aboutsummaryrefslogtreecommitdiff
path: root/scripts/trylink
blob: 5994a757bc1a3fc35994f0a3528e7eb72695da4a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
#!/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