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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
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2 <HTML
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3 ><HEAD
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4 ><TITLE
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5 >Linking Scripts</TITLE
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6 ><META
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7 NAME="GENERATOR"
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8 CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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9 REL="HOME"
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10 TITLE="LW Tool Chain"
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11 HREF="index.html"><LINK
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12 REL="UP"
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13 TITLE="LWLINK"
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14 HREF="c734.html"><LINK
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15 REL="PREVIOUS"
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16 TITLE="Linker Operation"
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17 HREF="x834.html"><LINK
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18 REL="NEXT"
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19 TITLE="Format Specific Linking Notes"
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20 HREF="x914.html"></HEAD
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21 ><BODY
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22 CLASS="SECTION"
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23 BGCOLOR="#FFFFFF"
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24 TEXT="#000000"
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25 LINK="#0000FF"
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26 VLINK="#840084"
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27 ALINK="#0000FF"
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28 ><DIV
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29 CLASS="NAVHEADER"
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30 ><TABLE
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31 SUMMARY="Header navigation table"
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32 WIDTH="100%"
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33 BORDER="0"
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34 CELLPADDING="0"
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35 CELLSPACING="0"
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36 ><TR
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37 ><TH
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38 COLSPAN="3"
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39 ALIGN="center"
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40 >LW Tool Chain</TH
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41 ></TR
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42 ><TR
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43 ><TD
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44 WIDTH="10%"
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45 ALIGN="left"
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46 VALIGN="bottom"
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47 ><A
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48 HREF="x834.html"
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49 ACCESSKEY="P"
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50 >Prev</A
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51 ></TD
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52 ><TD
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53 WIDTH="80%"
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54 ALIGN="center"
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55 VALIGN="bottom"
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56 >Chapter 4. LWLINK</TD
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57 ><TD
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58 WIDTH="10%"
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59 ALIGN="right"
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60 VALIGN="bottom"
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61 ><A
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62 HREF="x914.html"
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63 ACCESSKEY="N"
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64 >Next</A
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65 ></TD
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66 ></TR
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67 ></TABLE
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68 ><HR
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69 ALIGN="LEFT"
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70 WIDTH="100%"></DIV
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71 ><DIV
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72 CLASS="SECTION"
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73 ><H1
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74 CLASS="SECTION"
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75 ><A
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76 NAME="AEN848"
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77 >4.3. Linking Scripts</A
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78 ></H1
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79 ><P
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80 >A linker script is used to instruct the linker about how to assemble the
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81 various sections into a completed binary. It consists of a series of
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82 directives which are considered in the order they are encountered.</P
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83 ><P
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84 >The sections will appear in the resulting binary in the order they are
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85 specified in the script file. If a referenced section is not found, the linker will behave as though the
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86 section did exist but had a zero size, no relocations, and no exports.
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87 A section should only be referenced once. Any subsequent references will have
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88 an undefined effect.</P
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89 ><P
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90 >All numbers are in linking scripts are specified in hexadecimal. All directives
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91 are case sensitive although the hexadecimal numbers are not.</P
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92 ><P
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93 >A section name can be specified as a "*", then any section not
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94 already matched by the script will be matched. The "*" can be followed
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95 by a comma and a flag to narrow the section down slightly, also.
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96 If the flag is "!bss", then any section that is not flagged as a bss section
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97 will be matched. If the flag is "bss", then any section that is flagged as
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98 bss will be matched.</P
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99 ><P
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100 >The following directives are understood in a linker script.</P
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101 ><P
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102 ></P
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103 ><DIV
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104 CLASS="VARIABLELIST"
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105 ><DL
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106 ><DT
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107 >sectopt <CODE
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108 CLASS="PARAMETER"
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109 >section</CODE
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110 > padafter <CODE
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111 CLASS="PARAMETER"
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112 >byte,...</CODE
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113 ></DT
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114 ><DD
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115 ><P
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116 > This will cause the linker to append the specified list of byte values
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117 (specified in hexadecimal separated by commas) to the end of the named
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118 section. This is done once all instances of the specified section are
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119 collected together. This has no effect if the specified section does not
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120 appear anywhere in any of the objects specified for linking. </P
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121 ><P
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122 > If code depends on the presence of this padding somewhere, it is sufficient
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123 to include an empty section of the specified name in the object that depends
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124 on it. </P
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125 ></DD
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126 ><DT
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127 >define basesympat <CODE
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128 CLASS="PARAMETER"
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129 >string</CODE
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130 ></DT
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131 ><DD
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132 ><P
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133 > This causes the linker to define a symbol for the ultimate base address of
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134 each section using the pattern specified by <CODE
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135 CLASS="PARAMETER"
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136 >string</CODE
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137 >.
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138 In the string, %s can appear exactly once and will be replaced with the
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139 section name. The base address is calculated after all instances of each
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140 section have been collapsed together. </P
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141 ><P
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142 > It should be noted that if none of the objects to be linked contains a
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143 particular section name, there will be no base symbol defined for it, even
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144 if it is listed explicitly in the link script. If code depends on the
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145 presence of these symbols, it is sufficient to include an empty section of
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146 the specified name in the object that depends on it. </P
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147 ><P
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148 > If the pattern resolves to the same string for multiple
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149 sections, the results are undefined. </P
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150 ></DD
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151 ><DT
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152 >define lensympat <CODE
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153 CLASS="PARAMETER"
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154 >string</CODE
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155 ></DT
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156 ><DD
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157 ><P
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158 > This causes the linker to define a symbol for the ultimate length of each
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159 section using the pattern specified by <CODE
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160 CLASS="PARAMETER"
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161 >string</CODE
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162 >. In
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163 the string, %s can appear exactly once and will be replaced with the section
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164 name. The length is calculated after all instances of a section have been
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165 collapsed together. </P
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166 ><P
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167 > It should be noted that if none of the objects to be linked contains a
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168 particular section name, there will be no length symbol defined for it, even
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169 if it is listed explicitly in the link script. If code depends on the
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170 presence of these symbols, it is sufficient to include an empty section of
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171 the specified name in the object that depends on it. </P
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172 ><P
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173 >If the pattern resolves to the same string for multiple
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174 sections, the results are undefined. </P
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175 ></DD
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176 ><DT
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177 >section <CODE
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178 CLASS="PARAMETER"
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179 >name</CODE
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180 > load <CODE
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181 CLASS="PARAMETER"
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182 >addr</CODE
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183 ></DT
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184 ><DD
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185 ><P
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186 > This causes the section <CODE
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187 CLASS="PARAMETER"
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188 >name</CODE
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189 > to load at
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190 <CODE
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191 CLASS="PARAMETER"
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192 >addr</CODE
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193 >. For the raw target, only one "load at" entry is
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194 allowed for non-bss sections and it must be the first one. For raw targets,
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195 it affects the addresses the linker assigns to symbols but has no other
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196 affect on the output. bss sections may all have separate load addresses but
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197 since they will not appear in the binary anyway, this is okay.</P
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198 ><P
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199 >For the decb target, each "load" entry will cause a new "block" to be
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200 output to the binary which will contain the load address. It is legal for
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201 sections to overlap in this manner - the linker assumes the loader will sort
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202 everything out.</P
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203 ></DD
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204 ><DT
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205 >section <CODE
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206 CLASS="PARAMETER"
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207 >name</CODE
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208 > high <CODE
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209 CLASS="PARAMETER"
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210 >addr</CODE
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211 ></DT
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212 ><DD
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213 ><P
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214 > This causes the section <CODE
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215 CLASS="PARAMETER"
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216 >name</CODE
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217 > to load with its end
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218 address just below <CODE
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219 CLASS="PARAMETER"
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220 >addr</CODE
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221 >. Subsequent sections are
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222 loaded at progressively lower addresses. This may lead to inefficient file
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223 encoding for some targets. As of this writing, it will also almost
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224 certainly do the wrong thing for a raw target. </P
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225 ><P
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226 > This is useful for aligning a block of code with high memory. As an
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227 example, if the total size of a section is $100 bytes and a high address of
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228 $FE00 is specified, the section will actually load at $FD00. </P
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229 ></DD
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230 ><DT
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231 >section <CODE
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232 CLASS="PARAMETER"
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233 >name</CODE
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234 ></DT
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235 ><DD
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236 ><P
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237 > This will cause the section <CODE
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238 CLASS="PARAMETER"
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239 >name</CODE
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240 > to load after the previously listed
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241 section.</P
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242 ></DD
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243 ><DT
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244 >entry <CODE
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245 CLASS="PARAMETER"
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246 >addr or sym</CODE
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247 ></DT
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248 ><DD
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249 ><P
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250 >This will cause the execution address (entry point) to be the address
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251 specified (in hex) or the specified symbol name. The symbol name must
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252 match a symbol that is exported by one of the object files being linked.
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253 This has no effect for targets that do not encode the entry point into the
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254 resulting file. If not specified, the entry point is assumed to be address 0
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255 which is probably not what you want. The default link scripts for targets
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256 that support this directive automatically starts at the beginning of the
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257 first section (usually "init" or "code") that is emitted in the binary.</P
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258 ></DD
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259 ><DT
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260 >pad <CODE
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261 CLASS="PARAMETER"
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262 >size</CODE
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263 ></DT
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264 ><DD
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265 ><P
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266 >This will cause the output file to be padded with NUL bytes to be exactly
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267 <CODE
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268 CLASS="PARAMETER"
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269 >size</CODE
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270 > bytes in length. This only makes sense for a raw target.</P
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271 ></DD
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272 ></DL
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273 ></DIV
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274 ></DIV
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275 ><DIV
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276 CLASS="NAVFOOTER"
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277 ><HR
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278 ALIGN="LEFT"
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279 WIDTH="100%"><TABLE
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280 SUMMARY="Footer navigation table"
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281 WIDTH="100%"
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282 BORDER="0"
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283 CELLPADDING="0"
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284 CELLSPACING="0"
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285 ><TR
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286 ><TD
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287 WIDTH="33%"
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288 ALIGN="left"
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289 VALIGN="top"
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290 ><A
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291 HREF="x834.html"
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292 ACCESSKEY="P"
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293 >Prev</A
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294 ></TD
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295 ><TD
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296 WIDTH="34%"
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297 ALIGN="center"
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298 VALIGN="top"
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299 ><A
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300 HREF="index.html"
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301 ACCESSKEY="H"
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302 >Home</A
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303 ></TD
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304 ><TD
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305 WIDTH="33%"
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306 ALIGN="right"
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307 VALIGN="top"
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308 ><A
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309 HREF="x914.html"
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310 ACCESSKEY="N"
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311 >Next</A
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312 ></TD
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313 ></TR
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314 ><TR
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315 ><TD
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316 WIDTH="33%"
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317 ALIGN="left"
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318 VALIGN="top"
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319 >Linker Operation</TD
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320 ><TD
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321 WIDTH="34%"
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322 ALIGN="center"
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323 VALIGN="top"
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324 ><A
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325 HREF="c734.html"
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326 ACCESSKEY="U"
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327 >Up</A
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328 ></TD
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329 ><TD
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330 WIDTH="33%"
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331 ALIGN="right"
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332 VALIGN="top"
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333 >Format Specific Linking Notes</TD
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334 ></TR
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335 ></TABLE
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336 ></DIV
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337 ></BODY
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338 ></HTML
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339 > |
