linux-kernel - Re: get rid of the address_space override in setsockopt

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Date:   Wed, 22 Jul 2020 10:07:24 +0200
From:   'Christoph Hellwig' <hch@....de>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Christoph Hellwig' <hch@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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Subject: Re: get rid of the address_space override in setsockopt

On Tue, Jul 21, 2020 at 10:26:58AM +0000, David Laight wrote:
> From: Christoph Hellwig
> > Sent: 20 July 2020 13:47
> > 
> > setsockopt is the last place in architecture-independ code that still
> > uses set_fs to force the uaccess routines to operate on kernel pointers.
> > 
> > This series adds a new sockptr_t type that can contained either a kernel
> > or user pointer, and which has accessors that do the right thing, and
> > then uses it for setsockopt, starting by refactoring some low-level
> > helpers and moving them over to it before finally doing the main
> > setsockopt method.
> 
> Another 'gotcha' ...
> 
> On an least some architectures (possibly only m68k) IIRC all structures
> are actually passed by reference.
> (This used to be true for sparc - but it may have changed in the
> last 30 years.)

Tough luck for ABIs wit suboptimal calling conventions.  At least we can
do the right thing for those that do not have the problem.