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     return $?
  46 }
  47
  48 check_cc() {
  49     local tempname="/tmp/temp.$$.$RANDOM"
  50     # Can use "-o /dev/null", but older gcc tend to *unlink it* on failure! :(
  51     # "-xc": C language. "/dev/null" is an empty source file.
  52     if $CC $1 -shared -xc /dev/null -o "$tempname".o >/dev/null 2>&1; then
  53         echo "$1";
  54     else
  55         echo "$2";
  56     fi
  57     rm "$tempname".o 2>/dev/null
  58 }
  59
  60 check_libc_is_glibc() {
  61     local tempname="/tmp/temp.$$.$RANDOM"
  62     echo "\
  63         #include <stdlib.h>
  64         /* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */
  65         #if defined(__GLIBC__) && !defined(__UCLIBC__)
  66         syntax error here
  67         #endif
  68         " >"$tempname".c
  69     if $CC "$tempname".c -c -o "$tempname".o >/dev/null 2>&1; then
  70         echo "$2";
  71     else
  72         echo "$1";
  73     fi
  74     rm "$tempname".c "$tempname".o 2>/dev/null
  75 }
  76
  77 EXE="$1"
  78 CC="$2"
  79 CFLAGS="$3"
  80 LDFLAGS="$4"
  81 O_FILES="$5"
  82 A_FILES="$6"
  83 LDLIBS="$7"
  84
  85 # The --sort-section option is not supported by older versions of ld
  86 SORT_SECTION=`check_cc "-Wl,--sort-section,alignment" ""`
  87
  88 # Static linking against glibc produces buggy executables
  89 # (glibc does not cope well with ld --gc-sections).
  90 # See sources.redhat.com/bugzilla/show_bug.cgi?id=3400
  91 # Note that glibc is unsuitable for static linking anyway.
  92 # We are removing -Wl,--gc-sections from link command line.
  93 GC_SECTIONS=`(
  94 . ./.config
  95 if test x"$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 $CFLAGS $LDFLAGS \
 111         -o $EXE \
 112         -Wl,--sort-common \
 113         $SORT_SECTION \
 114         $GC_SECTIONS \
 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     last_needed=false
 129     for one in $LDLIBS; do
 130         without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
 131         # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 132         l_list=`echo "$without_one" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 133         test x"$l_list" != x"" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 134         $debug && echo "Trying -l options: '$l_list'"
 135         try $CC $CFLAGS $LDFLAGS \
 136                 -o $EXE \
 137                 -Wl,--sort-common \
 138                 $SORT_SECTION \
 139                 $GC_SECTIONS \
 140                 -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 141                 $l_list
 142         if test $? = 0; then
 143             echo " Library $one is not needed, excluding it"
 144             LDLIBS="$without_one"
 145             all_needed=false
 146             last_needed=false
 147         else
 148             echo " Library $one is needed, can't exclude it (yet)"
 149             last_needed=true
 150         fi
 151     done
 152     # All libs were needed, can't remove any
 153     $all_needed && break
 154     # Optimization: was the last tried lib needed?
 155     if $last_needed; then
 156         # Was it the only one lib left? Don't test again then.
 157         { echo "$LDLIBS" | grep -q ' '; } || break
 158     fi
 159 done
 160
 161 # Make the binary with final, minimal list of libs
 162 echo "Final link with: ${LDLIBS:-<none>}"
 163 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 164 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 165 # --verbose gives us gobs of info to stdout (e.g. linker script used)
 166 if ! test -f busybox_ldscript; then
 167     try $CC $CFLAGS $LDFLAGS \
 168             -o $EXE \
 169             -Wl,--sort-common \
 170             $SORT_SECTION \
 171             $GC_SECTIONS \
 172             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 173             $l_list \
 174             -Wl,--warn-common \
 175             -Wl,-Map,$EXE.map \
 176             -Wl,--verbose \
 177     || {
 178         cat $EXE.out
 179         exit 1
 180     }
 181 else
 182     echo "Custom linker script 'busybox_ldscript' found, using it"
 183     # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
 184     #  .rodata         : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
 185     #  *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
 186     #  *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
 187     # This will eliminate most of the padding (~3kb).
 188     # Hmm, "ld --sort-section alignment" should do it too.
 189     try $CC $CFLAGS $LDFLAGS \
 190             -o $EXE \
 191             -Wl,--sort-common \
 192             $SORT_SECTION \
 193             $GC_SECTIONS \
 194             -Wl,-T,busybox_ldscript \
 195             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 196             $l_list \
 197             -Wl,--warn-common \
 198             -Wl,-Map,$EXE.map \
 199             -Wl,--verbose \
 200     || {
 201         cat $EXE.out
 202         exit 1
 203     }
 204 fi
 205
 206 . ./.config
 207
 208 sharedlib_dir="0_lib"
 209
 210 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 211     mkdir "$sharedlib_dir" 2>/dev/null
 212     test -d "$sharedlib_dir" || {
 213         echo "Cannot make directory $sharedlib_dir"
 214         exit 1
 215     }
 216     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 217
 218     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
 219     try $CC $CFLAGS $LDFLAGS \
 220             -o $EXE \
 221             -shared -fPIC \
 222             -Wl,--enable-new-dtags \
 223             -Wl,-z,combreloc \
 224             -Wl,-soname="libbusybox.so.$BB_VER" \
 225             -Wl,--undefined=lbb_main \
 226             -Wl,--sort-common \
 227             $SORT_SECTION \
 228             -Wl,--start-group $A_FILES -Wl,--end-group \
 229             $l_list \
 230             -Wl,--warn-common \
 231             -Wl,-Map,$EXE.map \
 232             -Wl,--verbose \
 233     || {
 234         echo "Linking $EXE failed"
 235         cat $EXE.out
 236         exit 1
 237     }
 238     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
 239     chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
 240     echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
 241 fi
 242
 243 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 244     EXE="$sharedlib_dir/busybox_unstripped"
 245     try $CC $CFLAGS $LDFLAGS \
 246             -o $EXE \
 247             -Wl,--sort-common \
 248             $SORT_SECTION \
 249             $GC_SECTIONS \
 250             -Wl,--start-group $O_FILES -Wl,--end-group \
 251             -L"$sharedlib_dir" -lbusybox \
 252             -Wl,--warn-common \
 253             -Wl,-Map,$EXE.map \
 254             -Wl,--verbose \
 255     || {
 256         echo "Linking $EXE failed"
 257         cat $EXE.out
 258         exit 1
 259     }
 260     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
 261     echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
 262 fi
 263
 264 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
 265     echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
 266     gcc -DNAME_MAIN_CNAME -E -include include/autoconf.h include/applets.h \
 267     | grep -v "^#" \
 268     | grep -v "^$" \
 269     > applet_lst.tmp
 270     while read name main junk; do
 271
 272         echo "\
 273 void lbb_prepare(const char *applet, char **argv);
 274 int $main(int argc, char **argv);
 275
 276 int main(int argc, char **argv)
 277 {
 278         lbb_prepare(\"$name\", argv);
 279         return $main(argc, argv);
 280 }
 281 " >"$sharedlib_dir/applet.c"
 282
 283         EXE="$sharedlib_dir/$name"
 284         try $CC $CFLAGS $LDFLAGS "$sharedlib_dir/applet.c" \
 285                 -o $EXE \
 286                 -Wl,--sort-common \
 287                 $SORT_SECTION \
 288                 $GC_SECTIONS \
 289                 -L"$sharedlib_dir" -lbusybox \
 290                 -Wl,--warn-common \
 291         || {
 292             echo "Linking $EXE failed"
 293             cat $EXE.out
 294             exit 1
 295         }
 296         rm -- "$sharedlib_dir/applet.c" $EXE.out
 297         $STRIP -s --remove-section=.note --remove-section=.comment $EXE
 298
 299     done <applet_lst.tmp
 300 fi
 301
 302 # libbusybox.so is needed only for -lbusybox at link time,
 303 # it is not needed at runtime. Deleting to reduce confusion.
 304 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
 305 exit 0 # or else we may confuse make