[PATCH HID v2 00/16] HID: convert HID-BPF into using bpf_struct_ops

[Benjamin Tissoires <bentiss@kernel.org>]

The purpose of this series is to rethink how HID-BPF is invoked.
Currently it implies a jmp table, a prog fd bpf_map, a preloaded tracing
bpf program and a lot of manual work for handling the bpf program
lifetime and addition/removal.

OTOH, bpf_struct_ops take care of most of the bpf handling leaving us
with a simple list of ops pointers, and we can directly call the
struct_ops program from the kernel as a regular function.

The net gain right now is in term of code simplicity and lines of code
removal (though is an API breakage), but udev-hid-bpf is able to handle
such breakages.

In the near future, we will be able to extend the HID-BPF struct_ops
with entrypoints for hid_hw_raw_request() and hid_hw_output_report(),
allowing for covering all of the initial use cases:
- firewalling a HID device
- fixing all of the HID device interactions (not just device events as
  it is right now).

The matching user-space loader (udev-hid-bpf) MR is at
https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/86

I'll put it out of draft once this is merged.

Cheers,
Benjamin

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
---
Changes in v2:
- drop HID_BPF_FLAGS enum and use BPF_F_BEFORE instead
- fix .init_members to not open code member->offset
- allow struct hid_device to be writeable from HID-BPF for its name,
  uniq and phys
- Link to v1: https://lore.kernel.org/r/20240528-hid_bpf_struct_ops-v1-0-8c6663df27d8@kernel.org

---
Benjamin Tissoires (16):
      HID: rename struct hid_bpf_ops into hid_ops
      HID: bpf: add hid_get/put_device() helpers
      HID: bpf: implement HID-BPF through bpf_struct_ops
      selftests/hid: convert the hid_bpf selftests with struct_ops
      HID: samples: convert the 2 HID-BPF samples into struct_ops
      HID: bpf: add defines for HID-BPF SEC in in-tree bpf fixes
      HID: bpf: convert in-tree fixes into struct_ops
      HID: bpf: remove tracing HID-BPF capability
      selftests/hid: add subprog call test
      Documentation: HID: amend HID-BPF for struct_ops
      Documentation: HID: add a small blurb on udev-hid-bpf
      HID: bpf: Artist24: remove unused variable
      HID: bpf: error on warnings when compiling bpf objects
      bpf: allow bpf helpers to be used into HID-BPF struct_ops
      HID: bpf: rework hid_bpf_ops_btf_struct_access
      HID: bpf: make part of struct hid_device writable

 Documentation/hid/hid-bpf.rst                      | 173 ++++---
 drivers/hid/bpf/Makefile                           |   2 +-
 drivers/hid/bpf/entrypoints/Makefile               |  93 ----
 drivers/hid/bpf/entrypoints/README                 |   4 -
 drivers/hid/bpf/entrypoints/entrypoints.bpf.c      |  25 -
 drivers/hid/bpf/entrypoints/entrypoints.lskel.h    | 248 ---------
 drivers/hid/bpf/hid_bpf_dispatch.c                 | 266 +++-------
 drivers/hid/bpf/hid_bpf_dispatch.h                 |  12 +-
 drivers/hid/bpf/hid_bpf_jmp_table.c                | 565 ---------------------
 drivers/hid/bpf/hid_bpf_struct_ops.c               | 298 +++++++++++
 drivers/hid/bpf/progs/FR-TEC__Raptor-Mach-2.bpf.c  |   9 +-
 drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c    |   6 +-
 drivers/hid/bpf/progs/Huion__Kamvas-Pro-19.bpf.c   |   9 +-
 .../hid/bpf/progs/IOGEAR__Kaliber-MMOmentum.bpf.c  |   6 +-
 drivers/hid/bpf/progs/Makefile                     |   2 +-
 .../hid/bpf/progs/Microsoft__XBox-Elite-2.bpf.c    |   6 +-
 drivers/hid/bpf/progs/Wacom__ArtPen.bpf.c          |   6 +-
 drivers/hid/bpf/progs/XPPen__Artist24.bpf.c        |  10 +-
 drivers/hid/bpf/progs/XPPen__ArtistPro16Gen2.bpf.c |  24 +-
 drivers/hid/bpf/progs/hid_bpf.h                    |   5 +
 drivers/hid/hid-core.c                             |   6 +-
 include/linux/hid_bpf.h                            | 125 ++---
 samples/hid/Makefile                               |   5 +-
 samples/hid/hid_bpf_attach.bpf.c                   |  18 -
 samples/hid/hid_bpf_attach.h                       |  14 -
 samples/hid/hid_mouse.bpf.c                        |  26 +-
 samples/hid/hid_mouse.c                            |  39 +-
 samples/hid/hid_surface_dial.bpf.c                 |  10 +-
 samples/hid/hid_surface_dial.c                     |  53 +-
 tools/testing/selftests/hid/hid_bpf.c              | 100 +++-
 tools/testing/selftests/hid/progs/hid.c            | 100 +++-
 .../testing/selftests/hid/progs/hid_bpf_helpers.h  |  19 +-
 32 files changed, 805 insertions(+), 1479 deletions(-)
---
base-commit: 70ec81c2e2b4005465ad0d042e90b36087c36104
change-id: 20240513-hid_bpf_struct_ops-e3212a224555

Best regards,
-- 
Benjamin Tissoires <bentiss@kernel.org>