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