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

[Tero Kristo <tero.kristo@linux.intel.com>]

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 <tero.kristo@linux.intel.com>

Tested-by: Tero Kristo <tero.kristo@linux.intel.com>

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
>
>
> 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
>