smatch_param_filter.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 for functions like:
  20  *
  21  * void foo(int *x)
  22  * {
  23  *      if (*x == 42)
  24  *              *x = 0;
  25  * }
  26  *
  27  * The final value of *x depends on the input to the function but with *x == 42
  28  * filtered out.
  29  *
  30  */
  31
  32 #include "smatch.h"
  33 #include "smatch_extra.h"
  34 #include "smatch_slist.h"
  35
  36 static int my_id;
  37
  38 static struct stree *start_states;
  39 static void save_start_states(struct statement *stmt)
  40 {
  41         start_states = get_all_states_stree(SMATCH_EXTRA);
  42 }
  43
  44 static void free_start_states(void)
  45 {
  46         free_stree(&start_states);
  47 }
  48
  49 static struct smatch_state *unmatched_state(struct sm_state *sm)
  50 {
  51         struct smatch_state *state;
  52
  53         if (parent_is_gone_var_sym(sm->name, sm->sym))
  54                 return alloc_estate_empty();
  55
  56         state = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
  57         if (state)
  58                 return state;
  59         return alloc_estate_whole(estate_type(sm->state));
  60 }
  61
  62 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
  63 {
  64         struct smatch_state *extra;
  65         struct range_list *rl;
  66
  67         if (estate_rl(other->state))
  68                 return;
  69
  70         extra = get_state(SMATCH_EXTRA, cur->name, cur->sym);
  71         if (!extra)
  72                 return;
  73
  74         rl = rl_intersection(estate_rl(extra), estate_rl(cur->state));
  75         if (rl_equiv(rl, estate_rl(cur->state)))
  76                 return;
  77         set_state(my_id, cur->name, cur->sym, alloc_estate_rl(clone_rl(rl)));
  78 }
  79
  80 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
  81 {
  82         int param;
  83
  84         if (__in_fake_assign)
  85                 return;
  86
  87         param = get_param_num_from_sym(sym);
  88         if (param < 0)
  89                 return;
  90
  91         /* on stack parameters are handled in smatch_param_limit.c */
  92         if (sym->ident && strcmp(sym->ident->name, name) == 0)
  93                 return;
  94
  95         set_state(my_id, name, sym, alloc_estate_empty());
  96 }
  97
  98 /*
  99  * This relies on the fact that these states are stored so that
 100  * foo->bar is before foo->bar->baz.
 101  */
 102 static int parent_set(struct string_list *list, const char *name)
 103 {
 104         char *tmp;
 105         int len;
 106         int ret;
 107
 108         FOR_EACH_PTR(list, tmp) {
 109                 len = strlen(tmp);
 110                 ret = strncmp(tmp, name, len);
 111                 if (ret < 0)
 112                         continue;
 113                 if (ret > 0)
 114                         return 0;
 115                 if (name[len] == '-')
 116                         return 1;
 117         } END_FOR_EACH_PTR(tmp);
 118
 119         return 0;
 120 }
 121
 122 static void print_one_mod_param(int return_id, char *return_ranges,
 123                         int param, struct sm_state *sm, struct string_list **totally_filtered)
 124 {
 125         const char *param_name;
 126
 127         param_name = get_param_name(sm);
 128         if (!param_name)
 129                 return;
 130         if (is_whole_rl(estate_rl(sm->state)))
 131                 return;
 132         if (!estate_rl(sm->state)) {
 133                 insert_string(totally_filtered, (char *)sm->name);
 134                 return;
 135         }
 136
 137         if (is_ignored_kernel_data(param_name)) {
 138                 insert_string(totally_filtered, (char *)sm->name);
 139                 return;
 140         }
 141
 142         sql_insert_return_states(return_id, return_ranges, PARAM_FILTER, param,
 143                         param_name, show_rl(estate_rl(sm->state)));
 144 }
 145
 146 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 147 {
 148         struct sm_state *tmp;
 149         struct sm_state *sm;
 150         struct string_list *totally_filtered = NULL;
 151         int param;
 152
 153         FOR_EACH_MY_SM(SMATCH_EXTRA, __get_cur_stree(), tmp) {
 154                 param = get_param_num_from_sym(tmp->sym);
 155                 if (param < 0)
 156                         continue;
 157
 158                 /* on stack parameters are handled in smatch_param_limit.c */
 159                 if (tmp->sym->ident && strcmp(tmp->sym->ident->name, tmp->name) == 0)
 160                         continue;
 161
 162                 if (parent_set(totally_filtered, tmp->name))
 163                         continue;
 164
 165                 sm = get_sm_state(my_id, tmp->name, tmp->sym);
 166                 if (sm)
 167                         print_one_mod_param(return_id, return_ranges, param, sm, &totally_filtered);
 168         } END_FOR_EACH_SM(tmp);
 169
 170         free_ptr_list((struct ptr_list **)&totally_filtered);
 171 }
 172
 173 int param_has_filter_data(struct sm_state *sm)
 174 {
 175         struct smatch_state *state;
 176
 177         state = get_state(my_id, sm->name, sm->sym);
 178         if (!state) {
 179                 if (get_assigned_expr_name_sym(sm->name, sm->sym))
 180                         return 0;
 181                 return 1;
 182         }
 183         if (estate_rl(state))
 184                 return 1;
 185         return 0;
 186 }
 187
 188 void register_param_filter(int id)
 189 {
 190         my_id = id;
 191
 192         set_dynamic_states(my_id);
 193         add_hook(&save_start_states, AFTER_DEF_HOOK);
 194         add_hook(&free_start_states, AFTER_FUNC_HOOK);
 195         add_function_data((unsigned long *)&start_states);
 196
 197         add_extra_mod_hook(&extra_mod_hook);
 198         add_unmatched_state_hook(my_id, &unmatched_state);
 199         add_pre_merge_hook(my_id, &pre_merge_hook);
 200         add_merge_hook(my_id, &merge_estates);
 201
 202         add_split_return_callback(&print_return_value_param);
 203 }
 204