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 struct stree_stack *saved_stack;
  40 static void save_start_states(struct statement *stmt)
  41 {
  42         start_states = get_all_states_stree(SMATCH_EXTRA);
  43 }
  44
  45 static void free_start_states(void)
  46 {
  47         free_stree(&start_states);
  48 }
  49
  50 static void match_save_states(struct expression *expr)
  51 {
  52         push_stree(&saved_stack, start_states);
  53         start_states = NULL;
  54 }
  55
  56 static void match_restore_states(struct expression *expr)
  57 {
  58         free_stree(&start_states);
  59         start_states = pop_stree(&saved_stack);
  60 }
  61
  62 static struct smatch_state *unmatched_state(struct sm_state *sm)
  63 {
  64         struct smatch_state *state;
  65
  66         if (parent_is_gone_var_sym(sm->name, sm->sym))
  67                 return alloc_estate_empty();
  68
  69         state = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
  70         if (state)
  71                 return state;
  72         return alloc_estate_whole(estate_type(sm->state));
  73 }
  74
  75 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
  76 {
  77         struct smatch_state *extra;
  78         struct range_list *rl;
  79
  80         if (estate_rl(other->state))
  81                 return;
  82
  83         extra = get_state(SMATCH_EXTRA, cur->name, cur->sym);
  84         if (!extra)
  85                 return;
  86
  87         rl = rl_intersection(estate_rl(extra), estate_rl(cur->state));
  88         if (rl_equiv(rl, estate_rl(cur->state)))
  89                 return;
  90         set_state(my_id, cur->name, cur->sym, alloc_estate_rl(clone_rl(rl)));
  91 }
  92
  93 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
  94 {
  95         int param;
  96
  97         if (__in_fake_assign)
  98                 return;
  99
 100         param = get_param_num_from_sym(sym);
 101         if (param < 0)
 102                 return;
 103
 104         /* on stack parameters are handled in smatch_param_limit.c */
 105         if (sym->ident && strcmp(sym->ident->name, name) == 0)
 106                 return;
 107
 108         set_state(my_id, name, sym, alloc_estate_empty());
 109 }
 110
 111 /*
 112  * This relies on the fact that these states are stored so that
 113  * foo->bar is before foo->bar->baz.
 114  */
 115 static int parent_set(struct string_list *list, const char *name)
 116 {
 117         char *tmp;
 118         int len;
 119         int ret;
 120
 121         FOR_EACH_PTR(list, tmp) {
 122                 len = strlen(tmp);
 123                 ret = strncmp(tmp, name, len);
 124                 if (ret < 0)
 125                         continue;
 126                 if (ret > 0)
 127                         return 0;
 128                 if (name[len] == '-')
 129                         return 1;
 130         } END_FOR_EACH_PTR(tmp);
 131
 132         return 0;
 133 }
 134
 135 static void print_one_mod_param(int return_id, char *return_ranges,
 136                         int param, struct sm_state *sm, struct string_list **totally_filtered)
 137 {
 138         const char *param_name;
 139
 140         param_name = get_param_name(sm);
 141         if (!param_name)
 142                 return;
 143         if (is_whole_rl(estate_rl(sm->state)))
 144                 return;
 145         if (!estate_rl(sm->state)) {
 146                 insert_string(totally_filtered, (char *)sm->name);
 147                 return;
 148         }
 149
 150         if (is_ignored_kernel_data(param_name)) {
 151                 insert_string(totally_filtered, (char *)sm->name);
 152                 return;
 153         }
 154
 155         sql_insert_return_states(return_id, return_ranges, PARAM_FILTER, param,
 156                         param_name, show_rl(estate_rl(sm->state)));
 157 }
 158
 159 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 160 {
 161         struct sm_state *tmp;
 162         struct sm_state *sm;
 163         struct string_list *totally_filtered = NULL;
 164         int param;
 165
 166         FOR_EACH_MY_SM(SMATCH_EXTRA, __get_cur_stree(), tmp) {
 167                 param = get_param_num_from_sym(tmp->sym);
 168                 if (param < 0)
 169                         continue;
 170
 171                 /* on stack parameters are handled in smatch_param_limit.c */
 172                 if (tmp->sym->ident && strcmp(tmp->sym->ident->name, tmp->name) == 0)
 173                         continue;
 174
 175                 if (parent_set(totally_filtered, tmp->name))
 176                         continue;
 177
 178                 sm = get_sm_state(my_id, tmp->name, tmp->sym);
 179                 if (sm)
 180                         print_one_mod_param(return_id, return_ranges, param, sm, &totally_filtered);
 181         } END_FOR_EACH_SM(tmp);
 182
 183         free_ptr_list((struct ptr_list **)&totally_filtered);
 184 }
 185
 186 int param_has_filter_data(struct sm_state *sm)
 187 {
 188         struct smatch_state *state;
 189
 190         state = get_state(my_id, sm->name, sm->sym);
 191         if (!state) {
 192                 if (get_assigned_expr_name_sym(sm->name, sm->sym))
 193                         return 0;
 194                 return 1;
 195         }
 196         if (estate_rl(state))
 197                 return 1;
 198         return 0;
 199 }
 200
 201 void register_param_filter(int id)
 202 {
 203         my_id = id;
 204
 205         set_dynamic_states(my_id);
 206         add_hook(&save_start_states, AFTER_DEF_HOOK);
 207         add_hook(&free_start_states, AFTER_FUNC_HOOK);
 208
 209         add_extra_mod_hook(&extra_mod_hook);
 210         add_unmatched_state_hook(my_id, &unmatched_state);
 211         add_pre_merge_hook(my_id, &pre_merge_hook);
 212         add_merge_hook(my_id, &merge_estates);
 213
 214         add_hook(&match_save_states, INLINE_FN_START);
 215         add_hook(&match_restore_states, INLINE_FN_END);
 216
 217         add_split_return_callback(&print_return_value_param);
 218 }
 219