Messages in this thread | | | Date | Fri, 27 May 2022 10:26:01 +0300 | Subject | Re: [PATCH bpf-next v5 00/17] Introduce eBPF support for HID devices | From | Tero Kristo <> |
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Hi Benjamin,
I noticed a couple of issues with this series, but was able to fix/workaround them locally and got my USI program working with it.
1) You seem to be missing tools/include/uapi/linux/hid_bpf.h from index, I wasn't able to compile the selftests (or my own program) without adding this. It is included from tools/testing/selftests/bpf/prog_tests/hid.c: #include <linux/hid_bpf.h>
2) The limitation of needing to hardcode the size for hid_bpf_get_data() seems somewhat worrying, especially as the kernel side limits this to the ctx->allocated_size. I used a sufficiently large number for my purposes for now (256) which seems to work, but how should I handle my case where I basically need to read the whole input report and parse certain portions of it? How does the HID subsystem select the size of the ctx->allocated_size?
-Tero
On 18/05/2022 23:59, Benjamin Tissoires wrote: > Hi, > > And here comes the v5 of the HID-BPF series. > > I managed to achive the same functionalities than v3 this time. > Handling per-device BPF program was "interesting" to say the least, > but I don't know if we can have a generic BPF way of handling such > situation. > > The interesting bits is that now the BPF core changes are rather small, > and I am mostly using existing facilities. > I didn't managed to write selftests for the RET_PTR_TO_MEM kfunc, > because I can not call kmalloc while in a SEC("tc") program to match > what the other kfunc tests are doing. > And AFAICT, the most interesting bits would be to implement verifier > selftests, which are way out of my league, given that they are > implemented as plain bytecode. > > The logic is the following (see also the last patch for some more > documentation): > - hid-bpf first preloads a BPF program in the kernel that does a few > things: > * find out which attach_btf_id are associated with our trace points > * adds a bpf_tail_call() BPF program that I can use to "call" any > other BPF program stored into a jump table > * monitors the releases of struct bpf_prog, and when there are no > other users than us, detach the bpf progs from the HID devices > - users then declare their tracepoints and then call > hid_bpf_attach_prog() in a SEC("syscall") program > - hid-bpf then calls multiple time the bpf_tail_call() program with a > different index in the jump table whenever there is an event coming > from a matching HID device > > Note that I am tempted to pin an "attach_hid_program" in the bpffs so > that users don't need to declare one, but I am afraid this will be one > more API to handle, so maybe not. > > I am also wondering if I should not strip out hid_bpf_jmp_table of most > of its features and implement everything as a BPF program. This might > remove the need to add the kernel light skeleton implementations of map > modifications, and might also possibly be more re-usable for other > subsystems. But every plan I do in my head involves a lot of back and > forth between the kernel and BPF to achieve the same, which doesn't feel > right. The tricky part is the RCU list of programs that is stored in each > device and also the global state of the jump table. > Anyway, something to look for in a next version if there is a push for it. > > FWIW, patch 1 is something I'd like to get merged sooner. With 2 > colleagues, we are also working on supporting the "revoke" functionality > of a fd for USB and for hidraw. While hidraw can be emulated with the > current features, we need the syscall kfuncs for USB, because when we > revoke a USB access, we also need to kick out the user, and for that, we > need to actually execute code in the kernel from a userspace event. > > Anyway, happy reviewing. > > Cheers, > Benjamin > > [Patch series based on commit 68084a136420 ("selftests/bpf: Fix building bpf selftests statically") > in the bpf-next tree] > > Benjamin Tissoires (17): > bpf/btf: also allow kfunc in tracing and syscall programs > bpf/verifier: allow kfunc to return an allocated mem > bpf: prepare for more bpf syscall to be used from kernel and user > space. > libbpf: add map_get_fd_by_id and map_delete_elem in light skeleton > HID: core: store the unique system identifier in hid_device > HID: export hid_report_type to uapi > HID: initial BPF implementation > selftests/bpf: add tests for the HID-bpf initial implementation > HID: bpf: allocate data memory for device_event BPF programs > selftests/bpf/hid: add test to change the report size > HID: bpf: introduce hid_hw_request() > selftests/bpf: add tests for bpf_hid_hw_request > HID: bpf: allow to change the report descriptor > selftests/bpf: add report descriptor fixup tests > samples/bpf: add new hid_mouse example > selftests/bpf: Add a test for BPF_F_INSERT_HEAD > Documentation: add HID-BPF docs > > Documentation/hid/hid-bpf.rst | 528 ++++++++++ > Documentation/hid/index.rst | 1 + > drivers/hid/Kconfig | 2 + > drivers/hid/Makefile | 2 + > drivers/hid/bpf/Kconfig | 19 + > drivers/hid/bpf/Makefile | 11 + > drivers/hid/bpf/entrypoints/Makefile | 88 ++ > drivers/hid/bpf/entrypoints/README | 4 + > drivers/hid/bpf/entrypoints/entrypoints.bpf.c | 78 ++ > .../hid/bpf/entrypoints/entrypoints.lskel.h | 782 ++++++++++++++ > drivers/hid/bpf/hid_bpf_dispatch.c | 565 ++++++++++ > drivers/hid/bpf/hid_bpf_dispatch.h | 28 + > drivers/hid/bpf/hid_bpf_jmp_table.c | 587 +++++++++++ > drivers/hid/hid-core.c | 43 +- > include/linux/btf.h | 7 + > include/linux/hid.h | 29 +- > include/linux/hid_bpf.h | 144 +++ > include/uapi/linux/hid.h | 12 + > include/uapi/linux/hid_bpf.h | 25 + > kernel/bpf/btf.c | 47 +- > kernel/bpf/syscall.c | 10 +- > kernel/bpf/verifier.c | 72 +- > samples/bpf/.gitignore | 1 + > samples/bpf/Makefile | 23 + > samples/bpf/hid_mouse.bpf.c | 134 +++ > samples/bpf/hid_mouse.c | 157 +++ > tools/lib/bpf/skel_internal.h | 23 + > tools/testing/selftests/bpf/config | 3 + > tools/testing/selftests/bpf/prog_tests/hid.c | 990 ++++++++++++++++++ > tools/testing/selftests/bpf/progs/hid.c | 222 ++++ > 30 files changed, 4593 insertions(+), 44 deletions(-) > create mode 100644 Documentation/hid/hid-bpf.rst > create mode 100644 drivers/hid/bpf/Kconfig > create mode 100644 drivers/hid/bpf/Makefile > create mode 100644 drivers/hid/bpf/entrypoints/Makefile > create mode 100644 drivers/hid/bpf/entrypoints/README > create mode 100644 drivers/hid/bpf/entrypoints/entrypoints.bpf.c > create mode 100644 drivers/hid/bpf/entrypoints/entrypoints.lskel.h > create mode 100644 drivers/hid/bpf/hid_bpf_dispatch.c > create mode 100644 drivers/hid/bpf/hid_bpf_dispatch.h > create mode 100644 drivers/hid/bpf/hid_bpf_jmp_table.c > create mode 100644 include/linux/hid_bpf.h > create mode 100644 include/uapi/linux/hid_bpf.h > create mode 100644 samples/bpf/hid_mouse.bpf.c > create mode 100644 samples/bpf/hid_mouse.c > create mode 100644 tools/testing/selftests/bpf/prog_tests/hid.c > create mode 100644 tools/testing/selftests/bpf/progs/hid.c >
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