path: root/scripts/link-vmlinux.sh

#!/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()
{
	if [ "${quiet}" != "silent_" ]; then
		printf "  %-7s %s\n" "${1}" "${2}"
	fi
}

# 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}, ${3}, ... - optional extra .o files
vmlinux_link()
{
	local lds="${objtree}/${KBUILD_LDS}"
	local output=${1}
	local objects
	local strip_debug
	local map_option

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

	if [ "${SRCARCH}" != "um" ]; then
		if [ -n "${CONFIG_LTO_CLANG}" ]; then
			# Use vmlinux.o instead of performing the slow LTO
			# link again.
			objects="--whole-archive		\
				vmlinux.o 			\
				--no-whole-archive		\
				${@}"
		else
			objects="--whole-archive		\
				${KBUILD_VMLINUX_OBJS}		\
				--no-whole-archive		\
				--start-group			\
				${KBUILD_VMLINUX_LIBS}		\
				--end-group			\
				${@}"
		fi

		${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}	\
			${strip_debug#-Wl,}			\
			-o ${output}				\
			${map_option}				\
			-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}				\
			${map_option:+-Wl,${map_option}}	\
			-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
	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 [ "${pahole_ver}" -ge "121" ]; then
		extra_paholeopt="${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