scripts/trylink

   1 #!/bin/sh
   2
   3 #debug=true
   4 debug=false
   5
   6 # Linker flags used:
   7 #
   8 # Informational:
   9 # --warn-common
  10 # -Map $EXE.map
  11 # --verbose
  12 #
  13 # Optimizations:
  14 # --sort-common                 reduces padding
  15 # --sort-section alignment      reduces padding
  16 # --gc-sections                 throws out unused sections,
  17 #                               does not work for shared libs
  18 # -On                           Not used, maybe useful?
  19 #
  20 # List of files to link:
  21 # $l_list                       == --start-group -llib1 -llib2 --end-group
  22 # --start-group $O_FILES $A_FILES --end-group
  23 #
  24 # Shared library link:
  25 # -shared                       self-explanatory
  26 # -fPIC                         position-independent code
  27 # --enable-new-dtags            ?
  28 # -z,combreloc                  ?
  29 # -soname="libbusybox.so.$BB_VER"
  30 # --undefined=lbb_main          Seed name to start pulling from
  31 #                               (otherwise we'll need --whole-archive)
  32 # -static                       Not used, but may be useful! manpage:
  33 #                               "... This option can be used with -shared.
  34 #                               Doing so means that a shared library
  35 #                               is being created but that all of the library's
  36 #                               external references must be resolved by pulling
  37 #                               in entries from static libraries."
  38
  39
  40 try() {
  41     printf "%s\n" "Output of:" >$EXE.out
  42     printf "%s\n" "$*" >>$EXE.out
  43     printf "%s\n" "==========" >>$EXE.out
  44     $debug && echo "Trying: $*"
  45     $@ >>$EXE.out 2>&1
  46     return $?
  47 }
  48
  49 check_cc() {
  50     tempname="$(mktemp tmp.XXXXXXXXXX)"
  51     echo "int main(int argc,char**argv){return argv?argc:0;}" >"$tempname".c
  52     # Can use "-o /dev/null", but older gcc tend to *unlink it* on failure! :(
  53     # Was using "-xc /dev/null", but we need a valid C program.
  54     $CC $CFLAGS $LDFLAGS $1 "$tempname".c -o "$tempname" >/dev/null 2>&1
  55     exitcode=$?
  56     rm -f "$tempname" "$tempname".c "$tempname".o
  57     return $exitcode
  58 }
  59
  60 check_libc_is_glibc() {
  61     tempname="$(mktemp tmp.XXXXXXXXXX)"
  62     echo "\
  63         #include <stdlib.h>
  64         /* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */
  65         #if defined(__GLIBC__) && !defined(__UCLIBC__)
  66         syntax error here
  67         #endif
  68         " >"$tempname".c
  69     ! $CC $CFLAGS "$tempname".c -c -o "$tempname".o >/dev/null 2>&1
  70     exitcode=$?
  71     rm -f "$tempname" "$tempname".c "$tempname".o
  72     return $exitcode
  73 }
  74
  75 EXE="$1"
  76 CC="$2"
  77 CFLAGS="$3"
  78 LDFLAGS="$4"
  79 O_FILES="$5"
  80 A_FILES="$6"
  81 # We try to drop libraries from LDLIBS if build works without them,
  82 # but ones from CONFIG_EXTRA_LDLIBS are always linked in.
  83 # (For example, musl has stub utmp implementation, and if you link with
  84 # a real utmp library in LDLIBS, dropping it "works" but resulting binary
  85 # does not work properly).
  86 LDLIBS="$7"
  87 CONFIG_EXTRA_LDLIBS="$8"
  88
  89 # The --sort-section option is not supported by older versions of ld
  90 SORT_SECTION="-Wl,--sort-section,alignment"
  91 if ! check_cc "-Wl,--sort-section,alignment"; then
  92     echo "Your linker does not support --sort-section,alignment"
  93     SORT_SECTION=""
  94 fi
  95
  96 START_GROUP="-Wl,--start-group"
  97 END_GROUP="-Wl,--end-group"
  98 INFO_OPTS() {
  99         echo "-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose"
 100 }
 101
 102 # gold may not support --sort-common (yet)
 103 SORT_COMMON="-Wl,--sort-common"
 104 if ! check_cc "-Wl,--sort-common"; then
 105     echo "Your linker does not support --sort-common"
 106     SORT_COMMON=""
 107 fi
 108
 109 # Static linking against glibc produces buggy executables
 110 # (glibc does not cope well with ld --gc-sections).
 111 # See sources.redhat.com/bugzilla/show_bug.cgi?id=3400
 112 # Note that glibc is unsuitable for static linking anyway.
 113 # We are removing -Wl,--gc-sections from link command line.
 114 GC_SECTIONS="-Wl,--gc-sections"
 115 if (. ./.config && test x"$CONFIG_STATIC" = x"y") then
 116     if check_libc_is_glibc; then
 117         echo "Static linking against glibc, can't use --gc-sections"
 118         GC_SECTIONS=""
 119     fi
 120 fi
 121 # The --gc-sections option is not supported by older versions of ld
 122 if test -n "$GC_SECTIONS"; then
 123     if ! check_cc "$GC_SECTIONS"; then
 124         echo "Your linker does not support $GC_SECTIONS"
 125         GC_SECTIONS=""
 126     fi
 127 fi
 128
 129 # Sanitize lib list (dups, extra spaces etc)
 130 LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs`
 131
 132 # First link with all libs. If it fails, bail out
 133 echo "Trying libraries: $LDLIBS"
 134 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 135 l_list=`echo " $LDLIBS $CONFIG_EXTRA_LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g' -e 's/^ *//'`
 136 test x"$l_list" != x"" && l_list="$START_GROUP $l_list $END_GROUP"
 137 try $CC $CFLAGS $LDFLAGS \
 138         -o $EXE \
 139         $SORT_COMMON \
 140         $SORT_SECTION \
 141         $GC_SECTIONS \
 142         $START_GROUP $O_FILES $A_FILES $END_GROUP \
 143         $l_list \
 144 || {
 145     echo "Failed: $l_list"
 146     cat $EXE.out
 147     echo 'Note: if build needs additional libraries, put them in CONFIG_EXTRA_LDLIBS.'
 148     echo 'Example: CONFIG_EXTRA_LDLIBS="pthread dl tirpc audit pam"'
 149     exit 1
 150 }
 151
 152 # Now try to remove each lib and build without it.
 153 # Stop when no lib can be removed.
 154 while test "$LDLIBS"; do
 155     $debug && echo "Trying libraries: $LDLIBS"
 156     dropped_non_first_lib=false
 157     first_lib=true
 158     for one in $LDLIBS; do
 159         without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
 160         # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 161         l_list=`echo " $without_one $CONFIG_EXTRA_LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g' -e 's/^ *//'`
 162         test x"$l_list" != x"" && l_list="$START_GROUP $l_list $END_GROUP"
 163         $debug && echo "Trying -l options: '$l_list'"
 164         try $CC $CFLAGS $LDFLAGS \
 165                 -o $EXE \
 166                 $SORT_COMMON \
 167                 $SORT_SECTION \
 168                 $GC_SECTIONS \
 169                 $START_GROUP $O_FILES $A_FILES $END_GROUP \
 170                 $l_list
 171         if test $? = 0; then
 172             echo " Library $one is not needed, excluding it"
 173             LDLIBS="$without_one"
 174             $first_lib || dropped_non_first_lib=true
 175         else
 176             echo " Library $one is needed, can't exclude it (yet)"
 177             first_lib=false
 178         fi
 179     done
 180     # We can stop trying to drop libs if either all libs were needed,
 181     # or we excluded only the _first_ few.
 182     # (else: we dropped some intermediate lib(s), maybe now we can succeed
 183     # in dropping some of the preceding ones)
 184     $dropped_non_first_lib || break
 185 done
 186
 187 # Make the binary with final, minimal list of libs
 188 echo "Final link with: ${LDLIBS:-<none>}"
 189 l_list=`echo " $LDLIBS $CONFIG_EXTRA_LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g' -e 's/^ *//'`
 190 test x"$l_list" != x"" && l_list="$START_GROUP $l_list $END_GROUP"
 191 # --verbose gives us gobs of info to stdout (e.g. linker script used)
 192 if ! test -f busybox_ldscript; then
 193     try $CC $CFLAGS $LDFLAGS \
 194             -o $EXE \
 195             $SORT_COMMON \
 196             $SORT_SECTION \
 197             $GC_SECTIONS \
 198             $START_GROUP $O_FILES $A_FILES $END_GROUP \
 199             $l_list \
 200             `INFO_OPTS` \
 201     || {
 202         cat $EXE.out
 203         exit 1
 204     }
 205 else
 206     echo "Custom linker script 'busybox_ldscript' found, using it"
 207     # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
 208     #  .rodata         : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
 209     #  *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
 210     #  *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
 211     # This will eliminate most of the padding (~3kb).
 212     # Hmm, "ld --sort-section alignment" should do it too.
 213     #
 214     # There is a ld hack which is meant to decrease disk usage
 215     # at the cost of more RAM usage (??!!) in standard ld script:
 216     #  /* Adjust the address for the data segment.  We want to adjust up to
 217     #     the same address within the page on the next page up.  */
 218     #  . = ALIGN (0x1000) - ((0x1000 - .) & (0x1000 - 1)); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000);
 219     # Replace it with:
 220     #  . = ALIGN (0x1000); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000);
 221     # to unconditionally align .data to the next page boundary,
 222     # instead of "next page, plus current offset in this page"
 223     try $CC $CFLAGS $LDFLAGS \
 224             -o $EXE \
 225             $SORT_COMMON \
 226             $SORT_SECTION \
 227             $GC_SECTIONS \
 228             -Wl,-T,busybox_ldscript \
 229             $START_GROUP $O_FILES $A_FILES $END_GROUP \
 230             $l_list \
 231             `INFO_OPTS` \
 232     || {
 233         cat $EXE.out
 234         exit 1
 235     }
 236 fi
 237
 238 . ./.config
 239
 240 sharedlib_dir="0_lib"
 241
 242 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 243     mkdir "$sharedlib_dir" 2>/dev/null
 244     test -d "$sharedlib_dir" || {
 245         echo "Cannot make directory $sharedlib_dir"
 246         exit 1
 247     }
 248     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 249
 250     # Yes, "ld -shared -static" is a thing. It's a shared library which is itself static.
 251     LBB_STATIC=""
 252     test "$CONFIG_FEATURE_LIBBUSYBOX_STATIC" = y && LBB_STATIC="-Wl,-static"
 253
 254     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
 255     try $CC $CFLAGS $LDFLAGS \
 256             -o $EXE \
 257             -shared -fPIC $LBB_STATIC \
 258             -Wl,--enable-new-dtags \
 259             -Wl,-z,combreloc \
 260             -Wl,-soname="libbusybox.so.$BB_VER" \
 261             -Wl,--undefined=lbb_main \
 262             $SORT_COMMON \
 263             $SORT_SECTION \
 264             $START_GROUP $A_FILES $END_GROUP \
 265             $l_list \
 266             `INFO_OPTS` \
 267     || {
 268         echo "Linking $EXE failed"
 269         cat $EXE.out
 270         exit 1
 271     }
 272     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
 273     chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
 274     echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
 275 fi
 276
 277 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 278     EXE="$sharedlib_dir/busybox_unstripped"
 279     try $CC $CFLAGS $LDFLAGS \
 280             -o $EXE \
 281             $SORT_COMMON \
 282             $SORT_SECTION \
 283             $GC_SECTIONS \
 284             $START_GROUP $O_FILES $END_GROUP \
 285             -L"$sharedlib_dir" -lbusybox \
 286             $l_list \
 287             `INFO_OPTS` \
 288     || {
 289         echo "Linking $EXE failed"
 290         cat $EXE.out
 291         exit 1
 292     }
 293     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
 294     echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
 295 fi
 296
 297 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
 298     echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
 299     gcc -DNAME_MAIN -E -include include/autoconf.h include/applets.h \
 300     | grep -v "^#" \
 301     | grep -v "^ *$" \
 302     > applet_lst.tmp
 303     while read name main junk; do
 304
 305         echo "\
 306 void lbb_prepare(const char *applet, char **argv);
 307 int $main(int argc, char **argv);
 308
 309 int main(int argc, char **argv)
 310 {
 311         lbb_prepare(\"$name\", argv);
 312         return $main(argc, argv);
 313 }
 314 " >"$sharedlib_dir/applet.c"
 315
 316         EXE="$sharedlib_dir/$name"
 317         try $CC $CFLAGS $LDFLAGS "$sharedlib_dir/applet.c" \
 318                 -o $EXE \
 319                 $SORT_COMMON \
 320                 $SORT_SECTION \
 321                 $GC_SECTIONS \
 322                 -L"$sharedlib_dir" -lbusybox \
 323                 -Wl,--warn-common \
 324         || {
 325             echo "Linking $EXE failed"
 326             cat $EXE.out
 327             exit 1
 328         }
 329         rm -- "$sharedlib_dir/applet.c" $EXE.out
 330         $STRIP -s --remove-section=.note --remove-section=.comment $EXE
 331         # Let user see that we do something - list the names of created binaries:
 332         echo "$EXE"
 333
 334     done <applet_lst.tmp
 335 fi
 336
 337 # libbusybox.so is needed only for -lbusybox at link time,
 338 # it is not needed at runtime. Deleting to reduce confusion.
 339 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
 340 exit 0 # or else we may confuse make