1#!/bin/sh
  2# SPDX-License-Identifier: GPL-2.0
  3#
  4# link vmlinux
  5#
  6# vmlinux is linked from the objects in vmlinux.a and $(KBUILD_VMLINUX_LIBS).
  7# vmlinux.a contains objects that are linked unconditionally.
  8# $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
  9# (not within --whole-archive), and do not require symbol indexes added.
 10#
 11# vmlinux
 12#   ^
 13#   |
 14#   +--< vmlinux.a
 15#   |
 16#   +--< $(KBUILD_VMLINUX_LIBS)
 17#   |    +--< lib/lib.a + more
 18#   |
 19#   +-< ${kallsymso} (see description in KALLSYMS section)
 20#
 21# vmlinux version (uname -v) cannot be updated during normal
 22# descending-into-subdirs phase since we do not yet know if we need to
 23# update vmlinux.
 24# Therefore this step is delayed until just before final link of vmlinux.
 25#
 26# System.map is generated to document addresses of all kernel symbols
 27
 28# Error out on error
 29set -e
 30
 31LD="$1"
 32KBUILD_LDFLAGS="$2"
 33LDFLAGS_vmlinux="$3"
 34
 35is_enabled() {
 36	grep -q "^$1=y" include/config/auto.conf
 37}
 38
 39# Nice output in kbuild format
 40# Will be supressed by "make -s"
 41info()
 42{
 43	printf "  %-7s %s\n" "${1}" "${2}"
 44}
 45
 46# Link of vmlinux
 47# ${1} - output file
 48# ${2}, ${3}, ... - optional extra .o files
 49vmlinux_link()
 50{
 51	local output=${1}
 52	local objs
 53	local libs
 54	local ld
 55	local ldflags
 56	local ldlibs
 57
 58	info LD ${output}
 59
 60	# skip output file argument
 61	shift
 62
 63	if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
 64		# Use vmlinux.o instead of performing the slow LTO link again.
 65		objs=vmlinux.o
 66		libs=
 67	else
 68		objs=vmlinux.a
 69		libs="${KBUILD_VMLINUX_LIBS}"
 70	fi
 71
 72	if is_enabled CONFIG_MODULES; then
 73		objs="${objs} .vmlinux.export.o"
 74	fi
 75
 76	objs="${objs} init/version-timestamp.o"
 77
 78	if [ "${SRCARCH}" = "um" ]; then
 79		wl=-Wl,
 80		ld="${CC}"
 81		ldflags="${CFLAGS_vmlinux}"
 82		ldlibs="-lutil -lrt -lpthread"
 83	else
 84		wl=
 85		ld="${LD}"
 86		ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
 87		ldlibs=
 88	fi
 89
 90	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
 91
 92	# The kallsyms linking does not need debug symbols included.
 93	if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
 94		ldflags="${ldflags} ${wl}--strip-debug"
 95	fi
 96
 97	if is_enabled CONFIG_VMLINUX_MAP; then
 98		ldflags="${ldflags} ${wl}-Map=${output}.map"
 99	fi
100
101	${ld} ${ldflags} -o ${output}					\
102		${wl}--whole-archive ${objs} ${wl}--no-whole-archive	\
103		${wl}--start-group ${libs} ${wl}--end-group		\
104		$@ ${ldlibs}
105}
106
107# generate .BTF typeinfo from DWARF debuginfo
108# ${1} - vmlinux image
109# ${2} - file to dump raw BTF data into
110gen_btf()
111{
112	local pahole_ver
113
114	if ! [ -x "$(command -v ${PAHOLE})" ]; then
115		echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
116		return 1
117	fi
118
119	pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
120	if [ "${pahole_ver}" -lt "116" ]; then
121		echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.16"
122		return 1
123	fi
124
125	vmlinux_link ${1}
126
127	info "BTF" ${2}
128	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
129
130	# Create ${2} which contains just .BTF section but no symbols. Add
131	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
132	# deletes all symbols including __start_BTF and __stop_BTF, which will
133	# be redefined in the linker script. Add 2>/dev/null to suppress GNU
134	# objcopy warnings: "empty loadable segment detected at ..."
135	${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
136		--strip-all ${1} ${2} 2>/dev/null
137	# Change e_type to ET_REL so that it can be used to link final vmlinux.
138	# GNU ld 2.35+ and lld do not allow an ET_EXEC input.
139	if is_enabled CONFIG_CPU_BIG_ENDIAN; then
140		et_rel='\0\1'
141	else
142		et_rel='\1\0'
143	fi
144	printf "${et_rel}" | dd of=${2} conv=notrunc bs=1 seek=16 status=none
145}
146
147# Create ${2} .S file with all symbols from the ${1} object file
148kallsyms()
149{
150	local kallsymopt;
151
152	if is_enabled CONFIG_KALLSYMS_ALL; then
153		kallsymopt="${kallsymopt} --all-symbols"
154	fi
155
156	if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
157		kallsymopt="${kallsymopt} --absolute-percpu"
158	fi
159
160	if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
161		kallsymopt="${kallsymopt} --base-relative"
162	fi
163
164	if is_enabled CONFIG_LTO_CLANG; then
165		kallsymopt="${kallsymopt} --lto-clang"
166	fi
167
168	info KSYMS ${2}
169	scripts/kallsyms ${kallsymopt} ${1} > ${2}
170}
171
172# Perform one step in kallsyms generation, including temporary linking of
173# vmlinux.
174kallsyms_step()
175{
176	kallsymso_prev=${kallsymso}
177	kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
178	kallsymso=${kallsyms_vmlinux}.o
179	kallsyms_S=${kallsyms_vmlinux}.S
180
181	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
182	mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms ${kallsymso_prev}
183	kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
184
185	info AS ${kallsyms_S}
186	${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
187	      ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
188	      -c -o ${kallsymso} ${kallsyms_S}
189}
190
191# Create map file with all symbols from ${1}
192# See mksymap for additional details
193mksysmap()
194{
195	info NM ${2}
196	${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2} ${3}
197}
198
199sorttable()
200{
201	${objtree}/scripts/sorttable ${1}
202}
203
204# Delete output files in case of error
205cleanup()
206{
207	rm -f .btf.*
208	rm -f System.map
209	rm -f vmlinux
210	rm -f vmlinux.map
211}
212
213# Use "make V=1" to debug this script
214case "${KBUILD_VERBOSE}" in
215*1*)
216	set -x
217	;;
218esac
219
220if [ "$1" = "clean" ]; then
221	cleanup
222	exit 0
223fi
224
225${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
226
227btf_vmlinux_bin_o=""
228if is_enabled CONFIG_DEBUG_INFO_BTF; then
229	btf_vmlinux_bin_o=.btf.vmlinux.bin.o
230	if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
231		echo >&2 "Failed to generate BTF for vmlinux"
232		echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
233		exit 1
234	fi
235fi
236
237kallsymso=""
238kallsymso_prev=""
239kallsyms_vmlinux=""
240if is_enabled CONFIG_KALLSYMS; then
241
242	# kallsyms support
243	# Generate section listing all symbols and add it into vmlinux
244	# It's a three step process:
245	# 1)  Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
246	#     but __kallsyms is empty.
247	#     Running kallsyms on that gives us .tmp_kallsyms1.o with
248	#     the right size
249	# 2)  Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of
250	#     the right size, but due to the added section, some
251	#     addresses have shifted.
252	#     From here, we generate a correct .tmp_vmlinux.kallsyms2.o
253	# 3)  That link may have expanded the kernel image enough that
254	#     more linker branch stubs / trampolines had to be added, which
255	#     introduces new names, which further expands kallsyms. Do another
256	#     pass if that is the case. In theory it's possible this results
257	#     in even more stubs, but unlikely.
258	#     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
259	#     other bugs.
260	# 4)  The correct ${kallsymso} is linked into the final vmlinux.
261	#
262	# a)  Verify that the System.map from vmlinux matches the map from
263	#     ${kallsymso}.
264
265	kallsyms_step 1
266	kallsyms_step 2
267
268	# step 3
269	size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
270	size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
271
272	if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
273		kallsyms_step 3
274	fi
275fi
276
277vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
278
279# fill in BTF IDs
280if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
281	info BTFIDS vmlinux
282	${RESOLVE_BTFIDS} vmlinux
283fi
284
285mksysmap vmlinux System.map ${kallsymso}
286
287if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
288	info SORTTAB vmlinux
289	if ! sorttable vmlinux; then
290		echo >&2 Failed to sort kernel tables
291		exit 1
292	fi
293fi
294
295# step a (see comment above)
296if is_enabled CONFIG_KALLSYMS; then
297	if ! cmp -s System.map ${kallsyms_vmlinux}.syms; then
298		echo >&2 Inconsistent kallsyms data
299		echo >&2 'Try "make KALLSYMS_EXTRA_PASS=1" as a workaround'
300		exit 1
301	fi
302fi
303
304# For fixdep
305echo "vmlinux: $0" > .vmlinux.d