mono/utils/checked-build.c

   1 /*
   2  * checked-build.c: Expensive asserts used when mono is built with --with-checked-build=yes
   3  *
   4  * Author:
   5  *      Rodrigo Kumpera (kumpera@gmail.com)
   6  *
   7  * (C) 2015 Xamarin
   8  */
   9 #include <config.h>
  10 #ifdef CHECKED_BUILD
  11
  12 #include <mono/utils/checked-build.h>
  13 #include <mono/utils/mono-threads.h>
  14 #include <mono/utils/mono-tls.h>
  15 #include <mono/metadata/mempool.h>
  16 #include <mono/metadata/metadata-internals.h>
  17 #include <mono/metadata/image-internals.h>
  18 #include <mono/metadata/class-internals.h>
  19 #include <mono/metadata/reflection-internals.h>
  20 #include <glib.h>
  21
  22 #define MAX_NATIVE_BT 6
  23 #define MAX_NATIVE_BT_PROBE (MAX_NATIVE_BT + 5)
  24 #define MAX_TRANSITIONS 3
  25
  26
  27 #ifdef HAVE_BACKTRACE_SYMBOLS
  28 #include <execinfo.h>
  29
  30 //XXX We should collect just the IPs and lazily symbolificate them.
  31 static int
  32 collect_backtrace (gpointer out_data[])
  33 {
  34         return backtrace (out_data, MAX_NATIVE_BT_PROBE);
  35 }
  36
  37 static char*
  38 translate_backtrace (gpointer native_trace[], int size)
  39 {
  40         char **names = backtrace_symbols (native_trace, size);
  41         GString* bt = g_string_sized_new (100);
  42
  43         int i, j = -1;
  44
  45         //Figure out the cut point of useless backtraces
  46         //We'll skip up to the caller of checked_build_thread_transition
  47         for (i = 0; i < size; ++i) {
  48                 if (strstr (names [i], "checked_build_thread_transition")) {
  49                         j = i + 1;
  50                         break;
  51                 }
  52         }
  53
  54         if (j == -1)
  55                 j = 0;
  56         for (i = j; i < size; ++i) {
  57                 if (i - j <= MAX_NATIVE_BT)
  58                         g_string_append_printf (bt, "\tat %s\n", names [i]);
  59         }
  60
  61         free (names);
  62         return g_string_free (bt, FALSE);
  63 }
  64
  65 #else
  66
  67 static int
  68 collect_backtrace (gpointer out_data[])
  69 {
  70         return 0;
  71 }
  72
  73 static char*
  74 translate_backtrace (gpointer native_trace[], int size)
  75 {
  76         return g_strdup ("\tno backtrace available\n");
  77 }
  78
  79 #endif
  80
  81
  82 typedef struct {
  83         GPtrArray *transitions;
  84         gboolean in_gc_critical_region;
  85 } CheckState;
  86
  87 typedef struct {
  88         const char *name;
  89         int from_state, next_state, suspend_count, suspend_count_delta, size;
  90         gpointer backtrace [MAX_NATIVE_BT_PROBE];
  91 } ThreadTransition;
  92
  93 static MonoNativeTlsKey thread_status;
  94
  95 void
  96 checked_build_init (void)
  97 {
  98         mono_native_tls_alloc (&thread_status, NULL);
  99 }
 100
 101 static CheckState*
 102 get_state (void)
 103 {
 104         CheckState *state = mono_native_tls_get_value (thread_status);
 105         if (!state) {
 106                 state = g_new0 (CheckState, 1);
 107                 state->transitions = g_ptr_array_new ();
 108                 mono_native_tls_set_value (thread_status, state);
 109         }
 110
 111         return state;
 112 }
 113
 114 static void
 115 free_transition (ThreadTransition *t)
 116 {
 117         g_free (t);
 118 }
 119
 120 void
 121 checked_build_thread_transition (const char *transition, void *info, int from_state, int suspend_count, int next_state, int suspend_count_delta)
 122 {
 123         MonoThreadInfo *cur = mono_thread_info_current_unchecked ();
 124         CheckState *state = get_state ();
 125         /* We currently don't record external changes as those are hard to reason about. */
 126         if (cur != info)
 127                 return;
 128
 129         if (state->transitions->len >= MAX_TRANSITIONS)
 130                 free_transition (g_ptr_array_remove_index (state->transitions, 0));
 131
 132         ThreadTransition *t = g_new0 (ThreadTransition, 1);
 133         t->name = transition;
 134         t->from_state = from_state;
 135         t->next_state = next_state;
 136         t->suspend_count = suspend_count;
 137         t->suspend_count_delta = suspend_count_delta;
 138         t->size = collect_backtrace (t->backtrace);
 139         g_ptr_array_add (state->transitions, t);
 140 }
 141
 142 static void
 143 assertion_fail (const char *msg, ...)
 144 {
 145         int i;
 146         GString* err = g_string_sized_new (100);
 147         CheckState *state = get_state ();
 148
 149         g_string_append_printf (err, "Assertion failure in thread %p due to: ", mono_native_thread_id_get ());
 150
 151         va_list args;
 152         va_start (args, msg);
 153         g_string_append_vprintf (err, msg, args);
 154         va_end (args);
 155
 156         g_string_append_printf (err, "\nLast %d state transitions: (most recent first)\n", state->transitions->len);
 157
 158         for (i = state->transitions->len - 1; i >= 0; --i) {
 159                 ThreadTransition *t = state->transitions->pdata [i];
 160                 char *bt = translate_backtrace (t->backtrace, t->size);
 161                 g_string_append_printf (err, "[%s] %s -> %s (%d) %s%d at:\n%s",
 162                         t->name,
 163                         mono_thread_state_name (t->from_state),
 164                         mono_thread_state_name (t->next_state),
 165                         t->suspend_count,
 166                         t->suspend_count_delta > 0 ? "+" : "", //I'd like to see this sort of values: -1, 0, +1
 167                         t->suspend_count_delta,
 168                         bt);
 169                 g_free (bt);
 170         }
 171
 172         g_error (err->str);
 173         g_string_free (err, TRUE);
 174 }
 175
 176 void
 177 assert_gc_safe_mode (void)
 178 {
 179         MonoThreadInfo *cur = mono_thread_info_current ();
 180         int state;
 181
 182         if (!cur)
 183                 assertion_fail ("Expected GC Safe mode but thread is not attached");
 184
 185         switch (state = mono_thread_info_current_state (cur)) {
 186         case STATE_BLOCKING:
 187         case STATE_BLOCKING_AND_SUSPENDED:
 188                 break;
 189         default:
 190                 assertion_fail ("Expected GC Safe mode but was in %s state", mono_thread_state_name (state));
 191         }
 192 }
 193
 194 void
 195 assert_gc_unsafe_mode (void)
 196 {
 197         MonoThreadInfo *cur = mono_thread_info_current ();
 198         int state;
 199
 200         if (!cur)
 201                 assertion_fail ("Expected GC Unsafe mode but thread is not attached");
 202
 203         switch (state = mono_thread_info_current_state (cur)) {
 204         case STATE_RUNNING:
 205         case STATE_ASYNC_SUSPEND_REQUESTED:
 206         case STATE_SELF_SUSPEND_REQUESTED:
 207                 break;
 208         default:
 209                 assertion_fail ("Expected GC Unsafe mode but was in %s state", mono_thread_state_name (state));
 210         }
 211 }
 212
 213 void
 214 assert_gc_neutral_mode (void)
 215 {
 216         MonoThreadInfo *cur = mono_thread_info_current ();
 217         int state;
 218
 219         if (!cur)
 220                 assertion_fail ("Expected GC Neutral mode but thread is not attached");
 221
 222         switch (state = mono_thread_info_current_state (cur)) {
 223         case STATE_RUNNING:
 224         case STATE_ASYNC_SUSPEND_REQUESTED:
 225         case STATE_SELF_SUSPEND_REQUESTED:
 226         case STATE_BLOCKING:
 227         case STATE_BLOCKING_AND_SUSPENDED:
 228                 break;
 229         default:
 230                 assertion_fail ("Expected GC Neutral mode but was in %s state", mono_thread_state_name (state));
 231         }
 232 }
 233
 234 void *
 235 critical_gc_region_begin(void)
 236 {
 237         CheckState *state = get_state ();
 238         state->in_gc_critical_region = TRUE;
 239         return state;
 240 }
 241
 242
 243 void
 244 critical_gc_region_end(void* token)
 245 {
 246         CheckState *state = get_state();
 247         g_assert (state == token);
 248         state->in_gc_critical_region = FALSE;
 249 }
 250
 251 void
 252 assert_not_in_gc_critical_region(void)
 253 {
 254         CheckState *state = get_state();
 255         if (state->in_gc_critical_region) {
 256                 MonoThreadInfo *cur = mono_thread_info_current();
 257                 state = mono_thread_info_current_state(cur);
 258                 assertion_fail("Expected GC Unsafe mode, but was in %s state", mono_thread_state_name(state));
 259         }
 260 }
 261
 262 // check_metadata_store et al: The goal of these functions is to verify that if there is a pointer from one mempool into
 263 // another, that the pointed-to memory is protected by the reference count mechanism for MonoImages.
 264 //
 265 // Note: The code below catches only some kinds of failures. Failures outside its scope notably incode:
 266 // * Code below absolutely assumes that no mempool is ever held as "mempool" member by more than one Image or ImageSet at once
 267 // * Code below assumes reference counts never underflow (ie: if we have a pointer to something, it won't be deallocated while we're looking at it)
 268 // Locking strategy is a little slapdash overall.
 269
 270 // Reference audit support
 271 #define check_mempool_assert_message(...) \
 272         g_assertion_message("Mempool reference violation: " __VA_ARGS__)
 273
 274 typedef struct
 275 {
 276         MonoImage *image;
 277         MonoImageSet *image_set;
 278 } MonoMemPoolOwner;
 279
 280 static MonoMemPoolOwner mono_mempool_no_owner = {NULL,NULL};
 281
 282 static gboolean
 283 check_mempool_owner_eq (MonoMemPoolOwner a, MonoMemPoolOwner b)
 284 {
 285         return a.image == b.image && a.image_set == b.image_set;
 286 }
 287
 288 // Say image X "references" image Y if X either contains Y in its modules field, or X’s "references" field contains an
 289 // assembly whose image is Y.
 290 // Say image X transitively references image Y if there is any chain of images-referencing-images which leads from X to Y.
 291 // Once the mempools for two pointers have been looked up, there are four possibilities:
 292
 293 // Case 1. Image FROM points to Image TO: Legal if FROM transitively references TO
 294
 295 // We'll do a simple BFS graph search on images. For each image we visit:
 296 static void
 297 check_image_search (GHashTable *visited, GPtrArray *next, MonoImage *candidate, MonoImage *goal, gboolean *success)
 298 {
 299         // Image hasn't even been loaded-- ignore it
 300         if (!candidate)
 301                 return;
 302
 303         // Image has already been visited-- ignore it
 304         if (g_hash_table_lookup_extended (visited, candidate, NULL, NULL))
 305                 return;
 306
 307         // Image is the target-- mark success
 308         if (candidate == goal)
 309         {
 310                 *success = TRUE;
 311                 return;
 312         }
 313
 314         // Unvisited image, queue it to have its children visited
 315         g_hash_table_insert (visited, candidate, NULL);
 316         g_ptr_array_add (next, candidate);
 317         return;
 318 }
 319
 320 static gboolean
 321 check_image_may_reference_image(MonoImage *from, MonoImage *to)
 322 {
 323         if (to == from) // Shortcut
 324                 return TRUE;
 325
 326         // Corlib is never unloaded, and all images implicitly reference it.
 327         // Some images avoid explicitly referencing it as an optimization, so special-case it here.
 328         if (to == mono_defaults.corlib)
 329                 return TRUE;
 330
 331         // Non-dynamic images may NEVER reference dynamic images
 332         if (to->dynamic && !from->dynamic)
 333                 return FALSE;
 334
 335         // FIXME: We currently give a dynamic images a pass on the reference rules.
 336         // Dynamic images may ALWAYS reference non-dynamic images.
 337         // We allow this because the dynamic image code is known "messy", and in theory it is already
 338         // protected because dynamic images can only reference classes their assembly has retained.
 339         // However, long term, we should make this rigorous.
 340         if (from->dynamic && !to->dynamic)
 341                 return TRUE;
 342
 343         gboolean success = FALSE;
 344
 345         // Images to inspect on this pass, images to inspect on the next pass
 346         GPtrArray *current = g_ptr_array_sized_new (1), *next = g_ptr_array_new ();
 347
 348         // Because in practice the image graph contains cycles, we must track which images we've visited
 349         GHashTable *visited = g_hash_table_new (NULL, NULL);
 350
 351         #define CHECK_IMAGE_VISIT(i) check_image_search (visited, next, (i), to, &success)
 352
 353         CHECK_IMAGE_VISIT (from); // Initially "next" contains only from node
 354
 355         // For each pass exhaust the "to check" queue while filling up the "check next" queue
 356         while (!success && next->len > 0) // Halt on success or when out of nodes to process
 357         {
 358                 // Swap "current" and "next" and clear next
 359                 GPtrArray *temp = current;
 360                 current = next;
 361                 next = temp;
 362                 g_ptr_array_set_size (next, 0);
 363
 364                 int current_idx;
 365                 for(current_idx = 0; current_idx < current->len; current_idx++)
 366                 {
 367                         MonoImage *checking = g_ptr_array_index (current, current_idx); // CAST?
 368
 369                         mono_image_lock (checking);
 370
 371                         // For each queued image visit all directly referenced images
 372                         int inner_idx;
 373
 374                         for (inner_idx = 0; !success && inner_idx < checking->module_count; inner_idx++)
 375                         {
 376                                 CHECK_IMAGE_VISIT (checking->modules[inner_idx]);
 377                         }
 378
 379                         for (inner_idx = 0; !success && inner_idx < checking->nreferences; inner_idx++)
 380                         {
 381                                 // References are lazy-loaded and thus allowed to be NULL.
 382                                 // If they are NULL, we don't care about them for this search, because they haven't impacted ref_count yet.
 383                                 if (checking->references[inner_idx])
 384                                 {
 385                                         CHECK_IMAGE_VISIT (checking->references[inner_idx]->image);
 386                                 }
 387                         }
 388
 389                         mono_image_unlock (checking);
 390                 }
 391         }
 392
 393         g_ptr_array_free (current, TRUE); g_ptr_array_free (next, TRUE); g_hash_table_destroy (visited);
 394
 395         return success;
 396 }
 397
 398 // Case 2. ImageSet FROM points to Image TO: One of FROM's "images" either is, or transitively references, TO.
 399 static gboolean
 400 check_image_set_may_reference_image (MonoImageSet *from, MonoImage *to)
 401 {
 402         // See above-- All images implicitly reference corlib
 403         if (to == mono_defaults.corlib)
 404                 return TRUE;
 405
 406         int idx;
 407         gboolean success = FALSE;
 408         mono_image_set_lock (from);
 409         for (idx = 0; !success && idx < from->nimages; idx++)
 410         {
 411                 if (check_image_may_reference_image (from->images[idx], to))
 412                         success = TRUE;
 413         }
 414         mono_image_set_unlock (from);
 415
 416         return success; // No satisfying image found in from->images
 417 }
 418
 419 // Case 3. ImageSet FROM points to ImageSet TO: The images in TO are a strict subset of FROM (no transitive relationship is important here)
 420 static gboolean
 421 check_image_set_may_reference_image_set (MonoImageSet *from, MonoImageSet *to)
 422 {
 423         if (to == from)
 424                 return TRUE;
 425
 426         gboolean valid = TRUE; // Until proven otherwise
 427
 428         mono_image_set_lock (from); mono_image_set_lock (to);
 429
 430         int to_idx, from_idx;
 431         for (to_idx = 0; valid && to_idx < to->nimages; to_idx++)
 432         {
 433                 gboolean seen = FALSE;
 434
 435                 // For each item in to->images, scan over from->images looking for it.
 436                 for (from_idx = 0; !seen && from_idx < from->nimages; from_idx++)
 437                 {
 438                         if (to->images[to_idx] == from->images[from_idx])
 439                                 seen = TRUE;
 440                 }
 441
 442                 // If the to->images item is not found in from->images, the subset check has failed
 443                 if (!seen)
 444                         valid = FALSE;
 445         }
 446
 447         mono_image_set_unlock (from); mono_image_set_unlock (to);
 448
 449         return valid; // All items in "to" were found in "from"
 450 }
 451
 452 // Case 4. Image FROM points to ImageSet TO: FROM transitively references *ALL* of the “images” listed in TO
 453 static gboolean
 454 check_image_may_reference_image_set (MonoImage *from, MonoImageSet *to)
 455 {
 456         if (to->nimages == 0) // Malformed image_set
 457                 return FALSE;
 458
 459         gboolean valid = TRUE;
 460
 461         mono_image_set_lock (to);
 462         int idx;
 463         for (idx = 0; valid && idx < to->nimages; idx++)
 464         {
 465                 if (!check_image_may_reference_image (from, to->images[idx]))
 466                         valid = FALSE;
 467         }
 468         mono_image_set_unlock (to);
 469
 470         return valid; // All images in to->images checked out
 471 }
 472
 473 // Small helper-- get a descriptive string for a MonoMemPoolOwner
 474 // Callers are obligated to free buffer with g_free after use
 475 static const char *
 476 check_mempool_owner_name (MonoMemPoolOwner owner)
 477 {
 478         GString *result = g_string_new (NULL);
 479         if (owner.image)
 480         {
 481                 if (owner.image->dynamic)
 482                         g_string_append (result, "(Dynamic)");
 483                 g_string_append (result, owner.image->name);
 484         }
 485         else if (owner.image_set)
 486         {
 487                 char *temp = mono_image_set_description (owner.image_set);
 488                 g_string_append (result, "(Image set)");
 489                 g_string_append (result, temp);
 490                 g_free (temp);
 491         }
 492         else
 493         {
 494                 g_string_append (result, "(Non-image memory)");
 495         }
 496         return g_string_free (result, FALSE);
 497 }
 498
 499 // Helper -- surf various image-locating functions looking for the owner of this pointer
 500 static MonoMemPoolOwner
 501 mono_find_mempool_owner (void *ptr)
 502 {
 503         MonoMemPoolOwner owner = mono_mempool_no_owner;
 504
 505         owner.image = mono_find_image_owner (ptr);
 506         if (!check_mempool_owner_eq (owner, mono_mempool_no_owner))
 507                 return owner;
 508
 509         owner.image_set = mono_find_image_set_owner (ptr);
 510         if (!check_mempool_owner_eq (owner, mono_mempool_no_owner))
 511                 return owner;
 512
 513         owner.image = mono_find_dynamic_image_owner (ptr);
 514
 515         return owner;
 516 }
 517
 518 // Actually perform reference audit
 519 static void
 520 check_mempool_may_reference_mempool (void *from_ptr, void *to_ptr, gboolean require_local)
 521 {
 522         // Null pointers are OK
 523         if (!to_ptr)
 524                 return;
 525
 526         MonoMemPoolOwner from = mono_find_mempool_owner (from_ptr), to = mono_find_mempool_owner (to_ptr);
 527
 528         if (require_local)
 529         {
 530                 if (!check_mempool_owner_eq (from,to))
 531                         check_mempool_assert_message ("Pointer in image %s should have been internal, but instead pointed to image %s", check_mempool_owner_name (from), check_mempool_owner_name (to));
 532         }
 533
 534         // Writing into unknown mempool
 535         else if (check_mempool_owner_eq (from, mono_mempool_no_owner))
 536         {
 537                 check_mempool_assert_message ("Non-image memory attempting to write pointer to image %s", check_mempool_owner_name (to));
 538         }
 539
 540         // Reading from unknown mempool
 541         else if (check_mempool_owner_eq (to, mono_mempool_no_owner))
 542         {
 543                 check_mempool_assert_message ("Attempting to write pointer from image %s to non-image memory", check_mempool_owner_name (from));
 544         }
 545
 546         // Split out the four cases described above:
 547         else if (from.image && to.image)
 548         {
 549                 if (!check_image_may_reference_image (from.image, to.image))
 550                         check_mempool_assert_message ("Image %s tried to point to image %s, but does not retain a reference", check_mempool_owner_name (from), check_mempool_owner_name (to));
 551         }
 552
 553         else if (from.image && to.image_set)
 554         {
 555                 if (!check_image_may_reference_image_set (from.image, to.image_set))
 556                         check_mempool_assert_message ("Image %s tried to point to image set %s, but does not retain a reference", check_mempool_owner_name (from), check_mempool_owner_name (to));
 557         }
 558
 559         else if (from.image_set && to.image_set)
 560         {
 561                 if (!check_image_set_may_reference_image_set (from.image_set, to.image_set))
 562                         check_mempool_assert_message ("Image set %s tried to point to image set %s, but does not retain a reference", check_mempool_owner_name (from), check_mempool_owner_name (to));
 563         }
 564
 565         else if (from.image_set && to.image)
 566         {
 567                 if (!check_image_set_may_reference_image (from.image_set, to.image))
 568                         check_mempool_assert_message ("Image set %s tried to point to image %s, but does not retain a reference", check_mempool_owner_name (from), check_mempool_owner_name (to));
 569         }
 570
 571         else
 572         {
 573                 check_mempool_assert_message ("Internal logic error: Unreachable code");
 574         }
 575 }
 576
 577 void
 578 check_metadata_store (void *from, void *to)
 579 {
 580     check_mempool_may_reference_mempool (from, to, FALSE);
 581 }
 582
 583 void
 584 check_metadata_store_local (void *from, void *to)
 585 {
 586     check_mempool_may_reference_mempool (from, to, TRUE);
 587 }
 588
 589 #endif /* CHECKED_BUILD */