scripts/Makefile.lib - linux - Git at Google

 # SPDX-License-Identifier: GPL-2.0
 # Backward compatibility
 asflags-y  += $(EXTRA_AFLAGS)
 ccflags-y  += $(EXTRA_CFLAGS)
 cppflags-y += $(EXTRA_CPPFLAGS)
 ldflags-y  += $(EXTRA_LDFLAGS)

 # flags that take effect in current and sub directories
 KBUILD_AFLAGS += $(subdir-asflags-y)
 KBUILD_CFLAGS += $(subdir-ccflags-y)

 # Figure out what we need to build from the various variables
 # ===========================================================================

 # When an object is listed to be built compiled-in and modular,
 # only build the compiled-in version
 obj-m := $(filter-out $(obj-y),$(obj-m))

 # Libraries are always collected in one lib file.
 # Filter out objects already built-in
 lib-y := $(filter-out $(obj-y), $(sort $(lib-y) $(lib-m)))

 # Subdirectories we need to descend into
 subdir-ym := $(sort $(subdir-y) $(subdir-m) \
 			$(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m))))

 # Handle objects in subdirs:
 # - If we encounter foo/ in $(obj-y), replace it by foo/built-in.a and
 #   foo/modules.order
 # - If we encounter foo/ in $(obj-m), replace it by foo/modules.order
 #
 # Generate modules.order to determine modorder. Unfortunately, we don't have
 # information about ordering between -y and -m subdirs. Just put -y's first.

 ifdef need-modorder
 obj-m := $(patsubst %/,%/modules.order, $(filter %/, $(obj-y)) $(obj-m))
 else
 obj-m := $(filter-out %/, $(obj-m))
 endif

 ifdef need-builtin
 obj-y		:= $(patsubst %/, %/built-in.a, $(obj-y))
 else
 obj-y		:= $(filter-out %/, $(obj-y))
 endif

 # Expand $(foo-objs) $(foo-y) etc. by replacing their individuals
 suffix-search = $(strip $(foreach s, $3, $($(1:%$(strip $2)=%$s))))
 # List composite targets that are constructed by combining other targets
 multi-search = $(sort $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $m)))
 # List primitive targets that are compiled from source files
 real-search = $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $(call suffix-search, $m, $2, $3), $m))

 # If $(foo-objs), $(foo-y), $(foo-m), or $(foo-) exists, foo.o is a composite object
 multi-obj-y := $(call multi-search, $(obj-y), .o, -objs -y)
 multi-obj-m := $(call multi-search, $(obj-m), .o, -objs -y -m)
 multi-obj-ym := $(multi-obj-y) $(multi-obj-m)

 # Replace multi-part objects by their individual parts,
 # including built-in.a from subdirectories
 real-obj-y := $(call real-search, $(obj-y), .o, -objs -y)
 real-obj-m := $(call real-search, $(obj-m), .o, -objs -y -m)

 always-y += $(always-m)

 # hostprogs-always-y += foo
 # ... is a shorthand for
 # hostprogs += foo
 # always-y  += foo
 hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)
 always-y += $(hostprogs-always-y) $(hostprogs-always-m)

 # userprogs-always-y is likewise.
 userprogs += $(userprogs-always-y) $(userprogs-always-m)
 always-y += $(userprogs-always-y) $(userprogs-always-m)

 # DTB
 # If CONFIG_OF_ALL_DTBS is enabled, all DT blobs are built
 dtb-$(CONFIG_OF_ALL_DTBS)       += $(dtb-)

 # Composite DTB (i.e. DTB constructed by overlay)
 multi-dtb-y := $(call multi-search, $(dtb-y), .dtb, -dtbs)
 # Primitive DTB compiled from *.dts
 real-dtb-y := $(call real-search, $(dtb-y), .dtb, -dtbs)
 # Base DTB that overlay is applied onto (each first word of $(*-dtbs) expansion)
 base-dtb-y := $(foreach m, $(multi-dtb-y), $(firstword $(call suffix-search, $m, .dtb, -dtbs)))

 always-y			+= $(dtb-y)

 ifneq ($(CHECK_DTBS),)
 always-y += $(patsubst %.dtb,%.dt.yaml, $(real-dtb-y))
 always-y += $(patsubst %.dtbo,%.dt.yaml, $(real-dtb-y))
 endif

 # Add subdir path

 extra-y		:= $(addprefix $(obj)/,$(extra-y))
 always-y	:= $(addprefix $(obj)/,$(always-y))
 targets		:= $(addprefix $(obj)/,$(targets))
 obj-m		:= $(addprefix $(obj)/,$(obj-m))
 lib-y		:= $(addprefix $(obj)/,$(lib-y))
 real-obj-y	:= $(addprefix $(obj)/,$(real-obj-y))
 real-obj-m	:= $(addprefix $(obj)/,$(real-obj-m))
 multi-obj-m	:= $(addprefix $(obj)/, $(multi-obj-m))
 multi-dtb-y	:= $(addprefix $(obj)/, $(multi-dtb-y))
 real-dtb-y	:= $(addprefix $(obj)/, $(real-dtb-y))
 subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))

 # Finds the multi-part object the current object will be linked into.
 # If the object belongs to two or more multi-part objects, list them all.
 modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
 		$(if $(filter $*.o, $(call suffix-search, $m, .o, -objs -y -m)),$(m:.o=))))

 __modname = $(if $(modname-multi),$(modname-multi),$(basetarget))

 modname = $(subst $(space),:,$(__modname))
 modfile = $(addprefix $(obj)/,$(__modname))

 # target with $(obj)/ and its suffix stripped
 target-stem = $(basename $(patsubst $(obj)/%,%,$@))

 # These flags are needed for modversions and compiling, so we define them here
 # $(modname_flags) defines KBUILD_MODNAME as the name of the module it will
 # end up in (or would, if it gets compiled in)
 name-fix-token = $(subst $(comma),_,$(subst -,_,$1))
 name-fix = $(call stringify,$(call name-fix-token,$1))
 basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
 modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
 		 -D__KBUILD_MODNAME=kmod_$(call name-fix-token,$(modname))
 modfile_flags  = -DKBUILD_MODFILE=$(call stringify,$(modfile))

 _c_flags       = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
                      $(filter-out $(ccflags-remove-y), \
                          $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(ccflags-y)) \
                      $(CFLAGS_$(target-stem).o))
 _a_flags       = $(filter-out $(AFLAGS_REMOVE_$(target-stem).o), \
                      $(filter-out $(asflags-remove-y), \
                          $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(asflags-y)) \
                      $(AFLAGS_$(target-stem).o))
 _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)

 #
 # Enable gcov profiling flags for a file, directory or for all files depending
 # on variables GCOV_PROFILE_obj.o, GCOV_PROFILE and CONFIG_GCOV_PROFILE_ALL
 # (in this order)
 #
 ifeq ($(CONFIG_GCOV_KERNEL),y)
 _c_flags += $(if $(patsubst n%,, \
 		$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
 		$(CFLAGS_GCOV))
 endif

 #
 # Enable address sanitizer flags for kernel except some files or directories
 # we don't want to check (depends on variables KASAN_SANITIZE_obj.o, KASAN_SANITIZE)
 #
 ifeq ($(CONFIG_KASAN),y)
 ifneq ($(CONFIG_KASAN_HW_TAGS),y)
 _c_flags += $(if $(patsubst n%,, \
 		$(KASAN_SANITIZE_$(basetarget).o)$(KASAN_SANITIZE)y), \
 		$(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
 endif
 endif

 ifeq ($(CONFIG_UBSAN),y)
 _c_flags += $(if $(patsubst n%,, \
 		$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)), \
 		$(CFLAGS_UBSAN))
 endif

 ifeq ($(CONFIG_KCOV),y)
 _c_flags += $(if $(patsubst n%,, \
 	$(KCOV_INSTRUMENT_$(basetarget).o)$(KCOV_INSTRUMENT)$(CONFIG_KCOV_INSTRUMENT_ALL)), \
 	$(CFLAGS_KCOV))
 endif

 #
 # Enable KCSAN flags except some files or directories we don't want to check
 # (depends on variables KCSAN_SANITIZE_obj.o, KCSAN_SANITIZE)
 #
 ifeq ($(CONFIG_KCSAN),y)
 _c_flags += $(if $(patsubst n%,, \
 	$(KCSAN_SANITIZE_$(basetarget).o)$(KCSAN_SANITIZE)y), \
 	$(CFLAGS_KCSAN))
 endif

 # $(srctree)/$(src) for including checkin headers from generated source files
 # $(objtree)/$(obj) for including generated headers from checkin source files
 ifeq ($(KBUILD_EXTMOD),)
 ifdef building_out_of_srctree
 _c_flags   += -I $(srctree)/$(src) -I $(objtree)/$(obj)
 _a_flags   += -I $(srctree)/$(src) -I $(objtree)/$(obj)
 _cpp_flags += -I $(srctree)/$(src) -I $(objtree)/$(obj)
 endif
 endif

 part-of-module = $(if $(filter $(basename $@).o, $(real-obj-m)),y)
 quiet_modtag = $(if $(part-of-module),[M],   )

 modkern_cflags =                                          \
 	$(if $(part-of-module),                           \
 		$(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
 		$(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL) $(modfile_flags))

 modkern_aflags = $(if $(part-of-module),				\
 			$(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE),	\
 			$(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL))

 c_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 -include $(srctree)/include/linux/compiler_types.h       \
 		 $(_c_flags) $(modkern_cflags)                           \
 		 $(basename_flags) $(modname_flags)

 a_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(_a_flags) $(modkern_aflags)

 cpp_flags      = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(_cpp_flags)

 ld_flags       = $(KBUILD_LDFLAGS) $(ldflags-y) $(LDFLAGS_$(@F))

 # ANDROID: Allow DTC_INCLUDE to be set by the BUILD_CONFIG. This allows one to
 # compile an out-of-tree device tree.
 DTC_INCLUDE    += $(srctree)/scripts/dtc/include-prefixes

 dtc_cpp_flags  = -Wp,-MMD,$(depfile).pre.tmp -nostdinc                    \
 		 $(addprefix -I,$(DTC_INCLUDE))                          \
 		 -undef -D__DTS__

 ifeq ($(CONFIG_LTO_CLANG),y)
 # With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we
 # need to run LTO to compile them into native code (.lto.o) before further
 # processing.
 mod-prelink-ext := .lto
 endif

 # Useful for describing the dependency of composite objects
 # Usage:
 #   $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
 define multi_depend
 $(foreach m, $1, \
 	$(eval $m: \
 	$(addprefix $(obj)/, $(call suffix-search, $(patsubst $(obj)/%,%,$m), $2, $3))))
 endef

 quiet_cmd_copy = COPY    $@
       cmd_copy = cp $< $@

 # Shipped files
 # ===========================================================================
 # 'cp' preserves permissions. If you use it to copy a file in read-only srctree,
 # the copy would be read-only as well, leading to an error when executing the
 # rule next time. Use 'cat' instead in order to generate a writable file.

 quiet_cmd_shipped = SHIPPED $@
 cmd_shipped = cat $< > $@

 $(obj)/%: $(src)/%_shipped
 	$(call cmd,shipped)

 # Commands useful for building a boot image
 # ===========================================================================
 #
 #	Use as following:
 #
 #	target: source(s) FORCE
 #		$(if_changed,ld/objcopy/gzip)
 #
 #	and add target to 'targets' so that we know we have to
 #	read in the saved command line

 # Linking
 # ---------------------------------------------------------------------------

 quiet_cmd_ld = LD      $@
       cmd_ld = $(LD) $(ld_flags) $(real-prereqs) -o $@

 # Archive
 # ---------------------------------------------------------------------------

 quiet_cmd_ar = AR      $@
       cmd_ar = rm -f $@; $(AR) cDPrsT $@ $(real-prereqs)

 # Objcopy
 # ---------------------------------------------------------------------------

 quiet_cmd_objcopy = OBJCOPY $@
 cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@

 # Gzip
 # ---------------------------------------------------------------------------

 quiet_cmd_gzip = GZIP    $@
       cmd_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 > $@

 # DTC
 # ---------------------------------------------------------------------------
 DTC ?= $(objtree)/scripts/dtc/dtc
 DTC_FLAGS += -Wno-interrupt_provider

 # Disable noisy checks by default
 ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
 DTC_FLAGS += -Wno-unit_address_vs_reg \
 	-Wno-unit_address_format \
 	-Wno-avoid_unnecessary_addr_size \
 	-Wno-alias_paths \
 	-Wno-graph_child_address \
 	-Wno-simple_bus_reg \
 	-Wno-unique_unit_address
 endif

 ifneq ($(findstring 2,$(KBUILD_EXTRA_WARN)),)
 DTC_FLAGS += -Wnode_name_chars_strict \
 	-Wproperty_name_chars_strict \
 	-Winterrupt_provider
 endif

 DTC_FLAGS += $(DTC_FLAGS_$(basetarget))

 # Set -@ if the target is a base DTB that overlay is applied onto
 DTC_FLAGS += $(if $(filter $(patsubst $(obj)/%,%,$@), $(base-dtb-y)), -@)

 # Generate an assembly file to wrap the output of the device tree compiler
 quiet_cmd_dt_S_dtb= DTB     $@
 cmd_dt_S_dtb=						\
 {							\
 	echo '\#include <asm-generic/vmlinux.lds.h>'; 	\
 	echo '.section .dtb.init.rodata,"a"';		\
 	echo '.balign STRUCT_ALIGNMENT';		\
 	echo '.global __dtb_$(subst -,_,$(*F))_begin';	\
 	echo '__dtb_$(subst -,_,$(*F))_begin:';		\
 	echo '.incbin "$<" ';				\
 	echo '__dtb_$(subst -,_,$(*F))_end:';		\
 	echo '.global __dtb_$(subst -,_,$(*F))_end';	\
 	echo '.balign STRUCT_ALIGNMENT'; 		\
 } > $@

 $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
 	$(call if_changed,dt_S_dtb)

 quiet_cmd_dtc = DTC     $@
 cmd_dtc = $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
 	$(DTC) -o $@ -b 0 \
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)

 $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
 	$(call if_changed_dep,dtc)

 $(obj)/%.dtbo: $(src)/%.dts $(DTC) FORCE
 	$(call if_changed_dep,dtc)

 quiet_cmd_fdtoverlay = DTOVL   $@
       cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $(real-prereqs)

 $(multi-dtb-y): FORCE
 	$(call if_changed,fdtoverlay)
 $(call multi_depend, $(multi-dtb-y), .dtb, -dtbs)

 DT_CHECKER ?= dt-validate
 DT_CHECKER_FLAGS ?= $(if $(DT_SCHEMA_FILES),,-m)
 DT_BINDING_DIR := Documentation/devicetree/bindings
 # DT_TMP_SCHEMA may be overridden from Documentation/devicetree/bindings/Makefile
 DT_TMP_SCHEMA ?= $(objtree)/$(DT_BINDING_DIR)/processed-schema.json

 quiet_cmd_dtb_check =	CHECK   $@
       cmd_dtb_check =	$(DT_CHECKER) $(DT_CHECKER_FLAGS) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@

 define rule_dtc
 	$(call cmd_and_fixdep,dtc)
 	$(call cmd,dtb_check)
 endef

 $(obj)/%.dt.yaml: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
 	$(call if_changed_rule,dtc)

 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)

 # Bzip2
 # ---------------------------------------------------------------------------

 # Bzip2 and LZMA do not include size in file... so we have to fake that;
 # append the size as a 32-bit littleendian number as gzip does.
 size_append = printf $(shell						\
 dec_size=0;								\
 for F in $(real-prereqs); do					\
 	fsize=$$($(CONFIG_SHELL) $(srctree)/scripts/file-size.sh $$F);	\
 	dec_size=$$(expr $$dec_size + $$fsize);				\
 done;									\
 printf "%08x\n" $$dec_size |						\
 	sed 's/\(..\)/\1 /g' | {					\
 		read ch0 ch1 ch2 ch3;					\
 		for ch in $$ch3 $$ch2 $$ch1 $$ch0; do			\
 			printf '%s%03o' '\\' $$((0x$$ch)); 		\
 		done;							\
 	}								\
 )

 quiet_cmd_bzip2 = BZIP2   $@
       cmd_bzip2 = cat $(real-prereqs) | $(KBZIP2) -9 > $@

 quiet_cmd_bzip2_with_size = BZIP2   $@
       cmd_bzip2_with_size = { cat $(real-prereqs) | $(KBZIP2) -9; $(size_append); } > $@

 # Lzma
 # ---------------------------------------------------------------------------

 quiet_cmd_lzma = LZMA    $@
       cmd_lzma = cat $(real-prereqs) | $(LZMA) -9 > $@

 quiet_cmd_lzma_with_size = LZMA    $@
       cmd_lzma_with_size = { cat $(real-prereqs) | $(LZMA) -9; $(size_append); } > $@

 quiet_cmd_lzo = LZO     $@
       cmd_lzo = cat $(real-prereqs) | $(KLZOP) -9 > $@

 quiet_cmd_lzo_with_size = LZO     $@
       cmd_lzo_with_size = { cat $(real-prereqs) | $(KLZOP) -9; $(size_append); } > $@

 quiet_cmd_lz4 = LZ4     $@
       cmd_lz4 = cat $(real-prereqs) | $(LZ4) -l -12 --favor-decSpeed stdin stdout > $@

 quiet_cmd_lz4_with_size = LZ4     $@
       cmd_lz4_with_size = { cat $(real-prereqs) | $(LZ4) -l -12 --favor-decSpeed stdin stdout; \
                   $(size_append); } > $@

 # U-Boot mkimage
 # ---------------------------------------------------------------------------

 MKIMAGE := $(srctree)/scripts/mkuboot.sh

 # SRCARCH just happens to match slightly more than ARCH (on sparc), so reduces
 # the number of overrides in arch makefiles
 UIMAGE_ARCH ?= $(SRCARCH)
 UIMAGE_COMPRESSION ?= $(if $(2),$(2),none)
 UIMAGE_OPTS-y ?=
 UIMAGE_TYPE ?= kernel
 UIMAGE_LOADADDR ?= arch_must_set_this
 UIMAGE_ENTRYADDR ?= $(UIMAGE_LOADADDR)
 UIMAGE_NAME ?= 'Linux-$(KERNELRELEASE)'

 quiet_cmd_uimage = UIMAGE  $@
       cmd_uimage = $(BASH) $(MKIMAGE) -A $(UIMAGE_ARCH) -O linux \
 			-C $(UIMAGE_COMPRESSION) $(UIMAGE_OPTS-y) \
 			-T $(UIMAGE_TYPE) \
 			-a $(UIMAGE_LOADADDR) -e $(UIMAGE_ENTRYADDR) \
 			-n $(UIMAGE_NAME) -d $< $@

 # XZ
 # ---------------------------------------------------------------------------
 # Use xzkern to compress the kernel image and xzmisc to compress other things.
 #
 # xzkern uses a big LZMA2 dictionary since it doesn't increase memory usage
 # of the kernel decompressor. A BCJ filter is used if it is available for
 # the target architecture. xzkern also appends uncompressed size of the data
 # using size_append. The .xz format has the size information available at
 # the end of the file too, but it's in more complex format and it's good to
 # avoid changing the part of the boot code that reads the uncompressed size.
 # Note that the bytes added by size_append will make the xz tool think that
 # the file is corrupt. This is expected.
 #
 # xzmisc doesn't use size_append, so it can be used to create normal .xz
 # files. xzmisc uses smaller LZMA2 dictionary than xzkern, because a very
 # big dictionary would increase the memory usage too much in the multi-call
 # decompression mode. A BCJ filter isn't used either.
 quiet_cmd_xzkern = XZKERN  $@
       cmd_xzkern = cat $(real-prereqs) | sh $(srctree)/scripts/xz_wrap.sh > $@

 quiet_cmd_xzkern_with_size = XZKERN  $@
       cmd_xzkern_with_size = { cat $(real-prereqs) | sh $(srctree)/scripts/xz_wrap.sh; \
                      $(size_append); } > $@

 quiet_cmd_xzmisc = XZMISC  $@
       cmd_xzmisc = cat $(real-prereqs) | $(XZ) --check=crc32 --lzma2=dict=1MiB > $@

 # ZSTD
 # ---------------------------------------------------------------------------
 # Appends the uncompressed size of the data using size_append. The .zst
 # format has the size information available at the beginning of the file too,
 # but it's in a more complex format and it's good to avoid changing the part
 # of the boot code that reads the uncompressed size.
 #
 # Note that the bytes added by size_append will make the zstd tool think that
 # the file is corrupt. This is expected.
 #
 # zstd uses a maximum window size of 8 MB. zstd22 uses a maximum window size of
 # 128 MB. zstd22 is used for kernel compression because it is decompressed in a
 # single pass, so zstd doesn't need to allocate a window buffer. When streaming
 # decompression is used, like initramfs decompression, zstd22 should likely not
 # be used because it would require zstd to allocate a 128 MB buffer.

 quiet_cmd_zstd = ZSTD    $@
       cmd_zstd = { cat $(real-prereqs) | $(ZSTD) -19; $(size_append); } > $@

 quiet_cmd_zstd22 = ZSTD22  $@
       cmd_zstd22 = cat $(real-prereqs) | $(ZSTD) -22 --ultra > $@

 quiet_cmd_zstd22_with_size = ZSTD22  $@
       cmd_zstd22_with_size = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@

 # ASM offsets
 # ---------------------------------------------------------------------------

 # Default sed regexp - multiline due to syntax constraints
 #
 # Use [:space:] because LLVM's integrated assembler inserts <tab> around
 # the .ascii directive whereas GCC keeps the <space> as-is.
 define sed-offsets
 	's:^[[:space:]]*\.ascii[[:space:]]*"\(.*\)".*:\1:; \
 	/^->/{s:->#\(.*\):/* \1 */:; \
 	s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
 	s:->::; p;}'
 endef

 # Use filechk to avoid rebuilds when a header changes, but the resulting file
 # does not
 define filechk_offsets
 	 echo "#ifndef $2"; \
 	 echo "#define $2"; \
 	 echo "/*"; \
 	 echo " * DO NOT MODIFY."; \
 	 echo " *"; \
 	 echo " * This file was generated by Kbuild"; \
 	 echo " */"; \
 	 echo ""; \
 	 sed -ne $(sed-offsets) < $<; \
 	 echo ""; \
 	 echo "#endif"
 endef
	# SPDX-License-Identifier: GPL-2.0
	# Backward compatibility
	asflags-y += $(EXTRA_AFLAGS)
	ccflags-y += $(EXTRA_CFLAGS)
	cppflags-y += $(EXTRA_CPPFLAGS)
	ldflags-y += $(EXTRA_LDFLAGS)

	# flags that take effect in current and sub directories
	KBUILD_AFLAGS += $(subdir-asflags-y)
	KBUILD_CFLAGS += $(subdir-ccflags-y)

	# Figure out what we need to build from the various variables
	# ===========================================================================

	# When an object is listed to be built compiled-in and modular,
	# only build the compiled-in version
	obj-m := $(filter-out $(obj-y),$(obj-m))

	# Libraries are always collected in one lib file.
	# Filter out objects already built-in
	lib-y := $(filter-out $(obj-y), $(sort $(lib-y) $(lib-m)))

	# Subdirectories we need to descend into
	subdir-ym := $(sort $(subdir-y) $(subdir-m) \
	$(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m))))

	# Handle objects in subdirs:
	# - If we encounter foo/ in $(obj-y), replace it by foo/built-in.a and
	# foo/modules.order
	# - If we encounter foo/ in $(obj-m), replace it by foo/modules.order
	#
	# Generate modules.order to determine modorder. Unfortunately, we don't have
	# information about ordering between -y and -m subdirs. Just put -y's first.

	ifdef need-modorder
	obj-m := $(patsubst %/,%/modules.order, $(filter %/, $(obj-y)) $(obj-m))
	else
	obj-m := $(filter-out %/, $(obj-m))
	endif

	ifdef need-builtin
	obj-y := $(patsubst %/, %/built-in.a, $(obj-y))
	else
	obj-y := $(filter-out %/, $(obj-y))
	endif

	# Expand $(foo-objs) $(foo-y) etc. by replacing their individuals
	suffix-search = $(strip $(foreach s, $3, $($(1:%$(strip $2)=%$s))))
	# List composite targets that are constructed by combining other targets
	multi-search = $(sort $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $m)))
	# List primitive targets that are compiled from source files
	real-search = $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $(call suffix-search, $m, $2, $3), $m))

	# If $(foo-objs), $(foo-y), $(foo-m), or $(foo-) exists, foo.o is a composite object
	multi-obj-y := $(call multi-search, $(obj-y), .o, -objs -y)
	multi-obj-m := $(call multi-search, $(obj-m), .o, -objs -y -m)
	multi-obj-ym := $(multi-obj-y) $(multi-obj-m)

	# Replace multi-part objects by their individual parts,
	# including built-in.a from subdirectories
	real-obj-y := $(call real-search, $(obj-y), .o, -objs -y)
	real-obj-m := $(call real-search, $(obj-m), .o, -objs -y -m)

	always-y += $(always-m)

	# hostprogs-always-y += foo
	# ... is a shorthand for
	# hostprogs += foo
	# always-y += foo
	hostprogs += $(hostprogs-always-y) $(hostprogs-always-m)
	always-y += $(hostprogs-always-y) $(hostprogs-always-m)

	# userprogs-always-y is likewise.
	userprogs += $(userprogs-always-y) $(userprogs-always-m)
	always-y += $(userprogs-always-y) $(userprogs-always-m)

	# DTB
	# If CONFIG_OF_ALL_DTBS is enabled, all DT blobs are built
	dtb-$(CONFIG_OF_ALL_DTBS) += $(dtb-)

	# Composite DTB (i.e. DTB constructed by overlay)
	multi-dtb-y := $(call multi-search, $(dtb-y), .dtb, -dtbs)
	# Primitive DTB compiled from *.dts
	real-dtb-y := $(call real-search, $(dtb-y), .dtb, -dtbs)
	# Base DTB that overlay is applied onto (each first word of $(*-dtbs) expansion)
	base-dtb-y := $(foreach m, $(multi-dtb-y), $(firstword $(call suffix-search, $m, .dtb, -dtbs)))

	always-y += $(dtb-y)

	ifneq ($(CHECK_DTBS),)
	always-y += $(patsubst %.dtb,%.dt.yaml, $(real-dtb-y))
	always-y += $(patsubst %.dtbo,%.dt.yaml, $(real-dtb-y))
	endif

	# Add subdir path

	extra-y := $(addprefix $(obj)/,$(extra-y))
	always-y := $(addprefix $(obj)/,$(always-y))
	targets := $(addprefix $(obj)/,$(targets))
	obj-m := $(addprefix $(obj)/,$(obj-m))
	lib-y := $(addprefix $(obj)/,$(lib-y))
	real-obj-y := $(addprefix $(obj)/,$(real-obj-y))
	real-obj-m := $(addprefix $(obj)/,$(real-obj-m))
	multi-obj-m := $(addprefix $(obj)/, $(multi-obj-m))
	multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y))
	real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y))
	subdir-ym := $(addprefix $(obj)/,$(subdir-ym))

	# Finds the multi-part object the current object will be linked into.
	# If the object belongs to two or more multi-part objects, list them all.
	modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
	$(if $(filter $*.o, $(call suffix-search, $m, .o, -objs -y -m)),$(m:.o=))))

	__modname = $(if $(modname-multi),$(modname-multi),$(basetarget))

	modname = $(subst $(space),:,$(__modname))
	modfile = $(addprefix $(obj)/,$(__modname))

	# target with $(obj)/ and its suffix stripped
	target-stem = $(basename $(patsubst $(obj)/%,%,$@))

	# These flags are needed for modversions and compiling, so we define them here
	# $(modname_flags) defines KBUILD_MODNAME as the name of the module it will
	# end up in (or would, if it gets compiled in)
	name-fix-token = $(subst $(comma),_,$(subst -,_,$1))
	name-fix = $(call stringify,$(call name-fix-token,$1))
	basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
	modname_flags = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
	-D__KBUILD_MODNAME=kmod_$(call name-fix-token,$(modname))
	modfile_flags = -DKBUILD_MODFILE=$(call stringify,$(modfile))

	_c_flags = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
	$(filter-out $(ccflags-remove-y), \
	$(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(ccflags-y)) \
	$(CFLAGS_$(target-stem).o))
	_a_flags = $(filter-out $(AFLAGS_REMOVE_$(target-stem).o), \
	$(filter-out $(asflags-remove-y), \
	$(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(asflags-y)) \
	$(AFLAGS_$(target-stem).o))
	_cpp_flags = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)

	#
	# Enable gcov profiling flags for a file, directory or for all files depending
	# on variables GCOV_PROFILE_obj.o, GCOV_PROFILE and CONFIG_GCOV_PROFILE_ALL
	# (in this order)
	#
	ifeq ($(CONFIG_GCOV_KERNEL),y)
	_c_flags += $(if $(patsubst n%,, \
	$(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
	$(CFLAGS_GCOV))
	endif

	#
	# Enable address sanitizer flags for kernel except some files or directories
	# we don't want to check (depends on variables KASAN_SANITIZE_obj.o, KASAN_SANITIZE)
	#
	ifeq ($(CONFIG_KASAN),y)
	ifneq ($(CONFIG_KASAN_HW_TAGS),y)
	_c_flags += $(if $(patsubst n%,, \
	$(KASAN_SANITIZE_$(basetarget).o)$(KASAN_SANITIZE)y), \
	$(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
	endif
	endif

	ifeq ($(CONFIG_UBSAN),y)
	_c_flags += $(if $(patsubst n%,, \
	$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)), \
	$(CFLAGS_UBSAN))
	endif

	ifeq ($(CONFIG_KCOV),y)
	_c_flags += $(if $(patsubst n%,, \
	$(KCOV_INSTRUMENT_$(basetarget).o)$(KCOV_INSTRUMENT)$(CONFIG_KCOV_INSTRUMENT_ALL)), \
	$(CFLAGS_KCOV))
	endif

	#
	# Enable KCSAN flags except some files or directories we don't want to check
	# (depends on variables KCSAN_SANITIZE_obj.o, KCSAN_SANITIZE)
	#
	ifeq ($(CONFIG_KCSAN),y)
	_c_flags += $(if $(patsubst n%,, \
	$(KCSAN_SANITIZE_$(basetarget).o)$(KCSAN_SANITIZE)y), \
	$(CFLAGS_KCSAN))
	endif

	# $(srctree)/$(src) for including checkin headers from generated source files
	# $(objtree)/$(obj) for including generated headers from checkin source files
	ifeq ($(KBUILD_EXTMOD),)
	ifdef building_out_of_srctree
	_c_flags += -I $(srctree)/$(src) -I $(objtree)/$(obj)
	_a_flags += -I $(srctree)/$(src) -I $(objtree)/$(obj)
	_cpp_flags += -I $(srctree)/$(src) -I $(objtree)/$(obj)
	endif
	endif

	part-of-module = $(if $(filter $(basename $@).o, $(real-obj-m)),y)
	quiet_modtag = $(if $(part-of-module),[M], )

	modkern_cflags = \
	$(if $(part-of-module), \
	$(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
	$(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL) $(modfile_flags))

	modkern_aflags = $(if $(part-of-module), \
	$(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE), \
	$(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL))

	c_flags = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) \
	-include $(srctree)/include/linux/compiler_types.h \
	$(_c_flags) $(modkern_cflags) \
	$(basename_flags) $(modname_flags)

	a_flags = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) \
	$(_a_flags) $(modkern_aflags)

	cpp_flags = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) \
	$(_cpp_flags)

	ld_flags = $(KBUILD_LDFLAGS) $(ldflags-y) $(LDFLAGS_$(@F))

	# ANDROID: Allow DTC_INCLUDE to be set by the BUILD_CONFIG. This allows one to
	# compile an out-of-tree device tree.
	DTC_INCLUDE += $(srctree)/scripts/dtc/include-prefixes

	dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \
	$(addprefix -I,$(DTC_INCLUDE)) \
	-undef -D__DTS__

	ifeq ($(CONFIG_LTO_CLANG),y)
	# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we
	# need to run LTO to compile them into native code (.lto.o) before further
	# processing.
	mod-prelink-ext := .lto
	endif

	# Useful for describing the dependency of composite objects
	# Usage:
	# $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
	define multi_depend
	$(foreach m, $1, \
	$(eval $m: \
	$(addprefix $(obj)/, $(call suffix-search, $(patsubst $(obj)/%,%,$m), $2, $3))))
	endef

	quiet_cmd_copy = COPY $@
	cmd_copy = cp $< $@

	# Shipped files
	# ===========================================================================
	# 'cp' preserves permissions. If you use it to copy a file in read-only srctree,
	# the copy would be read-only as well, leading to an error when executing the
	# rule next time. Use 'cat' instead in order to generate a writable file.

	quiet_cmd_shipped = SHIPPED $@
	cmd_shipped = cat $< > $@

	$(obj)/%: $(src)/%_shipped
	$(call cmd,shipped)

	# Commands useful for building a boot image
	# ===========================================================================
	#
	# Use as following:
	#
	# target: source(s) FORCE
	# $(if_changed,ld/objcopy/gzip)
	#
	# and add target to 'targets' so that we know we have to
	# read in the saved command line

	# Linking
	# ---------------------------------------------------------------------------

	quiet_cmd_ld = LD $@
	cmd_ld = $(LD) $(ld_flags) $(real-prereqs) -o $@

	# Archive
	# ---------------------------------------------------------------------------

	quiet_cmd_ar = AR $@
	cmd_ar = rm -f $@; $(AR) cDPrsT $@ $(real-prereqs)

	# Objcopy
	# ---------------------------------------------------------------------------

	quiet_cmd_objcopy = OBJCOPY $@
	cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@

	# Gzip
	# ---------------------------------------------------------------------------

	quiet_cmd_gzip = GZIP $@
	cmd_gzip = cat $(real-prereqs) \| $(KGZIP) -n -f -9 > $@

	# DTC
	# ---------------------------------------------------------------------------
	DTC ?= $(objtree)/scripts/dtc/dtc
	DTC_FLAGS += -Wno-interrupt_provider

	# Disable noisy checks by default
	ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
	DTC_FLAGS += -Wno-unit_address_vs_reg \
	-Wno-unit_address_format \
	-Wno-avoid_unnecessary_addr_size \
	-Wno-alias_paths \
	-Wno-graph_child_address \
	-Wno-simple_bus_reg \
	-Wno-unique_unit_address
	endif

	ifneq ($(findstring 2,$(KBUILD_EXTRA_WARN)),)
	DTC_FLAGS += -Wnode_name_chars_strict \
	-Wproperty_name_chars_strict \
	-Winterrupt_provider
	endif

	DTC_FLAGS += $(DTC_FLAGS_$(basetarget))

	# Set -@ if the target is a base DTB that overlay is applied onto
	DTC_FLAGS += $(if $(filter $(patsubst $(obj)/%,%,$@), $(base-dtb-y)), -@)

	# Generate an assembly file to wrap the output of the device tree compiler
	quiet_cmd_dt_S_dtb= DTB $@
	cmd_dt_S_dtb= \
	{ \
	echo '\#include <asm-generic/vmlinux.lds.h>'; \
	echo '.section .dtb.init.rodata,"a"'; \
	echo '.balign STRUCT_ALIGNMENT'; \
	echo '.global __dtb_$(subst -,_,$(*F))_begin'; \
	echo '__dtb_$(subst -,_,$(*F))_begin:'; \
	echo '.incbin "$<" '; \
	echo '__dtb_$(subst -,_,$(*F))_end:'; \
	echo '.global __dtb_$(subst -,_,$(*F))_end'; \
	echo '.balign STRUCT_ALIGNMENT'; \
	} > $@

	$(obj)/%.dtb.S: $(obj)/%.dtb FORCE
	$(call if_changed,dt_S_dtb)

	quiet_cmd_dtc = DTC $@
	cmd_dtc = $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
	$(DTC) -o $@ -b 0 \
	$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
	-d $(depfile).dtc.tmp $(dtc-tmp) ; \
	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)

	$(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
	$(call if_changed_dep,dtc)

	$(obj)/%.dtbo: $(src)/%.dts $(DTC) FORCE
	$(call if_changed_dep,dtc)

	quiet_cmd_fdtoverlay = DTOVL $@
	cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $(real-prereqs)

	$(multi-dtb-y): FORCE
	$(call if_changed,fdtoverlay)
	$(call multi_depend, $(multi-dtb-y), .dtb, -dtbs)

	DT_CHECKER ?= dt-validate
	DT_CHECKER_FLAGS ?= $(if $(DT_SCHEMA_FILES),,-m)
	DT_BINDING_DIR := Documentation/devicetree/bindings
	# DT_TMP_SCHEMA may be overridden from Documentation/devicetree/bindings/Makefile
	DT_TMP_SCHEMA ?= $(objtree)/$(DT_BINDING_DIR)/processed-schema.json

	quiet_cmd_dtb_check = CHECK $@
	cmd_dtb_check = $(DT_CHECKER) $(DT_CHECKER_FLAGS) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@

	define rule_dtc
	$(call cmd_and_fixdep,dtc)
	$(call cmd,dtb_check)
	endef

	$(obj)/%.dt.yaml: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
	$(call if_changed_rule,dtc)

	dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)

	# Bzip2
	# ---------------------------------------------------------------------------

	# Bzip2 and LZMA do not include size in file... so we have to fake that;
	# append the size as a 32-bit littleendian number as gzip does.
	size_append = printf $(shell \
	dec_size=0; \
	for F in $(real-prereqs); do \
	fsize=$$($(CONFIG_SHELL) $(srctree)/scripts/file-size.sh $$F); \
	dec_size=$$(expr $$dec_size + $$fsize); \
	done; \
	printf "%08x\n" $$dec_size \| \
	sed 's/\(..\)/\1 /g' \| { \
	read ch0 ch1 ch2 ch3; \
	for ch in $$ch3 $$ch2 $$ch1 $$ch0; do \
	printf '%s%03o' '\\' $$((0x$$ch)); \
	done; \
	} \
	)

	quiet_cmd_bzip2 = BZIP2 $@
	cmd_bzip2 = cat $(real-prereqs) \| $(KBZIP2) -9 > $@

	quiet_cmd_bzip2_with_size = BZIP2 $@
	cmd_bzip2_with_size = { cat $(real-prereqs) \| $(KBZIP2) -9; $(size_append); } > $@

	# Lzma
	# ---------------------------------------------------------------------------

	quiet_cmd_lzma = LZMA $@
	cmd_lzma = cat $(real-prereqs) \| $(LZMA) -9 > $@

	quiet_cmd_lzma_with_size = LZMA $@
	cmd_lzma_with_size = { cat $(real-prereqs) \| $(LZMA) -9; $(size_append); } > $@

	quiet_cmd_lzo = LZO $@
	cmd_lzo = cat $(real-prereqs) \| $(KLZOP) -9 > $@

	quiet_cmd_lzo_with_size = LZO $@
	cmd_lzo_with_size = { cat $(real-prereqs) \| $(KLZOP) -9; $(size_append); } > $@

	quiet_cmd_lz4 = LZ4 $@
	cmd_lz4 = cat $(real-prereqs) \| $(LZ4) -l -12 --favor-decSpeed stdin stdout > $@

	quiet_cmd_lz4_with_size = LZ4 $@
	cmd_lz4_with_size = { cat $(real-prereqs) \| $(LZ4) -l -12 --favor-decSpeed stdin stdout; \
	$(size_append); } > $@

	# U-Boot mkimage
	# ---------------------------------------------------------------------------

	MKIMAGE := $(srctree)/scripts/mkuboot.sh

	# SRCARCH just happens to match slightly more than ARCH (on sparc), so reduces
	# the number of overrides in arch makefiles
	UIMAGE_ARCH ?= $(SRCARCH)
	UIMAGE_COMPRESSION ?= $(if $(2),$(2),none)
	UIMAGE_OPTS-y ?=
	UIMAGE_TYPE ?= kernel
	UIMAGE_LOADADDR ?= arch_must_set_this
	UIMAGE_ENTRYADDR ?= $(UIMAGE_LOADADDR)
	UIMAGE_NAME ?= 'Linux-$(KERNELRELEASE)'

	quiet_cmd_uimage = UIMAGE $@
	cmd_uimage = $(BASH) $(MKIMAGE) -A $(UIMAGE_ARCH) -O linux \
	-C $(UIMAGE_COMPRESSION) $(UIMAGE_OPTS-y) \
	-T $(UIMAGE_TYPE) \
	-a $(UIMAGE_LOADADDR) -e $(UIMAGE_ENTRYADDR) \
	-n $(UIMAGE_NAME) -d $< $@

	# XZ
	# ---------------------------------------------------------------------------
	# Use xzkern to compress the kernel image and xzmisc to compress other things.
	#
	# xzkern uses a big LZMA2 dictionary since it doesn't increase memory usage
	# of the kernel decompressor. A BCJ filter is used if it is available for
	# the target architecture. xzkern also appends uncompressed size of the data
	# using size_append. The .xz format has the size information available at
	# the end of the file too, but it's in more complex format and it's good to
	# avoid changing the part of the boot code that reads the uncompressed size.
	# Note that the bytes added by size_append will make the xz tool think that
	# the file is corrupt. This is expected.
	#
	# xzmisc doesn't use size_append, so it can be used to create normal .xz
	# files. xzmisc uses smaller LZMA2 dictionary than xzkern, because a very
	# big dictionary would increase the memory usage too much in the multi-call
	# decompression mode. A BCJ filter isn't used either.
	quiet_cmd_xzkern = XZKERN $@
	cmd_xzkern = cat $(real-prereqs) \| sh $(srctree)/scripts/xz_wrap.sh > $@

	quiet_cmd_xzkern_with_size = XZKERN $@
	cmd_xzkern_with_size = { cat $(real-prereqs) \| sh $(srctree)/scripts/xz_wrap.sh; \
	$(size_append); } > $@

	quiet_cmd_xzmisc = XZMISC $@
	cmd_xzmisc = cat $(real-prereqs) \| $(XZ) --check=crc32 --lzma2=dict=1MiB > $@

	# ZSTD
	# ---------------------------------------------------------------------------
	# Appends the uncompressed size of the data using size_append. The .zst
	# format has the size information available at the beginning of the file too,
	# but it's in a more complex format and it's good to avoid changing the part
	# of the boot code that reads the uncompressed size.
	#
	# Note that the bytes added by size_append will make the zstd tool think that
	# the file is corrupt. This is expected.
	#
	# zstd uses a maximum window size of 8 MB. zstd22 uses a maximum window size of
	# 128 MB. zstd22 is used for kernel compression because it is decompressed in a
	# single pass, so zstd doesn't need to allocate a window buffer. When streaming
	# decompression is used, like initramfs decompression, zstd22 should likely not
	# be used because it would require zstd to allocate a 128 MB buffer.

	quiet_cmd_zstd = ZSTD $@
	cmd_zstd = { cat $(real-prereqs) \| $(ZSTD) -19; $(size_append); } > $@

	quiet_cmd_zstd22 = ZSTD22 $@
	cmd_zstd22 = cat $(real-prereqs) \| $(ZSTD) -22 --ultra > $@

	quiet_cmd_zstd22_with_size = ZSTD22 $@
	cmd_zstd22_with_size = { cat $(real-prereqs) \| $(ZSTD) -22 --ultra; $(size_append); } > $@

	# ASM offsets
	# ---------------------------------------------------------------------------

	# Default sed regexp - multiline due to syntax constraints
	#
	# Use [:space:] because LLVM's integrated assembler inserts <tab> around
	# the .ascii directive whereas GCC keeps the <space> as-is.
	define sed-offsets
	's:^[[:space:]]\.ascii[[:space:]]"\(.\)".:\1:; \
	/^->/{s:->#\(.\):/ \1 */:; \
	s:^->\([^ ]\) [\$$#]\([^ ]\) \(.\):#define \1 \2 /* \3 */:; \
	s:->::; p;}'
	endef

	# Use filechk to avoid rebuilds when a header changes, but the resulting file
	# does not
	define filechk_offsets
	echo "#ifndef $2"; \
	echo "#define $2"; \
	echo "/*"; \
	echo " * DO NOT MODIFY."; \
	echo " *"; \
	echo " * This file was generated by Kbuild"; \
	echo " */"; \
	echo ""; \
	sed -ne $(sed-offsets) < $<; \
	echo ""; \
	echo "#endif"
	endef