smatch_power_of_two.c

   1 /*
   2  * Copyright (C) 2021
   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_extra.h"
  20 #include "smatch_slist.h"
  21
  22 static int my_id;
  23
  24 STATE(power_of_two);
  25
  26 bool is_power_of_two(struct expression *expr)
  27 {
  28         sval_t sval;
  29
  30         expr = strip_expr(expr);
  31
  32         if (expr->type == EXPR_BINOP &&
  33             expr->op == SPECIAL_LEFTSHIFT &&
  34             is_power_of_two(expr->left))
  35                 return true;
  36
  37         if (get_implied_value(expr, &sval)) {
  38                 if (!(sval.uvalue & (sval.uvalue - 1)))
  39                         return true;
  40                 return false;
  41         }
  42
  43         if (get_state_expr(my_id, expr) == &power_of_two)
  44                 return true;
  45
  46         return false;
  47 }
  48
  49 static bool is_sign_expansion(struct expression *expr)
  50 {
  51         struct range_list *rl;
  52         struct symbol *type_left;
  53         struct symbol *type_right;
  54
  55         type_left = get_type(expr->left);
  56         type_right = get_type(expr->right);
  57         if (!type_left || !type_right)
  58                 return true;
  59         if (type_bits(type_left) <= type_bits(type_right))
  60                 return false;
  61
  62         get_absolute_rl(expr->right, &rl);
  63         if (sval_is_negative(rl_min(rl)))
  64                 return true;
  65
  66         return false;
  67 }
  68
  69 static void match_assign(struct expression *expr)
  70 {
  71         if (expr->op != '=')
  72                 return;
  73
  74         if (is_sign_expansion(expr))
  75                 return;
  76
  77         if (is_power_of_two(expr->right))
  78                 set_state_expr(my_id, expr->left, &power_of_two);
  79 }
  80
  81 static bool is_minus_mask(struct expression *left, struct expression *right)
  82 {
  83         if (right->type != EXPR_BINOP ||
  84             right->op != '-')
  85                 return false;
  86
  87         if (right->right->value != 1)
  88                 return false;
  89
  90         if (expr_equiv(left, right->left))
  91                 return true;
  92
  93         return false;
  94 }
  95
  96 static void match_condition(struct expression *expr)
  97 {
  98         expr = strip_expr(expr);
  99         if (expr->type != EXPR_BINOP ||
 100             expr->op != '&')
 101                 return;
 102
 103         if (is_minus_mask(strip_expr(expr->left), strip_expr(expr->right))) {
 104                 set_true_false_states_expr(my_id, expr->left, NULL, &power_of_two);
 105                 return;
 106         }
 107
 108         if (is_minus_mask(strip_expr(expr->right), strip_expr(expr->left))) {
 109                 set_true_false_states_expr(my_id, expr->right, NULL, &power_of_two);
 110                 return;
 111         }
 112 }
 113
 114 static void caller_info_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 115 {
 116         if (sm->state != &power_of_two)
 117                 return;
 118
 119         sql_insert_caller_info(call, POWER_OF_TWO, param, printed_name, "");
 120 }
 121
 122 static void set_power_of_two(const char *name, struct symbol *sym, char *value)
 123 {
 124         set_state(my_id, name, sym, &power_of_two);
 125 }
 126
 127 static void return_info_callback(int return_id, char *return_ranges,
 128                                  struct expression *returned_expr,
 129                                  int param,
 130                                  const char *printed_name,
 131                                  struct sm_state *sm)
 132 {
 133         struct smatch_state *estate;
 134         sval_t sval;
 135
 136         if (sm->state != &power_of_two)
 137                 return;
 138
 139         if (param != -1 && !param_was_set_var_sym(sm->name, sm->sym))
 140                 return;
 141
 142         estate = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 143         if (estate_get_single_value(estate, &sval))
 144                 return;
 145
 146         sql_insert_return_states(return_id, return_ranges, POWER_OF_TWO_SET, param, printed_name, "");
 147 }
 148
 149 static void returns_power_of_two_set(struct expression *expr, int param, char *key, char *value)
 150 {
 151         char *name;
 152         struct symbol *sym;
 153
 154         name = get_name_sym_from_param_key(expr, param, key, &sym);
 155         if (!name)
 156                 return;
 157         set_state(my_id, name, sym, &power_of_two);
 158 }
 159
 160 void register_power_of_two(int id)
 161 {
 162         my_id = id;
 163
 164         add_hook(&match_assign, ASSIGNMENT_HOOK);
 165         add_hook(&match_condition, CONDITION_HOOK);
 166         add_caller_info_callback(my_id, caller_info_callback);
 167         select_caller_name_sym(set_power_of_two, POWER_OF_TWO);
 168         add_return_info_callback(my_id, return_info_callback);
 169         select_return_states_hook(POWER_OF_TWO_SET, &returns_power_of_two_set);
 170 }