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 LD="$1"
  34 KBUILD_LDFLAGS="$2"
  35 LDFLAGS_vmlinux="$3"
  36
  37 is_enabled() {
  38         grep -q "^$1=y" include/config/auto.conf
  39 }
  40
  41 # Nice output in kbuild format
  42 # Will be supressed by "make -s"
  43 info()
  44 {
  45         printf "  %-7s %s\n" "${1}" "${2}"
  46 }
  47
  48 # Link of vmlinux
  49 # ${1} - output file
  50 # ${2}, ${3}, ... - optional extra .o files
  51 vmlinux_link()
  52 {
  53         local output=${1}
  54         local objs
  55         local libs
  56         local ld
  57         local ldflags
  58         local ldlibs
  59
  60         info LD ${output}
  61
  62         # skip output file argument
  63         shift
  64
  65         if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
  66                 # Use vmlinux.o instead of performing the slow LTO link again.
  67                 objs=vmlinux.o
  68                 libs=
  69         else
  70                 objs="${KBUILD_VMLINUX_OBJS}"
  71                 libs="${KBUILD_VMLINUX_LIBS}"
  72         fi
  73
  74         if is_enabled CONFIG_MODULES; then
  75                 objs="${objs} .vmlinux.export.o"
  76         fi
  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 # ${2} - file to dump raw BTF data into
 110 gen_btf()
 111 {
 112         local pahole_ver
 113
 114         if ! [ -x "$(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} ${2} 2>/dev/null
 137         # Change e_type to ET_REL so that it can be used to link final vmlinux.
 138         # Unlike GNU ld, lld does not allow an ET_EXEC input.
 139         printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none
 140 }
 141
 142 # Create ${2} .S file with all symbols from the ${1} object file
 143 kallsyms()
 144 {
 145         local kallsymopt;
 146
 147         if is_enabled CONFIG_KALLSYMS_ALL; then
 148                 kallsymopt="${kallsymopt} --all-symbols"
 149         fi
 150
 151         if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
 152                 kallsymopt="${kallsymopt} --absolute-percpu"
 153         fi
 154
 155         if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
 156                 kallsymopt="${kallsymopt} --base-relative"
 157         fi
 158
 159         info KSYMS ${2}
 160         ${NM} -n ${1} | scripts/kallsyms ${kallsymopt} > ${2}
 161 }
 162
 163 # Perform one step in kallsyms generation, including temporary linking of
 164 # vmlinux.
 165 kallsyms_step()
 166 {
 167         kallsymso_prev=${kallsymso}
 168         kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
 169         kallsymso=${kallsyms_vmlinux}.o
 170         kallsyms_S=${kallsyms_vmlinux}.S
 171
 172         vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
 173         kallsyms ${kallsyms_vmlinux} ${kallsyms_S}
 174
 175         info AS ${kallsyms_S}
 176         ${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
 177               ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
 178               -c -o ${kallsymso} ${kallsyms_S}
 179 }
 180
 181 # Create map file with all symbols from ${1}
 182 # See mksymap for additional details
 183 mksysmap()
 184 {
 185         ${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
 186 }
 187
 188 sorttable()
 189 {
 190         ${objtree}/scripts/sorttable ${1}
 191 }
 192
 193 # Delete output files in case of error
 194 cleanup()
 195 {
 196         rm -f .btf.*
 197         rm -f System.map
 198         rm -f vmlinux
 199         rm -f vmlinux.map
 200         rm -f .vmlinux.objs
 201         rm -f .vmlinux.export.c
 202 }
 203
 204 # Use "make V=1" to debug this script
 205 case "${KBUILD_VERBOSE}" in
 206 *1*)
 207         set -x
 208         ;;
 209 esac
 210
 211 if [ "$1" = "clean" ]; then
 212         cleanup
 213         exit 0
 214 fi
 215
 216 # Update version
 217 info GEN .version
 218 if [ -r .version ]; then
 219         VERSION=$(expr 0$(cat .version) + 1)
 220         echo $VERSION > .version
 221 else
 222         rm -f .version
 223         echo 1 > .version
 224 fi;
 225
 226 # final build of init/
 227 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
 228
 229 #link vmlinux.o
 230 ${MAKE} -f "${srctree}/scripts/Makefile.vmlinux_o"
 231
 232 # Generate the list of in-tree objects in vmlinux
 233 #
 234 # This is used to retrieve symbol versions generated by genksyms.
 235 for f in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
 236         case ${f} in
 237         *libgcc.a)
 238                 # Some architectures do '$(CC) --print-libgcc-file-name' to
 239                 # borrow libgcc.a from the toolchain.
 240                 # There is no EXPORT_SYMBOL in external objects. Ignore this.
 241                 ;;
 242         *.a)
 243                 ${AR} t ${f} ;;
 244         *)
 245                 echo ${f} ;;
 246         esac
 247 done > .vmlinux.objs
 248
 249 # modpost vmlinux.o to check for section mismatches
 250 ${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1
 251
 252 info MODINFO modules.builtin.modinfo
 253 ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
 254 info GEN modules.builtin
 255 # The second line aids cases where multiple modules share the same object.
 256 tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
 257         tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin
 258
 259 if is_enabled CONFIG_MODULES; then
 260         ${MAKE} -f "${srctree}/scripts/Makefile.vmlinux" .vmlinux.export.o
 261 fi
 262
 263 btf_vmlinux_bin_o=""
 264 if is_enabled CONFIG_DEBUG_INFO_BTF; then
 265         btf_vmlinux_bin_o=.btf.vmlinux.bin.o
 266         if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
 267                 echo >&2 "Failed to generate BTF for vmlinux"
 268                 echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
 269                 exit 1
 270         fi
 271 fi
 272
 273 kallsymso=""
 274 kallsymso_prev=""
 275 kallsyms_vmlinux=""
 276 if is_enabled CONFIG_KALLSYMS; then
 277
 278         # kallsyms support
 279         # Generate section listing all symbols and add it into vmlinux
 280         # It's a three step process:
 281         # 1)  Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
 282         #     but __kallsyms is empty.
 283         #     Running kallsyms on that gives us .tmp_kallsyms1.o with
 284         #     the right size
 285         # 2)  Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of
 286         #     the right size, but due to the added section, some
 287         #     addresses have shifted.
 288         #     From here, we generate a correct .tmp_vmlinux.kallsyms2.o
 289         # 3)  That link may have expanded the kernel image enough that
 290         #     more linker branch stubs / trampolines had to be added, which
 291         #     introduces new names, which further expands kallsyms. Do another
 292         #     pass if that is the case. In theory it's possible this results
 293         #     in even more stubs, but unlikely.
 294         #     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
 295         #     other bugs.
 296         # 4)  The correct ${kallsymso} is linked into the final vmlinux.
 297         #
 298         # a)  Verify that the System.map from vmlinux matches the map from
 299         #     ${kallsymso}.
 300
 301         kallsyms_step 1
 302         kallsyms_step 2
 303
 304         # step 3
 305         size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
 306         size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
 307
 308         if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
 309                 kallsyms_step 3
 310         fi
 311 fi
 312
 313 vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
 314
 315 # fill in BTF IDs
 316 if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
 317         info BTFIDS vmlinux
 318         ${RESOLVE_BTFIDS} vmlinux
 319 fi
 320
 321 info SYSMAP System.map
 322 mksysmap vmlinux System.map
 323
 324 if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
 325         info SORTTAB vmlinux
 326         if ! sorttable vmlinux; then
 327                 echo >&2 Failed to sort kernel tables
 328                 exit 1
 329         fi
 330 fi
 331
 332 # step a (see comment above)
 333 if is_enabled CONFIG_KALLSYMS; then
 334         mksysmap ${kallsyms_vmlinux} .tmp_System.map
 335
 336         if ! cmp -s System.map .tmp_System.map; then
 337                 echo >&2 Inconsistent kallsyms data
 338                 echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
 339                 exit 1
 340         fi
 341 fi
 342
 343 # For fixdep
 344 echo "vmlinux: $0" > .vmlinux.d