Exporting kernel symbols

[Ravi <kravi26@yahoo.com>]

Hello,

 While working with the 2.4.10 kernel, I wanted to export a function
that I added. I found that EXPORT_SYMBOL(..) alone does not help if
CONFIG_MODVERSIONS is set. I also didn't  find any document that
explains how to make a kernel symbol available to modules. Below is the
list of steps that I followed  - after some trial and error. Can
someone please verify this?



HOWTO export a kernel symbol to modules
---------------------------------------
Steps to make a symbol 'my_function' (defined in my_obj.c) available to
kernel modules:
 
1. Include the following two files in the source file (my_obj.c) :

 linux/module.h  and  linux/modsetver.h
 
2. Add the following line to the source file:
 
EXPORT_SYMBOL(my_function);
 
 
3. Add the object filename to the 'export-objs' variable in the current
directory's Makefile. If the variable does not exist, add it:
 
export_objs := my_obj.o
 
  3a. If the changes you are making are enabled/disabled by a config
option, you can conditionally modify export-objs : 

#ifdef CONFIG_MY_OPTION
export-objs += my_obj.o
#endif
 
 
IMPORTANT:
Make sure that your file name does not clash with any of the existing
files in include/linux/modules. For example, if a file 'my_obj.ver'
already exists in include/linux/modules, you have to rename your file
(or move only the EXPORT_SYMBOL and related parts to a different file).

---------------------------


-Thanks,
 Ravi.

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