1 // boehm.cc - interface between libjava and Boehm GC.
3 /* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 Free Software Foundation
6 This file is part of libgcj.
8 This software is copyrighted work licensed under the terms of the
9 Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
20 #include <java/lang/Class.h>
21 #include <java/lang/reflect/Modifier.h>
22 #include <java-interp.h>
24 // More nastiness: the GC wants to define TRUE and FALSE. We don't
25 // need the Java definitions (themselves a hack), so we undefine them.
29 // We include two autoconf headers. Avoid multiple definition warnings.
32 #undef PACKAGE_TARNAME
33 #undef PACKAGE_VERSION
43 #include <gc_config.h>
45 // Set GC_DEBUG before including gc.h!
46 #ifdef LIBGCJ_GC_DEBUG
52 #include <javaxfc.h> // GC_finalize_all declaration.
54 #ifdef THREAD_LOCAL_ALLOC
55 # define GC_REDIRECT_TO_LOCAL
56 # include <gc_local_alloc.h>
59 // From boehm's misc.c
64 #define MAYBE_MARK(Obj, Top, Limit, Source) \
65 Top=GC_MARK_AND_PUSH((GC_PTR) Obj, Top, Limit, (GC_PTR *) Source)
67 // `kind' index used when allocating Java arrays.
68 static int array_kind_x;
70 // Freelist used for Java arrays.
71 static void **array_free_list;
73 static int _Jv_GC_has_static_roots (const char *filename, void *, size_t);
77 // This is called by the GC during the mark phase. It marks a Java
78 // object. We use `void *' arguments and return, and not what the
79 // Boehm GC wants, to avoid pollution in our headers.
81 _Jv_MarkObj (void *addr, void *msp, void *msl, void *env)
83 struct GC_ms_entry *mark_stack_ptr = (struct GC_ms_entry *)msp;
84 struct GC_ms_entry *mark_stack_limit = (struct GC_ms_entry *)msl;
86 if (env == (void *)1) /* Object allocated with debug allocator. */
87 addr = (GC_PTR)GC_USR_PTR_FROM_BASE(addr);
88 jobject obj = (jobject) addr;
90 _Jv_VTable *dt = *(_Jv_VTable **) addr;
91 // The object might not yet have its vtable set, or it might
92 // really be an object on the freelist. In either case, the vtable slot
93 // will either be 0, or it will point to a cleared object.
94 // This assumes Java objects have size at least 3 words,
95 // including the header. But this should remain true, since this
96 // should only be used with debugging allocation or with large objects.
97 if (__builtin_expect (! dt || !(dt -> get_finalizer()), false))
98 return mark_stack_ptr;
99 jclass klass = dt->clas;
103 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, obj);
105 # ifndef JV_HASH_SYNCHRONIZATION
106 // Every object has a sync_info pointer.
107 p = (GC_PTR) obj->sync_info;
108 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, obj);
111 if (__builtin_expect (klass == &java::lang::Class::class$, false))
113 // Currently we allocate some of the memory referenced from class objects
114 // as pointerfree memory, and then mark it more intelligently here.
115 // We ensure that the ClassClass mark descriptor forces invocation of
117 // Correctness of this is subtle, but it looks OK to me for now. For the incremental
118 // collector, we need to make sure that the class object is written whenever
119 // any of the subobjects are altered and may need rescanning. This may be tricky
120 // during construction, and this may not be the right way to do this with
121 // incremental collection.
122 // If we overflow the mark stack, we will rescan the class object, so we should
123 // be OK. The same applies if we redo the mark phase because win32 unmapped part
124 // of our root set. - HB
125 jclass c = (jclass) addr;
127 p = (GC_PTR) c->name;
128 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
129 p = (GC_PTR) c->superclass;
130 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
132 p = (GC_PTR) c->constants.tags;
133 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
134 p = (GC_PTR) c->constants.data;
135 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
137 // If the class is an array, then the methods field holds a
138 // pointer to the element class. If the class is primitive,
139 // then the methods field holds a pointer to the array class.
140 p = (GC_PTR) c->methods;
141 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
143 p = (GC_PTR) c->fields;
144 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
146 // The vtable might be allocated even for compiled code.
147 p = (GC_PTR) c->vtable;
148 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
150 p = (GC_PTR) c->interfaces;
151 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
152 p = (GC_PTR) c->loader;
153 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
155 // The dispatch tables can be allocated at runtime.
156 p = (GC_PTR) c->ancestors;
157 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
160 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
162 p = (GC_PTR) c->arrayclass;
163 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
164 p = (GC_PTR) c->protectionDomain;
165 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
166 p = (GC_PTR) c->hack_signers;
167 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
168 p = (GC_PTR) c->aux_info;
169 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, c);
173 // NOTE: each class only holds information about the class
174 // itself. So we must do the marking for the entire inheritance
175 // tree in order to mark all fields. FIXME: what about
176 // interfaces? We skip Object here, because Object only has a
177 // sync_info, and we handled that earlier.
178 // Note: occasionally `klass' can be null. For instance, this
179 // can happen if a GC occurs between the point where an object
180 // is allocated and where the vtbl slot is set.
181 while (klass && klass != &java::lang::Object::class$)
183 jfieldID field = JvGetFirstInstanceField (klass);
184 jint max = JvNumInstanceFields (klass);
186 for (int i = 0; i < max; ++i)
188 if (JvFieldIsRef (field))
190 jobject val = JvGetObjectField (obj, field);
192 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, obj);
194 field = field->getNextField ();
196 klass = klass->getSuperclass();
200 return mark_stack_ptr;
203 // This is called by the GC during the mark phase. It marks a Java
204 // array (of objects). We use `void *' arguments and return, and not
205 // what the Boehm GC wants, to avoid pollution in our headers.
207 _Jv_MarkArray (void *addr, void *msp, void *msl, void *env)
209 struct GC_ms_entry *mark_stack_ptr = (struct GC_ms_entry *)msp;
210 struct GC_ms_entry *mark_stack_limit = (struct GC_ms_entry *)msl;
212 if (env == (void *)1) /* Object allocated with debug allocator. */
213 addr = (void *)GC_USR_PTR_FROM_BASE(addr);
214 jobjectArray array = (jobjectArray) addr;
216 _Jv_VTable *dt = *(_Jv_VTable **) addr;
217 // Assumes size >= 3 words. That's currently true since arrays have
218 // a vtable, sync pointer, and size. If the sync pointer goes away,
219 // we may need to round up the size.
220 if (__builtin_expect (! dt || !(dt -> get_finalizer()), false))
221 return mark_stack_ptr;
225 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, array);
227 # ifndef JV_HASH_SYNCHRONIZATION
228 // Every object has a sync_info pointer.
229 p = (GC_PTR) array->sync_info;
230 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, array);
233 for (int i = 0; i < JvGetArrayLength (array); ++i)
235 jobject obj = elements (array)[i];
237 MAYBE_MARK (p, mark_stack_ptr, mark_stack_limit, array);
240 return mark_stack_ptr;
243 // Generate a GC marking descriptor for a class.
245 // We assume that the gcj mark proc has index 0. This is a dubious assumption,
246 // since another one could be registered first. But the compiler also
247 // knows this, so in that case everything else will break, too.
248 #define GCJ_DEFAULT_DESCR GC_MAKE_PROC(GC_GCJ_RESERVED_MARK_PROC_INDEX,0)
251 _Jv_BuildGCDescr(jclass self)
254 jint bits_per_word = CHAR_BIT * sizeof (void *);
256 // Note: for now we only consider a bitmap mark descriptor. We
257 // could also handle the case where the first N fields of a type are
258 // references. However, this is not very likely to be used by many
259 // classes, and it is easier to compute things this way.
261 // The vtable pointer.
262 desc |= 1ULL << (bits_per_word - 1);
263 #ifndef JV_HASH_SYNCHRONIZATION
264 // The sync_info field.
265 desc |= 1ULL << (bits_per_word - 2);
268 for (jclass klass = self; klass != NULL; klass = klass->getSuperclass())
270 jfieldID field = JvGetFirstInstanceField(klass);
271 int count = JvNumInstanceFields(klass);
273 for (int i = 0; i < count; ++i)
277 unsigned int off = field->getOffset();
278 // If we run into a weird situation, we bail.
279 if (off % sizeof (void *) != 0)
280 return (void *) (GCJ_DEFAULT_DESCR);
281 off /= sizeof (void *);
282 // If we find a field outside the range of our bitmap,
283 // fall back to procedure marker. The bottom 2 bits are
285 if (off >= (unsigned) bits_per_word - 2)
286 return (void *) (GCJ_DEFAULT_DESCR);
287 desc |= 1ULL << (bits_per_word - off - 1);
290 field = field->getNextField();
294 // For bitmap mark type, bottom bits are 01.
296 // Bogus warning avoidance (on many platforms).
297 return (void *) (unsigned long) desc;
300 // Allocate some space that is known to be pointer-free.
302 _Jv_AllocBytes (jsize size)
304 void *r = GC_MALLOC_ATOMIC (size);
305 // We have to explicitly zero memory here, as the GC doesn't
306 // guarantee that PTRFREE allocations are zeroed. Note that we
307 // don't have to do this for other allocation types because we set
308 // the `ok_init' flag in the type descriptor.
313 #ifdef LIBGCJ_GC_DEBUG
316 _Jv_AllocObj (jsize size, jclass klass)
318 return GC_GCJ_MALLOC (size, klass->vtable);
322 _Jv_AllocPtrFreeObj (jsize size, jclass klass)
324 #ifdef JV_HASH_SYNCHRONIZATION
325 void * obj = GC_MALLOC_ATOMIC(size);
326 *((_Jv_VTable **) obj) = klass->vtable;
328 void * obj = GC_GCJ_MALLOC(size, klass->vtable);
333 #endif /* LIBGCJ_GC_DEBUG */
334 // In the non-debug case, the above two functions are defined
335 // as inline functions in boehm-gc.h. In the debug case we
336 // really want to take advantage of the definitions in gc_gcj.h.
338 // Allocate space for a new Java array.
339 // Used only for arrays of objects.
341 _Jv_AllocArray (jsize size, jclass klass)
345 #ifdef LIBGCJ_GC_DEBUG
346 // There isn't much to lose by scanning this conservatively.
347 // If we didn't, the mark proc would have to understand that
348 // it needed to skip the header.
349 obj = GC_MALLOC(size);
351 const jsize min_heap_addr = 16*1024;
352 // A heuristic. If size is less than this value, the size
353 // stored in the array can't possibly be misinterpreted as
354 // a pointer. Thus we lose nothing by scanning the object
355 // completely conservatively, since no misidentification can
358 if (size < min_heap_addr)
359 obj = GC_MALLOC(size);
361 obj = GC_generic_malloc (size, array_kind_x);
363 *((_Jv_VTable **) obj) = klass->vtable;
367 /* Allocate space for a new non-Java object, which does not have the usual
368 Java object header but may contain pointers to other GC'ed objects. */
370 _Jv_AllocRawObj (jsize size)
372 return (void *) GC_MALLOC (size ? size : 1);
376 call_finalizer (GC_PTR obj, GC_PTR client_data)
378 _Jv_FinalizerFunc *fn = (_Jv_FinalizerFunc *) client_data;
379 jobject jobj = (jobject) obj;
385 _Jv_RegisterFinalizer (void *object, _Jv_FinalizerFunc *meth)
387 GC_REGISTER_FINALIZER_NO_ORDER (object, call_finalizer, (GC_PTR) meth,
392 _Jv_RunFinalizers (void)
394 GC_invoke_finalizers ();
398 _Jv_RunAllFinalizers (void)
410 _Jv_GCTotalMemory (void)
412 return GC_get_heap_size ();
416 _Jv_GCFreeMemory (void)
418 return GC_get_free_bytes ();
422 _Jv_GCSetInitialHeapSize (size_t size)
424 size_t current = GC_get_heap_size ();
426 GC_expand_hp (size - current);
430 _Jv_GCSetMaximumHeapSize (size_t size)
432 GC_set_max_heap_size ((GC_word) size);
447 static void * handle_out_of_memory(size_t)
453 gcj_describe_type_fn(void *obj, char *out_buf)
455 _Jv_VTable *dt = *(_Jv_VTable **) obj;
457 if (! dt /* Shouldn't happen */)
459 strcpy(out_buf, "GCJ (bad)");
462 jclass klass = dt->clas;
463 if (!klass /* shouldn't happen */)
465 strcpy(out_buf, "GCJ (bad)");
468 jstring name = klass -> getName();
469 size_t len = name -> length();
470 if (len >= GC_TYPE_DESCR_LEN) len = GC_TYPE_DESCR_LEN - 1;
471 JvGetStringUTFRegion (name, 0, len, out_buf);
479 static bool gc_initialized;
486 // Ignore pointers that do not point to the start of an object.
487 GC_all_interior_pointers = 0;
489 #if defined (HAVE_DLFCN_H) && defined (HAVE_DLADDR)
490 // Tell the collector to ask us before scanning DSOs.
491 GC_register_has_static_roots_callback (_Jv_GC_has_static_roots);
494 // Configure the collector to use the bitmap marking descriptors that we
495 // stash in the class vtable.
496 // We always use mark proc descriptor 0, since the compiler knows
498 GC_init_gcj_malloc (0, (void *) _Jv_MarkObj);
500 // Cause an out of memory error to be thrown from the allocators,
501 // instead of returning 0. This is cheaper than checking on allocation.
502 GC_oom_fn = handle_out_of_memory;
504 GC_java_finalization = 1;
506 // We use a different mark procedure for object arrays. This code
507 // configures a different object `kind' for object array allocation and
509 array_free_list = GC_new_free_list();
510 proc = GC_new_proc((GC_mark_proc)_Jv_MarkArray);
511 array_kind_x = GC_new_kind(array_free_list, GC_MAKE_PROC (proc, 0), 0, 1);
513 // Arrange to have the GC print Java class names in backtraces, etc.
514 GC_register_describe_type_fn(GC_gcj_kind, gcj_describe_type_fn);
515 GC_register_describe_type_fn(GC_gcj_debug_kind, gcj_describe_type_fn);
518 #ifdef JV_HASH_SYNCHRONIZATION
519 // Allocate an object with a fake vtable pointer, which causes only
520 // the first field (beyond the fake vtable pointer) to be traced.
521 // Eventually this should probably be generalized.
523 static _Jv_VTable trace_one_vtable = {
525 (void *)(2 * sizeof(void *)),
526 // descriptor; scan 2 words incl. vtable ptr.
527 // Least significant bits must be zero to
528 // identify this as a length descriptor
533 _Jv_AllocTraceOne (jsize size /* includes vtable slot */)
535 return GC_GCJ_MALLOC (size, &trace_one_vtable);
538 // Ditto for two words.
539 // the first field (beyond the fake vtable pointer) to be traced.
540 // Eventually this should probably be generalized.
542 static _Jv_VTable trace_two_vtable =
545 (void *)(3 * sizeof(void *)),
546 // descriptor; scan 3 words incl. vtable ptr.
551 _Jv_AllocTraceTwo (jsize size /* includes vtable slot */)
553 return GC_GCJ_MALLOC (size, &trace_two_vtable);
556 #endif /* JV_HASH_SYNCHRONIZATION */
559 _Jv_GCInitializeFinalizers (void (*notifier) (void))
561 GC_finalize_on_demand = 1;
562 GC_finalizer_notifier = notifier;
566 _Jv_GCRegisterDisappearingLink (jobject *objp)
568 // This test helps to ensure that we meet a precondition of
569 // GC_general_register_disappearing_link, viz. "Obj must be a
570 // pointer to the first word of an object we allocated."
572 GC_general_register_disappearing_link ((GC_PTR *) objp, (GC_PTR) *objp);
576 _Jv_GCCanReclaimSoftReference (jobject)
578 // For now, always reclaim soft references. FIXME.
584 #if defined (HAVE_DLFCN_H) && defined (HAVE_DLADDR)
586 // We keep a store of the filenames of DSOs that need to be
587 // conservatively scanned by the garbage collector. During collection
588 // the gc calls _Jv_GC_has_static_roots() to see if the data segment
589 // of a DSO should be scanned.
590 typedef struct filename_node
593 struct filename_node *link;
596 #define FILENAME_STORE_SIZE 17
597 static filename_node *filename_store[FILENAME_STORE_SIZE];
599 // Find a filename in filename_store.
600 static filename_node **
601 find_file (const char *filename)
603 int index = strlen (filename) % FILENAME_STORE_SIZE;
604 filename_node **node = &filename_store[index];
608 if (strcmp ((*node)->name, filename) == 0)
610 node = &(*node)->link;
616 // Print the store of filenames of DSOs that need collection.
618 _Jv_print_gc_store (void)
620 for (int i = 0; i < FILENAME_STORE_SIZE; i++)
622 filename_node *node = filename_store[i];
625 fprintf (stderr, "%s\n", node->name);
631 // Create a new node in the store of libraries to collect.
632 static filename_node *
633 new_node (const char *filename)
635 filename_node *node = (filename_node*)_Jv_Malloc (sizeof (filename_node));
636 node->name = (char *)_Jv_Malloc (strlen (filename) + 1);
638 strcpy (node->name, filename);
643 // Nonzero if the gc should scan this lib.
645 _Jv_GC_has_static_roots (const char *filename, void *, size_t)
647 if (filename == NULL || strlen (filename) == 0)
648 // No filename; better safe than sorry.
651 filename_node **node = find_file (filename);
660 // Register the DSO that contains p for collection.
662 _Jv_RegisterLibForGc (const void *p __attribute__ ((__unused__)))
664 #if defined (HAVE_DLFCN_H) && defined (HAVE_DLADDR)
667 if (dladdr (const_cast<void *>(p), &info) != 0)
669 filename_node **node = find_file (info.dli_fname);
671 *node = new_node (info.dli_fname);