summaryrefslogtreecommitdiff
path: root/scripts/link-vmlinux.sh
blob: 3adef49250af979b22e3180ae05a8adb382a29b6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
#!/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 [ "${quiet}" != "silent_" ]; then
		printf "  %-7s %s\n" "${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}
}

objtool_link()
{
	local objtoolopt;

	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
		objtoolopt="check"
		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
			objtoolopt="${objtoolopt} --no-fp"
		fi
		if [ -n "${CONFIG_GCOV_KERNEL}" ]; 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 ${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

	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}
}

sorttable()
{
	${objtree}/scripts/sorttable ${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 need-builtin=1

#link vmlinux.o
info LD vmlinux.o
modpost_link vmlinux.o
objtool_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
${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
info GEN modules.builtin
# The second line aids cases where multiple modules share the same object.
tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin

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_TABLE_SORT}" ]; then
	info SORTTAB vmlinux
	if ! sorttable vmlinux; then
		echo >&2 Failed to sort kernel tables
		exit 1
	fi
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