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Merge branch 'tools/bpf: Enable cross-building with clang'
Jean-Philippe Brucker says:
====================
Since v1 [1], I added Quentin's acks and applied Andrii's suggestions:
* Pass CFLAGS to libbpf link in patch 3
* Substitute CLANG_CROSS_FLAGS whole in HOST_CFLAGS to avoid accidents,
patch 4
Add support for cross-building BPF tools and selftests with clang, by
passing LLVM=1 or CC=clang to make, as well as CROSS_COMPILE. A single
clang toolchain can generate binaries for multiple architectures, so
instead of having prefixes such as aarch64-linux-gnu-gcc, clang uses the
-target parameter: `clang -target aarch64-linux-gnu'.
Patch 1 adds the parameter in Makefile.include so tools can easily
support this. Patch 2 prepares for the libbpf change from patch 3 (keep
building resolve_btfids's libbpf in the host arch, when cross-building
the kernel with clang). Patches 3-6 enable cross-building BPF tools with
clang.
[1] https://lore.kernel.org/bpf/20211122192019.1277299-1-jean-philippe@linaro.org/
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
+28
-14
+7
-6
tools/bpf/bpftool/Makefile
+7
-6
tools/bpf/bpftool/Makefile
···
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$(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
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$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
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DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \
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-
ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
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ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
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$(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)
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$(call QUIET_INSTALL, $@)
···
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SRCS += $(BFD_SRCS)
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endif
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+
HOST_CFLAGS = $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\
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$(subst $(CLANG_CROSS_FLAGS),,$(CFLAGS)))
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BPFTOOL_BOOTSTRAP := $(BOOTSTRAP_OUTPUT)bpftool
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BOOTSTRAP_OBJS = $(addprefix $(BOOTSTRAP_OUTPUT),main.o common.o json_writer.o gen.o btf.o xlated_dumper.o btf_dumper.o disasm.o)
···
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CFLAGS += $(if $(BUILD_BPF_SKELS),,-DBPFTOOL_WITHOUT_SKELETONS)
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$(BOOTSTRAP_OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
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$(QUIET_CC)$(HOSTCC) $(CFLAGS) -c -MMD $< -o $@
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$(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@
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$(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
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$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@
···
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endif
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$(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP)
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-
$(QUIET_LINK)$(HOSTCC) $(CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@
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$(QUIET_LINK)$(HOSTCC) $(HOST_CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@
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$(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
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$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) $(LIBS) -o $@
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$(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT)
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$(QUIET_CC)$(HOSTCC) \
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$(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),$(CFLAGS)) \
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-c -MMD $< -o $@
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$(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@
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$(OUTPUT)%.o: %.c
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$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@
+1
tools/bpf/resolve_btfids/Makefile
+1
tools/bpf/resolve_btfids/Makefile
+2
-2
tools/bpf/runqslower/Makefile
+2
-2
tools/bpf/runqslower/Makefile
···
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BPF_DESTDIR := $(BPFOBJ_OUTPUT)
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BPF_INCLUDE := $(BPF_DESTDIR)/include
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INCLUDES := -I$(OUTPUT) -I$(BPF_INCLUDE) -I$(abspath ../../include/uapi)
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CFLAGS := -g -Wall
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CFLAGS := -g -Wall $(CLANG_CROSS_FLAGS)
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# Try to detect best kernel BTF source
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KERNEL_REL := $(shell uname -r)
···
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$(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)
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$(Q)$(MAKE) $(submake_extras) -C ../bpftool OUTPUT=$(BPFTOOL_OUTPUT) \
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CC=$(HOSTCC) LD=$(HOSTLD)
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ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD)
+2
-1
tools/lib/bpf/Makefile
+2
-1
tools/lib/bpf/Makefile
···
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override CFLAGS += $(INCLUDES)
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override CFLAGS += -fvisibility=hidden
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override CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
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override CFLAGS += $(CLANG_CROSS_FLAGS)
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# flags specific for shared library
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SHLIB_FLAGS := -DSHARED -fPIC
···
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$(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
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$(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN_SHARED) $(VERSION_SCRIPT)
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$(QUIET_LINK)$(CC) $(LDFLAGS) \
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$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) \
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--shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \
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-Wl,--version-script=$(VERSION_SCRIPT) $< -lelf -lz -o $@
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@ln -sf $(@F) $(OUTPUT)libbpf.so
+12
-1
tools/scripts/Makefile.include
+12
-1
tools/scripts/Makefile.include
···
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ifeq ($(CC_NO_CLANG), 1)
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EXTRA_WARNINGS += -Wstrict-aliasing=3
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-
endif
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+
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else ifneq ($(CROSS_COMPILE),)
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CLANG_CROSS_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
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GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)gcc))
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ifneq ($(GCC_TOOLCHAIN_DIR),)
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CLANG_CROSS_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
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CLANG_CROSS_FLAGS += --sysroot=$(shell $(CROSS_COMPILE)gcc -print-sysroot)
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CLANG_CROSS_FLAGS += --gcc-toolchain=$(realpath $(GCC_TOOLCHAIN_DIR)/..)
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endif # GCC_TOOLCHAIN_DIR
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CFLAGS += $(CLANG_CROSS_FLAGS)
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AFLAGS += $(CLANG_CROSS_FLAGS)
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endif # CROSS_COMPILE
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# Hack to avoid type-punned warnings on old systems such as RHEL5:
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# We should be changing CFLAGS and checking gcc version, but this
+4
-4
tools/testing/selftests/bpf/Makefile
+4
-4
tools/testing/selftests/bpf/Makefile
···
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$(OUTPUT)/urandom_read: urandom_read.c
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$(call msg,BINARY,,$@)
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$(Q)$(CC) $(LDFLAGS) $< $(LDLIBS) -Wl,--build-id=sha1 -o $@
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$(Q)$(CC) $(CFLAGS) $(LDFLAGS) $< $(LDLIBS) -Wl,--build-id=sha1 -o $@
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$(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch])
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$(call msg,MOD,,$@)
···
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$(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \
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$(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool
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$(Q)$(MAKE) $(submake_extras) -C $(BPFTOOLDIR) \
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CC=$(HOSTCC) LD=$(HOSTLD) \
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ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) \
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EXTRA_CFLAGS='-g -O0' \
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OUTPUT=$(HOST_BUILD_DIR)/bpftool/ \
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LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/ \
···
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$(APIDIR)/linux/bpf.h \
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| $(HOST_BUILD_DIR)/libbpf
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$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) \
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EXTRA_CFLAGS='-g -O0' \
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EXTRA_CFLAGS='-g -O0' ARCH= CROSS_COMPILE= \
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OUTPUT=$(HOST_BUILD_DIR)/libbpf/ CC=$(HOSTCC) LD=$(HOSTLD) \
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DESTDIR=$(HOST_SCRATCH_DIR)/ prefix= all install_headers
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endif
···
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$(OUTPUT)/bench_bpf_loop.o \
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$(OUTPUT)/bench_strncmp.o
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$(call msg,BINARY,,$@)
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$(Q)$(CC) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
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$(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
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EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR) \
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prog_tests/tests.h map_tests/tests.h verifier/tests.h \