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>
21 #define MAX_NATIVE_BT 6
22 #define MAX_NATIVE_BT_PROBE (MAX_NATIVE_BT + 5)
23 #define MAX_TRANSITIONS 3
26 #ifdef HAVE_BACKTRACE_SYMBOLS
29 //XXX We should collect just the IPs and lazily symbolificate them.
31 collect_backtrace (gpointer out_data[])
33 return backtrace (out_data, MAX_NATIVE_BT_PROBE);
37 translate_backtrace (gpointer native_trace[], int size)
39 char **names = backtrace_symbols (native_trace, size);
40 GString* bt = g_string_sized_new (100);
44 //Figure out the cut point of useless backtraces
45 //We'll skip up to the caller of checked_build_thread_transition
46 for (i = 0; i < size; ++i) {
47 if (strstr (names [i], "checked_build_thread_transition")) {
55 for (i = j; i < size; ++i) {
56 if (i - j <= MAX_NATIVE_BT)
57 g_string_append_printf (bt, "\tat %s\n", names [i]);
61 return g_string_free (bt, FALSE);
67 collect_backtrace (gpointer out_data[])
73 translate_backtrace (gpointer native_trace[], int size)
75 return g_strdup ("\tno backtrace available\n");
82 GPtrArray *transitions;
87 int from_state, next_state, suspend_count, suspend_count_delta, size;
88 gpointer backtrace [MAX_NATIVE_BT_PROBE];
91 static MonoNativeTlsKey thread_status;
94 checked_build_init (void)
96 mono_native_tls_alloc (&thread_status, NULL);
102 CheckState *state = mono_native_tls_get_value (thread_status);
104 state = g_new0 (CheckState, 1);
105 state->transitions = g_ptr_array_new ();
106 mono_native_tls_set_value (thread_status, state);
113 free_transition (ThreadTransition *t)
119 checked_build_thread_transition (const char *transition, void *info, int from_state, int suspend_count, int next_state, int suspend_count_delta)
121 MonoThreadInfo *cur = mono_thread_info_current_unchecked ();
122 CheckState *state = get_state ();
123 /* We currently don't record external changes as those are hard to reason about. */
127 if (state->transitions->len >= MAX_TRANSITIONS)
128 free_transition (g_ptr_array_remove_index (state->transitions, 0));
130 ThreadTransition *t = g_new0 (ThreadTransition, 1);
131 t->name = transition;
132 t->from_state = from_state;
133 t->next_state = next_state;
134 t->suspend_count = suspend_count;
135 t->suspend_count_delta = suspend_count_delta;
136 t->size = collect_backtrace (t->backtrace);
137 g_ptr_array_add (state->transitions, t);
141 assertion_fail (const char *msg, ...)
144 GString* err = g_string_sized_new (100);
145 CheckState *state = get_state ();
147 g_string_append_printf (err, "Assertion failure in thread %p due to: ", mono_native_thread_id_get ());
150 va_start (args, msg);
151 g_string_append_vprintf (err, msg, args);
154 g_string_append_printf (err, "\nLast %d state transitions: (most recent first)\n", state->transitions->len);
156 for (i = state->transitions->len - 1; i >= 0; --i) {
157 ThreadTransition *t = state->transitions->pdata [i];
158 char *bt = translate_backtrace (t->backtrace, t->size);
159 g_string_append_printf (err, "[%s] %s -> %s (%d) %s%d at:\n%s",
161 mono_thread_state_name (t->from_state),
162 mono_thread_state_name (t->next_state),
164 t->suspend_count_delta > 0 ? "+" : "", //I'd like to see this sort of values: -1, 0, +1
165 t->suspend_count_delta,
171 g_string_free (err, TRUE);
175 assert_gc_safe_mode (void)
177 MonoThreadInfo *cur = mono_thread_info_current ();
181 assertion_fail ("Expected GC Safe mode but thread is not attached");
183 switch (state = mono_thread_info_current_state (cur)) {
185 case STATE_BLOCKING_AND_SUSPENDED:
188 assertion_fail ("Expected GC Safe mode but was in %s state", mono_thread_state_name (state));
193 assert_gc_unsafe_mode (void)
195 MonoThreadInfo *cur = mono_thread_info_current ();
199 assertion_fail ("Expected GC Unsafe mode but thread is not attached");
201 switch (state = mono_thread_info_current_state (cur)) {
203 case STATE_ASYNC_SUSPEND_REQUESTED:
204 case STATE_SELF_SUSPEND_REQUESTED:
207 assertion_fail ("Expected GC Unsafe mode but was in %s state", mono_thread_state_name (state));
212 assert_gc_neutral_mode (void)
214 MonoThreadInfo *cur = mono_thread_info_current ();
218 assertion_fail ("Expected GC Neutral mode but thread is not attached");
220 switch (state = mono_thread_info_current_state (cur)) {
222 case STATE_ASYNC_SUSPEND_REQUESTED:
223 case STATE_SELF_SUSPEND_REQUESTED:
225 case STATE_BLOCKING_AND_SUSPENDED:
228 assertion_fail ("Expected GC Neutral mode but was in %s state", mono_thread_state_name (state));
232 // check_metadata_store et al: The goal of these functions is to verify that if there is a pointer from one mempool into
233 // another, that the pointed-to memory is protected by the reference count mechanism for MonoImages.
235 // Note: The code below catches only some kinds of failures. Failures outside its scope notably incode:
236 // * Code below absolutely assumes that no mempool is ever held as "mempool" member by more than one Image or ImageSet at once
237 // * 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)
238 // Locking strategy is a little slapdash overall.
240 #define check_mempool_assert_message(...) \
241 g_assertion_message("Mempool reference violation: " __VA_ARGS__)
243 // Say image X "references" image Y if X either contains Y in its modules field, or X’s "references" field contains an
244 // assembly whose image is Y.
245 // Say image X transitively references image Y if there is any chain of images-referencing-images which leads from X to Y.
246 // Once the mempools for two pointers have been looked up, there are four possibilities:
248 // Case 1. Image FROM points to Image TO: Legal if FROM transitively references TO
250 // We'll do a simple BFS graph search on images. For each image we visit:
252 check_image_search (GHashTable *visited, GPtrArray *next, MonoImage *candidate, MonoImage *goal, gboolean *success)
254 // Image hasn't even been loaded-- ignore it
258 // Image has already been visited-- ignore it
259 if (g_hash_table_lookup_extended (visited, candidate, NULL, NULL))
262 // Image is the target-- mark success
263 if (candidate == goal)
269 // Unvisited image, queue it to have its children visited
270 g_hash_table_insert (visited, candidate, NULL);
271 g_ptr_array_add (next, candidate);
276 check_image_may_reference_image(MonoImage *from, MonoImage *to)
278 if (to == from) // Shortcut
281 // Corlib is never unloaded, and all images implicitly reference it.
282 // Some images avoid explicitly referencing it as an optimization, so special-case it here.
283 if (to == mono_defaults.corlib)
286 gboolean success = FALSE;
288 // Images to inspect on this pass, images to inspect on the next pass
289 GPtrArray *current = g_ptr_array_sized_new (1), *next = g_ptr_array_new ();
291 // Because in practice the image graph contains cycles, we must track which images we've visited
292 GHashTable *visited = g_hash_table_new (NULL, NULL);
294 #define CHECK_IMAGE_VISIT(i) check_image_search (visited, next, (i), to, &success)
296 CHECK_IMAGE_VISIT (from); // Initially "next" contains only from node
298 // For each pass exhaust the "to check" queue while filling up the "check next" queue
299 while (!success && next->len > 0) // Halt on success or when out of nodes to process
301 // Swap "current" and "next" and clear next
302 GPtrArray *temp = current;
305 g_ptr_array_set_size (next, 0);
308 for(current_idx = 0; current_idx < current->len; current_idx++)
310 MonoImage *checking = g_ptr_array_index (current, current_idx); // CAST?
312 mono_image_lock (checking);
314 // For each queued image visit all directly referenced images
317 for (inner_idx = 0; !success && inner_idx < checking->module_count; inner_idx++)
319 CHECK_IMAGE_VISIT (checking->modules[inner_idx]);
322 for (inner_idx = 0; !success && inner_idx < checking->nreferences; inner_idx++)
324 // References are lazy-loaded and thus allowed to be NULL.
325 // If they are NULL, we don't care about them for this search, because they haven't impacted ref_count yet.
326 if (checking->references[inner_idx])
328 CHECK_IMAGE_VISIT (checking->references[inner_idx]->image);
332 mono_image_unlock (checking);
336 g_ptr_array_free (current, TRUE); g_ptr_array_free (next, TRUE); g_hash_table_destroy (visited);
341 // Case 2. ImageSet FROM points to Image TO: One of FROM's "images" either is, or transitively references, TO.
343 check_image_set_may_reference_image (MonoImageSet *from, MonoImage *to)
345 // See above-- All images implicitly reference corlib
346 if (to == mono_defaults.corlib)
350 gboolean success = FALSE;
351 mono_image_set_lock (from);
352 for (idx = 0; !success && idx < from->nimages; idx++)
354 if (!check_image_may_reference_image (from->images[idx], to))
357 mono_image_set_unlock (from);
359 return success; // No satisfying image found in from->images
362 // Case 3. ImageSet FROM points to ImageSet TO: The images in TO are a strict subset of FROM (no transitive relationship is important here)
364 check_image_set_may_reference_image_set (MonoImageSet *from, MonoImageSet *to)
369 gboolean valid = TRUE; // Until proven otherwise
371 mono_image_set_lock (from); mono_image_set_lock (to);
373 int to_idx, from_idx;
374 for (to_idx = 0; valid && to_idx < to->nimages; to_idx++)
376 gboolean seen = FALSE;
378 // For each item in to->images, scan over from->images looking for it.
379 for (from_idx = 0; !seen && from_idx < from->nimages; from_idx++)
381 if (to->images[to_idx] == from->images[from_idx])
385 // If the to->images item is not found in from->images, the subset check has failed
390 mono_image_set_unlock (from); mono_image_set_unlock (to);
392 return valid; // All items in "to" were found in "from"
395 // Case 4. Image FROM points to ImageSet TO: FROM transitively references *ALL* of the “images” listed in TO
397 check_image_may_reference_image_set (MonoImage *from, MonoImageSet *to)
399 if (to->nimages == 0) // Malformed image_set
402 gboolean valid = TRUE;
404 mono_image_set_lock (to);
406 for (idx = 0; valid && idx < to->nimages; idx++)
408 if (!check_image_may_reference_image (from, to->images[idx]))
411 mono_image_set_unlock (to);
413 return valid; // All images in to->images checked out
416 // Small helper-- get a descriptive string for a MonoMemPoolOwner
418 check_mempool_owner_name (MonoMemPoolOwner owner)
421 return owner.image->name;
422 if (owner.image_set) // TODO: Construct a string containing all included images
424 return "(Non-image memory)";
428 check_mempool_may_reference_mempool (void *from_ptr, void *to_ptr, gboolean require_local)
430 // Null pointers are OK
434 MonoMemPoolOwner from = mono_find_mempool_owner (from_ptr), to = mono_find_mempool_owner (to_ptr);
438 if (!check_mempool_owner_eq (from,to))
439 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));
442 // Writing into unknown mempool
443 else if (check_mempool_owner_eq (from, mono_mempool_no_owner))
445 check_mempool_assert_message ("Non-image memory attempting to write pointer to image %s", check_mempool_owner_name(to));
448 // Reading from unknown mempool
449 else if (check_mempool_owner_eq (to, mono_mempool_no_owner))
451 check_mempool_assert_message ("Attempting to write pointer from image %s to non-image memory", check_mempool_owner_name(from));
454 // Split out the four cases described above:
455 else if (from.image && to.image)
457 if (!check_image_may_reference_image (from.image, to.image))
458 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));
461 else if (from.image && to.image_set)
463 if (!check_image_may_reference_image_set (from.image, to.image_set))
464 check_mempool_assert_message ("Image %s tried to point to image set, but does not retain a reference", check_mempool_owner_name(from));
467 else if (from.image_set && to.image_set)
469 if (!check_image_set_may_reference_image_set (from.image_set, to.image_set))
470 check_mempool_assert_message ("Image set tried to point to image set, but does not retain a reference");
473 else if (from.image_set && to.image)
475 if (!check_image_set_may_reference_image (from.image_set, to.image))
476 check_mempool_assert_message ("Image set tried to point to image %s, but does not retain a reference", check_mempool_owner_name(to));
481 check_mempool_assert_message ("Internal logic error: Unreachable code");
486 check_metadata_store (void *from, void *to)
488 check_mempool_may_reference_mempool (from, to, FALSE);
492 check_metadata_store_local (void *from, void *to)
494 check_mempool_may_reference_mempool (from, to, TRUE);
497 #endif /* CHECKED_BUILD */