Re: RFD: x32 ABI system call numbers

[H. Peter Anvin]

On 09/01/2011 05:49 PM, Pedro Alves wrote:
> > >       struct iovec
> > >       {
> > >           void __user *iov_base;    /* BSD uses caddr_t (1003.1g requires
> > > void *) */
> > >           __kernel_size_t iov_len; /* Must be size_t (1003.1g) */
> > >       } __attribute__((x32_abi_64));
> > >
> > >       typedef long time_t __attribute__((x32_abi_64));
> > >
> > > The x32_abi_64 attribute converts pointers and longs back to 64-bit and
> > > adjusts the alignment accordingly.  If we tag all userspace visible
> > > structures with this attribute, we can use the 64-bit ABI without changes.
>
> I would expect no new gcc extension to be needed for that -- there's the
> mode attribute (you can read DI as 64-bit):
>
>   typedef void * __kernel_ptr64 __attribute ((mode(DI)));
>
>   struct iovec
>   {
>     __kernel_ptr64 iov_base;
>     ...
>   };

Does that work for *writing*, too?  That might be a very useful little 
escape hatch for some particularly tight corners.

	-hpa
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