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         if (does_inc_dec(one) || does_inc_dec(two))
  36                 return 0;
  37         return expr_equiv(one, two);
  38 }
  39
  40 static int inconsistent_check(struct expression *left, struct expression *right)
  41 {
  42         sval_t sval;
  43
  44         if (get_value(left->left, &sval)) {
  45                 if (get_value(right->left, &sval))
  46                         return expr_equiv_no_inc_dec(left->right, right->right);
  47                 if (get_value(right->right, &sval))
  48                         return expr_equiv_no_inc_dec(left->right, right->left);
  49                 return 0;
  50         }
  51         if (get_value(left->right, &sval)) {
  52                 if (get_value(right->left, &sval))
  53                         return expr_equiv_no_inc_dec(left->left, right->right);
  54                 if (get_value(right->right, &sval))
  55                         return expr_equiv_no_inc_dec(left->left, right->left);
  56                 return 0;
  57         }
  58
  59         return 0;
  60 }
  61
  62 static void check_or(struct expression *expr)
  63 {
  64         struct expression *left, *right;
  65
  66         left = strip_expr(expr->left);
  67         right = strip_expr(expr->right);
  68
  69         if (left->type != EXPR_COMPARE || left->op != SPECIAL_NOTEQUAL)
  70                 return;
  71         if (right->type != EXPR_COMPARE || right->op != SPECIAL_NOTEQUAL)
  72                 return;
  73         if (!inconsistent_check(left, right))
  74                 return;
  75
  76         sm_warning("was && intended here instead of ||?");
  77 }
  78
  79 static int is_kernel_min_macro(struct expression *expr)
  80 {
  81         char *macro;
  82
  83         if (option_project != PROJ_KERNEL)
  84                 return 0;
  85         macro = get_macro_name(expr->pos);
  86         if (!macro)
  87                 return 0;
  88         if (strcmp(macro, "min") == 0 ||
  89             strcmp(macro, "min_t") == 0 ||
  90             strcmp(macro, "max") == 0 ||
  91             strcmp(macro, "max_t") == 0)
  92                 return 1;
  93         return 0;
  94 }
  95
  96 static void check_and(struct expression *expr)
  97 {
  98         struct expression *left, *right;
  99
 100         if (is_kernel_min_macro(expr))
 101                 return;
 102
 103         left = strip_expr(expr->left);
 104         right = strip_expr(expr->right);
 105
 106         if (left->type != EXPR_COMPARE || left->op != SPECIAL_EQUAL)
 107                 return;
 108         if (right->type != EXPR_COMPARE || right->op != SPECIAL_EQUAL)
 109                 return;
 110         if (!inconsistent_check(left, right))
 111                 return;
 112
 113         sm_warning("was || intended here instead of &&?");
 114 }
 115
 116 static void match_logic(struct expression *expr)
 117 {
 118         if (expr->type != EXPR_LOGICAL)
 119                 return;
 120
 121         if (expr->op == SPECIAL_LOGICAL_OR)
 122                 check_or(expr);
 123         if (expr->op == SPECIAL_LOGICAL_AND)
 124                 check_and(expr);
 125 }
 126
 127 static void match_condition(struct expression *expr)
 128 {
 129         sval_t sval;
 130
 131         if (expr->type != EXPR_BINOP)
 132                 return;
 133         if (expr->op == '|') {
 134                 if (get_value(expr->left, &sval) || get_value(expr->right, &sval))
 135                         sm_warning("suspicious bitop condition");
 136                 return;
 137         }
 138
 139         if (expr->op != '&')
 140                 return;
 141
 142         if (get_macro_name(expr->pos))
 143                 return;
 144         if (is_unconstant_macro(expr->left) || is_unconstant_macro(expr->right))
 145                 return;
 146
 147         if ((get_value(expr->left, &sval) && sval.value == 0) ||
 148             (get_value(expr->right, &sval) && sval.value == 0))
 149                 sm_warning("bitwise AND condition is false here");
 150 }
 151
 152 static void match_binop(struct expression *expr)
 153 {
 154         sval_t left, right, sval;
 155
 156         if (expr->op != '&')
 157                 return;
 158         if (!get_value(expr, &sval) || sval.value != 0)
 159                 return;
 160         if (get_macro_name(expr->pos))
 161                 return;
 162         if (!get_value(expr->left, &left) || !get_value(expr->right, &right))
 163                 return;
 164         sm_warning("odd binop '0x%llx & 0x%llx'", left.uvalue, right.uvalue);
 165 }
 166
 167 void check_or_vs_and(int id)
 168 {
 169         my_id = id;
 170
 171         add_hook(&match_logic, LOGIC_HOOK);
 172         add_hook(&match_condition, CONDITION_HOOK);
 173         if (option_spammy)
 174                 add_hook(&match_binop, BINOP_HOOK);
 175 }