1#!/bin/sh 2 3debug=false 4 5# Linker flags used: 6# 7# Informational: 8# --warn-common 9# -Map $EXE.map 10# --verbose 11# 12# Optimizations: 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? 18# 19# List of files to link: 20# $l_list == --start-group -llib1 -llib2 --end-group 21# --start-group $O_FILES $A_FILES --end-group 22# 23# Shared library link: 24# -shared self-explanatory 25# -fPIC position-independent code 26# --enable-new-dtags ? 27# -z,combreloc ? 28# -soname="libbusybox.so.$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." 37 38 39try() { 40 printf "%s\n" "Output of:" >$EXE.out 41 printf "%s\n" "$*" >>$EXE.out 42 printf "%s\n" "==========" >>$EXE.out 43 $debug && echo "Trying: $*" 44 $@ >>$EXE.out 2>&1 45 return $? 46} 47 48check_cc() { 49 tempname="$(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 # "eval" may be needed if CFLAGS can contain 54 # '... -D"BB_VER=KBUILD_STR(1.N.M)" ...' 55 # and we need shell to process quotes! 56 $CC $CFLAGS $LDFLAGS $1 "$tempname".c -o "$tempname" >/dev/null 2>&1 57 exitcode=$? 58 rm -f "$tempname" "$tempname".c "$tempname".o 59 return $exitcode 60} 61 62check_libc_is_glibc() { 63 tempname="$(mktemp tmp.XXXXXXXXXX)" 64 echo "\ 65 #include <stdlib.h> 66 /* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */ 67 #if defined(__GLIBC__) && !defined(__UCLIBC__) 68 syntax error here 69 #endif 70 " >"$tempname".c 71 ! $CC $CFLAGS "$tempname".c -c -o "$tempname".o >/dev/null 2>&1 72 exitcode=$? 73 rm -f "$tempname" "$tempname".c "$tempname".o 74 return $exitcode 75} 76 77EXE="$1" 78CC="$2" 79CFLAGS="$3" 80LDFLAGS="$4" 81O_FILES="$5" 82A_FILES="$6" 83LDLIBS="$7" 84 85# The --sort-section option is not supported by older versions of ld 86SORT_SECTION="-Wl,--sort-section,alignment" 87if ! check_cc "-Wl,--sort-section,alignment"; then 88 echo "Your linker does not support --sort-section,alignment" 89 SORT_SECTION="" 90fi 91 92START_GROUP="-Wl,--start-group" 93END_GROUP="-Wl,--end-group" 94INFO_OPTS() { 95 echo "-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose" 96} 97 98# gold may not support --sort-common (yet) 99SORT_COMMON="-Wl,--sort-common" 100if ! check_cc "-Wl,--sort-common"; then 101 echo "Your linker does not support --sort-common" 102 SORT_COMMON="" 103fi 104 105# Static linking against glibc produces buggy executables 106# (glibc does not cope well with ld --gc-sections). 107# See sources.redhat.com/bugzilla/show_bug.cgi?id=3400 108# Note that glibc is unsuitable for static linking anyway. 109# We are removing -Wl,--gc-sections from link command line. 110GC_SECTIONS="-Wl,--gc-sections" 111if (. ./.config && test x"$CONFIG_STATIC" = x"y") then 112 if check_libc_is_glibc; then 113 echo "Static linking against glibc, can't use --gc-sections" 114 GC_SECTIONS="" 115 fi 116fi 117# The --gc-sections option is not supported by older versions of ld 118if test -n "$GC_SECTIONS"; then 119 if ! check_cc "$GC_SECTIONS"; then 120 echo "Your linker does not support $GC_SECTIONS" 121 GC_SECTIONS="" 122 fi 123fi 124 125# Sanitize lib list (dups, extra spaces etc) 126LDLIBS=`echo "$LDLIBS" | xargs -n1 | sort | uniq | xargs` 127 128# First link with all libs. If it fails, bail out 129echo "Trying libraries: $LDLIBS" 130# "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3" 131l_list=`echo " $LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g'` 132test "x$l_list" != "x" && l_list="$START_GROUP $l_list $END_GROUP" 133try $CC $CFLAGS $LDFLAGS \ 134 -o $EXE \ 135 $SORT_COMMON \ 136 $SORT_SECTION \ 137 $GC_SECTIONS \ 138 $START_GROUP $O_FILES $A_FILES $END_GROUP \ 139 $l_list \ 140|| { 141 echo "Failed: $l_list" 142 cat $EXE.out 143 echo 'Note: if build needs additional libraries, put them in CONFIG_EXTRA_LDLIBS.' 144 echo 'Example: CONFIG_EXTRA_LDLIBS="pthread dl tirpc audit pam"' 145 exit 1 146} 147 148# Now try to remove each lib and build without it. 149# Stop when no lib can be removed. 150while test "$LDLIBS"; do 151 $debug && echo "Trying libraries: $LDLIBS" 152 all_needed=true 153 last_needed=false 154 for one in $LDLIBS; do 155 without_one=`echo " $LDLIBS " | sed "s/ $one / /g" | xargs` 156 # "lib1 lib2 lib3" -> "-llib1 -llib2 -llib3" 157 l_list=`echo " $without_one " | sed -e 's: \([^- ][^ ]*\): -l\1:g'` 158 test x"$l_list" != x"" && l_list="$START_GROUP $l_list $END_GROUP" 159 $debug && echo "Trying -l options: '$l_list'" 160 try $CC $CFLAGS $LDFLAGS \ 161 -o $EXE \ 162 $SORT_COMMON \ 163 $SORT_SECTION \ 164 $GC_SECTIONS \ 165 $START_GROUP $O_FILES $A_FILES $END_GROUP \ 166 $l_list 167 if test $? = 0; then 168 echo " Library $one is not needed, excluding it" 169 LDLIBS="$without_one" 170 all_needed=false 171 last_needed=false 172 else 173 echo " Library $one is needed, can't exclude it (yet)" 174 last_needed=true 175 fi 176 done 177 # All libs were needed, can't remove any 178 $all_needed && break 179 # Optimization: was the last tried lib needed? 180 if $last_needed; then 181 # Was it the only one lib left? Don't test again then. 182 { echo "$LDLIBS" | grep -q ' '; } || break 183 fi 184done 185 186# Make the binary with final, minimal list of libs 187echo "Final link with: ${LDLIBS:-<none>}" 188l_list=`echo " $LDLIBS " | sed -e 's: \([^- ][^ ]*\): -l\1:g'` 189test "x$l_list" != "x" && l_list="$START_GROUP $l_list $END_GROUP" 190# --verbose gives us gobs of info to stdout (e.g. linker script used) 191if ! test -f busybox_ldscript; then 192 try $CC $CFLAGS $LDFLAGS \ 193 -o $EXE \ 194 $SORT_COMMON \ 195 $SORT_SECTION \ 196 $GC_SECTIONS \ 197 $START_GROUP $O_FILES $A_FILES $END_GROUP \ 198 $l_list \ 199 `INFO_OPTS` \ 200 || { 201 cat $EXE.out 202 exit 1 203 } 204else 205 echo "Custom linker script 'busybox_ldscript' found, using it" 206 # Add SORT_BY_ALIGNMENT to linker script (found in $EXE.out): 207 # .rodata : { *(.rodata SORT_BY_ALIGNMENT(.rodata.*) .gnu.linkonce.r.*) } 208 # *(.data SORT_BY_ALIGNMENT(.data.*) .gnu.linkonce.d.*) 209 # *(.bss SORT_BY_ALIGNMENT(.bss.*) .gnu.linkonce.b.*) 210 # This will eliminate most of the padding (~3kb). 211 # Hmm, "ld --sort-section alignment" should do it too. 212 # 213 # There is a ld hack which is meant to decrease disk usage 214 # at the cost of more RAM usage (??!!) in standard ld script: 215 # /* Adjust the address for the data segment. We want to adjust up to 216 # the same address within the page on the next page up. */ 217 # . = ALIGN (0x1000) - ((0x1000 - .) & (0x1000 - 1)); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000); 218 # Replace it with: 219 # . = ALIGN (0x1000); . = DATA_SEGMENT_ALIGN (0x1000, 0x1000); 220 # to unconditionally align .data to the next page boundary, 221 # instead of "next page, plus current offset in this page" 222 try $CC $CFLAGS $LDFLAGS \ 223 -o $EXE \ 224 $SORT_COMMON \ 225 $SORT_SECTION \ 226 $GC_SECTIONS \ 227 -Wl,-T,busybox_ldscript \ 228 $START_GROUP $O_FILES $A_FILES $END_GROUP \ 229 $l_list \ 230 `INFO_OPTS` \ 231 || { 232 cat $EXE.out 233 exit 1 234 } 235fi 236 237. ./.config 238 239sharedlib_dir="0_lib" 240 241if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then 242 mkdir "$sharedlib_dir" 2>/dev/null 243 test -d "$sharedlib_dir" || { 244 echo "Cannot make directory $sharedlib_dir" 245 exit 1 246 } 247 ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null 248 249 # Yes, "ld -shared -static" is a thing. It's a shared library which is itself static. 250 LBB_STATIC="" 251 test "$CONFIG_FEATURE_LIBBUSYBOX_STATIC" = y && LBB_STATIC="-Wl,-static" 252 253 EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped" 254 try $CC $CFLAGS $LDFLAGS \ 255 -o $EXE \ 256 -shared -fPIC $LBB_STATIC \ 257 -Wl,--enable-new-dtags \ 258 -Wl,-z,combreloc \ 259 -Wl,-soname="libbusybox.so.$BB_VER" \ 260 -Wl,--undefined=lbb_main \ 261 $SORT_COMMON \ 262 $SORT_SECTION \ 263 $START_GROUP $A_FILES $END_GROUP \ 264 $l_list \ 265 `INFO_OPTS` \ 266 || { 267 echo "Linking $EXE failed" 268 cat $EXE.out 269 exit 1 270 } 271 $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/libbusybox.so.$BB_VER" 272 chmod a+x "$sharedlib_dir/libbusybox.so.$BB_VER" 273 echo "libbusybox: $sharedlib_dir/libbusybox.so.$BB_VER" 274fi 275 276if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then 277 EXE="$sharedlib_dir/busybox_unstripped" 278 try $CC $CFLAGS $LDFLAGS \ 279 -o $EXE \ 280 $SORT_COMMON \ 281 $SORT_SECTION \ 282 $GC_SECTIONS \ 283 $START_GROUP $O_FILES $END_GROUP \ 284 -L"$sharedlib_dir" -lbusybox \ 285 $l_list \ 286 `INFO_OPTS` \ 287 || { 288 echo "Linking $EXE failed" 289 cat $EXE.out 290 exit 1 291 } 292 $STRIP -s --remove-section=.note --remove-section=.comment $EXE -o "$sharedlib_dir/busybox" 293 echo "busybox linked against libbusybox: $sharedlib_dir/busybox" 294fi 295 296if test "$CONFIG_FEATURE_INDIVIDUAL" = y; then 297 echo "Linking individual applets against libbusybox (see $sharedlib_dir/*)" 298 gcc -DNAME_MAIN -E -include include/autoconf.h include/applets.h \ 299 | grep -v "^#" \ 300 | grep -v "^ *$" \ 301 > applet_lst.tmp 302 while read name main junk; do 303 304 echo "\ 305void lbb_prepare(const char *applet, char **argv); 306int $main(int argc, char **argv); 307 308int main(int argc, char **argv) 309{ 310 lbb_prepare(\"$name\", argv); 311 return $main(argc, argv); 312} 313" >"$sharedlib_dir/applet.c" 314 315 EXE="$sharedlib_dir/$name" 316 try $CC $CFLAGS $LDFLAGS "$sharedlib_dir/applet.c" \ 317 -o $EXE \ 318 $SORT_COMMON \ 319 $SORT_SECTION \ 320 $GC_SECTIONS \ 321 -L"$sharedlib_dir" -lbusybox \ 322 -Wl,--warn-common \ 323 || { 324 echo "Linking $EXE failed" 325 cat $EXE.out 326 exit 1 327 } 328 rm -- "$sharedlib_dir/applet.c" $EXE.out 329 $STRIP -s --remove-section=.note --remove-section=.comment $EXE 330 # Let user see that we do something - list the names of created binaries: 331 echo "$EXE" 332 333 done <applet_lst.tmp 334fi 335 336# libbusybox.so is needed only for -lbusybox at link time, 337# it is not needed at runtime. Deleting to reduce confusion. 338rm "$sharedlib_dir"/libbusybox.so 2>/dev/null 339exit 0 # or else we may confuse make 340