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     if $CC $1 -shared -o /dev/null -xc /dev/null > /dev/null 2>&1; then
  51         echo "$1";
  52     else
  53         echo "$2";
  54     fi
  55 }
  56
  57 EXE="$1"
  58 CC="$2"
  59 LDFLAGS="$3"
  60 O_FILES="$4"
  61 A_FILES="$5"
  62 LDLIBS="$6"
  63
  64 # The -Wl,--sort-section option is not supported by older versions of ld
  65 SORT_SECTION=`check_cc "-Wl,--sort-section -Wl,alignment" ""`
  66
  67 # Sanitize lib list (dups, extra spaces etc)
  68 LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs`
  69
  70 # First link with all libs. If it fails, bail out
  71 echo "Trying libraries: $LDLIBS"
  72 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
  73 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
  74 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
  75 try $CC $LDFLAGS \
  76         -o $EXE \
  77         -Wl,--sort-common \
  78         $SORT_SECTION \
  79         -Wl,--gc-sections \
  80         -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
  81         $l_list \
  82 || {
  83     echo "Failed: $* $l_list"
  84     cat $EXE.out
  85     exit 1
  86 }
  87
  88 # Now try to remove each lib and build without it.
  89 # Stop when no lib can be removed.
  90 while test "$LDLIBS"; do
  91     $debug && echo "Trying libraries: $LDLIBS"
  92     all_needed=true
  93     for one in $LDLIBS; do
  94         without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
  95         # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
  96         l_list=`echo "$without_one" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
  97         test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
  98         $debug && echo "Trying -l options: '$l_list'"
  99         try $CC $LDFLAGS \
 100                 -o $EXE \
 101                 -Wl,--sort-common \
 102                 $SORT_SECTION \
 103                 -Wl,--gc-sections \
 104                 -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 105                 $l_list
 106         if test $? = 0; then
 107             echo " Library $one is not needed"
 108             LDLIBS="$without_one"
 109             all_needed=false
 110         else
 111             echo " Library $one is needed"
 112         fi
 113     done
 114     # All libs were needed, can't remove any
 115     $all_needed && break
 116     # If there is no space char, the list has just one lib.
 117     # I'm not sure that in this case lib really is 100% needed.
 118     # Let's try linking without it anyway... thus commented out.
 119     #{ echo "$LDLIBS" | grep -q ' '; } || break
 120 done
 121
 122 # Make the binary with final, minimal list of libs
 123 echo "Final link with: ${LDLIBS:-<none>}"
 124 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 125 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 126 # --verbose gives us gobs of info to stdout (e.g. linker script used)
 127 if ! test -f busybox_ldscript; then
 128     try $CC $LDFLAGS \
 129             -o $EXE \
 130             -Wl,--sort-common \
 131             $SORT_SECTION \
 132             -Wl,--gc-sections \
 133             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 134             $l_list \
 135             -Wl,--warn-common \
 136             -Wl,-Map -Wl,$EXE.map \
 137             -Wl,--verbose \
 138     || {
 139         cat $EXE.out
 140         exit 1
 141     }
 142 else
 143     echo "Custom linker script 'busybox_ldscript' found, using it"
 144     # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
 145     #  .rodata         : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
 146     #  *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
 147     #  *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
 148     # This will eliminate most of the padding (~3kb).
 149     # Hmm, "ld --sort-section alignment" should do it too.
 150     try $CC $LDFLAGS \
 151             -o $EXE \
 152             -Wl,--sort-common \
 153             $SORT_SECTION \
 154             -Wl,--gc-sections \
 155             -Wl,-T -Wl,busybox_ldscript \
 156             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 157             $l_list \
 158             -Wl,--warn-common \
 159             -Wl,-Map -Wl,$EXE.map \
 160             -Wl,--verbose \
 161     || {
 162         cat $EXE.out
 163         exit 1
 164     }
 165 fi
 166
 167 . ./.config
 168
 169 sharedlib_dir="0_lib"
 170
 171 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 172     mkdir "$sharedlib_dir" 2>/dev/null
 173     test -d "$sharedlib_dir" || {
 174         echo "Cannot make directory $sharedlib_dir"
 175         exit 1
 176     }
 177     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 178
 179     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
 180     try $CC $LDFLAGS \
 181             -o $EXE \
 182             -shared -fPIC \
 183             -Wl,--enable-new-dtags \
 184             -Wl,-z,combreloc \
 185             -Wl,-soname="libbusybox.so.$BB_VER" \
 186             -Wl,--undefined=lbb_main \
 187             -Wl,--sort-common \
 188             $SORT_SECTION \
 189             -Wl,--start-group $A_FILES -Wl,--end-group \
 190             $l_list \
 191             -Wl,--warn-common \
 192             -Wl,-Map -Wl,$EXE.map \
 193             -Wl,--verbose \
 194     || {
 195         echo "Linking $EXE failed"
 196         cat $EXE.out
 197         exit 1
 198     }
 199     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
 200     chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
 201     echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
 202 fi
 203
 204 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 205     EXE="$sharedlib_dir/busybox_unstripped"
 206     try $CC $LDFLAGS \
 207             -o $EXE \
 208             -Wl,--sort-common \
 209             $SORT_SECTION \
 210             -Wl,--gc-sections \
 211             -Wl,--start-group $O_FILES -Wl,--end-group \
 212             -L"$sharedlib_dir" -lbusybox \
 213             -Wl,--warn-common \
 214             -Wl,-Map -Wl,$EXE.map \
 215             -Wl,--verbose \
 216     || {
 217         echo "Linking $EXE failed"
 218         cat $EXE.out
 219         exit 1
 220     }
 221     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
 222     echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
 223 fi
 224
 225 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
 226     echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
 227     gcc -DNAME_MAIN_CNAME -E -include include/autoconf.h include/applets.h \
 228     | grep -v "^#" \
 229     | grep -v "^$" \
 230     > applet_lst.tmp
 231     while read name main junk; do
 232
 233         echo "\
 234 void lbb_prepare(const char *applet, char **argv);
 235 int $main(int argc, char **argv);
 236
 237 int main(int argc, char **argv)
 238 {
 239         lbb_prepare(\"$name\", argv);
 240         return $main(argc, argv);
 241 }
 242 " >"$sharedlib_dir/applet.c"
 243
 244         EXE="$sharedlib_dir/$name"
 245         try $CC $LDFLAGS "$sharedlib_dir/applet.c" \
 246                 -o $EXE \
 247                 -Wl,--sort-common \
 248                 $SORT_SECTION \
 249                 -Wl,--gc-sections \
 250                 -L"$sharedlib_dir" -lbusybox \
 251                 -Wl,--warn-common \
 252         || {
 253             echo "Linking $EXE failed"
 254             cat $EXE.out
 255             exit 1
 256         }
 257         rm -- "$sharedlib_dir/applet.c" $EXE.out
 258         $STRIP -s --remove-section=.note --remove-section=.comment $EXE
 259
 260     done <applet_lst.tmp
 261 fi
 262
 263 # libbusybox.so is needed only for -lbusybox at link time,
 264 # it is not needed at runtime. Deleting to reduce confusion.
 265 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
 266 exit 0 # or else we may confuse make