About exporting symbols from an external module

[Henrique Rodrigues]

Hi Le,

You can do that by exporting a function pointer from the kvm code that is
only called if it is not null. Then, when you load your module, you set
that exported function pointer (I'm assuming that you want to call your
module's function from the kvm code... ). Here is a post on how to do that:

http://stackoverflow.com/questions/11463184/how-to-use-exported-symbols-in-the-linux-kernel
http://stackoverflow.com/questions/1196944/can-i-replace-a-linux-kernel-function-with-a-module

Best,
--
Henrique Rodrigues
http://www.dcc.ufmg.br/~hsr


On Mon, Jan 13, 2014 at 2:47 AM, Le Tan <tamlokveer at gmail.com> wrote:

> Hello! I am writing a device driver module. I define some functions in the
> module, for example print_record(). I am doing something in the kvm, so I
> want to call print_record() in the file of kvm module, for example, I may
> call print_record() in file /arch/x86/kvm/x86.c to put something into my
> device driver module.
> Now comes the question.
> 1. Where should I put the codes of my device driver module? It's the first
> time I write the device driver.
> 2. After compiling my module, I encounter an error when I compile the kvm
> module.
>      ERROR: "print_record" [arch/x86/kvm/kvm.ko] undefined!
>     I use EXPORT_SYMBOL(print_record) in my module file. I use "extern" to
> declare print_record() and then call print_record()  in file x86.c.
>     To solve this problem, I have tried to copy the Module.symvers from my
> module folder to /arch/x86/kvm/. But it doesn't work. I have also tried to
> add *KBUILD_EXTRA_SYMBOLS *to the Makefile of kvm. It doesn't work either.
>     I cat /proc/kallsyms and find that the type of symbol "print_record"
> is "t" ( local text). What should I do? How to call functions defined in my
> own module from kvm? Maybe there is something wrong in Makefiles?
>
> Any suggestion is appreciated!
> Thanks!
>
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