#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
#
# link vmlinux
#
# vmlinux is linked from the objects in vmlinux.a and $(KBUILD_VMLINUX_LIBS).
# vmlinux.a contains objects that are linked unconditionally.
# $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
# (not within --whole-archive), and do not require symbol indexes added.
#
# vmlinux
# ^
# |
# +--< vmlinux.a
# |
# +--< $(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"
is_enabled() {
grep -q "^$1=y" include/config/auto.conf
}
# Nice output in kbuild format
# Will be supressed by "make -s"
info()
{
printf " %-7s %s\n" "${1}" "${2}"
}
# Link of vmlinux
# ${1} - output file
vmlinux_link()
{
local output=${1}
local objs
local libs
local ld
local ldflags
local ldlibs
info LD ${output}
# skip output file argument
shift
if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
# Use vmlinux.o instead of performing the slow LTO link again.
objs=vmlinux.o
libs=
else
objs=vmlinux.a
libs="${KBUILD_VMLINUX_LIBS}"
fi
if is_enabled CONFIG_MODULES; then
objs="${objs} .vmlinux.export.o"
fi
objs="${objs} init/version-timestamp.o"
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}/${KBUILD_LDS}"
# The kallsyms linking does not need debug symbols included.
if [ -n "${strip_debug}" ] ; then
ldflags="${ldflags} ${wl}--strip-debug"
fi
if is_enabled CONFIG_VMLINUX_MAP; then
ldflags="${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 \
${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}
}
# generate .BTF typeinfo from DWARF debuginfo
# ${1} - vmlinux image
gen_btf()
{
local pahole_ver
local btf_data=${1}.btf.o
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
info BTF "${btf_data}"
LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
# Create ${btf_data} 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 ${1} "${btf_data}" 2>/dev/null
# Change e_type to ET_REL so that it can be used to link final vmlinux.
# GNU ld 2.35+ and lld do not allow an ET_EXEC input.
if is_enabled CONFIG_CPU_BIG_ENDIAN; then
et_rel='\0\1'
else
et_rel='\1\0'
fi
printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
btf_vmlinux_bin_o=${btf_data}
}
# Create ${2}.o file with all symbols from the ${1} object file
kallsyms()
{
local kallsymopt;
if is_enabled CONFIG_KALLSYMS_ALL; then
kallsymopt="${kallsymopt} --all-symbols"
fi
if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
kallsymopt="${kallsymopt} --absolute-percpu"
fi
if is_enabled CONFIG_LTO_CLANG; then
kallsymopt="${kallsymopt} --lto-clang"
fi
info KSYMS "${2}.S"
scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
info AS "${2}.o"
${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
kallsymso=${2}.o
}
# Perform kallsyms for the given temporary vmlinux.
sysmap_and_kallsyms()
{
mksysmap "${1}" "${1}.syms"
kallsyms "${1}.syms" "${1}.kallsyms"
kallsyms_sysmap=${1}.syms
}
# Create map file with all symbols from ${1}
# See mksymap for additional details
mksysmap()
{
info NM ${2}
${NM} -n "${1}" | sed -f "${srctree}/scripts/mksysmap" > "${2}"
}
sorttable()
{
${objtree}/scripts/sorttable ${1}
}
cleanup()
{
rm -f .btf.*
rm -f System.map
rm -f vmlinux
rm -f vmlinux.map
}
# Use "make V=1" to debug this script
case "${KBUILD_VERBOSE}" in
*1*)
set -x
;;
esac
if [ "$1" = "clean" ]; then
cleanup
exit 0
fi
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
btf_vmlinux_bin_o=
kallsymso=
strip_debug=
if is_enabled CONFIG_KALLSYMS; then
kallsyms /dev/null .tmp_vmlinux0.kallsyms
fi
if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
# The kallsyms linking does not need debug symbols, but the BTF does.
if ! is_enabled CONFIG_DEBUG_INFO_BTF; then
strip_debug=1
fi
vmlinux_link .tmp_vmlinux1
fi
if is_enabled CONFIG_DEBUG_INFO_BTF; then
if ! gen_btf .tmp_vmlinux1; then
echo >&2 "Failed to generate BTF for vmlinux"
echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
exit 1
fi
fi
if is_enabled CONFIG_KALLSYMS; then
# kallsyms support
# Generate section listing all symbols and add it into vmlinux
# It's a four step process:
# 0) Generate a dummy __kallsyms with empty symbol list.
# 1) Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
# with a dummy __kallsyms.
# Running kallsyms on that gives us .tmp_kallsyms1.o with
# the right size
# 2) Link .tmp_vmlinux.kallsyms2 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_vmlinux.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
# ${kallsymso}.
# The kallsyms linking does not need debug symbols included.
strip_debug=1
sysmap_and_kallsyms .tmp_vmlinux1
size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
vmlinux_link .tmp_vmlinux2
sysmap_and_kallsyms .tmp_vmlinux2
size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
vmlinux_link .tmp_vmlinux3
sysmap_and_kallsyms .tmp_vmlinux3
fi
fi
strip_debug=
vmlinux_link vmlinux
# fill in BTF IDs
if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
info BTFIDS vmlinux
${RESOLVE_BTFIDS} vmlinux
fi
mksysmap vmlinux System.map
if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
info SORTTAB vmlinux
if ! sorttable vmlinux; then
echo >&2 Failed to sort kernel tables
exit 1
fi
fi
# step a (see comment above)
if is_enabled CONFIG_KALLSYMS; then
if ! cmp -s System.map "${kallsyms_sysmap}"; 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
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