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