Thanks John. Later I understood the code. But I would like to ask that is this code portable ? becoz when you are using (struct module *)0L then it is going to become a NULL pointer and it is not necessary NULL will have a value 0 (zero). So would'nt it be better if this code is written as : ((unsigned long)&((struct module *)0L)->persist_start - (unsigned long)(struct module *)0L) I think this is portable! -neeraj => 0L refers to the number 0 as a Long integer. => => Basically, what is happening is, the kernel is acting as if the module => struct is located at address 0. Obviously, this structure isn't there, but => the effect is that the address returned is the size of the data contained => in the structure before the persist_start member. => => John => => On Thu, 18 Apr 2002, Neeraj wrote: => => > Hello friends, => > => > I have just started reading the kernel code and hence a kernel newbie. Right now => > I am reading the code of Linux kernel version 2.4.3. The file module.c conatins => > a function sys_init_module. I am not able to the understand the following LOC. => > => > <snip> => > => > if (mod_user_size < (unsigned long)&((struct module *)0L)->persist_start => > => > </snip> => > => > What does 0L refers to ? Can somebody please explain it to me. => > => > Thanks => > neeraj => > => > => > => > -- => > Kernelnewbies: Help each other learn about the Linux kernel. => > Archive: http://mail.nl.linux.org/kernelnewbies/ => > FAQ: http://kernelnewbies.org/faq/ => > => => -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
