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.
Jean-Philippe Brucker (6): tools: Help cross-building with clang tools/resolve_btfids: Support cross-building the kernel with clang tools/libbpf: Enable cross-building with clang bpftool: Enable cross-building with clang tools/runqslower: Enable cross-building with clang selftests/bpf: Enable cross-building with clang
tools/bpf/bpftool/Makefile | 13 +++++++------ tools/bpf/resolve_btfids/Makefile | 1 + tools/bpf/runqslower/Makefile | 4 ++-- tools/lib/bpf/Makefile | 3 ++- tools/scripts/Makefile.include | 13 ++++++++++++- tools/testing/selftests/bpf/Makefile | 8 ++++---- 6 files changed, 28 insertions(+), 14 deletions(-)
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 jean-philippe@linaro.org --- Most tools I looked at needed additional changes to support cross-build with clang. I've only done the work for bpf tools. --- 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
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 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/
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 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..fe9201862aed 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) $(CLANG_CROSS_FLAGS) $(LDFLAGS) \ --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \ -Wl,--version-script=$(VERSION_SCRIPT) $< -lelf -lz -o $@ @ln -sf $(@F) $(OUTPUT)libbpf.so
On Mon, Nov 22, 2021 at 11:24 AM Jean-Philippe Brucker jean-philippe@linaro.org wrote:
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 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..fe9201862aed 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) $(CLANG_CROSS_FLAGS) $(LDFLAGS) \
I haven't checked, but what would happen if we just use $(CFLAGS) here? Would it still work?
--shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \ -Wl,--version-script=$(VERSION_SCRIPT) $< -lelf -lz -o $@ @ln -sf $(@F) $(OUTPUT)libbpf.so-- 2.33.1
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. Filter out the cross flags for the bootstrap bpftool, and erase the CROSS_COMPILE flag for the bootstrap libbpf.
Signed-off-by: Jean-Philippe Brucker 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..b0f3e17d981a 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),\ + $(filter-out $(CLANG_CROSS_FLAGS),$(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 $@
On Mon, Nov 22, 2021 at 11:23 AM Jean-Philippe Brucker jean-philippe@linaro.org wrote:
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. Filter out the cross flags for the bootstrap bpftool, and erase the CROSS_COMPILE flag for the bootstrap libbpf.
Signed-off-by: Jean-Philippe Brucker 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..b0f3e17d981a 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),\
$(filter-out $(CLANG_CROSS_FLAGS),$(CFLAGS)))
Isn't this dangerous? CLANG_CROSS_FLAGS are treated as space-separated array of values, so if you have something like '-I whatever' it will actually filter out unrelated -Is from CFLAGS, no? I'd rather subst into empty string instead, just like we do for LIBBPF_INCLUDE.
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 $@ -- 2.33.1
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 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)
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 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 52383fe8ba42..6c678509e949 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]) $(call msg,MOD,,$@) @@ -213,7 +213,7 @@ 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/ \ @@ -244,7 +244,7 @@ $(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 @@ -542,7 +542,7 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \ $(OUTPUT)/bench_ringbufs.o \ $(OUTPUT)/bench_bloom_filter_map.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 \
On Mon, 22 Nov 2021 at 19:23, Jean-Philippe Brucker jean-philippe@linaro.org wrote:
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.
The set looks good to me. I checked that the tools are still building (without cross-compiling). I currently have issues building the selftests on my setup, but they don't appear to be related to this patchset.
Acked-by: Quentin Monnet quentin@isovalent.com
Note that on bpf-next, patch 5 (runqslower) has a conflict with be79505caf3f ("tools/runqslower: Install libbpf headers when building").
Did you consider enabling cross-compiling for the BPF samples too? I'm asking because the build system is pretty similar to the BPF tools.
Thanks, Quentin
On 11/26/21 9:36 PM, Quentin Monnet wrote:
On Mon, 22 Nov 2021 at 19:23, Jean-Philippe Brucker jean-philippe@linaro.org wrote:
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.
The set looks good to me. I checked that the tools are still building (without cross-compiling). I currently have issues building the selftests on my setup, but they don't appear to be related to this patchset.
Acked-by: Quentin Monnet quentin@isovalent.com
Note that on bpf-next, patch 5 (runqslower) has a conflict with be79505caf3f ("tools/runqslower: Install libbpf headers when building").
Jean-Philippe, please do one rebase spin for addressing the above.
Thanks, Daniel
On Fri, Nov 26, 2021 at 08:36:24PM +0000, Quentin Monnet wrote:
On Mon, 22 Nov 2021 at 19:23, Jean-Philippe Brucker jean-philippe@linaro.org wrote:
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.
The set looks good to me. I checked that the tools are still building (without cross-compiling). I currently have issues building the selftests on my setup, but they don't appear to be related to this patchset.
Acked-by: Quentin Monnet quentin@isovalent.com
Note that on bpf-next, patch 5 (runqslower) has a conflict with be79505caf3f ("tools/runqslower: Install libbpf headers when building").
Ah right, I have the series on top of "tools/runqslower: Fix cross-build", which is in bpf/master but not yet in bpf-next. I'll wait for the branches to synchronize before resending, since the patches conflict either way.
Did you consider enabling cross-compiling for the BPF samples too? I'm asking because the build system is pretty similar to the BPF tools.
Right, the problems seem similar to the selftests (need to build two libbpfs, pass $(HOSTCC) etc). Samples aren't as crucial as tools but I can look into it when I find a bit of time.
Thanks, Jean
linux-kselftest-mirror@lists.linaro.org
-
Andrii Nakryiko -
Daniel Borkmann -
Jean-Philippe Brucker -
Quentin Monnet