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 EXE="$1"
  50 CC="$2"
  51 LDFLAGS="$3"
  52 O_FILES="$4"
  53 A_FILES="$5"
  54 LDLIBS="$6"
  55
  56 # Sanitize lib list (dups, extra spaces etc)
  57 LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs`
  58
  59 # First link with all libs. If it fails, bail out
  60 echo "Trying libraries: $LDLIBS"
  61 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
  62 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
  63 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
  64 try $CC $LDFLAGS \
  65         -o $EXE \
  66         -Wl,--sort-common \
  67         -Wl,--sort-section -Wl,alignment \
  68         -Wl,--gc-sections \
  69         -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
  70         $l_list \
  71 || {
  72     echo "Failed: $* $l_list"
  73     cat $EXE.out
  74     exit 1
  75 }
  76
  77 # Now try to remove each lib and build without it.
  78 # Stop when no lib can be removed.
  79 while test "$LDLIBS"; do
  80     $debug && echo "Trying libraries: $LDLIBS"
  81     all_needed=true
  82     for one in $LDLIBS; do
  83         without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
  84         # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
  85         l_list=`echo "$without_one" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
  86         test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
  87         $debug && echo "Trying -l options: '$l_list'"
  88         try $CC $LDFLAGS \
  89                 -o $EXE \
  90                 -Wl,--sort-common \
  91                 -Wl,--sort-section -Wl,alignment \
  92                 -Wl,--gc-sections \
  93                 -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
  94                 $l_list
  95         if test $? = 0; then
  96             echo "Library $one is not needed"
  97             LDLIBS="$without_one"
  98             all_needed=false
  99         else
 100             echo "Library $one is needed"
 101         fi
 102     done
 103     # All libs were needed, can't remove any
 104     $all_needed && break
 105     # If there is no space char, the list has just one lib.
 106     # I'm not sure that in this case lib really is 100% needed.
 107     # Let's try linking without it anyway... thus commented out.
 108     #{ echo "$LDLIBS" | grep -q ' '; } || break
 109 done
 110
 111 # Make the binary with final, minimal list of libs
 112 echo "Final link with: $LDLIBS"
 113 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 114 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 115 # --verbose gives us gobs of info to stdout (e.g. linker script used)
 116 if ! test -f busybox_ldscript; then
 117     try $CC $LDFLAGS \
 118             -o $EXE \
 119             -Wl,--sort-common \
 120             -Wl,--sort-section -Wl,alignment \
 121             -Wl,--gc-sections \
 122             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 123             $l_list \
 124             -Wl,--warn-common \
 125             -Wl,-Map -Wl,$EXE.map \
 126             -Wl,--verbose \
 127     || {
 128         cat $EXE.out
 129         exit 1
 130     }
 131 else
 132     echo "Custom linker script 'busybox_ldscript' found, using it"
 133     # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
 134     #  .rodata         : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
 135     #  *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
 136     #  *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
 137     # This will eliminate most of the padding (~3kb).
 138     # Hmm, "ld --sort-section alignment" should do it too.
 139     try $CC $LDFLAGS \
 140             -o $EXE \
 141             -Wl,--sort-common \
 142             -Wl,--sort-section -Wl,alignment \
 143             -Wl,--gc-sections \
 144             -Wl,-T -Wl,busybox_ldscript \
 145             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 146             $l_list \
 147             -Wl,--warn-common \
 148             -Wl,-Map -Wl,$EXE.map \
 149             -Wl,--verbose \
 150     || {
 151         cat $EXE.out
 152         exit 1
 153     }
 154 fi
 155
 156 . ./.config
 157
 158 sharedlib_dir="0_lib"
 159
 160 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 161     mkdir "$sharedlib_dir" 2>/dev/null
 162     test -d "$sharedlib_dir" || {
 163         echo "Cannot make directory $sharedlib_dir"
 164         exit 1
 165     }
 166     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 167
 168     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
 169     try $CC $LDFLAGS \
 170             -o $EXE \
 171             -shared -fPIC \
 172             -Wl,--enable-new-dtags \
 173             -Wl,-z,combreloc \
 174             -Wl,-soname="libbusybox.so.$BB_VER" \
 175             -Wl,--undefined=lbb_main \
 176             -Wl,--sort-common \
 177             -Wl,--sort-section -Wl,alignment \
 178             -Wl,--start-group $A_FILES -Wl,--end-group \
 179             $l_list \
 180             -Wl,--warn-common \
 181             -Wl,-Map -Wl,$EXE.map \
 182             -Wl,--verbose \
 183     || {
 184         echo "Linking $EXE failed"
 185         cat $EXE.out
 186         exit 1
 187     }
 188     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
 189     chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
 190     echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
 191 fi
 192
 193 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 194     EXE="$sharedlib_dir/busybox_unstripped"
 195     try $CC $LDFLAGS \
 196             -o $EXE \
 197             -Wl,--sort-common \
 198             -Wl,--sort-section -Wl,alignment \
 199             -Wl,--gc-sections \
 200             -Wl,--start-group $O_FILES -Wl,--end-group \
 201             -L"$sharedlib_dir" -lbusybox \
 202             -Wl,--warn-common \
 203             -Wl,-Map -Wl,$EXE.map \
 204             -Wl,--verbose \
 205     || {
 206         echo "Linking $EXE failed"
 207         cat $EXE.out
 208         exit 1
 209     }
 210     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
 211     echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
 212 fi
 213
 214 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
 215     echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
 216     gcc -DNAME_MAIN_CNAME -E -include include/autoconf.h include/applets.h \
 217     | grep -v "^#" \
 218     | grep -v "^$" \
 219     > applet_lst.tmp
 220     while read name main junk; do
 221
 222         echo "\
 223 void lbb_prepare(const char *applet, char **argv);
 224 int $main(int argc, char **argv);
 225
 226 int main(int argc, char **argv)
 227 {
 228         lbb_prepare(\"$name\", argv);
 229         return $main(argc, argv);
 230 }
 231 " >"$sharedlib_dir/applet.c"
 232
 233         EXE="$sharedlib_dir/$name"
 234         try $CC $LDFLAGS "$sharedlib_dir/applet.c" \
 235                 -o $EXE \
 236                 -Wl,--sort-common \
 237                 -Wl,--sort-section -Wl,alignment \
 238                 -Wl,--gc-sections \
 239                 -L"$sharedlib_dir" -lbusybox \
 240                 -Wl,--warn-common \
 241         || {
 242             echo "Linking $EXE failed"
 243             cat $EXE.out
 244             exit 1
 245         }
 246         rm -- "$sharedlib_dir/applet.c" $EXE.out
 247         $STRIP -s --remove-section=.note --remove-section=.comment $EXE
 248
 249     done <applet_lst.tmp
 250 fi
 251
 252 # libbusybox.so is needed only for -lbusybox at link time,
 253 # it is not needed at runtime. Deleting to reduce confusion.
 254 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
 255 exit 0 # or else we may confuse make