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136
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1 /*
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2 link.c
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3 Copyright © 2009 William Astle
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4
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5 This file is part of LWLINK.
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6
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7 LWLINK is free software: you can redistribute it and/or modify it under the
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8 terms of the GNU General Public License as published by the Free Software
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9 Foundation, either version 3 of the License, or (at your option) any later
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10 version.
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11
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12 This program is distributed in the hope that it will be useful, but WITHOUT
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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15 more details.
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16
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17 You should have received a copy of the GNU General Public License along with
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18 this program. If not, see <http://www.gnu.org/licenses/>.
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19
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20
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21 Resolve section and symbol addresses; handle incomplete references
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22 */
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23
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24 #ifdef HAVE_CONFIG_H
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25 #include "config.h"
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26 #endif
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27
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28 #include <stdio.h>
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29 #include <stdlib.h>
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30
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31 #include "expr.h"
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32 #include "lwlink.h"
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33 #include "util.h"
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34
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35 struct section_list *sectlist = NULL;
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36 int nsects = 0;
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37
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38 // work out section load order and resolve base addresses for each section
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39 // make a list of sections to load in order
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40 void resolve_sections(void)
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41 {
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42 int laddr = 0;
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43 int ln, sn, fn;
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44
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45 for (ln = 0; ln < linkscript.nlines; ln++)
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46 {
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47 // printf("Linker script line %d: '%s', %04X, %d, %d\n", ln, linkscript.lines[ln].sectname, linkscript.lines[ln].loadat, linkscript.lines[ln].yesflags, linkscript.lines[ln].noflags);
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48 if (linkscript.lines[ln].sectname)
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49 {
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50 int f = 0;
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51 // named section
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52 // look for all instances of a section by the specified name
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53 // and resolve base addresses and add to the list
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54 for (fn = 0; fn < ninputfiles; fn++)
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55 {
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56 for (sn = 0; sn < inputfiles[fn] -> nsections; sn++)
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57 {
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58 // printf(" Considering %s:%s\n", inputfiles[fn]->filename, inputfiles[fn]->sections[sn].name);
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59 if (!strcmp(linkscript.lines[ln].sectname, inputfiles[fn] -> sections[sn].name))
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60 {
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61 // we have a match
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62 sectlist = lw_realloc(sectlist, sizeof(struct section_list) * (nsects + 1));
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63 sectlist[nsects].ptr = &(inputfiles[fn] -> sections[sn]);
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64
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65 inputfiles[fn] -> sections[sn].processed = 1;
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66 if (!f && linkscript.lines[ln].loadat >= 0)
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67 {
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68 f = 1;
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69 sectlist[nsects].forceaddr = 1;
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70 laddr = linkscript.lines[ln].loadat;
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71 }
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72 else
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73 {
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74 sectlist[nsects].forceaddr = 0;
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75 }
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76 inputfiles[fn] -> sections[sn].loadaddress = laddr;
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77 laddr += inputfiles[fn] -> sections[sn].codesize;
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78 nsects++;
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79 }
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80 }
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81 }
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82 }
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83 else
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84 {
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85 // wildcard section
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86 // look for all sections not yet processed that match flags
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87
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88 int f = 0;
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89 int fn0, sn0;
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90 char *sname;
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91
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92 // named section
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93 // look for all instances of a section by the specified name
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94 // and resolve base addresses and add to the list
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95 for (fn0 = 0; fn0 < ninputfiles; fn0++)
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96 {
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97 for (sn0 = 0; sn0 < inputfiles[fn0] -> nsections; sn0++)
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98 {
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99 // ignore if the "no flags" bit says to
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100 if (linkscript.lines[ln].noflags && (inputfiles[fn0] -> sections[sn0].flags & linkscript.lines[ln].noflags))
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101 continue;
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102 // ignore unless the yes flags tell us not to
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103 if (linkscript.lines[ln].yesflags && (inputfiles[fn0] -> sections[sn0].flags & linkscript.lines[ln].yesflags == 0))
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104 continue;
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105 if (inputfiles[fn0] -> sections[sn0].processed == 0)
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106 {
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107 sname = inputfiles[fn0] -> sections[sn0].name;
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108 for (fn = 0; fn < ninputfiles; fn++)
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109 {
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110 for (sn = 0; sn < inputfiles[fn] -> nsections; sn++)
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111 {
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112 if (!strcmp(sname, inputfiles[fn] -> sections[sn].name))
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113 {
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114 // we have a match
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115 sectlist = lw_realloc(sectlist, sizeof(struct section_list) * (nsects + 1));
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116 sectlist[nsects].ptr = &(inputfiles[fn] -> sections[sn]);
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117
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118 inputfiles[fn] -> sections[sn].processed = 1;
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119 if (!f && linkscript.lines[ln].loadat >= 0)
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120 {
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121 f = 1;
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122 sectlist[nsects].forceaddr = 1;
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123 laddr = linkscript.lines[ln].loadat;
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124 }
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125 else
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126 {
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127 sectlist[nsects].forceaddr = 0;
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128 }
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129 inputfiles[fn] -> sections[sn].loadaddress = laddr;
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130 laddr += inputfiles[fn] -> sections[sn].codesize;
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131 nsects++;
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132 }
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133 }
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134 }
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135 }
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136 }
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137 }
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138 }
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139 }
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140
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141 // theoretically, all the base addresses are set now
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142 }
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143
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144 // resolve all incomplete references now
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145 // anything that is unresolvable at this stage will throw an error
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146 // because we know the load address of every section now
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147 lw_expr_stack_t *resolve_sym(char *sym, int symtype, void *state)
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148 {
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149 section_t *sect = state;
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150 lw_expr_term_t *term;
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151 int val = 0, i, fn;
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152 lw_expr_stack_t *s;
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153 symtab_t *se;
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154
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155 if (symtype == 1)
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156 {
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157 // local symbol
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158 if (!sym)
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159 {
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160 val = sect -> loadaddress;
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161 goto out;
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162 }
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163
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164 // start with this section
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165 for (se = sect -> localsyms; se; se = se -> next)
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166 {
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167 if (!strcmp(se -> sym, sym))
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168 {
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169 val = se -> offset + sect -> loadaddress;
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170 goto out;
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171 }
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172 }
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173 // not in this section - check all sections in this file
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174 for (i = 0; i < sect -> file -> nsections; i++)
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175 {
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176 for (se = sect -> file -> sections[i].localsyms; se; se = se -> next)
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177 {
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178 if (!strcmp(se -> sym, sym))
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179 {
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180 val = se -> offset + sect -> file -> sections[i].loadaddress;
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181 goto out;
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182 }
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183 }
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184 }
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185 // not found
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186 fprintf(stderr, "Local symbol %s not found in %s:%s\n", sym, sect -> file -> filename, sect -> name);
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187 exit(1);
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188 }
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189 else
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190 {
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191 // external symbol
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192 // read all files in order until found (or not found)
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193 for (fn = 0; fn < ninputfiles; fn++)
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194 {
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195 for (i = 0; i < inputfiles[fn] -> nsections; i++)
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196 {
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197 for (se = inputfiles[fn] -> sections[i].exportedsyms; se; se = se -> next)
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198 {
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199 if (!strcmp(sym, se -> sym))
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200 {
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201 val = se -> offset + inputfiles[fn] -> sections[i].loadaddress;
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202 goto out;
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203 }
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204 }
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205 }
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206 }
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207 if (sect)
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208 {
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209 fprintf(stderr, "External symbol %s not found in %s:%s\n", sym, sect -> file -> filename, sect -> name);
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210 }
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211 else
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212 {
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213 fprintf(stderr, "External symbol %s not found\n", sym);
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214 }
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215 exit(1);
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216 }
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217 fprintf(stderr, "Shouldn't ever get here!!!\n");
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218 exit(88);
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219 out:
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220 s = lw_expr_stack_create();
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221 term = lw_expr_term_create_int(val & 0xffff);
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222 lw_expr_stack_push(s, term);
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223 lw_expr_term_free(term);
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224 return s;
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225 }
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226
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227 void resolve_references(void)
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228 {
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229 int sn;
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230 reloc_t *rl;
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231 int rval;
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232
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233 // resolve entry point if required
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234 // this must resolve to an *exported* symbol and will resolve to the
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235 // first instance of that symbol
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236 if (linkscript.execsym)
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237 {
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238 lw_expr_stack_t *s;
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239
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240 s = resolve_sym(linkscript.execsym, 0, NULL);
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241 linkscript.execaddr = lw_expr_get_value(s);
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242 lw_expr_stack_free(s);
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243 }
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244
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245 for (sn = 0; sn < nsects; sn++)
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246 {
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247 for (rl = sectlist[sn].ptr -> incompletes; rl; rl = rl -> next)
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248 {
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249 // do a "simplify" on the expression
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250 rval = lw_expr_reval(rl -> expr, resolve_sym, sectlist[sn].ptr);
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251
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252 // is it constant? error out if not
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253 if (rval != 0 || !lw_expr_is_constant(rl -> expr))
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254 {
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255 fprintf(stderr, "Incomplete reference at %s:%s:%02X\n", sectlist[sn].ptr -> file -> filename, sectlist[sn].ptr -> name, rl -> offset);
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256 exit(1);
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257 }
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258
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259 // put the value into the relocation address
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260 rval = lw_expr_get_value(rl -> expr);
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261 sectlist[sn].ptr -> code[rl -> offset] = (rval >> 8) & 0xff;
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262 sectlist[sn].ptr -> code[rl -> offset + 1] = rval & 0xff;
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263 }
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264 }
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265 }
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