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_string_mtag(struct expression *expr, mtag_t *tag)
 117 {
 118         mtag_t xor;
 119
 120         if (expr->type != EXPR_STRING || !expr->string)
 121                 return 0;
 122
 123         /* I was worried about collisions so I added a xor */
 124         xor = str_to_tag("__smatch string");
 125         *tag = str_to_tag(expr->string->data);
 126         *tag = *tag ^ xor;
 127
 128         return 1;
 129 }
 130
 131 int get_toplevel_mtag(struct symbol *sym, mtag_t *tag)
 132 {
 133         char buf[256];
 134
 135         if (!sym)
 136                 return 0;
 137
 138         if (!sym->ident ||
 139             !(sym->ctype.modifiers & MOD_TOPLEVEL))
 140                 return 0;
 141
 142         snprintf(buf, sizeof(buf), "%s %s",
 143                  (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern",
 144                  sym->ident->name);
 145         *tag = str_to_tag(buf);
 146         return 1;
 147 }
 148
 149 int get_deref_mtag(struct expression *expr, mtag_t *tag)
 150 {
 151         mtag_t container_tag, member_tag;
 152         int offset;
 153
 154         /*
 155          * I'm not totally sure what I'm doing...
 156          *
 157          * This is supposed to get something like "global_var->ptr", but I don't
 158          * feel like it's complete at all.
 159          *
 160          */
 161
 162         if (!get_mtag(expr->unop, &container_tag))
 163                 return 0;
 164
 165         offset = get_member_offset_from_deref(expr);
 166         if (offset < 0)
 167                 return 0;
 168
 169         if (!mtag_map_select_tag(container_tag, -offset, &member_tag))
 170                 return 0;
 171
 172         *tag = member_tag;
 173         return 1;
 174 }
 175
 176 static void global_variable(struct symbol *sym)
 177 {
 178         mtag_t tag;
 179
 180         if (!get_toplevel_mtag(sym, &tag))
 181                 return;
 182
 183         sql_insert_mtag_about(tag,
 184                               sym->ident->name,
 185                               (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern");
 186 }
 187
 188 static void db_returns_buf_size(struct expression *expr, int param, char *unused, char *math)
 189 {
 190         struct expression *call;
 191         struct range_list *rl;
 192
 193         if (expr->type != EXPR_ASSIGNMENT)
 194                 return;
 195         call = strip_expr(expr->right);
 196
 197         if (!parse_call_math_rl(call, math, &rl))
 198                 return;
 199 //      rl = cast_rl(&int_ctype, rl);
 200 //      set_state_expr(my_size_id, expr->left, alloc_estate_rl(rl));
 201 }
 202
 203 static void db_returns_memory_tag(struct expression *expr, int param, char *key, char *value)
 204 {
 205         struct expression *call, *arg;
 206         mtag_t tag, alias;
 207         char *name;
 208         struct symbol *sym;
 209
 210         call = strip_expr(expr);
 211         while (call->type == EXPR_ASSIGNMENT)
 212                 call = strip_expr(call->right);
 213         if (call->type != EXPR_CALL)
 214                 return;
 215
 216         tag = strtoul(value, NULL, 10);
 217
 218         if (!create_mtag_alias(tag, call, &alias))
 219                 return;
 220
 221         arg = get_argument_from_call_expr(call->args, param);
 222         if (!arg)
 223                 return;
 224
 225         name = get_variable_from_key(arg, key, &sym);
 226         if (!name || !sym)
 227                 goto free;
 228
 229         set_state(my_id, name, sym, alloc_tag_state(alias));
 230 free:
 231         free_string(name);
 232 }
 233
 234 static void match_call_info(struct expression *expr)
 235 {
 236         struct smatch_state *state;
 237         struct expression *arg;
 238         int i = -1;
 239
 240         FOR_EACH_PTR(expr->args, arg) {
 241                 i++;
 242                 state = get_state_expr(my_id, arg);
 243                 if (!state || !state->data)
 244                         continue;
 245                 sql_insert_caller_info(expr, MEMORY_TAG, i, "$", state->name);
 246         } END_FOR_EACH_PTR(arg);
 247 }
 248
 249 static void save_caller_info(const char *name, struct symbol *sym, char *key, char *value)
 250 {
 251         struct smatch_state *state;
 252         char fullname[256];
 253         mtag_t tag;
 254
 255         if (strncmp(key, "$", 1) != 0)
 256                 return;
 257
 258         tag = atoll(value);
 259         snprintf(fullname, 256, "%s%s", name, key + 1);
 260         state = alloc_tag_state(tag);
 261         set_state(my_id, fullname, sym, state);
 262 }
 263
 264 static int get_array_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 265 {
 266         struct expression *array, *offset_expr;
 267         struct symbol *type;
 268         sval_t sval;
 269
 270         if (!is_array(expr))
 271                 return 0;
 272
 273         array = get_array_base(expr);
 274         if (!array)
 275                 return 0;
 276         type = get_type(array);
 277         if (!type || type->type != SYM_ARRAY)
 278                 return 0;
 279         type = get_real_base_type(type);
 280         if (!type_bytes(type))
 281                 return 0;
 282
 283         if (!get_mtag(array, tag))
 284                 return 0;
 285
 286         offset_expr = get_array_offset(expr);
 287         if (!get_value(offset_expr, &sval))
 288                 return 0;
 289         *offset = sval.value * type_bytes(type);
 290
 291         return 1;
 292 }
 293
 294 static int get_implied_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 295 {
 296         struct smatch_state *state;
 297         struct symbol *type;
 298         sval_t sval;
 299
 300         type = get_type(expr);
 301         if (!type_is_ptr(type))
 302                 return 0;
 303         state = get_extra_state(expr);
 304         if (!state || !estate_get_single_value(state, &sval) || sval.value == 0)
 305                 return 0;
 306
 307         *tag = sval.uvalue & ~MTAG_OFFSET_MASK;
 308         *offset = sval.uvalue & MTAG_OFFSET_MASK;
 309         return 1;
 310 }
 311
 312 static int get_mtag_cnt;
 313 int get_mtag(struct expression *expr, mtag_t *tag)
 314 {
 315         struct smatch_state *state;
 316         int ret = 0;
 317
 318         expr = strip_expr(expr);
 319         if (!expr)
 320                 return 0;
 321
 322         if (get_mtag_cnt > 0)
 323                 return 0;
 324
 325         get_mtag_cnt++;
 326
 327         switch (expr->type) {
 328         case EXPR_STRING:
 329                 if (get_string_mtag(expr, tag)) {
 330                         ret = 1;
 331                         goto dec_cnt;
 332                 }
 333                 break;
 334         case EXPR_SYMBOL:
 335                 if (get_toplevel_mtag(expr->symbol, tag)) {
 336                         ret = 1;
 337                         goto dec_cnt;
 338                 }
 339                 break;
 340         case EXPR_DEREF:
 341                 if (get_deref_mtag(expr, tag)) {
 342                         ret = 1;
 343                         goto dec_cnt;
 344                 }
 345                 break;
 346         }
 347
 348         state = get_state_expr(my_id, expr);
 349         if (!state)
 350                 goto dec_cnt;
 351         if (state->data) {
 352                 *tag = *(mtag_t *)state->data;
 353                 ret = 1;
 354                 goto dec_cnt;
 355         }
 356
 357 dec_cnt:
 358         get_mtag_cnt--;
 359         return ret;
 360 }
 361
 362 int get_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 363 {
 364         int val;
 365
 366         if (!expr)
 367                 return 0;
 368         if (expr->type == EXPR_PREOP && expr->op == '*')
 369                 return get_mtag_offset(expr->unop, tag, offset);
 370         if (get_implied_mtag_offset(expr, tag, offset))
 371                 return 1;
 372         if (!get_mtag(expr, tag))
 373                 return 0;
 374         expr = strip_expr(expr);
 375         if (expr->type == EXPR_SYMBOL) {
 376                 *offset = 0;
 377                 return 1;
 378         }
 379         val = get_member_offset_from_deref(expr);
 380         if (val < 0)
 381                 return 0;
 382         *offset = val;
 383         return 1;
 384 }
 385
 386 int create_mtag_alias(mtag_t tag, struct expression *expr, mtag_t *new)
 387 {
 388         char buf[256];
 389         int lines_from_start;
 390         char *str;
 391
 392         /*
 393          * We need the alias to be unique.  It's not totally required that it
 394          * be the same from one DB build to then next, but it makes debugging
 395          * a bit simpler.
 396          *
 397          */
 398
 399         if (!cur_func_sym)
 400                 return 0;
 401
 402         lines_from_start = expr->pos.line - cur_func_sym->pos.line;
 403         str = expr_to_str(expr);
 404         snprintf(buf, sizeof(buf), "%lld %d %s", tag, lines_from_start, str);
 405         free_string(str);
 406
 407         *new = str_to_tag(buf);
 408         sql_insert_mtag_alias(tag, *new);
 409
 410         return 1;
 411 }
 412
 413 int expr_to_mtag_offset(struct expression *expr, mtag_t *tag, int *offset)
 414 {
 415         *offset = 0;
 416
 417         expr = strip_expr(expr);
 418         if (!expr)
 419                 return 0;
 420
 421         if (is_array(expr))
 422                 return get_array_mtag_offset(expr, tag, offset);
 423
 424         if (expr->type ==  EXPR_DEREF) {
 425                 *offset = get_member_offset_from_deref(expr);
 426                 if (*offset < 0)
 427                         return 0;
 428                 return get_mtag(expr->deref, tag);
 429         }
 430
 431         if (get_implied_mtag_offset(expr, tag, offset))
 432                 return 1;
 433
 434         return get_mtag(expr, tag);
 435 }
 436
 437 int get_mtag_sval(struct expression *expr, sval_t *sval)
 438 {
 439         struct symbol *type;
 440         mtag_t tag;
 441         int offset = 0;
 442
 443         if (bits_in_pointer != 64)
 444                 return 0;
 445
 446         expr = strip_expr(expr);
 447
 448         type = get_type(expr);
 449         if (!type_is_ptr(type))
 450                 return 0;
 451         /*
 452          * There are only three options:
 453          *
 454          * 1) An array address:
 455          *    p = array;
 456          * 2) An address like so:
 457          *    p = &my_struct->member;
 458          * 3) A pointer:
 459          *    p = pointer;
 460          *
 461          */
 462
 463         if (expr->type == EXPR_STRING && get_string_mtag(expr, &tag))
 464                 goto found;
 465
 466         if (type->type == SYM_ARRAY && get_toplevel_mtag(expr->symbol, &tag))
 467                 goto found;
 468
 469         if (get_implied_mtag_offset(expr, &tag, &offset))
 470                 goto found;
 471
 472         if (expr->type != EXPR_PREOP || expr->op != '&')
 473                 return 0;
 474         expr = strip_expr(expr->unop);
 475
 476         if (!expr_to_mtag_offset(expr, &tag, &offset))
 477                 return 0;
 478         if (offset > MTAG_OFFSET_MASK)
 479                 offset = MTAG_OFFSET_MASK;
 480
 481 found:
 482         sval->type = type;
 483         sval->uvalue = tag | offset;
 484
 485         return 1;
 486 }
 487
 488 static struct expression *remove_dereference(struct expression *expr)
 489 {
 490         expr = strip_expr(expr);
 491
 492         if (expr->type == EXPR_PREOP && expr->op == '*')
 493                 return strip_expr(expr->unop);
 494         return preop_expression(expr, '&');
 495 }
 496
 497 int get_mtag_addr_sval(struct expression *expr, sval_t *sval)
 498 {
 499         return get_mtag_sval(remove_dereference(expr), sval);
 500 }
 501
 502 static void print_stored_to_mtag(int return_id, char *return_ranges, struct expression *expr)
 503 {
 504         struct sm_state *sm;
 505         char buf[256];
 506         const char *param_name;
 507         int param;
 508
 509         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 510                 if (!sm->state->data)
 511                         continue;
 512
 513                 param = get_param_num_from_sym(sm->sym);
 514                 if (param < 0)
 515                         continue;
 516                 param_name = get_param_name(sm);
 517                 if (!param_name)
 518                         continue;
 519                 if (strcmp(param_name, "$") == 0)
 520                         continue;
 521
 522                 snprintf(buf, sizeof(buf), "%lld", *(mtag_t *)sm->state->data);
 523                 sql_insert_return_states(return_id, return_ranges, MEMORY_TAG, param, param_name, buf);
 524         } END_FOR_EACH_SM(sm);
 525 }
 526
 527 void register_mtag(int id)
 528 {
 529         my_id = id;
 530
 531
 532         /*
 533          * The mtag stuff only works on 64 systems because we store the
 534          * information in the pointer itself.
 535          * bit 63   : set for alias mtags
 536          * bit 62-12: mtag hash
 537          * bit 11-0 : offset
 538          *
 539          */
 540         if (bits_in_pointer != 64)
 541                 return;
 542
 543         add_hook(&global_variable, BASE_HOOK);
 544
 545         add_function_assign_hook("kmalloc", &alloc_assign, NULL);
 546         add_function_assign_hook("kzalloc", &alloc_assign, NULL);
 547
 548         select_return_states_hook(BUF_SIZE, &db_returns_buf_size);
 549
 550         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 551         select_caller_info_hook(save_caller_info, MEMORY_TAG);
 552         add_split_return_callback(&print_stored_to_mtag);
 553         select_return_states_hook(MEMORY_TAG, db_returns_memory_tag);
 554 }