#taken from /samples/bpf/Makefile and removed all targets 

# SPDX-License-Identifier: GPL-2.0

BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools

# Libbpf dependencies
LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a

CGROUP_HELPERS := ../../tools/testing/selftests/bpf/cgroup_helpers.o
TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o

always-y += opensnitch.o

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

TPROGS_CFLAGS += -Wall -O2
TPROGS_CFLAGS += -Wmissing-prototypes
TPROGS_CFLAGS += -Wstrict-prototypes

TPROGS_CFLAGS += -I$(objtree)/usr/include
TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
TPROGS_CFLAGS += -I$(srctree)/tools/lib/
TPROGS_CFLAGS += -I$(srctree)/tools/include
TPROGS_CFLAGS += -I$(srctree)/tools/perf
TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0

ifdef SYSROOT
TPROGS_CFLAGS += --sysroot=$(SYSROOT)
TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
endif

TPROGCFLAGS_bpf_load.o += -Wno-unused-variable

TPROGS_LDLIBS			+= $(LIBBPF) -lelf -lz
TPROGLDLIBS_tracex4		+= -lrt
TPROGLDLIBS_trace_output	+= -lrt
TPROGLDLIBS_map_perf_test	+= -lrt
TPROGLDLIBS_test_overhead	+= -lrt
TPROGLDLIBS_xdpsock		+= -pthread

# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
#  make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
LLC ?= llc
CLANG ?= clang
LLVM_OBJCOPY ?= llvm-objcopy
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 "\#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; \
			  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) BPF_SAMPLES_PATH=$(CURDIR)

clean:
	$(MAKE) -C ../../ M=$(CURDIR) clean
	@find $(CURDIR) -type f -name '*~' -delete

$(LIBBPF): FORCE
# Fix up variables inherited from Kbuild that tools/ build system won't like
	$(MAKE) -C $(dir $@) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)" \
		LDFLAGS=$(TPROGS_LDFLAGS) srctree=$(BPF_SAMPLES_PATH)/../../ O=

$(obj)/syscall_nrs.h:	$(obj)/syscall_nrs.s FORCE
	$(call filechk,offsets,__SYSCALL_NRS_H__)

targets += syscall_nrs.s
clean-files += syscall_nrs.h

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

$(BPF_SAMPLES_PATH)/*.c: verify_target_bpf $(LIBBPF)
$(src)/*.c: verify_target_bpf $(LIBBPF)

$(obj)/tracex5_kern.o: $(obj)/syscall_nrs.h
$(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
$(obj)/hbm.o: $(src)/hbm.h
$(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h

-include $(BPF_SAMPLES_PATH)/Makefile.target

# 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.
$(obj)/%.o: $(src)/%.c
	@echo "  CLANG-bpf " $@
	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(BPF_EXTRA_CFLAGS) \
		-I$(obj) -I$(srctree)/tools/testing/selftests/bpf/ \
		-I$(srctree)/tools/lib/ \
		-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 $(CLANG_ARCH_ARGS) \
		-I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \
		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@
ifeq ($(DWARF2BTF),y)
	$(BTF_PAHOLE) -J $@
endif