check_locking.c

   1 /*
   2  * sparse/check_locking.c
   3  *
   4  * Copyright (C) 2009 Dan Carpenter.
   5  *
   6  *  Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * This test checks that locks are held the same across all returns.
  12  *
  13  * Of course, some functions are designed to only hold the locks on success.
  14  * Oh well... We can rewrite it later if we want.
  15  */
  16
  17 #include "parse.h"
  18 #include "smatch.h"
  19 #include "smatch_slist.h"
  20
  21 static const char *lock_funcs[] = {
  22         "_spin_lock",
  23         "_spin_lock_irqsave",
  24         "_spin_lock_irq",
  25         "_spin_lock_bh",
  26         "_spin_lock_nested",
  27         "_spin_lock_irqsave_nested",
  28         "_raw_spin_lock",
  29         "_read_lock",
  30         "_read_lock_irqsave",
  31         "_read_lock_irq",
  32         "_read_lock_bh",
  33         "_write_lock",
  34         "_write_lock_irqsave",
  35         "_write_lock_irq",
  36         "_write_lock_bh",
  37         "down",
  38         "mutex_lock_nested",
  39         "mutex_lock",
  40         NULL,
  41 };
  42
  43 static const char *unlock_funcs[] = {
  44         "_spin_unlock",
  45         "_spin_unlock_irqrestore",
  46         "_spin_unlock_irq",
  47         "_spin_unlock_bh",
  48         "_raw_spin_unlock",
  49         "_read_unlock",
  50         "_read_unlock_irqrestore",
  51         "_read_unlock_irq",
  52         "_read_unlock_bh",
  53         "_write_unlock",
  54         "_write_unlock_irqrestore",
  55         "_write_unlock_irq",
  56         "_write_unlock_bh",
  57         "up",
  58         "mutex_unlock",
  59         NULL,
  60 };
  61
  62 /* These are return 1 if they aquire the lock */
  63 static const char *conditional_funcs[] = {
  64         "_spin_trylock",
  65         "_spin_trylock_bh",
  66         "_read_trylock",
  67         "_write_trylock",
  68         "generic__raw_read_trylock",
  69         "_raw_spin_trylock",
  70         "_raw_read_trylock",
  71         "_raw_write_trylock",
  72         "__raw_spin_trylock",
  73         "__raw_read_trylock",
  74         "__raw_write_trylock",
  75         "__raw_write_trylock",
  76         "mutex_trylock",
  77         NULL,
  78 };
  79
  80 /* These functions return 0 on success */
  81 static const char *reverse_cond_funcs[] = {
  82         "down_trylock",
  83         "down_interruptible",
  84         "mutex_lock_interruptible",
  85         "mutex_lock_interruptible_nested",
  86         "mutex_lock_killable",
  87         "mutex_lock_killable_nested",
  88         NULL,
  89 };
  90
  91 /* todo still need to handle__raw_spin_is_locked */
  92
  93 struct locked_call {
  94         const char *function;
  95         const char *lock;
  96 };
  97
  98 static struct locked_call lock_needed[] = {
  99         {"tty_ldisc_ref_wait", "tty_ldisc_lock"},
 100 };
 101
 102 static int my_id;
 103
 104 static struct tracker_list *starts_locked;
 105 static struct tracker_list *starts_unlocked;
 106
 107 struct locks_on_return {
 108         int line;
 109         struct tracker_list *locked;
 110         struct tracker_list *unlocked;
 111 };
 112 DECLARE_PTR_LIST(return_list, struct locks_on_return);
 113 static struct return_list *all_returns;
 114
 115 STATE(locked);
 116 STATE(start_state);
 117 STATE(unlocked);
 118
 119 static struct smatch_state *get_start_state(struct sm_state *sm)
 120 {
 121        int is_locked = 0;
 122        int is_unlocked = 0;
 123
 124        if (in_tracker_list(starts_locked, sm->name, my_id, sm->sym))
 125                is_locked = 1;
 126        if (in_tracker_list(starts_unlocked, sm->name, my_id, sm->sym))
 127                is_unlocked = 1;
 128        if (is_locked && is_unlocked)
 129                return &undefined;
 130        if (is_locked)
 131                return &locked;
 132        if (is_unlocked)
 133                return &unlocked;
 134         return &undefined;
 135 }
 136
 137 static struct smatch_state *unmatched_state(struct sm_state *sm)
 138 {
 139         return &start_state;
 140 }
 141
 142 static char *get_lock_name(struct expression *expr, void *data)
 143 {
 144         struct expression *lock_expr;
 145
 146         if (data) {
 147                 return alloc_string((char *)data);
 148         } else {
 149                 lock_expr = get_argument_from_call_expr(expr->args, 0);
 150                 return get_variable_from_expr(lock_expr, NULL);
 151         }
 152 }
 153
 154 static void match_lock_func(const char *fn, struct expression *expr, void *data)
 155 {
 156         char *lock_name;
 157         struct sm_state *sm;
 158
 159         lock_name = get_lock_name(expr, data);
 160         if (!lock_name)
 161                 return;
 162         sm = get_sm_state(lock_name, my_id, NULL);
 163         if (!sm)
 164                 add_tracker(&starts_unlocked, lock_name, my_id, NULL);
 165         if (sm && slist_has_state(sm->possible, &locked))
 166                 smatch_msg("error: double lock '%s'", lock_name);
 167         set_state(lock_name, my_id, NULL, &locked);
 168         free_string(lock_name);
 169 }
 170
 171 static void match_unlock_func(const char *fn, struct expression *expr,
 172                               void *data)
 173 {
 174         char *lock_name;
 175         struct sm_state *sm;
 176
 177         lock_name = get_lock_name(expr, data);
 178         if (!lock_name)
 179                 return;
 180         sm = get_sm_state(lock_name, my_id, NULL);
 181         if (!sm)
 182                 add_tracker(&starts_locked, lock_name, my_id, NULL);
 183         if (sm && slist_has_state(sm->possible, &unlocked))
 184                 smatch_msg("error: double unlock '%s'", lock_name);
 185         set_state(lock_name, my_id, NULL, &unlocked);
 186         free_string(lock_name);
 187 }
 188
 189 static void match_lock_needed(const char *fn, struct expression *expr,
 190                               void *data)
 191 {
 192         struct smatch_state *state;
 193         char *fn_name;
 194
 195         state = get_state((char *)data, my_id, NULL);
 196         if (state == &locked)
 197                 return;
 198         fn_name = get_variable_from_expr(expr->fn, NULL);
 199         if (!fn_name) {
 200                 smatch_msg("Internal error.");
 201                 exit(1);
 202         }
 203         smatch_msg("error: %s called without holding '%s' lock", fn_name,
 204                    (char *)data);
 205         free_string(fn_name);
 206 }
 207
 208 static void match_locks_on_zero(const char *fn, struct expression *expr,
 209                                 void *data)
 210 {
 211         char *lock_name;
 212         struct sm_state *sm;
 213
 214         lock_name = get_lock_name(expr, data);
 215         if (!lock_name)
 216                 return;
 217         sm = get_sm_state(lock_name, my_id, NULL);
 218         if (!sm)
 219                 add_tracker(&starts_unlocked, lock_name, my_id, NULL);
 220         set_cond_states(lock_name, my_id, NULL, &unlocked, &locked);
 221         free_string(lock_name);
 222 }
 223
 224 static void match_locks_on_non_zero(const char *fn, struct expression *expr,
 225                                    void *data)
 226 {
 227         char *lock_name;
 228         struct sm_state *sm;
 229
 230         lock_name = get_lock_name(expr, data);
 231         if (!lock_name)
 232                 return;
 233         sm = get_sm_state(lock_name, my_id, NULL);
 234         if (!sm)
 235                 add_tracker(&starts_unlocked, lock_name, my_id, NULL);
 236         set_cond_states(lock_name, my_id, NULL, &locked, &unlocked);
 237         free_string(lock_name);
 238 }
 239
 240 static struct locks_on_return *alloc_return(int line)
 241 {
 242         struct locks_on_return *ret;
 243
 244         ret = malloc(sizeof(*ret));
 245         ret->line = line;
 246         ret->locked = NULL;
 247         ret->unlocked = NULL;
 248         return ret;
 249 }
 250
 251 static void check_possible(struct sm_state *sm)
 252 {
 253         struct sm_state *tmp;
 254         int islocked = 0;
 255         int isunlocked = 0;
 256         int undef = 0;
 257
 258         FOR_EACH_PTR(sm->possible, tmp) {
 259                 if (tmp->state == &locked)
 260                         islocked = 1;
 261                 if (tmp->state == &unlocked)
 262                         isunlocked = 1;
 263                 if (tmp->state == &start_state) {
 264                         struct smatch_state *s;
 265
 266                         s = get_start_state(tmp);
 267                         if (s == &locked)
 268                                 islocked = 1;
 269                         else if (s == &unlocked)
 270                                 isunlocked = 1;
 271                         else
 272                                 undef = 1;
 273                 }
 274                 if (tmp->state == &undefined)
 275                         undef = 1;  // i don't think this is possible any more.
 276         } END_FOR_EACH_PTR(tmp);
 277         if ((islocked && isunlocked) || undef)
 278                 smatch_msg("warn: '%s' is sometimes locked here and "
 279                            "sometimes unlocked.", sm->name);
 280 }
 281
 282 static void match_return(struct statement *stmt)
 283 {
 284         struct locks_on_return *ret;
 285         struct state_list *slist;
 286         struct sm_state *tmp;
 287
 288         ret = alloc_return(get_lineno());
 289
 290         slist = get_all_states(my_id);
 291         FOR_EACH_PTR(slist, tmp) {
 292                 if (tmp->state == &locked) {
 293                         add_tracker(&ret->locked, tmp->name, tmp->owner,
 294                                 tmp->sym);
 295                 } else if (tmp->state == &unlocked) {
 296                         add_tracker(&ret->unlocked, tmp->name, tmp->owner,
 297                                 tmp->sym);
 298                 } else if (tmp->state == &start_state) {
 299                         struct smatch_state *s;
 300
 301                         s = get_start_state(tmp);
 302                         if (s == &locked)
 303                                 add_tracker(&ret->locked, tmp->name, tmp->owner,
 304                                             tmp->sym);
 305                         if (s == &unlocked)
 306                                 add_tracker(&ret->unlocked, tmp->name,
 307                                             tmp->owner, tmp->sym);
 308                 }else {
 309                         check_possible(tmp);
 310                 }
 311         } END_FOR_EACH_PTR(tmp);
 312         free_slist(&slist);
 313         add_ptr_list(&all_returns, ret);
 314 }
 315
 316 static void check_returns_consistently(struct tracker *lock,
 317                                 struct smatch_state *start)
 318 {
 319         int returns_locked = 0;
 320         int returns_unlocked = 0;
 321         struct locks_on_return *tmp;
 322
 323         FOR_EACH_PTR(all_returns, tmp) {
 324                 if (in_tracker_list(tmp->unlocked, lock->name, lock->owner,
 325                                         lock->sym))
 326                         returns_unlocked = tmp->line;
 327                 else if (in_tracker_list(tmp->locked, lock->name, lock->owner,
 328                                                 lock->sym))
 329                         returns_locked = tmp->line;
 330                 else if (start == &locked)
 331                         returns_locked = tmp->line;
 332                 else if (start == &unlocked)
 333                         returns_unlocked = tmp->line;
 334         } END_FOR_EACH_PTR(tmp);
 335
 336         if (returns_locked && returns_unlocked)
 337                 smatch_msg("warn: lock '%s' held on line %d but not on %d.",
 338                         lock->name, returns_locked, returns_unlocked);
 339
 340 }
 341
 342 static void check_consistency(struct symbol *sym)
 343 {
 344         struct tracker *tmp;
 345
 346         if (is_reachable())
 347                 match_return(NULL);
 348
 349         FOR_EACH_PTR(starts_locked, tmp) {
 350                 if (in_tracker_list(starts_unlocked, tmp->name, tmp->owner,
 351                                         tmp->sym))
 352                         smatch_msg("error:  locking inconsistency.  We assume "
 353                                    "'%s' is both locked and unlocked at the "
 354                                    "start.",
 355                                 tmp->name);
 356         } END_FOR_EACH_PTR(tmp);
 357
 358         FOR_EACH_PTR(starts_locked, tmp) {
 359                 check_returns_consistently(tmp, &locked);
 360         } END_FOR_EACH_PTR(tmp);
 361
 362         FOR_EACH_PTR(starts_unlocked, tmp) {
 363                 check_returns_consistently(tmp, &unlocked);
 364         } END_FOR_EACH_PTR(tmp);
 365
 366 }
 367
 368 static void clear_lists(void)
 369 {
 370         struct locks_on_return *tmp;
 371
 372         free_trackers_and_list(&starts_locked);
 373         free_trackers_and_list(&starts_unlocked);
 374
 375         FOR_EACH_PTR(all_returns, tmp) {
 376                 free_trackers_and_list(&tmp->locked);
 377                 free_trackers_and_list(&tmp->unlocked);
 378                 free(tmp);
 379         } END_FOR_EACH_PTR(tmp);
 380         __free_ptr_list((struct ptr_list **)&all_returns);
 381 }
 382
 383 static void match_func_end(struct symbol *sym)
 384 {
 385         check_consistency(sym);
 386         clear_lists();
 387 }
 388
 389 void check_locking(int id)
 390 {
 391         int i;
 392
 393         my_id = id;
 394         add_unmatched_state_hook(my_id, &unmatched_state);
 395         add_hook(&match_return, RETURN_HOOK);
 396         add_hook(&match_func_end, END_FUNC_HOOK);
 397
 398         for (i = 0; lock_funcs[i]; i++) {
 399                 add_function_hook(lock_funcs[i], &match_lock_func, NULL);
 400         }
 401         add_function_hook("lock_kernel", &match_lock_func, (void *)"kernel");
 402         for (i = 0; unlock_funcs[i]; i++) {
 403                 add_function_hook(unlock_funcs[i], &match_unlock_func, NULL);
 404         }
 405         add_function_hook("unlock_kernel", &match_unlock_func, (void *)"kernel");
 406         for (i = 0; i < sizeof(lock_needed)/sizeof(struct locked_call); i++) {
 407                 add_function_hook(lock_needed[i].function, &match_lock_needed,
 408                                   (void *)lock_needed[i].lock);
 409         }
 410
 411         for (i = 0; conditional_funcs[i]; i++) {
 412                 add_conditional_hook(conditional_funcs[i],
 413                                   &match_locks_on_non_zero, NULL);
 414         }
 415
 416         for (i = 0; reverse_cond_funcs[i]; i++) {
 417                 add_conditional_hook(reverse_cond_funcs[i],
 418                                      &match_locks_on_zero, NULL);
 419         }
 420 }