Re: [PATCH bpf-next v2 00/28] Introduce eBPF support for HID devices

Hi Benjamin,

On 04/03/2022 19:28, Benjamin Tissoires wrote:

Hi,

This is a followup of my v1 at [0].

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 tried to address as many comments as I could and here is the short log
of changes:

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

I posted a couple of comments to the series, but other than that for the whole series you can use:

Reviewed-by: Tero Kristo <redacted>

Tested-by: Tero Kristo <redacted>

I did test this with my USI-BPF program + userspace code, they work with few minor updates compared to previous version.

-Tero

[0] https://lore.kernel.org/linux-input/20220224110828.2168231-1-benjamin.tissoires@redhat.com/T/#t (local)


Benjamin Tissoires (28):
   bpf: add new is_sys_admin_prog_type() helper
   bpf: introduce hid program type
   HID: hook up with bpf
   libbpf: add HID program type and API
   selftests/bpf: add tests for the HID-bpf initial implementation
   samples/bpf: add new hid_mouse example
   bpf/hid: add a new attach type to change the report descriptor
   HID: allow to change the report descriptor from an eBPF program
   libbpf: add new attach type BPF_HID_RDESC_FIXUP
   selftests/bpf: add report descriptor fixup tests
   samples/bpf: add a report descriptor fixup
   bpf/hid: add hid_{get|set}_data helpers
   HID: bpf: implement hid_bpf_get|set_data
   selftests/bpf: add tests for hid_{get|set}_data helpers
   bpf/hid: add new BPF type to trigger commands from userspace
   libbpf: add new attach type BPF_HID_USER_EVENT
   selftests/bpf: add test for user call of HID bpf programs
   selftests/bpf: hid: rely on uhid event to know if a test device is
     ready
   bpf/hid: add bpf_hid_raw_request helper function
   HID: add implementation of bpf_hid_raw_request
   selftests/bpf: add tests for bpf_hid_hw_request
   bpf/verifier: prevent non GPL programs to be loaded against HID
   HID: bpf: compute only the required buffer size for the device
   HID: bpf: only call hid_bpf_raw_event() if a ctx is available
   bpf/hid: Add a flag to add the program at the beginning of the list
   libbpf: add handling for BPF_F_INSERT_HEAD in HID programs
   selftests/bpf: Add a test for BPF_F_INSERT_HEAD
   samples/bpf: fix bpf_program__attach_hid() api change

  drivers/hid/Makefile                         |   1 +
  drivers/hid/hid-bpf.c                        | 361 +++++++++
  drivers/hid/hid-core.c                       |  34 +-
  include/linux/bpf-hid.h                      | 129 +++
  include/linux/bpf_types.h                    |   4 +
  include/linux/hid.h                          |  25 +
  include/uapi/linux/bpf.h                     |  59 ++
  include/uapi/linux/bpf_hid.h                 |  50 ++
  kernel/bpf/Makefile                          |   3 +
  kernel/bpf/hid.c                             | 652 +++++++++++++++
  kernel/bpf/syscall.c                         |  26 +-
  kernel/bpf/verifier.c                        |   7 +
  samples/bpf/.gitignore                       |   1 +
  samples/bpf/Makefile                         |   4 +
  samples/bpf/hid_mouse_kern.c                 |  91 +++
  samples/bpf/hid_mouse_user.c                 | 129 +++
  tools/include/uapi/linux/bpf.h               |  59 ++
  tools/lib/bpf/libbpf.c                       |  22 +-
  tools/lib/bpf/libbpf.h                       |   2 +
  tools/lib/bpf/libbpf.map                     |   1 +
  tools/testing/selftests/bpf/prog_tests/hid.c | 788 +++++++++++++++++++
  tools/testing/selftests/bpf/progs/hid.c      | 216 +++++
  22 files changed, 2649 insertions(+), 15 deletions(-)
  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