Unimplemented system call

[Umair Khan]

On Tue, Mar 5, 2019 at 7:26 PM <valdis.kletnieks at vt.edu> wrote:
>
> On Tue, 05 Mar 2019 19:08:20 -0500, Umair Khan said:
>
> > I was just roaming around the linux source code when I stumbled upon
> > this line - https://github.com/torvalds/linux/blob/master/include/linux/syscalls.h#L1200
> >
> > May I know what is the use of this system call?
>
> /*
>  * Not a real system call, but a placeholder for syscalls which are
>  * not implemented -- see kernel/sys_ni.c
>  */
> asmlinkage long sys_ni_syscall(void);
>
> Well, did you go look at kernel/sys_ni.c like it told you to?  Because if you
> bothered reading the first 2 dozen lines of that file, you would find:

Yes I looked at this file actually.

> /*
>  * Non-implemented system calls get redirected here.
>  */
> asmlinkage long sys_ni_syscall(void)
> {
>         return -ENOSYS;
> }
>
> Are there any remining questions?

I was just wondering why are these system calls not implemented?

-Umair