#!/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
  
  # Nice output in kbuild format
  # Will be supressed by "make -s"
  info()
  {
  	if [ "${quiet}" != "silent_" ]; then

  		printf "  %-7s %s
  " "${1}" "${2}"

  	fi
  }
  
  # Link of vmlinux.o used for section mismatch analysis
  # ${1} output file
  modpost_link()
  {

  	local objects

  	objects="--whole-archive				\

  		${KBUILD_VMLINUX_OBJS}				\

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

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

  }
  
  # Link of vmlinux

  # ${1} - output file

  # ${2}, ${3}, ... - optional extra .o files

  vmlinux_link()
  {
  	local lds="${objtree}/${KBUILD_LDS}"

  	local output=${1}

  	local objects

  	local strip_debug

  	info LD ${output}

  	# skip output file argument
  	shift

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

  	if [ "${SRCARCH}" != "um" ]; then

  		objects="--whole-archive			\

  			${KBUILD_VMLINUX_OBJS}			\

  			--no-whole-archive			\
  			--start-group				\
  			${KBUILD_VMLINUX_LIBS}			\
  			--end-group				\

  			${@}"

  		${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}	\

  			${strip_debug#-Wl,}			\

  			-o ${output}				\

  			-T ${lds} ${objects}

  	else

  		objects="-Wl,--whole-archive			\

  			${KBUILD_VMLINUX_OBJS}			\

  			-Wl,--no-whole-archive			\
  			-Wl,--start-group			\
  			${KBUILD_VMLINUX_LIBS}			\
  			-Wl,--end-group				\

  			${@}"

  		${CC} ${CFLAGS_vmlinux}				\

  			${strip_debug}				\

  			-o ${output}				\

  			-Wl,-T,${lds}				\
  			${objects}				\

  			-lutil -lrt -lpthread

  		rm -f linux
  	fi
  }

  # generate .BTF typeinfo from DWARF debuginfo

  # ${1} - vmlinux image
  # ${2} - file to dump raw BTF data into

  gen_btf()
  {

  	local pahole_ver

  	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 "113" ]; then

  		echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13"

  		return 1

  	fi

  	vmlinux_link ${1}

  
  	info "BTF" ${2}

  	LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${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} .o file with all symbols from the ${1} object file
  kallsyms()
  {
  	info KSYM ${2}
  	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

  	local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL}               \
  		      ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"

  	local afile="`basename ${2} .o`.S"
  
  	${NM} -n ${1} | scripts/kallsyms ${kallsymopt} > ${afile}
  	${CC} ${aflags} -c -o ${2} ${afile}

  }

  # 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

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

  	kallsyms ${kallsyms_vmlinux} ${kallsymso}
  }

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

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

  # Delete output files in case of error

  cleanup()
  {

  	rm -f .btf.*

  	rm -f .tmp_System.map

  	rm -f .tmp_vmlinux*
  	rm -f System.map
  	rm -f vmlinux
  	rm -f vmlinux.o
  }

  on_exit()
  {
  	if [ $? -ne 0 ]; then
  		cleanup
  	fi
  }
  trap on_exit EXIT
  
  on_signals()
  {
  	exit 1
  }
  trap on_signals HUP INT QUIT TERM

  #
  #
  # 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

  #link vmlinux.o
  info LD vmlinux.o
  modpost_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

  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}

  if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then
  	info SORTEX vmlinux
  	sortextable vmlinux
  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