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# ${1} - output file
 48vmlinux_link()
 49{
 50	local output=${1}
 51	local objs
 52	local libs
 53	local ld
 54	local ldflags
 55	local ldlibs
 56
 57	info LD ${output}
 58
 59	# skip output file argument
 60	shift
 61
 62	if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
 63		# Use vmlinux.o instead of performing the slow LTO link again.
 64		objs=vmlinux.o
 65		libs=
 66	else
 67		objs=vmlinux.a
 68		libs="${KBUILD_VMLINUX_LIBS}"
 69	fi
 70
 71	if is_enabled CONFIG_GENERIC_BUILTIN_DTB; then
 72		objs="${objs} .builtin-dtbs.o"
 73	fi
 74
 75	if is_enabled CONFIG_MODULES; then
 76		objs="${objs} .vmlinux.export.o"
 77	fi
 78
 79	objs="${objs} init/version-timestamp.o"
 80
 81	if [ "${SRCARCH}" = "um" ]; then
 82		wl=-Wl,
 83		ld="${CC}"
 84		ldflags="${CFLAGS_vmlinux}"
 85		ldlibs="-lutil -lrt -lpthread"
 86	else
 87		wl=
 88		ld="${LD}"
 89		ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
 90		ldlibs=
 91	fi
 92
 93	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
 94
 95	# The kallsyms linking does not need debug symbols included.
 96	if [ -n "${strip_debug}" ] ; then
 97		ldflags="${ldflags} ${wl}--strip-debug"
 98	fi
 99
100	if is_enabled CONFIG_VMLINUX_MAP; then
101		ldflags="${ldflags} ${wl}-Map=${output}.map"
102	fi
103
104	${ld} ${ldflags} -o ${output}					\
105		${wl}--whole-archive ${objs} ${wl}--no-whole-archive	\
106		${wl}--start-group ${libs} ${wl}--end-group		\
107		${kallsymso} ${btf_vmlinux_bin_o} ${arch_vmlinux_o} ${ldlibs}
108}
109
110# generate .BTF typeinfo from DWARF debuginfo
111# ${1} - vmlinux image
112gen_btf()
113{
114	local btf_data=${1}.btf.o
115
116	info BTF "${btf_data}"
117	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
118
119	# Create ${btf_data} which contains just .BTF section but no symbols. Add
120	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
121	# deletes all symbols including __start_BTF and __stop_BTF, which will
122	# be redefined in the linker script. Add 2>/dev/null to suppress GNU
123	# objcopy warnings: "empty loadable segment detected at ..."
124	${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
125		--strip-all ${1} "${btf_data}" 2>/dev/null
126	# Change e_type to ET_REL so that it can be used to link final vmlinux.
127	# GNU ld 2.35+ and lld do not allow an ET_EXEC input.
128	if is_enabled CONFIG_CPU_BIG_ENDIAN; then
129		et_rel='\0\1'
130	else
131		et_rel='\1\0'
132	fi
133	printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
134
135	btf_vmlinux_bin_o=${btf_data}
136}
137
138# Create ${2}.o file with all symbols from the ${1} object file
139kallsyms()
140{
141	local kallsymopt;
142
143	if is_enabled CONFIG_KALLSYMS_ALL; then
144		kallsymopt="${kallsymopt} --all-symbols"
145	fi
146
147	if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
148		kallsymopt="${kallsymopt} --absolute-percpu"
149	fi
150
151	info KSYMS "${2}.S"
152	scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
153
154	info AS "${2}.o"
155	${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
156	      ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
157
158	kallsymso=${2}.o
159}
160
161# Perform kallsyms for the given temporary vmlinux.
162sysmap_and_kallsyms()
163{
164	mksysmap "${1}" "${1}.syms"
165	kallsyms "${1}.syms" "${1}.kallsyms"
166
167	kallsyms_sysmap=${1}.syms
168}
169
170# Create map file with all symbols from ${1}
171# See mksymap for additional details
172mksysmap()
173{
174	info NM ${2}
175	${NM} -n "${1}" | sed -f "${srctree}/scripts/mksysmap" > "${2}"
176}
177
178sorttable()
179{
180	${objtree}/scripts/sorttable ${1}
181}
182
183cleanup()
184{
185	rm -f .btf.*
186	rm -f System.map
187	rm -f vmlinux
188	rm -f vmlinux.map
189}
190
191# Use "make V=1" to debug this script
192case "${KBUILD_VERBOSE}" in
193*1*)
194	set -x
195	;;
196esac
197
198if [ "$1" = "clean" ]; then
199	cleanup
200	exit 0
201fi
202
203${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
204
205arch_vmlinux_o=
206if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
207	arch_vmlinux_o=arch/${SRCARCH}/tools/vmlinux.arch.o
208fi
209
210btf_vmlinux_bin_o=
211kallsymso=
212strip_debug=
213
214if is_enabled CONFIG_KALLSYMS; then
215	true > .tmp_vmlinux0.syms
216	kallsyms .tmp_vmlinux0.syms .tmp_vmlinux0.kallsyms
217fi
218
219if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
220
221	# The kallsyms linking does not need debug symbols, but the BTF does.
222	if ! is_enabled CONFIG_DEBUG_INFO_BTF; then
223		strip_debug=1
224	fi
225
226	vmlinux_link .tmp_vmlinux1
227fi
228
229if is_enabled CONFIG_DEBUG_INFO_BTF; then
230	if ! gen_btf .tmp_vmlinux1; 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
237if is_enabled CONFIG_KALLSYMS; then
238
239	# kallsyms support
240	# Generate section listing all symbols and add it into vmlinux
241	# It's a four step process:
242	# 0)  Generate a dummy __kallsyms with empty symbol list.
243	# 1)  Link .tmp_vmlinux1.kallsyms so it has all symbols and sections,
244	#     with a dummy __kallsyms.
245	#     Running kallsyms on that gives us .tmp_vmlinux1.kallsyms.o with
246	#     the right size
247	# 2)  Link .tmp_vmlinux2.kallsyms so it now has a __kallsyms section of
248	#     the right size, but due to the added section, some
249	#     addresses have shifted.
250	#     From here, we generate a correct .tmp_vmlinux2.kallsyms.o
251	# 3)  That link may have expanded the kernel image enough that
252	#     more linker branch stubs / trampolines had to be added, which
253	#     introduces new names, which further expands kallsyms. Do another
254	#     pass if that is the case. In theory it's possible this results
255	#     in even more stubs, but unlikely.
256	#     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
257	#     other bugs.
258	# 4)  The correct ${kallsymso} is linked into the final vmlinux.
259	#
260	# a)  Verify that the System.map from vmlinux matches the map from
261	#     ${kallsymso}.
262
263	# The kallsyms linking does not need debug symbols included.
264	strip_debug=1
265
266	sysmap_and_kallsyms .tmp_vmlinux1
267	size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
268
269	vmlinux_link .tmp_vmlinux2
270	sysmap_and_kallsyms .tmp_vmlinux2
271	size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
272
273	if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
274		vmlinux_link .tmp_vmlinux3
275		sysmap_and_kallsyms .tmp_vmlinux3
276	fi
277fi
278
279strip_debug=
280
281vmlinux_link vmlinux
282
283# fill in BTF IDs
284if is_enabled CONFIG_DEBUG_INFO_BTF; then
285	info BTFIDS vmlinux
286	${RESOLVE_BTFIDS} vmlinux
287fi
288
289mksysmap vmlinux System.map
290
291if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
292	info SORTTAB vmlinux
293	if ! sorttable vmlinux; then
294		echo >&2 Failed to sort kernel tables
295		exit 1
296	fi
297fi
298
299# step a (see comment above)
300if is_enabled CONFIG_KALLSYMS; then
301	if ! cmp -s System.map "${kallsyms_sysmap}"; then
302		echo >&2 Inconsistent kallsyms data
303		echo >&2 'Try "make KALLSYMS_EXTRA_PASS=1" as a workaround'
304		exit 1
305	fi
306fi
307
308# For fixdep
309echo "vmlinux: $0" > .vmlinux.d