scripts/trylink

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