From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <edumazet@google.com>
Subject: Re: [PATCH 04/26] net: add a new sockptr_t type
Date: Thu, 23 Jul 2020 09:40:27 -0700
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References: <20200723060908.50081-1-hch@lst.de> <20200723060908.50081-5-hch@lst.de>
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To: Christoph Hellwig <hch@lst.de>
Cc: "David S. Miller" <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" <linux-crypto@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-sctp@vger.kernel.org, linux-hams@vger.kernel.org, linux-bluetooth@vger.kernel.org, bridge@lists.linux-foundation.org, linux-can@vger.kernel.org, dccp@vger.kernel.org, linux-decnet-user@lists.sourceforge.net, linux-wpan@vger.kernel.org, linux-s390@vger.kernel.org, mptcp@lists.01.org, lvs
List-Id: linux-can.vger.kernel.org

On Wed, Jul 22, 2020 at 11:09 PM Christoph Hellwig <hch@lst.de> wrote:
>
> Add a uptr_t type that can hold a pointer to either a user or kernel
> memory region, and simply helpers to copy to and from it.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  include/linux/sockptr.h | 104 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 104 insertions(+)
>  create mode 100644 include/linux/sockptr.h
>
> diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
> new file mode 100644
> index 00000000000000..700856e13ea0c4
> --- /dev/null
> +++ b/include/linux/sockptr.h
> @@ -0,0 +1,104 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2020 Christoph Hellwig.
> + *
> + * Support for "universal" pointers that can point to either kernel or userspace
> + * memory.
> + */
> +#ifndef _LINUX_SOCKPTR_H
> +#define _LINUX_SOCKPTR_H
> +
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +typedef struct {
> +       union {
> +               void            *kernel;
> +               void __user     *user;
> +       };
> +       bool            is_kernel : 1;
> +} sockptr_t;
>

I am not sure why you chose sockptr_t   for something that really seems generic.

Or is it really meant to be exclusive to setsockopt() and/or getsockopt() ?

If the first user of this had been futex code, we would have used
futexptr_t, I guess.