2 * checked-build.c: Expensive asserts used when mono is built with --with-checked-build=yes
5 * Rodrigo Kumpera (kumpera@gmail.com)
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>
22 #define MAX_NATIVE_BT 6
23 #define MAX_NATIVE_BT_PROBE (MAX_NATIVE_BT + 5)
24 #define MAX_TRANSITIONS 3
27 #ifdef HAVE_BACKTRACE_SYMBOLS
30 //XXX We should collect just the IPs and lazily symbolificate them.
32 collect_backtrace (gpointer out_data[])
34 return backtrace (out_data, MAX_NATIVE_BT_PROBE);
38 translate_backtrace (gpointer native_trace[], int size)
40 char **names = backtrace_symbols (native_trace, size);
41 GString* bt = g_string_sized_new (100);
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")) {
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]);
62 return g_string_free (bt, FALSE);
68 collect_backtrace (gpointer out_data[])
74 translate_backtrace (gpointer native_trace[], int size)
76 return g_strdup ("\tno backtrace available\n");
83 GPtrArray *transitions;
88 int from_state, next_state, suspend_count, suspend_count_delta, size;
89 gpointer backtrace [MAX_NATIVE_BT_PROBE];
92 static MonoNativeTlsKey thread_status;
95 checked_build_init (void)
97 mono_native_tls_alloc (&thread_status, NULL);
103 CheckState *state = mono_native_tls_get_value (thread_status);
105 state = g_new0 (CheckState, 1);
106 state->transitions = g_ptr_array_new ();
107 mono_native_tls_set_value (thread_status, state);
114 free_transition (ThreadTransition *t)
120 checked_build_thread_transition (const char *transition, void *info, int from_state, int suspend_count, int next_state, int suspend_count_delta)
122 MonoThreadInfo *cur = mono_thread_info_current_unchecked ();
123 CheckState *state = get_state ();
124 /* We currently don't record external changes as those are hard to reason about. */
128 if (state->transitions->len >= MAX_TRANSITIONS)
129 free_transition (g_ptr_array_remove_index (state->transitions, 0));
131 ThreadTransition *t = g_new0 (ThreadTransition, 1);
132 t->name = transition;
133 t->from_state = from_state;
134 t->next_state = next_state;
135 t->suspend_count = suspend_count;
136 t->suspend_count_delta = suspend_count_delta;
137 t->size = collect_backtrace (t->backtrace);
138 g_ptr_array_add (state->transitions, t);
142 assertion_fail (const char *msg, ...)
145 GString* err = g_string_sized_new (100);
146 CheckState *state = get_state ();
148 g_string_append_printf (err, "Assertion failure in thread %p due to: ", mono_native_thread_id_get ());
151 va_start (args, msg);
152 g_string_append_vprintf (err, msg, args);
155 g_string_append_printf (err, "\nLast %d state transitions: (most recent first)\n", state->transitions->len);
157 for (i = state->transitions->len - 1; i >= 0; --i) {
158 ThreadTransition *t = state->transitions->pdata [i];
159 char *bt = translate_backtrace (t->backtrace, t->size);
160 g_string_append_printf (err, "[%s] %s -> %s (%d) %s%d at:\n%s",
162 mono_thread_state_name (t->from_state),
163 mono_thread_state_name (t->next_state),
165 t->suspend_count_delta > 0 ? "+" : "", //I'd like to see this sort of values: -1, 0, +1
166 t->suspend_count_delta,
172 g_string_free (err, TRUE);
176 assert_gc_safe_mode (void)
178 MonoThreadInfo *cur = mono_thread_info_current ();
182 assertion_fail ("Expected GC Safe mode but thread is not attached");
184 switch (state = mono_thread_info_current_state (cur)) {
186 case STATE_BLOCKING_AND_SUSPENDED:
189 assertion_fail ("Expected GC Safe mode but was in %s state", mono_thread_state_name (state));
194 assert_gc_unsafe_mode (void)
196 MonoThreadInfo *cur = mono_thread_info_current ();
200 assertion_fail ("Expected GC Unsafe mode but thread is not attached");
202 switch (state = mono_thread_info_current_state (cur)) {
204 case STATE_ASYNC_SUSPEND_REQUESTED:
205 case STATE_SELF_SUSPEND_REQUESTED:
208 assertion_fail ("Expected GC Unsafe mode but was in %s state", mono_thread_state_name (state));
213 assert_gc_neutral_mode (void)
215 MonoThreadInfo *cur = mono_thread_info_current ();
219 assertion_fail ("Expected GC Neutral mode but thread is not attached");
221 switch (state = mono_thread_info_current_state (cur)) {
223 case STATE_ASYNC_SUSPEND_REQUESTED:
224 case STATE_SELF_SUSPEND_REQUESTED:
226 case STATE_BLOCKING_AND_SUSPENDED:
229 assertion_fail ("Expected GC Neutral mode but was in %s state", mono_thread_state_name (state));
233 // check_metadata_store et al: The goal of these functions is to verify that if there is a pointer from one mempool into
234 // another, that the pointed-to memory is protected by the reference count mechanism for MonoImages.
236 // Note: The code below catches only some kinds of failures. Failures outside its scope notably incode:
237 // * Code below absolutely assumes that no mempool is ever held as "mempool" member by more than one Image or ImageSet at once
238 // * 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)
239 // Locking strategy is a little slapdash overall.
241 // Reference audit support
242 #define check_mempool_assert_message(...) \
243 g_assertion_message("Mempool reference violation: " __VA_ARGS__)
248 MonoImageSet *image_set;
251 static MonoMemPoolOwner mono_mempool_no_owner = {NULL,NULL};
254 check_mempool_owner_eq (MonoMemPoolOwner a, MonoMemPoolOwner b)
256 return a.image == b.image && a.image_set == b.image_set;
259 // Say image X "references" image Y if X either contains Y in its modules field, or X’s "references" field contains an
260 // assembly whose image is Y.
261 // Say image X transitively references image Y if there is any chain of images-referencing-images which leads from X to Y.
262 // Once the mempools for two pointers have been looked up, there are four possibilities:
264 // Case 1. Image FROM points to Image TO: Legal if FROM transitively references TO
266 // We'll do a simple BFS graph search on images. For each image we visit:
268 check_image_search (GHashTable *visited, GPtrArray *next, MonoImage *candidate, MonoImage *goal, gboolean *success)
270 // Image hasn't even been loaded-- ignore it
274 // Image has already been visited-- ignore it
275 if (g_hash_table_lookup_extended (visited, candidate, NULL, NULL))
278 // Image is the target-- mark success
279 if (candidate == goal)
285 // Unvisited image, queue it to have its children visited
286 g_hash_table_insert (visited, candidate, NULL);
287 g_ptr_array_add (next, candidate);
292 check_image_may_reference_image(MonoImage *from, MonoImage *to)
294 if (to == from) // Shortcut
297 // Corlib is never unloaded, and all images implicitly reference it.
298 // Some images avoid explicitly referencing it as an optimization, so special-case it here.
299 if (to == mono_defaults.corlib)
302 // Non-dynamic images may NEVER reference dynamic images
303 if (to->dynamic && !from->dynamic)
306 // FIXME: We currently give a dynamic images a pass on the reference rules.
307 // Dynamic images may ALWAYS reference non-dynamic images.
308 // We allow this because the dynamic image code is known "messy", and in theory it is already
309 // protected because dynamic images can only reference classes their assembly has retained.
310 // However, long term, we should make this rigorous.
311 if (from->dynamic && !to->dynamic)
314 gboolean success = FALSE;
316 // Images to inspect on this pass, images to inspect on the next pass
317 GPtrArray *current = g_ptr_array_sized_new (1), *next = g_ptr_array_new ();
319 // Because in practice the image graph contains cycles, we must track which images we've visited
320 GHashTable *visited = g_hash_table_new (NULL, NULL);
322 #define CHECK_IMAGE_VISIT(i) check_image_search (visited, next, (i), to, &success)
324 CHECK_IMAGE_VISIT (from); // Initially "next" contains only from node
326 // For each pass exhaust the "to check" queue while filling up the "check next" queue
327 while (!success && next->len > 0) // Halt on success or when out of nodes to process
329 // Swap "current" and "next" and clear next
330 GPtrArray *temp = current;
333 g_ptr_array_set_size (next, 0);
336 for(current_idx = 0; current_idx < current->len; current_idx++)
338 MonoImage *checking = g_ptr_array_index (current, current_idx); // CAST?
340 mono_image_lock (checking);
342 // For each queued image visit all directly referenced images
345 for (inner_idx = 0; !success && inner_idx < checking->module_count; inner_idx++)
347 CHECK_IMAGE_VISIT (checking->modules[inner_idx]);
350 for (inner_idx = 0; !success && inner_idx < checking->nreferences; inner_idx++)
352 // References are lazy-loaded and thus allowed to be NULL.
353 // If they are NULL, we don't care about them for this search, because they haven't impacted ref_count yet.
354 if (checking->references[inner_idx])
356 CHECK_IMAGE_VISIT (checking->references[inner_idx]->image);
360 mono_image_unlock (checking);
364 g_ptr_array_free (current, TRUE); g_ptr_array_free (next, TRUE); g_hash_table_destroy (visited);
369 // Case 2. ImageSet FROM points to Image TO: One of FROM's "images" either is, or transitively references, TO.
371 check_image_set_may_reference_image (MonoImageSet *from, MonoImage *to)
373 // See above-- All images implicitly reference corlib
374 if (to == mono_defaults.corlib)
378 gboolean success = FALSE;
379 mono_image_set_lock (from);
380 for (idx = 0; !success && idx < from->nimages; idx++)
382 if (check_image_may_reference_image (from->images[idx], to))
385 mono_image_set_unlock (from);
387 return success; // No satisfying image found in from->images
390 // Case 3. ImageSet FROM points to ImageSet TO: The images in TO are a strict subset of FROM (no transitive relationship is important here)
392 check_image_set_may_reference_image_set (MonoImageSet *from, MonoImageSet *to)
397 gboolean valid = TRUE; // Until proven otherwise
399 mono_image_set_lock (from); mono_image_set_lock (to);
401 int to_idx, from_idx;
402 for (to_idx = 0; valid && to_idx < to->nimages; to_idx++)
404 gboolean seen = FALSE;
406 // For each item in to->images, scan over from->images looking for it.
407 for (from_idx = 0; !seen && from_idx < from->nimages; from_idx++)
409 if (to->images[to_idx] == from->images[from_idx])
413 // If the to->images item is not found in from->images, the subset check has failed
418 mono_image_set_unlock (from); mono_image_set_unlock (to);
420 return valid; // All items in "to" were found in "from"
423 // Case 4. Image FROM points to ImageSet TO: FROM transitively references *ALL* of the “images” listed in TO
425 check_image_may_reference_image_set (MonoImage *from, MonoImageSet *to)
427 if (to->nimages == 0) // Malformed image_set
430 gboolean valid = TRUE;
432 mono_image_set_lock (to);
434 for (idx = 0; valid && idx < to->nimages; idx++)
436 if (!check_image_may_reference_image (from, to->images[idx]))
439 mono_image_set_unlock (to);
441 return valid; // All images in to->images checked out
444 // Small helper-- get a descriptive string for a MonoMemPoolOwner
445 // Callers are obligated to free buffer with g_free after use
447 check_mempool_owner_name (MonoMemPoolOwner owner)
449 GString *result = g_string_new (NULL);
452 if (owner.image->dynamic)
453 g_string_append (result, "(Dynamic)");
454 g_string_append (result, owner.image->name);
456 else if (owner.image_set)
458 char *temp = mono_image_set_description (owner.image_set);
459 g_string_append (result, "(Image set)");
460 g_string_append (result, temp);
465 g_string_append (result, "(Non-image memory)");
467 return g_string_free (result, FALSE);
470 // Helper -- surf various image-locating functions looking for the owner of this pointer
471 static MonoMemPoolOwner
472 mono_find_mempool_owner (void *ptr)
474 MonoMemPoolOwner owner = mono_mempool_no_owner;
476 owner.image = mono_find_image_owner (ptr);
477 if (!check_mempool_owner_eq (owner, mono_mempool_no_owner))
480 owner.image_set = mono_find_image_set_owner (ptr);
481 if (!check_mempool_owner_eq (owner, mono_mempool_no_owner))
484 owner.image = mono_find_dynamic_image_owner (ptr);
489 // Actually perform reference audit
491 check_mempool_may_reference_mempool (void *from_ptr, void *to_ptr, gboolean require_local)
493 // Null pointers are OK
497 MonoMemPoolOwner from = mono_find_mempool_owner (from_ptr), to = mono_find_mempool_owner (to_ptr);
501 if (!check_mempool_owner_eq (from,to))
502 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));
505 // Writing into unknown mempool
506 else if (check_mempool_owner_eq (from, mono_mempool_no_owner))
508 check_mempool_assert_message ("Non-image memory attempting to write pointer to image %s", check_mempool_owner_name (to));
511 // Reading from unknown mempool
512 else if (check_mempool_owner_eq (to, mono_mempool_no_owner))
514 check_mempool_assert_message ("Attempting to write pointer from image %s to non-image memory", check_mempool_owner_name (from));
517 // Split out the four cases described above:
518 else if (from.image && to.image)
520 if (!check_image_may_reference_image (from.image, to.image))
521 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));
524 else if (from.image && to.image_set)
526 if (!check_image_may_reference_image_set (from.image, to.image_set))
527 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));
530 else if (from.image_set && to.image_set)
532 if (!check_image_set_may_reference_image_set (from.image_set, to.image_set))
533 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));
536 else if (from.image_set && to.image)
538 if (!check_image_set_may_reference_image (from.image_set, to.image))
539 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));
544 check_mempool_assert_message ("Internal logic error: Unreachable code");
549 check_metadata_store (void *from, void *to)
551 check_mempool_may_reference_mempool (from, to, FALSE);
555 check_metadata_store_local (void *from, void *to)
557 check_mempool_may_reference_mempool (from, to, TRUE);
560 #endif /* CHECKED_BUILD */