kernel stack memory

[Kshemendra KP]

In user space when you write beyond your address space (if your write
crosses
the page boundary alloacted to you), then process is terminated. In the
kernel
you are still writinng inside the kernel address space. Your write is not
beyond
kernel address space.

Secondly you are corrupting some other data structure. The kernel stack is
part
of task_struct of the running process, a kmalloc or slab allocator might
have
provided this memory (task_-struct).  When you write beyond this if the
write modiefies some crucial data structure that may result in hang or a
crash.




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;
>         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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