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1 /*
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2 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * 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 <search.h>
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27 #include <stdlib.h>
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28 #include <string.h>
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29 #include <db.h>
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30 #include <fcntl.h>
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31
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32 #include "libproc_impl.h"
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33 #include "symtab.h"
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34 #ifndef __APPLE__
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35 #include "salibelf.h"
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36 #endif // __APPLE__
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37
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38
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39 // ----------------------------------------------------
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40 // functions for symbol lookups
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41 // ----------------------------------------------------
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42
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43 typedef struct symtab_symbol {
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44 char *name; // name like __ZThread_...
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45 uintptr_t offset; // to loaded address
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46 uintptr_t size; // size strlen
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47 } symtab_symbol;
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48
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49 typedef struct symtab {
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50 char *strs; // all symbols "__symbol1__'\0'__symbol2__...."
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51 size_t num_symbols;
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52 DB* hash_table;
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53 symtab_symbol* symbols;
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54 } symtab_t;
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55
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56 #ifdef __APPLE__
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57
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58 void build_search_table(symtab_t *symtab) {
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59 int i;
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60 for (i = 0; i < symtab->num_symbols; i++) {
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61 DBT key, value;
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62 key.data = symtab->symbols[i].name;
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63 key.size = strlen(key.data) + 1;
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64 value.data = &(symtab->symbols[i]);
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65 value.size = sizeof(symtab_symbol);
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66 (*symtab->hash_table->put)(symtab->hash_table, &key, &value, 0);
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67
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68 // check result
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69 if (is_debug()) {
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70 DBT rkey, rvalue;
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71 char* tmp = (char *)malloc(strlen(symtab->symbols[i].name) + 1);
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72 strcpy(tmp, symtab->symbols[i].name);
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73 rkey.data = tmp;
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74 rkey.size = strlen(tmp) + 1;
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75 (*symtab->hash_table->get)(symtab->hash_table, &rkey, &rvalue, 0);
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76 // we may get a copy back so compare contents
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77 symtab_symbol *res = (symtab_symbol *)rvalue.data;
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78 if (strcmp(res->name, symtab->symbols[i].name) ||
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79 res->offset != symtab->symbols[i].offset ||
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80 res->size != symtab->symbols[i].size) {
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81 print_debug("error to get hash_table value!\n");
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82 }
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83 free(tmp);
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84 }
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85 }
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86 }
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87
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88 // read symbol table from given fd.
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89 struct symtab* build_symtab(int fd) {
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90 symtab_t* symtab = NULL;
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91 int i;
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92 mach_header_64 header;
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93 off_t image_start;
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94
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95 if (!get_arch_off(fd, CPU_TYPE_X86_64, &image_start)) {
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96 print_debug("failed in get fat header\n");
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97 return NULL;
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98 }
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99 lseek(fd, image_start, SEEK_SET);
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100 if (read(fd, (void *)&header, sizeof(mach_header_64)) != sizeof(mach_header_64)) {
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101 print_debug("reading header failed!\n");
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102 return NULL;
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103 }
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104 // header
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105 if (header.magic != MH_MAGIC_64) {
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106 print_debug("not a valid .dylib file\n");
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107 return NULL;
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108 }
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109
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110 load_command lcmd;
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111 symtab_command symtabcmd;
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112 nlist_64 lentry;
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113
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114 bool lcsymtab_exist = false;
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115
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116 long filepos = ltell(fd);
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117 for (i = 0; i < header.ncmds; i++) {
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118 lseek(fd, filepos, SEEK_SET);
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119 if (read(fd, (void *)&lcmd, sizeof(load_command)) != sizeof(load_command)) {
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120 print_debug("read load_command failed for file\n");
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121 return NULL;
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122 }
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123 filepos += lcmd.cmdsize; // next command position
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124 if (lcmd.cmd == LC_SYMTAB) {
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125 lseek(fd, -sizeof(load_command), SEEK_CUR);
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126 lcsymtab_exist = true;
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127 break;
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128 }
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129 }
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130 if (!lcsymtab_exist) {
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131 print_debug("No symtab command found!\n");
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132 return NULL;
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133 }
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134 if (read(fd, (void *)&symtabcmd, sizeof(symtab_command)) != sizeof(symtab_command)) {
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135 print_debug("read symtab_command failed for file");
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136 return NULL;
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137 }
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138 symtab = (symtab_t *)malloc(sizeof(symtab_t));
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139 if (symtab == NULL) {
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140 print_debug("out of memory: allocating symtab\n");
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141 return NULL;
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142 }
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143
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144 // create hash table, we use berkeley db to
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145 // manipulate the hash table.
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146 symtab->hash_table = dbopen(NULL, O_CREAT | O_RDWR, 0600, DB_HASH, NULL);
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147 if (symtab->hash_table == NULL)
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148 goto quit;
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149
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150 symtab->num_symbols = symtabcmd.nsyms;
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151 symtab->symbols = (symtab_symbol *)malloc(sizeof(symtab_symbol) * symtab->num_symbols);
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152 symtab->strs = (char *)malloc(sizeof(char) * symtabcmd.strsize);
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153 if (symtab->symbols == NULL || symtab->strs == NULL) {
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154 print_debug("out of memory: allocating symtab.symbol or symtab.strs\n");
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155 goto quit;
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156 }
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157 lseek(fd, image_start + symtabcmd.symoff, SEEK_SET);
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158 for (i = 0; i < symtab->num_symbols; i++) {
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159 if (read(fd, (void *)&lentry, sizeof(nlist_64)) != sizeof(nlist_64)) {
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160 print_debug("read nlist_64 failed at %i\n", i);
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161 goto quit;
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162 }
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163 symtab->symbols[i].offset = lentry.n_value;
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164 symtab->symbols[i].size = lentry.n_un.n_strx; // index
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165 }
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166
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167 // string table
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168 lseek(fd, image_start + symtabcmd.stroff, SEEK_SET);
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169 int size = read(fd, (void *)(symtab->strs), symtabcmd.strsize * sizeof(char));
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170 if (size != symtabcmd.strsize * sizeof(char)) {
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171 print_debug("reading string table failed\n");
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172 goto quit;
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173 }
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174
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175 for (i = 0; i < symtab->num_symbols; i++) {
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176 symtab->symbols[i].name = symtab->strs + symtab->symbols[i].size;
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177 if (i > 0) {
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178 // fix size
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179 symtab->symbols[i - 1].size = symtab->symbols[i].size - symtab->symbols[i - 1].size;
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180 print_debug("%s size = %d\n", symtab->symbols[i - 1].name, symtab->symbols[i - 1].size);
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181
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182 }
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183
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184 if (i == symtab->num_symbols - 1) {
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185 // last index
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186 symtab->symbols[i].size =
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187 symtabcmd.strsize - symtab->symbols[i].size;
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188 print_debug("%s size = %d\n", symtab->symbols[i].name, symtab->symbols[i].size);
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189 }
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190 }
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191
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192 // build a hashtable for fast query
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193 build_search_table(symtab);
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194 return symtab;
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195 quit:
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196 if (symtab) destroy_symtab(symtab);
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197 return NULL;
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198 }
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199
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200 #else // __APPLE__
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201
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202 struct elf_section {
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203 ELF_SHDR *c_shdr;
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204 void *c_data;
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205 };
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206
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207 // read symbol table from given fd.
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208 struct symtab* build_symtab(int fd) {
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209 ELF_EHDR ehdr;
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210 struct symtab* symtab = NULL;
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211
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212 // Reading of elf header
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213 struct elf_section *scn_cache = NULL;
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214 int cnt = 0;
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215 ELF_SHDR* shbuf = NULL;
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216 ELF_SHDR* cursct = NULL;
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217 ELF_PHDR* phbuf = NULL;
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218 int symtab_found = 0;
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219 int dynsym_found = 0;
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220 uint32_t symsection = SHT_SYMTAB;
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221
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222 uintptr_t baseaddr = (uintptr_t)-1;
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223
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224 lseek(fd, (off_t)0L, SEEK_SET);
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225 if (! read_elf_header(fd, &ehdr)) {
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226 // not an elf
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227 return NULL;
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228 }
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229
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230 // read ELF header
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231 if ((shbuf = read_section_header_table(fd, &ehdr)) == NULL) {
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232 goto quit;
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233 }
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234
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235 baseaddr = find_base_address(fd, &ehdr);
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236
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237 scn_cache = calloc(ehdr.e_shnum, sizeof(*scn_cache));
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238 if (scn_cache == NULL) {
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239 goto quit;
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240 }
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241
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242 for (cursct = shbuf, cnt = 0; cnt < ehdr.e_shnum; cnt++) {
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243 scn_cache[cnt].c_shdr = cursct;
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244 if (cursct->sh_type == SHT_SYMTAB ||
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245 cursct->sh_type == SHT_STRTAB ||
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246 cursct->sh_type == SHT_DYNSYM) {
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247 if ( (scn_cache[cnt].c_data = read_section_data(fd, &ehdr, cursct)) == NULL) {
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248 goto quit;
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249 }
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250 }
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251
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252 if (cursct->sh_type == SHT_SYMTAB)
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253 symtab_found++;
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254
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255 if (cursct->sh_type == SHT_DYNSYM)
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256 dynsym_found++;
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257
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258 cursct++;
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259 }
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260
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261 if (!symtab_found && dynsym_found)
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262 symsection = SHT_DYNSYM;
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263
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264 for (cnt = 1; cnt < ehdr.e_shnum; cnt++) {
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265 ELF_SHDR *shdr = scn_cache[cnt].c_shdr;
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266
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267 if (shdr->sh_type == symsection) {
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268 ELF_SYM *syms;
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269 int j, n;
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270 size_t size;
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271
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272 // FIXME: there could be multiple data buffers associated with the
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273 // same ELF section. Here we can handle only one buffer. See man page
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274 // for elf_getdata on Solaris.
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275
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276 // guarantee(symtab == NULL, "multiple symtab");
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277 symtab = calloc(1, sizeof(*symtab));
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278 if (symtab == NULL) {
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279 goto quit;
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280 }
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281 // the symbol table
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282 syms = (ELF_SYM *)scn_cache[cnt].c_data;
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283
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284 // number of symbols
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285 n = shdr->sh_size / shdr->sh_entsize;
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286
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287 // create hash table, we use berkeley db to
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288 // manipulate the hash table.
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289 symtab->hash_table = dbopen(NULL, O_CREAT | O_RDWR, 0600, DB_HASH, NULL);
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290 // guarantee(symtab->hash_table, "unexpected failure: dbopen");
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291 if (symtab->hash_table == NULL)
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292 goto bad;
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293
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294 // shdr->sh_link points to the section that contains the actual strings
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295 // for symbol names. the st_name field in ELF_SYM is just the
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296 // string table index. we make a copy of the string table so the
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297 // strings will not be destroyed by elf_end.
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298 size = scn_cache[shdr->sh_link].c_shdr->sh_size;
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299 symtab->strs = malloc(size);
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300 if (symtab->strs == NULL)
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301 goto bad;
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302 memcpy(symtab->strs, scn_cache[shdr->sh_link].c_data, size);
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303
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304 // allocate memory for storing symbol offset and size;
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305 symtab->num_symbols = n;
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306 symtab->symbols = calloc(n , sizeof(*symtab->symbols));
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307 if (symtab->symbols == NULL)
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308 goto bad;
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309
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310 // copy symbols info our symtab and enter them info the hash table
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311 for (j = 0; j < n; j++, syms++) {
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312 DBT key, value;
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313 char *sym_name = symtab->strs + syms->st_name;
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314
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315 // skip non-object and non-function symbols
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316 int st_type = ELF_ST_TYPE(syms->st_info);
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317 if ( st_type != STT_FUNC && st_type != STT_OBJECT)
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318 continue;
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319 // skip empty strings and undefined symbols
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320 if (*sym_name == '\0' || syms->st_shndx == SHN_UNDEF) continue;
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321
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322 symtab->symbols[j].name = sym_name;
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323 symtab->symbols[j].offset = syms->st_value - baseaddr;
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324 symtab->symbols[j].size = syms->st_size;
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325
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326 key.data = sym_name;
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327 key.size = strlen(sym_name) + 1;
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328 value.data = &(symtab->symbols[j]);
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329 value.size = sizeof(symtab_symbol);
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330 (*symtab->hash_table->put)(symtab->hash_table, &key, &value, 0);
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331 }
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332 }
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333 }
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334 goto quit;
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335
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336 bad:
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337 destroy_symtab(symtab);
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338 symtab = NULL;
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339
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340 quit:
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341 if (shbuf) free(shbuf);
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342 if (phbuf) free(phbuf);
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343 if (scn_cache) {
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344 for (cnt = 0; cnt < ehdr.e_shnum; cnt++) {
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345 if (scn_cache[cnt].c_data != NULL) {
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346 free(scn_cache[cnt].c_data);
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347 }
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348 }
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349 free(scn_cache);
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350 }
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351 return symtab;
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352 }
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353
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354 #endif // __APPLE__
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355
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356 void destroy_symtab(symtab_t* symtab) {
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357 if (!symtab) return;
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358 free(symtab->strs);
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359 free(symtab->symbols);
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360 free(symtab);
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361 }
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362
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363 uintptr_t search_symbol(struct symtab* symtab, uintptr_t base, const char *sym_name, int *sym_size) {
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364 DBT key, value;
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365 int ret;
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366
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367 // library does not have symbol table
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368 if (!symtab || !symtab->hash_table) {
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369 return 0;
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370 }
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371
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372 key.data = (char*)(uintptr_t)sym_name;
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373 key.size = strlen(sym_name) + 1;
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374 ret = (*symtab->hash_table->get)(symtab->hash_table, &key, &value, 0);
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375 if (ret == 0) {
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376 symtab_symbol *sym = value.data;
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377 uintptr_t rslt = (uintptr_t) ((char*)base + sym->offset);
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378 if (sym_size) *sym_size = sym->size;
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379 return rslt;
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380 }
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381
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382 return 0;
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383 }
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384
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385 const char* nearest_symbol(struct symtab* symtab, uintptr_t offset,
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386 uintptr_t* poffset) {
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387 int n = 0;
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388 if (!symtab) return NULL;
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389 for (; n < symtab->num_symbols; n++) {
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390 symtab_symbol* sym = &(symtab->symbols[n]);
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391 if (sym->name != NULL &&
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392 offset >= sym->offset && offset < sym->offset + sym->size) {
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393 if (poffset) *poffset = (offset - sym->offset);
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394 return sym->name;
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395 }
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3960
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396 }
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397 return NULL;
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398 }
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