smatch_param_filter.c

   1 /*
   2  * sparse/smatch_param_filter.c
   3  *
   4  * Copyright (C) 2012 Oracle.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * This is for functions like:
  12  *
  13  * void foo(int *x)
  14  * {
  15  *      if (*x == 42)
  16  *              *x = 0;
  17  * }
  18  *
  19  * The final value of *x depends on the input to the function but with *x == 42
  20  * filtered out.
  21  *
  22  */
  23
  24 #include "smatch.h"
  25 #include "smatch_extra.h"
  26 #include "smatch_slist.h"
  27
  28 static int my_id;
  29
  30 STATE(modified);
  31 STATE(original);
  32
  33 static struct state_list *start_states;
  34 static void save_start_states(struct statement *stmt)
  35 {
  36         start_states = get_all_states(SMATCH_EXTRA);
  37 }
  38
  39 static void match_end_func(void)
  40 {
  41         free_slist(&start_states);
  42 }
  43
  44 static struct smatch_state *unmatched_state(struct sm_state *sm)
  45 {
  46         return &original;
  47 }
  48
  49 static void extra_mod_hook(const char *name, struct symbol *sym, struct smatch_state *state)
  50 {
  51         int param;
  52
  53         param = get_param_num_from_sym(sym);
  54         if (param < 0)
  55                 return;
  56
  57         set_state(my_id, name, sym, &modified);
  58 }
  59
  60 static const char *get_param_name(struct sm_state *sm)
  61 {
  62         char *param_name;
  63         int name_len;
  64         static char buf[256];
  65
  66         if (!sm->sym->ident)
  67                 return NULL;
  68
  69         param_name = sm->sym->ident->name;
  70         name_len = strlen(param_name);
  71
  72         if (strcmp(sm->name, param_name) == 0) {
  73                 return "$$";
  74         } else if (sm->name[name_len] == '-' && /* check for '-' from "->" */
  75             strncmp(sm->name, param_name, name_len) == 0) {
  76                 snprintf(buf, sizeof(buf), "$$%s", sm->name + name_len);
  77                 return buf;
  78         } else if (sm->name[0] == '*' && strcmp(sm->name + 1, param_name) == 0) {
  79                 return "*$$";
  80         }
  81         return NULL;
  82 }
  83
  84 static char *get_orig_rl(struct sm_state *sm)
  85 {
  86         struct range_list *ret = NULL;
  87         struct sm_state *tmp;
  88         struct smatch_state *extra;
  89
  90         FOR_EACH_PTR(sm->possible, tmp) {
  91                 if (tmp->state != &original)
  92                         continue;
  93                 extra = get_state_slist(tmp->pool, SMATCH_EXTRA, tmp->name, tmp->sym);
  94                 if (!extra) {
  95                         sm_msg("debug: no value found in pool %p", tmp->pool);
  96                         return NULL;
  97                 }
  98                 ret = rl_union(ret, estate_rl(extra));
  99         } END_FOR_EACH_PTR(tmp);
 100         return show_rl(ret);
 101 }
 102
 103 static void print_one_mod_param(int return_id, char *return_ranges,
 104                         int param, struct sm_state *sm, struct state_list *slist)
 105 {
 106         const char *param_name;
 107         char *filter;
 108
 109         param_name = get_param_name(sm);
 110         if (!param_name)
 111                 return;
 112         filter = get_orig_rl(sm);
 113         if (!filter)
 114                 return;
 115
 116         sql_insert_return_states(return_id, return_ranges, FILTER_VALUE, param,
 117                         param_name, filter);
 118 }
 119
 120 static void print_one_extra_param(int return_id, char *return_ranges,
 121                         int param, struct sm_state *sm, struct state_list *slist)
 122 {
 123         struct smatch_state *old;
 124         const char *param_name;
 125
 126         old = get_state_slist(start_states, SMATCH_EXTRA, sm->name, sm->sym);
 127         if (old && estates_equiv(old, sm->state))
 128                 return;
 129
 130         param_name = get_param_name(sm);
 131         if (!param_name)
 132                 return;
 133
 134         sql_insert_return_states(return_id, return_ranges, FILTER_VALUE, param,
 135                         param_name, sm->state->name);
 136 }
 137
 138 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr, struct state_list *slist)
 139 {
 140         struct state_list *extra_slist;
 141         struct sm_state *tmp;
 142         struct sm_state *sm;
 143         int param;
 144
 145         extra_slist = get_all_states_slist(SMATCH_EXTRA, slist);
 146
 147         FOR_EACH_PTR(extra_slist, tmp) {
 148                 param = get_param_num_from_sym(tmp->sym);
 149                 if (param < 0)
 150                         continue;
 151                 /*
 152                  * skip the parameter itself because that's handled by
 153                  * smatch_param_limit.c.
 154                  */
 155                 if (tmp->sym->ident && strcmp(tmp->sym->ident->name, tmp->name) == 0)
 156                         continue;
 157
 158                 sm = get_sm_state_slist(slist, my_id, tmp->name, tmp->sym);
 159                 if (sm)
 160                         print_one_mod_param(return_id, return_ranges, param, sm, slist);
 161                 else
 162                         print_one_extra_param(return_id, return_ranges, param, tmp, slist);
 163         } END_FOR_EACH_PTR(tmp);
 164
 165         free_slist(&extra_slist);
 166 }
 167
 168 void register_param_filter(int id)
 169 {
 170         if (!option_info)
 171                 return;
 172
 173         my_id = id;
 174
 175         add_hook(&save_start_states, AFTER_DEF_HOOK);
 176         add_extra_mod_hook(&extra_mod_hook);
 177         add_unmatched_state_hook(my_id, &unmatched_state);
 178         add_returned_state_callback(&print_return_value_param);
 179         add_hook(&match_end_func, END_FUNC_HOOK);
 180 }
 181