1 | /* |
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2 | * various helper functions to access elf structures |
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3 | */ |
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4 | |
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5 | #include "libelf-private.h" |
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6 | |
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7 | /* ------------------------------------------------------------------------ */ |
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8 | |
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9 | uint64_t elf_access_unsigned(struct elf_binary * elf, const void *ptr, |
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10 | uint64_t offset, size_t size) |
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11 | { |
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12 | int need_swap = elf_swap(elf); |
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13 | const uint8_t *u8; |
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14 | const uint16_t *u16; |
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15 | const uint32_t *u32; |
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16 | const uint64_t *u64; |
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17 | |
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18 | switch ( size ) |
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19 | { |
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20 | case 1: |
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21 | u8 = ptr + offset; |
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22 | return *u8; |
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23 | case 2: |
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24 | u16 = ptr + offset; |
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25 | return need_swap ? bswap_16(*u16) : *u16; |
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26 | case 4: |
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27 | u32 = ptr + offset; |
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28 | return need_swap ? bswap_32(*u32) : *u32; |
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29 | case 8: |
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30 | u64 = ptr + offset; |
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31 | return need_swap ? bswap_64(*u64) : *u64; |
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32 | default: |
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33 | return 0; |
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34 | } |
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35 | } |
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36 | |
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37 | int64_t elf_access_signed(struct elf_binary *elf, const void *ptr, |
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38 | uint64_t offset, size_t size) |
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39 | { |
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40 | int need_swap = elf_swap(elf); |
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41 | const int8_t *s8; |
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42 | const int16_t *s16; |
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43 | const int32_t *s32; |
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44 | const int64_t *s64; |
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45 | |
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46 | switch ( size ) |
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47 | { |
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48 | case 1: |
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49 | s8 = ptr + offset; |
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50 | return *s8; |
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51 | case 2: |
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52 | s16 = ptr + offset; |
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53 | return need_swap ? bswap_16(*s16) : *s16; |
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54 | case 4: |
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55 | s32 = ptr + offset; |
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56 | return need_swap ? bswap_32(*s32) : *s32; |
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57 | case 8: |
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58 | s64 = ptr + offset; |
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59 | return need_swap ? bswap_64(*s64) : *s64; |
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60 | default: |
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61 | return 0; |
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62 | } |
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63 | } |
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64 | |
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65 | uint64_t elf_round_up(struct elf_binary *elf, uint64_t addr) |
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66 | { |
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67 | int elf_round = (elf_64bit(elf) ? 8 : 4) - 1; |
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68 | |
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69 | return (addr + elf_round) & ~elf_round; |
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70 | } |
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71 | |
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72 | /* ------------------------------------------------------------------------ */ |
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73 | |
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74 | int elf_shdr_count(struct elf_binary *elf) |
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75 | { |
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76 | return elf_uval(elf, elf->ehdr, e_shnum); |
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77 | } |
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78 | |
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79 | int elf_phdr_count(struct elf_binary *elf) |
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80 | { |
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81 | return elf_uval(elf, elf->ehdr, e_phnum); |
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82 | } |
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83 | |
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84 | const elf_shdr *elf_shdr_by_name(struct elf_binary *elf, const char *name) |
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85 | { |
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86 | uint64_t count = elf_shdr_count(elf); |
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87 | const elf_shdr *shdr; |
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88 | const char *sname; |
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89 | int i; |
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90 | |
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91 | for ( i = 0; i < count; i++ ) |
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92 | { |
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93 | shdr = elf_shdr_by_index(elf, i); |
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94 | sname = elf_section_name(elf, shdr); |
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95 | if ( sname && !strcmp(sname, name) ) |
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96 | return shdr; |
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97 | } |
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98 | return NULL; |
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99 | } |
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100 | |
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101 | const elf_shdr *elf_shdr_by_index(struct elf_binary *elf, int index) |
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102 | { |
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103 | uint64_t count = elf_shdr_count(elf); |
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104 | const void *ptr; |
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105 | |
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106 | if ( index >= count ) |
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107 | return NULL; |
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108 | |
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109 | ptr = (elf->image |
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110 | + elf_uval(elf, elf->ehdr, e_shoff) |
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111 | + elf_uval(elf, elf->ehdr, e_shentsize) * index); |
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112 | return ptr; |
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113 | } |
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114 | |
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115 | const elf_phdr *elf_phdr_by_index(struct elf_binary *elf, int index) |
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116 | { |
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117 | uint64_t count = elf_uval(elf, elf->ehdr, e_phnum); |
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118 | const void *ptr; |
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119 | |
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120 | if ( index >= count ) |
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121 | return NULL; |
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122 | |
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123 | ptr = (elf->image |
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124 | + elf_uval(elf, elf->ehdr, e_phoff) |
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125 | + elf_uval(elf, elf->ehdr, e_phentsize) * index); |
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126 | return ptr; |
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127 | } |
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128 | |
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129 | const char *elf_section_name(struct elf_binary *elf, const elf_shdr * shdr) |
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130 | { |
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131 | if ( elf->sec_strtab == NULL ) |
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132 | return "unknown"; |
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133 | return elf->sec_strtab + elf_uval(elf, shdr, sh_name); |
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134 | } |
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135 | |
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136 | const void *elf_section_start(struct elf_binary *elf, const elf_shdr * shdr) |
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137 | { |
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138 | return elf->image + elf_uval(elf, shdr, sh_offset); |
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139 | } |
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140 | |
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141 | const void *elf_section_end(struct elf_binary *elf, const elf_shdr * shdr) |
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142 | { |
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143 | return elf->image |
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144 | + elf_uval(elf, shdr, sh_offset) + elf_uval(elf, shdr, sh_size); |
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145 | } |
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146 | |
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147 | const void *elf_segment_start(struct elf_binary *elf, const elf_phdr * phdr) |
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148 | { |
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149 | return elf->image + elf_uval(elf, phdr, p_offset); |
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150 | } |
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151 | |
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152 | const void *elf_segment_end(struct elf_binary *elf, const elf_phdr * phdr) |
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153 | { |
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154 | return elf->image |
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155 | + elf_uval(elf, phdr, p_offset) + elf_uval(elf, phdr, p_filesz); |
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156 | } |
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157 | |
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158 | const elf_sym *elf_sym_by_name(struct elf_binary *elf, const char *symbol) |
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159 | { |
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160 | const void *ptr = elf_section_start(elf, elf->sym_tab); |
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161 | const void *end = elf_section_end(elf, elf->sym_tab); |
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162 | const elf_sym *sym; |
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163 | uint64_t info, name; |
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164 | |
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165 | for ( ; ptr < end; ptr += elf_size(elf, sym) ) |
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166 | { |
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167 | sym = ptr; |
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168 | info = elf_uval(elf, sym, st_info); |
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169 | name = elf_uval(elf, sym, st_name); |
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170 | if ( ELF32_ST_BIND(info) != STB_GLOBAL ) |
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171 | continue; |
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172 | if ( strcmp(elf->sym_strtab + name, symbol) ) |
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173 | continue; |
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174 | return sym; |
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175 | } |
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176 | return NULL; |
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177 | } |
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178 | |
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179 | const elf_sym *elf_sym_by_index(struct elf_binary *elf, int index) |
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180 | { |
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181 | const void *ptr = elf_section_start(elf, elf->sym_tab); |
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182 | const elf_sym *sym; |
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183 | |
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184 | sym = ptr + index * elf_size(elf, sym); |
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185 | return sym; |
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186 | } |
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187 | |
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188 | const char *elf_note_name(struct elf_binary *elf, const elf_note * note) |
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189 | { |
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190 | return (void *)note + elf_size(elf, note); |
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191 | } |
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192 | |
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193 | const void *elf_note_desc(struct elf_binary *elf, const elf_note * note) |
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194 | { |
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195 | int namesz = (elf_uval(elf, note, namesz) + 3) & ~3; |
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196 | |
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197 | return (void *)note + elf_size(elf, note) + namesz; |
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198 | } |
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199 | |
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200 | uint64_t elf_note_numeric(struct elf_binary *elf, const elf_note * note) |
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201 | { |
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202 | const void *desc = elf_note_desc(elf, note); |
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203 | int descsz = elf_uval(elf, note, descsz); |
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204 | |
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205 | switch (descsz) |
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206 | { |
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207 | case 1: |
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208 | case 2: |
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209 | case 4: |
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210 | case 8: |
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211 | return elf_access_unsigned(elf, desc, 0, descsz); |
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212 | default: |
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213 | return 0; |
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214 | } |
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215 | } |
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216 | const elf_note *elf_note_next(struct elf_binary *elf, const elf_note * note) |
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217 | { |
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218 | int namesz = (elf_uval(elf, note, namesz) + 3) & ~3; |
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219 | int descsz = (elf_uval(elf, note, descsz) + 3) & ~3; |
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220 | |
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221 | return (void *)note + elf_size(elf, note) + namesz + descsz; |
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222 | } |
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223 | |
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224 | /* ------------------------------------------------------------------------ */ |
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225 | |
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226 | int elf_is_elfbinary(const void *image) |
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227 | { |
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228 | const Elf32_Ehdr *ehdr = image; |
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229 | |
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230 | return IS_ELF(*ehdr); |
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231 | } |
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232 | |
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233 | int elf_phdr_is_loadable(struct elf_binary *elf, const elf_phdr * phdr) |
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234 | { |
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235 | uint64_t p_type = elf_uval(elf, phdr, p_type); |
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236 | uint64_t p_flags = elf_uval(elf, phdr, p_flags); |
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237 | |
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238 | return ((p_type == PT_LOAD) && (p_flags & (PF_W | PF_X)) != 0); |
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239 | } |
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240 | |
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241 | /* |
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242 | * Local variables: |
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243 | * mode: C |
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244 | * c-set-style: "BSD" |
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245 | * c-basic-offset: 4 |
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246 | * tab-width: 4 |
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247 | * indent-tabs-mode: nil |
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248 | * End: |
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249 | */ |
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