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 STATE(original);
  53
  54 static struct stree *start_states;
  55 static struct stree_stack *saved_stack;
  56
  57 static void save_start_states(struct statement *stmt)
  58 {
  59         start_states = get_all_states_stree(SMATCH_EXTRA);
  60 }
  61
  62 static void free_start_states(void)
  63 {
  64         free_stree(&start_states);
  65 }
  66
  67 static struct smatch_state *unmatched_state(struct sm_state *sm)
  68 {
  69         return &original;
  70 }
  71
  72 static struct smatch_state *filter_my_sm(struct sm_state *sm)
  73 {
  74         struct range_list *ret = NULL;
  75         struct sm_state *tmp;
  76         struct smatch_state *estate;
  77
  78         FOR_EACH_PTR(sm->possible, tmp) {
  79                 if (tmp->state == &merged)
  80                         continue;
  81                 if (tmp->state == &original) {
  82                         estate = get_state_stree(tmp->pool, SMATCH_EXTRA, tmp->name, tmp->sym);
  83                         if (!estate) {
  84 //                              sm_msg("debug: no value found in pool %p", tmp->pool);
  85                                 continue;
  86                         }
  87                 } else {
  88                         estate = tmp->state;
  89                 }
  90                 ret = rl_union(ret, estate_rl(estate));
  91         } END_FOR_EACH_PTR(tmp);
  92
  93         return alloc_estate_rl(ret);
  94 }
  95
  96 struct smatch_state *get_orig_estate(const char *name, struct symbol *sym)
  97 {
  98         struct sm_state *sm;
  99         struct smatch_state *state;
 100
 101         sm = get_sm_state(my_id, name, sym);
 102         if (sm)
 103                 return filter_my_sm(sm);
 104
 105         state = get_state(SMATCH_EXTRA, name, sym);
 106         if (state)
 107                 return state;
 108         return alloc_estate_rl(alloc_whole_rl(get_real_base_type(sym)));
 109 }
 110
 111 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 112 {
 113         struct stree *stree;
 114         struct sm_state *tmp;
 115         struct sm_state *my_sm;
 116         struct smatch_state *state;
 117         int param;
 118         char *compare;
 119         const char *compare_str;
 120         char buf[256];
 121
 122         stree = __get_cur_stree();
 123
 124         FOR_EACH_MY_SM(SMATCH_EXTRA, stree, tmp) {
 125                 if (!tmp->sym || !tmp->sym->ident || strcmp(tmp->name, tmp->sym->ident->name) != 0)
 126                         continue;
 127
 128                 param = get_param_num_from_sym(tmp->sym);
 129                 if (param < 0)
 130                         continue;
 131
 132                 compare = expr_param_comparison(symbol_expression(tmp->sym), param);
 133                 if (!compare)
 134                         compare = expr_equal_to_param(symbol_expression(tmp->sym), param);
 135                 if (!compare)
 136                         compare = expr_lte_to_param(symbol_expression(tmp->sym), param);
 137                 compare_str = compare;
 138                 if (!compare_str)
 139                         compare_str = "";
 140
 141                 my_sm = get_sm_state(my_id, tmp->name, tmp->sym);
 142                 if (!my_sm) {
 143                         struct smatch_state *old;
 144
 145                         if (estate_is_whole(tmp->state) && !compare)
 146                                 continue;
 147                         old = get_state_stree(start_states, SMATCH_EXTRA, tmp->name, tmp->sym);
 148                         if (old && estates_equiv(old, tmp->state) && !compare)
 149                                 continue;
 150
 151                         snprintf(buf, sizeof(buf), "%s%s", tmp->state->name, compare_str);
 152                         sql_insert_return_states(return_id, return_ranges,
 153                                         LIMITED_VALUE, param, "$", buf);
 154                         continue;
 155                 }
 156
 157                 state = filter_my_sm(my_sm);
 158                 if (!state)
 159                         continue;
 160                 /* This represents an impossible state.  I screwd up.  Bail. */
 161                 if (!estate_rl(state))
 162                         continue;
 163                 if (estate_is_whole(state) && !compare) {
 164                         continue;
 165                 }
 166
 167                 snprintf(buf, sizeof(buf), "%s%s", state->name, compare_str);
 168                 sql_insert_return_states(return_id, return_ranges,
 169                                         LIMITED_VALUE, param, "$", buf);
 170         } END_FOR_EACH_SM(tmp);
 171 }
 172
 173 static void extra_mod_hook(const char *name, struct symbol *sym, struct smatch_state *state)
 174 {
 175         struct smatch_state *orig_vals;
 176         int param;
 177
 178         param = get_param_num_from_sym(sym);
 179         if (param < 0)
 180                 return;
 181
 182         /* we are only saving params for now */
 183         if (!sym->ident || strcmp(name, sym->ident->name) != 0)
 184                 return;
 185
 186         orig_vals = get_orig_estate(name, sym);
 187         set_state(my_id, name, sym, orig_vals);
 188 }
 189
 190 static void match_save_states(struct expression *expr)
 191 {
 192         push_stree(&saved_stack, start_states);
 193         start_states = NULL;
 194 }
 195
 196 static void match_restore_states(struct expression *expr)
 197 {
 198         free_stree(&start_states);
 199         start_states = pop_stree(&saved_stack);
 200 }
 201
 202 void register_param_limit(int id)
 203 {
 204         my_id = id;
 205
 206         add_hook(&save_start_states, AFTER_DEF_HOOK);
 207         add_hook(&free_start_states, END_FUNC_HOOK);
 208
 209         add_extra_mod_hook(&extra_mod_hook);
 210         add_unmatched_state_hook(my_id, &unmatched_state);
 211
 212         add_hook(&match_save_states, INLINE_FN_START);
 213         add_hook(&match_restore_states, INLINE_FN_END);
 214
 215         add_split_return_callback(&print_return_value_param);
 216 }
 217