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2933 | 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 | |||
2965 | svoboda | 37 | #include <elf_dyn.h> |
38 | #include <rtld.h> |
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39 | |||
2952 | svoboda | 40 | void __main(void); |
41 | void __io_init(void); |
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42 | void __exit(void); |
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43 | |||
2933 | svoboda | 44 | static void kputint(unsigned i) |
45 | { |
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46 | unsigned dummy; |
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47 | asm volatile ( |
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48 | "movl $30, %%eax;" |
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49 | "int $0x30" |
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50 | : "=d" (dummy) /* output - %edx clobbered */ |
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51 | : "d" (i) /* input */ |
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52 | : "%eax","%ecx" /* all scratch registers clobbered */ |
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53 | ); |
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54 | } |
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55 | |||
56 | void __bootstrap(void) |
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57 | { |
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58 | unsigned bias; |
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59 | unsigned *got; |
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2965 | svoboda | 60 | elf_dyn_t *dynamic; |
61 | void *dptr; |
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2933 | svoboda | 62 | unsigned dval; |
63 | int i; |
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64 | |||
2965 | svoboda | 65 | size_t rel_entries; |
66 | size_t r_offset; |
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67 | elf_word r_info; |
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2933 | svoboda | 68 | unsigned rel_type; |
2965 | svoboda | 69 | elf_word sym_idx; |
70 | uintptr_t sym_addr; |
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2933 | svoboda | 71 | |
2965 | svoboda | 72 | elf_symbol_t *sym_table; |
73 | elf_rel_t *rel_table; |
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74 | elf_rel_t *jmp_rel_table; |
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75 | size_t jmp_rel_entries; |
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2933 | svoboda | 76 | |
77 | asm volatile ( |
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78 | /* Calculate the bias into %0 */ |
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2952 | svoboda | 79 | /* Generates "fake" R_386_RELATIVE run-time relocation */ |
2933 | svoboda | 80 | " call .L0;" |
81 | ".L0: pop %0;" |
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82 | " subl $.L0, %0;" |
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83 | |||
84 | /* Calculate run-time address of _DYNAMIC into %1 */ |
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2952 | svoboda | 85 | /* Generates "fake" R_386_RELATIVE run-time relocation */ |
2933 | svoboda | 86 | " movl $_DYNAMIC, %1;" /* Again, at link time 0-based VMA gets in */ |
87 | " addl %0, %1;" /* Add bias to compute run-time address */ |
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88 | |||
89 | : "=r" (bias), "=r" (dynamic) |
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90 | ); |
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91 | |||
92 | kputint(bias); |
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93 | kputint((unsigned)dynamic); |
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94 | |||
95 | /* parse DYNAMIC */ |
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96 | got = 0; |
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97 | sym_table = 0; |
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98 | rel_table = 0; |
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99 | rel_entries = 0; |
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2952 | svoboda | 100 | jmp_rel_table = 0; |
101 | jmp_rel_entries = 0; |
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2933 | svoboda | 102 | |
103 | i = 0; |
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104 | while (dynamic[i].d_tag != 0) { |
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2965 | svoboda | 105 | dptr = (void *)(dynamic[i].d_un.d_val + bias); |
2933 | svoboda | 106 | dval = dynamic[i].d_un.d_val; |
107 | |||
108 | switch (dynamic[i].d_tag) { |
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2952 | svoboda | 109 | case 2/* DT_PLTRELSZ */: jmp_rel_entries = dval/8; break; |
110 | case 23/* DT_JMPREL */: jmp_rel_table = dptr; break; |
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2933 | svoboda | 111 | case 3 /* DT_PLTGOT */: |
112 | /* GOT address */ |
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113 | got = dptr; break; |
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114 | case 6 /* DT_SYMTAB */ : sym_table = dptr; break; |
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115 | case 17 /* DT_REL */ : rel_table = dptr; break; |
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116 | case 18 /* DT_RELSZ */ : rel_entries = dval / 8; break; |
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117 | default: break; |
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118 | } |
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119 | |||
120 | ++i; |
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121 | } |
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122 | |||
123 | kputint(1); |
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124 | kputint((unsigned)sym_table); |
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125 | kputint((unsigned)rel_table); |
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126 | kputint((unsigned)rel_entries); |
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127 | |||
128 | /* Now relocate all our dynsyms */ |
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129 | kputint(-1); |
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130 | |||
131 | for (i=0; i<rel_entries; i++) { |
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132 | kputint(i); |
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133 | r_offset = rel_table[i].r_offset; |
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134 | r_info = rel_table[i].r_info; |
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135 | |||
136 | rel_type = ELF32_R_TYPE(r_info); |
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137 | |||
138 | kputint(rel_type); |
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139 | kputint(r_offset); |
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140 | |||
2952 | svoboda | 141 | switch (rel_type) { |
142 | case 6: /* R_386_GLOB_DAT */ |
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143 | case 7: /* R_386_JUMP_SLOT */ |
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2933 | svoboda | 144 | kputint(16); |
145 | sym_idx = ELF32_R_SYM(r_info); |
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146 | |||
147 | sym_addr = sym_table[sym_idx].st_value + bias; |
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148 | kputint(sym_idx); |
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149 | kputint(sym_addr); |
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150 | |||
151 | *(unsigned *)(r_offset+bias) = sym_addr; |
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2952 | svoboda | 152 | break; |
153 | |||
154 | case 1: /* R_386_32 */ |
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155 | kputint(16); |
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156 | sym_idx = ELF32_R_SYM(r_info); |
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157 | |||
158 | sym_addr = sym_table[sym_idx].st_value + bias; |
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159 | kputint(sym_idx); |
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160 | kputint(sym_addr); |
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161 | |||
162 | *(unsigned *)(r_offset+bias) += sym_addr; |
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163 | break; |
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164 | |||
165 | case 8: /* R_386_RELATIVE */ |
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166 | kputint(16); |
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167 | *(unsigned *)(r_offset+bias) += bias; |
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168 | break; |
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2933 | svoboda | 169 | } |
170 | } |
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171 | |||
172 | kputint(-1); |
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2952 | svoboda | 173 | |
174 | for (i=0; i<jmp_rel_entries; i++) { |
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175 | kputint(i); |
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176 | r_offset = jmp_rel_table[i].r_offset; |
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177 | r_info = jmp_rel_table[i].r_info; |
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2933 | svoboda | 178 | |
2952 | svoboda | 179 | rel_type = ELF32_R_TYPE(r_info); |
2933 | svoboda | 180 | |
2952 | svoboda | 181 | kputint(rel_type); |
182 | kputint(r_offset); |
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183 | |||
184 | switch (rel_type) { |
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185 | case 6: /* R_386_GLOB_DAT */ |
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186 | case 7: /* R_386_JUMP_SLOT */ |
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187 | kputint(16); |
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188 | sym_idx = ELF32_R_SYM(r_info); |
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189 | |||
190 | sym_addr = sym_table[sym_idx].st_value + bias; |
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191 | kputint(sym_idx); |
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192 | kputint(sym_addr); |
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193 | |||
194 | *(unsigned *)(r_offset+bias) = sym_addr; |
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195 | break; |
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196 | |||
197 | case 1: /* R_386_32 */ |
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198 | kputint(16); |
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199 | sym_idx = ELF32_R_SYM(r_info); |
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200 | |||
201 | sym_addr = sym_table[sym_idx].st_value + bias; |
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202 | kputint(sym_idx); |
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203 | kputint(sym_addr); |
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204 | |||
205 | *(unsigned *)(r_offset+bias) += sym_addr; |
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206 | break; |
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207 | |||
208 | case 8: /* R_386_RELATIVE */ |
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209 | kputint(16); |
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210 | *(unsigned *)(r_offset+bias) += bias; |
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211 | break; |
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212 | } |
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213 | } |
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214 | |||
215 | kputint(-1); |
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216 | |||
217 | /* Init libc and run rtld main */ |
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218 | __main(); |
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219 | |||
220 | kputint(33); |
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221 | __io_init(); |
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222 | kputint(34); |
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2933 | svoboda | 223 | _rtld_main(); |
2952 | svoboda | 224 | kputint(35); |
225 | __exit(); |
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2933 | svoboda | 226 | |
2952 | svoboda | 227 | kputint(36); |
228 | |||
2933 | svoboda | 229 | asm ( |
230 | "movl $250, %%eax;" |
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231 | "int $0x30" |
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232 | : /* output */ |
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233 | : /* input */ |
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234 | : "%eax","%ecx","%edx" /* all scratch registers clobbered */ |
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235 | ); |
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236 | } |
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237 | |||
238 | /** @} |
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239 | */ |