Error message not relevant

Mulyadi Santosa mulyadi.santosa at
Thu Nov 21 01:45:46 EST 2013

On Wed, Nov 20, 2013 at 11:43 PM, Nav Kamal <navkamal90 at> wrote:
> Am learning to write LKMs and wrote this program :
> #include<linux/init.h>
> #include<linux/module.h>
> static int module_entry(void){
>         printk(KERN_ALERT "Hello World !!\n");
>         return 0;
> }
> static void exit_module(void){
>         printk(KERN_ALERT "Bye World .... \n");
> }
> module_init(module_entry);
> module_exit(exit_module);
> In this program if I change return value of function module_entry from 0 to
> something negative, the module fails to load. The error message is :
> "insmod: ERROR: could not insert module test.ko: Operation not permitted"
> Failing to load module with negative return value is understandable but I
> can't understand why it says "Operation not permitted". Its not about user
> permissions, its about return value. Can somebody please guide me about this
> ?

AFAIK, insmod/modprobe translate any errors during module load as "not
permitted". This doesn't mean you can not read the .ko files, it just
means you can't load it.


Mulyadi Santosa
Freelance Linux trainer and consultant


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