Re: [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable

[Al Viro]

On Sun, Aug 29, 2021 at 08:44:04PM +0200, Thomas Gleixner wrote:
> On Sat, Aug 28 2021 at 22:51, Al Viro wrote:
> > @@ -345,7 +346,7 @@ static inline int xsave_to_user_sigframe(struct xregs_state __user *buf)
> >  	 */
> >  	err = __clear_user(&buf->header, sizeof(buf->header));
> >  	if (unlikely(err))
> > -		return -EFAULT;
> > +		return -X86_TRAP_PF;
> 
> This clear_user can be lifted into copy_fpstate_to_sigframe(). Something
> like the below.

Hmm...  This mixing of -X86_TRAP_... with -E... looks like it's asking for
trouble in general.  Might be worth making e.g. fpu__restore_sig() (and
its callers) return bool, seeing that we only check for 0/non-zero in
there.