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 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 # ${2}, ${3}, ... - optional extra .o files
  49 vmlinux_link()
  50 {
  51         local output=${1}
  52         local objs
  53         local libs
  54         local ld
  55         local ldflags
  56         local ldlibs
  57
  58         info LD ${output}
  59
  60         # skip output file argument
  61         shift
  62
  63         if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
  64                 # Use vmlinux.o instead of performing the slow LTO link again.
  65                 objs=vmlinux.o
  66                 libs=
  67         else
  68                 objs=vmlinux.a
  69                 libs="${KBUILD_VMLINUX_LIBS}"
  70         fi
  71
  72         if is_enabled CONFIG_MODULES; then
  73                 objs="${objs} .vmlinux.export.o"
  74         fi
  75
  76         objs="${objs} init/version-timestamp.o"
  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         if is_enabled CONFIG_LTO_CLANG; then
 160                 kallsymopt="${kallsymopt} --lto-clang"
 161         fi
 162
 163         info KSYMS ${2}
 164         scripts/kallsyms ${kallsymopt} ${1} > ${2}
 165 }
 166
 167 # Perform one step in kallsyms generation, including temporary linking of
 168 # vmlinux.
 169 kallsyms_step()
 170 {
 171         kallsymso_prev=${kallsymso}
 172         kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
 173         kallsymso=${kallsyms_vmlinux}.o
 174         kallsyms_S=${kallsyms_vmlinux}.S
 175
 176         vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
 177         mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms
 178         kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
 179
 180         info AS ${kallsyms_S}
 181         ${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
 182               ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
 183               -c -o ${kallsymso} ${kallsyms_S}
 184 }
 185
 186 # Create map file with all symbols from ${1}
 187 # See mksymap for additional details
 188 mksysmap()
 189 {
 190         info NM ${2}
 191         ${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
 192 }
 193
 194 sorttable()
 195 {
 196         ${objtree}/scripts/sorttable ${1}
 197 }
 198
 199 # Delete output files in case of error
 200 cleanup()
 201 {
 202         rm -f .btf.*
 203         rm -f System.map
 204         rm -f vmlinux
 205         rm -f vmlinux.map
 206 }
 207
 208 # Use "make V=1" to debug this script
 209 case "${KBUILD_VERBOSE}" in
 210 *1*)
 211         set -x
 212         ;;
 213 esac
 214
 215 if [ "$1" = "clean" ]; then
 216         cleanup
 217         exit 0
 218 fi
 219
 220 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
 221
 222 btf_vmlinux_bin_o=""
 223 if is_enabled CONFIG_DEBUG_INFO_BTF; then
 224         btf_vmlinux_bin_o=.btf.vmlinux.bin.o
 225         if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
 226                 echo >&2 "Failed to generate BTF for vmlinux"
 227                 echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
 228                 exit 1
 229         fi
 230 fi
 231
 232 kallsymso=""
 233 kallsymso_prev=""
 234 kallsyms_vmlinux=""
 235 if is_enabled CONFIG_KALLSYMS; then
 236
 237         # kallsyms support
 238         # Generate section listing all symbols and add it into vmlinux
 239         # It's a three step process:
 240         # 1)  Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
 241         #     but __kallsyms is empty.
 242         #     Running kallsyms on that gives us .tmp_kallsyms1.o with
 243         #     the right size
 244         # 2)  Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of
 245         #     the right size, but due to the added section, some
 246         #     addresses have shifted.
 247         #     From here, we generate a correct .tmp_vmlinux.kallsyms2.o
 248         # 3)  That link may have expanded the kernel image enough that
 249         #     more linker branch stubs / trampolines had to be added, which
 250         #     introduces new names, which further expands kallsyms. Do another
 251         #     pass if that is the case. In theory it's possible this results
 252         #     in even more stubs, but unlikely.
 253         #     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
 254         #     other bugs.
 255         # 4)  The correct ${kallsymso} is linked into the final vmlinux.
 256         #
 257         # a)  Verify that the System.map from vmlinux matches the map from
 258         #     ${kallsymso}.
 259
 260         kallsyms_step 1
 261         kallsyms_step 2
 262
 263         # step 3
 264         size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
 265         size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
 266
 267         if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
 268                 kallsyms_step 3
 269         fi
 270 fi
 271
 272 vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
 273
 274 # fill in BTF IDs
 275 if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
 276         info BTFIDS vmlinux
 277         ${RESOLVE_BTFIDS} vmlinux
 278 fi
 279
 280 mksysmap vmlinux System.map
 281
 282 if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
 283         info SORTTAB vmlinux
 284         if ! sorttable vmlinux; then
 285                 echo >&2 Failed to sort kernel tables
 286                 exit 1
 287         fi
 288 fi
 289
 290 # step a (see comment above)
 291 if is_enabled CONFIG_KALLSYMS; then
 292         if ! cmp -s System.map ${kallsyms_vmlinux}.syms; then
 293                 echo >&2 Inconsistent kallsyms data
 294                 echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
 295                 exit 1
 296         fi
 297 fi
 298
 299 # For fixdep
 300 echo "vmlinux: $0" > .vmlinux.d