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Message-Id: <20240214-hid-bpf-sleepable-v2-0-5756b054724d@kernel.org>
Date: Wed, 14 Feb 2024 18:18:29 +0100
From: Benjamin Tissoires <bentiss@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Jiri Kosina <jikos@...nel.org>,
Benjamin Tissoires <benjamin.tissoires@...hat.com>,
Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-input@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kselftest@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH RFC bpf-next v2 00/10] allow HID-BPF to do device IOs
[Still a RFC: there are a lot of FIXMEs in the code, and
calling the sleepable timer cb actually crashes.]
[Also using bpf-next as the base tree as there will be conflicting
changes otherwise]
This is crashing, and I have a few questions in the code (look for all
of the FIXMEs), so sending this now before I become insane :)
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 <ast@...nel.org>
To: Daniel Borkmann <daniel@...earbox.net>
To: John Fastabend <john.fastabend@...il.com>
To: Andrii Nakryiko <andrii@...nel.org>
To: Martin KaFai Lau <martin.lau@...ux.dev>
To: Eduard Zingerman <eddyz87@...il.com>
To: Song Liu <song@...nel.org>
To: Yonghong Song <yonghong.song@...ux.dev>
To: KP Singh <kpsingh@...nel.org>
To: Stanislav Fomichev <sdf@...gle.com>
To: Hao Luo <haoluo@...gle.com>
To: Jiri Olsa <jolsa@...nel.org>
To: Jiri Kosina <jikos@...nel.org>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>
To: Jonathan Corbet <corbet@....net>
To: Shuah Khan <shuah@...nel.org>
Cc: <bpf@...r.kernel.org>
Cc: <linux-kernel@...r.kernel.org>
Cc: <linux-input@...r.kernel.org>
Cc: <linux-doc@...r.kernel.org>
Cc: <linux-kselftest@...r.kernel.org>
Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>
---
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/20240209-hid-bpf-sleepable-v1-0-4cc895b5adbd@kernel.org
---
Benjamin Tissoires (10):
bpf/verifier: introduce in_sleepable() helper
bpf/helpers: introduce sleepable timers
bpf/verifier: allow more maps in sleepable bpf programs
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
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 | 12 ++
kernel/bpf/helpers.c | 105 +++++++++-
kernel/bpf/verifier.c | 91 +++++++-
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 +
11 files changed, 756 insertions(+), 94 deletions(-)
---
base-commit: 4f7a05917237b006ceae760507b3d15305769ade
change-id: 20240205-hid-bpf-sleepable-c01260fd91c4
Best regards,
--
Benjamin Tissoires <bentiss@...nel.org>
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