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3092
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1 /* Virtual diry bit implementation for XEmacs.
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2 Copyright (C) 2005 Marcus Crestani.
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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 in FSF. */
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22
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23 #include <config.h>
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24 #include "lisp.h"
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25 #include "gc.h"
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26 #include "mc-alloc.h"
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27 #include "vdb.h"
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28
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29 #include <errno.h>
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30 #include <signal.h>
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31 #include <sys/mman.h>
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32
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33 #if defined (HAVE_SIGACTION)
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34 # if defined (HAVE_STRUCT_SIGINFO_SI_ADDR)
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35 # define FAULT_HANDLER_ARGUMENTS \
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36 int signum, struct siginfo *siginfo, void *UNUSED (ctx)
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37 # define GET_FAULT_ADDRESS siginfo->si_addr
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38 # elif defined (HAVE_SIGINFO_T_SI_ADDR)
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39 # define FAULT_HANDLER_ARGUMENTS \
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40 int signum, siginfo_t *siginfo, void *UNUSED (ctx)
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41 # define GET_FAULT_ADDRESS siginfo->si_addr
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42 # endif
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43 # define USE_SIGACTION
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44 # define FAULT_HANDLER_REMOVE_HANDLER
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45 #elif defined (HAVE_SIGNAL)
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46 # define FAULT_HANDLER_ARGUMENTS int signum, struct sigcontext sc
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47 # define GET_FAULT_ADDRESS (void *) sc.cr2
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48 # define USE_SIGNAL
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49 #endif
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50
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51
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52 #ifdef USE_SIGACTION
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53 struct sigaction act, segv_oact, bus_oact;
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54 #endif /* USE_SIGACTION */
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55
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56 #ifdef USE_SIGNAL
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57 sighandler_t segv_oact, bus_oact;
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58 #endif /* USE_SIGNAL */
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59
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60 void vdb_remove_signal_handler (void);
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61
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62 void
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63 vdb_fault_handler (FAULT_HANDLER_ARGUMENTS)
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64 {
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65 if (write_barrier_enabled
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66 && (fault_on_protected_page (GET_FAULT_ADDRESS)))
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67 {
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68 vdb_designate_modified (GET_FAULT_ADDRESS);
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69 unprotect_page_and_mark_dirty (GET_FAULT_ADDRESS);
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70 #ifdef FAULT_HANDLER_REINSTALL_HANDLER
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71 vdb_install_signal_handler ();
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72 #endif /* FAULT_HANDLER_REINSTALL_HANDLER */
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73 }
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74 else /* default sigsegv handler */
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75 {
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76 char *signal_name;
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77 if (signum == SIGSEGV)
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78 signal_name = "SIGSEGV";
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79 else if (signum == SIGBUS)
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80 signal_name = "SIGBUS";
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81 else
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82 ABORT (); /* something weird happened: wrong signal caught */
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83 fprintf (stderr, "\n\nFatal Error: Received %s (%d) for address 0x%x\n",
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84 signal_name, signum, (int) GET_FAULT_ADDRESS);
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85 #ifdef FAULT_HANDLER_CALL_PREVIOUS_HANDLER
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86 if (signum == SIGSEGV)
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87 segv_oact (signum);
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88 else if (signum == SIGBUS)
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89 bus_oact (signum);
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90 #endif /* FAULT_HANDLER_CALL_PREVIOUS_HANDLER */
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91 #ifdef FAULT_HANDLER_REMOVE_HANDLER
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92 vdb_remove_signal_handler ();
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93 #endif /* FAULT_HANDLER_REMOVE_HANDLER */
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94 }
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95 }
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96
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97 void
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98 vdb_remove_signal_handler (void)
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99 {
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100 #ifdef USE_SIGACTION
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101 sigaction(SIGSEGV, &segv_oact, 0);
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102 sigaction(SIGBUS, &bus_oact, 0);
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103 #endif /* USE_SIGACTION */
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104 #ifdef USE_SIGNAL
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105 signal (SIGSEGV, segv_oact);
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106 signal (SIGBUS, bus_oact);
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107 #endif
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108 }
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109
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110 void
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111 vdb_install_signal_handler (void)
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112 {
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113 /* See init_signals_very_early () in signal.c. */
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114 if (noninteractive && !initialized)
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115 {
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116 allow_incremental_gc = 0;
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117 return;
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118 }
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119
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120 #ifdef USE_SIGACTION
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3307
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121 memset(&act, 0, sizeof(struct sigaction));
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3092
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122 act.sa_sigaction = vdb_fault_handler;
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123 sigemptyset (&act.sa_mask);
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124 act.sa_flags = SA_SIGINFO;
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125 sigaction (SIGSEGV, &act, &segv_oact);
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126 sigaction (SIGBUS, &act, &bus_oact);
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127 allow_incremental_gc = 1;
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128 #endif /* USE_SIGACTION */
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129 #ifdef USE_SIGNAL
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130 segv_oact = signal (SIGSEGV, (void (*)(int)) vdb_fault_handler);
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131 bus_oact = signal (SIGBUS, (void (*)(int)) vdb_fault_handler);
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132 #endif /* USE_SIGNAL */
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133 }
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134
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135 void
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136 vdb_protect (void *ptr, EMACS_INT len)
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137 {
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138 if (mprotect (ptr, len, PROT_READ))
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139 {
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140 perror ("Couldn't mprotect");
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141 ABORT ();
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142 }
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143 }
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144
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145 void
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146 vdb_unprotect (void *ptr, EMACS_INT len)
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147 {
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148 if (mprotect (ptr, len, PROT_READ | PROT_WRITE))
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149 {
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150 perror ("Couldn't mprotect");
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151 ABORT ();
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152 }
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153 }
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