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 # The --gc-sections option is not supported by older versions of ld
 103 if test -n "$GC_SECTIONS"; then
 104     GC_SECTIONS=`check_cc "$GC_SECTIONS" ""`
 105 fi
 106
 107 # Sanitize lib list (dups, extra spaces etc)
 108 LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs`
 109
 110 # First link with all libs. If it fails, bail out
 111 echo "Trying libraries: $LDLIBS"
 112 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 113 l_list=`echo "$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 try $CC $CFLAGS $LDFLAGS \
 116         -o $EXE \
 117         -Wl,--sort-common \
 118         $SORT_SECTION \
 119         $GC_SECTIONS \
 120         -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 121         $l_list \
 122 || {
 123     echo "Failed: $l_list"
 124     cat $EXE.out
 125     exit 1
 126 }
 127
 128 # Now try to remove each lib and build without it.
 129 # Stop when no lib can be removed.
 130 while test "$LDLIBS"; do
 131     $debug && echo "Trying libraries: $LDLIBS"
 132     all_needed=true
 133     last_needed=false
 134     for one in $LDLIBS; do
 135         without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
 136         # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
 137         l_list=`echo "$without_one" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 138         test x"$l_list" != x"" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 139         $debug && echo "Trying -l options: '$l_list'"
 140         try $CC $CFLAGS $LDFLAGS \
 141                 -o $EXE \
 142                 -Wl,--sort-common \
 143                 $SORT_SECTION \
 144                 $GC_SECTIONS \
 145                 -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 146                 $l_list
 147         if test $? = 0; then
 148             echo " Library $one is not needed, excluding it"
 149             LDLIBS="$without_one"
 150             all_needed=false
 151             last_needed=false
 152         else
 153             echo " Library $one is needed, can't exclude it (yet)"
 154             last_needed=true
 155         fi
 156     done
 157     # All libs were needed, can't remove any
 158     $all_needed && break
 159     # Optimization: was the last tried lib needed?
 160     if $last_needed; then
 161         # Was it the only one lib left? Don't test again then.
 162         { echo "$LDLIBS" | grep -q ' '; } || break
 163     fi
 164 done
 165
 166 # Make the binary with final, minimal list of libs
 167 echo "Final link with: ${LDLIBS:-<none>}"
 168 l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
 169 test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
 170 # --verbose gives us gobs of info to stdout (e.g. linker script used)
 171 if ! test -f busybox_ldscript; then
 172     try $CC $CFLAGS $LDFLAGS \
 173             -o $EXE \
 174             -Wl,--sort-common \
 175             $SORT_SECTION \
 176             $GC_SECTIONS \
 177             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 178             $l_list \
 179             -Wl,--warn-common \
 180             -Wl,-Map,$EXE.map \
 181             -Wl,--verbose \
 182     || {
 183         cat $EXE.out
 184         exit 1
 185     }
 186 else
 187     echo "Custom linker script 'busybox_ldscript' found, using it"
 188     # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
 189     #  .rodata         : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
 190     #  *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
 191     #  *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
 192     # This will eliminate most of the padding (~3kb).
 193     # Hmm, "ld --sort-section alignment" should do it too.
 194     try $CC $CFLAGS $LDFLAGS \
 195             -o $EXE \
 196             -Wl,--sort-common \
 197             $SORT_SECTION \
 198             $GC_SECTIONS \
 199             -Wl,-T,busybox_ldscript \
 200             -Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
 201             $l_list \
 202             -Wl,--warn-common \
 203             -Wl,-Map,$EXE.map \
 204             -Wl,--verbose \
 205     || {
 206         cat $EXE.out
 207         exit 1
 208     }
 209 fi
 210
 211 . ./.config
 212
 213 sharedlib_dir="0_lib"
 214
 215 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 216     mkdir "$sharedlib_dir" 2>/dev/null
 217     test -d "$sharedlib_dir" || {
 218         echo "Cannot make directory $sharedlib_dir"
 219         exit 1
 220     }
 221     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 222
 223     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
 224     try $CC $CFLAGS $LDFLAGS \
 225             -o $EXE \
 226             -shared -fPIC \
 227             -Wl,--enable-new-dtags \
 228             -Wl,-z,combreloc \
 229             -Wl,-soname="libbusybox.so.$BB_VER" \
 230             -Wl,--undefined=lbb_main \
 231             -Wl,--sort-common \
 232             $SORT_SECTION \
 233             -Wl,--start-group $A_FILES -Wl,--end-group \
 234             $l_list \
 235             -Wl,--warn-common \
 236             -Wl,-Map,$EXE.map \
 237             -Wl,--verbose \
 238     || {
 239         echo "Linking $EXE failed"
 240         cat $EXE.out
 241         exit 1
 242     }
 243     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
 244     chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
 245     echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
 246 fi
 247
 248 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 249     EXE="$sharedlib_dir/busybox_unstripped"
 250     try $CC $CFLAGS $LDFLAGS \
 251             -o $EXE \
 252             -Wl,--sort-common \
 253             $SORT_SECTION \
 254             $GC_SECTIONS \
 255             -Wl,--start-group $O_FILES -Wl,--end-group \
 256             -L"$sharedlib_dir" -lbusybox \
 257             -Wl,--warn-common \
 258             -Wl,-Map,$EXE.map \
 259             -Wl,--verbose \
 260     || {
 261         echo "Linking $EXE failed"
 262         cat $EXE.out
 263         exit 1
 264     }
 265     $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
 266     echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
 267 fi
 268
 269 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
 270     echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
 271     gcc -DNAME_MAIN_CNAME -E -include include/autoconf.h include/applets.h \
 272     | grep -v "^#" \
 273     | grep -v "^$" \
 274     > applet_lst.tmp
 275     while read name main junk; do
 276
 277         echo "\
 278 void lbb_prepare(const char *applet, char **argv);
 279 int $main(int argc, char **argv);
 280
 281 int main(int argc, char **argv)
 282 {
 283         lbb_prepare(\"$name\", argv);
 284         return $main(argc, argv);
 285 }
 286 " >"$sharedlib_dir/applet.c"
 287
 288         EXE="$sharedlib_dir/$name"
 289         try $CC $CFLAGS $LDFLAGS "$sharedlib_dir/applet.c" \
 290                 -o $EXE \
 291                 -Wl,--sort-common \
 292                 $SORT_SECTION \
 293                 $GC_SECTIONS \
 294                 -L"$sharedlib_dir" -lbusybox \
 295                 -Wl,--warn-common \
 296         || {
 297             echo "Linking $EXE failed"
 298             cat $EXE.out
 299             exit 1
 300         }
 301         rm -- "$sharedlib_dir/applet.c" $EXE.out
 302         $STRIP -s --remove-section=.note --remove-section=.comment $EXE
 303
 304     done <applet_lst.tmp
 305 fi
 306
 307 # libbusybox.so is needed only for -lbusybox at link time,
 308 # it is not needed at runtime. Deleting to reduce confusion.
 309 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
 310 exit 0 # or else we may confuse make