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

Tero Kristo
2022-03-15T17:07:07Z

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
>