kernel stack memory

[Adil Mujeeb]

Hi,

On Thu, Sep 13, 2012 at 1:59 PM, Arun KS <getarunks at gmail.com> wrote:
> Hello Shubham,
>
> On Thu, Sep 13, 2012 at 12:15 PM, shubham sharma <shubham20006 at gmail.com>
> wrote:
>>
>> Hi,
>>
>> As far as i know, the size of stack allocated in the kernel space is
>> 8Kb for each process. But in case i use more than 8Kb of memory from
>> the stack then what will happen? I think that in that case the system
>> would crash because i am accessing an illegal memory area. I wrote
>> kernel module in which i defined an integer array whose size was 8000.
>> But still it did not crash my system. Why?
>>
>> The module i wrote was as follows:
>>
>> #include <linux/kernel.h>
>> #include <linux/module.h>
>>
>> int __init init_my_module(void)
>> {
>>         int arr[8000];
>>         printk("%s:%d\tmodule initilized\n", __func__, __LINE__);
>>         arr[1] = 1;
>>         arr[4000] = 1;
>>         arr[7999] = 1;
>
> Instead do a memset.
> memset(arr, 0, 8192);
>
> If you do this the current calling process thread_info will be set to zero.
> This should cause a crash.

I tried and this is also not causing any crash.

Thanks,
Adil
>
> Thanks,
> Arun
>
>
>>
>>         printk("%s:%d\tarr[1]:%d, arr[4000]:%d, arr[7999]:%d\n", __func__,
>> __LINE__, arr[1], arr[4000], arr[7999]);
>>         return 0;
>> }
>>
>> void __exit cleanup_my_module(void)
>> {
>>         printk("exiting\n");
>>         return;
>> }
>>
>> module_init(init_my_module);
>> module_exit(cleanup_my_module);
>>
>> MODULE_LICENSE("GPL");
>>
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>
>
>
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