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111
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1 /* UndefinedBehaviorSanitizer, undefined behavior detector.
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131
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2 Copyright (C) 2013-2018 Free Software Foundation, Inc.
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111
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3 Contributed by Marek Polacek <polacek@redhat.com>
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4
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5 This file is part of GCC.
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6
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7 GCC is free software; you can redistribute it and/or modify it under
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8 the terms of the GNU General Public License as published by the Free
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9 Software Foundation; either version 3, or (at your option) any later
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10 version.
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11
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12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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15 for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with GCC; see the file COPYING3. If not see
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19 <http://www.gnu.org/licenses/>. */
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20
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21 #include "config.h"
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22 #include "system.h"
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23 #include "coretypes.h"
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24 #include "tm.h"
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25 #include "c-family/c-common.h"
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26 #include "ubsan.h"
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27 #include "c-family/c-ubsan.h"
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28 #include "stor-layout.h"
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29 #include "builtins.h"
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30 #include "gimplify.h"
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31 #include "stringpool.h"
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32 #include "attribs.h"
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33 #include "asan.h"
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34
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35 /* Instrument division by zero and INT_MIN / -1. If not instrumenting,
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36 return NULL_TREE. */
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37
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38 tree
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39 ubsan_instrument_division (location_t loc, tree op0, tree op1)
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40 {
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41 tree t, tt;
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42 tree type = TREE_TYPE (op0);
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43
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44 /* At this point both operands should have the same type,
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45 because they are already converted to RESULT_TYPE.
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46 Use TYPE_MAIN_VARIANT since typedefs can confuse us. */
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47 gcc_assert (TYPE_MAIN_VARIANT (TREE_TYPE (op0))
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48 == TYPE_MAIN_VARIANT (TREE_TYPE (op1)));
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49
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50 op0 = unshare_expr (op0);
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51 op1 = unshare_expr (op1);
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52
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53 if (TREE_CODE (type) == INTEGER_TYPE
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54 && sanitize_flags_p (SANITIZE_DIVIDE))
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55 t = fold_build2 (EQ_EXPR, boolean_type_node,
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56 op1, build_int_cst (type, 0));
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57 else if (TREE_CODE (type) == REAL_TYPE
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58 && sanitize_flags_p (SANITIZE_FLOAT_DIVIDE))
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59 t = fold_build2 (EQ_EXPR, boolean_type_node,
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60 op1, build_real (type, dconst0));
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61 else
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62 return NULL_TREE;
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63
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64 /* We check INT_MIN / -1 only for signed types. */
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65 if (TREE_CODE (type) == INTEGER_TYPE
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66 && sanitize_flags_p (SANITIZE_DIVIDE)
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67 && !TYPE_UNSIGNED (type))
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68 {
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69 tree x;
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70 tt = fold_build2 (EQ_EXPR, boolean_type_node, unshare_expr (op1),
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71 build_int_cst (type, -1));
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72 x = fold_build2 (EQ_EXPR, boolean_type_node, op0,
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73 TYPE_MIN_VALUE (type));
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74 x = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, x, tt);
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75 t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t, x);
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76 }
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77
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78 /* If the condition was folded to 0, no need to instrument
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79 this expression. */
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80 if (integer_zerop (t))
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81 return NULL_TREE;
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82
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83 /* In case we have a SAVE_EXPR in a conditional context, we need to
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84 make sure it gets evaluated before the condition. */
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85 t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), unshare_expr (op0), t);
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86 t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), unshare_expr (op1), t);
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87 if (flag_sanitize_undefined_trap_on_error)
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88 tt = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
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89 else
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90 {
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91 tree data = ubsan_create_data ("__ubsan_overflow_data", 1, &loc,
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92 ubsan_type_descriptor (type), NULL_TREE,
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93 NULL_TREE);
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94 data = build_fold_addr_expr_loc (loc, data);
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95 enum built_in_function bcode
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96 = (flag_sanitize_recover & SANITIZE_DIVIDE)
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97 ? BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW
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98 : BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW_ABORT;
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99 tt = builtin_decl_explicit (bcode);
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100 op0 = unshare_expr (op0);
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101 op1 = unshare_expr (op1);
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102 tt = build_call_expr_loc (loc, tt, 3, data, ubsan_encode_value (op0),
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103 ubsan_encode_value (op1));
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104 }
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105 t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_node);
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106
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107 return t;
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108 }
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109
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110 /* Instrument left and right shifts. */
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111
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112 tree
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113 ubsan_instrument_shift (location_t loc, enum tree_code code,
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114 tree op0, tree op1)
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115 {
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116 tree t, tt = NULL_TREE;
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117 tree type0 = TREE_TYPE (op0);
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118 tree type1 = TREE_TYPE (op1);
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119 if (!INTEGRAL_TYPE_P (type0))
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120 return NULL_TREE;
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121
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122 tree op1_utype = unsigned_type_for (type1);
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123 HOST_WIDE_INT op0_prec = TYPE_PRECISION (type0);
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124 tree uprecm1 = build_int_cst (op1_utype, op0_prec - 1);
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125
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126 op0 = unshare_expr (op0);
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127 op1 = unshare_expr (op1);
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128
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129 t = fold_convert_loc (loc, op1_utype, op1);
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130 t = fold_build2 (GT_EXPR, boolean_type_node, t, uprecm1);
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131
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132 /* If this is not a signed operation, don't perform overflow checks.
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133 Also punt on bit-fields. */
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134 if (TYPE_OVERFLOW_WRAPS (type0)
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131
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135 || maybe_ne (GET_MODE_BITSIZE (TYPE_MODE (type0)),
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136 TYPE_PRECISION (type0))
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111
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137 || !sanitize_flags_p (SANITIZE_SHIFT_BASE))
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138 ;
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139
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140 /* For signed x << y, in C99/C11, the following:
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141 (unsigned) x >> (uprecm1 - y)
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142 if non-zero, is undefined. */
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143 else if (code == LSHIFT_EXPR && flag_isoc99 && cxx_dialect < cxx11)
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144 {
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145 tree x = fold_build2 (MINUS_EXPR, op1_utype, uprecm1,
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146 fold_convert (op1_utype, unshare_expr (op1)));
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147 tt = fold_convert_loc (loc, unsigned_type_for (type0), op0);
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148 tt = fold_build2 (RSHIFT_EXPR, TREE_TYPE (tt), tt, x);
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149 tt = fold_build2 (NE_EXPR, boolean_type_node, tt,
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150 build_int_cst (TREE_TYPE (tt), 0));
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151 }
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152
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153 /* For signed x << y, in C++11 and later, the following:
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154 x < 0 || ((unsigned) x >> (uprecm1 - y))
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155 if > 1, is undefined. */
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156 else if (code == LSHIFT_EXPR && cxx_dialect >= cxx11)
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157 {
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158 tree x = fold_build2 (MINUS_EXPR, op1_utype, uprecm1,
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159 fold_convert (op1_utype, unshare_expr (op1)));
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160 tt = fold_convert_loc (loc, unsigned_type_for (type0),
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161 unshare_expr (op0));
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162 tt = fold_build2 (RSHIFT_EXPR, TREE_TYPE (tt), tt, x);
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163 tt = fold_build2 (GT_EXPR, boolean_type_node, tt,
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164 build_int_cst (TREE_TYPE (tt), 1));
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165 x = fold_build2 (LT_EXPR, boolean_type_node, unshare_expr (op0),
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166 build_int_cst (type0, 0));
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167 tt = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, x, tt);
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168 }
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169
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170 /* If the condition was folded to 0, no need to instrument
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171 this expression. */
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172 if (integer_zerop (t) && (tt == NULL_TREE || integer_zerop (tt)))
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173 return NULL_TREE;
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174
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175 /* In case we have a SAVE_EXPR in a conditional context, we need to
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176 make sure it gets evaluated before the condition. */
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177 t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), unshare_expr (op0), t);
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178 t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), unshare_expr (op1), t);
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179
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180 enum sanitize_code recover_kind = SANITIZE_SHIFT_EXPONENT;
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181 tree else_t = void_node;
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182 if (tt)
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183 {
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184 if (!sanitize_flags_p (SANITIZE_SHIFT_EXPONENT))
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185 {
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186 t = fold_build1 (TRUTH_NOT_EXPR, boolean_type_node, t);
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187 t = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, t, tt);
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188 recover_kind = SANITIZE_SHIFT_BASE;
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189 }
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190 else
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191 {
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192 if (flag_sanitize_undefined_trap_on_error
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193 || ((!(flag_sanitize_recover & SANITIZE_SHIFT_EXPONENT))
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194 == (!(flag_sanitize_recover & SANITIZE_SHIFT_BASE))))
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195 t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t, tt);
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196 else
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197 else_t = tt;
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198 }
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199 }
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200
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201 if (flag_sanitize_undefined_trap_on_error)
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202 tt = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
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203 else
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204 {
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205 tree data = ubsan_create_data ("__ubsan_shift_data", 1, &loc,
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206 ubsan_type_descriptor (type0),
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207 ubsan_type_descriptor (type1), NULL_TREE,
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208 NULL_TREE);
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209 data = build_fold_addr_expr_loc (loc, data);
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210
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211 enum built_in_function bcode
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212 = (flag_sanitize_recover & recover_kind)
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213 ? BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS
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214 : BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS_ABORT;
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215 tt = builtin_decl_explicit (bcode);
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216 op0 = unshare_expr (op0);
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217 op1 = unshare_expr (op1);
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218 tt = build_call_expr_loc (loc, tt, 3, data, ubsan_encode_value (op0),
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219 ubsan_encode_value (op1));
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220 if (else_t != void_node)
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221 {
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222 bcode = (flag_sanitize_recover & SANITIZE_SHIFT_BASE)
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223 ? BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS
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224 : BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS_ABORT;
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225 tree else_tt = builtin_decl_explicit (bcode);
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226 op0 = unshare_expr (op0);
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227 op1 = unshare_expr (op1);
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228 else_tt = build_call_expr_loc (loc, else_tt, 3, data,
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229 ubsan_encode_value (op0),
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230 ubsan_encode_value (op1));
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231 else_t = fold_build3 (COND_EXPR, void_type_node, else_t,
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232 else_tt, void_node);
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233 }
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234 }
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235 t = fold_build3 (COND_EXPR, void_type_node, t, tt, else_t);
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236
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237 return t;
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238 }
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239
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240 /* Instrument variable length array bound. */
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241
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242 tree
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243 ubsan_instrument_vla (location_t loc, tree size)
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244 {
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245 tree type = TREE_TYPE (size);
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246 tree t, tt;
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247
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248 t = fold_build2 (LE_EXPR, boolean_type_node, size, build_int_cst (type, 0));
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249 if (flag_sanitize_undefined_trap_on_error)
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250 tt = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
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251 else
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252 {
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253 tree data = ubsan_create_data ("__ubsan_vla_data", 1, &loc,
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254 ubsan_type_descriptor (type), NULL_TREE,
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255 NULL_TREE);
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256 data = build_fold_addr_expr_loc (loc, data);
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257 enum built_in_function bcode
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258 = (flag_sanitize_recover & SANITIZE_VLA)
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259 ? BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE
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260 : BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE_ABORT;
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261 tt = builtin_decl_explicit (bcode);
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262 tt = build_call_expr_loc (loc, tt, 2, data, ubsan_encode_value (size));
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263 }
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264 t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_node);
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265
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266 return t;
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267 }
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268
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269 /* Instrument missing return in C++ functions returning non-void. */
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270
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271 tree
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272 ubsan_instrument_return (location_t loc)
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273 {
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274 if (flag_sanitize_undefined_trap_on_error)
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275 return build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
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276
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277 tree data = ubsan_create_data ("__ubsan_missing_return_data", 1, &loc,
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278 NULL_TREE, NULL_TREE);
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279 tree t = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_MISSING_RETURN);
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280 return build_call_expr_loc (loc, t, 1, build_fold_addr_expr_loc (loc, data));
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281 }
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282
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283 /* Instrument array bounds for ARRAY_REFs. We create special builtin,
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284 that gets expanded in the sanopt pass, and make an array dimension
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285 of it. ARRAY is the array, *INDEX is an index to the array.
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286 Return NULL_TREE if no instrumentation is emitted.
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287 IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside a ADDR_EXPR. */
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288
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289 tree
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290 ubsan_instrument_bounds (location_t loc, tree array, tree *index,
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291 bool ignore_off_by_one)
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292 {
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293 tree type = TREE_TYPE (array);
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294 tree domain = TYPE_DOMAIN (type);
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295
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296 if (domain == NULL_TREE || TYPE_MAX_VALUE (domain) == NULL_TREE)
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297 return NULL_TREE;
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298
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299 tree bound = TYPE_MAX_VALUE (domain);
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300 if (ignore_off_by_one)
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301 bound = fold_build2 (PLUS_EXPR, TREE_TYPE (bound), bound,
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302 build_int_cst (TREE_TYPE (bound), 1));
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303
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304 /* Detect flexible array members and suchlike, unless
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305 -fsanitize=bounds-strict. */
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306 tree base = get_base_address (array);
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307 if (!sanitize_flags_p (SANITIZE_BOUNDS_STRICT)
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308 && TREE_CODE (array) == COMPONENT_REF
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309 && base && (INDIRECT_REF_P (base) || TREE_CODE (base) == MEM_REF))
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310 {
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311 tree next = NULL_TREE;
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312 tree cref = array;
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313
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314 /* Walk all structs/unions. */
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315 while (TREE_CODE (cref) == COMPONENT_REF)
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316 {
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317 if (TREE_CODE (TREE_TYPE (TREE_OPERAND (cref, 0))) == RECORD_TYPE)
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318 for (next = DECL_CHAIN (TREE_OPERAND (cref, 1));
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319 next && TREE_CODE (next) != FIELD_DECL;
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320 next = DECL_CHAIN (next))
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321 ;
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322 if (next)
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323 /* Not a last element. Instrument it. */
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324 break;
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325 /* Ok, this is the last field of the structure/union. But the
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326 aggregate containing the field must be the last field too,
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327 recursively. */
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328 cref = TREE_OPERAND (cref, 0);
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329 }
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330 if (!next)
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331 /* Don't instrument this flexible array member-like array in non-strict
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332 -fsanitize=bounds mode. */
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333 return NULL_TREE;
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334 }
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335
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336 /* Don't emit instrumentation in the most common cases. */
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337 tree idx = NULL_TREE;
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338 if (TREE_CODE (*index) == INTEGER_CST)
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339 idx = *index;
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340 else if (TREE_CODE (*index) == BIT_AND_EXPR
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341 && TREE_CODE (TREE_OPERAND (*index, 1)) == INTEGER_CST)
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342 idx = TREE_OPERAND (*index, 1);
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343 if (idx
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344 && TREE_CODE (bound) == INTEGER_CST
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345 && tree_int_cst_sgn (idx) >= 0
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346 && tree_int_cst_le (idx, bound))
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347 return NULL_TREE;
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348
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349 *index = save_expr (*index);
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350 /* Create a "(T *) 0" tree node to describe the array type. */
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351 tree zero_with_type = build_int_cst (build_pointer_type (type), 0);
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352 return build_call_expr_internal_loc (loc, IFN_UBSAN_BOUNDS,
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353 void_type_node, 3, zero_with_type,
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354 *index, bound);
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355 }
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356
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357 /* Return true iff T is an array that was instrumented by SANITIZE_BOUNDS. */
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358
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359 bool
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360 ubsan_array_ref_instrumented_p (const_tree t)
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361 {
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362 if (TREE_CODE (t) != ARRAY_REF)
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363 return false;
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364
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365 tree op1 = TREE_OPERAND (t, 1);
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366 return TREE_CODE (op1) == COMPOUND_EXPR
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367 && TREE_CODE (TREE_OPERAND (op1, 0)) == CALL_EXPR
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368 && CALL_EXPR_FN (TREE_OPERAND (op1, 0)) == NULL_TREE
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369 && CALL_EXPR_IFN (TREE_OPERAND (op1, 0)) == IFN_UBSAN_BOUNDS;
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370 }
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371
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372 /* Instrument an ARRAY_REF, if it hasn't already been instrumented.
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373 IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside a ADDR_EXPR. */
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374
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375 void
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376 ubsan_maybe_instrument_array_ref (tree *expr_p, bool ignore_off_by_one)
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377 {
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378 if (!ubsan_array_ref_instrumented_p (*expr_p)
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379 && sanitize_flags_p (SANITIZE_BOUNDS | SANITIZE_BOUNDS_STRICT)
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380 && current_function_decl != NULL_TREE)
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381 {
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382 tree op0 = TREE_OPERAND (*expr_p, 0);
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383 tree op1 = TREE_OPERAND (*expr_p, 1);
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384 tree e = ubsan_instrument_bounds (EXPR_LOCATION (*expr_p), op0, &op1,
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385 ignore_off_by_one);
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386 if (e != NULL_TREE)
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387 {
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388 tree t = copy_node (*expr_p);
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389 TREE_OPERAND (t, 1) = build2 (COMPOUND_EXPR, TREE_TYPE (op1),
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390 e, op1);
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391 *expr_p = t;
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392 }
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393 }
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394 }
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395
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396 static tree
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397 ubsan_maybe_instrument_reference_or_call (location_t loc, tree op, tree ptype,
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398 enum ubsan_null_ckind ckind)
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399 {
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400 if (!sanitize_flags_p (SANITIZE_ALIGNMENT | SANITIZE_NULL)
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401 || current_function_decl == NULL_TREE)
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402 return NULL_TREE;
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403
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404 tree type = TREE_TYPE (ptype);
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405 tree orig_op = op;
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406 bool instrument = false;
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407 unsigned int mina = 0;
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408
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409 if (sanitize_flags_p (SANITIZE_ALIGNMENT))
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410 {
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411 mina = min_align_of_type (type);
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412 if (mina <= 1)
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413 mina = 0;
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414 }
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415 while ((TREE_CODE (op) == NOP_EXPR
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416 || TREE_CODE (op) == NON_LVALUE_EXPR)
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417 && TREE_CODE (TREE_TYPE (op)) == POINTER_TYPE)
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418 op = TREE_OPERAND (op, 0);
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419 if (TREE_CODE (op) == NOP_EXPR
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420 && TREE_CODE (TREE_TYPE (op)) == REFERENCE_TYPE)
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421 {
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422 if (mina && mina > min_align_of_type (TREE_TYPE (TREE_TYPE (op))))
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423 instrument = true;
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424 }
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425 else
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426 {
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427 if (sanitize_flags_p (SANITIZE_NULL) && TREE_CODE (op) == ADDR_EXPR)
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428 {
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429 bool strict_overflow_p = false;
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430 /* tree_single_nonzero_warnv_p will not return true for non-weak
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431 non-automatic decls with -fno-delete-null-pointer-checks,
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432 which is disabled during -fsanitize=null. We don't want to
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433 instrument those, just weak vars though. */
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434 int save_flag_delete_null_pointer_checks
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435 = flag_delete_null_pointer_checks;
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436 flag_delete_null_pointer_checks = 1;
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437 if (!tree_single_nonzero_warnv_p (op, &strict_overflow_p)
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438 || strict_overflow_p)
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439 instrument = true;
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|
|
440 flag_delete_null_pointer_checks
|
|
|
441 = save_flag_delete_null_pointer_checks;
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|
|
442 }
|
|
|
443 else if (sanitize_flags_p (SANITIZE_NULL))
|
|
|
444 instrument = true;
|
|
|
445 if (mina && mina > 1)
|
|
|
446 {
|
|
|
447 if (!POINTER_TYPE_P (TREE_TYPE (op))
|
|
|
448 || mina > get_pointer_alignment (op) / BITS_PER_UNIT)
|
|
|
449 instrument = true;
|
|
|
450 }
|
|
|
451 }
|
|
|
452 if (!instrument)
|
|
|
453 return NULL_TREE;
|
|
|
454 op = save_expr (orig_op);
|
|
|
455 gcc_assert (POINTER_TYPE_P (ptype));
|
|
|
456 if (TREE_CODE (ptype) == REFERENCE_TYPE)
|
|
|
457 ptype = build_pointer_type (TREE_TYPE (ptype));
|
|
|
458 tree kind = build_int_cst (ptype, ckind);
|
|
|
459 tree align = build_int_cst (pointer_sized_int_node, mina);
|
|
|
460 tree call
|
|
|
461 = build_call_expr_internal_loc (loc, IFN_UBSAN_NULL, void_type_node,
|
|
|
462 3, op, kind, align);
|
|
|
463 TREE_SIDE_EFFECTS (call) = 1;
|
|
|
464 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op);
|
|
|
465 }
|
|
|
466
|
|
|
467 /* Instrument a NOP_EXPR to REFERENCE_TYPE or INTEGER_CST with REFERENCE_TYPE
|
|
|
468 type if needed. */
|
|
|
469
|
|
|
470 void
|
|
|
471 ubsan_maybe_instrument_reference (tree *stmt_p)
|
|
|
472 {
|
|
|
473 tree stmt = *stmt_p;
|
|
|
474 tree op = stmt;
|
|
|
475 if (TREE_CODE (stmt) == NOP_EXPR)
|
|
|
476 op = TREE_OPERAND (stmt, 0);
|
|
|
477 op = ubsan_maybe_instrument_reference_or_call (EXPR_LOCATION (stmt), op,
|
|
|
478 TREE_TYPE (stmt),
|
|
|
479 UBSAN_REF_BINDING);
|
|
|
480 if (op)
|
|
|
481 {
|
|
|
482 if (TREE_CODE (stmt) == NOP_EXPR)
|
|
|
483 TREE_OPERAND (stmt, 0) = op;
|
|
|
484 else
|
|
|
485 *stmt_p = op;
|
|
|
486 }
|
|
|
487 }
|
|
|
488
|
|
|
489 /* Instrument a CALL_EXPR to a method if needed. */
|
|
|
490
|
|
|
491 void
|
|
|
492 ubsan_maybe_instrument_member_call (tree stmt, bool is_ctor)
|
|
|
493 {
|
|
|
494 if (call_expr_nargs (stmt) == 0)
|
|
|
495 return;
|
|
|
496 tree op = CALL_EXPR_ARG (stmt, 0);
|
|
|
497 if (op == error_mark_node
|
|
|
498 || !POINTER_TYPE_P (TREE_TYPE (op)))
|
|
|
499 return;
|
|
|
500 op = ubsan_maybe_instrument_reference_or_call (EXPR_LOCATION (stmt), op,
|
|
|
501 TREE_TYPE (op),
|
|
|
502 is_ctor ? UBSAN_CTOR_CALL
|
|
|
503 : UBSAN_MEMBER_CALL);
|
|
|
504 if (op)
|
|
|
505 CALL_EXPR_ARG (stmt, 0) = op;
|
|
|
506 }
|
