1 /*
  2  * Copyright (c) 1997, 2023, 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 #include "asm/assembler.hpp"
 27 #include "classfile/symbolTable.hpp"
 28 #include "classfile/systemDictionary.hpp"
 29 #include "classfile/vmSymbols.hpp"
 30 #include "memory/oopFactory.hpp"
 31 #include "memory/resourceArea.hpp"
 32 #include "memory/universe.hpp"
 33 #include "oops/instanceKlass.hpp"
 34 #include "oops/klass.inline.hpp"
 35 #include "oops/oop.inline.hpp"
 36 #include "oops/symbol.hpp"
 37 #include "oops/typeArrayKlass.hpp"
 38 #include "runtime/fieldDescriptor.inline.hpp"
 39 #include "runtime/handles.inline.hpp"
 40 #include "runtime/safepointVerifiers.hpp"
 41 #include "runtime/sharedRuntime.hpp"
 42 #include "runtime/signature.hpp"
 43 #include "runtime/sharedRuntime.hpp"
 44 
 45 // Implementation of SignatureIterator
 46 
 47 // Signature syntax:
 48 //
 49 // Signature  = "(" {Parameter} ")" ReturnType.
 50 // Parameter  = FieldType.
 51 // ReturnType = FieldType | "V".
 52 // FieldType  = "B" | "C" | "D" | "F" | "I" | "J" | "S" | "Z" | "L" ClassName ";" | "[" FieldType.
 53 // ClassName  = string.
 54 
 55 // The ClassName string can be any JVM-style UTF8 string except:
 56 //  - an empty string (the empty string is never a name of any kind)
 57 //  - a string which begins or ends with slash '/' (the package separator)
 58 //  - a string which contains adjacent slashes '//' (no empty package names)
 59 //  - a string which contains a semicolon ';' (the end-delimiter)
 60 //  - a string which contains a left bracket '[' (the array marker)
 61 //  - a string which contains a dot '.' (the external package separator)
 62 //
 63 // Other "meta-looking" characters, such as '(' and '<' and '+',
 64 // are perfectly legitimate within a class name, for the JVM.
 65 // Class names which contain double slashes ('a//b') and non-initial
 66 // brackets ('a[b]') are reserved for possible enrichment of the
 67 // type language.
 68 
 69 void SignatureIterator::set_fingerprint(fingerprint_t fingerprint) {
 70   if (!fp_is_valid(fingerprint)) {
 71     _fingerprint = fingerprint;
 72     _return_type = T_ILLEGAL;
 73   } else if (fingerprint != _fingerprint) {
 74     assert(_fingerprint == zero_fingerprint(), "consistent fingerprint values");
 75     _fingerprint = fingerprint;
 76     _return_type = fp_return_type(fingerprint);
 77   }
 78 }
 79 
 80 BasicType SignatureIterator::return_type() {
 81   if (_return_type == T_ILLEGAL) {
 82     SignatureStream ss(_signature);
 83     ss.skip_to_return_type();
 84     _return_type = ss.type();
 85     assert(_return_type != T_ILLEGAL, "illegal return type");
 86   }
 87   return _return_type;
 88 }
 89 
 90 bool SignatureIterator::fp_is_valid_type(BasicType type, bool for_return_type) {
 91   assert(type != (BasicType)fp_parameters_done, "fingerprint is incorrectly at done");
 92   assert(((int)type & ~fp_parameter_feature_mask) == 0, "fingerprint feature mask yielded non-zero value");
 93   return (is_java_primitive(type) ||
 94           is_reference_type(type) ||
 95           (for_return_type && type == T_VOID));
 96 }
 97 
 98 ArgumentSizeComputer::ArgumentSizeComputer(Symbol* signature)
 99   : SignatureIterator(signature)
100 {
101   _size = 0;
102   do_parameters_on(this);  // non-virtual template execution
103 }
104 
105 ArgumentCount::ArgumentCount(Symbol* signature)
106   : SignatureIterator(signature)
107 {
108   _size = 0;
109   do_parameters_on(this);  // non-virtual template execution
110 }
111 
112 ReferenceArgumentCount::ReferenceArgumentCount(Symbol* signature)
113   : SignatureIterator(signature)
114 {
115   _refs = 0;
116   do_parameters_on(this);  // non-virtual template execution
117 }
118 
119 #if !defined(_LP64) || defined(ZERO) || defined(ASSERT)
120 static int compute_num_stack_arg_slots(Symbol* signature, int sizeargs, bool is_static) {
121   ResourceMark rm;
122   BasicType* sig_bt = NEW_RESOURCE_ARRAY(BasicType, sizeargs);
123   VMRegPair* regs   = NEW_RESOURCE_ARRAY(VMRegPair, sizeargs);
124 
125   int sig_index = 0;
126   if (!is_static) {
127     sig_bt[sig_index++] = T_OBJECT; // 'this'
128   }
129   for (SignatureStream ss(signature); !ss.at_return_type(); ss.next()) {
130     BasicType t = ss.type();
131     assert(type2size[t] == 1 || type2size[t] == 2, "size is 1 or 2");
132     sig_bt[sig_index++] = t;
133     if (type2size[t] == 2) {
134       sig_bt[sig_index++] = T_VOID;
135     }
136   }
137   assert(sig_index == sizeargs, "sig_index: %d sizeargs: %d", sig_index, sizeargs);
138 
139   return SharedRuntime::java_calling_convention(sig_bt, regs, sizeargs);
140 }
141 #endif
142 
143 void Fingerprinter::compute_fingerprint_and_return_type(bool static_flag) {
144   // See if we fingerprinted this method already
145   if (_method != nullptr) {
146     assert(!static_flag, "must not be passed by caller");
147     static_flag = _method->is_static();
148     _fingerprint = _method->constMethod()->fingerprint();
149 
150     if (_fingerprint != zero_fingerprint()) {
151       _return_type = _method->result_type();
152       assert(is_java_type(_return_type), "return type must be a java type");
153       return;
154     }
155 
156     if (_method->size_of_parameters() > fp_max_size_of_parameters) {
157       _fingerprint = overflow_fingerprint();
158       _method->constMethod()->set_fingerprint(_fingerprint);
159       // as long as we are here compute the return type:
160       _return_type = ResultTypeFinder(_method->signature()).type();
161       assert(is_java_type(_return_type), "return type must be a java type");
162       return;
163     }
164   }
165 
166   // Note:  This will always take the slow path, since _fp==zero_fp.
167   initialize_accumulator();
168   initialize_calling_convention(static_flag);
169   do_parameters_on(this);
170   assert(fp_is_valid_type(_return_type, true), "bad result type");
171 
172   // Fill in the return type and static bits:
173   _accumulator |= _return_type << fp_static_feature_size;
174   if (static_flag) {
175     _accumulator |= fp_is_static_bit;
176   } else {
177     _param_size += 1;  // this is the convention for Method::compute_size_of_parameters
178   }
179 
180 #if defined(_LP64) && !defined(ZERO)
181 #ifdef ASSERT
182   int dbg_stack_arg_slots = compute_num_stack_arg_slots(_signature, _param_size, static_flag);
183   assert(_stack_arg_slots == dbg_stack_arg_slots, "fingerprinter: %d full: %d", _stack_arg_slots, dbg_stack_arg_slots);
184 #endif
185 #else
186   // Fallback: computed _stack_arg_slots is unreliable, compute directly.
187   _stack_arg_slots = compute_num_stack_arg_slots(_signature, _param_size, static_flag);
188 #endif
189 
190   // Detect overflow.  (We counted _param_size correctly.)
191   if (_method == nullptr && _param_size > fp_max_size_of_parameters) {
192     // We did a one-pass computation of argument size, return type,
193     // and fingerprint.
194     _fingerprint = overflow_fingerprint();
195     return;
196   }
197 
198   assert(_shift_count < BitsPerLong,
199          "shift count overflow %d (%d vs. %d): %s",
200          _shift_count, _param_size, fp_max_size_of_parameters,
201          _signature->as_C_string());
202   assert((_accumulator >> _shift_count) == fp_parameters_done, "must be zero");
203 
204   // This is the result, along with _return_type:
205   _fingerprint = _accumulator;
206 
207   // Cache the result on the method itself:
208   if (_method != nullptr) {
209     _method->constMethod()->set_fingerprint(_fingerprint);
210   }
211 }
212 
213 void Fingerprinter::initialize_calling_convention(bool static_flag) {
214   _int_args = 0;
215   _fp_args = 0;
216 
217   if (!static_flag) { // `this` takes up an int register
218     _int_args++;
219   }
220 }
221 
222 void Fingerprinter::do_type_calling_convention(BasicType type) {
223   // We compute the number of slots for stack-passed arguments in compiled calls.
224   // TODO: SharedRuntime::java_calling_convention is the shared code that knows all details
225   // about the platform-specific calling conventions. This method tries to compute the stack
226   // args number... poorly, at least for 32-bit ports and for zero. Current code has the fallback
227   // that recomputes the stack args number from SharedRuntime::java_calling_convention.
228 #if defined(_LP64) && !defined(ZERO)
229   switch (type) {
230   case T_VOID:
231     break;
232   case T_BOOLEAN:
233   case T_CHAR:
234   case T_BYTE:
235   case T_SHORT:
236   case T_INT:
237     if (_int_args < Argument::n_int_register_parameters_j) {
238       _int_args++;
239     } else {
240 #if defined(PPC64) || defined(S390)
241       _stack_arg_slots += 1;
242 #else
243       _stack_arg_slots = align_up(_stack_arg_slots, 2);
244       _stack_arg_slots += 1;
245 #endif // defined(PPC64) || defined(S390)
246     }
247     break;
248   case T_LONG:
249   case T_OBJECT:
250   case T_ARRAY:
251   case T_ADDRESS:
252     if (_int_args < Argument::n_int_register_parameters_j) {
253       _int_args++;
254     } else {
255       _stack_arg_slots = align_up(_stack_arg_slots, 2);
256       _stack_arg_slots += 2;
257     }
258     break;
259   case T_FLOAT:
260     if (_fp_args < Argument::n_float_register_parameters_j) {
261       _fp_args++;
262     } else {
263 #if defined(PPC64) || defined(S390)
264       _stack_arg_slots += 1;
265 #else
266       _stack_arg_slots = align_up(_stack_arg_slots, 2);
267       _stack_arg_slots += 1;
268 #endif // defined(PPC64) || defined(S390)
269     }
270     break;
271   case T_DOUBLE:
272     if (_fp_args < Argument::n_float_register_parameters_j) {
273       _fp_args++;
274     } else {
275       _stack_arg_slots = align_up(_stack_arg_slots, 2);
276       _stack_arg_slots += 2;
277     }
278     break;
279   default:
280     ShouldNotReachHere();
281     break;
282   }
283 #endif
284 }
285 
286 // Implementation of SignatureStream
287 
288 static inline BasicType decode_signature_char(int ch) {
289   switch (ch) {
290 #define EACH_SIG(ch, bt, ignore) \
291     case ch: return bt;
292     SIGNATURE_TYPES_DO(EACH_SIG, ignore)
293 #undef EACH_SIG
294   }
295   return (BasicType)0;
296 }
297 
298 SignatureStream::SignatureStream(const Symbol* signature,
299                                  bool is_method) {
300   assert(!is_method || signature->starts_with(JVM_SIGNATURE_FUNC),
301          "method signature required");
302   _signature = signature;
303   _limit = signature->utf8_length();
304   int oz = (is_method ? _s_method : _s_field);
305   _state = oz;
306   _begin = _end = oz; // skip first '(' in method signatures
307   _array_prefix = 0;  // just for definiteness
308 
309   // assigning java/lang/Object to _previous_name means we can
310   // avoid a number of null checks in the parser
311   _previous_name = vmSymbols::java_lang_Object();
312   _names = nullptr;
313   next();
314 }
315 
316 SignatureStream::~SignatureStream() {
317   if (_previous_name == vmSymbols::java_lang_Object()) {
318     // no names were created
319     assert(_names == nullptr, "_names unexpectedly created");
320     return;
321   }
322 
323   // decrement refcount for names created during signature parsing
324   _previous_name->decrement_refcount();
325   if (_names != nullptr) {
326     for (int i = 0; i < _names->length(); i++) {
327       _names->at(i)->decrement_refcount();
328     }
329   }
330 }
331 
332 inline int SignatureStream::scan_type(BasicType type) {
333   const u1* base = _signature->bytes();
334   int end = _end;
335   int limit = _limit;
336   const u1* tem;
337   switch (type) {
338   case T_OBJECT:
339     tem = (const u1*) memchr(&base[end], JVM_SIGNATURE_ENDCLASS, limit - end);
340     return (tem == nullptr ? limit : tem + 1 - base);
341 
342   case T_ARRAY:
343     while ((end < limit) && ((char)base[end] == JVM_SIGNATURE_ARRAY)) { end++; }
344     // If we discovered only the string of '[', this means something is wrong.
345     if (end >= limit) {
346       assert(false, "Invalid type detected");
347       return limit;
348     }
349     _array_prefix = end - _end;  // number of '[' chars just skipped
350     if (Signature::has_envelope(base[end])) {
351       tem = (const u1 *) memchr(&base[end], JVM_SIGNATURE_ENDCLASS, limit - end);
352       return (tem == nullptr ? limit : tem + 1 - base);
353     }
354     // Skipping over a single character for a primitive type.
355     assert(is_java_primitive(decode_signature_char(base[end])), "only primitives expected");
356     return end + 1;
357 
358   default:
359     // Skipping over a single character for a primitive type (or void).
360     assert(!is_reference_type(type), "only primitives or void expected");
361     return end + 1;
362   }
363 }
364 
365 void SignatureStream::next() {
366   const Symbol* sig = _signature;
367   int len = _limit;
368   if (_end >= len) { set_done(); return; }
369   _begin = _end;
370   int ch = sig->char_at(_begin);
371   if (ch == JVM_SIGNATURE_ENDFUNC) {
372     assert(_state == _s_method, "must be in method");
373     _state = _s_method_return;
374     _begin = ++_end;
375     if (_end >= len) { set_done(); return; }
376     ch = sig->char_at(_begin);
377   }
378   BasicType bt = decode_signature_char(ch);
379   assert(ch == type2char(bt), "bad signature char %c/%d", ch, ch);
380   _type = bt;
381   _end = scan_type(bt);
382 }
383 
384 int SignatureStream::skip_whole_array_prefix() {
385   assert(_type == T_ARRAY, "must be");
386 
387   // we are stripping all levels of T_ARRAY,
388   // so we must decode the next character
389   int whole_array_prefix = _array_prefix;
390   int new_begin = _begin + whole_array_prefix;
391   _begin = new_begin;
392   int ch = _signature->char_at(new_begin);
393   BasicType bt = decode_signature_char(ch);
394   assert(ch == type2char(bt), "bad signature char %c/%d", ch, ch);
395   _type = bt;
396   assert(bt != T_VOID && bt != T_ARRAY, "bad signature type");
397   // Don't bother to re-scan, since it won't change the value of _end.
398   return whole_array_prefix;
399 }
400 
401 bool Signature::is_valid_array_signature(const Symbol* sig) {
402   assert(sig->utf8_length() > 1, "this should already have been checked");
403   assert(sig->char_at(0) == JVM_SIGNATURE_ARRAY, "this should already have been checked");
404   // The first character is already checked
405   int i = 1;
406   int len = sig->utf8_length();
407   // First skip all '['s
408   while(i < len - 1 && sig->char_at(i) == JVM_SIGNATURE_ARRAY) i++;
409 
410   // Check type
411   switch(sig->char_at(i)) {
412   case JVM_SIGNATURE_BYTE:
413   case JVM_SIGNATURE_CHAR:
414   case JVM_SIGNATURE_DOUBLE:
415   case JVM_SIGNATURE_FLOAT:
416   case JVM_SIGNATURE_INT:
417   case JVM_SIGNATURE_LONG:
418   case JVM_SIGNATURE_SHORT:
419   case JVM_SIGNATURE_BOOLEAN:
420     // If it is an array, the type is the last character
421     return (i + 1 == len);
422   case JVM_SIGNATURE_CLASS:
423     // If it is an object, the last character must be a ';'
424     return sig->char_at(len - 1) == JVM_SIGNATURE_ENDCLASS;
425   }
426   return false;
427 }
428 
429 BasicType Signature::basic_type(int ch) {
430   BasicType btcode = decode_signature_char(ch);
431   if (btcode == 0)  return T_ILLEGAL;
432   return btcode;
433 }
434 
435 Symbol* Signature::strip_envelope(const Symbol* signature) {
436   assert(has_envelope(signature), "precondition");
437   return SymbolTable::new_symbol((char*) signature->bytes() + 1,
438                                  signature->utf8_length() - 2);
439 }
440 
441 static const int jl_len = 10, object_len = 6, jl_object_len = jl_len + object_len;
442 static const char jl_str[] = "java/lang/";
443 
444 #ifdef ASSERT
445 static bool signature_symbols_sane() {
446   static bool done;
447   if (done)  return true;
448   done = true;
449   // test some tense code that looks for common symbol names:
450   assert(vmSymbols::java_lang_Object()->utf8_length() == jl_object_len &&
451          vmSymbols::java_lang_Object()->starts_with(jl_str, jl_len) &&
452          vmSymbols::java_lang_Object()->ends_with("Object", object_len) &&
453          vmSymbols::java_lang_Object()->is_permanent() &&
454          vmSymbols::java_lang_String()->utf8_length() == jl_object_len &&
455          vmSymbols::java_lang_String()->starts_with(jl_str, jl_len) &&
456          vmSymbols::java_lang_String()->ends_with("String", object_len) &&
457          vmSymbols::java_lang_String()->is_permanent(),
458          "sanity");
459   return true;
460 }
461 #endif //ASSERT
462 
463 // returns a symbol; the caller is responsible for decrementing it
464 Symbol* SignatureStream::find_symbol() {
465   // Create a symbol from for string _begin _end
466   int begin = raw_symbol_begin();
467   int end   = raw_symbol_end();
468 
469   const char* symbol_chars = (const char*)_signature->base() + begin;
470   int len = end - begin;
471 
472   // Quick check for common symbols in signatures
473   assert(signature_symbols_sane(), "incorrect signature sanity check");
474   if (len == jl_object_len &&
475       memcmp(symbol_chars, jl_str, jl_len) == 0) {
476     if (memcmp("String", symbol_chars + jl_len, object_len) == 0) {
477       return vmSymbols::java_lang_String();
478     } else if (memcmp("Object", symbol_chars + jl_len, object_len) == 0) {
479       return vmSymbols::java_lang_Object();
480     }
481   }
482 
483   Symbol* name = _previous_name;
484   if (name->equals(symbol_chars, len)) {
485     return name;
486   }
487 
488   // Save names for cleaning up reference count at the end of
489   // SignatureStream scope.
490   name = SymbolTable::new_symbol(symbol_chars, len);
491 
492   // Only allocate the GrowableArray for the _names buffer if more than
493   // one name is being processed in the signature.
494   if (!_previous_name->is_permanent()) {
495     if (_names == nullptr) {
496       _names = new GrowableArray<Symbol*>(10);
497     }
498     _names->push(_previous_name);
499   }
500   _previous_name = name;
501   return name;
502 }
503 
504 Klass* SignatureStream::as_klass(Handle class_loader, Handle protection_domain,
505                                  FailureMode failure_mode, TRAPS) {
506   if (!is_reference()) {
507     return nullptr;
508   }
509   Symbol* name = as_symbol();
510   Klass* k = nullptr;
511   if (failure_mode == ReturnNull) {
512     // Note:  SD::resolve_or_null returns null for most failure modes,
513     // but not all.  Circularity errors, invalid PDs, etc., throw.
514     k = SystemDictionary::resolve_or_null(name, class_loader, protection_domain, CHECK_NULL);
515   } else if (failure_mode == CachedOrNull) {
516     NoSafepointVerifier nsv;  // no loading, now, we mean it!
517     assert(!HAS_PENDING_EXCEPTION, "");
518     k = SystemDictionary::find_instance_klass(THREAD, name, class_loader, protection_domain);
519     // SD::find does not trigger loading, so there should be no throws
520     // Still, bad things can happen, so we CHECK_NULL and ask callers
521     // to do likewise.
522     return k;
523   } else {
524     // The only remaining failure mode is NCDFError.
525     // The test here allows for an additional mode CNFException
526     // if callers need to request the reflective error instead.
527     bool throw_error = (failure_mode == NCDFError);
528     k = SystemDictionary::resolve_or_fail(name, class_loader, protection_domain, throw_error, CHECK_NULL);
529   }
530 
531   return k;
532 }
533 
534 oop SignatureStream::as_java_mirror(Handle class_loader, Handle protection_domain,
535                                     FailureMode failure_mode, TRAPS) {
536   if (!is_reference()) {
537     return Universe::java_mirror(type());
538   }
539   Klass* klass = as_klass(class_loader, protection_domain, failure_mode, CHECK_NULL);
540   if (klass == nullptr) {
541     return nullptr;
542   }
543   return klass->java_mirror();
544 }
545 
546 void SignatureStream::skip_to_return_type() {
547   while (!at_return_type()) {
548     next();
549   }
550 }
551 
552 ResolvingSignatureStream::ResolvingSignatureStream(Symbol* signature,
553                                                    Handle class_loader,
554                                                    Handle protection_domain,
555                                                    bool is_method)
556   : SignatureStream(signature, is_method),
557     _class_loader(class_loader), _protection_domain(protection_domain)
558 {
559   initialize_load_origin(nullptr);
560 }
561 
562 ResolvingSignatureStream::ResolvingSignatureStream(Symbol* signature, Klass* load_origin, bool is_method)
563   : SignatureStream(signature, is_method)
564 {
565   assert(load_origin != nullptr, "");
566   initialize_load_origin(load_origin);
567 }
568 
569 ResolvingSignatureStream::ResolvingSignatureStream(const Method* method)
570   : SignatureStream(method->signature(), true)
571 {
572   initialize_load_origin(method->method_holder());
573 }
574 
575 void ResolvingSignatureStream::cache_handles() {
576   assert(_load_origin != nullptr, "");
577   JavaThread* current = JavaThread::current();
578   _class_loader = Handle(current, _load_origin->class_loader());
579   _protection_domain = Handle(current, _load_origin->protection_domain());
580 }
581 
582 #ifdef ASSERT
583 
584 extern bool signature_constants_sane(); // called from basic_types_init()
585 
586 bool signature_constants_sane() {
587   // for the lookup table, test every 8-bit code point, and then some:
588   for (int i = -256; i <= 256; i++) {
589     int btcode = 0;
590     switch (i) {
591 #define EACH_SIG(ch, bt, ignore) \
592     case ch: { btcode = bt; break; }
593     SIGNATURE_TYPES_DO(EACH_SIG, ignore)
594 #undef EACH_SIG
595     }
596     int btc = decode_signature_char(i);
597     assert(btc == btcode, "misconfigured table: %d => %d not %d", i, btc, btcode);
598   }
599   return true;
600 }
601 
602 bool SignatureVerifier::is_valid_method_signature(Symbol* sig) {
603   const char* method_sig = (const char*)sig->bytes();
604   ssize_t len = sig->utf8_length();
605   ssize_t index = 0;
606   if (method_sig != nullptr && len > 1 && method_sig[index] == JVM_SIGNATURE_FUNC) {
607     ++index;
608     while (index < len && method_sig[index] != JVM_SIGNATURE_ENDFUNC) {
609       ssize_t res = is_valid_type(&method_sig[index], len - index);
610       if (res == -1) {
611         return false;
612       } else {
613         index += res;
614       }
615     }
616     if (index < len && method_sig[index] == JVM_SIGNATURE_ENDFUNC) {
617       // check the return type
618       ++index;
619       return (is_valid_type(&method_sig[index], len - index) == (len - index));
620     }
621   }
622   return false;
623 }
624 
625 bool SignatureVerifier::is_valid_type_signature(Symbol* sig) {
626   const char* type_sig = (const char*)sig->bytes();
627   ssize_t len = sig->utf8_length();
628   return (type_sig != nullptr && len >= 1 &&
629           (is_valid_type(type_sig, len) == len));
630 }
631 
632 // Checks to see if the type (not to go beyond 'limit') refers to a valid type.
633 // Returns -1 if it is not, or the index of the next character that is not part
634 // of the type.  The type encoding may end before 'limit' and that's ok.
635 ssize_t SignatureVerifier::is_valid_type(const char* type, ssize_t limit) {
636   ssize_t index = 0;
637 
638   // Iterate over any number of array dimensions
639   while (index < limit && type[index] == JVM_SIGNATURE_ARRAY) ++index;
640   if (index >= limit) {
641     return -1;
642   }
643   switch (type[index]) {
644     case JVM_SIGNATURE_BYTE:
645     case JVM_SIGNATURE_CHAR:
646     case JVM_SIGNATURE_FLOAT:
647     case JVM_SIGNATURE_DOUBLE:
648     case JVM_SIGNATURE_INT:
649     case JVM_SIGNATURE_LONG:
650     case JVM_SIGNATURE_SHORT:
651     case JVM_SIGNATURE_BOOLEAN:
652     case JVM_SIGNATURE_VOID:
653       return index + 1;
654     case JVM_SIGNATURE_CLASS:
655       for (index = index + 1; index < limit; ++index) {
656         char c = type[index];
657         switch (c) {
658           case JVM_SIGNATURE_ENDCLASS:
659             return index + 1;
660           case '\0': case JVM_SIGNATURE_DOT: case JVM_SIGNATURE_ARRAY:
661             return -1;
662           default: ; // fall through
663         }
664       }
665       // fall through
666     default: ; // fall through
667   }
668   return -1;
669 }
670 
671 #endif // ASSERT