1 /* |
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2 * Copyright (c) 2012, 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 /* |
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26 * Name: fix_empty_sec_hdr_flags.c |
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27 * |
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28 * Description: Remove the SHF_ALLOC flag from "empty" section headers. |
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29 * An "empty" section header has sh_addr == 0 and sh_size == 0. |
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30 * |
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31 * This program is adapted from the example program shown on the |
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32 * elf(3elf) man page and from code from the Solaris compiler |
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33 * driver. |
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34 */ |
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35 |
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36 #include <fcntl.h> |
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37 #include <stdio.h> |
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38 #include <libelf.h> |
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39 #include <stdlib.h> |
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40 #include <string.h> |
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41 #include <unistd.h> |
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42 |
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43 static void failure(void); |
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44 |
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45 void |
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46 main(int argc, char ** argv) { |
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47 void * ehdr; /* ELF header */ |
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48 unsigned int i; /* section counter */ |
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49 int fd; /* descriptor for file */ |
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50 Elf * elf; /* ELF descriptor */ |
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51 char * elf_ident; /* ELF identity string */ |
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52 char * elf_obj; /* elf_obj file */ |
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53 int fix_count; /* number of flags fixed */ |
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54 int is_elfclass64; /* is an ELFCLASS64 file? */ |
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55 Elf_Scn * scn; /* ELF section descriptor */ |
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56 void * shdr; /* ELF section header */ |
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57 Elf_Data * shstrtab; /* ELF section header string table */ |
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58 |
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59 if (argc != 2) { |
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60 (void) fprintf(stderr, "Usage: %s elf_obj\n", argv[0]); |
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61 exit(2); |
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62 } |
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63 |
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64 /* open the elf_obj */ |
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65 elf_obj = argv[1]; |
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66 if ((fd = open(elf_obj, O_RDWR)) == -1) { |
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67 (void) fprintf(stderr, "%s: cannot open file.\n", elf_obj); |
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68 exit(3); |
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69 } |
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70 |
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71 (void) printf("Opening '%s' for update\n", elf_obj); |
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72 (void) fflush(stdout); |
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73 (void) elf_version(EV_CURRENT); /* coordinate ELF versions */ |
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74 |
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75 /* obtain the ELF descriptors from the input file */ |
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76 if ((elf = elf_begin(fd, ELF_C_RDWR, NULL)) == NULL) { |
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77 failure(); |
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78 } |
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79 |
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80 /* determine if ELFCLASS64 or not? */ |
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81 elf_ident = elf_getident(elf, NULL); |
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82 is_elfclass64 = (elf_ident[EI_CLASS] == ELFCLASS64); |
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83 |
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84 /* get the ELF header */ |
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85 if (is_elfclass64) { |
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86 ehdr = elf64_getehdr(elf); |
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87 } else { |
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88 ehdr = elf32_getehdr(elf); |
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89 } |
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90 if (ehdr == NULL) { |
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91 failure(); |
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92 } |
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93 |
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94 /* get the ELF section descriptor */ |
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95 if (is_elfclass64) { |
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96 scn = elf_getscn(elf, ((Elf64_Ehdr *) ehdr)->e_shstrndx); |
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97 } else { |
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98 scn = elf_getscn(elf, ((Elf32_Ehdr *) ehdr)->e_shstrndx); |
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99 } |
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100 if (scn == NULL) { |
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101 failure(); |
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102 } |
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103 |
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104 /* get the section header string table */ |
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105 shstrtab = elf_getdata(scn, NULL); |
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106 if (shstrtab == NULL) { |
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107 failure(); |
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108 } |
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109 |
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110 fix_count = 0; |
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111 |
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112 /* traverse the sections of the input file */ |
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113 for (i = 1, scn = NULL; scn = elf_nextscn(elf, scn); i++) { |
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114 int has_flag_set; /* is SHF_ALLOC flag set? */ |
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115 int is_empty; /* is section empty? */ |
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116 char * name; /* short hand pointer */ |
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117 |
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118 /* get the section header */ |
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119 if (is_elfclass64) { |
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120 shdr = elf64_getshdr(scn); |
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121 } else { |
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122 shdr = elf32_getshdr(scn); |
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123 } |
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124 if (shdr == NULL) { |
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125 failure(); |
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126 } |
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127 |
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128 if (is_elfclass64) { |
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129 name = (char *)shstrtab->d_buf + ((Elf64_Shdr *) shdr)->sh_name; |
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130 } else { |
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131 name = (char *)shstrtab->d_buf + ((Elf32_Shdr *) shdr)->sh_name; |
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132 } |
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133 |
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134 if (is_elfclass64) { |
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135 has_flag_set = ((Elf64_Shdr *) shdr)->sh_flags & SHF_ALLOC; |
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136 is_empty = ((Elf64_Shdr *) shdr)->sh_addr == 0 && |
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137 ((Elf64_Shdr *) shdr)->sh_size == 0; |
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138 } else { |
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139 has_flag_set = ((Elf32_Shdr *) shdr)->sh_flags & SHF_ALLOC; |
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140 is_empty = ((Elf32_Shdr *) shdr)->sh_addr == 0 && |
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141 ((Elf32_Shdr *) shdr)->sh_size == 0; |
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142 } |
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143 |
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144 if (is_empty && has_flag_set) { |
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145 (void) printf("section[%u] '%s' is empty, " |
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146 "but SHF_ALLOC flag is set.\n", i, name); |
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147 (void) printf("Clearing the SHF_ALLOC flag.\n"); |
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148 |
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149 if (is_elfclass64) { |
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150 ((Elf64_Shdr *) shdr)->sh_flags &= ~SHF_ALLOC; |
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151 } else { |
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152 ((Elf32_Shdr *) shdr)->sh_flags &= ~SHF_ALLOC; |
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153 } |
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154 fix_count++; |
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155 } |
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156 } /* end for each ELF section */ |
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157 |
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158 if (fix_count > 0) { |
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159 (void) printf("Saving %d updates to '%s'\n", fix_count, elf_obj); |
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160 (void) fflush(stdout); |
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161 (void) elf_update(elf, ELF_C_NULL); /* recalc ELF memory structures */ |
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162 (void) elf_update(elf, ELF_C_WRITE); /* write out changes to ELF obj */ |
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163 } else { |
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164 (void) printf("No SHF_ALLOC flags needed to be cleared.\n"); |
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165 } |
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166 |
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167 (void) elf_end(elf); /* done with ELF obj */ |
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168 (void) close(fd); |
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169 |
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170 (void) printf("Done %s '%s'\n", |
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171 (fix_count > 0) ? "updating" : "with", elf_obj); |
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172 (void) fflush(stdout); |
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173 exit(0); |
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174 } /* end main */ |
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175 |
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176 |
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177 static void |
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178 failure() { |
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179 (void) fprintf(stderr, "%s\n", elf_errmsg(elf_errno())); |
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180 exit(6); |
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181 } |
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