Re: [v10][PATCH 8/9] Define clone_with_pids() syscall

[Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>]

On Tuesday 03 November 2009, Sukadev Bhattiprolu wrote:
> 
> Oren Laadan [orenl-RdfvBDnrOixBDgjK7y7TUQ@public.gmane.org] wrote:
> | 
> | > +   /*
> | > +    * TODO: If size of clone_args is not what the kernel expects, it
> | > +    *       could be that kernel is newer and has an extended structure.
> | > +    *       When that happens, this check needs to be smarter (and we
> | > +    *       need an additional copy_from_user()). For now, assume exact
> | > +    *       match.
> | > +    */
> | > +   if (kcs.clone_args_size != sizeof(kcs))
> | > +           return -EINVAL;
> | 
> | I wonder if this is a reason to move the clone_args_size outside the
> | structure and pass it as a regular argument ?  This will rid the
> | (futuristic) additional copy-from-user (in case it causes a concern
> | for clone performance ?)
> 
> Your idea makes sense to me. 
> 
> Roland, Peter Arnd: do you have any concerns with removing clone_args_size
> from the structure and making it a parameter ?

As I mentioned before when it came up the first time, I think that the
clone_args_size argument is completely bogus and unnecessary in the
presence of the flags word, but I agree that if we have it, it should
better be a separate argument.

	Arnd <><