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 check_libc_is_glibc() {
  58     local tempname="/tmp/temp.$$.$RANDOM.c"
  59     echo "\
  60         #include <stdlib.h>
  61         /* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */
  62         #if defined(__GLIBC__) && !defined(__UCLIBC__)
  63         syntax error here
  64         #endif
  65         " >"$tempname"
  66     if $CC "$tempname" -c -o /dev/null >/dev/null 2>&1; then
  67         echo "$2";
  68     else
  69         echo "$1";
  70     fi
  71     rm "$tempname"
  72 }
  73
  74 EXE="$1"
  75 CC="$2"
  76 LDFLAGS="$3"
  77 O_FILES="$4"
  78 A_FILES="$5"
  79 LDLIBS="$6"
  80
  81 # The -Wl,--sort-section option is not supported by older versions of ld
  82 SORT_SECTION=`check_cc "-Wl,--sort-section -Wl,alignment" ""`
  83
  84 # Static linking against glibc produces buggy executables
  85 # (glibc does not cope well with ld --gc-sections).
  86 # See sources.redhat.com/bugzilla/show_bug.cgi?id=3400
  87 # Note that glibc is unsuitable for static linking anyway.
  88 # We are removing -Wl,--gc-sections from link command line.
  89 GC_SECTION=`(
  90 . ./.config
  91 if test x"$CONFIG_STATIC" = x"y"; then
  92     check_libc_is_glibc "" "-Wl,--gc-sections"
  93 else
  94     echo "-Wl,--gc-sections"
  95 fi
  96 )`
  97
  98 # Sanitize lib list (dups, extra spaces etc)
  99 LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs`
 100
 101 # First link with all libs. If it fails, bail out
 102 echo "Trying libraries: $LDLIBS"
 103 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 104 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 105 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 106 try $CC $LDFLAGS \
 107         -o $EXE \
 108         -Wl,--sort-common \
 109         $SORT_SECTION \
 110         $GC_SECTION \
 111         -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 112         $l_list \
 113 || {
 114     echo "Failed: $* $l_list"
 115     cat $EXE.out
 116     exit 1
 117 }
 118
 119 # Now try to remove each lib and build without it.
 120 # Stop when no lib can be removed.
 121 while test "$LDLIBS"; do
 122     $debug && echo "Trying libraries: $LDLIBS"
 123     all_needed=true
 124     for one in $LDLIBS; do
 125         without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
 126         # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 127         l_list=`echo "$without_one" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 128         test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 129         $debug && echo "Trying -l options: '$l_list'"
 130         try $CC $LDFLAGS \
 131                 -o $EXE \
 132                 -Wl,--sort-common \
 133                 $SORT_SECTION \
 134                 $GC_SECTION \
 135                 -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 136                 $l_list
 137         if test $? = 0; then
 138             echo " Library $one is not needed"
 139             LDLIBS="$without_one"
 140             all_needed=false
 141         else
 142             echo " Library $one is needed"
 143         fi
 144     done
 145     # All libs were needed, can't remove any
 146     $all_needed && break
 147     # If there is no space char, the list has just one lib.
 148     # I'm not sure that in this case lib really is 100% needed.
 149     # Let's try linking without it anyway... thus commented out.
 150     #{ echo "$LDLIBS" | grep -q ' '; } || break
 151 done
 152
 153 # Make the binary with final, minimal list of libs
 154 echo "Final link with: ${LDLIBS:-<none>}"
 155 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 156 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 157 # --verbose gives us gobs of info to stdout (e.g. linker script used)
 158 if ! test -f busybox_ldscript; then
 159     try $CC $LDFLAGS \
 160             -o $EXE \
 161             -Wl,--sort-common \
 162             $SORT_SECTION \
 163             $GC_SECTION \
 164             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 165             $l_list \
 166             -Wl,--warn-common \
 167             -Wl,-Map -Wl,$EXE.map \
 168             -Wl,--verbose \
 169     || {
 170         cat $EXE.out
 171         exit 1
 172     }
 173 else
 174     echo "Custom linker script 'busybox_ldscript' found, using it"
 175     # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
 176     #  .rodata         : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
 177     #  *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
 178     #  *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
 179     # This will eliminate most of the padding (~3kb).
 180     # Hmm, "ld --sort-section alignment" should do it too.
 181     try $CC $LDFLAGS \
 182             -o $EXE \
 183             -Wl,--sort-common \
 184             $SORT_SECTION \
 185             $GC_SECTION \
 186             -Wl,-T -Wl,busybox_ldscript \
 187             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 188             $l_list \
 189             -Wl,--warn-common \
 190             -Wl,-Map -Wl,$EXE.map \
 191             -Wl,--verbose \
 192     || {
 193         cat $EXE.out
 194         exit 1
 195     }
 196 fi
 197
 198 . ./.config
 199
 200 sharedlib_dir="0_lib"
 201
 202 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 203     mkdir "$sharedlib_dir" 2>/dev/null
 204     test -d "$sharedlib_dir" || {
 205         echo "Cannot make directory $sharedlib_dir"
 206         exit 1
 207     }
 208     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 209
 210     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
 211     try $CC $LDFLAGS \
 212             -o $EXE \
 213             -shared -fPIC \
 214             -Wl,--enable-new-dtags \
 215             -Wl,-z,combreloc \
 216             -Wl,-soname="libbusybox.so.$BB_VER" \
 217             -Wl,--undefined=lbb_main \
 218             -Wl,--sort-common \
 219             $SORT_SECTION \
 220             -Wl,--start-group $A_FILES -Wl,--end-group \
 221             $l_list \
 222             -Wl,--warn-common \
 223             -Wl,-Map -Wl,$EXE.map \
 224             -Wl,--verbose \
 225     || {
 226         echo "Linking $EXE failed"
 227         cat $EXE.out
 228         exit 1
 229     }
 230     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
 231     chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
 232     echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
 233 fi
 234
 235 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 236     EXE="$sharedlib_dir/busybox_unstripped"
 237     try $CC $LDFLAGS \
 238             -o $EXE \
 239             -Wl,--sort-common \
 240             $SORT_SECTION \
 241             $GC_SECTION \
 242             -Wl,--start-group $O_FILES -Wl,--end-group \
 243             -L"$sharedlib_dir" -lbusybox \
 244             -Wl,--warn-common \
 245             -Wl,-Map -Wl,$EXE.map \
 246             -Wl,--verbose \
 247     || {
 248         echo "Linking $EXE failed"
 249         cat $EXE.out
 250         exit 1
 251     }
 252     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
 253     echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
 254 fi
 255
 256 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
 257     echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
 258     gcc -DNAME_MAIN_CNAME -E -include include/autoconf.h include/applets.h \
 259     | grep -v "^#" \
 260     | grep -v "^$" \
 261     > applet_lst.tmp
 262     while read name main junk; do
 263
 264         echo "\
 265 void lbb_prepare(const char *applet, char **argv);
 266 int $main(int argc, char **argv);
 267
 268 int main(int argc, char **argv)
 269 {
 270         lbb_prepare(\"$name\", argv);
 271         return $main(argc, argv);
 272 }
 273 " >"$sharedlib_dir/applet.c"
 274
 275         EXE="$sharedlib_dir/$name"
 276         try $CC $LDFLAGS "$sharedlib_dir/applet.c" \
 277                 -o $EXE \
 278                 -Wl,--sort-common \
 279                 $SORT_SECTION \
 280                 $GC_SECTION \
 281                 -L"$sharedlib_dir" -lbusybox \
 282                 -Wl,--warn-common \
 283         || {
 284             echo "Linking $EXE failed"
 285             cat $EXE.out
 286             exit 1
 287         }
 288         rm -- "$sharedlib_dir/applet.c" $EXE.out
 289         $STRIP -s --remove-section=.note --remove-section=.comment $EXE
 290
 291     done <applet_lst.tmp
 292 fi
 293
 294 # libbusybox.so is needed only for -lbusybox at link time,
 295 # it is not needed at runtime. Deleting to reduce confusion.
 296 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
 297 exit 0 # or else we may confuse make