scripts/link-vmlinux.sh - linux - Git at Google

 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 #
 # link vmlinux
 #
 # vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_OBJS) and
 # $(KBUILD_VMLINUX_LIBS). Most are built-in.a files from top-level directories
 # in the kernel tree, others are specified in arch/$(ARCH)/Makefile.
 # $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
 # (not within --whole-archive), and do not require symbol indexes added.
 #
 # vmlinux
 #   ^
 #   |
 #   +--< $(KBUILD_VMLINUX_OBJS)
 #   |    +--< init/built-in.a drivers/built-in.a mm/built-in.a + more
 #   |
 #   +--< $(KBUILD_VMLINUX_LIBS)
 #   |    +--< lib/lib.a + more
 #   |
 #   +-< ${kallsymso} (see description in KALLSYMS section)
 #
 # vmlinux version (uname -v) cannot be updated during normal
 # descending-into-subdirs phase since we do not yet know if we need to
 # update vmlinux.
 # Therefore this step is delayed until just before final link of vmlinux.
 #
 # System.map is generated to document addresses of all kernel symbols

 # Error out on error
 set -e

 LD="$1"
 KBUILD_LDFLAGS="$2"
 LDFLAGS_vmlinux="$3"

 # Nice output in kbuild format
 # Will be supressed by "make -s"
 info()
 {
 	printf "  %-7s %s\n" "${1}" "${2}"
 }

 # Generate a linker script to ensure correct ordering of initcalls.
 gen_initcalls()
 {
 	info GEN .tmp_initcalls.lds

 	${PYTHON} ${srctree}/scripts/jobserver-exec		\
 	${PERL} ${srctree}/scripts/generate_initcall_order.pl	\
 		${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}	\
 		> .tmp_initcalls.lds
 }

 # If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
 # .tmp_symversions.lds
 gen_symversions()
 {
 	info GEN .tmp_symversions.lds
 	rm -f .tmp_symversions.lds

 	for o in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
 		if [ -f ${o}.symversions ]; then
 			cat ${o}.symversions >> .tmp_symversions.lds
 		fi
 	done
 }

 # Link of vmlinux.o used for section mismatch analysis
 # ${1} output file
 modpost_link()
 {
 	local objects
 	local lds=""

 	objects="--whole-archive				\
 		${KBUILD_VMLINUX_OBJS}				\
 		--no-whole-archive				\
 		--start-group					\
 		${KBUILD_VMLINUX_LIBS}				\
 		--end-group"

 	if [ -n "${CONFIG_LTO_CLANG}" ]; then
 		gen_initcalls
 		lds="-T .tmp_initcalls.lds"

 		if [ -n "${CONFIG_MODVERSIONS}" ]; then
 			gen_symversions
 			lds="${lds} -T .tmp_symversions.lds"
 		fi

 		# This might take a while, so indicate that we're doing
 		# an LTO link
 		info LTO ${1}
 	else
 		info LD ${1}
 	fi

 	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${lds} ${objects}
 }

 objtool_link()
 {
 	local objtoolcmd;
 	local objtoolopt;

 	if [ "${CONFIG_LTO_CLANG} ${CONFIG_STACK_VALIDATION}" = "y y" ]; then
 		# Don't perform vmlinux validation unless explicitly requested,
 		# but run objtool on vmlinux.o now that we have an object file.
 		if [ -n "${CONFIG_UNWINDER_ORC}" ]; then
 			objtoolcmd="orc generate"
 		fi

 		objtoolopt="${objtoolopt} --duplicate"

 		if [ -n "${CONFIG_FTRACE_MCOUNT_USE_OBJTOOL}" ]; then
 			objtoolopt="${objtoolopt} --mcount"
 		fi
 	fi

 	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
 		objtoolopt="${objtoolopt} --noinstr"
 	fi

 	if [ -n "${objtoolopt}" ]; then
 		if [ -z "${objtoolcmd}" ]; then
 			objtoolcmd="check"
 		fi
 		objtoolopt="${objtoolopt} --vmlinux"
 		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
 			objtoolopt="${objtoolopt} --no-fp"
 		fi
 		if [ -n "${CONFIG_GCOV_KERNEL}" ] || [ -n "${CONFIG_LTO_CLANG}" ]; then
 			objtoolopt="${objtoolopt} --no-unreachable"
 		fi
 		if [ -n "${CONFIG_RETPOLINE}" ]; then
 			objtoolopt="${objtoolopt} --retpoline"
 		fi
 		if [ -n "${CONFIG_X86_SMAP}" ]; then
 			objtoolopt="${objtoolopt} --uaccess"
 		fi
 		info OBJTOOL ${1}
 		tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
 	fi
 }

 # Link of vmlinux
 # ${1} - output file
 # ${2}, ${3}, ... - optional extra .o files
 vmlinux_link()
 {
 	local output=${1}
 	local objs
 	local libs
 	local ld
 	local ldflags
 	local ldlibs

 	info LD ${output}

 	# skip output file argument
 	shift

 	if [ -n "${CONFIG_LTO_CLANG}" ]; then
 		# Use vmlinux.o instead of performing the slow LTO link again.
 		objs=vmlinux.o
 		libs=
 	else
 		objs="${KBUILD_VMLINUX_OBJS}"
 		libs="${KBUILD_VMLINUX_LIBS}"
 	fi

 	if [ "${SRCARCH}" = "um" ]; then
 		wl=-Wl,
 		ld="${CC}"
 		ldflags="${CFLAGS_vmlinux}"
 		ldlibs="-lutil -lrt -lpthread"
 	else
 		wl=
 		ld="${LD}"
 		ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
 		ldlibs=
 	fi

 	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"

 	# The kallsyms linking does not need debug symbols included.
 	if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
 		ldflags="${ldflags} ${wl}--strip-debug"
 	fi

 	if [ -n "${CONFIG_VMLINUX_MAP}" ]; then
 		ldflags="${ldflags} ${wl}-Map=${output}.map"
 	fi

 	${ld} ${ldflags} -o ${output}					\
 		${wl}--whole-archive ${objs} ${wl}--no-whole-archive	\
 		${wl}--start-group ${libs} ${wl}--end-group		\
 		$@ ${ldlibs}
 }

 # generate .BTF typeinfo from DWARF debuginfo
 # ${1} - vmlinux image
 # ${2} - file to dump raw BTF data into
 gen_btf()
 {
 	local pahole_ver
 	local extra_paholeopt=

 	if ! [ -x "$(command -v ${PAHOLE})" ]; then
 		echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
 		return 1
 	fi

 	pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
 	if [ "${pahole_ver}" -lt "116" ]; then
 		echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.16"
 		return 1
 	fi

 	vmlinux_link ${1}

 	if [ "${pahole_ver}" -ge "118" ] && [ "${pahole_ver}" -le "121" ]; then
 		# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars
 		extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_vars"
 	fi
 	if [ "${pahole_ver}" -ge "121" ]; then
 		extra_paholeopt="${extra_paholeopt} --btf_gen_floats"
 	fi

 	info "BTF" ${2}
 	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${extra_paholeopt} ${1}

 	# Create ${2} which contains just .BTF section but no symbols. Add
 	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
 	# deletes all symbols including __start_BTF and __stop_BTF, which will
 	# be redefined in the linker script. Add 2>/dev/null to suppress GNU
 	# objcopy warnings: "empty loadable segment detected at ..."
 	${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
 		--strip-all ${1} ${2} 2>/dev/null
 	# Change e_type to ET_REL so that it can be used to link final vmlinux.
 	# Unlike GNU ld, lld does not allow an ET_EXEC input.
 	printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none
 }

 # Create ${2} .S file with all symbols from the ${1} object file
 kallsyms()
 {
 	local kallsymopt;

 	if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
 		kallsymopt="${kallsymopt} --all-symbols"
 	fi

 	if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
 		kallsymopt="${kallsymopt} --absolute-percpu"
 	fi

 	if [ -n "${CONFIG_KALLSYMS_BASE_RELATIVE}" ]; then
 		kallsymopt="${kallsymopt} --base-relative"
 	fi

 	info KSYMS ${2}
 	${NM} -n ${1} | scripts/kallsyms ${kallsymopt} > ${2}
 }

 # Perform one step in kallsyms generation, including temporary linking of
 # vmlinux.
 kallsyms_step()
 {
 	kallsymso_prev=${kallsymso}
 	kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
 	kallsymso=${kallsyms_vmlinux}.o
 	kallsyms_S=${kallsyms_vmlinux}.S

 	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
 	kallsyms ${kallsyms_vmlinux} ${kallsyms_S}

 	info AS ${kallsyms_S}
 	${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
 	      ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
 	      -c -o ${kallsymso} ${kallsyms_S}
 }

 # Create map file with all symbols from ${1}
 # See mksymap for additional details
 mksysmap()
 {
 	${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
 }

 sorttable()
 {
 	${objtree}/scripts/sorttable ${1}
 }

 # Delete output files in case of error
 cleanup()
 {
 	rm -f .btf.*
 	rm -f .tmp_System.map
 	rm -f .tmp_initcalls.lds
 	rm -f .tmp_symversions.lds
 	rm -f .tmp_vmlinux*
 	rm -f System.map
 	rm -f vmlinux
 	rm -f vmlinux.map
 	rm -f vmlinux.o
 	rm -f .vmlinux.d
 }

 # Use "make V=1" to debug this script
 case "${KBUILD_VERBOSE}" in
 *1*)
 	set -x
 	;;
 esac

 if [ "$1" = "clean" ]; then
 	cleanup
 	exit 0
 fi

 # We need access to CONFIG_ symbols
 . include/config/auto.conf

 # Update version
 info GEN .version
 if [ -r .version ]; then
 	VERSION=$(expr 0$(cat .version) + 1)
 	echo $VERSION > .version
 else
 	rm -f .version
 	echo 1 > .version
 fi;

 # final build of init/
 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1

 #link vmlinux.o
 modpost_link vmlinux.o
 objtool_link vmlinux.o

 # modpost vmlinux.o to check for section mismatches
 ${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1

 info MODINFO modules.builtin.modinfo
 ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
 info GEN modules.builtin
 # The second line aids cases where multiple modules share the same object.
 tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
 	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin

 btf_vmlinux_bin_o=""
 if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
 	btf_vmlinux_bin_o=.btf.vmlinux.bin.o
 	if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
 		echo >&2 "Failed to generate BTF for vmlinux"
 		echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
 		exit 1
 	fi
 fi

 kallsymso=""
 kallsymso_prev=""
 kallsyms_vmlinux=""
 if [ -n "${CONFIG_KALLSYMS}" ]; then

 	# kallsyms support
 	# Generate section listing all symbols and add it into vmlinux
 	# It's a three step process:
 	# 1)  Link .tmp_vmlinux1 so it has all symbols and sections,
 	#     but __kallsyms is empty.
 	#     Running kallsyms on that gives us .tmp_kallsyms1.o with
 	#     the right size
 	# 2)  Link .tmp_vmlinux2 so it now has a __kallsyms section of
 	#     the right size, but due to the added section, some
 	#     addresses have shifted.
 	#     From here, we generate a correct .tmp_kallsyms2.o
 	# 3)  That link may have expanded the kernel image enough that
 	#     more linker branch stubs / trampolines had to be added, which
 	#     introduces new names, which further expands kallsyms. Do another
 	#     pass if that is the case. In theory it's possible this results
 	#     in even more stubs, but unlikely.
 	#     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
 	#     other bugs.
 	# 4)  The correct ${kallsymso} is linked into the final vmlinux.
 	#
 	# a)  Verify that the System.map from vmlinux matches the map from
 	#     ${kallsymso}.

 	kallsyms_step 1
 	kallsyms_step 2

 	# step 3
 	size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
 	size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})

 	if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
 		kallsyms_step 3
 	fi
 fi

 vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}

 # fill in BTF IDs
 if [ -n "${CONFIG_DEBUG_INFO_BTF}" -a -n "${CONFIG_BPF}" ]; then
 	info BTFIDS vmlinux
 	${RESOLVE_BTFIDS} vmlinux
 fi

 if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then
 	info SORTTAB vmlinux
 	if ! sorttable vmlinux; then
 		echo >&2 Failed to sort kernel tables
 		exit 1
 	fi
 fi

 info SYSMAP System.map
 mksysmap vmlinux System.map

 # step a (see comment above)
 if [ -n "${CONFIG_KALLSYMS}" ]; then
 	mksysmap ${kallsyms_vmlinux} .tmp_System.map

 	if ! cmp -s System.map .tmp_System.map; then
 		echo >&2 Inconsistent kallsyms data
 		echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
 		exit 1
 	fi
 fi

 # For fixdep
 echo "vmlinux: $0" > .vmlinux.d
	#!/bin/sh
	# SPDX-License-Identifier: GPL-2.0
	#
	# link vmlinux
	#
	# vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_OBJS) and
	# $(KBUILD_VMLINUX_LIBS). Most are built-in.a files from top-level directories
	# in the kernel tree, others are specified in arch/$(ARCH)/Makefile.
	# $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
	# (not within --whole-archive), and do not require symbol indexes added.
	#
	# vmlinux
	# ^
	# \|
	# +--< $(KBUILD_VMLINUX_OBJS)
	# \| +--< init/built-in.a drivers/built-in.a mm/built-in.a + more
	# \|
	# +--< $(KBUILD_VMLINUX_LIBS)
	# \| +--< lib/lib.a + more
	# \|
	# +-< ${kallsymso} (see description in KALLSYMS section)
	#
	# vmlinux version (uname -v) cannot be updated during normal
	# descending-into-subdirs phase since we do not yet know if we need to
	# update vmlinux.
	# Therefore this step is delayed until just before final link of vmlinux.
	#
	# System.map is generated to document addresses of all kernel symbols

	# Error out on error
	set -e

	LD="$1"
	KBUILD_LDFLAGS="$2"
	LDFLAGS_vmlinux="$3"

	# Nice output in kbuild format
	# Will be supressed by "make -s"
	info()
	{
	printf " %-7s %s\n" "${1}" "${2}"
	}

	# Generate a linker script to ensure correct ordering of initcalls.
	gen_initcalls()
	{
	info GEN .tmp_initcalls.lds

	${PYTHON} ${srctree}/scripts/jobserver-exec \
	${PERL} ${srctree}/scripts/generate_initcall_order.pl \
	${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS} \
	> .tmp_initcalls.lds
	}

	# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
	# .tmp_symversions.lds
	gen_symversions()
	{
	info GEN .tmp_symversions.lds
	rm -f .tmp_symversions.lds

	for o in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
	if [ -f ${o}.symversions ]; then
	cat ${o}.symversions >> .tmp_symversions.lds
	fi
	done
	}

	# Link of vmlinux.o used for section mismatch analysis
	# ${1} output file
	modpost_link()
	{
	local objects
	local lds=""

	objects="--whole-archive \
	${KBUILD_VMLINUX_OBJS} \
	--no-whole-archive \
	--start-group \
	${KBUILD_VMLINUX_LIBS} \
	--end-group"

	if [ -n "${CONFIG_LTO_CLANG}" ]; then
	gen_initcalls
	lds="-T .tmp_initcalls.lds"

	if [ -n "${CONFIG_MODVERSIONS}" ]; then
	gen_symversions
	lds="${lds} -T .tmp_symversions.lds"
	fi

	# This might take a while, so indicate that we're doing
	# an LTO link
	info LTO ${1}
	else
	info LD ${1}
	fi

	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${lds} ${objects}
	}

	objtool_link()
	{
	local objtoolcmd;
	local objtoolopt;

	if [ "${CONFIG_LTO_CLANG} ${CONFIG_STACK_VALIDATION}" = "y y" ]; then
	# Don't perform vmlinux validation unless explicitly requested,
	# but run objtool on vmlinux.o now that we have an object file.
	if [ -n "${CONFIG_UNWINDER_ORC}" ]; then
	objtoolcmd="orc generate"
	fi

	objtoolopt="${objtoolopt} --duplicate"

	if [ -n "${CONFIG_FTRACE_MCOUNT_USE_OBJTOOL}" ]; then
	objtoolopt="${objtoolopt} --mcount"
	fi
	fi

	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
	objtoolopt="${objtoolopt} --noinstr"
	fi

	if [ -n "${objtoolopt}" ]; then
	if [ -z "${objtoolcmd}" ]; then
	objtoolcmd="check"
	fi
	objtoolopt="${objtoolopt} --vmlinux"
	if [ -z "${CONFIG_FRAME_POINTER}" ]; then
	objtoolopt="${objtoolopt} --no-fp"
	fi
	if [ -n "${CONFIG_GCOV_KERNEL}" ] \|\| [ -n "${CONFIG_LTO_CLANG}" ]; then
	objtoolopt="${objtoolopt} --no-unreachable"
	fi
	if [ -n "${CONFIG_RETPOLINE}" ]; then
	objtoolopt="${objtoolopt} --retpoline"
	fi
	if [ -n "${CONFIG_X86_SMAP}" ]; then
	objtoolopt="${objtoolopt} --uaccess"
	fi
	info OBJTOOL ${1}
	tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
	fi
	}

	# Link of vmlinux
	# ${1} - output file
	# ${2}, ${3}, ... - optional extra .o files
	vmlinux_link()
	{
	local output=${1}
	local objs
	local libs
	local ld
	local ldflags
	local ldlibs

	info LD ${output}

	# skip output file argument
	shift

	if [ -n "${CONFIG_LTO_CLANG}" ]; then
	# Use vmlinux.o instead of performing the slow LTO link again.
	objs=vmlinux.o
	libs=
	else
	objs="${KBUILD_VMLINUX_OBJS}"
	libs="${KBUILD_VMLINUX_LIBS}"
	fi

	if [ "${SRCARCH}" = "um" ]; then
	wl=-Wl,
	ld="${CC}"
	ldflags="${CFLAGS_vmlinux}"
	ldlibs="-lutil -lrt -lpthread"
	else
	wl=
	ld="${LD}"
	ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
	ldlibs=
	fi

	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"

	# The kallsyms linking does not need debug symbols included.
	if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
	ldflags="${ldflags} ${wl}--strip-debug"
	fi

	if [ -n "${CONFIG_VMLINUX_MAP}" ]; then
	ldflags="${ldflags} ${wl}-Map=${output}.map"
	fi

	${ld} ${ldflags} -o ${output} \
	${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
	${wl}--start-group ${libs} ${wl}--end-group \
	$@ ${ldlibs}
	}

	# generate .BTF typeinfo from DWARF debuginfo
	# ${1} - vmlinux image
	# ${2} - file to dump raw BTF data into
	gen_btf()
	{
	local pahole_ver
	local extra_paholeopt=

	if ! [ -x "$(command -v ${PAHOLE})" ]; then
	echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
	return 1
	fi

	pahole_ver=$(${PAHOLE} --version \| sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
	if [ "${pahole_ver}" -lt "116" ]; then
	echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.16"
	return 1
	fi

	vmlinux_link ${1}

	if [ "${pahole_ver}" -ge "118" ] && [ "${pahole_ver}" -le "121" ]; then
	# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars
	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_vars"
	fi
	if [ "${pahole_ver}" -ge "121" ]; then
	extra_paholeopt="${extra_paholeopt} --btf_gen_floats"
	fi

	info "BTF" ${2}
	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${extra_paholeopt} ${1}

	# Create ${2} which contains just .BTF section but no symbols. Add
	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
	# deletes all symbols including __start_BTF and __stop_BTF, which will
	# be redefined in the linker script. Add 2>/dev/null to suppress GNU
	# objcopy warnings: "empty loadable segment detected at ..."
	${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
	--strip-all ${1} ${2} 2>/dev/null
	# Change e_type to ET_REL so that it can be used to link final vmlinux.
	# Unlike GNU ld, lld does not allow an ET_EXEC input.
	printf '\1' \| dd of=${2} conv=notrunc bs=1 seek=16 status=none
	}

	# Create ${2} .S file with all symbols from the ${1} object file
	kallsyms()
	{
	local kallsymopt;

	if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
	kallsymopt="${kallsymopt} --all-symbols"
	fi

	if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
	kallsymopt="${kallsymopt} --absolute-percpu"
	fi

	if [ -n "${CONFIG_KALLSYMS_BASE_RELATIVE}" ]; then
	kallsymopt="${kallsymopt} --base-relative"
	fi

	info KSYMS ${2}
	${NM} -n ${1} \| scripts/kallsyms ${kallsymopt} > ${2}
	}

	# Perform one step in kallsyms generation, including temporary linking of
	# vmlinux.
	kallsyms_step()
	{
	kallsymso_prev=${kallsymso}
	kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
	kallsymso=${kallsyms_vmlinux}.o
	kallsyms_S=${kallsyms_vmlinux}.S

	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
	kallsyms ${kallsyms_vmlinux} ${kallsyms_S}

	info AS ${kallsyms_S}
	${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
	${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
	-c -o ${kallsymso} ${kallsyms_S}
	}

	# Create map file with all symbols from ${1}
	# See mksymap for additional details
	mksysmap()
	{
	${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
	}

	sorttable()
	{
	${objtree}/scripts/sorttable ${1}
	}

	# Delete output files in case of error
	cleanup()
	{
	rm -f .btf.*
	rm -f .tmp_System.map
	rm -f .tmp_initcalls.lds
	rm -f .tmp_symversions.lds
	rm -f .tmp_vmlinux*
	rm -f System.map
	rm -f vmlinux
	rm -f vmlinux.map
	rm -f vmlinux.o
	rm -f .vmlinux.d
	}

	# Use "make V=1" to debug this script
	case "${KBUILD_VERBOSE}" in
	1)
	set -x
	;;
	esac

	if [ "$1" = "clean" ]; then
	cleanup
	exit 0
	fi

	# We need access to CONFIG_ symbols
	. include/config/auto.conf

	# Update version
	info GEN .version
	if [ -r .version ]; then
	VERSION=$(expr 0$(cat .version) + 1)
	echo $VERSION > .version
	else
	rm -f .version
	echo 1 > .version
	fi;

	# final build of init/
	${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1

	#link vmlinux.o
	modpost_link vmlinux.o
	objtool_link vmlinux.o

	# modpost vmlinux.o to check for section mismatches
	${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1

	info MODINFO modules.builtin.modinfo
	${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
	info GEN modules.builtin
	# The second line aids cases where multiple modules share the same object.
	tr '\0' '\n' < modules.builtin.modinfo \| sed -n 's/^[[:alnum:]:_]*\.file=//p' \|
	tr ' ' '\n' \| uniq \| sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin

	btf_vmlinux_bin_o=""
	if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
	btf_vmlinux_bin_o=.btf.vmlinux.bin.o
	if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
	echo >&2 "Failed to generate BTF for vmlinux"
	echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
	exit 1
	fi
	fi

	kallsymso=""
	kallsymso_prev=""
	kallsyms_vmlinux=""
	if [ -n "${CONFIG_KALLSYMS}" ]; then

	# kallsyms support
	# Generate section listing all symbols and add it into vmlinux
	# It's a three step process:
	# 1) Link .tmp_vmlinux1 so it has all symbols and sections,
	# but __kallsyms is empty.
	# Running kallsyms on that gives us .tmp_kallsyms1.o with
	# the right size
	# 2) Link .tmp_vmlinux2 so it now has a __kallsyms section of
	# the right size, but due to the added section, some
	# addresses have shifted.
	# From here, we generate a correct .tmp_kallsyms2.o
	# 3) That link may have expanded the kernel image enough that
	# more linker branch stubs / trampolines had to be added, which
	# introduces new names, which further expands kallsyms. Do another
	# pass if that is the case. In theory it's possible this results
	# in even more stubs, but unlikely.
	# KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
	# other bugs.
	# 4) The correct ${kallsymso} is linked into the final vmlinux.
	#
	# a) Verify that the System.map from vmlinux matches the map from
	# ${kallsymso}.

	kallsyms_step 1
	kallsyms_step 2

	# step 3
	size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
	size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})

	if [ $size1 -ne $size2 ] \|\| [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
	kallsyms_step 3
	fi
	fi

	vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}

	# fill in BTF IDs
	if [ -n "${CONFIG_DEBUG_INFO_BTF}" -a -n "${CONFIG_BPF}" ]; then
	info BTFIDS vmlinux
	${RESOLVE_BTFIDS} vmlinux
	fi

	if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then
	info SORTTAB vmlinux
	if ! sorttable vmlinux; then
	echo >&2 Failed to sort kernel tables
	exit 1
	fi
	fi

	info SYSMAP System.map
	mksysmap vmlinux System.map

	# step a (see comment above)
	if [ -n "${CONFIG_KALLSYMS}" ]; then
	mksysmap ${kallsyms_vmlinux} .tmp_System.map

	if ! cmp -s System.map .tmp_System.map; then
	echo >&2 Inconsistent kallsyms data
	echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
	exit 1
	fi
	fi

	# For fixdep
	echo "vmlinux: $0" > .vmlinux.d