check_or_vs_and.c

   1 /*
   2  * Copyright (C) 2012 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "smatch.h"
  19 #include "smatch_function_hashtable.h"
  20
  21 static int my_id;
  22
  23 static int does_inc_dec(struct expression *expr)
  24 {
  25         if (expr->type == EXPR_PREOP || expr->type == EXPR_POSTOP) {
  26                 if (expr->op == SPECIAL_INCREMENT || expr->op == SPECIAL_DECREMENT)
  27                         return 1;
  28                 return does_inc_dec(expr->unop);
  29         }
  30         return 0;
  31 }
  32
  33 static int expr_equiv_no_inc_dec(struct expression *one, struct expression *two)
  34 {
  35         sval_t dummy;
  36
  37         if (does_inc_dec(one) || does_inc_dec(two))
  38                 return 0;
  39         if (get_value(one, &dummy) &&
  40             get_value(two, &dummy))
  41                 return 0;
  42
  43         return expr_equiv(one, two);
  44 }
  45
  46 static int inconsistent_check(struct expression *left, struct expression *right)
  47 {
  48         sval_t sval;
  49
  50         if (get_value(left->left, &sval)) {
  51                 if (get_value(right->left, &sval))
  52                         return expr_equiv_no_inc_dec(left->right, right->right);
  53                 if (get_value(right->right, &sval))
  54                         return expr_equiv_no_inc_dec(left->right, right->left);
  55                 return 0;
  56         }
  57         if (get_value(left->right, &sval)) {
  58                 if (get_value(right->left, &sval))
  59                         return expr_equiv_no_inc_dec(left->left, right->right);
  60                 if (get_value(right->right, &sval))
  61                         return expr_equiv_no_inc_dec(left->left, right->left);
  62                 return 0;
  63         }
  64
  65         return 0;
  66 }
  67
  68 static void check_or(struct expression *expr)
  69 {
  70         struct expression *left, *right;
  71
  72         left = strip_expr(expr->left);
  73         right = strip_expr(expr->right);
  74
  75         if (left->type != EXPR_COMPARE || left->op != SPECIAL_NOTEQUAL)
  76                 return;
  77         if (right->type != EXPR_COMPARE || right->op != SPECIAL_NOTEQUAL)
  78                 return;
  79         if (!inconsistent_check(left, right))
  80                 return;
  81
  82         sm_warning("was && intended here instead of ||?");
  83 }
  84
  85 static int is_kernel_min_macro(struct expression *expr)
  86 {
  87         char *macro;
  88
  89         if (option_project != PROJ_KERNEL)
  90                 return 0;
  91         macro = get_macro_name(expr->pos);
  92         if (!macro)
  93                 return 0;
  94         if (strcmp(macro, "min") == 0 ||
  95             strcmp(macro, "min_t") == 0 ||
  96             strcmp(macro, "max") == 0 ||
  97             strcmp(macro, "max_t") == 0)
  98                 return 1;
  99         return 0;
 100 }
 101
 102 static void check_and(struct expression *expr)
 103 {
 104         struct expression *left, *right;
 105
 106         if (is_kernel_min_macro(expr))
 107                 return;
 108
 109         left = strip_expr(expr->left);
 110         right = strip_expr(expr->right);
 111
 112         if (left->type != EXPR_COMPARE || left->op != SPECIAL_EQUAL)
 113                 return;
 114         if (right->type != EXPR_COMPARE || right->op != SPECIAL_EQUAL)
 115                 return;
 116         if (!inconsistent_check(left, right))
 117                 return;
 118
 119         sm_warning("was || intended here instead of &&?");
 120 }
 121
 122 static void match_logic(struct expression *expr)
 123 {
 124         if (expr->type != EXPR_LOGICAL)
 125                 return;
 126
 127         if (expr->op == SPECIAL_LOGICAL_OR)
 128                 check_or(expr);
 129         if (expr->op == SPECIAL_LOGICAL_AND)
 130                 check_and(expr);
 131 }
 132
 133 static void match_condition(struct expression *expr)
 134 {
 135         sval_t sval;
 136
 137         if (expr->type != EXPR_BINOP)
 138                 return;
 139         if (expr->op == '|') {
 140                 if (get_value(expr->left, &sval) || get_value(expr->right, &sval))
 141                         sm_warning("suspicious bitop condition");
 142                 return;
 143         }
 144
 145         if (expr->op != '&')
 146                 return;
 147
 148         if (get_macro_name(expr->pos))
 149                 return;
 150         if (is_unconstant_macro(expr->left) || is_unconstant_macro(expr->right))
 151                 return;
 152
 153         if ((get_value(expr->left, &sval) && sval.value == 0) ||
 154             (get_value(expr->right, &sval) && sval.value == 0))
 155                 sm_warning("bitwise AND condition is false here");
 156 }
 157
 158 static void match_binop(struct expression *expr)
 159 {
 160         sval_t left, right, sval;
 161
 162         if (expr->op != '&')
 163                 return;
 164         if (!get_value(expr, &sval) || sval.value != 0)
 165                 return;
 166         if (get_macro_name(expr->pos))
 167                 return;
 168         if (!get_value(expr->left, &left) || !get_value(expr->right, &right))
 169                 return;
 170         sm_warning("odd binop '0x%llx & 0x%llx'", left.uvalue, right.uvalue);
 171 }
 172
 173 void check_or_vs_and(int id)
 174 {
 175         my_id = id;
 176
 177         add_hook(&match_logic, LOGIC_HOOK);
 178         add_hook(&match_condition, CONDITION_HOOK);
 179         if (option_spammy)
 180                 add_hook(&match_binop, BINOP_HOOK);
 181 }