Re: [HELP] How to get address of module

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Mon, 8 Aug 2005, Hiroki Kaminaga wrote:

>
> Hi!
>
> I'm looking for *nice* way to get address of loaded module in 2.6.
> I'd like to know the address from driver.
>
> In 2.4, I wrote something like this:
>
> * * *
>
> (in kernel src)
> --- kernel/module.c
> +++ kernel/module.c
>
> struct module *module_list = &kernel_module;
>
> + struct module *get_module_queue(void)
> + {
> +         return module_list;
> + }
> +
> +
>
> ... and in driver, I wrote:
>
>        mod = get_module_queue();
>        while (mod->next) {
>                if (strcmp(mod->name, name) == 0)
>                        return (unsigned long)(mod + 1);
>                mod = mod->next;
>        }
>        return 0;
>
> * * *
>
> I am now using 2.6 kernel. The choice I can think of is
>
> 1) make linux-2.6/kernel/module.c:find_module(const char *name)
>   global func, not static, and use this func.
>
> 2) use linux-2.6/kernel/module.c:module_kallsyms_lookup_name(const char *name)
>   and somehow get return value from module_get_kallsym(...)
>
> choice 1) doesn't sound nice since it changes static func -> global
> func, but cost of getting module address is low. On the other hand,
> choice 2) will not modify kernel src, which sounds nice, but costs more,
> and I'm not sure this method works.
>
> Any advice?!
>
>
> HK.


What do you want the address of in your driver? Do you want the
address of its various entry points (hint, the stuff you put
into the "struct file_operations"), or its startup code, module_init(),
exit code, module_exit(), etc.

These are can all be obtained using conventional 'C' syntax. You
don't need to search some list somehere. You driver isn't just
put somewhere en-masse. The code is in the .text segment, relocated
to exist in allocated memory. The data sections are also relocated
to different sections of allocated memory.

You get the address of a function by referencing its name:

static int ioctl(struct inode *inp, struct file *fp, size_t cmd, unsigned long
arg)
{
     unsigned long val;
     switch(cmd)
    {
     case GET_ADDRESS_OF_IOCTL:
         val = (unsigned long) ioctl;
         if(put_user(val, (unsigned long *)arg))
             return -EFAULT
         break;
     case ETC:
    }

Your driver probably has many functions, therefore it has many
addresses. It's not just a single "module" somewhere.



Cheers,
Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
Warning : 98.36% of all statistics are fiction.
.
I apologize for the following. I tried to kill it with the above dot :

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