scripts/link-vmlinux.sh

   1 #!/bin/sh
   2 # SPDX-License-Identifier: GPL-2.0
   3 #
   4 # link vmlinux
   5 #
   6 # vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_OBJS) and
   7 # $(KBUILD_VMLINUX_LIBS). Most are built-in.a files from top-level directories
   8 # in the kernel tree, others are specified in arch/$(ARCH)/Makefile.
   9 # $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
  10 # (not within --whole-archive), and do not require symbol indexes added.
  11 #
  12 # vmlinux
  13 #   ^
  14 #   |
  15 #   +--< $(KBUILD_VMLINUX_OBJS)
  16 #   |    +--< init/built-in.a drivers/built-in.a mm/built-in.a + more
  17 #   |
  18 #   +--< $(KBUILD_VMLINUX_LIBS)
  19 #   |    +--< lib/lib.a + more
  20 #   |
  21 #   +-< ${kallsymso} (see description in KALLSYMS section)
  22 #
  23 # vmlinux version (uname -v) cannot be updated during normal
  24 # descending-into-subdirs phase since we do not yet know if we need to
  25 # update vmlinux.
  26 # Therefore this step is delayed until just before final link of vmlinux.
  27 #
  28 # System.map is generated to document addresses of all kernel symbols
  29
  30 # Error out on error
  31 set -e
  32
  33 # Nice output in kbuild format
  34 # Will be supressed by "make -s"
  35 info()
  36 {
  37         if [ "${quiet}" != "silent_" ]; then
  38                 printf "  %-7s %s\n" "${1}" "${2}"
  39         fi
  40 }
  41
  42 # Link of vmlinux.o used for section mismatch analysis
  43 # ${1} output file
  44 modpost_link()
  45 {
  46         local objects
  47
  48         objects="--whole-archive                                \
  49                 ${KBUILD_VMLINUX_OBJS}                          \
  50                 --no-whole-archive                              \
  51                 --start-group                                   \
  52                 ${KBUILD_VMLINUX_LIBS}                          \
  53                 --end-group"
  54
  55         ${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
  56 }
  57
  58 # Link of vmlinux
  59 # ${1} - output file
  60 # ${2}, ${3}, ... - optional extra .o files
  61 vmlinux_link()
  62 {
  63         local lds="${objtree}/${KBUILD_LDS}"
  64         local output=${1}
  65         local objects
  66         local strip_debug
  67
  68         info LD ${output}
  69
  70         # skip output file argument
  71         shift
  72
  73         # The kallsyms linking does not need debug symbols included.
  74         if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
  75                 strip_debug=-Wl,--strip-debug
  76         fi
  77
  78         if [ "${SRCARCH}" != "um" ]; then
  79                 objects="--whole-archive                        \
  80                         ${KBUILD_VMLINUX_OBJS}                  \
  81                         --no-whole-archive                      \
  82                         --start-group                           \
  83                         ${KBUILD_VMLINUX_LIBS}                  \
  84                         --end-group                             \
  85                         ${@}"
  86
  87                 ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}      \
  88                         ${strip_debug#-Wl,}                     \
  89                         -o ${output}                            \
  90                         -T ${lds} ${objects}
  91         else
  92                 objects="-Wl,--whole-archive                    \
  93                         ${KBUILD_VMLINUX_OBJS}                  \
  94                         -Wl,--no-whole-archive                  \
  95                         -Wl,--start-group                       \
  96                         ${KBUILD_VMLINUX_LIBS}                  \
  97                         -Wl,--end-group                         \
  98                         ${@}"
  99
 100                 ${CC} ${CFLAGS_vmlinux}                         \
 101                         ${strip_debug}                          \
 102                         -o ${output}                            \
 103                         -Wl,-T,${lds}                           \
 104                         ${objects}                              \
 105                         -lutil -lrt -lpthread
 106                 rm -f linux
 107         fi
 108 }
 109
 110 # generate .BTF typeinfo from DWARF debuginfo
 111 # ${1} - vmlinux image
 112 # ${2} - file to dump raw BTF data into
 113 gen_btf()
 114 {
 115         local pahole_ver
 116
 117         if ! [ -x "$(command -v ${PAHOLE})" ]; then
 118                 echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
 119                 return 1
 120         fi
 121
 122         pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
 123         if [ "${pahole_ver}" -lt "113" ]; then
 124                 echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13"
 125                 return 1
 126         fi
 127
 128         vmlinux_link ${1}
 129
 130         info "BTF" ${2}
 131         LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
 132
 133         # Create ${2} which contains just .BTF section but no symbols. Add
 134         # SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
 135         # deletes all symbols including __start_BTF and __stop_BTF, which will
 136         # be redefined in the linker script. Add 2>/dev/null to suppress GNU
 137         # objcopy warnings: "empty loadable segment detected at ..."
 138         ${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
 139                 --strip-all ${1} ${2} 2>/dev/null
 140         # Change e_type to ET_REL so that it can be used to link final vmlinux.
 141         # Unlike GNU ld, lld does not allow an ET_EXEC input.
 142         printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none
 143 }
 144
 145 # Create ${2} .o file with all symbols from the ${1} object file
 146 kallsyms()
 147 {
 148         info KSYM ${2}
 149         local kallsymopt;
 150
 151         if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
 152                 kallsymopt="${kallsymopt} --all-symbols"
 153         fi
 154
 155         if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
 156                 kallsymopt="${kallsymopt} --absolute-percpu"
 157         fi
 158
 159         if [ -n "${CONFIG_KALLSYMS_BASE_RELATIVE}" ]; then
 160                 kallsymopt="${kallsymopt} --base-relative"
 161         fi
 162
 163         local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL}               \
 164                       ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"
 165
 166         local afile="`basename ${2} .o`.S"
 167
 168         ${NM} -n ${1} | scripts/kallsyms ${kallsymopt} > ${afile}
 169         ${CC} ${aflags} -c -o ${2} ${afile}
 170 }
 171
 172 # Perform one step in kallsyms generation, including temporary linking of
 173 # vmlinux.
 174 kallsyms_step()
 175 {
 176         kallsymso_prev=${kallsymso}
 177         kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
 178         kallsymso=${kallsyms_vmlinux}.o
 179
 180         vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
 181         kallsyms ${kallsyms_vmlinux} ${kallsymso}
 182 }
 183
 184 # Create map file with all symbols from ${1}
 185 # See mksymap for additional details
 186 mksysmap()
 187 {
 188         ${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
 189 }
 190
 191 sortextable()
 192 {
 193         ${objtree}/scripts/sortextable ${1}
 194 }
 195
 196 # Delete output files in case of error
 197 cleanup()
 198 {
 199         rm -f .btf.*
 200         rm -f .tmp_System.map
 201         rm -f .tmp_vmlinux*
 202         rm -f System.map
 203         rm -f vmlinux
 204         rm -f vmlinux.o
 205 }
 206
 207 on_exit()
 208 {
 209         if [ $? -ne 0 ]; then
 210                 cleanup
 211         fi
 212 }
 213 trap on_exit EXIT
 214
 215 on_signals()
 216 {
 217         exit 1
 218 }
 219 trap on_signals HUP INT QUIT TERM
 220
 221 #
 222 #
 223 # Use "make V=1" to debug this script
 224 case "${KBUILD_VERBOSE}" in
 225 *1*)
 226         set -x
 227         ;;
 228 esac
 229
 230 if [ "$1" = "clean" ]; then
 231         cleanup
 232         exit 0
 233 fi
 234
 235 # We need access to CONFIG_ symbols
 236 . include/config/auto.conf
 237
 238 # Update version
 239 info GEN .version
 240 if [ -r .version ]; then
 241         VERSION=$(expr 0$(cat .version) + 1)
 242         echo $VERSION > .version
 243 else
 244         rm -f .version
 245         echo 1 > .version
 246 fi;
 247
 248 # final build of init/
 249 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init
 250
 251 #link vmlinux.o
 252 info LD vmlinux.o
 253 modpost_link vmlinux.o
 254
 255 # modpost vmlinux.o to check for section mismatches
 256 ${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1
 257
 258 info MODINFO modules.builtin.modinfo
 259 ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
 260
 261 btf_vmlinux_bin_o=""
 262 if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
 263         btf_vmlinux_bin_o=.btf.vmlinux.bin.o
 264         if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
 265                 echo >&2 "Failed to generate BTF for vmlinux"
 266                 echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
 267                 exit 1
 268         fi
 269 fi
 270
 271 kallsymso=""
 272 kallsymso_prev=""
 273 kallsyms_vmlinux=""
 274 if [ -n "${CONFIG_KALLSYMS}" ]; then
 275
 276         # kallsyms support
 277         # Generate section listing all symbols and add it into vmlinux
 278         # It's a three step process:
 279         # 1)  Link .tmp_vmlinux1 so it has all symbols and sections,
 280         #     but __kallsyms is empty.
 281         #     Running kallsyms on that gives us .tmp_kallsyms1.o with
 282         #     the right size
 283         # 2)  Link .tmp_vmlinux2 so it now has a __kallsyms section of
 284         #     the right size, but due to the added section, some
 285         #     addresses have shifted.
 286         #     From here, we generate a correct .tmp_kallsyms2.o
 287         # 3)  That link may have expanded the kernel image enough that
 288         #     more linker branch stubs / trampolines had to be added, which
 289         #     introduces new names, which further expands kallsyms. Do another
 290         #     pass if that is the case. In theory it's possible this results
 291         #     in even more stubs, but unlikely.
 292         #     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
 293         #     other bugs.
 294         # 4)  The correct ${kallsymso} is linked into the final vmlinux.
 295         #
 296         # a)  Verify that the System.map from vmlinux matches the map from
 297         #     ${kallsymso}.
 298
 299         kallsyms_step 1
 300         kallsyms_step 2
 301
 302         # step 3
 303         size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
 304         size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
 305
 306         if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
 307                 kallsyms_step 3
 308         fi
 309 fi
 310
 311 vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
 312
 313 if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then
 314         info SORTEX vmlinux
 315         sortextable vmlinux
 316 fi
 317
 318 info SYSMAP System.map
 319 mksysmap vmlinux System.map
 320
 321 # step a (see comment above)
 322 if [ -n "${CONFIG_KALLSYMS}" ]; then
 323         mksysmap ${kallsyms_vmlinux} .tmp_System.map
 324
 325         if ! cmp -s System.map .tmp_System.map; then
 326                 echo >&2 Inconsistent kallsyms data
 327                 echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
 328                 exit 1
 329         fi
 330 fi