2 * checked-build.c: Expensive asserts used when mono is built with --with-checked-build=yes
5 * Rodrigo Kumpera (kumpera@gmail.com)
13 #include <mono/utils/checked-build.h>
14 #include <mono/utils/mono-threads.h>
15 #include <mono/utils/mono-tls.h>
16 #include <mono/metadata/mempool.h>
17 #include <mono/metadata/metadata-internals.h>
18 #include <mono/metadata/image-internals.h>
19 #include <mono/metadata/class-internals.h>
20 #include <mono/metadata/reflection-internals.h>
23 #ifdef HAVE_BACKTRACE_SYMBOLS
28 GPtrArray *transitions;
29 guint32 in_gc_critical_region;
32 static MonoNativeTlsKey thread_status;
35 checked_build_init (void)
37 mono_native_tls_alloc (&thread_status, NULL);
43 CheckState *state = mono_native_tls_get_value (thread_status);
45 state = g_new0 (CheckState, 1);
46 state->transitions = g_ptr_array_new ();
47 mono_native_tls_set_value (thread_status, state);
53 #if !defined(DISABLE_CHECKED_BUILD_THREAD)
55 #define MAX_NATIVE_BT 6
56 #define MAX_NATIVE_BT_PROBE (MAX_NATIVE_BT + 5)
57 #define MAX_TRANSITIONS 3
59 #ifdef HAVE_BACKTRACE_SYMBOLS
61 //XXX We should collect just the IPs and lazily symbolificate them.
63 collect_backtrace (gpointer out_data[])
65 return backtrace (out_data, MAX_NATIVE_BT_PROBE);
69 translate_backtrace (gpointer native_trace[], int size)
71 char **names = backtrace_symbols (native_trace, size);
72 GString* bt = g_string_sized_new (100);
76 //Figure out the cut point of useless backtraces
77 //We'll skip up to the caller of checked_build_thread_transition
78 for (i = 0; i < size; ++i) {
79 if (strstr (names [i], "checked_build_thread_transition")) {
87 for (i = j; i < size; ++i) {
88 if (i - j <= MAX_NATIVE_BT)
89 g_string_append_printf (bt, "\tat %s\n", names [i]);
93 return g_string_free (bt, FALSE);
99 collect_backtrace (gpointer out_data[])
105 translate_backtrace (gpointer native_trace[], int size)
107 return g_strdup ("\tno backtrace available\n");
114 int from_state, next_state, suspend_count, suspend_count_delta, size;
115 gpointer backtrace [MAX_NATIVE_BT_PROBE];
119 free_transition (ThreadTransition *t)
125 checked_build_thread_transition (const char *transition, void *info, int from_state, int suspend_count, int next_state, int suspend_count_delta)
127 MonoThreadInfo *cur = mono_thread_info_current_unchecked ();
128 CheckState *state = get_state ();
129 /* We currently don't record external changes as those are hard to reason about. */
133 if (state->transitions->len >= MAX_TRANSITIONS)
134 free_transition (g_ptr_array_remove_index (state->transitions, 0));
136 ThreadTransition *t = g_new0 (ThreadTransition, 1);
137 t->name = transition;
138 t->from_state = from_state;
139 t->next_state = next_state;
140 t->suspend_count = suspend_count;
141 t->suspend_count_delta = suspend_count_delta;
142 t->size = collect_backtrace (t->backtrace);
143 g_ptr_array_add (state->transitions, t);
146 #endif /* !defined(DISABLE_CHECKED_BUILD_THREAD) */
148 #if !defined(DISABLE_CHECKED_BUILD_GC)
151 assertion_fail (const char *msg, ...)
154 GString* err = g_string_sized_new (100);
155 CheckState *state = get_state ();
157 g_string_append_printf (err, "Assertion failure in thread %p due to: ", mono_native_thread_id_get ());
160 va_start (args, msg);
161 g_string_append_vprintf (err, msg, args);
164 g_string_append_printf (err, "\nLast %d state transitions: (most recent first)\n", state->transitions->len);
166 for (i = state->transitions->len - 1; i >= 0; --i) {
167 ThreadTransition *t = state->transitions->pdata [i];
168 char *bt = translate_backtrace (t->backtrace, t->size);
169 g_string_append_printf (err, "[%s] %s -> %s (%d) %s%d at:\n%s",
171 mono_thread_state_name (t->from_state),
172 mono_thread_state_name (t->next_state),
174 t->suspend_count_delta > 0 ? "+" : "", //I'd like to see this sort of values: -1, 0, +1
175 t->suspend_count_delta,
181 g_string_free (err, TRUE);
185 assert_gc_safe_mode (void)
187 MonoThreadInfo *cur = mono_thread_info_current ();
191 assertion_fail ("Expected GC Safe mode but thread is not attached");
193 switch (state = mono_thread_info_current_state (cur)) {
195 case STATE_BLOCKING_AND_SUSPENDED:
198 assertion_fail ("Expected GC Safe mode but was in %s state", mono_thread_state_name (state));
203 assert_gc_unsafe_mode (void)
205 MonoThreadInfo *cur = mono_thread_info_current ();
209 assertion_fail ("Expected GC Unsafe mode but thread is not attached");
211 switch (state = mono_thread_info_current_state (cur)) {
213 case STATE_ASYNC_SUSPEND_REQUESTED:
214 case STATE_SELF_SUSPEND_REQUESTED:
217 assertion_fail ("Expected GC Unsafe mode but was in %s state", mono_thread_state_name (state));
222 assert_gc_neutral_mode (void)
224 MonoThreadInfo *cur = mono_thread_info_current ();
228 assertion_fail ("Expected GC Neutral mode but thread is not attached");
230 switch (state = mono_thread_info_current_state (cur)) {
232 case STATE_ASYNC_SUSPEND_REQUESTED:
233 case STATE_SELF_SUSPEND_REQUESTED:
235 case STATE_BLOCKING_AND_SUSPENDED:
238 assertion_fail ("Expected GC Neutral mode but was in %s state", mono_thread_state_name (state));
243 critical_gc_region_begin(void)
245 CheckState *state = get_state ();
246 state->in_gc_critical_region++;
252 critical_gc_region_end(void* token)
254 CheckState *state = get_state();
255 g_assert (state == token);
256 state->in_gc_critical_region--;
260 assert_not_in_gc_critical_region(void)
262 CheckState *state = get_state();
263 if (state->in_gc_critical_region > 0) {
264 assertion_fail("Expected GC Unsafe mode, but was in %s state", mono_thread_state_name (mono_thread_info_current_state (mono_thread_info_current ())));
269 assert_in_gc_critical_region (void)
271 CheckState *state = get_state();
272 if (state->in_gc_critical_region == 0)
273 assertion_fail("Expected GC critical region");
276 #endif /* !defined(DISABLE_CHECKED_BUILD_GC) */
278 #if !defined(DISABLE_CHECKED_BUILD_METADATA)
280 // check_metadata_store et al: The goal of these functions is to verify that if there is a pointer from one mempool into
281 // another, that the pointed-to memory is protected by the reference count mechanism for MonoImages.
283 // Note: The code below catches only some kinds of failures. Failures outside its scope notably incode:
284 // * Code below absolutely assumes that no mempool is ever held as "mempool" member by more than one Image or ImageSet at once
285 // * 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)
286 // Locking strategy is a little slapdash overall.
288 // Reference audit support
289 #define check_mempool_assert_message(...) \
290 g_assertion_message("Mempool reference violation: " __VA_ARGS__)
295 MonoImageSet *image_set;
298 static MonoMemPoolOwner mono_mempool_no_owner = {NULL,NULL};
301 check_mempool_owner_eq (MonoMemPoolOwner a, MonoMemPoolOwner b)
303 return a.image == b.image && a.image_set == b.image_set;
306 // Say image X "references" image Y if X either contains Y in its modules field, or X’s "references" field contains an
307 // assembly whose image is Y.
308 // Say image X transitively references image Y if there is any chain of images-referencing-images which leads from X to Y.
309 // Once the mempools for two pointers have been looked up, there are four possibilities:
311 // Case 1. Image FROM points to Image TO: Legal if FROM transitively references TO
313 // We'll do a simple BFS graph search on images. For each image we visit:
315 check_image_search (GHashTable *visited, GPtrArray *next, MonoImage *candidate, MonoImage *goal, gboolean *success)
317 // Image hasn't even been loaded-- ignore it
321 // Image has already been visited-- ignore it
322 if (g_hash_table_lookup_extended (visited, candidate, NULL, NULL))
325 // Image is the target-- mark success
326 if (candidate == goal)
332 // Unvisited image, queue it to have its children visited
333 g_hash_table_insert (visited, candidate, NULL);
334 g_ptr_array_add (next, candidate);
339 check_image_may_reference_image(MonoImage *from, MonoImage *to)
341 if (to == from) // Shortcut
344 // Corlib is never unloaded, and all images implicitly reference it.
345 // Some images avoid explicitly referencing it as an optimization, so special-case it here.
346 if (to == mono_defaults.corlib)
349 // Non-dynamic images may NEVER reference dynamic images
350 if (to->dynamic && !from->dynamic)
353 // FIXME: We currently give a dynamic images a pass on the reference rules.
354 // Dynamic images may ALWAYS reference non-dynamic images.
355 // We allow this because the dynamic image code is known "messy", and in theory it is already
356 // protected because dynamic images can only reference classes their assembly has retained.
357 // However, long term, we should make this rigorous.
358 if (from->dynamic && !to->dynamic)
361 gboolean success = FALSE;
363 // Images to inspect on this pass, images to inspect on the next pass
364 GPtrArray *current = g_ptr_array_sized_new (1), *next = g_ptr_array_new ();
366 // Because in practice the image graph contains cycles, we must track which images we've visited
367 GHashTable *visited = g_hash_table_new (NULL, NULL);
369 #define CHECK_IMAGE_VISIT(i) check_image_search (visited, next, (i), to, &success)
371 CHECK_IMAGE_VISIT (from); // Initially "next" contains only from node
373 // For each pass exhaust the "to check" queue while filling up the "check next" queue
374 while (!success && next->len > 0) // Halt on success or when out of nodes to process
376 // Swap "current" and "next" and clear next
377 GPtrArray *temp = current;
380 g_ptr_array_set_size (next, 0);
383 for(current_idx = 0; current_idx < current->len; current_idx++)
385 MonoImage *checking = g_ptr_array_index (current, current_idx); // CAST?
387 mono_image_lock (checking);
389 // For each queued image visit all directly referenced images
392 for (inner_idx = 0; !success && inner_idx < checking->module_count; inner_idx++)
394 CHECK_IMAGE_VISIT (checking->modules[inner_idx]);
397 for (inner_idx = 0; !success && inner_idx < checking->nreferences; inner_idx++)
399 // References are lazy-loaded and thus allowed to be NULL.
400 // If they are NULL, we don't care about them for this search, because they haven't impacted ref_count yet.
401 if (checking->references[inner_idx])
403 CHECK_IMAGE_VISIT (checking->references[inner_idx]->image);
407 mono_image_unlock (checking);
411 g_ptr_array_free (current, TRUE); g_ptr_array_free (next, TRUE); g_hash_table_destroy (visited);
416 // Case 2. ImageSet FROM points to Image TO: One of FROM's "images" either is, or transitively references, TO.
418 check_image_set_may_reference_image (MonoImageSet *from, MonoImage *to)
420 // See above-- All images implicitly reference corlib
421 if (to == mono_defaults.corlib)
425 gboolean success = FALSE;
426 mono_image_set_lock (from);
427 for (idx = 0; !success && idx < from->nimages; idx++)
429 if (check_image_may_reference_image (from->images[idx], to))
432 mono_image_set_unlock (from);
434 return success; // No satisfying image found in from->images
437 // Case 3. ImageSet FROM points to ImageSet TO: The images in TO are a strict subset of FROM (no transitive relationship is important here)
439 check_image_set_may_reference_image_set (MonoImageSet *from, MonoImageSet *to)
444 gboolean valid = TRUE; // Until proven otherwise
446 mono_image_set_lock (from); mono_image_set_lock (to);
448 int to_idx, from_idx;
449 for (to_idx = 0; valid && to_idx < to->nimages; to_idx++)
451 gboolean seen = FALSE;
453 // If TO set includes corlib, the FROM set may
454 // implicitly reference corlib, even if it's not
455 // present in the set explicitly.
456 if (to->images[to_idx] == mono_defaults.corlib)
459 // For each item in to->images, scan over from->images looking for it.
460 for (from_idx = 0; !seen && from_idx < from->nimages; from_idx++)
462 if (to->images[to_idx] == from->images[from_idx])
466 // If the to->images item is not found in from->images, the subset check has failed
471 mono_image_set_unlock (from); mono_image_set_unlock (to);
473 return valid; // All items in "to" were found in "from"
476 // Case 4. Image FROM points to ImageSet TO: FROM transitively references *ALL* of the “images” listed in TO
478 check_image_may_reference_image_set (MonoImage *from, MonoImageSet *to)
480 if (to->nimages == 0) // Malformed image_set
483 gboolean valid = TRUE;
485 mono_image_set_lock (to);
487 for (idx = 0; valid && idx < to->nimages; idx++)
489 if (!check_image_may_reference_image (from, to->images[idx]))
492 mono_image_set_unlock (to);
494 return valid; // All images in to->images checked out
497 // Small helper-- get a descriptive string for a MonoMemPoolOwner
498 // Callers are obligated to free buffer with g_free after use
500 check_mempool_owner_name (MonoMemPoolOwner owner)
502 GString *result = g_string_new (NULL);
505 if (owner.image->dynamic)
506 g_string_append (result, "(Dynamic)");
507 g_string_append (result, owner.image->name);
509 else if (owner.image_set)
511 char *temp = mono_image_set_description (owner.image_set);
512 g_string_append (result, "(Image set)");
513 g_string_append (result, temp);
518 g_string_append (result, "(Non-image memory)");
520 return g_string_free (result, FALSE);
523 // Helper -- surf various image-locating functions looking for the owner of this pointer
524 static MonoMemPoolOwner
525 mono_find_mempool_owner (void *ptr)
527 MonoMemPoolOwner owner = mono_mempool_no_owner;
529 owner.image = mono_find_image_owner (ptr);
530 if (!check_mempool_owner_eq (owner, mono_mempool_no_owner))
533 owner.image_set = mono_find_image_set_owner (ptr);
534 if (!check_mempool_owner_eq (owner, mono_mempool_no_owner))
537 owner.image = mono_find_dynamic_image_owner (ptr);
542 // Actually perform reference audit
544 check_mempool_may_reference_mempool (void *from_ptr, void *to_ptr, gboolean require_local)
546 // Null pointers are OK
550 MonoMemPoolOwner from = mono_find_mempool_owner (from_ptr), to = mono_find_mempool_owner (to_ptr);
554 if (!check_mempool_owner_eq (from,to))
555 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));
558 // Writing into unknown mempool
559 else if (check_mempool_owner_eq (from, mono_mempool_no_owner))
561 check_mempool_assert_message ("Non-image memory attempting to write pointer to image %s", check_mempool_owner_name (to));
564 // Reading from unknown mempool
565 else if (check_mempool_owner_eq (to, mono_mempool_no_owner))
567 check_mempool_assert_message ("Attempting to write pointer from image %s to non-image memory", check_mempool_owner_name (from));
570 // Split out the four cases described above:
571 else if (from.image && to.image)
573 if (!check_image_may_reference_image (from.image, to.image))
574 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));
577 else if (from.image && to.image_set)
579 if (!check_image_may_reference_image_set (from.image, to.image_set))
580 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));
583 else if (from.image_set && to.image_set)
585 if (!check_image_set_may_reference_image_set (from.image_set, to.image_set))
586 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));
589 else if (from.image_set && to.image)
591 if (!check_image_set_may_reference_image (from.image_set, to.image))
592 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));
597 check_mempool_assert_message ("Internal logic error: Unreachable code");
602 check_metadata_store (void *from, void *to)
604 check_mempool_may_reference_mempool (from, to, FALSE);
608 check_metadata_store_local (void *from, void *to)
610 check_mempool_may_reference_mempool (from, to, TRUE);
613 #endif /* !defined(DISABLE_CHECKED_BUILD_METADATA) */
615 #endif /* CHECKED_BUILD */