (e.g. ipv4_explicit_null from
> /usr/src/linux/net/mpls/mpls_init.c )
> 
> But when I try to insert the module using insmod it
> gives me an error saying unresolved symbol
> ipv4_explicit_null
> 
> thinking the kernel did not export the said symbol  I
> added EXPORT_SYMBOL(ipv4_explicit_null) in the file
> mpls_init.c 
> Now I can see the symbol in System.map
> but my problem still persists. 
> 
> Am I exporting symbols properly or is there anything
> else that needs to be done .

I assume that you're trying to build a module outside the regular kernel build
system.  You can do this if you are carefull.

Look carefully at the symbol in the System.map file.  Is it EXACTLY the
"ipv4_explicit_null" symbol? Are the extra characters after the "...null" part
of the name?  Any extra characters mean that you've got module versioning turned
on in your kernel, so exported symbols have their name mangled somewhat as C++
would do (this is to implement some protection since modules from one kernel
version probably won't work with another kernel version).  The easiest solution
to this is to recompile your kernel with module versioning turned off.

---------------------------------------------+-----------------------------
Tommy Reynolds                               | mailto: <reynolds@redhat.com>
Red Hat, Inc., Embedded Development Services | Phone:  +1.256.704.9286
307 Wynn Drive NW, Huntsville, AL 35805 USA  | FAX:    +1.256.837.3839
Senior Software Developer                    | Mobile: +1.919.641.2923

[-- Attachment #2: Type: application/pgp-signature, Size: 197 bytes --]

Re: Insmod gives unsresolved symbol

[Amit Kulkarni]

In system.map there are no other charachters except
ipv4_explicit_null the line is 
c03c4900 B ipv4_explicit_null
same is true for all other symbols I added.

I am not sure what B indicates




--- Tommy Reynolds <reynolds@redhat.com> wrote:
> It was a dark and stormy night.  Suddenly "Amit
> Kulkarni" <amitncsu@yahoo.com> wrote:
> 
> > Hi 
> > 
> > I am trying to write a device driver which calls
> > certain functions/variables from the kernel 
> > (e.g. ipv4_explicit_null from
> > /usr/src/linux/net/mpls/mpls_init.c )
> > 
> > But when I try to insert the module using insmod
> it
> > gives me an error saying unresolved symbol
> > ipv4_explicit_null
> > 
> > thinking the kernel did not export the said symbol
>  I
> > added EXPORT_SYMBOL(ipv4_explicit_null) in the
> file
> > mpls_init.c 
> > Now I can see the symbol in System.map
> > but my problem still persists. 
> > 
> > Am I exporting symbols properly or is there
> anything
> > else that needs to be done .
> 
> I assume that you're trying to build a module
> outside the regular kernel build
> system.  You can do this if you are carefull.
> 
> Look carefully at the symbol in the System.map file.
>  Is it EXACTLY the
> "ipv4_explicit_null" symbol? Are the extra
> characters after the "...null" part
> of the name?  Any extra characters mean that you've
> got module versioning turned
> on in your kernel, so exported symbols have their
> name mangled somewhat as C++
> would do (this is to implement some protection since
> modules from one kernel
> version probably won't work with another kernel
> version).  The easiest solution
> to this is to recompile your kernel with module
> versioning turned off.
> 
>
---------------------------------------------+-----------------------------
> Tommy Reynolds                               |
> mailto: <reynolds@redhat.com>
> Red Hat, Inc., Embedded Development Services |
> Phone:  +1.256.704.9286
> 307 Wynn Drive NW, Huntsville, AL 35805 USA  | FAX: 
>   +1.256.837.3839
> Senior Software Developer                    |
> Mobile: +1.919.641.2923
> 

> ATTACHMENT part 2 application/pgp-signature 



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Re: Insmod gives unsresolved symbol

[Amit Kulkarni]

these functions are defined in /net/mpls.h as extern
variables. 
I don't think there is a mpls_init.h
I have included mpls.h and hence it compiles w/o error
but only at the time of linking  it gives this error



--- Tyler BIRD <BIRDTY@uvsc.edu> wrote:
> Well you still much include the header file for the
> link
> whatever it might be.  #include
> <include/mpls_init.h>
> for example.  Only some functions such as printk
> don't need such headers.
> 
> Tyler
> 
> 
> >>> Amit Kulkarni <amitncsu@yahoo.com> 11/06/01
> 01:17AM >>>
> Hi 
> 
> I am trying to write a device driver which calls
> certain functions/variables from the kernel 
> (e.g. ipv4_explicit_null from
> /usr/src/linux/net/mpls/mpls_init.c )
> 
> But when I try to insert the module using insmod it
> gives me an error saying unresolved symbol
> ipv4_explicit_null
> 
> thinking the kernel did not export the said symbol 
> I
> added EXPORT_SYMBOL(ipv4_explicit_null) in the file
> mpls_init.c 
> Now I can see the symbol in System.map
> but my problem still persists. 
> 
> Am I exporting symbols properly or is there anything
> else that needs to be done .
> 
> please advise 
> thanks in anticipation,
> amit
> 
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