Commit f5c27da4 authored by Benjamin Tissoires's avatar Benjamin Tissoires Committed by Jiri Kosina
Browse files

HID: initial BPF implementation 



Declare an entry point that can use fmod_ret BPF programs, and
also an API to access and change the incoming data.

A simpler implementation would consist in just calling
hid_bpf_device_event() for any incoming event and let users deal
with the fact that they will be called for any event of any device.

The goal of HID-BPF is to partially replace drivers, so this situation
can be problematic because we might have programs which will step on
each other toes.

For that, we add a new API hid_bpf_attach_prog() that can be called
from a syscall and we manually deal with a jump table in hid-bpf.

Whenever we add a program to the jump table (in other words, when we
attach a program to a HID device), we keep the number of time we added
this program in the jump table so we can release it whenever there are
no other users.

HID devices have an RCU protected list of available programs in the
jump table, and those programs are called one after the other thanks
to bpf_tail_call().

To achieve the detection of users losing their fds on the programs we
attached, we add 2 tracing facilities on bpf_prog_release() (for when
a fd is closed) and bpf_free_inode() (for when a pinned program gets
unpinned).

Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarBenjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 25621bcc

drivers/hid/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -1284,6 +1284,8 @@ config HID_KUNIT_TEST 


endmenu



source "drivers/hid/bpf/Kconfig"



endif # HID



source "drivers/hid/usbhid/Kconfig"

drivers/hid/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -5,6 +5,8 @@ 
hid-y			:= hid-core.o hid-input.o hid-quirks.o

hid-$(CONFIG_DEBUG_FS)		+= hid-debug.o



obj-$(CONFIG_HID_BPF)		+= bpf/



obj-$(CONFIG_HID)		+= hid.o

obj-$(CONFIG_UHID)		+= uhid.o

drivers/hid/bpf/Kconfig

0 → 100644
+17 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0-only

menu "HID-BPF support"



config HID_BPF

	bool "HID-BPF support"

	default HID_SUPPORT

	depends on BPF && BPF_SYSCALL

	help

	This option allows to support eBPF programs on the HID subsystem.

	eBPF programs can fix HID devices in a lighter way than a full

	kernel patch and allow a lot more flexibility.



	For documentation, see Documentation/hid/hid-bpf.rst



	If unsure, say Y.



endmenu

drivers/hid/bpf/Makefile

0 → 100644
+11 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

#

# Makefile for HID-BPF

#



LIBBPF_INCLUDE = $(srctree)/tools/lib



obj-$(CONFIG_HID_BPF) += hid_bpf.o

CFLAGS_hid_bpf_dispatch.o += -I$(LIBBPF_INCLUDE)

CFLAGS_hid_bpf_jmp_table.o += -I$(LIBBPF_INCLUDE)

hid_bpf-objs += hid_bpf_dispatch.o hid_bpf_jmp_table.o

drivers/hid/bpf/entrypoints/Makefile

0 → 100644
+93 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

OUTPUT := .output

abs_out := $(abspath $(OUTPUT))



CLANG ?= clang

LLC ?= llc

LLVM_STRIP ?= llvm-strip



TOOLS_PATH := $(abspath ../../../../tools)

BPFTOOL_SRC := $(TOOLS_PATH)/bpf/bpftool

BPFTOOL_OUTPUT := $(abs_out)/bpftool

DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool

BPFTOOL ?= $(DEFAULT_BPFTOOL)



LIBBPF_SRC := $(TOOLS_PATH)/lib/bpf

LIBBPF_OUTPUT := $(abs_out)/libbpf

LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)

LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include

BPFOBJ := $(LIBBPF_OUTPUT)/libbpf.a



INCLUDES := -I$(OUTPUT) -I$(LIBBPF_INCLUDE) -I$(TOOLS_PATH)/include/uapi

CFLAGS := -g -Wall



VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)				\

		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\

		     ../../../../vmlinux				\

		     /sys/kernel/btf/vmlinux				\

		     /boot/vmlinux-$(shell uname -r)

VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))

ifeq ($(VMLINUX_BTF),)

$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")

endif



ifeq ($(V),1)

Q =

msg =

else

Q = @

msg = @printf '  %-8s %s%s\n' "$(1)" "$(notdir $(2))" "$(if $(3), $(3))";

MAKEFLAGS += --no-print-directory

submake_extras := feature_display=0

endif



.DELETE_ON_ERROR:



.PHONY: all clean



all: entrypoints.lskel.h



clean:

	$(call msg,CLEAN)

	$(Q)rm -rf $(OUTPUT) entrypoints



entrypoints.lskel.h: $(OUTPUT)/entrypoints.bpf.o | $(BPFTOOL)

	$(call msg,GEN-SKEL,$@)

	$(Q)$(BPFTOOL) gen skeleton -L $< > $@





$(OUTPUT)/entrypoints.bpf.o: entrypoints.bpf.c $(OUTPUT)/vmlinux.h $(BPFOBJ) | $(OUTPUT)

	$(call msg,BPF,$@)

	$(Q)$(CLANG) -g -O2 -target bpf $(INCLUDES)			      \

		 -c $(filter %.c,$^) -o $@ &&				      \

	$(LLVM_STRIP) -g $@



$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)

ifeq ($(VMLINUX_H),)

	$(call msg,GEN,,$@)

	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@

else

	$(call msg,CP,,$@)

	$(Q)cp "$(VMLINUX_H)" $@

endif



$(OUTPUT) $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):

	$(call msg,MKDIR,$@)

	$(Q)mkdir -p $@



$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)

	$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC)			       \

		    OUTPUT=$(abspath $(dir $@))/ prefix=		       \

		    DESTDIR=$(LIBBPF_DESTDIR) $(abspath $@) install_headers



ifeq ($(CROSS_COMPILE),)

$(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)

	$(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC)			       \

		    OUTPUT=$(BPFTOOL_OUTPUT)/				       \

		    LIBBPF_BOOTSTRAP_OUTPUT=$(LIBBPF_OUTPUT)/		       \

		    LIBBPF_BOOTSTRAP_DESTDIR=$(LIBBPF_DESTDIR)/ bootstrap

else

$(DEFAULT_BPFTOOL): | $(BPFTOOL_OUTPUT)

	$(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC)			       \

		    OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap

endif