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3092
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1 /* Virtual diry bit implementation (platform independent) 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
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30 typedef struct
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31 {
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32 Dynarr_declare (void *);
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33 } void_ptr_dynarr;
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34
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35 void_ptr_dynarr *page_fault_table;
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36
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37 /* Init page fault table and protect heap. */
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38 void
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39 vdb_start_dirty_bits_recording (void)
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40 {
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3303
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41 Elemcount protected_pages = (Elemcount) protect_heap_pages ();
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3092
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42 page_fault_table = Dynarr_new2 (void_ptr_dynarr, void *);
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3303
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43 Dynarr_resize (page_fault_table, protected_pages);
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3092
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44 }
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45
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46 /* Remove heap protection. */
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47 void
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48 vdb_stop_dirty_bits_recording (void)
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49 {
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50 unprotect_heap_pages ();
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51 }
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52
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53 /* Read page fault table and pass page faults to garbage collector. */
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54 int
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55 vdb_read_dirty_bits (void)
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56 {
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57 int repushed_objects = 0;
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58 Elemcount count;
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59 for (count = Dynarr_length (page_fault_table); count; count--)
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60 repushed_objects +=
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61 repush_all_objects_on_page (Dynarr_at (page_fault_table, count - 1));
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62 Dynarr_free (page_fault_table);
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63 page_fault_table = 0;
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64 return repushed_objects;
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65 }
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66
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67 /* Called by the page fault handler: add address to page fault table. */
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68 void
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69 vdb_designate_modified (void *addr)
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70 {
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71 Dynarr_add (page_fault_table, addr);
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72 }
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73
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74
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75 /* For testing and debugging... */
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76
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77 DEFUN ("test-vdb", Ftest_vdb, 0, 0, "", /*
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78 Test virtual dirty bit implementation. Prints results to stderr.
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79 */
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80 ())
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81 {
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82 Rawbyte *p;
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83 char c;
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84 Elemcount count;
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85
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86 /* Wrap up gc (if currently running). */
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87 gc_full ();
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88
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89 /* Allocate a buffer; it will have the default
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90 protection of PROT_READ|PROT_WRITE. */
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91 p = (Rawbyte *) mc_alloc (mc_get_page_size());
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92 set_lheader_implementation ((struct lrecord_header *) p, &lrecord_cons);
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93 fprintf (stderr, "Allocate p: [%x ... %x], length %d\n",
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94 (int) p, (int) (p + mc_get_page_size ()),
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95 (int) mc_get_page_size ());
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96
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97 /* Test read. */
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98 fprintf (stderr, "Attempt to read p[666]... ");
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99 c = p[666];
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100 fprintf (stderr, "read ok.\n");
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101
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102 /* Test write. */
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103 fprintf (stderr, "Attempt to write 42 to p[666]... ");
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104 p[666] = 42;
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105 fprintf (stderr, "write ok, p[666] = %d\n", p[666]);
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106
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107 /* Mark the buffer read-only and set environemnt for write-barrier. */
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108 fprintf (stderr, "Write-protect the page.\n");
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109 MARK_BLACK (p);
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110 vdb_start_dirty_bits_recording ();
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111 write_barrier_enabled = 1;
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112
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113 /* Test write-barrier read. */
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114 fprintf (stderr, "Attempt to read p[666]... ");
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115 c = p[666];
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116 fprintf (stderr, "read ok.\n");
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117
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118 /* Test write-barrier write, program receives SIGSEGV. */
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119 fprintf (stderr, "Attempt to write 23 to p[666]... ");
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120 p[666] = 23;
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121 fprintf (stderr, "Written p[666] = %d\n", p[666]);
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122
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123 /* Stop write-barrier mode. */
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124 write_barrier_enabled = 0;
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125 MARK_WHITE (p);
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126 vdb_unprotect (p, mc_get_page_size ());
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127 for (count = Dynarr_length (page_fault_table); count; count--)
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128 if (Dynarr_at (page_fault_table, count - 1) == &p[666])
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129 fprintf (stderr, "VALID page fault at %x\n",
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130 (int) Dynarr_at (page_fault_table, count - 1));
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131 else
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132 fprintf (stderr, "WRONG page fault at %x\n",
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133 (int) Dynarr_at (page_fault_table, count - 1));
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134 Dynarr_free (page_fault_table);
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135 mc_free (p);
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136 return Qnil;
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137 }
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138
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139 DEFUN ("test-segfault", Ftest_segfault, 0, 0, "", /*
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140 Test virtual dirty bit implementation: provoke a segfault on purpose.
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141 WARNING: this function causes a SEGFAULT on purpose and thus crashes
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142 XEmacs! This is only used for debbugging, e.g. for testing how the
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143 debugger behaves when XEmacs segfaults and the write barrier is
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144 enabled.
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145 */
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146 ())
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147 {
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148 Rawbyte *q = 0;
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149 q[0] = 23;
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150 return Qnil;
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151 }
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152
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153 void
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154 syms_of_vdb (void)
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155 {
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156 DEFSUBR (Ftest_vdb);
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157 DEFSUBR (Ftest_segfault);
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158 }
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