samples/hid: add new hid BPF example

Everything should be available in the selftest part of the tree, but
providing an example without uhid and hidraw will be more easy to
follow for users.

This example will probably ever only work on the Etekcity Scroll 6E
because we need to adapt the various raw values to the actual device.

On that device, the X and Y axis will be swapped and inverted, and on
any other device, chances are high that the device will not work until
Ctrl-C is hit.

The Makefiles are taken from samples/bpf to not reinvent the wheel and
to force using in-kernel libbpf and bpftool.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 246 insertions, 0 deletions

diff --git a/samples/hid/Makefile b/samples/hid/Makefile
new file mode 100644
index 000000000000..8fe6ccfc5f29
--- /dev/null
+++ b/samples/hid/Makefile
@@ -0,0 +1,246 @@
+# SPDX-License-Identifier: GPL-2.0
+
+HID_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
+TOOLS_PATH := $(HID_SAMPLES_PATH)/../../tools
+
+pound := \#
+
+# List of programs to build
+tprogs-y += hid_mouse
+
+# Libbpf dependencies
+LIBBPF_SRC = $(TOOLS_PATH)/lib/bpf
+LIBBPF_OUTPUT = $(abspath $(HID_SAMPLES_PATH))/libbpf
+LIBBPF_DESTDIR = $(LIBBPF_OUTPUT)
+LIBBPF_INCLUDE = $(LIBBPF_DESTDIR)/include
+LIBBPF = $(LIBBPF_OUTPUT)/libbpf.a
+
+EXTRA_HEADERS := hid_bpf_attach.h
+EXTRA_BPF_HEADERS := hid_bpf_helpers.h
+
+hid_mouse-objs := hid_mouse.o
+
+# Tell kbuild to always build the programs
+always-y := $(tprogs-y)
+
+ifeq ($(ARCH), arm)
+# Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
+# headers when arm instruction set identification is requested.
+ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS))
+BPF_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR)
+TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
+endif
+
+ifeq ($(ARCH), mips)
+TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
+ifdef CONFIG_MACH_LOONGSON64
+BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-loongson64
+BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-generic
+endif
+endif
+
+TPROGS_CFLAGS += -Wall -O2
+TPROGS_CFLAGS += -Wmissing-prototypes
+TPROGS_CFLAGS += -Wstrict-prototypes
+
+TPROGS_CFLAGS += -I$(objtree)/usr/include
+TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
+TPROGS_CFLAGS += -I$(srctree)/tools/include
+
+ifdef SYSROOT
+TPROGS_CFLAGS += --sysroot=$(SYSROOT)
+TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
+endif
+
+TPROGS_LDLIBS			+= $(LIBBPF) -lelf -lz
+
+# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
+# make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang
+LLC ?= llc
+CLANG ?= clang
+OPT ?= opt
+LLVM_DIS ?= llvm-dis
+LLVM_OBJCOPY ?= llvm-objcopy
+LLVM_READELF ?= llvm-readelf
+BTF_PAHOLE ?= pahole
+
+# Detect that we're cross compiling and use the cross compiler
+ifdef CROSS_COMPILE
+CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%))
+endif
+
+# Don't evaluate probes and warnings if we need to run make recursively
+ifneq ($(src),)
+HDR_PROBE := $(shell printf "$(pound)include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
+	$(CC) $(TPROGS_CFLAGS) $(TPROGS_LDFLAGS) -x c - \
+	-o /dev/null 2>/dev/null && echo okay)
+
+ifeq ($(HDR_PROBE),)
+$(warning WARNING: Detected possible issues with include path.)
+$(warning WARNING: Please install kernel headers locally (make headers_install).)
+endif
+
+BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
+BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
+BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
+BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
+			  $(CLANG) -target bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
+			  $(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
+			  /bin/rm -f ./llvm_btf_verify.o)
+
+BPF_EXTRA_CFLAGS += -fno-stack-protector
+ifneq ($(BTF_LLVM_PROBE),)
+	BPF_EXTRA_CFLAGS += -g
+else
+ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
+	BPF_EXTRA_CFLAGS += -g
+	LLC_FLAGS += -mattr=dwarfris
+	DWARF2BTF = y
+endif
+endif
+endif
+
+# Trick to allow make to be run from this directory
+all:
+	$(MAKE) -C ../../ M=$(CURDIR) HID_SAMPLES_PATH=$(CURDIR)
+
+clean:
+	$(MAKE) -C ../../ M=$(CURDIR) clean
+	@find $(CURDIR) -type f -name '*~' -delete
+	@$(RM) -r $(CURDIR)/libbpf $(CURDIR)/bpftool
+
+$(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)
+# Fix up variables inherited from Kbuild that tools/ build system won't like
+	$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)" \
+		LDFLAGS=$(TPROGS_LDFLAGS) srctree=$(HID_SAMPLES_PATH)/../../ \
+		O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
+		$@ install_headers
+
+BPFTOOLDIR := $(TOOLS_PATH)/bpf/bpftool
+BPFTOOL_OUTPUT := $(abspath $(HID_SAMPLES_PATH))/bpftool
+BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool
+$(BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT)
+	$(MAKE) -C $(BPFTOOLDIR) srctree=$(HID_SAMPLES_PATH)/../../ 		\
+		OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap
+
+$(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
+	$(call msg,MKDIR,$@)
+	$(Q)mkdir -p $@
+
+FORCE:
+
+
+# Verify LLVM compiler tools are available and bpf target is supported by llc
+.PHONY: verify_cmds verify_target_bpf $(CLANG) $(LLC)
+
+verify_cmds: $(CLANG) $(LLC)
+	@for TOOL in $^ ; do \
+		if ! (which -- "$${TOOL}" > /dev/null 2>&1); then \
+			echo "*** ERROR: Cannot find LLVM tool $${TOOL}" ;\
+			exit 1; \
+		else true; fi; \
+	done
+
+verify_target_bpf: verify_cmds
+	@if ! (${LLC} -march=bpf -mattr=help > /dev/null 2>&1); then \
+		echo "*** ERROR: LLVM (${LLC}) does not support 'bpf' target" ;\
+		echo "   NOTICE: LLVM version >= 3.7.1 required" ;\
+		exit 2; \
+	else true; fi
+
+$(HID_SAMPLES_PATH)/*.c: verify_target_bpf $(LIBBPF)
+$(src)/*.c: verify_target_bpf $(LIBBPF)
+
+libbpf_hdrs: $(LIBBPF)
+
+.PHONY: libbpf_hdrs
+
+$(obj)/hid_mouse.o: $(obj)/hid_mouse.skel.h
+
+-include $(HID_SAMPLES_PATH)/Makefile.target
+
+VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))				\
+		     $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux))	\
+		     $(abspath ./vmlinux)
+VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+
+$(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
+ifeq ($(VMLINUX_H),)
+ifeq ($(VMLINUX_BTF),)
+	$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\
+		build the kernel or set VMLINUX_BTF or VMLINUX_H variable)
+endif
+	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+else
+	$(Q)cp "$(VMLINUX_H)" $@
+endif
+
+clean-files += vmlinux.h
+
+# Get Clang's default includes on this system, as opposed to those seen by
+# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
+#
+# Use '-idirafter': Don't interfere with include mechanics except where the
+# build would have failed anyways.
+define get_sys_includes
+$(shell $(1) -v -E - </dev/null 2>&1 \
+        | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
+$(shell $(1) -dM -E - </dev/null | grep '#define __riscv_xlen ' | sed 's/#define /-D/' | sed 's/ /=/')
+endef
+
+CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
+
+EXTRA_BPF_HEADERS_SRC := $(addprefix $(src)/,$(EXTRA_BPF_HEADERS))
+
+$(obj)/%.bpf.o: $(src)/%.bpf.c $(EXTRA_BPF_HEADERS_SRC) $(obj)/vmlinux.h
+	@echo "  CLANG-BPF " $@
+	$(Q)$(CLANG) -g -O2 -target bpf -D__TARGET_ARCH_$(SRCARCH) \
+		-Wno-compare-distinct-pointer-types -I$(srctree)/include \
+		-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
+		-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
+		-c $(filter %.bpf.c,$^) -o $@
+
+LINKED_SKELS := hid_mouse.skel.h
+clean-files += $(LINKED_SKELS)
+
+hid_mouse.skel.h-deps := hid_mouse.bpf.o hid_bpf_attach.bpf.o
+
+LINKED_BPF_SRCS := $(patsubst %.bpf.o,%.bpf.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))
+
+BPF_SRCS_LINKED := $(notdir $(wildcard $(src)/*.bpf.c))
+BPF_OBJS_LINKED := $(patsubst %.bpf.c,$(obj)/%.bpf.o, $(BPF_SRCS_LINKED))
+BPF_SKELS_LINKED := $(addprefix $(obj)/,$(LINKED_SKELS))
+
+$(BPF_SKELS_LINKED): $(BPF_OBJS_LINKED) $(BPFTOOL)
+	@echo "  BPF GEN-OBJ " $(@:.skel.h=)
+	$(Q)$(BPFTOOL) gen object $(@:.skel.h=.lbpf.o) $(addprefix $(obj)/,$($(@F)-deps))
+	@echo "  BPF GEN-SKEL" $(@:.skel.h=)
+	$(Q)$(BPFTOOL) gen skeleton $(@:.skel.h=.lbpf.o) name $(notdir $(@:.skel.h=)) > $@
+
+# asm/sysreg.h - inline assembly used by it is incompatible with llvm.
+# But, there is no easy way to fix it, so just exclude it since it is
+# useless for BPF samples.
+# below we use long chain of commands, clang | opt | llvm-dis | llc,
+# to generate final object file. 'clang' compiles the source into IR
+# with native target, e.g., x64, arm64, etc. 'opt' does bpf CORE IR builtin
+# processing (llvm12) and IR optimizations. 'llvm-dis' converts
+# 'opt' output to IR, and finally 'llc' generates bpf byte code.
+$(obj)/%.o: $(src)/%.c
+	@echo "  CLANG-bpf " $@
+	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(BPF_EXTRA_CFLAGS) \
+		-I$(obj) -I$(srctree)/tools/testing/selftests/bpf/ \
+		-I$(LIBBPF_INCLUDE) \
+		-D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign \
+		-D__TARGET_ARCH_$(SRCARCH) -Wno-compare-distinct-pointer-types \
+		-Wno-gnu-variable-sized-type-not-at-end \
+		-Wno-address-of-packed-member -Wno-tautological-compare \
+		-Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \
+		-fno-asynchronous-unwind-tables \
+		-I$(srctree)/samples/hid/ \
+		-O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \
+		$(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \
+		$(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@
+ifeq ($(DWARF2BTF),y)
+	$(BTF_PAHOLE) -J $@
+endif