Files
openwrt/include/bpf.mk
T
Paul Spooren 6c03a267b0 build: bpf: remap build paths in BTF line info
CompileBPF calls clang with -g but without any prefix map. Stripping debug info
keeps .BTF and .BTF.ext, since libbpf needs them, and their line info carries
the absolute path of each source file. This makes BPF objects like qosify-bpf.o
depend on the build directory and breaks reproducibility:

  -/builder/shared-workdir/build/build_dir/.../qosify-bpf.c
  +/tmp/rebuilderd-openwrt.juCsuQ/src/build_dir/.../qosify-bpf.c

IREMAP_CFLAGS is not enough here: without CONFIG_REPRODUCIBLE_DEBUG_INFO it
only sets -fmacro-prefix-map, which leaves the line info alone, and it is empty
for external toolchains, which have no say over the host clang.  Unlike regular
debug info, BTF ships with the package, so always pass -ffile-prefix-map for
the build and staging directories.

Add an fremap helper next to iremap for that, and let IREMAP_STAGING_DIR and
CompileBPF share the map of the staging directory, so they cannot drift apart.

Link: https://github.com/openwrt/openwrt/pull/25359
Signed-off-by: Paul Spooren <mail@aparcar.org>
2026-09-25 09:13:47 +02:00

101 lines
3.7 KiB
Makefile

BPF_DEPENDS := @HAS_BPF_TOOLCHAIN +@NEED_BPF_TOOLCHAIN
CLANG_MIN_VER:=12
ifneq ($(CONFIG_USE_LLVM_HOST),)
find-llvm-tool=$(firstword $(shell PATH='$(BPF_PATH)' command -v $(1) || echo '$(firstword $(1))-not-found'))
BPF_TOOLCHAIN_HOST_PATH:=$(call qstrip,$(CONFIG_BPF_TOOLCHAIN_HOST_PATH))
ifneq ($(BPF_TOOLCHAIN_HOST_PATH),)
BPF_PATH:=$(BPF_TOOLCHAIN_HOST_PATH)/bin:$(PATH)
else
BPF_PATH:=$(PATH)
endif
CLANG:=$(call find-llvm-tool,clang clang-13 clang-12)
LLVM_VER:=$(subst clang,,$(notdir $(CLANG)))
BPF_PATH:=$(dir $(CLANG)):$(BPF_PATH)
LLVM_LLC:=$(call find-llvm-tool,llc$(LLVM_VER))
LLVM_DIS:=$(call find-llvm-tool,llvm-dis$(LLVM_VER))
LLVM_OPT:=$(call find-llvm-tool,opt$(LLVM_VER))
LLVM_STRIP:=$(call find-llvm-tool,llvm-strip$(LLVM_VER))
else
LLVM_PATH:=/invalid
ifneq ($(CONFIG_USE_LLVM_PREBUILT),)
LLVM_PATH:=$(TOPDIR)/llvm-bpf/bin
endif
ifneq ($(CONFIG_USE_LLVM_BUILD),)
LLVM_PATH:=$(STAGING_DIR_HOST)/llvm-bpf/bin
endif
CLANG:=$(LLVM_PATH)/clang
LLVM_LLC:=$(LLVM_PATH)/llc
LLVM_DIS:=$(LLVM_PATH)/llvm-dis
LLVM_OPT:=$(LLVM_PATH)/opt
LLVM_STRIP:=$(LLVM_PATH)/llvm-strip
endif
BPF_KARCH:=mips
BPF_ARCH:=mips$(if $(CONFIG_ARCH_64BIT),64)$(if $(CONFIG_BIG_ENDIAN),,el)
BPF_TARGET:=bpf$(if $(CONFIG_BIG_ENDIAN),eb,el)
BPF_HEADERS_DIR:=$(STAGING_DIR)/bpf-headers
BPF_KERNEL_INCLUDE := \
-nostdinc -isystem $(TOOLCHAIN_ROOT_DIR)/lib/gcc/*/*/include \
$(patsubst %,-isystem%,$(TOOLCHAIN_INC_DIRS)) \
-I$(BPF_HEADERS_DIR)/arch/$(BPF_KARCH)/include \
-I$(BPF_HEADERS_DIR)/arch/$(BPF_KARCH)/include/asm/mach-generic \
-I$(BPF_HEADERS_DIR)/arch/$(BPF_KARCH)/include/generated \
-I$(BPF_HEADERS_DIR)/include \
-I$(BPF_HEADERS_DIR)/arch/$(BPF_KARCH)/include/uapi \
-I$(BPF_HEADERS_DIR)/arch/$(BPF_KARCH)/include/generated/uapi \
-I$(BPF_HEADERS_DIR)/include/uapi \
-I$(BPF_HEADERS_DIR)/include/generated/uapi \
-I$(BPF_HEADERS_DIR)/tools/lib \
-I$(BPF_HEADERS_DIR)/tools/testing/selftests \
-I$(BPF_HEADERS_DIR)/samples/bpf \
-include linux/kconfig.h -include asm_goto_workaround.h
BPF_CFLAGS := \
$(BPF_KERNEL_INCLUDE) -I$(PKG_BUILD_DIR) \
-D__KERNEL__ -D__BPF_TRACING__ -DCONFIG_GENERIC_CSUM \
-D__TARGET_ARCH_${BPF_KARCH} \
-m$(if $(CONFIG_BIG_ENDIAN),big,little)-endian \
-fno-stack-protector -Wall \
-Wno-unused-value -Wno-pointer-sign \
-Wno-compare-distinct-pointer-types \
-Wno-gnu-variable-sized-type-not-at-end \
-Wno-address-of-packed-member -Wno-tautological-compare \
-Wno-unknown-warning-option \
-fno-asynchronous-unwind-tables \
-Wno-uninitialized -Wno-unused-variable \
-Wno-unused-label \
-O2 -emit-llvm -Xclang -disable-llvm-passes
BPF_IREMAP_CFLAGS := \
$(call fremap,$(PKG_BUILD_DIR),$(notdir $(PKG_BUILD_DIR))) \
$(call remap_staging_dir,fremap)
ifneq ($(CONFIG_HAS_BPF_TOOLCHAIN),)
ifeq ($(DUMP)$(filter download refresh,$(MAKECMDGOALS)),)
CLANG_VER:=$(shell $(CLANG) --target=$(BPF_TARGET) -dM -E - < /dev/null | grep __clang_major__ | cut -d' ' -f3)
CLANG_VER_VALID:=$(shell [ "$(CLANG_VER)" -ge "$(CLANG_MIN_VER)" ] && echo 1 )
ifeq ($(CLANG_VER_VALID),)
$(error ERROR: LLVM/clang version too old. Minimum required: $(CLANG_MIN_VER), found: $(CLANG_VER))
endif
endif
endif
define CompileBPF
$(CLANG) -g -target $(BPF_ARCH)-linux-gnu $(BPF_CFLAGS) $(BPF_IREMAP_CFLAGS) $(2) \
-c $(1) -o $(patsubst %.c,%.bc,$(1))
$(LLVM_OPT) -O2 -mtriple=$(BPF_TARGET) < $(patsubst %.c,%.bc,$(1)) > $(patsubst %.c,%.opt,$(1))
$(LLVM_DIS) < $(patsubst %.c,%.opt,$(1)) > $(patsubst %.c,%.S,$(1))
$(LLVM_LLC) -march=$(BPF_TARGET) -mcpu=v3 -filetype=obj -o $(patsubst %.c,%.o,$(1)) < $(patsubst %.c,%.S,$(1))
$(CP) $(patsubst %.c,%.o,$(1)) $(patsubst %.c,%.debug.o,$(1))
$(LLVM_STRIP) --strip-debug $(patsubst %.c,%.o,$(1))
endef