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2978 | svoboda | 1 | /* |
2 | * Copyright (c) 2008 Jiri Svoboda |
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3 | * All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions |
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7 | * are met: |
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8 | * |
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9 | * - Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * - Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * - The name of the author may not be used to endorse or promote products |
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15 | * derived from this software without specific prior written permission. |
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16 | * |
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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27 | */ |
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28 | |||
29 | /** @addtogroup rtld rtld |
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30 | * @brief |
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31 | * @{ |
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32 | */ |
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33 | /** |
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34 | * @file |
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35 | */ |
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36 | |||
37 | #include <stdio.h> |
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38 | #include <stdlib.h> |
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39 | #include <string.h> |
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40 | |||
41 | #include <rtld.h> |
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42 | #include <symbol.h> |
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43 | #include <elf.h> |
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44 | |||
2998 | svoboda | 45 | /* |
46 | * Hash tables are 32-bit (elf_word) even for 64-bit ELF files. |
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47 | */ |
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48 | static elf_word elf_hash(const unsigned char *name) |
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49 | { |
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50 | elf_word h = 0, g; |
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51 | |||
52 | while (*name) { |
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53 | h = (h << 4) + *name++; |
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54 | g = h & 0xf0000000; |
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55 | if (g != 0) h ^= g >> 24; |
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56 | h &= ~g; |
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57 | } |
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58 | |||
59 | return h; |
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60 | } |
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61 | |||
2980 | svoboda | 62 | static elf_symbol_t *def_find_in_module(char *name, module_t *m) |
2978 | svoboda | 63 | { |
64 | elf_symbol_t *sym_table; |
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2998 | svoboda | 65 | elf_symbol_t *s, *sym; |
66 | elf_word nbucket; |
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2978 | svoboda | 67 | elf_word nchain; |
2998 | svoboda | 68 | elf_word i; |
2978 | svoboda | 69 | char *s_name; |
2998 | svoboda | 70 | elf_word bucket; |
2978 | svoboda | 71 | |
2998 | svoboda | 72 | // module_name = m->dyn.soname; |
3689 | svoboda | 73 | DPRINTF("def_find_in_module('%s', %s)\n", name, module_name); |
2978 | svoboda | 74 | |
75 | sym_table = m->dyn.sym_tab; |
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2998 | svoboda | 76 | nbucket = m->dyn.hash[0]; |
2978 | svoboda | 77 | nchain = m->dyn.hash[1]; |
78 | |||
2998 | svoboda | 79 | bucket = elf_hash((unsigned char *)name) % nbucket; |
80 | i = m->dyn.hash[2 + bucket]; |
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81 | |||
82 | sym = NULL; |
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83 | while (i != STN_UNDEF) { |
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84 | s = &sym_table[i]; |
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85 | s_name = m->dyn.str_tab + s->st_name; |
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86 | |||
2978 | svoboda | 87 | if (strcmp(name, s_name) == 0) { |
2998 | svoboda | 88 | sym = s; |
89 | break; |
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2978 | svoboda | 90 | } |
2998 | svoboda | 91 | |
92 | i = m->dyn.hash[2 + nbucket + i]; |
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2978 | svoboda | 93 | } |
94 | |||
2998 | svoboda | 95 | if (!sym) |
96 | return NULL; /* Not found */ |
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97 | |||
98 | if (sym->st_shndx == SHN_UNDEF) { |
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99 | /* Not a definition */ |
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100 | return NULL; |
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101 | } |
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102 | |||
103 | return sym; /* Found */ |
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2978 | svoboda | 104 | } |
105 | |||
3689 | svoboda | 106 | /** Find the definition of a symbol in a module and its deps. |
2999 | svoboda | 107 | * |
3689 | svoboda | 108 | * Search the module dependency graph is breadth-first, beginning |
109 | * from the module @a start. Thus, @start and all its dependencies |
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110 | * get searched. |
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2999 | svoboda | 111 | * |
112 | * @param name Name of the symbol to search for. |
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3689 | svoboda | 113 | * @param start Module in which to start the search.. |
2999 | svoboda | 114 | * @param mod (output) Will be filled with a pointer to the module |
115 | * that contains the symbol. |
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116 | */ |
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3689 | svoboda | 117 | elf_symbol_t *symbol_bfs_find(char *name, module_t *start, module_t **mod) |
2980 | svoboda | 118 | { |
3000 | svoboda | 119 | module_t *m, *dm; |
120 | elf_symbol_t *sym, *s; |
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121 | link_t queue_head; |
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122 | size_t i; |
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2980 | svoboda | 123 | |
3000 | svoboda | 124 | /* |
125 | * Do a BFS using the queue_link and bfs_tag fields. |
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126 | * Vertices (modules) are tagged the moment they are inserted |
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127 | * into the queue. This prevents from visiting the same vertex |
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128 | * more times in case of circular dependencies. |
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129 | */ |
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130 | |||
131 | /* Mark all vertices (modules) as unvisited */ |
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132 | modules_untag(); |
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133 | |||
134 | /* Insert root (the program) into the queue and tag it */ |
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135 | list_initialize(&queue_head); |
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3689 | svoboda | 136 | start->bfs_tag = true; |
137 | list_append(&start->queue_link, &queue_head); |
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3000 | svoboda | 138 | |
139 | /* If the symbol is found, it will be stored in 'sym' */ |
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140 | sym = NULL; |
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141 | |||
142 | /* While queue is not empty */ |
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143 | while (!list_empty(&queue_head)) { |
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144 | /* Pop first element from the queue */ |
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145 | m = list_get_instance(queue_head.next, module_t, queue_link); |
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146 | list_remove(&m->queue_link); |
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147 | |||
148 | s = def_find_in_module(name, m); |
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149 | if (s != NULL) { |
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150 | /* Symbol found */ |
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151 | sym = s; |
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2999 | svoboda | 152 | *mod = m; |
3000 | svoboda | 153 | break; |
2999 | svoboda | 154 | } |
2980 | svoboda | 155 | |
3000 | svoboda | 156 | /* |
157 | * Insert m's untagged dependencies into the queue |
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158 | * and tag them. |
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159 | */ |
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160 | for (i = 0; i < m->n_deps; ++i) { |
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161 | dm = m->deps[i]; |
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2999 | svoboda | 162 | |
3000 | svoboda | 163 | if (dm->bfs_tag == false) { |
164 | dm->bfs_tag = true; |
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165 | list_append(&dm->queue_link, &queue_head); |
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166 | } |
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2999 | svoboda | 167 | } |
3000 | svoboda | 168 | } |
2999 | svoboda | 169 | |
3000 | svoboda | 170 | /* Empty the queue so that we leave it in a clean state */ |
171 | while (!list_empty(&queue_head)) |
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172 | list_remove(queue_head.next); |
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173 | |||
174 | if (!sym) { |
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175 | printf("Error, symbol '%s' not found anywhere\n", name); |
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176 | exit(1); |
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177 | return NULL; /* Not found */ |
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2999 | svoboda | 178 | } |
179 | |||
3000 | svoboda | 180 | return sym; /* Symbol found */ |
2980 | svoboda | 181 | } |
182 | |||
3689 | svoboda | 183 | |
184 | /** Find the definition of a symbol.. |
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185 | * |
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186 | * By definition in System V ABI, if module origin has the flag DT_SYMBOLIC, |
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187 | * origin is searched first. Otherwise, or if the symbol hasn't been found, |
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188 | * the module dependency graph is searched breadth-first, beginning |
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189 | * from the executable program. |
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190 | * |
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191 | * @param name Name of the symbol to search for. |
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192 | * @param origin Module in which the dependency originates. |
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193 | * @param mod (output) Will be filled with a pointer to the module |
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194 | * that contains the symbol. |
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195 | */ |
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196 | elf_symbol_t *symbol_def_find(char *name, module_t *origin, module_t **mod) |
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197 | { |
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198 | module_t *m, *dm; |
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199 | elf_symbol_t *sym, *s; |
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200 | link_t queue_head; |
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201 | size_t i; |
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202 | |||
203 | if (origin->dyn.symbolic) { |
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204 | /* |
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205 | * Origin module has a DT_SYMBOLIC flag. |
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206 | * Try this module first |
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207 | */ |
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208 | s = def_find_in_module(name, origin); |
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209 | if (s != NULL) { |
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210 | /* Found */ |
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211 | *mod = origin; |
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212 | return s; |
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213 | } |
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214 | } |
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215 | |||
216 | /* Otherwise start in the executable program */ |
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217 | return symbol_bfs_find(name, runtime_env->program, mod); |
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218 | } |
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219 | |||
2998 | svoboda | 220 | uintptr_t symbol_get_addr(elf_symbol_t *sym, module_t *m) |
221 | { |
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222 | if (sym->st_shndx == SHN_ABS) { |
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223 | /* Do not add bias to absolute symbols */ |
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224 | return sym->st_value; |
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225 | } else { |
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226 | return sym->st_value + m->bias; |
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227 | } |
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228 | } |
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229 | |||
2978 | svoboda | 230 | /** @} |
231 | */ |