1 /*
   2  * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 
  27 #include "memory/universe.hpp"
  28 #include "oops/oop.inline.hpp"
  29 
  30 #include "classfile/symbolTable.hpp"
  31 #include "classfile/classLoaderData.hpp"
  32 
  33 #include "prims/whitebox.hpp"
  34 #include "prims/wbtestmethods/parserTests.hpp"
  35 
  36 #include "runtime/arguments.hpp"
  37 #include "runtime/interfaceSupport.hpp"
  38 #include "runtime/os.hpp"
  39 #include "utilities/debug.hpp"
  40 #include "utilities/macros.hpp"
  41 #include "utilities/exceptions.hpp"
  42 
  43 #if INCLUDE_ALL_GCS
  44 #include "gc_implementation/g1/concurrentMark.hpp"
  45 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  46 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  47 #endif // INCLUDE_ALL_GCS
  48 
  49 #ifdef INCLUDE_NMT
  50 #include "services/memTracker.hpp"
  51 #endif // INCLUDE_NMT
  52 
  53 #include "compiler/compileBroker.hpp"
  54 #include "runtime/compilationPolicy.hpp"
  55 
  56 bool WhiteBox::_used = false;
  57 
  58 WB_ENTRY(jlong, WB_GetObjectAddress(JNIEnv* env, jobject o, jobject obj))
  59   return (jlong)(void*)JNIHandles::resolve(obj);
  60 WB_END
  61 
  62 WB_ENTRY(jint, WB_GetHeapOopSize(JNIEnv* env, jobject o))
  63   return heapOopSize;
  64 WB_END
  65 
  66 
  67 class WBIsKlassAliveClosure : public KlassClosure {
  68     Symbol* _name;
  69     bool _found;
  70 public:
  71     WBIsKlassAliveClosure(Symbol* name) : _name(name), _found(false) {}
  72 
  73     void do_klass(Klass* k) {
  74       if (_found) return;
  75       Symbol* ksym = k->name();
  76       if (ksym->fast_compare(_name) == 0) {
  77         _found = true;
  78       }
  79     }
  80 
  81     bool found() const {
  82         return _found;
  83     }
  84 };
  85 
  86 WB_ENTRY(jboolean, WB_IsClassAlive(JNIEnv* env, jobject target, jstring name))
  87   Handle h_name = JNIHandles::resolve(name);
  88   if (h_name.is_null()) return false;
  89   Symbol* sym = java_lang_String::as_symbol(h_name, CHECK_false);
  90   TempNewSymbol tsym(sym); // Make sure to decrement reference count on sym on return
  91 
  92   WBIsKlassAliveClosure closure(sym);
  93   ClassLoaderDataGraph::classes_do(&closure);
  94 
  95   return closure.found();
  96 WB_END
  97 
  98 WB_ENTRY(void, WB_PrintCompressedOopsHeapInfo(JNIEnv* env, jobject o)) {
  99   gclog_or_tty->print_cr("Max heap for compressed oops "SIZE_FORMAT" ClassMetaspaceSize "SIZE_FORMAT,
 100     Arguments::max_heap_for_compressed_oops(), ClassMetaspaceSize);
 101 }
 102 WB_END
 103 
 104 WB_ENTRY(void, WB_PrintHeapSizes(JNIEnv* env, jobject o)) {
 105   CollectorPolicy * p = Universe::heap()->collector_policy();
 106   gclog_or_tty->print_cr("Minimum heap "SIZE_FORMAT" Initial heap "
 107     SIZE_FORMAT" Maximum heap "SIZE_FORMAT" Min alignment "SIZE_FORMAT" Max alignment "SIZE_FORMAT,
 108     p->min_heap_byte_size(), p->initial_heap_byte_size(), p->max_heap_byte_size(),
 109     p->min_alignment(), p->max_alignment());
 110 }
 111 WB_END
 112 
 113 #if INCLUDE_ALL_GCS
 114 WB_ENTRY(jboolean, WB_G1IsHumongous(JNIEnv* env, jobject o, jobject obj))
 115   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 116   oop result = JNIHandles::resolve(obj);
 117   const HeapRegion* hr = g1->heap_region_containing(result);
 118   return hr->isHumongous();
 119 WB_END
 120 
 121 WB_ENTRY(jlong, WB_G1NumFreeRegions(JNIEnv* env, jobject o))
 122   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 123   size_t nr = g1->free_regions();
 124   return (jlong)nr;
 125 WB_END
 126 
 127 WB_ENTRY(jboolean, WB_G1InConcurrentMark(JNIEnv* env, jobject o))
 128   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 129   ConcurrentMark* cm = g1->concurrent_mark();
 130   return cm->concurrent_marking_in_progress();
 131 WB_END
 132 
 133 WB_ENTRY(jint, WB_G1RegionSize(JNIEnv* env, jobject o))
 134   return (jint)HeapRegion::GrainBytes;
 135 WB_END
 136 #endif // INCLUDE_ALL_GCS
 137 
 138 #ifdef INCLUDE_NMT
 139 // Alloc memory using the test memory type so that we can use that to see if
 140 // NMT picks it up correctly
 141 WB_ENTRY(jlong, WB_NMTMalloc(JNIEnv* env, jobject o, jlong size))
 142   jlong addr = 0;
 143 
 144   if (MemTracker::is_on() && !MemTracker::shutdown_in_progress()) {
 145     addr = (jlong)(uintptr_t)os::malloc(size, mtTest);
 146   }
 147 
 148   return addr;
 149 WB_END
 150 
 151 // Free the memory allocated by NMTAllocTest
 152 WB_ENTRY(void, WB_NMTFree(JNIEnv* env, jobject o, jlong mem))
 153   os::free((void*)(uintptr_t)mem, mtTest);
 154 WB_END
 155 
 156 WB_ENTRY(jlong, WB_NMTReserveMemory(JNIEnv* env, jobject o, jlong size))
 157   jlong addr = 0;
 158 
 159   if (MemTracker::is_on() && !MemTracker::shutdown_in_progress()) {
 160     addr = (jlong)(uintptr_t)os::reserve_memory(size);
 161     MemTracker::record_virtual_memory_type((address)addr, mtTest);
 162   }
 163 
 164   return addr;
 165 WB_END
 166 
 167 
 168 WB_ENTRY(void, WB_NMTCommitMemory(JNIEnv* env, jobject o, jlong addr, jlong size))
 169   os::commit_memory((char *)(uintptr_t)addr, size);
 170   MemTracker::record_virtual_memory_type((address)(uintptr_t)addr, mtTest);
 171 WB_END
 172 
 173 WB_ENTRY(void, WB_NMTUncommitMemory(JNIEnv* env, jobject o, jlong addr, jlong size))
 174   os::uncommit_memory((char *)(uintptr_t)addr, size);
 175 WB_END
 176 
 177 WB_ENTRY(void, WB_NMTReleaseMemory(JNIEnv* env, jobject o, jlong addr, jlong size))
 178   os::release_memory((char *)(uintptr_t)addr, size);
 179 WB_END
 180 
 181 // Block until the current generation of NMT data to be merged, used to reliably test the NMT feature
 182 WB_ENTRY(jboolean, WB_NMTWaitForDataMerge(JNIEnv* env))
 183 
 184   if (!MemTracker::is_on() || MemTracker::shutdown_in_progress()) {
 185     return false;
 186   }
 187 
 188   return MemTracker::wbtest_wait_for_data_merge();
 189 WB_END
 190 
 191 #endif // INCLUDE_NMT
 192 
 193 static jmethodID reflected_method_to_jmid(JavaThread* thread, JNIEnv* env, jobject method) {
 194   assert(method != NULL, "method should not be null");
 195   ThreadToNativeFromVM ttn(thread);
 196   return env->FromReflectedMethod(method);
 197 }
 198 
 199 WB_ENTRY(void, WB_DeoptimizeAll(JNIEnv* env, jobject o))
 200   MutexLockerEx mu(Compile_lock);
 201   CodeCache::mark_all_nmethods_for_deoptimization();
 202   VM_Deoptimize op;
 203   VMThread::execute(&op);
 204 WB_END
 205 
 206 WB_ENTRY(jint, WB_DeoptimizeMethod(JNIEnv* env, jobject o, jobject method))
 207   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 208   MutexLockerEx mu(Compile_lock);
 209   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 210   int result = 0;
 211   nmethod* code = mh->code();
 212   if (code != NULL) {
 213     code->mark_for_deoptimization();
 214     ++result;
 215   }
 216   result += CodeCache::mark_for_deoptimization(mh());
 217   if (result > 0) {
 218     VM_Deoptimize op;
 219     VMThread::execute(&op);
 220   }
 221   return result;
 222 WB_END
 223 
 224 WB_ENTRY(jboolean, WB_IsMethodCompiled(JNIEnv* env, jobject o, jobject method))
 225   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 226   MutexLockerEx mu(Compile_lock);
 227   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 228   nmethod* code = mh->code();
 229   if (code == NULL) {
 230     return JNI_FALSE;
 231   }
 232   return (code->is_alive() && !code->is_marked_for_deoptimization());
 233 WB_END
 234 
 235 WB_ENTRY(jboolean, WB_IsMethodCompilable(JNIEnv* env, jobject o, jobject method, jint comp_level))
 236   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 237   MutexLockerEx mu(Compile_lock);
 238   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 239   return CompilationPolicy::can_be_compiled(mh, comp_level);
 240 WB_END
 241 
 242 WB_ENTRY(jboolean, WB_IsMethodQueuedForCompilation(JNIEnv* env, jobject o, jobject method))
 243   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 244   MutexLockerEx mu(Compile_lock);
 245   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 246   return mh->queued_for_compilation();
 247 WB_END
 248 
 249 WB_ENTRY(jint, WB_GetMethodCompilationLevel(JNIEnv* env, jobject o, jobject method))
 250   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 251   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 252   nmethod* code = mh->code();
 253   return (code != NULL ? code->comp_level() : CompLevel_none);
 254 WB_END
 255 
 256 
 257 WB_ENTRY(void, WB_MakeMethodNotCompilable(JNIEnv* env, jobject o, jobject method, jint comp_level))
 258   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 259   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 260   mh->set_not_compilable(comp_level, true /* report */, "WhiteBox");
 261 WB_END
 262 
 263 WB_ENTRY(jboolean, WB_TestSetDontInlineMethod(JNIEnv* env, jobject o, jobject method, jboolean value))
 264   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 265   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 266   bool result = mh->dont_inline();
 267   mh->set_dont_inline(value == JNI_TRUE);
 268   return result;
 269 WB_END
 270 
 271 WB_ENTRY(jint, WB_GetCompileQueuesSize(JNIEnv* env, jobject o))
 272   return CompileBroker::queue_size(CompLevel_full_optimization) /* C2 */ +
 273          CompileBroker::queue_size(CompLevel_full_profile) /* C1 */;
 274 WB_END
 275 
 276 
 277 WB_ENTRY(jboolean, WB_TestSetForceInlineMethod(JNIEnv* env, jobject o, jobject method, jboolean value))
 278   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 279   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 280   bool result = mh->force_inline();
 281   mh->set_force_inline(value == JNI_TRUE);
 282   return result;
 283 WB_END
 284 
 285 WB_ENTRY(jboolean, WB_EnqueueMethodForCompilation(JNIEnv* env, jobject o, jobject method, jint comp_level))
 286   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 287   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 288   nmethod* nm = CompileBroker::compile_method(mh, InvocationEntryBci, comp_level, mh, mh->invocation_count(), "WhiteBox", THREAD);
 289   MutexLockerEx mu(Compile_lock);
 290   return (mh->queued_for_compilation() || nm != NULL);
 291 WB_END
 292 
 293 WB_ENTRY(void, WB_ClearMethodState(JNIEnv* env, jobject o, jobject method))
 294   jmethodID jmid = reflected_method_to_jmid(thread, env, method);
 295   methodHandle mh(THREAD, Method::checked_resolve_jmethod_id(jmid));
 296   MutexLockerEx mu(Compile_lock);
 297   MethodData* mdo = mh->method_data();
 298   MethodCounters* mcs = mh->method_counters();
 299 
 300   if (mdo != NULL) {
 301     mdo->init();
 302     ResourceMark rm;
 303     int arg_count = mdo->method()->size_of_parameters();
 304     for (int i = 0; i < arg_count; i++) {
 305       mdo->set_arg_modified(i, 0);
 306     }
 307   }
 308 
 309   mh->clear_not_c1_compilable();
 310   mh->clear_not_c2_compilable();
 311   mh->clear_not_c2_osr_compilable();
 312   NOT_PRODUCT(mh->set_compiled_invocation_count(0));
 313   if (mcs != NULL) {
 314     mcs->backedge_counter()->init();
 315     mcs->invocation_counter()->init();
 316     mcs->set_interpreter_invocation_count(0);
 317     mcs->set_interpreter_throwout_count(0);
 318 
 319 #ifdef TIERED
 320     mcs->set_rate(0.0F);
 321     mh->set_prev_event_count(0, THREAD);
 322     mh->set_prev_time(0, THREAD);
 323 #endif
 324   }
 325 WB_END
 326 
 327 WB_ENTRY(jboolean, WB_IsInStringTable(JNIEnv* env, jobject o, jstring javaString))
 328   ResourceMark rm(THREAD);
 329   int len;
 330   jchar* name = java_lang_String::as_unicode_string(JNIHandles::resolve(javaString), len, CHECK_false);
 331   return (StringTable::lookup(name, len) != NULL);
 332 WB_END
 333 
 334 
 335 WB_ENTRY(void, WB_FullGC(JNIEnv* env, jobject o))
 336   Universe::heap()->collector_policy()->set_should_clear_all_soft_refs(true);
 337   Universe::heap()->collect(GCCause::_last_ditch_collection);
 338 WB_END
 339 
 340 
 341 WB_ENTRY(void, WB_ReadReservedMemory(JNIEnv* env, jobject o))
 342   // static+volatile in order to force the read to happen
 343   // (not be eliminated by the compiler)
 344   static char c;
 345   static volatile char* p;
 346 
 347   p = os::reserve_memory(os::vm_allocation_granularity(), NULL, 0);
 348   if (p == NULL) {
 349     THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(), "Failed to reserve memory");
 350   }
 351 
 352   c = *p;
 353 WB_END
 354 
 355 //Some convenience methods to deal with objects from java
 356 int WhiteBox::offset_for_field(const char* field_name, oop object,
 357     Symbol* signature_symbol) {
 358   assert(field_name != NULL && strlen(field_name) > 0, "Field name not valid");
 359   Thread* THREAD = Thread::current();
 360 
 361   //Get the class of our object
 362   Klass* arg_klass = object->klass();
 363   //Turn it into an instance-klass
 364   InstanceKlass* ik = InstanceKlass::cast(arg_klass);
 365 
 366   //Create symbols to look for in the class
 367   TempNewSymbol name_symbol = SymbolTable::lookup(field_name, (int) strlen(field_name),
 368       THREAD);
 369 
 370   //To be filled in with an offset of the field we're looking for
 371   fieldDescriptor fd;
 372 
 373   Klass* res = ik->find_field(name_symbol, signature_symbol, &fd);
 374   if (res == NULL) {
 375     tty->print_cr("Invalid layout of %s at %s", ik->external_name(),
 376         name_symbol->as_C_string());
 377     fatal("Invalid layout of preloaded class");
 378   }
 379 
 380   //fetch the field at the offset we've found
 381   int dest_offset = fd.offset();
 382 
 383   return dest_offset;
 384 }
 385 
 386 
 387 const char* WhiteBox::lookup_jstring(const char* field_name, oop object) {
 388   int offset = offset_for_field(field_name, object,
 389       vmSymbols::string_signature());
 390   oop string = object->obj_field(offset);
 391   if (string == NULL) {
 392     return NULL;
 393   }
 394   const char* ret = java_lang_String::as_utf8_string(string);
 395   return ret;
 396 }
 397 
 398 bool WhiteBox::lookup_bool(const char* field_name, oop object) {
 399   int offset =
 400       offset_for_field(field_name, object, vmSymbols::bool_signature());
 401   bool ret = (object->bool_field(offset) == JNI_TRUE);
 402   return ret;
 403 }
 404 
 405 
 406 #define CC (char*)
 407 
 408 static JNINativeMethod methods[] = {
 409   {CC"getObjectAddress",   CC"(Ljava/lang/Object;)J", (void*)&WB_GetObjectAddress  },
 410   {CC"getHeapOopSize",     CC"()I",                   (void*)&WB_GetHeapOopSize    },
 411   {CC"isClassAlive0",      CC"(Ljava/lang/String;)Z", (void*)&WB_IsClassAlive      },
 412   {CC"parseCommandLine",
 413       CC"(Ljava/lang/String;[Lsun/hotspot/parser/DiagnosticCommand;)[Ljava/lang/Object;",
 414       (void*) &WB_ParseCommandLine
 415   },
 416   {CC"printCompressedOopsHeapInfo",
 417       CC"()V",
 418       (void*)&WB_PrintCompressedOopsHeapInfo},
 419   {CC"printHeapSizes",     CC"()V",                   (void*)&WB_PrintHeapSizes    },
 420 #if INCLUDE_ALL_GCS
 421   {CC"g1InConcurrentMark", CC"()Z",                   (void*)&WB_G1InConcurrentMark},
 422   {CC"g1IsHumongous",      CC"(Ljava/lang/Object;)Z", (void*)&WB_G1IsHumongous     },
 423   {CC"g1NumFreeRegions",   CC"()J",                   (void*)&WB_G1NumFreeRegions  },
 424   {CC"g1RegionSize",       CC"()I",                   (void*)&WB_G1RegionSize      },
 425 #endif // INCLUDE_ALL_GCS
 426 #ifdef INCLUDE_NMT
 427   {CC"NMTMalloc",           CC"(J)J",                 (void*)&WB_NMTMalloc          },
 428   {CC"NMTFree",             CC"(J)V",                 (void*)&WB_NMTFree            },
 429   {CC"NMTReserveMemory",    CC"(J)J",                 (void*)&WB_NMTReserveMemory   },
 430   {CC"NMTCommitMemory",     CC"(JJ)V",                (void*)&WB_NMTCommitMemory    },
 431   {CC"NMTUncommitMemory",   CC"(JJ)V",                (void*)&WB_NMTUncommitMemory  },
 432   {CC"NMTReleaseMemory",    CC"(JJ)V",                (void*)&WB_NMTReleaseMemory   },
 433   {CC"NMTWaitForDataMerge", CC"()Z",                  (void*)&WB_NMTWaitForDataMerge},
 434 #endif // INCLUDE_NMT
 435   {CC"deoptimizeAll",      CC"()V",                   (void*)&WB_DeoptimizeAll     },
 436   {CC"deoptimizeMethod",   CC"(Ljava/lang/reflect/Executable;)I",
 437                                                       (void*)&WB_DeoptimizeMethod  },
 438   {CC"isMethodCompiled",   CC"(Ljava/lang/reflect/Executable;)Z",
 439                                                       (void*)&WB_IsMethodCompiled  },
 440   {CC"isMethodCompilable", CC"(Ljava/lang/reflect/Executable;I)Z",
 441                                                       (void*)&WB_IsMethodCompilable},
 442   {CC"isMethodQueuedForCompilation",
 443       CC"(Ljava/lang/reflect/Executable;)Z",          (void*)&WB_IsMethodQueuedForCompilation},
 444   {CC"makeMethodNotCompilable",
 445       CC"(Ljava/lang/reflect/Executable;I)V",         (void*)&WB_MakeMethodNotCompilable},
 446   {CC"testSetDontInlineMethod",
 447       CC"(Ljava/lang/reflect/Executable;Z)Z",         (void*)&WB_TestSetDontInlineMethod},
 448   {CC"getMethodCompilationLevel",
 449       CC"(Ljava/lang/reflect/Executable;)I",          (void*)&WB_GetMethodCompilationLevel},
 450   {CC"getCompileQueuesSize",
 451       CC"()I",                                        (void*)&WB_GetCompileQueuesSize},
 452   {CC"testSetForceInlineMethod",
 453       CC"(Ljava/lang/reflect/Executable;Z)Z",         (void*)&WB_TestSetForceInlineMethod},
 454   {CC"enqueueMethodForCompilation",
 455       CC"(Ljava/lang/reflect/Executable;I)Z",         (void*)&WB_EnqueueMethodForCompilation},
 456   {CC"clearMethodState",
 457       CC"(Ljava/lang/reflect/Executable;)V",          (void*)&WB_ClearMethodState},
 458   {CC"isInStringTable",   CC"(Ljava/lang/String;)Z",  (void*)&WB_IsInStringTable  },
 459   {CC"fullGC",   CC"()V",                             (void*)&WB_FullGC },
 460 
 461   {CC"readReservedMemory", CC"()V",                   (void*)&WB_ReadReservedMemory },
 462 };
 463 
 464 #undef CC
 465 
 466 JVM_ENTRY(void, JVM_RegisterWhiteBoxMethods(JNIEnv* env, jclass wbclass))
 467   {
 468     if (WhiteBoxAPI) {
 469       // Make sure that wbclass is loaded by the null classloader
 470       instanceKlassHandle ikh = instanceKlassHandle(JNIHandles::resolve(wbclass)->klass());
 471       Handle loader(ikh->class_loader());
 472       if (loader.is_null()) {
 473         ResourceMark rm;
 474         ThreadToNativeFromVM ttnfv(thread); // can't be in VM when we call JNI
 475         bool result = true;
 476         //  one by one registration natives for exception catching
 477         jclass exceptionKlass = env->FindClass(vmSymbols::java_lang_NoSuchMethodError()->as_C_string());
 478         for (int i = 0, n = sizeof(methods) / sizeof(methods[0]); i < n; ++i) {
 479           if (env->RegisterNatives(wbclass, methods + i, 1) != 0) {
 480             result = false;
 481             if (env->ExceptionCheck() && env->IsInstanceOf(env->ExceptionOccurred(), exceptionKlass)) {
 482               // j.l.NoSuchMethodError is thrown when a method can't be found or a method is not native
 483               // ignoring the exception
 484               tty->print_cr("Warning: 'NoSuchMethodError' on register of sun.hotspot.WhiteBox::%s%s", methods[i].name, methods[i].signature);
 485               env->ExceptionClear();
 486             } else {
 487               // register is failed w/o exception or w/ unexpected exception
 488               tty->print_cr("Warning: unexpected error on register of sun.hotspot.WhiteBox::%s%s. All methods will be unregistered", methods[i].name, methods[i].signature);
 489               env->UnregisterNatives(wbclass);
 490               break;
 491             }
 492           }
 493         }
 494 
 495         if (result) {
 496           WhiteBox::set_used();
 497         }
 498       }
 499     }
 500   }
 501 JVM_END