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1 /* |
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2 * strptr.c - implementation of the elf_strptr(3) function. |
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3 * Copyright (C) 1995 - 2007 Michael Riepe |
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4 * |
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5 * This library is free software; you can redistribute it and/or |
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6 * modify it under the terms of the GNU Library General Public |
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7 * License as published by the Free Software Foundation; either |
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8 * version 2 of the License, or (at your option) any later version. |
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9 * |
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10 * This library is distributed in the hope that it will be useful, |
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11 * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 * Library General Public License for more details. |
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14 * |
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15 * You should have received a copy of the GNU Library General Public |
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16 * License along with this library; if not, write to the Free Software |
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17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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18 */ |
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19 |
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20 #include <private.h> |
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21 |
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22 #ifndef lint |
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23 static const char rcsid[] = "@(#) $Id: strptr.c,v 1.11 2007/09/07 12:07:59 michael Exp $"; |
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24 #endif /* lint */ |
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25 |
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26 char* |
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27 elf_strptr(Elf *elf, size_t section, size_t offset) { |
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28 Elf_Data *data; |
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29 Elf_Scn *scn; |
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30 size_t n; |
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31 char *s; |
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32 |
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33 if (!elf) { |
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34 return NULL; |
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35 } |
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36 elf_assert(elf->e_magic == ELF_MAGIC); |
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37 if (!(scn = elf_getscn(elf, section))) { |
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38 return NULL; |
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39 } |
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40 if (scn->s_index == SHN_UNDEF) { |
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41 seterr(ERROR_NOSTRTAB); |
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42 return NULL; |
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43 } |
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44 /* |
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45 * checking the section header is more appropriate |
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46 */ |
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47 if (elf->e_class == ELFCLASS32) { |
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48 if (scn->s_shdr32.sh_type != SHT_STRTAB) { |
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49 seterr(ERROR_NOSTRTAB); |
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50 return NULL; |
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51 } |
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52 } |
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53 #if __LIBELF64 |
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54 else if (elf->e_class == ELFCLASS64) { |
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55 if (scn->s_shdr64.sh_type != SHT_STRTAB) { |
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56 seterr(ERROR_NOSTRTAB); |
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57 return NULL; |
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58 } |
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59 } |
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60 #endif /* __LIBELF64 */ |
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61 else if (valid_class(elf->e_class)) { |
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62 seterr(ERROR_UNIMPLEMENTED); |
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63 return NULL; |
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64 } |
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65 else { |
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66 seterr(ERROR_UNKNOWN_CLASS); |
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67 return NULL; |
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68 } |
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69 /* |
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70 * Find matching buffer |
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71 */ |
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72 n = 0; |
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73 data = NULL; |
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74 if (elf->e_elf_flags & ELF_F_LAYOUT) { |
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75 /* |
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76 * Programmer is responsible for d_off |
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77 * Note: buffers may be in any order! |
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78 */ |
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79 while ((data = elf_getdata(scn, data))) { |
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80 n = data->d_off; |
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81 if (offset >= n && offset - n < data->d_size) { |
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82 /* |
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83 * Found it |
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84 */ |
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85 break; |
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86 } |
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87 } |
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88 } |
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89 else { |
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90 /* |
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91 * Calculate offsets myself |
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92 */ |
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93 while ((data = elf_getdata(scn, data))) { |
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94 if (data->d_align > 1) { |
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95 n += data->d_align - 1; |
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96 n -= n % data->d_align; |
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97 } |
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98 if (offset < n) { |
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99 /* |
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100 * Invalid offset: points into a hole |
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101 */ |
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102 seterr(ERROR_BADSTROFF); |
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103 return NULL; |
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104 } |
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105 if (offset - n < data->d_size) { |
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106 /* |
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107 * Found it |
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108 */ |
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109 break; |
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110 } |
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111 n += data->d_size; |
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112 } |
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113 } |
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114 if (data == NULL) { |
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115 /* |
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116 * Not found |
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117 */ |
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118 seterr(ERROR_BADSTROFF); |
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119 return NULL; |
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120 } |
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121 if (data->d_buf == NULL) { |
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122 /* |
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123 * Buffer is NULL (usually the programmers' fault) |
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124 */ |
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125 seterr(ERROR_NULLBUF); |
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126 return NULL; |
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127 } |
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128 offset -= n; |
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129 s = (char*)data->d_buf; |
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130 if (!(_elf_sanity_checks & SANITY_CHECK_STRPTR)) { |
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131 return s + offset; |
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132 } |
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133 /* |
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134 * Perform extra sanity check |
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135 */ |
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136 for (n = offset; n < data->d_size; n++) { |
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137 if (s[n] == '\0') { |
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138 /* |
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139 * Return properly NUL terminated string |
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140 */ |
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141 return s + offset; |
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142 } |
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143 } |
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144 /* |
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145 * String is not NUL terminated |
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146 * Return error to avoid SEGV in application |
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147 */ |
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148 seterr(ERROR_UNTERM); |
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149 return NULL; |
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150 } |