smatch_param_limit.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 almost the same as smatch_param_filter.c.  The difference is that
  20  * this only deals with values passed on the stack and param filter only deals
  21  * with values changed so that the caller sees the new value.  It other words
  22  * the key for these should always be "$" and the key for param_filter should
  23  * never be "$".  Also smatch_param_set() should never use "$" as the key.
  24  * Param set should work together with param_filter to determine the value that
  25  * the caller sees at the end.
  26  *
  27  * This is for functions like this:
  28  *
  29  * int foo(int a)
  30  * {
  31  *        if (a >= 0 && a < 10) {
  32  *                 a = 42;
  33  *                 return 1;
  34  *        }
  35  *        return 0;
  36  * }
  37  *
  38  * If we pass in 5, it returns 1.
  39  *
  40  * It's a bit complicated because we can't just consider the final value, we
  41  * have to always consider the passed in value.
  42  *
  43  */
  44
  45 #include "scope.h"
  46 #include "smatch.h"
  47 #include "smatch_extra.h"
  48 #include "smatch_slist.h"
  49
  50 static int my_id;
  51
  52 static struct smatch_state *unmatched_state(struct sm_state *sm)
  53 {
  54         struct smatch_state *state;
  55
  56         if (!param_was_set_var_sym(sm->name, sm->sym)) {
  57                 state = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
  58                 if (state)
  59                         return state;
  60         }
  61         return alloc_estate_whole(estate_type(sm->state));
  62 }
  63
  64 struct smatch_state *get_orig_estate(const char *name, struct symbol *sym)
  65 {
  66         struct smatch_state *state;
  67
  68         state = get_state(my_id, name, sym);
  69         if (state)
  70                 return state;
  71
  72         state = get_state(SMATCH_EXTRA, name, sym);
  73         if (state)
  74                 return state;
  75         return alloc_estate_rl(alloc_whole_rl(get_real_base_type(sym)));
  76 }
  77
  78 static struct range_list *generify_mtag_range(struct smatch_state *state)
  79 {
  80         struct range_list *rl;
  81         struct data_range *drange;
  82
  83         if (!estate_type(state) || estate_type(state)->type != SYM_PTR)
  84                 return estate_rl(state);
  85
  86         /*
  87          * The problem is that we get too specific on our param limits when we
  88          * know exactly what pointers are passed to a function.  It gets to the
  89          * point where we say "pointer x will succeed, but everything else will
  90          * fail."  And then we introduce a new caller which passes a different
  91          * pointer and it's like, "Sorry bro, that's not possible."
  92          *
  93          */
  94         rl = estate_rl(state);
  95         FOR_EACH_PTR(rl, drange) {
  96                 if (drange->min.value != drange->max.value)
  97                         continue;
  98                 if (drange->min.value == 0)
  99                         continue;
 100                 if (is_err_ptr(drange->min))
 101                         continue;
 102                 return rl_union(valid_ptr_rl, rl);
 103         } END_FOR_EACH_PTR(drange);
 104
 105         return estate_rl(state);
 106 }
 107
 108 static bool sm_was_set(struct sm_state *sm)
 109 {
 110         struct relation *rel;
 111
 112         if (!estate_related(sm->state))
 113                 return param_was_set_var_sym(sm->name, sm->sym);
 114
 115         FOR_EACH_PTR(estate_related(sm->state), rel) {
 116                 if (param_was_set_var_sym(sm->name, sm->sym))
 117                         return true;
 118         } END_FOR_EACH_PTR(rel);
 119         return false;
 120 }
 121
 122 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 123 {
 124         struct smatch_state *state, *old;
 125         struct sm_state *tmp;
 126         struct range_list *rl;
 127         const char *param_name;
 128         int param;
 129
 130         FOR_EACH_MY_SM(SMATCH_EXTRA, __get_cur_stree(), tmp) {
 131                 if (tmp->name[0] == '&')
 132                         continue;
 133                 param = get_param_num_from_sym(tmp->sym);
 134                 if (param < 0)
 135                         continue;
 136
 137                 param_name = get_param_name(tmp);
 138                 if (!param_name)
 139                         continue;
 140
 141                 state = __get_state(my_id, tmp->name, tmp->sym);
 142                 if (!state) {
 143                         if (sm_was_set(tmp))
 144                                 continue;
 145                         state = tmp->state;
 146                 }
 147
 148                 if (estate_is_whole(state) || estate_is_empty(state))
 149                         continue;
 150                 old = get_state_stree(get_start_states(), SMATCH_EXTRA, tmp->name, tmp->sym);
 151                 if (old && rl_equiv(estate_rl(old), estate_rl(state)))
 152                         continue;
 153
 154                 if (is_ignored_kernel_data(param_name))
 155                         continue;
 156
 157                 rl = generify_mtag_range(state);
 158                 sql_insert_return_states(return_id, return_ranges, PARAM_LIMIT,
 159                                          param, param_name, show_rl(rl));
 160         } END_FOR_EACH_SM(tmp);
 161 }
 162
 163 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
 164 {
 165         struct smatch_state *orig;
 166         struct symbol *param_sym;
 167         char *param_name;
 168
 169         if (expr && expr->smatch_flags & Fake)
 170                 return;
 171
 172         param_name = get_param_var_sym_var_sym(name, sym, NULL, &param_sym);
 173         if (!param_name || !param_sym)
 174                 goto free;
 175         if (get_param_num_from_sym(param_sym) < 0)
 176                 goto free;
 177
 178         /* already saved */
 179         if (get_state(my_id, param_name, param_sym))
 180                 goto free;
 181
 182         orig = get_state(SMATCH_EXTRA, param_name, param_sym);
 183         if (!orig)
 184                 orig = alloc_estate_whole(estate_type(state));
 185
 186         set_state(my_id, param_name, param_sym, orig);
 187 free:
 188         free_string(param_name);
 189 }
 190
 191 void register_param_limit(int id)
 192 {
 193         my_id = id;
 194
 195         db_ignore_states(my_id);
 196         set_dynamic_states(my_id);
 197
 198         add_extra_mod_hook(&extra_mod_hook);
 199         add_unmatched_state_hook(my_id, &unmatched_state);
 200         add_merge_hook(my_id, &merge_estates);
 201
 202         add_split_return_callback(&print_return_value_param);
 203 }
 204