selftests: add tests for the HID-bpf initial implementation

The tests are pretty basic:
- create a virtual uhid device that no userspace will like (to not mess
  up the running system)
- attach a BPF prog to it
- open the matching hidraw node
- inject one event and check:
  * that the BPF program can do something on the event stream
  * can modify the event stream
- add another test where we attach/detach BPF programs to see if we get
  errors

Note: the Makefile is extracted from selftests/bpf so we can rebuild
the libbpf and bpftool components from the current kernel tree without
relying on system installed components.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

MAINTAINERS

@@ -9100,6 +9100,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git
 F:	drivers/hid/
 F:	include/linux/hid*
 F:	include/uapi/linux/hid*
+F:	tools/testing/selftests/hid/
 
 HID LOGITECH DRIVERS
 R:	Filipe Laíns <lains@riseup.net>

tools/testing/selftests/Makefile

@@ -26,6 +26,7 @@ TARGETS += fpu
 TARGETS += ftrace
 TARGETS += futex
 TARGETS += gpio
+TARGETS += hid
 TARGETS += intel_pstate
 TARGETS += ipc
 TARGETS += ir

tools/testing/selftests/hid/.gitignore

+bpftool
+*.skel.h
+/tools
+hid_bpf

tools/testing/selftests/hid/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+# based on tools/testing/selftest/bpf/Makefile
+include ../../../build/Build.include
+include ../../../scripts/Makefile.arch
+include ../../../scripts/Makefile.include
+
+CXX ?= $(CROSS_COMPILE)g++
+
+CURDIR := $(abspath .)
+TOOLSDIR := $(abspath ../../..)
+TOP_SRCDIR = $(CURDIR)/../../../..
+KHDR_INCLUDES := $(TOP_SRCDIR)/usr/include
+LIBDIR := $(TOOLSDIR)/lib
+BPFDIR := $(LIBDIR)/bpf
+TOOLSINCDIR := $(TOOLSDIR)/include
+BPFTOOLDIR := $(TOOLSDIR)/bpf/bpftool
+HOSTPKG_CONFIG := pkg-config
+
+CFLAGS += -g -O0 -rdynamic -Wall -Werror -I$(KHDR_INCLUDES)
+LDLIBS += -lelf -lz -lrt -lpthread
+
+# Silence some warnings when compiled with clang
+ifneq ($(LLVM),)
+CFLAGS += -Wno-unused-command-line-argument
+endif
+
+# Order correspond to 'make run_tests' order
+TEST_GEN_PROGS = hid_bpf
+
+# Emit succinct information message describing current building step
+# $1 - generic step name (e.g., CC, LINK, etc);
+# $2 - optional "flavor" specifier; if provided, will be emitted as [flavor];
+# $3 - target (assumed to be file); only file name will be emitted;
+# $4 - optional extra arg, emitted as-is, if provided.
+ifeq ($(V),1)
+Q =
+msg =
+else
+Q = @
+msg = @printf '  %-8s%s %s%s\n' "$(1)" "$(if $(2), [$(2)])" "$(notdir $(3))" "$(if $(4), $(4))";
+MAKEFLAGS += --no-print-directory
+submake_extras := feature_display=0
+endif
+
+# override lib.mk's default rules
+OVERRIDE_TARGETS := 1
+override define CLEAN
+	$(call msg,CLEAN)
+	$(Q)$(RM) -r $(TEST_GEN_PROGS)
+	$(Q)$(RM) -r $(EXTRA_CLEAN)
+endef
+
+include ../lib.mk
+
+SCRATCH_DIR := $(OUTPUT)/tools
+BUILD_DIR := $(SCRATCH_DIR)/build
+INCLUDE_DIR := $(SCRATCH_DIR)/include
+BPFOBJ := $(BUILD_DIR)/libbpf/libbpf.a
+ifneq ($(CROSS_COMPILE),)
+HOST_BUILD_DIR		:= $(BUILD_DIR)/host
+HOST_SCRATCH_DIR	:= $(OUTPUT)/host-tools
+HOST_INCLUDE_DIR	:= $(HOST_SCRATCH_DIR)/include
+else
+HOST_BUILD_DIR		:= $(BUILD_DIR)
+HOST_SCRATCH_DIR	:= $(SCRATCH_DIR)
+HOST_INCLUDE_DIR	:= $(INCLUDE_DIR)
+endif
+HOST_BPFOBJ := $(HOST_BUILD_DIR)/libbpf/libbpf.a
+RESOLVE_BTFIDS := $(HOST_BUILD_DIR)/resolve_btfids/resolve_btfids
+
+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
+
+# Define simple and short `make test_progs`, `make test_sysctl`, etc targets
+# to build individual tests.
+# NOTE: Semicolon at the end is critical to override lib.mk's default static
+# rule for binaries.
+$(notdir $(TEST_GEN_PROGS)): %: $(OUTPUT)/% ;
+
+# sort removes libbpf duplicates when not cross-building
+MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf		\
+	       $(HOST_BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/resolve_btfids	\
+	       $(INCLUDE_DIR))
+$(MAKE_DIRS):
+	$(call msg,MKDIR,,$@)
+	$(Q)mkdir -p $@
+
+$(OUTPUT)/%.o: %.c
+	$(call msg,CC,,$@)
+	$(Q)$(CC) $(CFLAGS) -c $(filter %.c,$^) $(LDLIBS) -o $@
+
+# LLVM's ld.lld doesn't support all the architectures, so use it only on x86
+ifeq ($(SRCARCH),x86)
+LLD := lld
+else
+LLD := ld
+endif
+
+DEFAULT_BPFTOOL := $(HOST_SCRATCH_DIR)/sbin/bpftool
+
+TEST_GEN_PROGS_EXTENDED += $(DEFAULT_BPFTOOL)
+
+$(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED): $(BPFOBJ)
+
+BPFTOOL ?= $(DEFAULT_BPFTOOL)
+$(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
+		    $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool
+	$(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)			       \
+		    ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) 	       \
+		    EXTRA_CFLAGS='-g -O0'				       \
+		    OUTPUT=$(HOST_BUILD_DIR)/bpftool/			       \
+		    LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/		       \
+		    LIBBPF_DESTDIR=$(HOST_SCRATCH_DIR)/			       \
+		    prefix= DESTDIR=$(HOST_SCRATCH_DIR)/ install-bin
+
+$(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)		       \
+	   $(KHDR_INCLUDES)/linux/bpf.h					       \
+	   | $(BUILD_DIR)/libbpf
+	$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) OUTPUT=$(BUILD_DIR)/libbpf/ \
+		    EXTRA_CFLAGS='-g -O0'				       \
+		    DESTDIR=$(SCRATCH_DIR) prefix= all install_headers
+
+ifneq ($(BPFOBJ),$(HOST_BPFOBJ))
+$(HOST_BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)		       \
+		$(KHDR_INCLUDES)/linux/bpf.h					       \
+		| $(HOST_BUILD_DIR)/libbpf
+	$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR)                             \
+		    EXTRA_CFLAGS='-g -O0' ARCH= CROSS_COMPILE=		       \
+		    OUTPUT=$(HOST_BUILD_DIR)/libbpf/ CC=$(HOSTCC) LD=$(HOSTLD) \
+		    DESTDIR=$(HOST_SCRATCH_DIR)/ prefix= all install_headers
+endif
+
+$(INCLUDE_DIR)/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)" $@
+endif
+
+$(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids	\
+		       $(TOOLSDIR)/bpf/resolve_btfids/main.c	\
+		       $(TOOLSDIR)/lib/rbtree.c			\
+		       $(TOOLSDIR)/lib/zalloc.c			\
+		       $(TOOLSDIR)/lib/string.c			\
+		       $(TOOLSDIR)/lib/ctype.c			\
+		       $(TOOLSDIR)/lib/str_error_r.c
+	$(Q)$(MAKE) $(submake_extras) -C $(TOOLSDIR)/bpf/resolve_btfids	\
+		CC=$(HOSTCC) LD=$(HOSTLD) AR=$(HOSTAR) \
+		LIBBPF_INCLUDE=$(HOST_INCLUDE_DIR) \
+		OUTPUT=$(HOST_BUILD_DIR)/resolve_btfids/ BPFOBJ=$(HOST_BPFOBJ)
+
+# Get Clang's default includes on this system, as opposed to those seen by
+# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
+#
+# Use '-idirafter': Don't interfere with include mechanics except where the
+# build would have failed anyways.
+define get_sys_includes
+$(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 '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}')
+endef
+
+# Determine target endianness.
+IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
+			grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
+MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
+
+CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
+BPF_CFLAGS = -g -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN) 		\
+	     -I$(INCLUDE_DIR) -I$(CURDIR) -I$(KHDR_INCLUDES)		\
+	     -I$(abspath $(OUTPUT)/../usr/include)
+
+CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
+	       -Wno-compare-distinct-pointer-types
+
+# Build BPF object using Clang
+# $1 - input .c file
+# $2 - output .o file
+# $3 - CFLAGS
+define CLANG_BPF_BUILD_RULE
+	$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
+	$(Q)$(CLANG) $3 -O2 -target bpf -c $1 -mcpu=v3 -o $2
+endef
+# Similar to CLANG_BPF_BUILD_RULE, but with disabled alu32
+define CLANG_NOALU32_BPF_BUILD_RULE
+	$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
+	$(Q)$(CLANG) $3 -O2 -target bpf -c $1 -mcpu=v2 -o $2
+endef
+# Build BPF object using GCC
+define GCC_BPF_BUILD_RULE
+	$(call msg,GCC-BPF,$(TRUNNER_BINARY),$2)
+	$(Q)$(BPF_GCC) $3 -O2 -c $1 -o $2
+endef
+
+BPF_PROGS_DIR := progs
+BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
+BPF_SRCS := $(notdir $(wildcard $(BPF_PROGS_DIR)/*.c))
+BPF_OBJS := $(patsubst %.c,$(OUTPUT)/%.bpf.o, $(BPF_SRCS))
+BPF_SKELS := $(patsubst %.c,$(OUTPUT)/%.skel.h, $(BPF_SRCS))
+TEST_GEN_FILES += $(BPF_OBJS)
+
+$(BPF_PROGS_DIR)-bpfobjs := y
+$(BPF_OBJS): $(OUTPUT)/%.bpf.o:				\
+	     $(BPF_PROGS_DIR)/%.c			\
+	     $(wildcard $(BPF_PROGS_DIR)/*.h)		\
+	     $(INCLUDE_DIR)/vmlinux.h				\
+	     $(wildcard $(BPFDIR)/hid_bpf_*.h)			\
+	     $(wildcard $(BPFDIR)/*.bpf.h)			\
+	     | $(OUTPUT) $(BPFOBJ)
+	$(call $(BPF_BUILD_RULE),$<,$@, $(BPF_CFLAGS))
+
+$(BPF_SKELS): %.skel.h: %.bpf.o $(BPFTOOL) | $(OUTPUT)
+	$(call msg,GEN-SKEL,$(BINARY),$@)
+	$(Q)$(BPFTOOL) gen object $(<:.o=.linked1.o) $<
+	$(Q)$(BPFTOOL) gen skeleton $(<:.o=.linked1.o) name $(notdir $(<:.bpf.o=)) > $@
+
+$(OUTPUT)/%:%.c $(BPF_SKELS)
+	$(call msg,BINARY,,$@)
+	$(Q)$(LINK.c) $^ $(LDLIBS) -o $@
+
+EXTRA_CLEAN := $(SCRATCH_DIR) $(HOST_SCRATCH_DIR) feature bpftool	\
+	$(addprefix $(OUTPUT)/,*.o *.skel.h no_alu32)

tools/testing/selftests/hid/config

+CONFIG_BPF_EVENTS=y
+CONFIG_BPFILTER=y
+CONFIG_BPF_JIT_ALWAYS_ON=y
+CONFIG_BPF_JIT=y
+CONFIG_BPF_KPROBE_OVERRIDE=y
+CONFIG_BPF_LSM=y
+CONFIG_BPF_PRELOAD_UMD=y
+CONFIG_BPF_PRELOAD=y
+CONFIG_BPF_STREAM_PARSER=y
+CONFIG_BPF_SYSCALL=y
+CONFIG_BPF=y
+CONFIG_CGROUP_BPF=y
+CONFIG_DEBUG_INFO_BTF=y
+CONFIG_FPROBE=y
+CONFIG_FTRACE_SYSCALLS=y
+CONFIG_FUNCTION_TRACER=y
+CONFIG_HIDRAW=y
+CONFIG_HID=y
+CONFIG_INPUT_EVDEV=y
+CONFIG_UHID=y

tools/testing/selftests/hid/progs/hid.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Red hat */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "hid_bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct attach_prog_args {
+	int prog_fd;
+	unsigned int hid;
+	int retval;
+};
+
+__u64 callback_check = 52;
+__u64 callback2_check = 52;
+
+SEC("?fmod_ret/hid_bpf_device_event")
+int BPF_PROG(hid_first_event, struct hid_bpf_ctx *hid_ctx)
+{
+	__u8 *rw_data = hid_bpf_get_data(hid_ctx, 0 /* offset */, 3 /* size */);
+
+	if (!rw_data)
+		return 0; /* EPERM check */
+
+	callback_check = rw_data[1];
+
+	rw_data[2] = rw_data[1] + 5;
+
+	return 0;
+}
+
+SEC("syscall")
+int attach_prog(struct attach_prog_args *ctx)
+{
+	ctx->retval = hid_bpf_attach_prog(ctx->hid,
+					  ctx->prog_fd,
+					  0);
+	return 0;
+}

tools/testing/selftests/hid/progs/hid_bpf_helpers.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+
+#ifndef __HID_BPF_HELPERS_H
+#define __HID_BPF_HELPERS_H
+
+/* following are kfuncs exported by HID for HID-BPF */
+extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
+			      unsigned int offset,
+			      const size_t __sz) __ksym;
+extern int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, u32 flags) __ksym;
+
+#endif /* __HID_BPF_HELPERS_H */