From cebdb7374577ac6e14afb11311af8c2c44a259fa Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Thu, 16 Dec 2021 16:38:38 +0000 Subject: [PATCH 1/6] tools: Help cross-building with clang Cross-compilation with clang uses the -target parameter rather than a toolchain prefix. Just like the kernel Makefile, add that parameter to CFLAGS when CROSS_COMPILE is set. Unlike the kernel Makefile, we use the --sysroot and --gcc-toolchain options because unlike the kernel, tools require standard libraries. Commit c91d4e47e10e ("Makefile: Remove '--gcc-toolchain' flag") provides some background about --gcc-toolchain. Normally clang finds on its own the additional utilities and libraries that it needs (for example GNU ld or glibc). On some systems however, this autodetection doesn't work. There, our only recourse is asking GCC directly, and pass the result to --sysroot and --gcc-toolchain. Of course that only works when a cross GCC is available. Autodetection worked fine on Debian, but to use the aarch64-linux-gnu toolchain from Archlinux I needed both --sysroot (for crt1.o) and --gcc-toolchain (for crtbegin.o, -lgcc). The --prefix parameter wasn't needed there, but it might be useful on other distributions. Use the CLANG_CROSS_FLAGS variable instead of CLANG_FLAGS because it allows tools such as bpftool, that need to build both host and target binaries, to easily filter out the cross-build flags from CFLAGS. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet Acked-by: Nick Desaulniers Link: https://lore.kernel.org/bpf/20211216163842.829836-2-jean-philippe@linaro.org --- tools/scripts/Makefile.include | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include index 071312f5eb92..b0be5f40a3f1 100644 --- a/tools/scripts/Makefile.include +++ b/tools/scripts/Makefile.include @@ -87,7 +87,18 @@ LLVM_STRIP ?= llvm-strip ifeq ($(CC_NO_CLANG), 1) EXTRA_WARNINGS += -Wstrict-aliasing=3 -endif + +else ifneq ($(CROSS_COMPILE),) +CLANG_CROSS_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%)) +GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)gcc)) +ifneq ($(GCC_TOOLCHAIN_DIR),) +CLANG_CROSS_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) +CLANG_CROSS_FLAGS += --sysroot=$(shell $(CROSS_COMPILE)gcc -print-sysroot) +CLANG_CROSS_FLAGS += --gcc-toolchain=$(realpath $(GCC_TOOLCHAIN_DIR)/..) +endif # GCC_TOOLCHAIN_DIR +CFLAGS += $(CLANG_CROSS_FLAGS) +AFLAGS += $(CLANG_CROSS_FLAGS) +endif # CROSS_COMPILE # Hack to avoid type-punned warnings on old systems such as RHEL5: # We should be changing CFLAGS and checking gcc version, but this From bf1be903461a404a9d1c720b0872501ca35abc89 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Thu, 16 Dec 2021 16:38:39 +0000 Subject: [PATCH 2/6] tools/resolve_btfids: Support cross-building the kernel with clang The CROSS_COMPILE variable may be present during resolve_btfids build if the kernel is being cross-built. Since resolve_btfids is always executed on the host, we set CC to HOSTCC in order to use the host toolchain when cross-building with GCC. But instead of a toolchain prefix, cross-build with clang uses a "-target" parameter, which Makefile.include deduces from the CROSS_COMPILE variable. In order to avoid cross-building libbpf, clear CROSS_COMPILE before building resolve_btfids. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20211216163842.829836-3-jean-philippe@linaro.org --- tools/bpf/resolve_btfids/Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile index 751643f860b2..9ddeca947635 100644 --- a/tools/bpf/resolve_btfids/Makefile +++ b/tools/bpf/resolve_btfids/Makefile @@ -19,6 +19,7 @@ CC = $(HOSTCC) LD = $(HOSTLD) ARCH = $(HOSTARCH) RM ?= rm +CROSS_COMPILE = OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/ From 4980beb4cda2bc413a3a044e1851b0daaf137bf6 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Thu, 16 Dec 2021 16:38:40 +0000 Subject: [PATCH 3/6] tools/libbpf: Enable cross-building with clang Cross-building using clang requires passing the "-target" flag rather than using the CROSS_COMPILE prefix. Makefile.include transforms CROSS_COMPILE into CLANG_CROSS_FLAGS. Add them to the CFLAGS. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20211216163842.829836-4-jean-philippe@linaro.org --- tools/lib/bpf/Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile index 5f7086fae31c..f947b61b2107 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -90,6 +90,7 @@ override CFLAGS += -Werror -Wall override CFLAGS += $(INCLUDES) override CFLAGS += -fvisibility=hidden override CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 +override CFLAGS += $(CLANG_CROSS_FLAGS) # flags specific for shared library SHLIB_FLAGS := -DSHARED -fPIC @@ -162,7 +163,7 @@ $(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION) $(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN_SHARED) $(VERSION_SCRIPT) - $(QUIET_LINK)$(CC) $(LDFLAGS) \ + $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) \ --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \ -Wl,--version-script=$(VERSION_SCRIPT) $< -lelf -lz -o $@ @ln -sf $(@F) $(OUTPUT)libbpf.so From bdadbb44c90aedaa74d46f1b113bd845774efa39 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Thu, 16 Dec 2021 16:38:41 +0000 Subject: [PATCH 4/6] bpftool: Enable cross-building with clang Cross-building using clang requires passing the "-target" flag rather than using the CROSS_COMPILE prefix. Makefile.include transforms CROSS_COMPILE into CLANG_CROSS_FLAGS, and adds that to CFLAGS. Remove the cross flags for the bootstrap bpftool, and erase the CROSS_COMPILE flag for the bootstrap libbpf. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20211216163842.829836-5-jean-philippe@linaro.org --- tools/bpf/bpftool/Makefile | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile index 42eb8eee3d89..83369f55df61 100644 --- a/tools/bpf/bpftool/Makefile +++ b/tools/bpf/bpftool/Makefile @@ -57,7 +57,7 @@ $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_ $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT) $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \ DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \ - ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers + ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR) $(call QUIET_INSTALL, $@) @@ -152,6 +152,9 @@ CFLAGS += -DHAVE_LIBBFD_SUPPORT SRCS += $(BFD_SRCS) endif +HOST_CFLAGS = $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\ + $(subst $(CLANG_CROSS_FLAGS),,$(CFLAGS))) + BPFTOOL_BOOTSTRAP := $(BOOTSTRAP_OUTPUT)bpftool BOOTSTRAP_OBJS = $(addprefix $(BOOTSTRAP_OUTPUT),main.o common.o json_writer.o gen.o btf.o xlated_dumper.o btf_dumper.o disasm.o) @@ -202,7 +205,7 @@ endif CFLAGS += $(if $(BUILD_BPF_SKELS),,-DBPFTOOL_WITHOUT_SKELETONS) $(BOOTSTRAP_OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c - $(QUIET_CC)$(HOSTCC) $(CFLAGS) -c -MMD $< -o $@ + $(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@ $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c $(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@ @@ -213,15 +216,13 @@ ifneq ($(feature-zlib), 1) endif $(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP) - $(QUIET_LINK)$(HOSTCC) $(CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@ + $(QUIET_LINK)$(HOSTCC) $(HOST_CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@ $(OUTPUT)bpftool: $(OBJS) $(LIBBPF) $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) $(LIBS) -o $@ $(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT) - $(QUIET_CC)$(HOSTCC) \ - $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),$(CFLAGS)) \ - -c -MMD $< -o $@ + $(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@ $(OUTPUT)%.o: %.c $(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@ From bb7b75e860eec31aa67b83935849fdc46418c13e Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Thu, 16 Dec 2021 16:38:42 +0000 Subject: [PATCH 5/6] tools/runqslower: Enable cross-building with clang Cross-building using clang requires passing the "-target" flag rather than using the CROSS_COMPILE prefix. Makefile.include transforms CROSS_COMPILE into CLANG_CROSS_FLAGS. Add them to CFLAGS, and erase CROSS_COMPILE for the bpftool build, since it needs to be executed on the host. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20211216163842.829836-6-jean-philippe@linaro.org --- tools/bpf/runqslower/Makefile | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile index 8791d0e2762b..da6de16a3dfb 100644 --- a/tools/bpf/runqslower/Makefile +++ b/tools/bpf/runqslower/Makefile @@ -12,7 +12,7 @@ BPFOBJ := $(BPFOBJ_OUTPUT)libbpf.a BPF_DESTDIR := $(BPFOBJ_OUTPUT) BPF_INCLUDE := $(BPF_DESTDIR)/include INCLUDES := -I$(OUTPUT) -I$(BPF_INCLUDE) -I$(abspath ../../include/uapi) -CFLAGS := -g -Wall +CFLAGS := -g -Wall $(CLANG_CROSS_FLAGS) # Try to detect best kernel BTF source KERNEL_REL := $(shell uname -r) @@ -88,4 +88,4 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(BPFOBJ_OU $(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT) $(Q)$(MAKE) $(submake_extras) -C ../bpftool OUTPUT=$(BPFTOOL_OUTPUT) \ - CC=$(HOSTCC) LD=$(HOSTLD) + ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) From ea79020a2d9eea62b12d90f0c11b7d70fcadc172 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Thu, 16 Dec 2021 16:38:43 +0000 Subject: [PATCH 6/6] selftests/bpf: Enable cross-building with clang Cross building using clang requires passing the "-target" flag rather than using the CROSS_COMPILE prefix. Makefile.include transforms CROSS_COMPILE into CLANG_CROSS_FLAGS. Clear CROSS_COMPILE for bpftool and the host libbpf, and use the clang flags for urandom_read and bench. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20211216163842.829836-7-jean-philippe@linaro.org --- tools/testing/selftests/bpf/Makefile | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 43f6f3159431..42ffc24e9e71 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -170,7 +170,7 @@ $(OUTPUT)/%:%.c $(OUTPUT)/urandom_read: urandom_read.c $(call msg,BINARY,,$@) - $(Q)$(CC) $(LDFLAGS) $< $(LDLIBS) -Wl,--build-id=sha1 -o $@ + $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $< $(LDLIBS) -Wl,--build-id=sha1 -o $@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch]) $(call msg,MOD,,$@) @@ -217,7 +217,7 @@ BPFTOOL ?= $(DEFAULT_BPFTOOL) $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \ $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool $(Q)$(MAKE) $(submake_extras) -C $(BPFTOOLDIR) \ - CC=$(HOSTCC) LD=$(HOSTLD) \ + ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) \ EXTRA_CFLAGS='-g -O0' \ OUTPUT=$(HOST_BUILD_DIR)/bpftool/ \ LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/ \ @@ -248,7 +248,7 @@ $(HOST_BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \ $(APIDIR)/linux/bpf.h \ | $(HOST_BUILD_DIR)/libbpf $(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) \ - EXTRA_CFLAGS='-g -O0' \ + EXTRA_CFLAGS='-g -O0' ARCH= CROSS_COMPILE= \ OUTPUT=$(HOST_BUILD_DIR)/libbpf/ CC=$(HOSTCC) LD=$(HOSTLD) \ DESTDIR=$(HOST_SCRATCH_DIR)/ prefix= all install_headers endif @@ -551,7 +551,7 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \ $(OUTPUT)/bench_bpf_loop.o \ $(OUTPUT)/bench_strncmp.o $(call msg,BINARY,,$@) - $(Q)$(CC) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@ + $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@ EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR) \ prog_tests/tests.h map_tests/tests.h verifier/tests.h \