Re: [PATCH 0/5] add initial io_uring_cmd support for sockets

Breno Leitao
2023-04-12T13:53:30Z

On Tue, Apr 11, 2023 at 09:28:29AM -0600, Jens Axboe wrote:
> On 4/11/23 9:24?AM, Willem de Bruijn wrote:
> > Jens Axboe wrote:
> >> On 4/11/23 9:00?AM, Willem de Bruijn wrote:
> >> But that doesn't work, because sock->ops->ioctl() assumes the arg is
> >> memory in userspace. Or do you mean change all of the sock->ops->ioctl()
> >> to pass in on-stack memory (or similar) and have it work with a kernel
> >> address?
> >
> > That was what I suggested indeed.
> >
> > It's about as much code change as this patch series. But it avoids
> > the code duplication.
>
> Breno, want to tackle that as a prep patch first? Should make the
> functional changes afterwards much more straightforward, and will allow
> support for anything really.

Absolutely. I just want to make sure that I got the proper approach that
we agreed here.

Let me explain what I understood taking TCP as an example:

1) Rename tcp_ioctl() to something as _tcp_ioctl() where the 'arg'
argument is now just a kernel memory (located in the stack frame from the
callee).

2) Recreate "tcp_ioctl()" that will basically allocate a 'arg' in the
stack and call _tcp_ioctl() passing that 'arg' argument. At the bottom of
this (tcp_ioctl() function) function, call `put_user(in_kernel_arg, userspace_arg)

3) Repeat it for the 20 protocols that implement ioctl:

ag "struct proto .* = {" -A 20 net/ | grep \.ioctl
net/dccp/ipv6.c .ioctl = dccp_ioctl,
net/dccp/ipv4.c .ioctl = dccp_ioctl,
net/ieee802154/socket.c .ioctl = dgram_ioctl,
net/ipv4/udplite.c .ioctl = udp_ioctl,
net/ipv4/raw.c .ioctl = raw_ioctl,
net/ipv4/udp.c .ioctl = udp_ioctl,
net/ipv4/tcp_ipv4.c .ioctl = tcp_ioctl,
net/ipv6/raw.c .ioctl = rawv6_ioctl,
net/ipv6/tcp_ipv6.c .ioctl = tcp_ioctl,
net/ipv6/udp.c .ioctl = udp_ioctl,
net/ipv6/udplite.c .ioctl = udp_ioctl,
net/l2tp/l2tp_ip6.c .ioctl = l2tp_ioctl,
net/l2tp/l2tp_ip.c .ioctl = l2tp_ioctl,
net/phonet/datagram.: .ioctl = pn_ioctl,
net/phonet/pep.c .ioctl = pep_ioctl,
net/rds/af_rds.c .ioctl = rds_ioctl,
net/sctp/socket.c .ioctl = sctp_ioctl,
net/sctp/socket.c .ioctl = sctp_ioctl,
net/xdp/xsk.c .ioctl = sock_no_ioctl,
net/mptcp/protocol.c .ioctl = mptcp_ioctl,

Am I missing something?

Thanks!