Kernel module symbol versioning?

Kernel module symbol versioning?

[Kendall Bennett]

Hi,

I have been reading the book "Linux Device Drivers, 2nd Edition" and have 
some questions about symbol versioning. In Chapter 11 it mentions that 
you can use the <linux/modversions.h> header file to compile your module 
with symbol versions enabled, so that your module will load on multiple 
kernels and fail if the symbol CRC's do not match. I tested this out on a 
simple test module, but this module fails to load unless I pass the '-f' 
flag to insmod (Red Hat 7.3 and 8.0). 

Is there a way to compile the module so that insmod will only complain if 
there is a version conflict? Or do you always have to use -f in this case 
to force the module to load? If you have to do that, will -f still fail 
to load if the versioned symbols don't match?

Regards,

---
Kendall Bennett
Chief Executive Officer
SciTech Software, Inc.
Phone: (530) 894 8400
http://www.scitechsoft.com

~ SciTech SNAP - The future of device driver technology! ~

Re: Kernel module symbol versioning?

[Bas Mevissen]

Kendall Bennett wrote:

> Hi,
> 
> I have been reading the book "Linux Device Drivers, 2nd Edition" and have 
> some questions about symbol versioning. In Chapter 11 it mentions that 
> you can use the <linux/modversions.h> header file to compile your module 
> with symbol versions enabled, so that your module will load on multiple 
> kernels and fail if the symbol CRC's do not match. I tested this out on a 
> simple test module, but this module fails to load unless I pass the '-f' 
> flag to insmod (Red Hat 7.3 and 8.0). 
> 
> Is there a way to compile the module so that insmod will only complain if 
> there is a version conflict? Or do you always have to use -f in this case 
> to force the module to load? If you have to do that, will -f still fail 
> to load if the versioned symbols don't match?
> 

Isn't the confict cause here (just) that one is compiled with gcc 2.x 
and the other with gcc 3.x?

In other words, retry compiling this module on one system with the two 
different kernels, as you want to compare kernel source level interface 
  differences and not kernel ABI (Application Binairy Interface IIRC) 
differences.

Regards,

Bas.