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 struct state_list_stack *saved_stack;
  35 static void save_start_states(struct statement *stmt)
  36 {
  37         start_states = get_all_states(SMATCH_EXTRA);
  38 }
  39
  40 static void match_end_func(void)
  41 {
  42         free_slist(&start_states);
  43 }
  44
  45 static void match_save_states(struct expression *expr)
  46 {
  47         push_slist(&saved_stack, start_states);
  48         start_states = NULL;
  49 }
  50
  51 static void match_restore_states(struct expression *expr)
  52 {
  53         start_states = pop_slist(&saved_stack);
  54 }
  55
  56 static struct smatch_state *unmatched_state(struct sm_state *sm)
  57 {
  58         return &original;
  59 }
  60
  61 static void extra_mod_hook(const char *name, struct symbol *sym, struct smatch_state *state)
  62 {
  63         int param;
  64
  65         param = get_param_num_from_sym(sym);
  66         if (param < 0)
  67                 return;
  68
  69         set_state(my_id, name, sym, &modified);
  70 }
  71
  72 static const char *get_param_name(struct sm_state *sm)
  73 {
  74         char *param_name;
  75         int name_len;
  76         static char buf[256];
  77
  78         if (!sm->sym->ident)
  79                 return NULL;
  80
  81         param_name = sm->sym->ident->name;
  82         name_len = strlen(param_name);
  83
  84         if (strcmp(sm->name, param_name) == 0) {
  85                 return "$$";
  86         } else if (sm->name[name_len] == '-' && /* check for '-' from "->" */
  87             strncmp(sm->name, param_name, name_len) == 0) {
  88                 snprintf(buf, sizeof(buf), "$$%s", sm->name + name_len);
  89                 return buf;
  90         } else if (sm->name[0] == '*' && strcmp(sm->name + 1, param_name) == 0) {
  91                 return "*$$";
  92         }
  93         return NULL;
  94 }
  95
  96 static char *get_orig_rl(struct sm_state *sm)
  97 {
  98         struct range_list *ret = NULL;
  99         struct sm_state *tmp;
 100         struct smatch_state *extra;
 101
 102         FOR_EACH_PTR(sm->possible, tmp) {
 103                 if (tmp->state != &original)
 104                         continue;
 105                 extra = get_state_slist(tmp->pool, SMATCH_EXTRA, tmp->name, tmp->sym);
 106                 if (!extra) {
 107 //                      sm_msg("debug: no value found in pool %p", tmp->pool);
 108                         return NULL;
 109                 }
 110                 ret = rl_union(ret, estate_rl(extra));
 111         } END_FOR_EACH_PTR(tmp);
 112         return show_rl(ret);
 113 }
 114
 115 static void print_one_mod_param(int return_id, char *return_ranges,
 116                         int param, struct sm_state *sm, struct state_list *slist)
 117 {
 118         const char *param_name;
 119         char *filter;
 120
 121         param_name = get_param_name(sm);
 122         if (!param_name)
 123                 return;
 124         filter = get_orig_rl(sm);
 125         if (!filter)
 126                 return;
 127
 128         sql_insert_return_states(return_id, return_ranges, FILTER_VALUE, param,
 129                         param_name, filter);
 130 }
 131
 132 static void print_one_extra_param(int return_id, char *return_ranges,
 133                         int param, struct sm_state *sm, struct state_list *slist)
 134 {
 135         struct smatch_state *old;
 136         const char *param_name;
 137
 138         old = get_state_slist(start_states, SMATCH_EXTRA, sm->name, sm->sym);
 139         if (old && estates_equiv(old, sm->state))
 140                 return;
 141
 142         param_name = get_param_name(sm);
 143         if (!param_name)
 144                 return;
 145
 146         sql_insert_return_states(return_id, return_ranges, FILTER_VALUE, param,
 147                         param_name, sm->state->name);
 148 }
 149
 150 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr, struct state_list *slist)
 151 {
 152         struct state_list *extra_slist;
 153         struct sm_state *tmp;
 154         struct sm_state *sm;
 155         int param;
 156
 157         extra_slist = get_all_states_slist(SMATCH_EXTRA, slist);
 158
 159         FOR_EACH_PTR(extra_slist, tmp) {
 160                 param = get_param_num_from_sym(tmp->sym);
 161                 if (param < 0)
 162                         continue;
 163                 /*
 164                  * skip the parameter itself because that's handled by
 165                  * smatch_param_limit.c.
 166                  */
 167                 if (tmp->sym->ident && strcmp(tmp->sym->ident->name, tmp->name) == 0)
 168                         continue;
 169
 170                 sm = get_sm_state_slist(slist, my_id, tmp->name, tmp->sym);
 171                 if (sm)
 172                         print_one_mod_param(return_id, return_ranges, param, sm, slist);
 173                 else
 174                         print_one_extra_param(return_id, return_ranges, param, tmp, slist);
 175         } END_FOR_EACH_PTR(tmp);
 176
 177         free_slist(&extra_slist);
 178 }
 179
 180 void register_param_filter(int id)
 181 {
 182         my_id = id;
 183
 184         add_hook(&save_start_states, AFTER_DEF_HOOK);
 185         add_extra_mod_hook(&extra_mod_hook);
 186         add_unmatched_state_hook(my_id, &unmatched_state);
 187         add_returned_state_callback(&print_return_value_param);
 188         add_hook(&match_end_func, END_FUNC_HOOK);
 189         add_hook(&match_save_states, INLINE_FN_START);
 190         add_hook(&match_restore_states, INLINE_FN_END);
 191 }
 192