how to use the memory allocated in kernel?

[夏业添]

Hi everyone,

there are some functions can alloc memory in kernel, but it seems that I
cannot use it directly. Here is my code:

static int mytest_vm(){

        struct vm_struct *v_start;

        v_start=alloc_vm_area(PAGE_SIZE,NULL); //the kernel api has
changed, I don't understand why there is a second parameter
        if(v_start==NULL){
                printk("cannot alloc page\n");
                return -1;
        }

        sprintf((char *)v_start->addr,"this is a test.\n");
        printk("after sprintk:%s",(char *)v_start->addr);

        free_vm_area(v_start);

        return 0;
}
module_init(mytest_vm);

but it just got a kernel Oops. Can anyone explain this to me? Thanks very
much!
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