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