smatch_mtag.c

   1 /*
   2  * Copyright (C) 2017 Oracle.  All rights reserved.
   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  * One problem that I have is that it's really hard to track how pointers are
  20  * passed around.  For example, it would be nice to know that the probe() and
  21  * remove() functions get the same pci_dev pointer.  It would be good to know
  22  * what pointers we're passing to the open() and close() functions.  But that
  23  * information gets lost in a call tree full of function pointer calls.
  24  *
  25  * I think the first step is to start naming specific pointers.  So when a
  26  * pointer is allocated, then it gets a tag.  So calls to kmalloc() generate a
  27  * tag.  But we might not use that, because there might be a better name like
  28  * framebuffer_alloc(). The framebuffer_alloc() is interesting because there is
  29  * one per driver and it's passed around to all the file operations.
  30  *
  31  * Perhaps we could make a list of functions like framebuffer_alloc() which take
  32  * a size and say that those are the interesting alloc functions.
  33  *
  34  * Another place where we would maybe name the pointer is when they are passed
  35  * to the probe().  Because that's an important pointer, since there is one
  36  * per driver (sort of).
  37  *
  38  * My vision is that you could take a pointer and trace it back to a global.  So
  39  * I'm going to track that pointer_tag - 28 bytes takes you to another pointer
  40  * tag.  You could follow that one back and so on.  Also when we pass a pointer
  41  * to a function that would be recorded as sort of a link or path or something.
  42  *
  43  */
  44
  45 #include "smatch.h"
  46 #include "smatch_slist.h"
  47 #include "smatch_extra.h"
  48
  49 #include <openssl/md5.h>
  50
  51 static int my_id;
  52
  53 static struct smatch_state *alloc_tag_state(mtag_t tag)
  54 {
  55         struct smatch_state *state;
  56         char buf[64];
  57
  58         state = __alloc_smatch_state(0);
  59         snprintf(buf, sizeof(buf), "%lld", tag);
  60         state->name = alloc_sname(buf);
  61         state->data = malloc(sizeof(mtag_t));
  62         *(mtag_t *)state->data = tag;
  63
  64         return state;
  65 }
  66
  67 static mtag_t str_to_tag(const char *str)
  68 {
  69         unsigned char c[MD5_DIGEST_LENGTH];
  70         unsigned long long *tag = (unsigned long long *)&c;
  71         MD5_CTX mdContext;
  72         int len;
  73
  74         len = strlen(str);
  75         MD5_Init(&mdContext);
  76         MD5_Update(&mdContext, str, len);
  77         MD5_Final(c, &mdContext);
  78
  79         *tag &= ~MTAG_ALIAS_BIT;
  80         *tag &= ~MTAG_OFFSET_MASK;
  81
  82         return *tag;
  83 }
  84
  85 static void alloc_assign(const char *fn, struct expression *expr, void *unused)
  86 {
  87         struct expression *left, *right;
  88         char *left_name, *right_name;
  89         struct symbol *left_sym;
  90         char buf[256];
  91         mtag_t tag;
  92
  93
  94         // FIXME:  This should only happen when the size is not a paramter of
  95         // the caller
  96         return;
  97
  98         if (expr->type != EXPR_ASSIGNMENT || expr->op != '=')
  99                 return;
 100         left = strip_expr(expr->left);
 101         right = strip_expr(expr->right);
 102         if (right->type != EXPR_CALL || right->fn->type != EXPR_SYMBOL)
 103                 return;
 104
 105         left_name = expr_to_str_sym(left, &left_sym);
 106         right_name = expr_to_str(right);
 107
 108         snprintf(buf, sizeof(buf), "%s %s %s %s", get_filename(), get_function(),
 109                  left_name, right_name);
 110         tag = str_to_tag(buf);
 111
 112         sql_insert_mtag_about(tag, left_name, right_name);
 113
 114         if (left_name && left_sym)
 115                 set_state(my_id, left_name, left_sym, alloc_tag_state(tag));
 116
 117         free_string(left_name);
 118         free_string(right_name);
 119 }
 120
 121 int get_string_mtag(struct expression *expr, mtag_t *tag)
 122 {
 123         mtag_t xor;
 124
 125         if (expr->type != EXPR_STRING || !expr->string)
 126                 return 0;
 127
 128         /* I was worried about collisions so I added a xor */
 129         xor = str_to_tag("__smatch string");
 130         *tag = str_to_tag(expr->string->data);
 131         *tag = *tag ^ xor;
 132
 133         return 1;
 134 }
 135
 136 int get_toplevel_mtag(struct symbol *sym, mtag_t *tag)
 137 {
 138         char buf[256];
 139
 140         if (!sym)
 141                 return 0;
 142
 143         if (!sym->ident ||
 144             !(sym->ctype.modifiers & MOD_TOPLEVEL))
 145                 return 0;
 146
 147         snprintf(buf, sizeof(buf), "%s %s",
 148                  (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern",
 149                  sym->ident->name);
 150         *tag = str_to_tag(buf);
 151         return 1;
 152 }
 153
 154 int get_deref_mtag(struct expression *expr, mtag_t *tag)
 155 {
 156         mtag_t container_tag, member_tag;
 157         int offset;
 158
 159         /*
 160          * I'm not totally sure what I'm doing...
 161          *
 162          * This is supposed to get something like "global_var->ptr", but I don't
 163          * feel like it's complete at all.
 164          *
 165          */
 166
 167         if (!get_mtag(expr->unop, &container_tag))
 168                 return 0;
 169
 170         offset = get_member_offset_from_deref(expr);
 171         if (offset < 0)
 172                 return 0;
 173
 174         if (!mtag_map_select_tag(container_tag, -offset, &member_tag))
 175                 return 0;
 176
 177         *tag = member_tag;
 178         return 1;
 179 }
 180
 181 static void global_variable(struct symbol *sym)
 182 {
 183         mtag_t tag;
 184
 185         if (!get_toplevel_mtag(sym, &tag))
 186                 return;
 187
 188         sql_insert_mtag_about(tag,
 189                               sym->ident->name,
 190                               (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern");
 191 }
 192
 193 static void db_returns_buf_size(struct expression *expr, int param, char *unused, char *math)
 194 {
 195         struct expression *call;
 196         struct range_list *rl;
 197
 198         if (expr->type != EXPR_ASSIGNMENT)
 199                 return;
 200         call = strip_expr(expr->right);
 201
 202         if (!parse_call_math_rl(call, math, &rl))
 203                 return;
 204 //      rl = cast_rl(&int_ctype, rl);
 205 //      set_state_expr(my_size_id, expr->left, alloc_estate_rl(rl));
 206 }
 207
 208 static void db_returns_memory_tag(struct expression *expr, int param, char *key, char *value)
 209 {
 210         struct expression *call, *arg;
 211         mtag_t tag, alias;
 212         char *name;
 213         struct symbol *sym;
 214
 215         call = strip_expr(expr);
 216         while (call->type == EXPR_ASSIGNMENT)
 217                 call = strip_expr(call->right);
 218         if (call->type != EXPR_CALL)
 219                 return;
 220
 221         tag = strtoul(value, NULL, 10);
 222
 223         if (!create_mtag_alias(tag, call, &alias))
 224                 return;
 225
 226         arg = get_argument_from_call_expr(call->args, param);
 227         if (!arg)
 228                 return;
 229
 230         name = get_variable_from_key(arg, key, &sym);
 231         if (!name || !sym)
 232                 goto free;
 233
 234         set_state(my_id, name, sym, alloc_tag_state(alias));
 235 free:
 236         free_string(name);
 237 }
 238
 239 static void match_call_info(struct expression *expr)
 240 {
 241         struct smatch_state *state;
 242         struct expression *arg;
 243         int i = -1;
 244
 245         FOR_EACH_PTR(expr->args, arg) {
 246                 i++;
 247                 state = get_state_expr(my_id, arg);
 248                 if (!state || !state->data)
 249                         continue;
 250                 sql_insert_caller_info(expr, MEMORY_TAG, i, "$", state->name);
 251         } END_FOR_EACH_PTR(arg);
 252 }
 253
 254 static void save_caller_info(const char *name, struct symbol *sym, char *key, char *value)
 255 {
 256         struct smatch_state *state;
 257         char fullname[256];
 258         mtag_t tag;
 259
 260         if (strncmp(key, "$", 1) != 0)
 261                 return;
 262
 263         tag = atoll(value);
 264         snprintf(fullname, 256, "%s%s", name, key + 1);
 265         state = alloc_tag_state(tag);
 266         set_state(my_id, fullname, sym, state);
 267 }
 268
 269 static int get_array_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 270 {
 271         struct expression *array, *offset_expr;
 272         struct symbol *type;
 273         sval_t sval;
 274
 275         if (!is_array(expr))
 276                 return 0;
 277
 278         array = get_array_base(expr);
 279         if (!array)
 280                 return 0;
 281         type = get_type(array);
 282         if (!type || type->type != SYM_ARRAY)
 283                 return 0;
 284         type = get_real_base_type(type);
 285         if (!type_bytes(type))
 286                 return 0;
 287
 288         if (!get_mtag(array, tag))
 289                 return 0;
 290
 291         offset_expr = get_array_offset(expr);
 292         if (!get_value(offset_expr, &sval))
 293                 return 0;
 294         *offset = sval.value * type_bytes(type);
 295
 296         return 1;
 297 }
 298
 299 static int get_implied_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 300 {
 301         struct smatch_state *state;
 302         struct symbol *type;
 303         sval_t sval;
 304
 305         type = get_type(expr);
 306         if (!type_is_ptr(type))
 307                 return 0;
 308         state = get_extra_state(expr);
 309         if (!state || !estate_get_single_value(state, &sval) || sval.value == 0)
 310                 return 0;
 311
 312         *tag = sval.uvalue & ~MTAG_OFFSET_MASK;
 313         *offset = sval.uvalue & MTAG_OFFSET_MASK;
 314         return 1;
 315 }
 316
 317 static int get_mtag_cnt;
 318 int get_mtag(struct expression *expr, mtag_t *tag)
 319 {
 320         struct smatch_state *state;
 321         int ret = 0;
 322
 323         expr = strip_expr(expr);
 324         if (!expr)
 325                 return 0;
 326
 327         if (get_mtag_cnt > 0)
 328                 return 0;
 329
 330         get_mtag_cnt++;
 331
 332         switch (expr->type) {
 333         case EXPR_STRING:
 334                 if (get_string_mtag(expr, tag)) {
 335                         ret = 1;
 336                         goto dec_cnt;
 337                 }
 338                 break;
 339         case EXPR_SYMBOL:
 340                 if (get_toplevel_mtag(expr->symbol, tag)) {
 341                         ret = 1;
 342                         goto dec_cnt;
 343                 }
 344                 break;
 345         case EXPR_DEREF:
 346                 if (get_deref_mtag(expr, tag)) {
 347                         ret = 1;
 348                         goto dec_cnt;
 349                 }
 350                 break;
 351         }
 352
 353         state = get_state_expr(my_id, expr);
 354         if (!state)
 355                 goto dec_cnt;
 356         if (state->data) {
 357                 *tag = *(mtag_t *)state->data;
 358                 ret = 1;
 359                 goto dec_cnt;
 360         }
 361
 362 dec_cnt:
 363         get_mtag_cnt--;
 364         return ret;
 365 }
 366
 367 int get_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 368 {
 369         int val;
 370
 371         if (!expr)
 372                 return 0;
 373         if (expr->type == EXPR_PREOP && expr->op == '*')
 374                 return get_mtag_offset(expr->unop, tag, offset);
 375         if (get_implied_mtag_offset(expr, tag, offset))
 376                 return 1;
 377         if (!get_mtag(expr, tag))
 378                 return 0;
 379         expr = strip_expr(expr);
 380         if (expr->type == EXPR_SYMBOL) {
 381                 *offset = 0;
 382                 return 1;
 383         }
 384         val = get_member_offset_from_deref(expr);
 385         if (val < 0)
 386                 return 0;
 387         *offset = val;
 388         return 1;
 389 }
 390
 391 int create_mtag_alias(mtag_t tag, struct expression *expr, mtag_t *new)
 392 {
 393         char buf[256];
 394         int lines_from_start;
 395         char *str;
 396
 397         /*
 398          * We need the alias to be unique.  It's not totally required that it
 399          * be the same from one DB build to then next, but it makes debugging
 400          * a bit simpler.
 401          *
 402          */
 403
 404         if (!cur_func_sym)
 405                 return 0;
 406
 407         lines_from_start = expr->pos.line - cur_func_sym->pos.line;
 408         str = expr_to_str(expr);
 409         snprintf(buf, sizeof(buf), "%lld %d %s", tag, lines_from_start, str);
 410         free_string(str);
 411
 412         *new = str_to_tag(buf);
 413         sql_insert_mtag_alias(tag, *new);
 414
 415         return 1;
 416 }
 417
 418 int expr_to_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 419 {
 420         *offset = 0;
 421
 422         expr = strip_expr(expr);
 423         if (!expr)
 424                 return 0;
 425
 426         if (is_array(expr))
 427                 return get_array_mtag_offset(expr, tag, offset);
 428
 429         if (expr->type ==  EXPR_DEREF) {
 430                 *offset = get_member_offset_from_deref(expr);
 431                 if (*offset < 0)
 432                         return 0;
 433                 return get_mtag(expr->deref, tag);
 434         }
 435
 436         if (get_implied_mtag_offset(expr, tag, offset))
 437                 return 1;
 438
 439         return get_mtag(expr, tag);
 440 }
 441
 442 int get_mtag_sval(struct expression *expr, sval_t *sval)
 443 {
 444         struct symbol *type;
 445         mtag_t tag;
 446         int offset = 0;
 447
 448         if (bits_in_pointer != 64)
 449                 return 0;
 450
 451         expr = strip_expr(expr);
 452
 453         type = get_type(expr);
 454         if (!type_is_ptr(type))
 455                 return 0;
 456         /*
 457          * There are only three options:
 458          *
 459          * 1) An array address:
 460          *    p = array;
 461          * 2) An address like so:
 462          *    p = &my_struct->member;
 463          * 3) A pointer:
 464          *    p = pointer;
 465          *
 466          */
 467
 468         if (expr->type == EXPR_STRING && get_string_mtag(expr, &tag))
 469                 goto found;
 470
 471         if (type->type == SYM_ARRAY && get_toplevel_mtag(expr->symbol, &tag))
 472                 goto found;
 473
 474         if (get_implied_mtag_offset(expr, &tag, &offset))
 475                 goto found;
 476
 477         if (expr->type != EXPR_PREOP || expr->op != '&')
 478                 return 0;
 479         expr = strip_expr(expr->unop);
 480
 481         if (!expr_to_mtag_offset(expr, &tag, &offset))
 482                 return 0;
 483         if (offset > MTAG_OFFSET_MASK)
 484                 offset = MTAG_OFFSET_MASK;
 485
 486 found:
 487         sval->type = type;
 488         sval->uvalue = tag | offset;
 489
 490         return 1;
 491 }
 492
 493 static struct expression *remove_dereference(struct expression *expr)
 494 {
 495         expr = strip_expr(expr);
 496
 497         if (expr->type == EXPR_PREOP && expr->op == '*')
 498                 return strip_expr(expr->unop);
 499         return preop_expression(expr, '&');
 500 }
 501
 502 int get_mtag_addr_sval(struct expression *expr, sval_t *sval)
 503 {
 504         return get_mtag_sval(remove_dereference(expr), sval);
 505 }
 506
 507 static void print_stored_to_mtag(int return_id, char *return_ranges, struct expression *expr)
 508 {
 509         struct sm_state *sm;
 510         char buf[256];
 511         const char *param_name;
 512         int param;
 513
 514         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 515                 if (!sm->state->data)
 516                         continue;
 517
 518                 param = get_param_num_from_sym(sm->sym);
 519                 if (param < 0)
 520                         continue;
 521                 param_name = get_param_name(sm);
 522                 if (!param_name)
 523                         continue;
 524                 if (strcmp(param_name, "$") == 0)
 525                         continue;
 526
 527                 snprintf(buf, sizeof(buf), "%lld", *(mtag_t *)sm->state->data);
 528                 sql_insert_return_states(return_id, return_ranges, MEMORY_TAG, param, param_name, buf);
 529         } END_FOR_EACH_SM(sm);
 530 }
 531
 532 void register_mtag(int id)
 533 {
 534         my_id = id;
 535
 536
 537         /*
 538          * The mtag stuff only works on 64 systems because we store the
 539          * information in the pointer itself.
 540          * bit 63   : set for alias mtags
 541          * bit 62-12: mtag hash
 542          * bit 11-0 : offset
 543          *
 544          */
 545         if (bits_in_pointer != 64)
 546                 return;
 547
 548         add_hook(&global_variable, BASE_HOOK);
 549
 550         add_function_assign_hook("kmalloc", &alloc_assign, NULL);
 551         add_function_assign_hook("kzalloc", &alloc_assign, NULL);
 552
 553         select_return_states_hook(BUF_SIZE, &db_returns_buf_size);
 554
 555         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 556         select_caller_info_hook(save_caller_info, MEMORY_TAG);
 557         add_split_return_callback(&print_stored_to_mtag);
 558         select_return_states_hook(MEMORY_TAG, db_returns_memory_tag);
 559 }