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[34.150.157.240]) by smtp.gmail.com with ESMTPSA id t17-20020a05622a181100b003e3982a6f2bsm524147qtc.18.2023.04.13.07.24.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Apr 2023 07:24:32 -0700 (PDT) Date: Thu, 13 Apr 2023 10:24:31 -0400 From: Willem de Bruijn To: Breno Leitao , Willem de Bruijn Cc: Jens Axboe , David Ahern , Willem de Bruijn , io-uring@vger.kernel.org, netdev@vger.kernel.org, kuba@kernel.org, asml.silence@gmail.com, leit@fb.com, edumazet@google.com, pabeni@redhat.com, davem@davemloft.net, dccp@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, matthieu.baerts@tessares.net, marcelo.leitner@gmail.com Message-ID: <6438109fe8733_13361929472@willemb.c.googlers.com.notmuch> In-Reply-To: References: <75e3c434-eb8b-66e5-5768-ca0f906979a1@kernel.org> <67831406-8d2f-feff-f56b-d0f002a95d96@kernel.dk> <643573df81e20_11117c2942@willemb.c.googlers.com.notmuch> <036c80e5-4844-5c84-304c-7e553fe17a9b@kernel.dk> <64357608c396d_113ebd294ba@willemb.c.googlers.com.notmuch> <19c69021-dce3-1a4a-00eb-920d1f404cfc@kernel.dk> <64357bb97fb19_114b22294c4@willemb.c.googlers.com.notmuch> <20cb4641-c765-e5ef-41cb-252be7721ce5@kernel.dk> <6436c01979c9b_163b6294b4@willemb.c.googlers.com.notmuch> Subject: Re: [PATCH 0/5] add initial io_uring_cmd support for sockets Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Breno Leitao wrote: > On Wed, Apr 12, 2023 at 10:28:41AM -0400, Willem de Bruijn wrote: > > Breno Leitao wrote: > > > 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? > > > > The suggestion is to convert all to take kernel memory and do the > > put_cmsg in the caller of .ioctl. Rather than create a wrapper for > > each individual instance and add a separate .iouring_cmd for each. > > > > "change all of the sock->ops->ioctl() to pass in on-stack memory > > (or similar) and have it work with a kernel address" > > is it possible to do it for cases where we don't know what is the size > of the buffer? > > For instance the raw_ioctl()/rawv6_ioctl() case. The "arg" argument is > used in different ways (one for input and one for output): > > 1) If cmd == SIOCOUTQ or SIOCINQ, then the return value will be > returned to userspace: > put_user(amount, (int __user *)arg) > > 2) For default cmd, ipmr_ioctl() is called, which reads from the `arg` > parameter: > copy_from_user(&vr, arg, sizeof(vr) > > How to handle these contradictory behaviour ahead of time (at callee > time, where the buffers will be prepared)? > > Thank you! Ah you found a counter-example to the simple pattern of put_user. The answer perhaps depends on how many such counter-examples you encounter in the list you gave. If this is the only one, exceptions in the wrapper are reasonable. Not if there are many. Is the intent for io_uring to support all cases eventually? The current patch series only targeted more common fast path operations. Probably also relevant is whether/how the approach can be extended to [gs]etsockopt, as that was another example given, with the same challenge.