check_dereferences_param.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 /*
  19  * This is an --info recipe.  The goal is to print a message for every parameter
  20  * which we can not avoid dereferencing.  This is maybe a bit restrictive but it
  21  * avoids some false positives.
  22  */
  23
  24 #include "smatch.h"
  25 #include "smatch_extra.h"
  26 #include "smatch_slist.h"
  27
  28 static int my_id;
  29
  30 STATE(derefed);
  31 STATE(ignore);
  32 STATE(param);
  33
  34 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
  35 {
  36         if (cur->state == &derefed || other->state != &derefed)
  37                 return;
  38         if (is_impossible_path())
  39                 set_state(my_id, cur->name, cur->sym, &derefed);
  40 }
  41
  42 static void set_ignore(struct sm_state *sm, struct expression *mod_expr)
  43 {
  44         if (sm->state == &derefed)
  45                 return;
  46         set_state(my_id, sm->name, sm->sym, &ignore);
  47 }
  48
  49 static void match_function_def(struct symbol *sym)
  50 {
  51         struct symbol *arg;
  52         int i;
  53
  54         i = -1;
  55         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
  56                 i++;
  57                 if (!arg->ident)
  58                         continue;
  59                 set_state(my_id, arg->ident->name, arg, &param);
  60         } END_FOR_EACH_PTR(arg);
  61 }
  62
  63 static int is_ignored_param(struct expression *expr)
  64 {
  65         struct sm_state *sm;
  66
  67         if (param_was_set(expr))
  68                 return 1;
  69
  70         sm = get_sm_state_expr(my_id, expr);
  71         if (sm && slist_has_state(sm->possible, &ignore))
  72                 return 1;
  73         return 0;
  74 }
  75
  76 static void check_deref(struct expression *expr)
  77 {
  78         struct expression *tmp;
  79
  80         if (is_impossible_path())
  81                 return;
  82
  83         tmp = get_assigned_expr(expr);
  84         if (tmp)
  85                 expr = tmp;
  86
  87         if (expr->type == EXPR_PREOP &&
  88             expr->op == '&') {
  89                 expr = strip_expr(expr->unop);
  90                 if (expr->type != EXPR_DEREF)
  91                         return;
  92                 expr = strip_expr(expr->deref);
  93                 if (expr->type != EXPR_PREOP ||
  94                     expr->op != '*')
  95                         return;
  96                 expr = strip_expr(expr->unop);
  97         }
  98
  99         expr = strip_expr(expr);
 100         if (!expr)
 101                 return;
 102
 103         if (get_param_num(expr) < 0)
 104                 return;
 105
 106         if (is_ignored_param(expr))
 107                 return;
 108
 109         if (param_was_set(expr))
 110                 return;
 111
 112         /*
 113          * At this point we really only care about potential NULL dereferences.
 114          * Potentially in the future we will care about everything.
 115          */
 116         if (implied_not_equal(expr, 0))
 117                 return;
 118
 119         set_state_expr(my_id, expr, &derefed);
 120 }
 121
 122 static void match_dereference(struct expression *expr)
 123 {
 124         if (expr->type != EXPR_PREOP)
 125                 return;
 126         check_deref(expr->unop);
 127 }
 128
 129 static void find_inner_dereferences(struct expression *expr)
 130 {
 131         while (expr->type == EXPR_PREOP) {
 132                 if (expr->op == '*')
 133                         check_deref(expr->unop);
 134                 expr = strip_expr(expr->unop);
 135         }
 136 }
 137
 138 static void set_param_dereferenced(struct expression *call, struct expression *arg, char *key, char *unused)
 139 {
 140         struct symbol *sym;
 141         char *name;
 142
 143         check_deref(arg);
 144
 145         name = get_variable_from_key(arg, key, &sym);
 146         if (!name || !sym)
 147                 goto free;
 148         if (is_ignored_param(symbol_expression(sym)))
 149                 goto free;
 150         if (get_param_num_from_sym(sym) < 0)
 151                 goto free;
 152         if (param_was_set_var_sym(name, sym))
 153                 goto free;
 154
 155         set_state(my_id, name, sym, &derefed);
 156         find_inner_dereferences(arg);
 157 free:
 158         free_string(name);
 159 }
 160
 161 static void process_states(void)
 162 {
 163         struct sm_state *tmp;
 164         int arg;
 165         const char *name;
 166
 167         FOR_EACH_MY_SM(my_id, __get_cur_stree(), tmp) {
 168                 if (tmp->state != &derefed)
 169                         continue;
 170                 arg = get_param_num_from_sym(tmp->sym);
 171                 if (arg < 0)
 172                         continue;
 173                 name = get_param_name(tmp);
 174                 if (!name)
 175                         continue;
 176                 sql_insert_return_implies(DEREFERENCE, arg, name, "1");
 177         } END_FOR_EACH_SM(tmp);
 178 }
 179
 180 static void match_pointer_as_array(struct expression *expr)
 181 {
 182         if (!is_array(expr))
 183                 return;
 184         check_deref(get_array_base(expr));
 185 }
 186
 187 void check_dereferences_param(int id)
 188 {
 189         my_id = id;
 190
 191         add_hook(&match_function_def, FUNC_DEF_HOOK);
 192
 193         add_hook(&match_dereference, DEREF_HOOK);
 194         add_hook(&match_pointer_as_array, OP_HOOK);
 195         select_return_implies_hook(DEREFERENCE, &set_param_dereferenced);
 196         add_modification_hook(my_id, &set_ignore);
 197         add_pre_merge_hook(my_id, &pre_merge_hook);
 198
 199         all_return_states_hook(&process_states);
 200 }