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 void match_modify(struct sm_state *sm, struct expression *mod_expr)
 115 {
 116         // FIXME: we really need to store the type
 117
 118         set_state(my_id, sm->name, sm->sym, alloc_bstate(0, -1ULL));
 119 }
 120
 121 static int binfo_equiv(struct bit_info *one, struct bit_info *two)
 122 {
 123         if (one->set == two->set &&
 124             one->possible == two->possible)
 125                 return 1;
 126         return 0;
 127 }
 128
 129 static struct smatch_state *merge_bstates(struct smatch_state *one_state, struct smatch_state *two_state)
 130 {
 131         struct bit_info *one, *two;
 132
 133         one = one_state->data;
 134         two = two_state->data;
 135
 136         if (binfo_equiv(one, two))
 137                 return one_state;
 138
 139         return alloc_bstate(one->set & two->set, one->possible | two->possible);
 140 }
 141
 142 /*
 143  * The combine_bit_info() takes two bit_infos and takes creates the most
 144  * accurate picture we can assuming both are true.  Or it returns unknown if
 145  * the information is logically impossible.
 146  *
 147  * Which means that it takes the | of the ->set bits and the & of the possibly
 148  * set bits, which is the opposite of what merge_bstates() does.
 149  *
 150  */
 151 static struct bit_info *combine_bit_info(struct bit_info *one, struct bit_info *two)
 152 {
 153         struct bit_info *ret = __alloc_bit_info(0);
 154
 155         if ((one->set & two->possible) != one->set)
 156                 return alloc_bit_info(0, -1ULL);
 157         if ((two->set & one->possible) != two->set)
 158                 return alloc_bit_info(0, -1ULL);
 159
 160         ret->set = one->set | two->set;
 161         ret->possible = one->possible & two->possible;
 162
 163         return ret;
 164 }
 165
 166 static struct bit_info *binfo_AND(struct bit_info *left, struct bit_info *right)
 167 {
 168         unsigned long long set = 0;
 169         unsigned long long possible = -1ULL;
 170
 171         if (!left && !right) {
 172                 /* nothing */
 173         } else if (!left) {
 174                 possible = right->possible;
 175         } else if (!right) {
 176                 possible = left->possible;
 177         } else {
 178                 set = left->set & right->set;
 179                 possible = left->possible & right->possible;
 180         }
 181
 182         return alloc_bit_info(set, possible);
 183 }
 184
 185 static struct bit_info *binfo_OR(struct bit_info *left, struct bit_info *right)
 186 {
 187         unsigned long long set = 0;
 188         unsigned long long possible = -1ULL;
 189
 190         if (!left && !right) {
 191                 /* nothing */
 192         } else if (!left) {
 193                 set = right->set;
 194         } else if (!right) {
 195                 set = left->set;
 196         } else {
 197                 set = left->set | right->set;
 198                 possible = left->possible | right->possible;
 199         }
 200
 201         return alloc_bit_info(set, possible);
 202 }
 203
 204 struct bit_info *get_bit_info(struct expression *expr)
 205 {
 206         struct range_list *rl;
 207         struct smatch_state *bstate;
 208         struct bit_info tmp;
 209         struct bit_info *extra_info;
 210         struct bit_info *bit_info;
 211         sval_t known;
 212
 213         expr = strip_parens(expr);
 214
 215         if (get_implied_value(expr, &known))
 216                 return alloc_bit_info(known.value, known.value);
 217
 218         if (expr->type == EXPR_BINOP) {
 219                 if (expr->op == '&')
 220                         return binfo_AND(get_bit_info(expr->left),
 221                                          get_bit_info(expr->right));
 222                 if (expr->op == '|')
 223                         return binfo_OR(get_bit_info(expr->left),
 224                                         get_bit_info(expr->right));
 225         }
 226
 227         if (get_implied_rl(expr, &rl))
 228                 extra_info = rl_to_binfo(rl);
 229         else {
 230                 struct symbol *type;
 231
 232                 tmp = unknown_bit_info;
 233                 extra_info = &tmp;
 234
 235                 type = get_type(expr);
 236                 if (!type)
 237                         type = &ullong_ctype;
 238                 if (type_bits(type) == 64)
 239                         extra_info->possible = -1ULL;
 240                 else
 241                         extra_info->possible = (1ULL << type_bits(type)) - 1;
 242         }
 243
 244         bstate = get_state_expr(my_id, expr);
 245         if (bstate)
 246                 bit_info = bstate->data;
 247         else
 248                 bit_info = (struct bit_info *)&unknown_bit_info;
 249
 250         return combine_bit_info(extra_info, bit_info);
 251 }
 252
 253 static int is_single_bit(sval_t sval)
 254 {
 255         int i;
 256         int count = 0;
 257
 258         for (i = 0; i < 64; i++) {
 259                 if (sval.uvalue & 1ULL << i &&
 260                     count++)
 261                         return 0;
 262         }
 263         if (count == 1)
 264                 return 1;
 265         return 0;
 266 }
 267
 268 static void match_compare(struct expression *expr)
 269 {
 270         sval_t val;
 271
 272         if (expr->type != EXPR_COMPARE)
 273                 return;
 274         if (expr->op != SPECIAL_EQUAL &&
 275             expr->op != SPECIAL_NOTEQUAL)
 276                 return;
 277
 278         if (!get_implied_value(expr->right, &val))
 279                 return;
 280
 281         set_true_false_states_expr(my_id, expr->left,
 282                         (expr->op == SPECIAL_EQUAL) ? alloc_bstate(val.uvalue, val.uvalue) : NULL,
 283                         (expr->op == SPECIAL_EQUAL) ? NULL : alloc_bstate(val.uvalue, val.uvalue));
 284 }
 285
 286 static bool is_loop_iterator(struct expression *expr)
 287 {
 288         struct statement *pre_stmt, *loop_stmt;
 289
 290         pre_stmt = expr_get_parent_stmt(expr);
 291         if (!pre_stmt || pre_stmt->type != STMT_EXPRESSION)
 292                 return false;
 293
 294         loop_stmt = stmt_get_parent_stmt(pre_stmt);
 295         if (!loop_stmt || loop_stmt->type != STMT_ITERATOR)
 296                 return false;
 297         if (loop_stmt->iterator_pre_statement != pre_stmt)
 298                 return false;
 299
 300         return true;
 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 }