Re: Nonotify 0.3.2 (A simple dnotify replacement)

[Pascal Schmidt <der.eremit@email.de>]

On Sun, 22 Aug 2004, nf wrote:

> But i didn't want to bother people with asking to assign me a
> syscall-number before even knowing if they like my idea. And changing it
> to use a syscall lateron would be no problem at all from the concept of
> nonotify.

Right. It's just something to consider if you aim for inclusion in
the mainline tree later.

> Also - as a kernel newbie - i didn't find any good documentation how to
> add my own syscall into the kernel. I just wanted to get nonotify
> working as an 'optional patch', without changing tons of files.

Adding a syscall should roughly work like this:

- write your sys_foo() function
- add your syscall number to include/asm-i386/unistd.h, don't forget
  to change the "#define NR_syscalls" accordingly
- add ".long sys_foo" to sys_call_table in arch/i386/kernel/entry.S,
  in the right place (i.e. syscall 290 would need to be element 290
  in the list)
- arrange for the object file with sys_foo in it to be linked into
  the kernel

You're right, your going to have to touch a couple of files for
this approach.

> But you could help me if you have a look at my ioctl function. I'm using
> a structure which contains a char* pointer and four timespec fields. Do
> you know if this causes problems with 32/64bit compatibility.

I don't think the timespecs will be a problem. However, the char
pointer will have different sizes and alignment requirements on
32bit and 64bit system. I'm no expert in how that can be handled
in the compat layer, though.

-- 
Ciao,
Pascal