更改/ proc

Question

我实际上在Linux 2.6.32上工作lkm，我不理解一件事。我试图用我的函数更改/ proc / version的原始read_proc和write_proc。因此，我可以使用my函数的值更改read_proc和write_proc的原始值。我可以看到它，因为read_proc和write_proc的值变为NULL以对我的函数进行加法，但这没有效果......而且我不明白为什么。我没有到达以查找版本是否受到保护（我尝试使用chmod更改文件的值），或者为什么即使在更改了值之后，我也无法写入/ proc /版本为echo XXXX > /proc/version。我很感激你的帮助。

我尝试更改read_proc和write_proc的值的代码：

static void Proc_init()
{
    int find = 0;

pde = create_proc_entry("test", 0444, NULL); //that permit to create new file in /proc, only to get some useful values
ptdir = pde->parent; //affect to ptdir the value of the pointer on /proc

 if(strcmp(ptdir->name, "/proc")!=0)
 {
     Erreur=1;
 }
    else
     {

        root = ptdir;
        remove_proc_entry("test", NULL);

        ptr_subdir=root->subdir;

        while(find==0)
        {
            printk("%s \n", ptr_subdir->name);
            if(strcmp("version", ptr_subdir->name)==0)
                find=1;
            else
                 ptr_subdir=ptr_subdir->next;
        }

        //Save original write et read proc
        old_read_proc=ptr_subdir->read_proc;
    old_write_proc=ptr_subdir->write_proc;

    // Before I have null values for prt_subdir->read_proc and ptr_subdir->write_proc
     ptr_subdir->read_proc=&new_read_proc_t;
     ptr_subdir->write_proc=&new_write_proc_t;

    // after that, values of prt_subdir->read_proc and ptr_subdir- >write_proc are egual to values of &new_write_proc_t and &new_read_proc_t
     }
}

static int new_read_proc_t (char *page, char **start, off_t off,int count, int *eof, void *data)
{
    int len;
   /* For example - when content of our_buf is "hello" - when user executes   command "cat /proc/test_proc"
   he will see content of our_buf(in our example "hello" */
   len = snprintf(page, count, "%s", our_buf);
   return len;
 }

   static int new_write_proc_t(struct file *file, const char __user *buf,unsigned long count, void *data)
   {
    /* If count is bigger than 255, data which user wants to write is too   big to fit in our_buf. We don't want
    any buffer overflows, so we read only 255 bytes */  
    if(count > 255)
       count = 255;
    /* Here we read from buf to our_buf */
    copy_from_user(our_buf, buf, count);
    /* we write NULL to end the string */
    our_buf[count] = '\0';
    return count;

  }