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 stree *start_states;
  53 static struct stree_stack *saved_stack;
  54
  55 static void save_start_states(struct statement *stmt)
  56 {
  57         struct smatch_state *state;
  58         struct symbol *tmp;
  59
  60         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, tmp) {
  61                 if (!tmp->ident)
  62                         continue;
  63                 state = get_state(SMATCH_EXTRA, tmp->ident->name, tmp);
  64                 if (!state)
  65                         state = alloc_estate_whole(get_real_base_type(tmp));
  66                 set_state_stree(&start_states, SMATCH_EXTRA, tmp->ident->name, tmp, state);
  67         } END_FOR_EACH_PTR(tmp);
  68 }
  69
  70 static void free_start_states(void)
  71 {
  72         free_stree(&start_states);
  73 }
  74
  75 static struct smatch_state *unmatched_state(struct sm_state *sm)
  76 {
  77         struct smatch_state *state;
  78
  79         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
  80         if (state)
  81                 return state;
  82         return alloc_estate_whole(get_real_base_type(sm->sym));
  83 }
  84
  85 struct smatch_state *get_orig_estate(const char *name, struct symbol *sym)
  86 {
  87         struct smatch_state *state;
  88
  89         state = get_state(my_id, name, sym);
  90         if (state)
  91                 return state;
  92
  93         state = get_state(SMATCH_EXTRA, name, sym);
  94         if (state)
  95                 return state;
  96         return alloc_estate_rl(alloc_whole_rl(get_real_base_type(sym)));
  97 }
  98
  99 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 100 {
 101         struct smatch_state *start_state, *state;
 102         struct symbol *tmp;
 103         int param;
 104
 105         param = -1;
 106         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, tmp) {
 107                 param++;
 108                 if (!tmp->ident)
 109                         continue;
 110                 state = get_state(my_id, tmp->ident->name, tmp);
 111                 if (state)
 112                         goto print;
 113                 state = get_state(SMATCH_EXTRA, tmp->ident->name, tmp);
 114                 if (state)
 115                         goto print;
 116                 continue;
 117 print:
 118                 if (estate_is_whole(state))
 119                         continue;
 120
 121                 start_state = get_state_stree(start_states, SMATCH_EXTRA, tmp->ident->name, tmp);
 122                 if (estates_equiv(state, start_state))
 123                         continue;
 124 //              sm_msg("return_range %s limited '%s' from %s to %s", return_ranges, tmp->ident->name, start_state->name, state->name);
 125                 sql_insert_return_states(return_id, return_ranges,
 126                                 LIMITED_VALUE, param, "$", state->name);
 127         } END_FOR_EACH_PTR(tmp);
 128 }
 129
 130 static void extra_mod_hook(const char *name, struct symbol *sym, struct smatch_state *state)
 131 {
 132         struct smatch_state *orig_vals;
 133         int param;
 134
 135         param = get_param_num_from_sym(sym);
 136         if (param < 0)
 137                 return;
 138
 139         /* we only save on-stack params */
 140         if (!sym->ident || strcmp(name, sym->ident->name) != 0)
 141                 return;
 142
 143         orig_vals = get_orig_estate(name, sym);
 144         set_state(my_id, name, sym, orig_vals);
 145 }
 146
 147 static void match_save_states(struct expression *expr)
 148 {
 149         push_stree(&saved_stack, start_states);
 150         start_states = NULL;
 151 }
 152
 153 static void match_restore_states(struct expression *expr)
 154 {
 155         free_stree(&start_states);
 156         start_states = pop_stree(&saved_stack);
 157 }
 158
 159 void register_param_limit(int id)
 160 {
 161         my_id = id;
 162
 163         add_hook(&save_start_states, AFTER_DEF_HOOK);
 164         add_hook(&free_start_states, END_FUNC_HOOK);
 165
 166         add_extra_mod_hook(&extra_mod_hook);
 167         add_unmatched_state_hook(my_id, &unmatched_state);
 168         add_merge_hook(my_id, &merge_estates);
 169
 170         add_hook(&match_save_states, INLINE_FN_START);
 171         add_hook(&match_restore_states, INLINE_FN_END);
 172
 173         add_split_return_callback(&print_return_value_param);
 174 }
 175