smatch_bits.c

   1 /*
   2  * Copyright (C) 2015 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 to track when variables are masked away.
  20  *
  21  */
  22
  23 #include "smatch.h"
  24 #include "smatch_extra.h"
  25 #include "smatch_slist.h"
  26
  27 static int my_id;
  28
  29 static const struct bit_info unknown_bit_info = {
  30         .possible = -1ULL,
  31 };
  32
  33 ALLOCATOR(bit_info, "bit data");
  34 static struct bit_info *alloc_bit_info(unsigned long long set, unsigned long long possible)
  35 {
  36         struct bit_info *bit_info = __alloc_bit_info(0);
  37
  38         bit_info->set = set;
  39         bit_info->possible = possible;
  40
  41         return bit_info;
  42 }
  43
  44 static struct smatch_state *alloc_bstate(unsigned long long set, unsigned long long possible)
  45 {
  46         struct smatch_state *state;
  47         char buf[64];
  48
  49         state = __alloc_smatch_state(0);
  50         snprintf(buf, sizeof(buf), "0x%llx + 0x%llx", set, possible);
  51         state->name = alloc_sname(buf);
  52         state->data = alloc_bit_info(set, possible);
  53
  54         return state;
  55 }
  56
  57 struct bit_info *rl_to_binfo(struct range_list *rl)
  58 {
  59         struct bit_info *ret = __alloc_bit_info(0);
  60         sval_t sval;
  61
  62         if (rl_to_sval(rl, &sval)) {
  63                 ret->set = sval.uvalue;
  64                 ret->possible = sval.uvalue;
  65
  66                 return ret;
  67         }
  68
  69         ret->set = 0;
  70         ret->possible = sval_fls_mask(rl_max(rl));
  71         // FIXME: what about negatives?
  72
  73         return ret;
  74 }
  75
  76 static int is_unknown_binfo(struct symbol *type, struct bit_info *binfo)
  77 {
  78         if (!type)
  79                 type = &ullong_ctype;
  80
  81         if (binfo->set != 0)
  82                 return 0;
  83         if (binfo->possible < (-1ULL >> (64 - type_bits(type))))
  84                 return 0;
  85
  86         return 1;
  87 }
  88
  89 static struct smatch_state *unmatched_state(struct sm_state *sm)
  90 {
  91         struct smatch_state *estate;
  92         struct symbol *type;
  93         unsigned long long possible;
  94         struct bit_info *p;
  95
  96         estate = get_state(SMATCH_EXTRA, sm->name, sm->sym);
  97         if (estate_rl(estate)) {
  98                 p = rl_to_binfo(estate_rl(estate));
  99                 return alloc_bstate(p->set, p->possible);
 100         }
 101
 102         type = estate_type(estate);
 103         if (!type)
 104                 return alloc_bstate(0, -1ULL);
 105
 106         if (type_bits(type) == 64)
 107                 possible = -1ULL;
 108         else
 109                 possible = (1ULL << type_bits(type)) - 1;
 110
 111         return alloc_bstate(0, possible);
 112 }
 113
 114 static bool is_loop_iterator(struct expression *expr)
 115 {
 116         struct statement *pre_stmt, *loop_stmt;
 117
 118         pre_stmt = expr_get_parent_stmt(expr);
 119         if (!pre_stmt || pre_stmt->type != STMT_EXPRESSION)
 120                 return false;
 121
 122         loop_stmt = stmt_get_parent_stmt(pre_stmt);
 123         if (!loop_stmt || loop_stmt->type != STMT_ITERATOR)
 124                 return false;
 125         if (loop_stmt->iterator_pre_statement != pre_stmt)
 126                 return false;
 127
 128         return true;
 129 }
 130
 131 static void match_modify(struct sm_state *sm, struct expression *mod_expr)
 132 {
 133         // FIXME: we really need to store the type
 134
 135         set_state(my_id, sm->name, sm->sym, alloc_bstate(0, -1ULL));
 136 }
 137
 138 static int binfo_equiv(struct bit_info *one, struct bit_info *two)
 139 {
 140         if (one->set == two->set &&
 141             one->possible == two->possible)
 142                 return 1;
 143         return 0;
 144 }
 145
 146 static struct smatch_state *merge_bstates(struct smatch_state *one_state, struct smatch_state *two_state)
 147 {
 148         struct bit_info *one, *two;
 149
 150         one = one_state->data;
 151         two = two_state->data;
 152
 153         if (binfo_equiv(one, two))
 154                 return one_state;
 155
 156         return alloc_bstate(one->set & two->set, one->possible | two->possible);
 157 }
 158
 159 /*
 160  * The combine_bit_info() takes two bit_infos and takes creates the most
 161  * accurate picture we can assuming both are true.  Or it returns unknown if
 162  * the information is logically impossible.
 163  *
 164  * Which means that it takes the | of the ->set bits and the & of the possibly
 165  * set bits, which is the opposite of what merge_bstates() does.
 166  *
 167  */
 168 static struct bit_info *combine_bit_info(struct bit_info *one, struct bit_info *two)
 169 {
 170         struct bit_info *ret = __alloc_bit_info(0);
 171
 172         if ((one->set & two->possible) != one->set)
 173                 return alloc_bit_info(0, -1ULL);
 174         if ((two->set & one->possible) != two->set)
 175                 return alloc_bit_info(0, -1ULL);
 176
 177         ret->set = one->set | two->set;
 178         ret->possible = one->possible & two->possible;
 179
 180         return ret;
 181 }
 182
 183 static struct bit_info *binfo_AND(struct bit_info *left, struct bit_info *right)
 184 {
 185         unsigned long long set = 0;
 186         unsigned long long possible = -1ULL;
 187
 188         if (!left && !right) {
 189                 /* nothing */
 190         } else if (!left) {
 191                 possible = right->possible;
 192         } else if (!right) {
 193                 possible = left->possible;
 194         } else {
 195                 set = left->set & right->set;
 196                 possible = left->possible & right->possible;
 197         }
 198
 199         return alloc_bit_info(set, possible);
 200 }
 201
 202 static struct bit_info *binfo_OR(struct bit_info *left, struct bit_info *right)
 203 {
 204         unsigned long long set = 0;
 205         unsigned long long possible = -1ULL;
 206
 207         if (!left && !right) {
 208                 /* nothing */
 209         } else if (!left) {
 210                 set = right->set;
 211         } else if (!right) {
 212                 set = left->set;
 213         } else {
 214                 set = left->set | right->set;
 215                 possible = left->possible | right->possible;
 216         }
 217
 218         return alloc_bit_info(set, possible);
 219 }
 220
 221 struct bit_info *get_bit_info(struct expression *expr)
 222 {
 223         struct range_list *rl;
 224         struct smatch_state *bstate;
 225         struct bit_info tmp;
 226         struct bit_info *extra_info;
 227         struct bit_info *bit_info;
 228         sval_t known;
 229
 230         expr = strip_parens(expr);
 231
 232         if (get_implied_value(expr, &known))
 233                 return alloc_bit_info(known.value, known.value);
 234
 235         if (expr->type == EXPR_BINOP) {
 236                 if (expr->op == '&')
 237                         return binfo_AND(get_bit_info(expr->left),
 238                                          get_bit_info(expr->right));
 239                 if (expr->op == '|')
 240                         return binfo_OR(get_bit_info(expr->left),
 241                                         get_bit_info(expr->right));
 242         }
 243
 244         if (get_implied_rl(expr, &rl))
 245                 extra_info = rl_to_binfo(rl);
 246         else {
 247                 struct symbol *type;
 248
 249                 tmp = unknown_bit_info;
 250                 extra_info = &tmp;
 251
 252                 type = get_type(expr);
 253                 if (!type)
 254                         type = &ullong_ctype;
 255                 if (type_bits(type) == 64)
 256                         extra_info->possible = -1ULL;
 257                 else
 258                         extra_info->possible = (1ULL << type_bits(type)) - 1;
 259         }
 260
 261         bstate = get_state_expr(my_id, expr);
 262         if (bstate)
 263                 bit_info = bstate->data;
 264         else
 265                 bit_info = (struct bit_info *)&unknown_bit_info;
 266
 267         return combine_bit_info(extra_info, bit_info);
 268 }
 269
 270 static int is_single_bit(sval_t sval)
 271 {
 272         int i;
 273         int count = 0;
 274
 275         for (i = 0; i < 64; i++) {
 276                 if (sval.uvalue & 1ULL << i &&
 277                     count++)
 278                         return 0;
 279         }
 280         if (count == 1)
 281                 return 1;
 282         return 0;
 283 }
 284
 285 static void match_compare(struct expression *expr)
 286 {
 287         sval_t val;
 288
 289         if (expr->type != EXPR_COMPARE)
 290                 return;
 291         if (expr->op != SPECIAL_EQUAL &&
 292             expr->op != SPECIAL_NOTEQUAL)
 293                 return;
 294
 295         if (!get_implied_value(expr->right, &val))
 296                 return;
 297
 298         set_true_false_states_expr(my_id, expr->left,
 299                         (expr->op == SPECIAL_EQUAL) ? alloc_bstate(val.uvalue, val.uvalue) : NULL,
 300                         (expr->op == SPECIAL_EQUAL) ? NULL : alloc_bstate(val.uvalue, val.uvalue));
 301 }
 302
 303 static void match_assign(struct expression *expr)
 304 {
 305         struct bit_info *binfo;
 306
 307         if (expr->op != '=')
 308                 return;
 309         if (__in_fake_assign)
 310                 return;
 311         if (is_loop_iterator(expr))
 312                 return;
 313
 314         binfo = get_bit_info(expr->right);
 315         if (!binfo)
 316                 return;
 317         if (is_unknown_binfo(get_type(expr->left), binfo))
 318                 return;
 319         set_state_expr(my_id, expr->left, alloc_bstate(binfo->set, binfo->possible));
 320 }
 321
 322 static void match_condition(struct expression *expr)
 323 {
 324         struct bit_info *orig;
 325         struct bit_info true_info;
 326         struct bit_info false_info;
 327         sval_t right;
 328
 329         if (expr->type != EXPR_BINOP ||
 330             expr->op != '&')
 331                 return;
 332
 333         if (!get_value(expr->right, &right))
 334                 return;
 335
 336         orig = get_bit_info(expr->left);
 337         true_info = *orig;
 338         false_info = *orig;
 339
 340         if (right.uvalue == 0 || is_single_bit(right))
 341                 true_info.set &= right.uvalue;
 342
 343         true_info.possible &= right.uvalue;
 344         false_info.possible &= ~right.uvalue;
 345
 346         set_true_false_states_expr(my_id, expr->left,
 347                                    alloc_bstate(true_info.set, true_info.possible),
 348                                    alloc_bstate(false_info.set, false_info.possible));
 349 }
 350
 351 static void match_call_info(struct expression *expr)
 352 {
 353         struct bit_info *binfo, *rl_binfo;
 354         struct expression *arg;
 355         struct range_list *rl;
 356         char buf[64];
 357         int i;
 358
 359         i = -1;
 360         FOR_EACH_PTR(expr->args, arg) {
 361                 i++;
 362                 binfo = get_bit_info(arg);
 363                 if (!binfo)
 364                         continue;
 365                 if (is_unknown_binfo(get_type(arg), binfo))
 366                         continue;
 367                 if (get_implied_rl(arg, &rl)) {
 368                         rl_binfo = rl_to_binfo(rl);
 369                         if (binfo_equiv(rl_binfo, binfo))
 370                                 continue;
 371                 }
 372                 // If is just non-negative continue
 373                 // If ->set == ->possible continue
 374                 snprintf(buf, sizeof(buf), "0x%llx,0x%llx", binfo->set, binfo->possible);
 375                 sql_insert_caller_info(expr, BIT_INFO, i, "$", buf);
 376         } END_FOR_EACH_PTR(arg);
 377 }
 378
 379 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 380 {
 381         struct bit_info *binfo = sm->state->data;
 382         struct smatch_state *estate;
 383         struct bit_info *implied_binfo;
 384         char buf[64];
 385
 386         if (!binfo)
 387                 return;
 388
 389         /* This means it can only be one value, so it's handled by smatch_extra. */
 390         if (binfo->set == binfo->possible)
 391                 return;
 392
 393         estate = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 394         if (is_unknown_binfo(estate_type(estate), binfo))
 395                 return;
 396
 397         if (estate_rl(estate)) {
 398                 sval_t sval;
 399
 400                 if (estate_get_single_value(estate, &sval))
 401                         return;
 402
 403                 implied_binfo = rl_to_binfo(estate_rl(estate));
 404                 if (binfo_equiv(implied_binfo, binfo))
 405                         return;
 406         }
 407
 408         snprintf(buf, sizeof(buf), "0x%llx,0x%llx", binfo->set, binfo->possible);
 409         sql_insert_caller_info(call, BIT_INFO, param, printed_name, buf);
 410 }
 411
 412 static void set_param_bits(const char *name, struct symbol *sym, char *key, char *value)
 413 {
 414         char fullname[256];
 415         unsigned long long set, possible;
 416
 417         if (strcmp(key, "*$") == 0)
 418                 snprintf(fullname, sizeof(fullname), "*%s", name);
 419         else if (strncmp(key, "$", 1) == 0)
 420                 snprintf(fullname, 256, "%s%s", name, key + 1);
 421         else
 422                 return;
 423
 424         set = strtoull(value, &value, 16);
 425         if (*value != ',')
 426                 return;
 427         value++;
 428         possible = strtoull(value, &value, 16);
 429
 430         set_state(my_id, fullname, sym, alloc_bstate(set, possible));
 431 }
 432
 433 void register_bits(int id)
 434 {
 435         my_id = id;
 436
 437         set_dynamic_states(my_id);
 438
 439         add_unmatched_state_hook(my_id, &unmatched_state);
 440         add_merge_hook(my_id, &merge_bstates);
 441
 442         add_hook(&match_condition, CONDITION_HOOK);
 443         add_hook(&match_compare, CONDITION_HOOK);
 444         add_hook(&match_assign, ASSIGNMENT_HOOK);
 445         add_modification_hook(my_id, &match_modify);
 446
 447         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 448         add_member_info_callback(my_id, struct_member_callback);
 449         select_caller_info_hook(set_param_bits, BIT_INFO);
 450 }