I need to call a function in a module I've made. I need to do this from the file readdir.c in the kernel. At the moment, the module is a single file which I've used insmod and rmmod to test. In it is the implementation of my function 'testPath'. I also have a header file which has an empty declaration of my function. The header file I have put in the fs/ directory so it is in the same folder as the readdir.c file.
So I'm lead to understand, in readdir.c, in the kernel, before compiling the kernel, I need to add -
within fs/readdir.c
# include<YourCharDriver.H>
at the top, under the existing include statements. In the same file, within the syscall I'm modifying, I need to put -
struct module *find_module(const char *YourDriverModuleName)
if(module != NULL)
{
testPath();
}
This should test if my module is currently loaded, and if it is it will call my testPath() function.
Obviously I've used file names which actually reflect what my files are called. The error happens when I try to compile the kernel with my changes with a simple 'make'. Is that header file in the right place, and if it is, then what would be causing the 'undefined reference to testPath, why am I getting this when it all makes sense?
Additionally, I've tried declaring the function as extern under the includes in readdir.c, however this yields the same error. Although it seemingly happens a little sooner into the kernel compilation procedure.
Thanks again guys, all this help is appreciated!
2009/11/10 Pulkit Goel <vipulkit.goel@xxxxxxxxx>
Hi,
Mention at the top but after header file in readdir.c:::
..Heder file <>
extern returntype YourDriverFunctionName(arg list);
all other code..On Tue, Nov 10, 2009 at 4:41 PM, Sam Carter <sam.w.carter@xxxxxxxxx> wrote:
Hi again Pulkit, may I ask you where exactly the kernel code section of your reply belongs? I've put the extern part into readdir.c, but I still get an error that it can't find the line inside the if statement you mentioned. Help is appreciated, thanks :)
2009/11/9 Pulkit Goel <vipulkit.goel@xxxxxxxxx>Hi,
Add In Kernel Code::
# include<YourCharDriver.H>
OR
extern YourDriverFunctionName();
:::::from this Driver Function declaration Comes in Kernel Code
Add In Driver Code::
EXPORT_SYMBOL_GPL(YourDriverFunctionName);
Calling Method in ""fs/readdir.c"" ::
struct module *find_module(const char *YourDriverModuleName)
if(module != NULL)
{
YourDriverFunctionName();
}
Regards:
Pulkit Goel
mail:vipulkit.goel@xxxxxxxxx
On Mon, Nov 9, 2009 at 3:35 PM, Sam Carter <sam.w.carter@xxxxxxxxx> wrote:When I try to compile the kernel with my changes to readdir.c, my function in the driver is undefined and it therefore won't compile. This also happens after I've compiled my driver against the kernel tree with the EXPORT_SYMBOL in place.
Any more thoughts on this?2009/11/9 Zhu Yanhai <zhu.yanhai@xxxxxxxxx>EXPORT_SYMBOL_GPL(your func);
Then this function can be called outside.
For the second question, does this one work?
/* Search for module by name: must hold module_mutex. */
struct module *find_module(const char *name)
It's in kernel/module.c and has been exported.
Regards,
Zhu Yanhai
2009/11/8 Sam Carter <sam.w.carter@xxxxxxxxx>:
> Hi all,
>
> I have a char driver/module which compiles and loads into the linux kernel
> just fine. In this driver are some functions which I would like to access
> from the kernel file 'fs/readdir.c'. Additionally, how can I test if a
> driver is loaded?
>
> I need something like the following.
>
> if(myDriver is loaded){
>
> myDriver.functionCall();
> }
>
> All examples I've found on internet searches are doing it from userspace
> applications.
>
> Thanks for any help
>
>
