Re: [PATCH 0/3] clone64() and unshare64() system calls

["H. Peter Anvin" <hpa@zytor.com>]

sukadev@us.ibm.com wrote:
> This is a resend of the patch set Cedric had sent earlier. I ported
> the patch set to 2.6.25-rc8-mm1 and tested on x86 and x86_64.
> ---
> 
> We have run out of the 32 bits in clone_flags !
> 
> This patchset introduces 2 new system calls which support 64bit clone-flags.
> 
>      long sys_clone64(unsigned long flags_high, unsigned long flags_low,
> 		unsigned long newsp);
> 
>      long sys_unshare64(unsigned long flags_high, unsigned long flags_low);
> 
> The current version of clone64() does not support CLONE_PARENT_SETTID and 
> CLONE_CHILD_CLEARTID because we would exceed the 6 registers limit of some 
> arches. It's possible to get around this limitation but we might not
> need it as we already have clone()
> 

I really dislike this interface.

If you're going to make it a 64-bit pass it in as a 64-bit number, 
instead of breaking it into two numbers.  Better yet, IMO, would be to 
pass a pointer to a structure like:

struct shared {
	unsigned long nwords;
	unsigned long flags[];
};

... which can be expanded indefinitely.

	-hpa