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 *match_func(const char *list[], char *fn_name,
 143                         struct expression_list *args)
 144 {
 145         struct expression *lock_expr;
 146         int i;
 147
 148         for (i = 0; list[i]; i++) {
 149                 if (!strcmp(fn_name, list[i])) {
 150                         lock_expr = get_argument_from_call_expr(args, 0);
 151                         return get_variable_from_expr(lock_expr, NULL);
 152                 }
 153         }
 154         return NULL;
 155 }
 156
 157 static char kernel[] = "kernel";
 158 static char *match_lock_func(char *fn_name, struct expression_list *args)
 159 {
 160         char *arg;
 161
 162         arg = match_func(lock_funcs, fn_name, args);
 163         if (arg)
 164                 return arg;
 165         if (!strcmp(fn_name, "lock_kernel"))
 166                 return alloc_string(kernel);
 167         return NULL;
 168 }
 169
 170 static char *match_unlock_func(char *fn_name, struct expression_list *args)
 171 {
 172         char *arg;
 173
 174         arg = match_func(unlock_funcs, fn_name, args);
 175         if (arg)
 176                 return arg;
 177         if (!strcmp(fn_name, "unlock_kernel"))
 178                 return alloc_string(kernel);
 179         return NULL;
 180 }
 181
 182 static void check_locks_needed(const char *fn_name)
 183 {
 184         struct smatch_state *state;
 185         int i;
 186
 187         for (i = 0; i < sizeof(lock_needed)/sizeof(struct locked_call); i++) {
 188                 if (!strcmp(fn_name, lock_needed[i].function)) {
 189                         state = get_state(lock_needed[i].lock, my_id, NULL);
 190                         if (state != &locked) {
 191                                 smatch_msg("error: %s called without holding '%s' lock",
 192                                         lock_needed[i].function,
 193                                         lock_needed[i].lock);
 194                         }
 195                 }
 196         }
 197 }
 198
 199 static void match_call(struct expression *expr)
 200 {
 201         char *fn_name;
 202         char *lock_name;
 203         struct sm_state *sm;
 204
 205         fn_name = get_variable_from_expr(expr->fn, NULL);
 206         if (!fn_name)
 207                 return;
 208
 209         if ((lock_name = match_lock_func(fn_name, expr->args))) {
 210                 sm = get_sm_state(lock_name, my_id, NULL);
 211                 if (!sm)
 212                         add_tracker(&starts_unlocked, lock_name, my_id, NULL);
 213                 if (sm && slist_has_state(sm->possible, &locked))
 214                         smatch_msg("error: double lock '%s'", lock_name);
 215                 set_state(lock_name, my_id, NULL, &locked);
 216         } else if ((lock_name = match_unlock_func(fn_name, expr->args))) {
 217                 sm = get_sm_state(lock_name, my_id, NULL);
 218                 if (!sm)
 219                         add_tracker(&starts_locked, lock_name, my_id, NULL);
 220                 if (sm && slist_has_state(sm->possible, &unlocked))
 221                         smatch_msg("error: double unlock '%s'", lock_name);
 222                 set_state(lock_name, my_id, NULL, &unlocked);
 223         } else
 224                 check_locks_needed(fn_name);
 225         free_string(lock_name);
 226         free_string(fn_name);
 227         return;
 228 }
 229
 230 static void match_condition(struct expression *expr)
 231 {
 232         char *fn_name;
 233         char *lock_name;
 234
 235         if (expr->type != EXPR_CALL)
 236                 return;
 237
 238         fn_name = get_variable_from_expr(expr->fn, NULL);
 239         if (!fn_name)
 240                 return;
 241
 242         if ((lock_name = match_func(conditional_funcs, fn_name, expr->args))) {
 243                 if (!get_state(lock_name, my_id, NULL))
 244                         add_tracker(&starts_unlocked, lock_name, my_id, NULL);
 245                 set_true_false_states(lock_name, my_id, NULL, &locked, &unlocked);
 246         }
 247         if ((lock_name = match_func(reverse_cond_funcs, fn_name, expr->args))) {
 248                 if (!get_state(lock_name, my_id, NULL))
 249                         add_tracker(&starts_unlocked, lock_name, my_id, NULL);
 250                 set_true_false_states(lock_name, my_id, NULL, &unlocked, &locked);
 251         }
 252         free_string(lock_name);
 253         free_string(fn_name);
 254         return;
 255 }
 256
 257 static struct locks_on_return *alloc_return(int line)
 258 {
 259         struct locks_on_return *ret;
 260
 261         ret = malloc(sizeof(*ret));
 262         ret->line = line;
 263         ret->locked = NULL;
 264         ret->unlocked = NULL;
 265         return ret;
 266 }
 267
 268 static void check_possible(struct sm_state *sm)
 269 {
 270         struct sm_state *tmp;
 271         int islocked = 0;
 272         int isunlocked = 0;
 273         int undef = 0;
 274
 275         FOR_EACH_PTR(sm->possible, tmp) {
 276                 if (tmp->state == &locked)
 277                         islocked = 1;
 278                 if (tmp->state == &unlocked)
 279                         isunlocked = 1;
 280                 if (tmp->state == &start_state) {
 281                         struct smatch_state *s;
 282
 283                         s = get_start_state(tmp);
 284                         if (s == &locked)
 285                                 islocked = 1;
 286                         else if (s == &unlocked)
 287                                 isunlocked = 1;
 288                         else
 289                                 undef = 1;
 290                 }
 291                 if (tmp->state == &undefined)
 292                         undef = 1;  // i don't think this is possible any more.
 293         } END_FOR_EACH_PTR(tmp);
 294         if ((islocked && isunlocked) || undef)
 295                 smatch_msg("warn: '%s' is sometimes locked here and "
 296                            "sometimes unlocked.", sm->name);
 297 }
 298
 299 static void match_return(struct statement *stmt)
 300 {
 301         struct locks_on_return *ret;
 302         struct state_list *slist;
 303         struct sm_state *tmp;
 304
 305         ret = alloc_return(get_lineno());
 306
 307         slist = get_all_states(my_id);
 308         FOR_EACH_PTR(slist, tmp) {
 309                 if (tmp->state == &locked) {
 310                         add_tracker(&ret->locked, tmp->name, tmp->owner,
 311                                 tmp->sym);
 312                 } else if (tmp->state == &unlocked) {
 313                         add_tracker(&ret->unlocked, tmp->name, tmp->owner,
 314                                 tmp->sym);
 315                 } else if (tmp->state == &start_state) {
 316                         struct smatch_state *s;
 317
 318                         s = get_start_state(tmp);
 319                         if (s == &locked)
 320                                 add_tracker(&ret->locked, tmp->name, tmp->owner,
 321                                             tmp->sym);
 322                         if (s == &unlocked)
 323                                 add_tracker(&ret->unlocked, tmp->name,
 324                                             tmp->owner, tmp->sym);
 325                 }else {
 326                         check_possible(tmp);
 327                 }
 328         } END_FOR_EACH_PTR(tmp);
 329         free_slist(&slist);
 330         add_ptr_list(&all_returns, ret);
 331 }
 332
 333 static void check_returns_consistently(struct tracker *lock,
 334                                 struct smatch_state *start)
 335 {
 336         int returns_locked = 0;
 337         int returns_unlocked = 0;
 338         struct locks_on_return *tmp;
 339
 340         FOR_EACH_PTR(all_returns, tmp) {
 341                 if (in_tracker_list(tmp->unlocked, lock->name, lock->owner,
 342                                         lock->sym))
 343                         returns_unlocked = tmp->line;
 344                 else if (in_tracker_list(tmp->locked, lock->name, lock->owner,
 345                                                 lock->sym))
 346                         returns_locked = tmp->line;
 347                 else if (start == &locked)
 348                         returns_locked = tmp->line;
 349                 else if (start == &unlocked)
 350                         returns_unlocked = tmp->line;
 351         } END_FOR_EACH_PTR(tmp);
 352
 353         if (returns_locked && returns_unlocked)
 354                 smatch_msg("warn: lock '%s' held on line %d but not on %d.",
 355                         lock->name, returns_locked, returns_unlocked);
 356
 357 }
 358
 359 static void check_consistency(struct symbol *sym)
 360 {
 361         struct tracker *tmp;
 362
 363         if (is_reachable())
 364                 match_return(NULL);
 365
 366         FOR_EACH_PTR(starts_locked, tmp) {
 367                 if (in_tracker_list(starts_unlocked, tmp->name, tmp->owner,
 368                                         tmp->sym))
 369                         smatch_msg("error:  locking inconsistency.  We assume "
 370                                    "'%s' is both locked and unlocked at the "
 371                                    "start.",
 372                                 tmp->name);
 373         } END_FOR_EACH_PTR(tmp);
 374
 375         FOR_EACH_PTR(starts_locked, tmp) {
 376                 check_returns_consistently(tmp, &locked);
 377         } END_FOR_EACH_PTR(tmp);
 378
 379         FOR_EACH_PTR(starts_unlocked, tmp) {
 380                 check_returns_consistently(tmp, &unlocked);
 381         } END_FOR_EACH_PTR(tmp);
 382
 383 }
 384
 385 static void clear_lists(void)
 386 {
 387         struct locks_on_return *tmp;
 388
 389         free_trackers_and_list(&starts_locked);
 390         free_trackers_and_list(&starts_unlocked);
 391
 392         FOR_EACH_PTR(all_returns, tmp) {
 393                 free_trackers_and_list(&tmp->locked);
 394                 free_trackers_and_list(&tmp->unlocked);
 395         } END_FOR_EACH_PTR(tmp);
 396         __free_ptr_list((struct ptr_list **)&all_returns);
 397 }
 398
 399 static void match_func_end(struct symbol *sym)
 400 {
 401         check_consistency(sym);
 402         clear_lists();
 403 }
 404
 405 void check_locking(int id)
 406 {
 407         my_id = id;
 408         add_unmatched_state_hook(my_id, &unmatched_state);
 409         add_hook(&match_condition, CONDITION_HOOK);
 410         add_hook(&match_call, FUNCTION_CALL_HOOK);
 411         add_hook(&match_return, RETURN_HOOK);
 412         add_hook(&match_func_end, END_FUNC_HOOK);
 413 }