I see, the linker was trying to link your function (which is in a
module and invisible to make)
try function pointer:
in fs/readdir.c
define a global func pointer: void (*mytestPath)();
Then
struct module *find_module(const char *YourDriverModuleName)
if(module != NULL && mytestPath != NULL)
{
mytestPath();
}
And then in your module:
extern void (*mytestPath)();
module_init()
{
mytestPath=testPath;
}
2009/11/11 Sam Carter <sam.w.carter@xxxxxxxxx>:
> Sorry to ask again folks, but this is proving to be a nightmare.
>
> 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..
>>
>>
>>
>> Regards:
>> Pulkit Goel
>> mail:vipulkit.goel@xxxxxxxxx
>>
>>
>>
>> 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
>>>>>> >
>>>>>> >
>>>>>
>>>>
>>>
>>
>
>
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