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1 /*
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2 * Copyright 2003-2005 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 #include <unistd.h>
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26 #include <sys/procfs.h>
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27 #include <search.h>
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28 #include <stdlib.h>
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29 #include <string.h>
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30 #include "symtab.h"
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31 #include "salibelf.h"
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32
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33
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34 // ----------------------------------------------------
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35 // functions for symbol lookups
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36 // ----------------------------------------------------
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37
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38 struct elf_section {
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39 ELF_SHDR *c_shdr;
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40 void *c_data;
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41 };
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42
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43 struct elf_symbol {
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44 char *name;
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45 uintptr_t offset;
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46 uintptr_t size;
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47 };
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48
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49 typedef struct symtab {
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50 char *strs;
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51 size_t num_symbols;
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52 struct elf_symbol *symbols;
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53 struct hsearch_data *hash_table;
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54 } symtab_t;
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55
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56 // read symbol table from given fd.
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57 struct symtab* build_symtab(int fd) {
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58 ELF_EHDR ehdr;
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59 char *names = NULL;
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60 struct symtab* symtab = NULL;
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61
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62 // Reading of elf header
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63 struct elf_section *scn_cache = NULL;
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64 int cnt = 0;
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65 ELF_SHDR* shbuf = NULL;
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66 ELF_SHDR* cursct = NULL;
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67 ELF_PHDR* phbuf = NULL;
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68 ELF_PHDR* phdr = NULL;
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69
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70 uintptr_t baseaddr = (uintptr_t)-1;
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71
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72 lseek(fd, (off_t)0L, SEEK_SET);
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73 if (! read_elf_header(fd, &ehdr)) {
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74 // not an elf
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75 return NULL;
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76 }
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77
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78 // read ELF header
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79 if ((shbuf = read_section_header_table(fd, &ehdr)) == NULL) {
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80 goto quit;
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81 }
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82
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83 baseaddr = find_base_address(fd, &ehdr);
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84
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85 scn_cache = (struct elf_section *)
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86 calloc(ehdr.e_shnum * sizeof(struct elf_section), 1);
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87 if (scn_cache == NULL) {
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88 goto quit;
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89 }
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90
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91 for (cursct = shbuf, cnt = 0; cnt < ehdr.e_shnum; cnt++) {
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92 scn_cache[cnt].c_shdr = cursct;
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93 if (cursct->sh_type == SHT_SYMTAB || cursct->sh_type == SHT_STRTAB) {
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94 if ( (scn_cache[cnt].c_data = read_section_data(fd, &ehdr, cursct)) == NULL) {
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95 goto quit;
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96 }
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97 }
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98 cursct++;
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99 }
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100
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101 for (cnt = 1; cnt < ehdr.e_shnum; cnt++) {
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102 ELF_SHDR *shdr = scn_cache[cnt].c_shdr;
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103
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104 if (shdr->sh_type == SHT_SYMTAB) {
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105 ELF_SYM *syms;
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106 int j, n, rslt;
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107 size_t size;
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108
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109 // FIXME: there could be multiple data buffers associated with the
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110 // same ELF section. Here we can handle only one buffer. See man page
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111 // for elf_getdata on Solaris.
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112
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113 // guarantee(symtab == NULL, "multiple symtab");
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114 symtab = (struct symtab*)calloc(1, sizeof(struct symtab));
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115 if (symtab == NULL) {
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116 goto quit;
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117 }
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118 // the symbol table
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119 syms = (ELF_SYM *)scn_cache[cnt].c_data;
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120
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121 // number of symbols
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122 n = shdr->sh_size / shdr->sh_entsize;
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123
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124 // create hash table, we use hcreate_r, hsearch_r and hdestroy_r to
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125 // manipulate the hash table.
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126 symtab->hash_table = (struct hsearch_data*) calloc(1, sizeof(struct hsearch_data));
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127 rslt = hcreate_r(n, symtab->hash_table);
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128 // guarantee(rslt, "unexpected failure: hcreate_r");
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129
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130 // shdr->sh_link points to the section that contains the actual strings
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131 // for symbol names. the st_name field in ELF_SYM is just the
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132 // string table index. we make a copy of the string table so the
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133 // strings will not be destroyed by elf_end.
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134 size = scn_cache[shdr->sh_link].c_shdr->sh_size;
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135 symtab->strs = (char *)malloc(size);
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136 memcpy(symtab->strs, scn_cache[shdr->sh_link].c_data, size);
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137
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138 // allocate memory for storing symbol offset and size;
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139 symtab->num_symbols = n;
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140 symtab->symbols = (struct elf_symbol *)calloc(n , sizeof(struct elf_symbol));
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141
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142 // copy symbols info our symtab and enter them info the hash table
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143 for (j = 0; j < n; j++, syms++) {
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144 ENTRY item, *ret;
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145 char *sym_name = symtab->strs + syms->st_name;
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146
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147 // skip non-object and non-function symbols
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148 int st_type = ELF_ST_TYPE(syms->st_info);
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149 if ( st_type != STT_FUNC && st_type != STT_OBJECT)
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150 continue;
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151 // skip empty strings and undefined symbols
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152 if (*sym_name == '\0' || syms->st_shndx == SHN_UNDEF) continue;
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153
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154 symtab->symbols[j].name = sym_name;
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155 symtab->symbols[j].offset = syms->st_value - baseaddr;
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156 symtab->symbols[j].size = syms->st_size;
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157
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158 item.key = sym_name;
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159 item.data = (void *)&(symtab->symbols[j]);
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160
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161 hsearch_r(item, ENTER, &ret, symtab->hash_table);
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162 }
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163 }
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164 }
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165
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166 quit:
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167 if (shbuf) free(shbuf);
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168 if (phbuf) free(phbuf);
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169 if (scn_cache) {
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170 for (cnt = 0; cnt < ehdr.e_shnum; cnt++) {
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171 if (scn_cache[cnt].c_data != NULL) {
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172 free(scn_cache[cnt].c_data);
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173 }
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174 }
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175 free(scn_cache);
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176 }
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177 return symtab;
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178 }
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179
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180 void destroy_symtab(struct symtab* symtab) {
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181 if (!symtab) return;
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182 if (symtab->strs) free(symtab->strs);
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183 if (symtab->symbols) free(symtab->symbols);
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184 if (symtab->hash_table) {
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185 hdestroy_r(symtab->hash_table);
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186 free(symtab->hash_table);
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187 }
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188 free(symtab);
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189 }
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190
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191 uintptr_t search_symbol(struct symtab* symtab, uintptr_t base,
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192 const char *sym_name, int *sym_size) {
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193 ENTRY item;
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194 ENTRY* ret = NULL;
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195
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196 // library does not have symbol table
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197 if (!symtab || !symtab->hash_table)
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198 return (uintptr_t)NULL;
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199
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200 item.key = (char*) strdup(sym_name);
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201 hsearch_r(item, FIND, &ret, symtab->hash_table);
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202 if (ret) {
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203 struct elf_symbol * sym = (struct elf_symbol *)(ret->data);
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204 uintptr_t rslt = (uintptr_t) ((char*)base + sym->offset);
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205 if (sym_size) *sym_size = sym->size;
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206 free(item.key);
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207 return rslt;
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208 }
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209
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210 quit:
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211 free(item.key);
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212 return (uintptr_t) NULL;
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213 }
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214
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215 const char* nearest_symbol(struct symtab* symtab, uintptr_t offset,
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216 uintptr_t* poffset) {
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217 int n = 0;
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218 if (!symtab) return NULL;
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219 for (; n < symtab->num_symbols; n++) {
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220 struct elf_symbol* sym = &(symtab->symbols[n]);
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221 if (sym->name != NULL &&
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222 offset >= sym->offset && offset < sym->offset + sym->size) {
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223 if (poffset) *poffset = (offset - sym->offset);
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224 return sym->name;
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225 }
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226 }
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227 return NULL;
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228 }
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