From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Jiri Kosina <jikos@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
Dave Marchevsky <davemarchevsky@fb.com>,
Joe Stringer <joe@cilium.io>, Jonathan Corbet <corbet@lwn.net>,
Tero Kristo <tero.kristo@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
"open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
Subject: Re: [PATCH bpf-next v3 06/17] HID: allow to change the report descriptor from an eBPF program
Date: Mon, 28 Mar 2022 14:35:34 -0700 [thread overview]
Message-ID: <CAEf4BzZA7Wmg=N42ib_r9Jm8THXuGGR3CPgTqMyw9n2=gd_+Kg@mail.gmail.com> (raw)
In-Reply-To: <CAO-hwJKPxKCzxCKGpH85j5VG3bQk+7axDYpxYoy-12yL7AQj2w@mail.gmail.com>
On Sun, Mar 27, 2022 at 11:57 PM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> On Fri, Mar 25, 2022 at 6:00 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Wed, Mar 23, 2022 at 9:08 AM Benjamin Tissoires
> > <benjamin.tissoires@redhat.com> wrote:
> > >
> > > Hi Alexei,
> > >
> > > On Tue, Mar 22, 2022 at 11:51 PM Alexei Starovoitov
> > > <alexei.starovoitov@gmail.com> wrote:
> > > >
> > > > On Fri, Mar 18, 2022 at 9:16 AM Benjamin Tissoires
> > > > <benjamin.tissoires@redhat.com> wrote:
> > > > >
> > > > > +u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size)
> > > > > +{
> > > > > + int ret;
> > > > > + struct hid_bpf_ctx_kern ctx = {
> > > > > + .type = HID_BPF_RDESC_FIXUP,
> > > > > + .hdev = hdev,
> > > > > + .size = *size,
> > > > > + };
> > > > > +
> > > > > + if (bpf_hid_link_empty(&hdev->bpf, BPF_HID_ATTACH_RDESC_FIXUP))
> > > > > + goto ignore_bpf;
> > > > > +
> > > > > + ctx.data = kmemdup(rdesc, HID_MAX_DESCRIPTOR_SIZE, GFP_KERNEL);
> > > > > + if (!ctx.data)
> > > > > + goto ignore_bpf;
> > > > > +
> > > > > + ctx.allocated_size = HID_MAX_DESCRIPTOR_SIZE;
> > > > > +
> > > > > + ret = hid_bpf_run_progs(hdev, &ctx);
> > > > > + if (ret)
> > > > > + goto ignore_bpf;
> > > > > +
> > > > > + if (ctx.size > ctx.allocated_size)
> > > > > + goto ignore_bpf;
> > > > > +
> > > > > + *size = ctx.size;
> > > > > +
> > > > > + if (*size) {
> > > > > + rdesc = krealloc(ctx.data, *size, GFP_KERNEL);
> > > > > + } else {
> > > > > + rdesc = NULL;
> > > > > + kfree(ctx.data);
> > > > > + }
> > > > > +
> > > > > + return rdesc;
> > > > > +
> > > > > + ignore_bpf:
> > > > > + kfree(ctx.data);
> > > > > + return kmemdup(rdesc, *size, GFP_KERNEL);
> > > > > +}
> > > > > +
> > > > > int __init hid_bpf_module_init(void)
> > > > > {
> > > > > struct bpf_hid_hooks hooks = {
> > > > > .hdev_from_fd = hid_bpf_fd_to_hdev,
> > > > > .pre_link_attach = hid_bpf_pre_link_attach,
> > > > > + .post_link_attach = hid_bpf_post_link_attach,
> > > > > .array_detach = hid_bpf_array_detach,
> > > > > };
> > > > >
> > > > > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> > > > > index 937fab7eb9c6..3182c39db006 100644
> > > > > --- a/drivers/hid/hid-core.c
> > > > > +++ b/drivers/hid/hid-core.c
> > > > > @@ -1213,7 +1213,8 @@ int hid_open_report(struct hid_device *device)
> > > > > return -ENODEV;
> > > > > size = device->dev_rsize;
> > > > >
> > > > > - buf = kmemdup(start, size, GFP_KERNEL);
> > > > > + /* hid_bpf_report_fixup() ensures we work on a copy of rdesc */
> > > > > + buf = hid_bpf_report_fixup(device, start, &size);
> > > >
> > > > Looking at this patch and the majority of other patches...
> > > > the code is doing a lot of work to connect HID side with bpf.
> > > > At the same time the evolution of the patch series suggests
> > > > that these hook points are not quite stable. More hooks and
> > > > helpers are being added.
> > > > It tells us that it's way too early to introduce a stable
> > > > interface between HID and bpf.
> > >
> > > I understand that you might be under the impression that the interface
> > > is changing a lot, but this is mostly due to my poor knowledge of all
> > > the arcanes of eBPF.
> > > The overall way HID-BPF works is to work on a single array, and we
> > > should pretty much be sorted out. There are a couple of helpers to be
> > > able to communicate with the device, but the API has been stable in
> > > the kernel for those for quite some time now.
> > >
> > > The variations in the hooks is mostly because I don't know what is the
> > > best representation we can use in eBPF for those, and the review
> > > process is changing that.
> >
> > I think such a big feature as this one, especially that most BPF folks
> > are (probably) not familiar with the HID subsystem in the kernel,
> > would benefit from a bit of live discussion during BPF office hours.
> > Do you think you can give a short overview of what you are trying to
> > achieve with some background context on HID specifics at one of the
> > next BPF office hours? We have a meeting scheduled every week on
> > Thursday, 9am Pacific time. But people need to put their topic onto
> > the agenda, otherwise the meeting is cancelled. See [0] for
> > spreadsheet and links to Zoom meeting, agenda, etc.
>
> This sounds like a good idea. I just added my topic on the agenda and
> will prepare some slides.
>
Great! Unfortunately I personally have a conflict this week and won't
be able to attend, so I'll have to catch up somehow through word of
mouth :( Next week's BPF office hours would be best, but I don't want
to delay discussions just because of me.
> Cheers,
> Benjamin
>
> >
> > [0] https://docs.google.com/spreadsheets/d/1LfrDXZ9-fdhvPEp_LHkxAMYyxxpwBXjywWa0AejEveU
> >
> > [...]
> >
>
next prev parent reply other threads:[~2022-03-28 22:11 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-18 16:15 [PATCH bpf-next v3 00/17] Introduce eBPF support for HID devices Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 01/17] bpf: add new is_sys_admin_prog_type() helper Benjamin Tissoires
2022-03-18 18:07 ` Song Liu
2022-03-18 16:15 ` [PATCH bpf-next v3 02/17] bpf: introduce hid program type Benjamin Tissoires
2022-03-18 20:48 ` Song Liu
2022-03-21 16:07 ` Benjamin Tissoires
2022-03-21 21:51 ` Song Liu
2022-03-22 11:06 ` Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 03/17] bpf/verifier: prevent non GPL programs to be loaded against HID Benjamin Tissoires
2022-03-18 20:51 ` Song Liu
2022-03-18 16:15 ` [PATCH bpf-next v3 04/17] libbpf: add HID program type and API Benjamin Tissoires
2022-03-18 20:53 ` Song Liu
2022-03-18 16:15 ` [PATCH bpf-next v3 05/17] HID: hook up with bpf Benjamin Tissoires
2022-03-18 21:02 ` Song Liu
2022-03-18 21:04 ` Song Liu
2022-03-18 16:15 ` [PATCH bpf-next v3 06/17] HID: allow to change the report descriptor from an eBPF program Benjamin Tissoires
2022-03-18 21:10 ` Song Liu
2022-03-21 16:20 ` Benjamin Tissoires
2022-03-21 22:03 ` Song Liu
2022-03-22 22:51 ` Alexei Starovoitov
2022-03-23 16:08 ` Benjamin Tissoires
2022-03-25 17:00 ` Andrii Nakryiko
2022-03-28 6:56 ` Benjamin Tissoires
2022-03-28 21:35 ` Andrii Nakryiko [this message]
2022-03-29 13:53 ` Benjamin Tissoires
2022-04-01 13:21 ` Benjamin Tissoires
2022-03-30 21:27 ` Alexei Starovoitov
2022-03-18 16:15 ` [PATCH bpf-next v3 07/17] selftests/bpf: add tests for the HID-bpf initial implementation Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 08/17] selftests/bpf: add report descriptor fixup tests Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 09/17] selftests/bpf: Add a test for BPF_F_INSERT_HEAD Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 10/17] selftests/bpf: add test for user call of HID bpf programs Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 11/17] samples/bpf: add new hid_mouse example Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 12/17] bpf/hid: add more HID helpers Benjamin Tissoires
2022-03-18 21:19 ` Song Liu
2022-03-21 16:24 ` Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 13/17] HID: bpf: implement hid_bpf_get|set_bits Benjamin Tissoires
2022-03-18 21:20 ` Song Liu
2022-03-18 16:15 ` [PATCH bpf-next v3 14/17] HID: add implementation of bpf_hid_raw_request Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 15/17] selftests/bpf: add tests for hid_{get|set}_bits helpers Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 16/17] selftests/bpf: add tests for bpf_hid_hw_request Benjamin Tissoires
2022-03-18 16:15 ` [PATCH bpf-next v3 17/17] Documentation: add HID-BPF docs Benjamin Tissoires
2022-03-18 18:05 ` Song Liu
2022-03-29 13:04 ` [PATCH bpf-next v3 00/17] Introduce eBPF support for HID devices Tero Kristo
2022-04-01 9:37 ` Benjamin Tissoires
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