#!/bin/sh debug=false # Linker flags used: # # Informational: # --warn-common # -Map $EXE.map # --verbose # # Optimizations: # --sort-common reduces padding # --sort-section alignment reduces padding # --gc-sections throws out unused sections, # does not work for shared libs # -On Not used, maybe useful? # # List of files to link: # $l_list == --start-group -llib1 -llib2 --end-group # --start-group $O_FILES $A_FILES --end-group # # Shared library link: # -shared self-explanatory # -fPIC position-independent code # --enable-new-dtags ? # -z,combreloc ? # -soname="libbusybox.so.$BB_VER" # --undefined=lbb_main Seed name to start pulling from # (otherwise we'll need --whole-archive) # -static Not used, but may be useful! manpage: # "... This option can be used with -shared. # Doing so means that a shared library # is being created but that all of the library's # external references must be resolved by pulling # in entries from static libraries." try() { printf "%s\n" "Output of:" >$EXE.out printf "%s\n" "$*" >>$EXE.out printf "%s\n" "==========" >>$EXE.out $debug && echo "Trying: $*" $@ >>$EXE.out 2>&1 return $? } check_cc() { local tempname="/tmp/temp.$$.$RANDOM" # Can use "-o /dev/null", but older gcc tend to *unlink it* on failure! :( # "-xc": C language. "/dev/null" is an empty source file. if $CC $1 -shared -xc /dev/null -o "$tempname".o >/dev/null 2>&1; then echo "$1"; else echo "$2"; fi rm "$tempname".o 2>/dev/null } check_libc_is_glibc() { local tempname="/tmp/temp.$$.$RANDOM" echo "\ #include <stdlib.h> /* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */ #if defined(__GLIBC__) && !defined(__UCLIBC__) syntax error here #endif " >"$tempname".c if $CC "$tempname".c -c -o "$tempname".o >/dev/null 2>&1; then echo "$2"; else echo "$1"; fi rm "$tempname".c "$tempname".o 2>/dev/null } EXE="$1" CC="$2" CFLAGS="$3" LDFLAGS="$4" O_FILES="$5" A_FILES="$6" LDLIBS="$7" # The --sort-section option is not supported by older versions of ld SORT_SECTION=`check_cc "-Wl,--sort-section,alignment" ""` START_GROUP="-Wl,--start-group" END_GROUP="-Wl,--end-group" INFO_OPTS="-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose" # gold may not support --sort-common (yet) SORT_COMMON=`check_cc "-Wl,--sort-common" ""` # Static linking against glibc produces buggy executables # (glibc does not cope well with ld --gc-sections). # See sources.redhat.com/bugzilla/show_bug.cgi?id=3400 # Note that glibc is unsuitable for static linking anyway. # We are removing -Wl,--gc-sections from link command line. GC_SECTIONS=`( . ./.config if test x"$CONFIG_STATIC" = x"y"; then check_libc_is_glibc "" "-Wl,--gc-sections" else echo "-Wl,--gc-sections" fi )` # The --gc-sections option is not supported by older versions of ld if test -n "$GC_SECTIONS"; then GC_SECTIONS=`check_cc "$GC_SECTIONS" ""` fi # Sanitize lib list (dups, extra spaces etc) LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs` # First link with all libs. If it fails, bail out echo "Trying libraries: $LDLIBS" # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3" l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'` test "x$l_list" != "x" && l_list="$START_GROUP $l_list $END_GROUP" try $CC $CFLAGS $LDFLAGS \ -o $EXE \ $SORT_COMMON \ $SORT_SECTION \ $GC_SECTIONS \ $START_GROUP $O_FILES $A_FILES $END_GROUP \ $l_list \ || { echo "Failed: $l_list" cat $EXE.out exit 1 } # Now try to remove each lib and build without it. # Stop when no lib can be removed. while test "$LDLIBS"; do $debug && echo "Trying libraries: $LDLIBS" all_needed=true last_needed=false for one in $LDLIBS; do without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs` # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3" l_list=`echo "$without_one" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'` test x"$l_list" != x"" && l_list="$START_GROUP $l_list $END_GROUP" $debug && echo "Trying -l options: '$l_list'" try $CC $CFLAGS $LDFLAGS \ -o $EXE \ $SORT_COMMON \ $SORT_SECTION \ $GC_SECTIONS \ $START_GROUP $O_FILES $A_FILES $END_GROUP \ $l_list if test $? = 0; then echo " Library $one is not needed, excluding it" LDLIBS="$without_one" all_needed=false last_needed=false else echo " Library $one is needed, can't exclude it (yet)" last_needed=true fi done # All libs were needed, can't remove any $all_needed && break # Optimization: was the last tried lib needed? if $last_needed; then # Was it the only one lib left? Don't test again then. { echo "$LDLIBS" | grep -q ' '; } || break fi done # Make the binary with final, minimal list of libs echo "Final link with: ${LDLIBS:-<none>}" l_list=`echo "$LDLIBS" | sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'` test "x$l_list" != "x" && l_list="$START_GROUP $l_list $END_GROUP" # --verbose gives us gobs of info to stdout (e.g. linker script used) if ! test -f busybox_ldscript; then try $CC $CFLAGS $LDFLAGS \ -o $EXE \ $SORT_COMMON \ $SORT_SECTION \ $GC_SECTIONS \ $START_GROUP $O_FILES $A_FILES $END_GROUP \ $l_list \ $INFO_OPTS \ || { cat $EXE.out exit 1 } else echo "Custom linker script 'busybox_ldscript' found, using it" # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out): # .rodata : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) } # *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*) # *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*) # This will eliminate most of the padding (~3kb). # Hmm, "ld --sort-section alignment" should do it too. try $CC $CFLAGS $LDFLAGS \ -o $EXE \ $SORT_COMMON \ $SORT_SECTION \ $GC_SECTIONS \ -Wl,-T,busybox_ldscript \ $START_GROUP $O_FILES $A_FILES $END_GROUP \ $l_list \ $INFO_OPTS \ || { cat $EXE.out exit 1 } fi . ./.config sharedlib_dir="0_lib" if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then mkdir "$sharedlib_dir" 2>/dev/null test -d "$sharedlib_dir" || { echo "Cannot make directory $sharedlib_dir" exit 1 } ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped" try $CC $CFLAGS $LDFLAGS \ -o $EXE \ -shared -fPIC \ -Wl,--enable-new-dtags \ -Wl,-z,combreloc \ -Wl,-soname="libbusybox.so.$BB_VER" \ -Wl,--undefined=lbb_main \ $SORT_COMMON \ $SORT_SECTION \ $START_GROUP $A_FILES $END_GROUP \ $l_list \ $INFO_OPTS \ || { echo "Linking $EXE failed" cat $EXE.out exit 1 } $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER" chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER" echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER" fi if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then EXE="$sharedlib_dir/busybox_unstripped" try $CC $CFLAGS $LDFLAGS \ -o $EXE \ $SORT_COMMON \ $SORT_SECTION \ $GC_SECTIONS \ $START_GROUP $O_FILES $END_GROUP \ -L"$sharedlib_dir" -lbusybox \ $INFO_OPTS \ || { echo "Linking $EXE failed" cat $EXE.out exit 1 } $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox" echo "busybox linked against libbusybox: $sharedlib_dir/busybox" fi if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)" gcc -DNAME_MAIN_CNAME -E -include include/autoconf.h include/applets.h \ | grep -v "^#" \ | grep -v "^$" \ > applet_lst.tmp while read name main junk; do echo "\ void lbb_prepare(const char *applet, char **argv); int $main(int argc, char **argv); int main(int argc, char **argv) { lbb_prepare(\"$name\", argv); return $main(argc, argv); } " >"$sharedlib_dir/applet.c" EXE="$sharedlib_dir/$name" try $CC $CFLAGS $LDFLAGS "$sharedlib_dir/applet.c" \ -o $EXE \ $SORT_COMMON \ $SORT_SECTION \ $GC_SECTIONS \ -L"$sharedlib_dir" -lbusybox \ -Wl,--warn-common \ || { echo "Linking $EXE failed" cat $EXE.out exit 1 } rm -- "$sharedlib_dir/applet.c" $EXE.out $STRIP -s --remove-section=.note --remove-section=.comment $EXE done <applet_lst.tmp fi # libbusybox.so is needed only for -lbusybox at link time, # it is not needed at runtime. Deleting to reduce confusion. rm "$sharedlib_dir"/libbusybox.so 2>/dev/null exit 0 # or else we may confuse make