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busybox/scripts/trylink

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#!/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: $*"
"$@" >>$EXE.out 2>&1
exitcode=$?
return $exitcode
}
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="$7"
# The --sort-section option is not supported by older versions of ld
SORT_SECTION=`check_cc "-Wl,--sort-section,alignment" ""`
# Static linking against glibc produces buggy executables
# (glibc does not cope well with ld --gc-sections).
# See sources.redhat.com/bugzilla/show_bug.cgi?id=3400
# Note that glibc is unsuitable for static linking anyway.
# We are removing -Wl,--gc-sections from link command line.
GC_SECTIONS=`(
. ./.config
if test x"$CONFIG_STATIC" = x"y"; then
check_libc_is_glibc "" "-Wl,--gc-sections"
else
echo "-Wl,--gc-sections"
fi
)`
# 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="-Wl,--start-group $l_list -Wl,--end-group"
try $CC $CFLAGS $LDFLAGS \
-o $EXE \
-Wl,--sort-common \
$SORT_SECTION \
$GC_SECTIONS \
-Wl,--start-group $O_FILES $A_FILES -Wl,--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
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="-Wl,--start-group $l_list -Wl,--end-group"
$debug && echo "Trying -l options: '$l_list'"
try $CC $CFLAGS $LDFLAGS \
-o $EXE \
-Wl,--sort-common \
$SORT_SECTION \
$GC_SECTIONS \
-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
$l_list
if test $? = 0; then
echo " Library $one is not needed"
LDLIBS="$without_one"
all_needed=false
else
echo " Library $one is needed"
fi
done
# All libs were needed, can't remove any
$all_needed && break
# If there is no space char, the list has just one lib.
# I'm not sure that in this case lib really is 100% needed.
# Let's try linking without it anyway... thus commented out.
#{ echo "$LDLIBS" | grep -q ' '; } || break
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="-Wl,--start-group $l_list -Wl,--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 \
-Wl,--sort-common \
$SORT_SECTION \
$GC_SECTIONS \
-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
$l_list \
-Wl,--warn-common \
-Wl,-Map -Wl,$EXE.map \
-Wl,--verbose \
|| {
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 \
-Wl,--sort-common \
$SORT_SECTION \
$GC_SECTIONS \
-Wl,-T -Wl,busybox_ldscript \
-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
$l_list \
-Wl,--warn-common \
-Wl,-Map -Wl,$EXE.map \
-Wl,--verbose \
|| {
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 \
-Wl,--sort-common \
$SORT_SECTION \
-Wl,--start-group $A_FILES -Wl,--end-group \
$l_list \
-Wl,--warn-common \
-Wl,-Map -Wl,$EXE.map \
-Wl,--verbose \
|| {
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 \
-Wl,--sort-common \
$SORT_SECTION \
$GC_SECTIONS \
-Wl,--start-group $O_FILES -Wl,--end-group \
-L"$sharedlib_dir" -lbusybox \
-Wl,--warn-common \
-Wl,-Map -Wl,$EXE.map \
-Wl,--verbose \
|| {
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 \
-Wl,--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
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