EXPORT_SYMBOL doesn't work

DISCUSSION Jason Li 3 participants 9 messages Mar 18, 2002 – Mar 20, 2002

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Jason Li

author

2002-03-18 06:25 UTC #0 lore raw

Hi,

Have been puzzled by the problem for a couple of hours now, can some experts here please help me out. Thanks very much for any info you can provide here. Please remember to reply back to me also as I am not on the list yet.

I am trying to use module to do kernel development. Currently I have some code to be loaded as a module. In the code though I need some hooks to the existing kernel.

Basically I am working on the bridge code. In the bridge there is a hook created by myslef as:

int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);

The hook will be connected by my module on module_init:

	fdbIoSwitchHook = myFdbFunc;

But the symbol fdbIoSwitchHook can't bve resolved by the insmod for my module.

I saw there is no fdbIoSwitchHook in the /proc/ksyms. My kernel is versioned it seems.

When I compile the export_symbol file, it did complained:
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall -Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer -fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686 -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
br_ioctl.c:26: warning: parameter names (without types) in function declaration
br_ioctl.c:26: warning: data definition has no type or storage class br_ioctl.c: In function `br_ioctl_device':
br_ioctl.c:206: warning: implicit declaration of function `fdbShow'

Can someone please shed some light on this please? I don't understand why the symbol is not exported and what I need to do to finished my task ahead.

Best regards,
Jason

Keith Owens

2002-03-18 06:35 UTC #1 lore raw

Quoted 11 lines · Jason Li

int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'

#include <linux/module.h>

Also add br_ioctl.o to export-objs in Makefile.

Jason Li

author

2002-03-18 19:12 UTC #2 lore raw

Quoted 17 lines · Keith Owens

Quoted 11 lines · Jason Li
int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
#include <linux/module.h>

Quoted 1 line

Also add br_ioctl.o to export-objs in Makefile.

Thanks alot. It works.

Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:

#define MODULE
#include <linux/modversions.h>
#include <linux/kernel.h>

When I do nm on the module, fdbIoSwitchHook is still a pure name without the version info. Can you please tell me how to enable the versioning for the symbol fdbIoSwitchHook?

Appreciate your help!

-Jason

Keith Owens

2002-03-18 19:46 UTC #3 lore raw

Quoted 6 lines · Jason Li

Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:
#define MODULE
#include <linux/modversions.h>
#include <linux/kernel.h>

Never include modverversions.h yourself, the kernel build process automatically includes it when required. See also
http://www.tux.org/lkml/#s8-8.

Tom Rini

2002-03-18 19:20 UTC #4 lore raw

In reply to Keith Owens

Quoted 18 lines · Jason Li

Quoted 17 lines · Keith Owens
Quoted 11 lines · Jason Li
int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
#include <linux/module.h>

Quoted 6 lines

Quoted 1 line
Also add br_ioctl.o to export-objs in Makefile.
Thanks alot. It works.
Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:

Backup your .config, run 'distclean' or 'mrproper' and try again.

Signature · 2 lines

Tom Rini (TR1265)
http://gate.crashing.org/~trini/

Jason Li

author

2002-03-18 19:32 UTC #5 lore raw

In reply to Keith Owens

Quoted 24 lines · Tom Rini

Quoted 22 lines · Jason Li
Quoted 17 lines · Keith Owens
Quoted 11 lines · Jason Li
int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
#include <linux/module.h>
Quoted 1 line
Also add br_ioctl.o to export-objs in Makefile.
Thanks alot. It works.

Quoted 8 lines

Quoted 2 lines
Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:
Backup your .config, run 'distclean' or 'mrproper' and try again.
--
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

I followed Keith's instruction. It seems now the problem is that the inlucde/linux/module/netsym.ver (i put the EXPORT_SYMBOL in netsym.c now) doesn't have the vesion for the fdbIoSwatichHook symbol.

I wonder if someone tell me how to gernerate the file with latest info, I may be able to fix this.

In the meantime I did a distclean, and will see.

Thanks,
Jason

Jason Li

author

2002-03-18 19:43 UTC #6 lore raw

In reply to Keith Owens

Quoted 24 lines · Tom Rini

Quoted 22 lines · Jason Li
Quoted 17 lines · Keith Owens
Quoted 11 lines · Jason Li
int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
#include <linux/module.h>
Quoted 1 line
Also add br_ioctl.o to export-objs in Makefile.
Thanks alot. It works.

Quoted 8 lines

Quoted 2 lines
Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:
Backup your .config, run 'distclean' or 'mrproper' and try again.
--
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

Just did a distclean. Now the inluce/linux/modules/netsym.ver has the fdbIoSwitchHook version info.

Recompiled the module. Did a nm on the module, and saw the version info for the symbol. But when I dod insmod, it still complained about unresolved symbol fdbIoSwitchHook.

It seems now the version is different between the kernel and the module. Should I wait for the bzImage compilation to complete and install the new kernel?

Thanks a lot,
Jason

Tom Rini

2002-03-19 00:23 UTC #7 lore raw

In reply to Keith Owens

Quoted 37 lines · Jason Li

Quoted 24 lines · Tom Rini
Quoted 22 lines · Jason Li
Quoted 17 lines · Keith Owens
Quoted 11 lines · Jason Li
int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
#include <linux/module.h>
Quoted 1 line
Also add br_ioctl.o to export-objs in Makefile.
Thanks alot. It works.
Quoted 8 lines
Quoted 2 lines
Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:
Backup your .config, run 'distclean' or 'mrproper' and try again.
--
Tom Rini (TR1265)
http://gate.crashing.org/~trini/
Just did a distclean. Now the inluce/linux/modules/netsym.ver has the fdbIoSwitchHook version info.

Quoted 7 lines

Recompiled the module. Did a nm on the module, and saw the version info for the symbol. But when I dod insmod, it still complained about unresolved symbol fdbIoSwitchHook.
It seems now the version is different between the kernel and the module. Should I wait for the bzImage compilation to complete and install the new kernel?

There are annoying depenancies with modversions. Basically the safe way is that if you change any export (add/remove), you should do a 'distclean', recompile everything and switch to that.

Signature · 2 lines

Tom Rini (TR1265)
http://gate.crashing.org/~trini/

Jason Li

author

2002-03-20 06:20 UTC #8 lore raw

In reply to Keith Owens

Quoted 47 lines · Tom Rini

Quoted 37 lines · Jason Li
Quoted 24 lines · Tom Rini
Quoted 22 lines · Jason Li
Quoted 17 lines · Keith Owens
Quoted 11 lines · Jason Li
int (*fdbIoSwitchHook)(
unsigned long arg0, unsigned long arg1, unsigned long arg2)=NULL;
EXPORT_SYMBOL(fdbIoSwitchHook);
gcc -D__KERNEL__ -I/home/jli/cvs2/exos/linux/include -Wall
(quoted diff) +0 -3
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o br_ioctl.o br_ioctl.c
br_ioctl.c:26: warning: type defaults to int' in declaration of EXPORT_SYMBOL'
#include <linux/module.h>
Quoted 1 line
Also add br_ioctl.o to export-objs in Makefile.
Thanks alot. It works.
Quoted 8 lines
Quoted 2 lines
Now another problem with versioning. It seems even after I have the following in my module c file the symbol generated is not versioned:
Backup your .config, run 'distclean' or 'mrproper' and try again.
--
Tom Rini (TR1265)
http://gate.crashing.org/~trini/
Just did a distclean. Now the inluce/linux/modules/netsym.ver has the fdbIoSwitchHook version info.
Quoted 7 lines
Recompiled the module. Did a nm on the module, and saw the version info for the symbol. But when I dod insmod, it still complained about unresolved symbol fdbIoSwitchHook.
It seems now the version is different between the kernel and the module. Should I wait for the bzImage compilation to complete and install the new kernel?

Quoted 7 lines

There are annoying depenancies with modversions. Basically the safe way is that if you change any export (add/remove), you should do a 'distclean', recompile everything and switch to that.
--
Tom Rini (TR1265)
http://gate.crashing.org/~trini/

In case I haven't concluded this thread yet, all the info worked for me.

After the distclean everything is in place and it works nicely now.

Will try more when I get a little bit more time.

Huge thanks to Tom and Keith for their input.

-Jason