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?
19 # List of files to link:
20 # $l_list == --start-group -llib1 -llib2 --end-group
21 # --start-group $O_FILES $A_FILES --end-group
23 # Shared library link:
24 # -shared self-explanatory
25 # -fPIC position-independent code
26 # --enable-new-dtags ?
28 # -soname="libbusybox.so.$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."
40 printf "%s\n" "Output of:" >$EXE.out
41 printf "%s\n" "$*" >>$EXE.out
42 printf "%s\n" "==========" >>$EXE.out
43 $debug && echo "Trying: $*"
49 tempname="$(mktemp tmp.XXXXXXXXXX)"
50 echo "int main(int argc,char**argv){return argv?argc:0;}" >"$tempname".c
51 # Can use "-o /dev/null", but older gcc tend to *unlink it* on failure! :(
52 # Was using "-xc /dev/null", but we need a valid C program.
53 $CC $CFLAGS $LDFLAGS $1 "$tempname".c -o "$tempname" >/dev/null 2>&1
55 rm -f "$tempname" "$tempname".c "$tempname".o
59 check_libc_is_glibc() {
60 tempname="$(mktemp tmp.XXXXXXXXXX)"
63 /* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */
64 #if defined(__GLIBC__) && !defined(__UCLIBC__)
68 ! $CC $CFLAGS "$tempname".c -c -o "$tempname".o >/dev/null 2>&1
70 rm -f "$tempname" "$tempname".c "$tempname".o
82 # The --sort-section option is not supported by older versions of ld
83 SORT_SECTION="-Wl,--sort-section,alignment"
84 if ! check_cc "-Wl,--sort-section,alignment"; then
85 echo "Your linker does not support --sort-section,alignment"
89 START_GROUP="-Wl,--start-group"
90 END_GROUP="-Wl,--end-group"
92 echo "-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose"
95 # gold may not support --sort-common (yet)
96 SORT_COMMON="-Wl,--sort-common"
97 if ! check_cc "-Wl,--sort-common"; then
98 echo "Your linker does not support --sort-common"
102 # Static linking against glibc produces buggy executables
103 # (glibc does not cope well with ld --gc-sections).
104 # See sources.redhat.com/bugzilla/show_bug.cgi?id=3400
105 # Note that glibc is unsuitable for static linking anyway.
106 # We are removing -Wl,--gc-sections from link command line.
107 GC_SECTIONS="-Wl,--gc-sections"
108 if (. ./.config && test x"$CONFIG_STATIC" = x"y") then
109 if check_libc_is_glibc; then
110 echo "Static linking against glibc, can't use --gc-sections"
114 # The --gc-sections option is not supported by older versions of ld
115 if test -n "$GC_SECTIONS"; then
116 if ! check_cc "$GC_SECTIONS"; then
117 echo "Your linker does not support $GC_SECTIONS"
122 # Sanitize lib list (dups, extra spaces etc)
123 LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs`
125 # First link with all libs. If it fails, bail out
126 echo "Trying libraries: $LDLIBS"
127 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
128 l_list=`echo " $LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g'`
129 test "x$l_list" != "x" && l_list="$START_GROUP $l_list $END_GROUP"
130 try $CC $CFLAGS $LDFLAGS \
135 $START_GROUP $O_FILES $A_FILES $END_GROUP \
138 echo "Failed: $l_list"
140 echo 'Note: if build needs additional libraries, put them in CONFIG_EXTRA_LDLIBS.'
141 echo 'Example: CONFIG_EXTRA_LDLIBS="pthread dl tirpc audit pam"'
145 # Now try to remove each lib and build without it.
146 # Stop when no lib can be removed.
147 while test "$LDLIBS"; do
148 $debug && echo "Trying libraries: $LDLIBS"
149 dropped_non_first_lib=false
151 for one in $LDLIBS; do
152 without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs`
153 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3"
154 l_list=`echo " $without_one " | sed -e 's: \([^- ][^ ]*\): -l\1:g'`
155 test x"$l_list" != x"" && l_list="$START_GROUP $l_list $END_GROUP"
156 $debug && echo "Trying -l options: '$l_list'"
157 try $CC $CFLAGS $LDFLAGS \
162 $START_GROUP $O_FILES $A_FILES $END_GROUP \
165 echo " Library $one is not needed, excluding it"
166 LDLIBS="$without_one"
167 $first_lib || dropped_non_first_lib=true
169 echo " Library $one is needed, can't exclude it (yet)"
173 # We can stop trying to drop libs if either all libs were needed,
174 # or we excluded only the _first_ few.
175 # (else: we dropped some intermediate lib(s), maybe now we can succeed
176 # in dropping some of the preceding ones)
177 $dropped_non_first_lib || break
180 # Make the binary with final, minimal list of libs
181 echo "Final link with: ${LDLIBS:-<none>}"
182 l_list=`echo " $LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g'`
183 test "x$l_list" != "x" && l_list="$START_GROUP $l_list $END_GROUP"
184 # --verbose gives us gobs of info to stdout (e.g. linker script used)
185 if ! test -f busybox_ldscript; then
186 try $CC $CFLAGS $LDFLAGS \
191 $START_GROUP $O_FILES $A_FILES $END_GROUP \
199 echo "Custom linker script 'busybox_ldscript' found, using it"
200 # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out):
201 # .rodata : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) }
202 # *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*)
203 # *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*)
204 # This will eliminate most of the padding (~3kb).
205 # Hmm, "ld --sort-section alignment" should do it too.
207 # There is a ld hack which is meant to decrease disk usage
208 # at the cost of more RAM usage (??!!) in standard ld script:
209 # /* Adjust the address for the data segment. We want to adjust up to
210 # the same address within the page on the next page up. */
211 # . = ALIGN (0x1000) - ((0x1000 - .) & (0x1000 - 1)); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000);
213 # . = ALIGN (0x1000); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000);
214 # to unconditionally align .data to the next page boundary,
215 # instead of "next page, plus current offset in this page"
216 try $CC $CFLAGS $LDFLAGS \
221 -Wl,-T,busybox_ldscript \
222 $START_GROUP $O_FILES $A_FILES $END_GROUP \
233 sharedlib_dir="0_lib"
235 if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
236 mkdir "$sharedlib_dir" 2>/dev/null
237 test -d "$sharedlib_dir" || {
238 echo "Cannot make directory $sharedlib_dir"
241 ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
243 # Yes, "ld -shared -static" is a thing. It's a shared library which is itself static.
245 test "$CONFIG_FEATURE_LIBBUSYBOX_STATIC" = y && LBB_STATIC="-Wl,-static"
247 EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
248 try $CC $CFLAGS $LDFLAGS \
250 -shared -fPIC $LBB_STATIC \
251 -Wl,--enable-new-dtags \
253 -Wl,-soname="libbusybox.so.$BB_VER" \
254 -Wl,--undefined=lbb_main \
257 $START_GROUP $A_FILES $END_GROUP \
261 echo "Linking $EXE failed"
265 $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER"
266 chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER"
267 echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER"
270 if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
271 EXE="$sharedlib_dir/busybox_unstripped"
272 try $CC $CFLAGS $LDFLAGS \
277 $START_GROUP $O_FILES $END_GROUP \
278 -L"$sharedlib_dir" -lbusybox \
282 echo "Linking $EXE failed"
286 $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox"
287 echo "busybox linked against libbusybox: $sharedlib_dir/busybox"
290 if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then
291 echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)"
292 gcc -DNAME_MAIN -E -include include/autoconf.h include/applets.h \
296 while read name main junk; do
299 void lbb_prepare(const char *applet, char **argv);
300 int $main(int argc, char **argv);
302 int main(int argc, char **argv)
304 lbb_prepare(\"$name\", argv);
305 return $main(argc, argv);
307 " >"$sharedlib_dir/applet.c"
309 EXE="$sharedlib_dir/$name"
310 try $CC $CFLAGS $LDFLAGS "$sharedlib_dir/applet.c" \
315 -L"$sharedlib_dir" -lbusybox \
318 echo "Linking $EXE failed"
322 rm -- "$sharedlib_dir/applet.c" $EXE.out
323 $STRIP -s --remove-section=.note --remove-section=.comment $EXE
324 # Let user see that we do something - list the names of created binaries:
330 # libbusybox.so is needed only for -lbusybox at link time,
331 # it is not needed at runtime. Deleting to reduce confusion.
332 rm "$sharedlib_dir"/libbusybox.so 2>/dev/null
333 exit 0 # or else we may confuse make