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 # ${1} - output file
  48 vmlinux_link()
  49 {
  50         local output=${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 # ${1} - vmlinux image
 108 gen_btf()
 109 {
 110         local btf_data=${1}.btf.o
 111
 112         info BTF "${btf_data}"
 113         LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
 114
 115         # Create ${btf_data} which contains just .BTF section but no symbols. Add
 116         # SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
 117         # deletes all symbols including __start_BTF and __stop_BTF, which will
 118         # be redefined in the linker script. Add 2>/dev/null to suppress GNU
 119         # objcopy warnings: "empty loadable segment detected at ..."
 120         ${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
 121                 --strip-all ${1} "${btf_data}" 2>/dev/null
 122         # Change e_type to ET_REL so that it can be used to link final vmlinux.
 123         # GNU ld 2.35+ and lld do not allow an ET_EXEC input.
 124         if is_enabled CONFIG_CPU_BIG_ENDIAN; then
 125                 et_rel='\0\1'
 126         else
 127                 et_rel='\1\0'
 128         fi
 129         printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
 130
 131         btf_vmlinux_bin_o=${btf_data}
 132 }
 133
 134 # Create ${2}.o file with all symbols from the ${1} object file
 135 kallsyms()
 136 {
 137         local kallsymopt;
 138
 139         if is_enabled CONFIG_KALLSYMS_ALL; then
 140                 kallsymopt="${kallsymopt} --all-symbols"
 141         fi
 142
 143         if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
 144                 kallsymopt="${kallsymopt} --absolute-percpu"
 145         fi
 146
 147         info KSYMS "${2}.S"
 148         scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
 149
 150         info AS "${2}.o"
 151         ${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
 152               ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
 153
 154         kallsymso=${2}.o
 155 }
 156
 157 # Perform kallsyms for the given temporary vmlinux.
 158 sysmap_and_kallsyms()
 159 {
 160         mksysmap "${1}" "${1}.syms"
 161         kallsyms "${1}.syms" "${1}.kallsyms"
 162
 163         kallsyms_sysmap=${1}.syms
 164 }
 165
 166 # Create map file with all symbols from ${1}
 167 # See mksymap for additional details
 168 mksysmap()
 169 {
 170         info NM ${2}
 171         ${NM} -n "${1}" | sed -f "${srctree}/scripts/mksysmap" > "${2}"
 172 }
 173
 174 sorttable()
 175 {
 176         ${objtree}/scripts/sorttable ${1}
 177 }
 178
 179 cleanup()
 180 {
 181         rm -f .btf.*
 182         rm -f System.map
 183         rm -f vmlinux
 184         rm -f vmlinux.map
 185 }
 186
 187 # Use "make V=1" to debug this script
 188 case "${KBUILD_VERBOSE}" in
 189 *1*)
 190         set -x
 191         ;;
 192 esac
 193
 194 if [ "$1" = "clean" ]; then
 195         cleanup
 196         exit 0
 197 fi
 198
 199 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
 200
 201 btf_vmlinux_bin_o=
 202 kallsymso=
 203 strip_debug=
 204
 205 if is_enabled CONFIG_KALLSYMS; then
 206         true > .tmp_vmlinux.kallsyms0.syms
 207         kallsyms .tmp_vmlinux.kallsyms0.syms .tmp_vmlinux0.kallsyms
 208 fi
 209
 210 if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
 211
 212         # The kallsyms linking does not need debug symbols, but the BTF does.
 213         if ! is_enabled CONFIG_DEBUG_INFO_BTF; then
 214                 strip_debug=1
 215         fi
 216
 217         vmlinux_link .tmp_vmlinux1
 218 fi
 219
 220 if is_enabled CONFIG_DEBUG_INFO_BTF; then
 221         if ! gen_btf .tmp_vmlinux1; then
 222                 echo >&2 "Failed to generate BTF for vmlinux"
 223                 echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
 224                 exit 1
 225         fi
 226 fi
 227
 228 if is_enabled CONFIG_KALLSYMS; then
 229
 230         # kallsyms support
 231         # Generate section listing all symbols and add it into vmlinux
 232         # It's a four step process:
 233         # 0)  Generate a dummy __kallsyms with empty symbol list.
 234         # 1)  Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
 235         #     with a dummy __kallsyms.
 236         #     Running kallsyms on that gives us .tmp_kallsyms1.o with
 237         #     the right size
 238         # 2)  Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of
 239         #     the right size, but due to the added section, some
 240         #     addresses have shifted.
 241         #     From here, we generate a correct .tmp_vmlinux.kallsyms2.o
 242         # 3)  That link may have expanded the kernel image enough that
 243         #     more linker branch stubs / trampolines had to be added, which
 244         #     introduces new names, which further expands kallsyms. Do another
 245         #     pass if that is the case. In theory it's possible this results
 246         #     in even more stubs, but unlikely.
 247         #     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
 248         #     other bugs.
 249         # 4)  The correct ${kallsymso} is linked into the final vmlinux.
 250         #
 251         # a)  Verify that the System.map from vmlinux matches the map from
 252         #     ${kallsymso}.
 253
 254         # The kallsyms linking does not need debug symbols included.
 255         strip_debug=1
 256
 257         sysmap_and_kallsyms .tmp_vmlinux1
 258         size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
 259
 260         vmlinux_link .tmp_vmlinux2
 261         sysmap_and_kallsyms .tmp_vmlinux2
 262         size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
 263
 264         if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
 265                 vmlinux_link .tmp_vmlinux3
 266                 sysmap_and_kallsyms .tmp_vmlinux3
 267         fi
 268 fi
 269
 270 strip_debug=
 271
 272 vmlinux_link vmlinux
 273
 274 # fill in BTF IDs
 275 if is_enabled CONFIG_DEBUG_INFO_BTF; 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_sysmap}"; 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