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Merge branch 'tools/bpf: Enable cross-building with clang'

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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>
This commit is contained in:
Andrii Nakryiko 2021-12-16 12:15:05 -08:00
commit 1a6369ba62
6 changed files with 28 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
tools/bpf/bpftool/Makefile
View File

@ -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 $@

1
tools/bpf/resolve_btfids/Makefile
View File

@ -19,6 +19,7 @@ CC = $(HOSTCC)
LD = $(HOSTLD)
ARCH = $(HOSTARCH)
RM ?= rm
CROSS_COMPILE =
OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/

4
tools/bpf/runqslower/Makefile
View File

@ -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)

3
tools/lib/bpf/Makefile
View File

@ -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

13
tools/scripts/Makefile.include
View File

@ -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

8
tools/testing/selftests/bpf/Makefile
View File

@ -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 \