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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 $?
}
check_cc() {
tempname="$(mktemp tmp.XXXXXXXXXX)"
echo "int main(int argc,char**argv){return argv?argc:0;}" >"$tempname".c
# Can use "-o /dev/null", but older gcc tend to *unlink it* on failure! :(
# Was using "-xc /dev/null", but we need a valid C program.
# "eval" may be needed if CFLAGS can contain
# '... -D"BB_VER=KBUILD_STR(1.N.M)" ...'
# and we need shell to process quotes!
$CC $CFLAGS $LDFLAGS $1 "$tempname".c -o "$tempname" >/dev/null 2>&1
exitcode=$?
rm -f "$tempname" "$tempname".c "$tempname".o
return $exitcode
}
check_libc_is_glibc() {
tempname="$(mktemp tmp.XXXXXXXXXX)"
echo "\
#include <stdlib.h>
/* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */
#if defined(__GLIBC__) && !defined(__UCLIBC__)
syntax error here
#endif
" >"$tempname".c
! $CC $CFLAGS "$tempname".c -c -o "$tempname".o >/dev/null 2>&1
exitcode=$?
rm -f "$tempname" "$tempname".c "$tempname".o
return $exitcode
}
EXE="$1"
CC="$2"
CFLAGS="$3"
LDFLAGS="$4"
O_FILES="$5"
A_FILES="$6"
LDLIBS="$7"
# The --sort-section option is not supported by older versions of ld
SORT_SECTION="-Wl,--sort-section,alignment"
if ! check_cc "-Wl,--sort-section,alignment"; then
echo "Your linker does not support --sort-section,alignment"
SORT_SECTION=""
fi
START_GROUP="-Wl,--start-group"
END_GROUP="-Wl,--end-group"
INFO_OPTS() {
echo "-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose"
}
# gold may not support --sort-common (yet)
SORT_COMMON="-Wl,--sort-common"
if ! check_cc "-Wl,--sort-common"; then
echo "Your linker does not support --sort-common"
SORT_COMMON=""
fi
# 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="-Wl,--gc-sections"
if (. ./.config && test x"$CONFIG_STATIC" = x"y") then
if check_libc_is_glibc; then
echo "Static linking against glibc, can't use --gc-sections"
GC_SECTIONS=""
fi
fi
# The --gc-sections option is not supported by older versions of ld
if test -n "$GC_SECTIONS"; then
if ! check_cc "$GC_SECTIONS"; then
echo "Your linker does not support $GC_SECTIONS"
GC_SECTIONS=""
fi
fi
# Sanitize lib list (dups, extra spaces etc)
LDLIBS=`echo "$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\1:g'`
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 $EXE.out
echo 'Note: if build needs additional libraries, put them in CONFIG_EXTRA_LDLIBS.'
echo 'Example: CONFIG_EXTRA_LDLIBS="pthread dl tirpc audit pam"'
exit 1
}
# Now try to remove each lib and build without it.
# Stop when no lib can be removed.
while test "$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\1:g'`
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\1:g'`
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.
#
# There is a ld hack which is meant to decrease disk usage
# at the cost of more RAM usage (??!!) in standard ld script:
# /* Adjust the address for the data segment. We want to adjust up to
# the same address within the page on the next page up. */
# . = ALIGN (0x1000) - ((0x1000 - .) & (0x1000 - 1)); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000);
# Replace it with:
# . = ALIGN (0x1000); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000);
# to unconditionally align .data to the next page boundary,
# instead of "next page, plus current offset in this page"
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" "$sharedlib_dir"/libbusybox.so 2>/dev/null
# Yes, "ld -shared -static" is a thing. It's a shared library which is itself static.
LBB_STATIC=""
test "$CONFIG_FEATURE_LIBBUSYBOX_STATIC" = y && LBB_STATIC="-Wl,-static"
EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
try $CC $CFLAGS $LDFLAGS \
-o $EXE \
-shared -fPIC $LBB_STATIC \
-Wl,--enable-new-dtags \
-Wl,-z,combreloc \
-Wl,-soname="libbusybox.so.$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 \
$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/busybox"
echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
fi
if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
gcc -DNAME_MAIN -E -include include/autoconf.h include/applets.h \
| grep -v "^#" \
| grep -v "^ *$" \
> 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 $EXE
# Let user see that we do something - list the names of created binaries:
echo "$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
|