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 (expr->type == EXPR_PREOP && expr->op == '&')
 104                 return;
 105
 106         if (get_param_num(expr) < 0)
 107                 return;
 108
 109         if (is_ignored_param(expr))
 110                 return;
 111
 112         if (param_was_set(expr))
 113                 return;
 114
 115         /*
 116          * At this point we really only care about potential NULL dereferences.
 117          * Potentially in the future we will care about everything.
 118          */
 119         if (implied_not_equal(expr, 0))
 120                 return;
 121
 122         set_state_expr(my_id, expr, &derefed);
 123 }
 124
 125 static void match_dereference(struct expression *expr)
 126 {
 127         if (expr->type != EXPR_PREOP)
 128                 return;
 129         check_deref(expr->unop);
 130 }
 131
 132 static void find_inner_dereferences(struct expression *expr)
 133 {
 134         while (expr->type == EXPR_PREOP) {
 135                 if (expr->op == '*')
 136                         check_deref(expr->unop);
 137                 expr = strip_expr(expr->unop);
 138         }
 139 }
 140
 141 static void set_param_dereferenced(struct expression *call, struct expression *arg, char *key, char *unused)
 142 {
 143         struct symbol *sym;
 144         char *name;
 145
 146         check_deref(arg);
 147
 148         name = get_variable_from_key(arg, key, &sym);
 149         if (!name || !sym)
 150                 goto free;
 151         if (name[0] == '&')
 152                 goto free;
 153         if (is_ignored_param(symbol_expression(sym)))
 154                 goto free;
 155         if (get_param_num_from_sym(sym) < 0)
 156                 goto free;
 157         if (param_was_set_var_sym(name, sym))
 158                 goto free;
 159
 160         set_state(my_id, name, sym, &derefed);
 161         find_inner_dereferences(arg);
 162 free:
 163         free_string(name);
 164 }
 165
 166 static void process_states(void)
 167 {
 168         struct sm_state *tmp;
 169         int arg;
 170         const char *name;
 171
 172         FOR_EACH_MY_SM(my_id, __get_cur_stree(), tmp) {
 173                 if (tmp->state != &derefed)
 174                         continue;
 175                 arg = get_param_num_from_sym(tmp->sym);
 176                 if (arg < 0)
 177                         continue;
 178                 name = get_param_name(tmp);
 179                 if (!name || name[0] == '&')
 180                         continue;
 181                 sql_insert_return_implies(DEREFERENCE, arg, name, "1");
 182         } END_FOR_EACH_SM(tmp);
 183 }
 184
 185 static void match_pointer_as_array(struct expression *expr)
 186 {
 187         if (!is_array(expr))
 188                 return;
 189         check_deref(get_array_base(expr));
 190 }
 191
 192 void check_dereferences_param(int id)
 193 {
 194         my_id = id;
 195
 196         add_hook(&match_function_def, FUNC_DEF_HOOK);
 197
 198         add_hook(&match_dereference, DEREF_HOOK);
 199         add_hook(&match_pointer_as_array, OP_HOOK);
 200         select_return_implies_hook(DEREFERENCE, &set_param_dereferenced);
 201         add_modification_hook(my_id, &set_ignore);
 202         add_pre_merge_hook(my_id, &pre_merge_hook);
 203
 204         all_return_states_hook(&process_states);
 205 }