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         if (expr->type != EXPR_ASSIGNMENT || expr->op != '=')
  94                 return;
  95         left = strip_expr(expr->left);
  96         right = strip_expr(expr->right);
  97         if (right->type != EXPR_CALL || right->fn->type != EXPR_SYMBOL)
  98                 return;
  99
 100         left_name = expr_to_str_sym(left, &left_sym);
 101         right_name = expr_to_str(right);
 102
 103         snprintf(buf, sizeof(buf), "%s %s %s %s", get_filename(), get_function(),
 104                  left_name, right_name);
 105         tag = str_to_tag(buf);
 106
 107         sql_insert_mtag_about(tag, left_name, right_name);
 108
 109         if (left_name && left_sym)
 110                 set_state(my_id, left_name, left_sym, alloc_tag_state(tag));
 111
 112         free_string(left_name);
 113         free_string(right_name);
 114 }
 115
 116 int get_toplevel_mtag(struct symbol *sym, mtag_t *tag)
 117 {
 118         char buf[256];
 119
 120         if (!sym)
 121                 return 0;
 122
 123         if (!sym->ident ||
 124             !(sym->ctype.modifiers & MOD_TOPLEVEL))
 125                 return 0;
 126
 127         snprintf(buf, sizeof(buf), "%s %s",
 128                  (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern",
 129                  sym->ident->name);
 130         *tag = str_to_tag(buf);
 131         return 1;
 132 }
 133
 134 int get_deref_mtag(struct expression *expr, mtag_t *tag)
 135 {
 136         mtag_t container_tag, member_tag;
 137         int offset;
 138
 139         /*
 140          * I'm not totally sure what I'm doing...
 141          *
 142          * This is supposed to get something like "global_var->ptr", but I don't
 143          * feel like it's complete at all.
 144          *
 145          */
 146
 147         if (!get_mtag(expr->unop, &container_tag))
 148                 return 0;
 149
 150         offset = get_member_offset_from_deref(expr);
 151         if (offset < 0)
 152                 return 0;
 153
 154         if (!mtag_map_select_tag(container_tag, -offset, &member_tag))
 155                 return 0;
 156
 157         *tag = member_tag;
 158         return 1;
 159 }
 160
 161 static void global_variable(struct symbol *sym)
 162 {
 163         mtag_t tag;
 164
 165         if (!get_toplevel_mtag(sym, &tag))
 166                 return;
 167
 168         sql_insert_mtag_about(tag,
 169                               sym->ident->name,
 170                               (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern");
 171 }
 172
 173 static void db_returns_buf_size(struct expression *expr, int param, char *unused, char *math)
 174 {
 175         struct expression *call;
 176         struct range_list *rl;
 177
 178         if (expr->type != EXPR_ASSIGNMENT)
 179                 return;
 180         call = strip_expr(expr->right);
 181
 182         if (!parse_call_math_rl(call, math, &rl))
 183                 return;
 184 //      rl = cast_rl(&int_ctype, rl);
 185 //      set_state_expr(my_size_id, expr->left, alloc_estate_rl(rl));
 186 }
 187
 188 static void db_returns_memory_tag(struct expression *expr, int param, char *key, char *value)
 189 {
 190         struct expression *call, *arg;
 191         mtag_t tag, alias;
 192         char *name;
 193         struct symbol *sym;
 194
 195         call = strip_expr(expr);
 196         while (call->type == EXPR_ASSIGNMENT)
 197                 call = strip_expr(call->right);
 198         if (call->type != EXPR_CALL)
 199                 return;
 200
 201         tag = strtoul(value, NULL, 10);
 202
 203         if (!create_mtag_alias(tag, call, &alias))
 204                 return;
 205
 206         arg = get_argument_from_call_expr(call->args, param);
 207         if (!arg)
 208                 return;
 209
 210         name = get_variable_from_key(arg, key, &sym);
 211         if (!name || !sym)
 212                 goto free;
 213
 214         set_state(my_id, name, sym, alloc_tag_state(alias));
 215 free:
 216         free_string(name);
 217 }
 218
 219 static void match_call_info(struct expression *expr)
 220 {
 221         struct smatch_state *state;
 222         struct expression *arg;
 223         int i = -1;
 224
 225         FOR_EACH_PTR(expr->args, arg) {
 226                 i++;
 227                 state = get_state_expr(my_id, arg);
 228                 if (!state || !state->data)
 229                         continue;
 230                 sql_insert_caller_info(expr, MEMORY_TAG, i, "$", state->name);
 231         } END_FOR_EACH_PTR(arg);
 232 }
 233
 234 static void save_caller_info(const char *name, struct symbol *sym, char *key, char *value)
 235 {
 236         struct smatch_state *state;
 237         char fullname[256];
 238         mtag_t tag;
 239
 240         if (strncmp(key, "$", 1) != 0)
 241                 return;
 242
 243         tag = atoll(value);
 244         snprintf(fullname, 256, "%s%s", name, key + 1);
 245         state = alloc_tag_state(tag);
 246         set_state(my_id, fullname, sym, state);
 247 }
 248
 249 static int get_array_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 250 {
 251         struct expression *array, *offset_expr;
 252         struct symbol *type;
 253         sval_t sval;
 254
 255         if (!is_array(expr))
 256                 return 0;
 257
 258         array = get_array_base(expr);
 259         if (!array)
 260                 return 0;
 261         type = get_type(array);
 262         if (!type || type->type != SYM_ARRAY)
 263                 return 0;
 264         type = get_real_base_type(type);
 265         if (!type_bytes(type))
 266                 return 0;
 267
 268         if (!get_mtag(array, tag))
 269                 return 0;
 270
 271         offset_expr = get_array_offset(expr);
 272         if (!get_value(offset_expr, &sval))
 273                 return 0;
 274         *offset = sval.value * type_bytes(type);
 275
 276         return 1;
 277 }
 278
 279 static int get_implied_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 280 {
 281         struct smatch_state *state;
 282         struct symbol *type;
 283         sval_t sval;
 284
 285         type = get_type(expr);
 286         if (!type_is_ptr(type))
 287                 return 0;
 288         state = get_extra_state(expr);
 289         if (!state || !estate_get_single_value(state, &sval))
 290                 return 0;
 291
 292         *tag = sval.uvalue & ~MTAG_OFFSET_MASK;
 293         *offset = sval.uvalue & MTAG_OFFSET_MASK;
 294         return 1;
 295 }
 296
 297 static int get_mtag_cnt;
 298 int get_mtag(struct expression *expr, mtag_t *tag)
 299 {
 300         struct smatch_state *state;
 301         int ret = 0;
 302
 303         expr = strip_expr(expr);
 304         if (!expr)
 305                 return 0;
 306
 307         if (get_mtag_cnt > 0)
 308                 return 0;
 309
 310         get_mtag_cnt++;
 311
 312         switch (expr->type) {
 313         case EXPR_SYMBOL:
 314                 if (get_toplevel_mtag(expr->symbol, tag)) {
 315                         ret = 1;
 316                         goto dec_cnt;
 317                 }
 318                 break;
 319         case EXPR_DEREF:
 320                 if (get_deref_mtag(expr, tag)) {
 321                         ret = 1;
 322                         goto dec_cnt;
 323                 }
 324                 break;
 325         }
 326
 327         state = get_state_expr(my_id, expr);
 328         if (!state)
 329                 goto dec_cnt;
 330         if (state->data) {
 331                 *tag = *(mtag_t *)state->data;
 332                 ret = 1;
 333                 goto dec_cnt;
 334         }
 335
 336 dec_cnt:
 337         get_mtag_cnt--;
 338         return ret;
 339 }
 340
 341 int get_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 342 {
 343         int val;
 344
 345         if (!expr)
 346                 return 0;
 347         if (expr->type == EXPR_PREOP && expr->op == '*')
 348                 return get_mtag_offset(expr->unop, tag, offset);
 349         if (get_implied_mtag_offset(expr, tag, offset))
 350                 return 1;
 351         if (!get_mtag(expr, tag))
 352                 return 0;
 353         expr = strip_expr(expr);
 354         if (expr->type == EXPR_SYMBOL) {
 355                 *offset = 0;
 356                 return 1;
 357         }
 358         val = get_member_offset_from_deref(expr);
 359         if (val < 0)
 360                 return 0;
 361         *offset = val;
 362         return 1;
 363 }
 364
 365 int create_mtag_alias(mtag_t tag, struct expression *expr, mtag_t *new)
 366 {
 367         char buf[256];
 368         int lines_from_start;
 369         char *str;
 370
 371         /*
 372          * We need the alias to be unique.  It's not totally required that it
 373          * be the same from one DB build to then next, but it makes debugging
 374          * a bit simpler.
 375          *
 376          */
 377
 378         if (!cur_func_sym)
 379                 return 0;
 380
 381         lines_from_start = expr->pos.line - cur_func_sym->pos.line;
 382         str = expr_to_str(expr);
 383         snprintf(buf, sizeof(buf), "%lld %d %s", tag, lines_from_start, str);
 384         free_string(str);
 385
 386         *new = str_to_tag(buf);
 387         sql_insert_mtag_alias(tag, *new);
 388
 389         return 1;
 390 }
 391
 392 int expr_to_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 393 {
 394         *offset = 0;
 395
 396         expr = strip_expr(expr);
 397         if (!expr)
 398                 return 0;
 399
 400         if (get_implied_mtag_offset(expr, tag, offset))
 401                 return 1;
 402
 403         if (is_array(expr))
 404                 return get_array_mtag_offset(expr, tag, offset);
 405
 406         if (expr->type ==  EXPR_DEREF) {
 407                 *offset = get_member_offset_from_deref(expr);
 408                 if (*offset < 0)
 409                         return 0;
 410                 return get_mtag(expr->deref, tag);
 411         }
 412
 413         return get_mtag(expr, tag);
 414 }
 415
 416 int get_mtag_sval(struct expression *expr, sval_t *sval)
 417 {
 418         struct symbol *type;
 419         mtag_t tag;
 420         int offset = 0;
 421
 422         if (bits_in_pointer != 64)
 423                 return 0;
 424
 425         expr = strip_expr(expr);
 426
 427         type = get_type(expr);
 428         if (!type_is_ptr(type))
 429                 return 0;
 430         /*
 431          * There are only three options:
 432          *
 433          * 1) An array address:
 434          *    p = array;
 435          * 2) An address like so:
 436          *    p = &my_struct->member;
 437          * 3) A pointer:
 438          *    p = pointer;
 439          *
 440          */
 441
 442         if (type->type == SYM_ARRAY && get_toplevel_mtag(expr->symbol, &tag))
 443                 goto found;
 444
 445         if (get_implied_mtag_offset(expr, &tag, &offset))
 446                 goto found;
 447
 448         if (expr->type != EXPR_PREOP || expr->op != '&')
 449                 return 0;
 450         expr = strip_expr(expr->unop);
 451
 452         if (!expr_to_mtag_offset(expr, &tag, &offset))
 453                 return 0;
 454         if (offset > MTAG_OFFSET_MASK)
 455                 offset = MTAG_OFFSET_MASK;
 456
 457 found:
 458         sval->type = type;
 459         sval->uvalue = tag | offset;
 460
 461         return 1;
 462 }
 463
 464 static struct expression *remove_dereference(struct expression *expr)
 465 {
 466         expr = strip_expr(expr);
 467
 468         if (expr->type == EXPR_PREOP && expr->op == '*')
 469                 return strip_expr(expr->unop);
 470         return preop_expression(expr, '&');
 471 }
 472
 473 int get_mtag_addr_sval(struct expression *expr, sval_t *sval)
 474 {
 475         return get_mtag_sval(remove_dereference(expr), sval);
 476 }
 477
 478 static void print_stored_to_mtag(int return_id, char *return_ranges, struct expression *expr)
 479 {
 480         struct sm_state *sm;
 481         char buf[256];
 482         const char *param_name;
 483         int param;
 484
 485         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 486                 if (!sm->state->data)
 487                         continue;
 488
 489                 param = get_param_num_from_sym(sm->sym);
 490                 if (param < 0)
 491                         continue;
 492                 param_name = get_param_name(sm);
 493                 if (!param_name)
 494                         continue;
 495                 if (strcmp(param_name, "$") == 0)
 496                         continue;
 497
 498                 snprintf(buf, sizeof(buf), "%lld", *(mtag_t *)sm->state->data);
 499                 sql_insert_return_states(return_id, return_ranges, MEMORY_TAG, param, param_name, buf);
 500         } END_FOR_EACH_SM(sm);
 501 }
 502
 503 void register_mtag(int id)
 504 {
 505         my_id = id;
 506
 507
 508         /*
 509          * The mtag stuff only works on 64 systems because we store the
 510          * information in the pointer itself.
 511          * bit 63   : set for alias mtags
 512          * bit 62-12: mtag hash
 513          * bit 11-0 : offset
 514          *
 515          */
 516         if (bits_in_pointer != 64)
 517                 return;
 518
 519         add_hook(&global_variable, BASE_HOOK);
 520
 521         add_function_assign_hook("kmalloc", &alloc_assign, NULL);
 522         add_function_assign_hook("kzalloc", &alloc_assign, NULL);
 523
 524         select_return_states_hook(BUF_SIZE, &db_returns_buf_size);
 525
 526         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 527         select_caller_info_hook(save_caller_info, MEMORY_TAG);
 528         add_split_return_callback(&print_stored_to_mtag);
 529         select_return_states_hook(MEMORY_TAG, db_returns_memory_tag);
 530 }