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         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 struct smatch_state *get_orig_estate(const char *name, struct symbol *sym)
  63 {
  64         struct smatch_state *state;
  65
  66         state = get_state(my_id, name, sym);
  67         if (state)
  68                 return state;
  69
  70         state = get_state(SMATCH_EXTRA, name, sym);
  71         if (state)
  72                 return state;
  73         return alloc_estate_rl(alloc_whole_rl(get_real_base_type(sym)));
  74 }
  75
  76 struct smatch_state *get_orig_estate_type(const char *name, struct symbol *sym, struct symbol *type)
  77 {
  78         struct smatch_state *state;
  79
  80         state = get_state(my_id, name, sym);
  81         if (state)
  82                 return state;
  83
  84         state = get_state(SMATCH_EXTRA, name, sym);
  85         if (state)
  86                 return state;
  87         return alloc_estate_rl(alloc_whole_rl(type));
  88 }
  89
  90 static struct range_list *generify_mtag_range(struct smatch_state *state)
  91 {
  92         struct range_list *rl;
  93         struct data_range *drange;
  94
  95         if (!estate_type(state) || estate_type(state)->type != SYM_PTR)
  96                 return estate_rl(state);
  97
  98         /*
  99          * The problem is that we get too specific on our param limits when we
 100          * know exactly what pointers are passed to a function.  It gets to the
 101          * point where we say "pointer x will succeed, but everything else will
 102          * fail."  And then we introduce a new caller which passes a different
 103          * pointer and it's like, "Sorry bro, that's not possible."
 104          *
 105          */
 106         rl = estate_rl(state);
 107         FOR_EACH_PTR(rl, drange) {
 108                 if (drange->min.value != drange->max.value)
 109                         continue;
 110                 if (drange->min.value == 0)
 111                         continue;
 112                 if (is_err_ptr(drange->min))
 113                         continue;
 114                 return rl_union(valid_ptr_rl, rl);
 115         } END_FOR_EACH_PTR(drange);
 116
 117         return estate_rl(state);
 118 }
 119
 120 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 121 {
 122         struct smatch_state *state, *old;
 123         struct sm_state *tmp;
 124         struct range_list *rl;
 125         const char *param_name;
 126         int param;
 127
 128         FOR_EACH_MY_SM(SMATCH_EXTRA, __get_cur_stree(), tmp) {
 129                 param = get_param_num_from_sym(tmp->sym);
 130                 if (param < 0)
 131                         continue;
 132
 133                 param_name = get_param_name(tmp);
 134                 if (!param_name)
 135                         continue;
 136
 137                 state = __get_state(my_id, tmp->name, tmp->sym);
 138                 if (!state)
 139                         state = tmp->state;
 140
 141                 if (estate_is_whole(state) || estate_is_empty(state))
 142                         continue;
 143                 old = get_state_stree(get_start_states(), SMATCH_EXTRA, tmp->name, tmp->sym);
 144                 if (old && rl_equiv(estate_rl(old), estate_rl(state)))
 145                         continue;
 146
 147                 if (is_ignored_kernel_data(param_name))
 148                         continue;
 149
 150                 rl = generify_mtag_range(state);
 151                 sql_insert_return_states(return_id, return_ranges, PARAM_LIMIT,
 152                                          param, param_name, show_rl(rl));
 153         } END_FOR_EACH_SM(tmp);
 154 }
 155
 156 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
 157 {
 158         struct smatch_state *orig_vals;
 159         int param;
 160
 161         param = get_param_num_from_sym(sym);
 162         if (param < 0)
 163                 return;
 164
 165         orig_vals = get_orig_estate_type(name, sym, estate_type(state));
 166         set_state(my_id, name, sym, orig_vals);
 167 }
 168
 169 void register_param_limit(int id)
 170 {
 171         my_id = id;
 172
 173         set_dynamic_states(my_id);
 174
 175         add_extra_mod_hook(&extra_mod_hook);
 176         add_unmatched_state_hook(my_id, &unmatched_state);
 177         add_merge_hook(my_id, &merge_estates);
 178
 179         add_split_return_callback(&print_return_value_param);
 180 }
 181