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
29 set -e
30
31 LD="$1"
32 KBUILD_LDFLAGS="$2"
33 LDFLAGS_vmlinux="$3"
34
35 is_enabled() {
36 grep -q "^$1=y" include/config/auto.conf
37 }
38
39 # Nice output in kbuild format
40 # Will be supressed by "make -s"
41 info()
42 {
43 printf " %-7s %s\n" "${1}" "${2}"
44 }
45
46 # Link of vmlinux
47 # ${1} - output file
48 vmlinux_link()
49 {
50 local output=${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_MODULES; then
72 objs="${objs} .vmlinux.export.o"
73 fi
74
75 objs="${objs} init/version-timestamp.o"
76
77 if [ "${SRCARCH}" = "um" ]; then
78 wl=-Wl,
79 ld="${CC}"
80 ldflags="${CFLAGS_vmlinux}"
81 ldlibs="-lutil -lrt -lpthread"
82 else
83 wl=
84 ld="${LD}"
85 ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
86 ldlibs=
87 fi
88
89 ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
90
91 # The kallsyms linking does not need debug symbols included.
92 if [ -n "${strip_debug}" ] ; then
93 ldflags="${ldflags} ${wl}--strip-debug"
94 fi
95
96 if is_enabled CONFIG_VMLINUX_MAP; then
97 ldflags="${ldflags} ${wl}-Map=${output}.map"
98 fi
99
100 ${ld} ${ldflags} -o ${output} \
101 ${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
102 ${wl}--start-group ${libs} ${wl}--end-group \
103 ${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}
104 }
105
106 # generate .BTF typeinfo from DWARF debuginfo
107 # ${1} - vmlinux image
108 gen_btf()
109 {
110 local pahole_ver
111 local btf_data=${1}.btf.o
112
113 if ! [ -x "$(command -v ${PAHOLE})" ]; then
114 echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
115 return 1
116 fi
117
118 pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
119 if [ "${pahole_ver}" -lt "116" ]; then
120 echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.16"
121 return 1
122 fi
123
124 info BTF "${btf_data}"
125 LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
126
127 # Create ${btf_data} which contains just .BTF section but no symbols. Add
128 # SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
129 # deletes all symbols including __start_BTF and __stop_BTF, which will
130 # be redefined in the linker script. Add 2>/dev/null to suppress GNU
131 # objcopy warnings: "empty loadable segment detected at ..."
132 ${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
133 --strip-all ${1} "${btf_data}" 2>/dev/null
134 # Change e_type to ET_REL so that it can be used to link final vmlinux.
135 # GNU ld 2.35+ and lld do not allow an ET_EXEC input.
136 if is_enabled CONFIG_CPU_BIG_ENDIAN; then
137 et_rel='\0\1'
138 else
139 et_rel='\1\0'
140 fi
141 printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
142
143 btf_vmlinux_bin_o=${btf_data}
144 }
145
146 # Create ${2}.o file with all symbols from the ${1} object file
147 kallsyms()
148 {
149 local kallsymopt;
150
151 if is_enabled CONFIG_KALLSYMS_ALL; then
152 kallsymopt="${kallsymopt} --all-symbols"
153 fi
154
155 if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
156 kallsymopt="${kallsymopt} --absolute-percpu"
157 fi
158
159 info KSYMS "${2}.S"
160 scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
161
162 info AS "${2}.o"
163 ${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
164 ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
165
166 kallsymso=${2}.o
167 }
168
169 # Perform kallsyms for the given temporary vmlinux.
170 sysmap_and_kallsyms()
171 {
172 mksysmap "${1}" "${1}.syms"
173 kallsyms "${1}.syms" "${1}.kallsyms"
174
175 kallsyms_sysmap=${1}.syms
176 }
177
178 # Create map file with all symbols from ${1}
179 # See mksymap for additional details
180 mksysmap()
181 {
182 info NM ${2}
183 ${NM} -n "${1}" | sed -f "${srctree}/scripts/mksysmap" > "${2}"
184 }
185
186 sorttable()
187 {
188 ${objtree}/scripts/sorttable ${1}
189 }
190
191 cleanup()
192 {
193 rm -f .btf.*
194 rm -f System.map
195 rm -f vmlinux
196 rm -f vmlinux.map
197 }
198
199 # Use "make V=1" to debug this script
200 case "${KBUILD_VERBOSE}" in
201 *1*)
202 set -x
203 ;;
204 esac
205
206 if [ "$1" = "clean" ]; then
207 cleanup
208 exit 0
209 fi
210
211 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
212
213 btf_vmlinux_bin_o=
214 kallsymso=
215 strip_debug=
216
217 if is_enabled CONFIG_KALLSYMS; then
218 truncate -s0 .tmp_vmlinux.kallsyms0.syms
219 kallsyms .tmp_vmlinux.kallsyms0.syms .tmp_vmlinux0.kallsyms
220 fi
221
222 if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
223
224 # The kallsyms linking does not need debug symbols, but the BTF does.
225 if ! is_enabled CONFIG_DEBUG_INFO_BTF; then
226 strip_debug=1
227 fi
228
229 vmlinux_link .tmp_vmlinux1
230 fi
231
232 if is_enabled CONFIG_DEBUG_INFO_BTF; then
233 if ! gen_btf .tmp_vmlinux1; then
234 echo >&2 "Failed to generate BTF for vmlinux"
235 echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
236 exit 1
237 fi
238 fi
239
240 if is_enabled CONFIG_KALLSYMS; then
241
242 # kallsyms support
243 # Generate section listing all symbols and add it into vmlinux
244 # It's a four step process:
245 # 0) Generate a dummy __kallsyms with empty symbol list.
246 # 1) Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
247 # with a dummy __kallsyms.
248 # Running kallsyms on that gives us .tmp_kallsyms1.o with
249 # the right size
250 # 2) Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of
251 # the right size, but due to the added section, some
252 # addresses have shifted.
253 # From here, we generate a correct .tmp_vmlinux.kallsyms2.o
254 # 3) That link may have expanded the kernel image enough that
255 # more linker branch stubs / trampolines had to be added, which
256 # introduces new names, which further expands kallsyms. Do another
257 # pass if that is the case. In theory it's possible this results
258 # in even more stubs, but unlikely.
259 # KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
260 # other bugs.
261 # 4) The correct ${kallsymso} is linked into the final vmlinux.
262 #
263 # a) Verify that the System.map from vmlinux matches the map from
264 # ${kallsymso}.
265
266 # The kallsyms linking does not need debug symbols included.
267 strip_debug=1
268
269 sysmap_and_kallsyms .tmp_vmlinux1
270 size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
271
272 vmlinux_link .tmp_vmlinux2
273 sysmap_and_kallsyms .tmp_vmlinux2
274 size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
275
276 if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
277 vmlinux_link .tmp_vmlinux3
278 sysmap_and_kallsyms .tmp_vmlinux3
279 fi
280 fi
281
282 strip_debug=
283
284 vmlinux_link vmlinux
285
286 # fill in BTF IDs
287 if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
288 info BTFIDS vmlinux
289 ${RESOLVE_BTFIDS} vmlinux
290 fi
291
292 mksysmap vmlinux System.map
293
294 if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
295 info SORTTAB vmlinux
296 if ! sorttable vmlinux; then
297 echo >&2 Failed to sort kernel tables
298 exit 1
299 fi
300 fi
301
302 # step a (see comment above)
303 if is_enabled CONFIG_KALLSYMS; then
304 if ! cmp -s System.map "${kallsyms_sysmap}"; then
305 echo >&2 Inconsistent kallsyms data
306 echo >&2 'Try "make KALLSYMS_EXTRA_PASS=1" as a workaround'
307 exit 1
308 fi
309 fi
310
311 # For fixdep
312 echo "vmlinux: $0" > .vmlinux.d
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