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Message-ID: <0a30942b-e6c9-72fb-d012-4b8a6a16ae42@linux.intel.com>
Date: Tue, 29 Mar 2022 16:04:28 +0300
From: Tero Kristo <tero.kristo@...ux.intel.com>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>,
Greg KH <gregkh@...uxfoundation.org>,
Jiri Kosina <jikos@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>, Shuah Khan <shuah@...nel.org>,
Dave Marchevsky <davemarchevsky@...com>,
Joe Stringer <joe@...ium.io>, Jonathan Corbet <corbet@....net>
Cc: linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
netdev@...r.kernel.org, bpf@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 00/17] Introduce eBPF support for HID devices
Hi Benjamin,
I tested this iteration of the set, and I faced couple of problems with it.
1) There were some conflicts as I could not figure out the correct
kernel commit on which to apply the series on. I applied this on top of
last weeks bpf-next (see below) with some local merge fixes.
commit 2af7e566a8616c278e1d7287ce86cd3900bed943 (bpf-next/master,
bpf-next/for-next)
Author: Saeed Mahameed <saeedm@...dia.com>
Date: Tue Mar 22 10:22:24 2022 -0700
net/mlx5e: Fix build warning, detected write beyond size of field
2) hid_is_valid_access() causes some trouble and it rejects pretty much
every BPF program which tries to use ctx->retval. This appears to be
because prog->expected_attach_type is not populated, I had to apply
below local tweak to overcome this problem:
diff --git a/kernel/bpf/hid.c b/kernel/bpf/hid.c
index 30a62e8e0f0a..bf64411e6e9b 100644
--- a/kernel/bpf/hid.c
+++ b/kernel/bpf/hid.c
@@ -180,8 +180,7 @@ static bool hid_is_valid_access(int off, int size,
case offsetof(struct hid_bpf_ctx, retval):
if (size != size_default)
return false;
- return (prog->expected_attach_type == BPF_HID_USER_EVENT ||
- prog->expected_attach_type == BPF_HID_DRIVER_EVENT);
+ return true;
default:
if (size != size_default)
return false;
Proper fix would probably be to actually populate the
expected_attach_type, but I could not figure out quickly where this
should be done, or whether it is actually done on some other base commit.
With those, for the whole series:
Tested-by: Tero Kristo <tero.kristo@...ux.intel.com>
On 18/03/2022 18:15, Benjamin Tissoires wrote:
> Hi,
>
> This is a followup of my v1 at [0] and v2 at [1].
>
> The short summary of the previous cover letter and discussions is that
> HID could benefit from BPF for the following use cases:
>
> - simple fixup of report descriptor:
> benefits are faster development time and testing, with the produced
> bpf program being shipped in the kernel directly (the shipping part
> is *not* addressed here).
>
> - Universal Stylus Interface:
> allows a user-space program to define its own kernel interface
>
> - Surface Dial:
> somehow similar to the previous one except that userspace can decide
> to change the shape of the exported device
>
> - firewall:
> still partly missing there, there is not yet interception of hidraw
> calls, but it's coming in a followup series, I promise
>
> - tracing:
> well, tracing.
>
>
> I think I addressed the comments from the previous version, but there are
> a few things I'd like to note here:
>
> - I did not take the various rev-by and tested-by (thanks a lot for those)
> because the uapi changed significantly in v3, so I am not very confident
> in taking those rev-by blindly
>
> - I mentioned in my discussion with Song that I'll put a summary of the uapi
> in the cover letter, but I ended up adding a (long) file in the Documentation
> directory. So please maybe start by reading 17/17 to have an overview of
> what I want to achieve
>
> - I added in the libbpf and bpf the new type BPF_HID_DRIVER_EVENT, even though
> I don't have a user of it right now in the kernel. I wanted to have them in
> the docs, but we might not want to have them ready here.
> In terms of code, it just means that we can attach such programs types
> but that they will never get triggered.
>
> Anyway, I have been mulling on this for the past 2 weeks, and I think that
> maybe sharing this now is better than me just starring at the code over and
> over.
>
>
> Short summary of changes:
>
> v3:
> ===
>
> - squashed back together most of the libbpf and bpf changes into bigger
> commits that give a better overview of the whole interactions
>
> - reworked the user API to not expose .data as a directly accessible field
> from the context, but instead forces everyone to use hid_bpf_get_data (or
> get/set_bits)
>
> - added BPF_HID_DRIVER_EVENT (see note above)
>
> - addressed the various nitpicks from v2
>
> - added a big Documentation file (and so adding now the doc maintainers to the
> long list of recipients)
>
> v2:
> ===
>
> - split the series by subsystem (bpf, HID, libbpf, selftests and
> samples)
>
> - Added an extra patch at the beginning to not require CAP_NET_ADMIN for
> BPF_PROG_TYPE_LIRC_MODE2 (please shout if this is wrong)
>
> - made the bpf context attached to HID program of dynamic size:
> * the first 1 kB will be able to be addressed directly
> * the rest can be retrieved through bpf_hid_{set|get}_data
> (note that I am definitivey not happy with that API, because there
> is part of it in bits and other in bytes. ouch)
>
> - added an extra patch to prevent non GPL HID bpf programs to be loaded
> of type BPF_PROG_TYPE_HID
> * same here, not really happy but I don't know where to put that check
> in verifier.c
>
> - added a new flag BPF_F_INSERT_HEAD for BPF_LINK_CREATE syscall when in
> used with HID program types.
> * this flag is used for tracing, to be able to load a program before
> any others that might already have been inserted and that might
> change the data stream.
>
> Cheers,
> Benjamin
>
>
>
> [0] https://lore.kernel.org/linux-input/20220224110828.2168231-1-benjamin.tissoires@redhat.com/T/#t
> [1] https://lore.kernel.org/linux-input/20220304172852.274126-1-benjamin.tissoires@redhat.com/T/#t
>
>
> Benjamin Tissoires (17):
> bpf: add new is_sys_admin_prog_type() helper
> bpf: introduce hid program type
> bpf/verifier: prevent non GPL programs to be loaded against HID
> libbpf: add HID program type and API
> HID: hook up with bpf
> HID: allow to change the report descriptor from an eBPF program
> selftests/bpf: add tests for the HID-bpf initial implementation
> selftests/bpf: add report descriptor fixup tests
> selftests/bpf: Add a test for BPF_F_INSERT_HEAD
> selftests/bpf: add test for user call of HID bpf programs
> samples/bpf: add new hid_mouse example
> bpf/hid: add more HID helpers
> HID: bpf: implement hid_bpf_get|set_bits
> HID: add implementation of bpf_hid_raw_request
> selftests/bpf: add tests for hid_{get|set}_bits helpers
> selftests/bpf: add tests for bpf_hid_hw_request
> Documentation: add HID-BPF docs
>
> Documentation/hid/hid-bpf.rst | 444 +++++++++++
> Documentation/hid/index.rst | 1 +
> drivers/hid/Makefile | 1 +
> drivers/hid/hid-bpf.c | 328 ++++++++
> drivers/hid/hid-core.c | 34 +-
> include/linux/bpf-hid.h | 127 +++
> include/linux/bpf_types.h | 4 +
> include/linux/hid.h | 36 +-
> include/uapi/linux/bpf.h | 67 ++
> include/uapi/linux/bpf_hid.h | 71 ++
> include/uapi/linux/hid.h | 10 +
> kernel/bpf/Makefile | 3 +
> kernel/bpf/btf.c | 1 +
> kernel/bpf/hid.c | 728 +++++++++++++++++
> kernel/bpf/syscall.c | 27 +-
> kernel/bpf/verifier.c | 7 +
> samples/bpf/.gitignore | 1 +
> samples/bpf/Makefile | 4 +
> samples/bpf/hid_mouse_kern.c | 117 +++
> samples/bpf/hid_mouse_user.c | 129 +++
> tools/include/uapi/linux/bpf.h | 67 ++
> tools/lib/bpf/libbpf.c | 23 +-
> tools/lib/bpf/libbpf.h | 2 +
> tools/lib/bpf/libbpf.map | 1 +
> tools/testing/selftests/bpf/config | 3 +
> tools/testing/selftests/bpf/prog_tests/hid.c | 788 +++++++++++++++++++
> tools/testing/selftests/bpf/progs/hid.c | 205 +++++
> 27 files changed, 3204 insertions(+), 25 deletions(-)
> create mode 100644 Documentation/hid/hid-bpf.rst
> create mode 100644 drivers/hid/hid-bpf.c
> create mode 100644 include/linux/bpf-hid.h
> create mode 100644 include/uapi/linux/bpf_hid.h
> create mode 100644 kernel/bpf/hid.c
> create mode 100644 samples/bpf/hid_mouse_kern.c
> create mode 100644 samples/bpf/hid_mouse_user.c
> create mode 100644 tools/testing/selftests/bpf/prog_tests/hid.c
> create mode 100644 tools/testing/selftests/bpf/progs/hid.c
>
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