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 "smatch.h"
  46 #include "smatch_extra.h"
  47 #include "smatch_slist.h"
  48
  49 static int my_id;
  50
  51 static struct stree *limit_states;
  52 static struct stree *ignore_states;
  53
  54 int __no_limits;
  55
  56 static struct smatch_state *unmatched_state(struct sm_state *sm)
  57 {
  58         struct smatch_state *state;
  59
  60         if (!param_was_set_var_sym(sm->name, sm->sym)) {
  61                 state = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
  62                 if (state)
  63                         return state;
  64         }
  65         return alloc_estate_whole(estate_type(sm->state));
  66 }
  67
  68 struct smatch_state *get_orig_estate(const char *name, struct symbol *sym)
  69 {
  70         struct smatch_state *state;
  71
  72         state = get_state(my_id, name, sym);
  73         if (state)
  74                 return state;
  75
  76         state = get_state(SMATCH_EXTRA, name, sym);
  77         if (state)
  78                 return state;
  79         return alloc_estate_rl(alloc_whole_rl(get_real_base_type(sym)));
  80 }
  81
  82 static struct range_list *generify_mtag_range(struct smatch_state *state)
  83 {
  84         struct range_list *rl;
  85         struct data_range *drange;
  86
  87         if (!estate_type(state) || estate_type(state)->type != SYM_PTR)
  88                 return estate_rl(state);
  89
  90         /*
  91          * The problem is that we get too specific on our param limits when we
  92          * know exactly what pointers are passed to a function.  It gets to the
  93          * point where we say "pointer x will succeed, but everything else will
  94          * fail."  And then we introduce a new caller which passes a different
  95          * pointer and it's like, "Sorry bro, that's not possible."
  96          *
  97          */
  98         rl = estate_rl(state);
  99         FOR_EACH_PTR(rl, drange) {
 100                 if (drange->min.value != drange->max.value)
 101                         continue;
 102                 if (drange->min.value == 0)
 103                         continue;
 104                 if (is_err_ptr(drange->min))
 105                         continue;
 106                 return rl_union(valid_ptr_rl, rl);
 107         } END_FOR_EACH_PTR(drange);
 108
 109         return estate_rl(state);
 110 }
 111
 112 static bool sm_was_set(struct sm_state *sm)
 113 {
 114         struct relation *rel;
 115
 116         if (!estate_related(sm->state))
 117                 return param_was_set_var_sym(sm->name, sm->sym);
 118
 119         FOR_EACH_PTR(estate_related(sm->state), rel) {
 120                 if (param_was_set_var_sym(sm->name, sm->sym))
 121                         return true;
 122         } END_FOR_EACH_PTR(rel);
 123         return false;
 124 }
 125
 126 static bool is_boring_pointer_info(const char *name, struct range_list *rl)
 127 {
 128         char *rl_str;
 129
 130         /*
 131          * One way that PARAM_LIMIT can be set is by dereferencing pointers.
 132          * It's not necessarily very valuable to track that a pointer must
 133          * be non-NULL.  It's even less valuable to know that it's either NULL
 134          * or valid.  It can be nice to know that it's not an error pointer, I
 135          * suppose.  But let's not pass that data back to all the callers
 136          * forever.
 137          *
 138          */
 139
 140         if (strlen(name) < 40)
 141                 return false;
 142
 143         rl_str = show_rl(rl);
 144         if (!rl_str)
 145                 return false;
 146
 147         if (strcmp(rl_str, "4096-ptr_max") == 0 ||
 148             strcmp(rl_str, "0,4096-ptr_max") == 0)
 149                 return true;
 150
 151         return false;
 152 }
 153
 154 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 155 {
 156         struct smatch_state *state, *old;
 157         struct sm_state *tmp;
 158         struct range_list *rl;
 159         const char *param_name;
 160         int param;
 161
 162         FOR_EACH_MY_SM(SMATCH_EXTRA, __get_cur_stree(), tmp) {
 163                 if (tmp->name[0] == '&')
 164                         continue;
 165
 166                 if (!get_state_stree(limit_states, my_id, tmp->name, tmp->sym) &&
 167                     get_state_stree(ignore_states, my_id, tmp->name, tmp->sym))
 168                         continue;
 169
 170                 param = get_param_num_from_sym(tmp->sym);
 171                 if (param < 0)
 172                         continue;
 173
 174                 param_name = get_param_name(tmp);
 175                 if (!param_name)
 176                         continue;
 177
 178                 state = __get_state(my_id, tmp->name, tmp->sym);
 179                 if (!state) {
 180                         if (sm_was_set(tmp))
 181                                 continue;
 182                         state = tmp->state;
 183                 }
 184
 185                 if (estate_is_whole(state) || estate_is_empty(state))
 186                         continue;
 187                 old = get_state_stree(get_start_states(), SMATCH_EXTRA, tmp->name, tmp->sym);
 188                 if (old && rl_equiv(estate_rl(old), estate_rl(state)))
 189                         continue;
 190
 191                 if (is_ignored_kernel_data(param_name))
 192                         continue;
 193
 194                 rl = generify_mtag_range(state);
 195                 if (is_boring_pointer_info(param_name, rl))
 196                         continue;
 197
 198                 sql_insert_return_states(return_id, return_ranges, PARAM_LIMIT,
 199                                          param, param_name, show_rl(rl));
 200         } END_FOR_EACH_SM(tmp);
 201 }
 202
 203 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
 204 {
 205         struct smatch_state *orig;
 206         struct symbol *param_sym;
 207         char *param_name;
 208
 209         if (expr && expr->smatch_flags & Fake)
 210                 return;
 211
 212         param_name = get_param_var_sym_var_sym(name, sym, NULL, &param_sym);
 213         if (!param_name || !param_sym)
 214                 goto free;
 215         if (get_param_num_from_sym(param_sym) < 0)
 216                 goto free;
 217
 218         /* already saved */
 219         if (get_state(my_id, param_name, param_sym))
 220                 goto free;
 221
 222         if (__in_buf_clear)
 223                 return;
 224
 225         orig = get_state(SMATCH_EXTRA, param_name, param_sym);
 226         if (!orig)
 227                 orig = alloc_estate_whole(estate_type(state));
 228
 229         set_state(my_id, param_name, param_sym, orig);
 230 free:
 231         free_string(param_name);
 232 }
 233
 234 static void extra_nomod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
 235 {
 236         if (__no_limits) {
 237                 set_state_stree(&ignore_states, my_id, name, sym, &undefined);
 238                 return;
 239         }
 240         set_state_stree(&limit_states, my_id, name, sym, &undefined);
 241 }
 242
 243 static void match_end_func(struct symbol *sym)
 244 {
 245         free_stree(&ignore_states);
 246         free_stree(&limit_states);
 247 }
 248
 249 void register_param_limit(int id)
 250 {
 251         my_id = id;
 252
 253         add_function_data((unsigned long *)&limit_states);
 254         add_function_data((unsigned long *)&ignore_states);
 255         add_hook(&match_end_func, END_FUNC_HOOK);
 256
 257         db_ignore_states(my_id);
 258         set_dynamic_states(my_id);
 259
 260         add_extra_mod_hook(&extra_mod_hook);
 261         add_extra_nomod_hook(&extra_nomod_hook);
 262         add_unmatched_state_hook(my_id, &unmatched_state);
 263         add_merge_hook(my_id, &merge_estates);
 264
 265         add_split_return_callback(&print_return_value_param);
 266 }
 267