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 static struct smatch_state *unmatched_state(struct sm_state *sm)
  27 {
  28         struct smatch_state *state;
  29         sval_t sval;
  30
  31         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
  32         if (!state)
  33                 return &undefined;
  34         if (!estate_get_single_value(state, &sval))
  35                 return &undefined;
  36
  37         if (!(sval.uvalue & (sval.uvalue - 1)))
  38                 return &power_of_two;
  39         return &undefined;
  40 }
  41
  42 static bool implied_power_of_two(struct expression *expr)
  43 {
  44         sval_t sval;
  45
  46         if (!get_implied_value(expr, &sval))
  47                 return false;
  48         if (!(sval.uvalue & (sval.uvalue - 1)))
  49                 return true;
  50         return false;
  51 }
  52
  53 bool is_power_of_two(struct expression *expr)
  54 {
  55         expr = strip_expr(expr);
  56
  57         if (expr->type == EXPR_BINOP &&
  58             expr->op == SPECIAL_LEFTSHIFT &&
  59             is_power_of_two(expr->left))
  60                 return true;
  61
  62         if (implied_power_of_two(expr))
  63                 return true;
  64
  65         if (get_state_expr(my_id, expr) == &power_of_two)
  66                 return true;
  67
  68         return false;
  69 }
  70
  71 static void set_power_of_two(struct expression *expr)
  72 {
  73         struct symbol *type;
  74
  75         type = get_type(expr);
  76         if (type_bits(type) == 1)
  77                 return;
  78
  79         set_state_expr(my_id, expr->left, &power_of_two);
  80 }
  81
  82 static bool is_sign_expansion(struct expression *expr)
  83 {
  84         struct range_list *rl;
  85         struct symbol *type_left;
  86         struct symbol *type_right;
  87
  88         type_left = get_type(expr->left);
  89         type_right = get_type(expr->right);
  90         if (!type_left || !type_right)
  91                 return true;
  92         if (type_bits(type_left) <= type_bits(type_right))
  93                 return false;
  94
  95         get_absolute_rl(expr->right, &rl);
  96         if (sval_is_negative(rl_min(rl)))
  97                 return true;
  98
  99         return false;
 100 }
 101
 102 static void match_assign(struct expression *expr)
 103 {
 104         if (expr->op != '=')
 105                 return;
 106
 107         if (implied_power_of_two(expr->right)) {
 108                 if (get_state_expr(my_id, expr->left))
 109                         set_state_expr(my_id, expr->left, &power_of_two);
 110                 return;
 111         }
 112
 113         if (is_sign_expansion(expr))
 114                 return;
 115
 116         if (is_power_of_two(expr->right))
 117                 set_power_of_two(expr->left);
 118 }
 119
 120 static bool is_minus_mask(struct expression *left, struct expression *right)
 121 {
 122         if (right->type != EXPR_BINOP ||
 123             right->op != '-')
 124                 return false;
 125
 126         if (right->right->value != 1)
 127                 return false;
 128
 129         if (expr_equiv(left, right->left))
 130                 return true;
 131
 132         return false;
 133 }
 134
 135 static void match_condition(struct expression *expr)
 136 {
 137         expr = strip_expr(expr);
 138         if (expr->type != EXPR_BINOP ||
 139             expr->op != '&')
 140                 return;
 141
 142         if (is_minus_mask(strip_expr(expr->left), strip_expr(expr->right))) {
 143                 set_true_false_states_expr(my_id, expr->left, NULL, &power_of_two);
 144                 return;
 145         }
 146
 147         if (is_minus_mask(strip_expr(expr->right), strip_expr(expr->left))) {
 148                 set_true_false_states_expr(my_id, expr->right, NULL, &power_of_two);
 149                 return;
 150         }
 151 }
 152
 153 static void caller_info_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 154 {
 155         if (sm->state != &power_of_two)
 156                 return;
 157
 158         sql_insert_caller_info(call, POWER_OF_TWO, param, printed_name, "");
 159 }
 160
 161 static void set_power_of_two_name_sym(const char *name, struct symbol *sym, char *value)
 162 {
 163         set_state(my_id, name, sym, &power_of_two);
 164 }
 165
 166 static void return_info_callback(int return_id, char *return_ranges,
 167                                  struct expression *returned_expr,
 168                                  int param,
 169                                  const char *printed_name,
 170                                  struct sm_state *sm)
 171 {
 172         struct smatch_state *estate;
 173         sval_t sval;
 174
 175         if (sm->state != &power_of_two)
 176                 return;
 177
 178         if (param != -1 && !param_was_set_var_sym(sm->name, sm->sym))
 179                 return;
 180
 181         estate = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 182         if (estate_get_single_value(estate, &sval))
 183                 return;
 184
 185         sql_insert_return_states(return_id, return_ranges, POWER_OF_TWO_SET, param, printed_name, "");
 186 }
 187
 188 static void returns_power_of_two_set(struct expression *expr, int param, char *key, char *value)
 189 {
 190         char *name;
 191         struct symbol *sym;
 192
 193         name = get_name_sym_from_param_key(expr, param, key, &sym);
 194         if (!name)
 195                 return;
 196         set_state(my_id, name, sym, &power_of_two);
 197 }
 198
 199 void register_power_of_two(int id)
 200 {
 201         my_id = id;
 202
 203         add_hook(&match_assign, ASSIGNMENT_HOOK);
 204         add_hook(&match_condition, CONDITION_HOOK);
 205         add_unmatched_state_hook(my_id, &unmatched_state);
 206         add_caller_info_callback(my_id, caller_info_callback);
 207         select_caller_name_sym(set_power_of_two_name_sym, POWER_OF_TWO);
 208         add_return_info_callback(my_id, return_info_callback);
 209         select_return_states_hook(POWER_OF_TWO_SET, &returns_power_of_two_set);
 210 }