# SPDX-License-Identifier: GPL-2.0
CLANG ?= clang
+SCRATCH_DIR := $(OUTPUT)/tools
+BUILD_DIR := $(SCRATCH_DIR)/build
+BPFDIR := $(abspath ../../../lib/bpf)
+APIDIR := $(abspath ../../../include/uapi)
+
CCINCLUDE += -I../../bpf
-CCINCLUDE += -I../../../../lib
CCINCLUDE += -I../../../../../usr/include/
+CCINCLUDE += -I$(SCRATCH_DIR)/include
+
+BPFOBJ := $(BUILD_DIR)/libbpf/libbpf.a
+
+MAKE_DIRS := $(BUILD_DIR)/libbpf
+$(MAKE_DIRS):
+ mkdir -p $@
TEST_CUSTOM_PROGS = $(OUTPUT)/bpf/nat6to4.o
all: $(TEST_CUSTOM_PROGS)
-$(OUTPUT)/%.o: %.c
- $(CLANG) -O2 -target bpf -c $< $(CCINCLUDE) -o $@
+# Get Clang's default includes on this system, as opposed to those seen by
+# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
+#
+# Use '-idirafter': Don't interfere with include mechanics except where the
+# build would have failed anyways.
+define get_sys_includes
+$(shell $(1) $(2) -v -E - </dev/null 2>&1 \
+ | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
+$(shell $(1) $(2) -dM -E - </dev/null | grep '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}')
+endef
+
+ifneq ($(CROSS_COMPILE),)
+CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
+endif
+
+CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
+
+$(TEST_CUSTOM_PROGS): $(BPFOBJ)
+ $(CLANG) -O2 -target bpf -c $(@:.o=.c) $(CCINCLUDE) $(CLANG_SYS_INCLUDES) -o $@
+
+$(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \
+ $(APIDIR)/linux/bpf.h \
+ | $(BUILD_DIR)/libbpf
+ $(MAKE) $(submake_extras) -C $(BPFDIR) OUTPUT=$(BUILD_DIR)/libbpf/ \
+ EXTRA_CFLAGS='-g -O0' \
+ DESTDIR=$(SCRATCH_DIR) prefix= all install_headers
+
+EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR)
-EXTRA_CLEAN := $(TEST_CUSTOM_PROGS)