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428
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1 /* Unexec for HP 9000 Series 800 machines.
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2 Bob Desinger <hpsemc!bd@hplabs.hp.com>
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3
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4 This file is part of XEmacs.
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5
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6 XEmacs is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by the
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8 Free Software Foundation; either version 2, or (at your option) any
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9 later version.
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10
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11 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with XEmacs; see the file COPYING. If not, write to
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18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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19 Boston, MA 02111-1307, USA. */
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20
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21 /* Synched up with: Not synched with FSF. */
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22
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23 /*
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24
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25 Unexec creates a copy of the old a.out file, and replaces the old data
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26 area with the current data area. When the new file is executed, the
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27 process will see the same data structures and data values that the
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28 original process had when unexec was called.
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29
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30 Unlike other versions of unexec, this one copies symbol table and
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31 debug information to the new a.out file. Thus, the new a.out file
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32 may be debugged with symbolic debuggers.
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33
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34 If you fix any bugs in this, I'd like to incorporate your fixes.
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35 Send them to uunet!hpda!hpsemc!jmorris or jmorris%hpsemc@hplabs.HP.COM.
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36
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37 CAVEATS:
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38 This routine saves the current value of all static and external
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39 variables. This means that any data structure that needs to be
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40 initialized must be explicitly reset. Variables will not have their
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41 expected default values.
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42
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43 Unfortunately, the HP-UX signal handler has internal initialization
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44 flags which are not explicitly reset. Thus, for signals to work in
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45 conjunction with this routine, the following code must executed when
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46 the new process starts up.
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47
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48 void _sigreturn();
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49 ...
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50 sigsetreturn(_sigreturn);
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51 */
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52
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53
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54 #include <config.h>
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55 #include <stdio.h>
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56 #include <fcntl.h>
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57 #include <errno.h>
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58
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59 #include <a.out.h>
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60
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61 /*
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62 * Minor modification to enable dumping with shared libraries added by
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63 * Dipankar Gupta (dg@hplb.hpl.hp.com). I studied Oliver Laumann's
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64 * more elaborate dynamic loading scheme in ELK while implementing
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65 * this, but don't use any of his machinery.
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66 *
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67 * Stores the BRK value at dump time, and uses the RUN_TIME_REMAP hook
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68 * to break back to the stored value when the dumped executable is restarted.
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69 *
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70 * CAVEATS (addenda):
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71 * 1. Text area of the shlibs are not stored. Thus, if a shared library is
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72 * replaced between the time of dump and execution, all bets are off.
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73 *
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74 * 2. Assumes that the data and bss area are adjacent, which is true of the
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75 * current VM implementation.
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76 *
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77 * 3. Any setup that defines HPUX_USE_SHLIBS *must* also define
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78 * RUN_TIME_REMAP.
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79 */
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80
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81 #ifdef HPUX_USE_SHLIBS
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82 #include <dl.h> /* User-space dynamic loader entry points */
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83 void Save_Shared_Data();
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84 int run_time_remap();
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85 #endif
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86
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87 #define min(x,y) ( ((x)<(y))?(x):(y) )
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88
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89 void write_header(int file, struct header *hdr, struct som_exec_auxhdr *auxhdr);
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90 void read_header (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr);
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91 void save_data_space (int file, struct header *hdr,
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92 struct som_exec_auxhdr *auxhdr, int size);
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93 void copy_rest (int old, int new);
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94 void copy_file (int old, int new, int size);
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95 void update_file_ptrs(int file, struct header *hdr,
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96 struct som_exec_auxhdr *auxhdr,
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97 unsigned int location, int offset);
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98 int calculate_checksum(struct header *hdr);
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99
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100 /* Create a new a.out file, same as old but with current data space */
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101 int
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102 unexec(char new_name[], /* name of the new a.out file to be created */
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103 char old_name[], /* name of the old a.out file */
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104 char *new_end_of_text, /* ptr to new edata/etext; NOT USED YET */
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105 int dummy1, int dummy2) /* not used by emacs */
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106 {
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107 int old, new;
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108 int old_size, new_size;
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109 struct header hdr;
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110 struct som_exec_auxhdr auxhdr;
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111 long i;
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112
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113 /* For the greatest flexibility, should create a temporary file in
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114 the same directory as the new file. When everything is complete,
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115 rename the temp file to the new name.
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116 This way, a program could update its own a.out file even while
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117 it is still executing. If problems occur, everything is still
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118 intact. NOT implemented. */
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119
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120 /* Open the input and output a.out files */
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121 old = open (old_name, O_RDONLY);
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122 if (old < 0)
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123 { perror(old_name); exit(1); }
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124 new = open (new_name, O_CREAT|O_RDWR|O_TRUNC, 0777);
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125 if (new < 0)
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126 { perror(new_name); exit(1); }
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127
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128 /* Read the old headers */
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129 read_header(old, &hdr, &auxhdr);
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130
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131 #ifdef HPUX_USE_SHLIBS
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132 Save_Shared_Data(); /* Save break value (added: dg@hplb.hpl.hp.com) */
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133 #endif
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134 /* Decide how large the new and old data areas are */
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135 old_size = auxhdr.exec_dsize;
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136 /* I suspect these two statements are separate
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137 to avoid a compiler bug in hpux version 8. */
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138 i = (long) sbrk (0);
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139 new_size = i - auxhdr.exec_dmem;
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140
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141 /* Copy the old file to the new, up to the data space */
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142 lseek(old, 0, 0);
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143 copy_file(old, new, auxhdr.exec_dfile);
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144
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145 /* Skip the old data segment and write a new one */
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146 lseek(old, old_size, 1);
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147 save_data_space(new, &hdr, &auxhdr, new_size);
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148
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149 /* Copy the rest of the file */
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150 copy_rest(old, new);
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151
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152 /* Update file pointers since we probably changed size of data area */
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153 update_file_ptrs(new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size);
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154
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155 /* Save the modified header */
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156 write_header(new, &hdr, &auxhdr);
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157
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158 /* Close the binary file */
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159 close (old);
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160 close (new);
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161 return 0;
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162 }
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163
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164 /* Save current data space in the file, update header. */
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165
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166 void
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167 save_data_space (int file, struct header *hdr,
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168 struct som_exec_auxhdr *auxhdr, int size)
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169 {
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170 /* Write the entire data space out to the file */
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171 if (write(file, (void *)auxhdr->exec_dmem, size) != size)
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172 { perror("Can't save new data space"); exit(1); }
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173
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174 /* Update the header to reflect the new data size */
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175 auxhdr->exec_dsize = size;
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176 auxhdr->exec_bsize = 0;
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177 }
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178
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179 /* Update the values of file pointers when something is inserted. */
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180
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181 void
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182 update_file_ptrs(int file, struct header *hdr,
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183 struct som_exec_auxhdr *auxhdr,
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184 unsigned int location, int offset)
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185 {
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186 struct subspace_dictionary_record subspace;
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187 int i;
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188
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189 /* Increase the overall size of the module */
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190 hdr->som_length += offset;
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191
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192 /* Update the various file pointers in the header */
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193 #define update(ptr) if (ptr > location) ptr = ptr + offset
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194 update(hdr->aux_header_location);
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195 update(hdr->space_strings_location);
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196 update(hdr->init_array_location);
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197 update(hdr->compiler_location);
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198 update(hdr->symbol_location);
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199 update(hdr->fixup_request_location);
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200 update(hdr->symbol_strings_location);
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201 update(hdr->unloadable_sp_location);
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202 update(auxhdr->exec_tfile);
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203 update(auxhdr->exec_dfile);
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204
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205 /* Do for each subspace dictionary entry */
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206 lseek(file, hdr->subspace_location, 0);
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207 for (i = 0; i < hdr->subspace_total; i++)
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208 {
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209 if (read(file, &subspace, sizeof(subspace)) != sizeof(subspace))
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210 { perror("Can't read subspace record"); exit(1); }
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211
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212 /* If subspace has a file location, update it */
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213 if (subspace.initialization_length > 0
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214 && subspace.file_loc_init_value > location)
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215 {
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216 subspace.file_loc_init_value += offset;
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217 lseek(file, -sizeof(subspace), 1);
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218 if (write(file, &subspace, sizeof(subspace)) != sizeof(subspace))
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219 { perror("Can't update subspace record"); exit(1); }
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220 }
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221 }
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222
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223 /* Do for each initialization pointer record */
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224 /* (I don't think it applies to executable files, only relocatables) */
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225 #undef update
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226 }
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227
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228 /* Read in the header records from an a.out file. */
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229
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230 void
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231 read_header(int file, struct header *hdr, struct som_exec_auxhdr *auxhdr)
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232 {
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233
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234 /* Read the header in */
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235 lseek(file, 0, 0);
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236 if (read(file, hdr, sizeof(*hdr)) != sizeof(*hdr))
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237 { perror("Couldn't read header from a.out file"); exit(1); }
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238
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239 if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC
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240 && hdr->a_magic != DEMAND_MAGIC)
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241 {
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242 fprintf(stderr, "a.out file doesn't have legal magic number\n");
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243 exit(1);
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244 }
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245
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246 lseek(file, hdr->aux_header_location, 0);
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247 if (read(file, auxhdr, sizeof(*auxhdr)) != sizeof(*auxhdr))
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248 {
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249 perror("Couldn't read auxiliary header from a.out file");
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250 exit(1);
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251 }
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252 }
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253
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254 /* Write out the header records into an a.out file. */
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255 void
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256 write_header(int file, struct header *hdr, struct som_exec_auxhdr *auxhdr)
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257 {
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258 /* Update the checksum */
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259 hdr->checksum = calculate_checksum(hdr);
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260
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261 /* Write the header back into the a.out file */
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262 lseek(file, 0, 0);
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263 if (write(file, hdr, sizeof(*hdr)) != sizeof(*hdr))
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264 { perror("Couldn't write header to a.out file"); exit(1); }
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265 lseek(file, hdr->aux_header_location, 0);
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266 if (write(file, auxhdr, sizeof(*auxhdr)) != sizeof(*auxhdr))
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267 { perror("Couldn't write auxiliary header to a.out file"); exit(1); }
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268 }
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269
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270 /* Calculate the checksum of a SOM header record. */
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271 int
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272 calculate_checksum(struct header *hdr)
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273 {
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274 int checksum, i, *ptr;
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275
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276 checksum = 0; ptr = (int *) hdr;
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277
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278 for (i=0; i<sizeof(*hdr)/sizeof(int)-1; i++)
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279 checksum ^= ptr[i];
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280
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281 return(checksum);
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282 }
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283
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284 /* Copy size bytes from the old file to the new one. */
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285 void
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286 copy_file (int old, int new, int size)
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287 {
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288 int len;
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289 int buffer[8192]; /* word aligned will be faster */
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290
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291 for (; size > 0; size -= len)
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292 {
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293 len = min(size, sizeof(buffer));
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294 if (read(old, buffer, len) != len)
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295 { perror("Read failure on a.out file"); exit(1); }
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296 if (write(new, buffer, len) != len)
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297 { perror("Write failure in a.out file"); exit(1); }
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298 }
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299 }
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300
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301 /* Copy the rest of the file, up to EOF. */
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302 void
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303 copy_rest (int old, int new)
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304 {
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305 int buffer[4096];
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306 int len;
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307
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308 /* Copy bytes until end of file or error */
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309 while ( (len = read(old, buffer, sizeof(buffer))) > 0)
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310 if (write(new, buffer, len) != len) break;
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311
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312 if (len != 0)
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313 { perror("Unable to copy the rest of the file"); exit(1); }
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314 }
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315
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316 #ifdef DEBUG
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317 display_header(struct header *hdr, struct som_exec_auxhdr *auxhdr)
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318 {
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319 /* Display the header information (debug) */
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320 printf("\n\nFILE HEADER\n");
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321 printf("magic number %d \n", hdr->a_magic);
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322 printf("text loc %.8x size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize);
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323 printf("data loc %.8x size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize);
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324 printf("entry %x \n", auxhdr->exec_entry);
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325 printf("Bss segment size %u\n", auxhdr->exec_bsize);
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326 printf("\n");
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327 printf("data file loc %d size %d\n",
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328 auxhdr->exec_dfile, auxhdr->exec_dsize);
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329 printf("som_length %d\n", hdr->som_length);
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330 printf("unloadable sploc %d size %d\n",
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331 hdr->unloadable_sp_location, hdr->unloadable_sp_size);
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332 }
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333 #endif /* DEBUG */
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334
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335 #ifdef HPUX_USE_SHLIBS
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336 /* Added machinery for shared libs... see comments at the beginning of this file. */
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337
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338 void *Brk_On_Dump = 0; /* Brk value to restore... stored as a global */
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339
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340 void Save_Shared_Data () {
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341 Brk_On_Dump = sbrk( 0 );
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342 }
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343
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344 void Restore_Shared_Data () {
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345 brk ( Brk_On_Dump );
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346 }
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347
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348 int run_time_remap (int d) {
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349 Restore_Shared_Data();
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350 }
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351
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352 /* run_time_remap is the magic called by startup code in the dumped executable
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353 * if RUN_TIME_REMAP is set.
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354 */
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355 #endif /* HPUX_USE_SHLIBS */
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