[Partly a RFC/formal submission: there are still FIXMEs in the code] [Also using bpf-next as the base tree for HID changes as there will be conflicting changes otherwise, so I'm personaly fine for the HID commits to go through bpf-next]
IMO, patches 1-3 and 9-14 are ready to go, rest is still pending review. For reference, the use cases I have in mind: --- Basically, I need to be able to defer a HID-BPF program for the following reasons (from the aforementioned patch): 1. defer an event: Sometimes we receive an out of proximity event, but the device can not be trusted enough, and we need to ensure that we won't receive another one in the following n milliseconds. So we need to wait those n milliseconds, and eventually re-inject that event in the stack. 2. inject new events in reaction to one given event: We might want to transform one given event into several. This is the case for macro keys where a single key press is supposed to send a sequence of key presses. But this could also be used to patch a faulty behavior, if a device forgets to send a release event. 3. communicate with the device in reaction to one event: We might want to communicate back to the device after a given event. For example a device might send us an event saying that it came back from sleeping state and needs to be re-initialized. Currently we can achieve that by keeping a userspace program around, raise a bpf event, and let that userspace program inject the events and commands. However, we are just keeping that program alive as a daemon for just scheduling commands. There is no logic in it, so it doesn't really justify an actual userspace wakeup. So a kernel workqueue seems simpler to handle. The other part I'm not sure is whether we can say that BPF maps of type queue/stack can be used in sleepable context. I don't see any warning when running the test programs, but that's probably not a guarantee I'm doing the things properly :) Cheers, Benjamin To: Alexei Starovoitov <[email protected]> To: Daniel Borkmann <[email protected]> To: John Fastabend <[email protected]> To: Andrii Nakryiko <[email protected]> To: Martin KaFai Lau <[email protected]> To: Eduard Zingerman <[email protected]> To: Song Liu <[email protected]> To: Yonghong Song <[email protected]> To: KP Singh <[email protected]> To: Stanislav Fomichev <[email protected]> To: Hao Luo <[email protected]> To: Jiri Olsa <[email protected]> To: Jiri Kosina <[email protected]> To: Benjamin Tissoires <[email protected]> To: Jonathan Corbet <[email protected]> To: Shuah Khan <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Signed-off-by: Benjamin Tissoires <[email protected]> --- Changes in v3: - fixed the crash from v2 - changed the API to have only BPF_F_TIMER_SLEEPABLE for bpf_timer_start() - split the new kfuncs/verifier patch into several sub-patches, for easier reviews - Link to v2: https://lore.kernel.org/r/[email protected] Changes in v2: - make use of bpf_timer (and dropped the custom HID handling) - implemented bpf_timer_set_sleepable_cb as a kfunc - still not implemented global subprogs - no sleepable bpf_timer selftests yet - Link to v1: https://lore.kernel.org/r/[email protected] --- Benjamin Tissoires (16): bpf/verifier: allow more maps in sleepable bpf programs bpf/verifier: introduce in_sleepable() helper bpf/verifier: add is_async_callback_calling_insn() helper bpf/helpers: introduce sleepable bpf_timers bpf/verifier: add bpf_timer as a kfunc capable type bpf/helpers: introduce bpf_timer_set_sleepable_cb() kfunc bpf/helpers: mark the callback of bpf_timer_set_sleepable_cb() as sleepable bpf/verifier: do_misc_fixups for is_bpf_timer_set_sleepable_cb_kfunc HID: bpf/dispatch: regroup kfuncs definitions HID: bpf: export hid_hw_output_report as a BPF kfunc selftests/hid: Add test for hid_bpf_hw_output_report HID: bpf: allow to inject HID event from BPF selftests/hid: add tests for hid_bpf_input_report HID: bpf: allow to use bpf_timer_set_sleepable_cb() in tracing callbacks. selftests/hid: add test for bpf_timer selftests/hid: add KASAN to the VM tests Documentation/hid/hid-bpf.rst | 2 +- drivers/hid/bpf/hid_bpf_dispatch.c | 232 ++++++++++++++------- drivers/hid/hid-core.c | 2 + include/linux/bpf_verifier.h | 2 + include/linux/hid_bpf.h | 3 + include/uapi/linux/bpf.h | 4 + kernel/bpf/helpers.c | 140 +++++++++++-- kernel/bpf/verifier.c | 114 ++++++++-- tools/testing/selftests/hid/config.common | 1 + tools/testing/selftests/hid/hid_bpf.c | 195 ++++++++++++++++- tools/testing/selftests/hid/progs/hid.c | 198 ++++++++++++++++++ .../testing/selftests/hid/progs/hid_bpf_helpers.h | 8 + 12 files changed, 795 insertions(+), 106 deletions(-) --- base-commit: 5c331823b3fc52ffd27524bf5b7e0d137114f470 change-id: 20240205-hid-bpf-sleepable-c01260fd91c4 Best regards, -- Benjamin Tissoires <[email protected]>
