1 /*

     2  * Copyright (c) 1999, 2015, 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 "ci/ciField.hpp"

    27 #include "ci/ciInstanceKlass.hpp"

    28 #include "ci/ciUtilities.hpp"

    29 #include "classfile/systemDictionary.hpp"

    30 #include "gc/shared/collectedHeap.inline.hpp"

    31 #include "interpreter/linkResolver.hpp"

    32 #include "memory/universe.inline.hpp"

    33 #include "oops/oop.inline.hpp"

    34 #include "runtime/fieldDescriptor.hpp"

    35 

    36 // ciField

    37 //

    38 // This class represents the result of a field lookup in the VM.

    39 // The lookup may not succeed, in which case the information in

    40 // the ciField will be incomplete.

    41 

    42 // The ciObjectFactory cannot create circular data structures in one query.

    43 // To avoid vicious circularities, we initialize ciField::_type to NULL

    44 // for reference types and derive it lazily from the ciField::_signature.

    45 // Primitive types are eagerly initialized, and basic layout queries

    46 // can succeed without initialization, using only the BasicType of the field.

    47 

    48 // Notes on bootstrapping and shared CI objects:  A field is shared if and

    49 // only if it is (a) non-static and (b) declared by a shared instance klass.

    50 // This allows non-static field lists to be cached on shared types.

    51 // Because the _type field is lazily initialized, however, there is a

    52 // special restriction that a shared field cannot cache an unshared type.

    53 // This puts a small performance penalty on shared fields with unshared

    54 // types, such as StackTraceElement[] Throwable.stackTrace.

    55 // (Throwable is shared because ClassCastException is shared, but

    56 // StackTraceElement is not presently shared.)

    57 

    58 // It is not a vicious circularity for a ciField to recursively create

    59 // the ciSymbols necessary to represent its name and signature.

    60 // Therefore, these items are created eagerly, and the name and signature

    61 // of a shared field are themselves shared symbols.  This somewhat

    62 // pollutes the set of shared CI objects:  It grows from 50 to 93 items,

    63 // with all of the additional 43 being uninteresting shared ciSymbols.

    64 // This adds at most one step to the binary search, an amount which

    65 // decreases for complex compilation tasks.

    66 

    67 // ------------------------------------------------------------------

    68 // ciField::ciField

    69 ciField::ciField(ciInstanceKlass* klass, int index) :

    70     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {

    71   ASSERT_IN_VM;

    72   CompilerThread *thread = CompilerThread::current();

    73 

    74   assert(ciObjectFactory::is_initialized(), "not a shared field");

    75 

    76   assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");

    77 

    78   constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());

    79 

    80   // Get the field's name, signature, and type.

    81   Symbol* name  = cpool->name_ref_at(index);

    82   _name = ciEnv::current(thread)->get_symbol(name);

    83 

    84   int nt_index = cpool->name_and_type_ref_index_at(index);

    85   int sig_index = cpool->signature_ref_index_at(nt_index);

    86   Symbol* signature = cpool->symbol_at(sig_index);

    87   _signature = ciEnv::current(thread)->get_symbol(signature);

    88 

    89   BasicType field_type = FieldType::basic_type(signature);

    90 

    91   // If the field is a pointer type, get the klass of the

    92   // field.

    93   if (field_type == T_OBJECT || field_type == T_ARRAY) {

    94     bool ignore;

    95     // This is not really a class reference; the index always refers to the

    96     // field's type signature, as a symbol.  Linkage checks do not apply.

    97     _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);

    98   } else {

    99     _type = ciType::make(field_type);

   100   }

   101 

   102   _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);

   103 

   104   // Get the field's declared holder.

   105   //

   106   // Note: we actually create a ciInstanceKlass for this klass,

   107   // even though we may not need to.

   108   int holder_index = cpool->klass_ref_index_at(index);

   109   bool holder_is_accessible;

   110 

   111   ciKlass* generic_declared_holder = ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,

   112                                                                                 holder_is_accessible,

   113                                                                                 klass);

   114 

   115   if (generic_declared_holder->is_array_klass()) {

   116     // If the declared holder of the field is an array class, assume that

   117     // the canonical holder of that field is java.lang.Object. Arrays

   118     // do not have fields; java.lang.Object is the only supertype of an

   119     // array type that can declare fields and is therefore the canonical

   120     // holder of the array type.

   121     //

   122     // Furthermore, the compilers assume that java.lang.Object does not

   123     // have any fields. Therefore, the field is not looked up. Instead,

   124     // the method returns partial information that will trigger special

   125     // handling in ciField::will_link and will result in a

   126     // java.lang.NoSuchFieldError exception being thrown by the compiled

   127     // code (the expected behavior in this case).

   128     _holder = ciEnv::current(thread)->Object_klass();

   129     _offset = -1;

   130     _is_constant = false;

   131     return;

   132   }

   133 

   134   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();

   135 

   136   // The declared holder of this field may not have been loaded.

   137   // Bail out with partial field information.

   138   if (!holder_is_accessible) {

   139     // _type has already been set.

   140     // The default values for _flags and _constant_value will suffice.

   141     // We need values for _holder, _offset,  and _is_constant,

   142     _holder = declared_holder;

   143     _offset = -1;

   144     _is_constant = false;

   145     return;

   146   }

   147 

   148   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();

   149 

   150   // Perform the field lookup.

   151   fieldDescriptor field_desc;

   152   Klass* canonical_holder =

   153     loaded_decl_holder->find_field(name, signature, &field_desc);

   154   if (canonical_holder == NULL) {

   155     // Field lookup failed.  Will be detected by will_link.

   156     _holder = declared_holder;

   157     _offset = -1;

   158     _is_constant = false;

   159     return;

   160   }

   161 

   162   // Access check based on declared_holder. canonical_holder should not be used

   163   // to check access because it can erroneously succeed. If this check fails,

   164   // propagate the declared holder to will_link() which in turn will bail out

   165   // compilation for this field access.

   166   if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {

   167     _holder = declared_holder;

   168     _offset = -1;

   169     _is_constant = false;

   170     return;

   171   }

   172 

   173   assert(canonical_holder == field_desc.field_holder(), "just checking");

   174   initialize_from(&field_desc);

   175 }

   176 

   177 ciField::ciField(fieldDescriptor *fd) :

   178     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {

   179   ASSERT_IN_VM;

   180 

   181   // Get the field's name, signature, and type.

   182   ciEnv* env = CURRENT_ENV;

   183   _name = env->get_symbol(fd->name());

   184   _signature = env->get_symbol(fd->signature());

   185 

   186   BasicType field_type = fd->field_type();

   187 

   188   // If the field is a pointer type, get the klass of the

   189   // field.

   190   if (field_type == T_OBJECT || field_type == T_ARRAY) {

   191     _type = NULL;  // must call compute_type on first access

   192   } else {

   193     _type = ciType::make(field_type);

   194   }

   195 

   196   initialize_from(fd);

   197 

   198   // Either (a) it is marked shared, or else (b) we are done bootstrapping.

   199   assert(is_shared() || ciObjectFactory::is_initialized(),

   200          "bootstrap classes must not create & cache unshared fields");

   201 }

   202 

   203 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {

   204   if (holder == NULL)

   205     return false;

   206   if (holder->name() == ciSymbol::java_lang_System())

   207     // Never trust strangely unstable finals:  System.out, etc.

   208     return false;

   209   // Even if general trusting is disabled, trust system-built closures in these packages.

   210   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))

   211     return true;

   212   // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,

   213   // so there is no hacking of finals going on with them.

   214   if (holder->is_anonymous())

   215     return true;

   216   // Trust final fields in all boxed classes

   217   if (holder->is_box_klass())

   218     return true;

   219   // Trust final fields in String

   220   if (holder->name() == ciSymbol::java_lang_String())

   221     return true;

   222   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one

   223   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.

   224   if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||

   225       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||

   226       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||

   227       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {

   228     return true;

   229   }

   230   return TrustFinalNonStaticFields;

   231 }

   232 

   233 void ciField::initialize_from(fieldDescriptor* fd) {

   234   // Get the flags, offset, and canonical holder of the field.

   235   _flags = ciFlags(fd->access_flags());

   236   _offset = fd->offset();

   237   _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());

   238 

   239   // Check to see if the field is constant.

   240   Klass* k = _holder->get_Klass();

   241   bool is_stable_field = FoldStableValues && is_stable();

   242   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {

   243     if (is_static()) {

   244       // This field just may be constant.  The only case where it will

   245       // not be constant is when the field is a *special* static & final field

   246       // whose value may change.  The three examples are java.lang.System.in,

   247       // java.lang.System.out, and java.lang.System.err.

   248       assert(SystemDictionary::System_klass() != NULL, "Check once per vm");

   249       if (k == SystemDictionary::System_klass()) {

   250         // Check offsets for case 2: System.in, System.out, or System.err

   251         if( _offset == java_lang_System::in_offset_in_bytes()  ||

   252             _offset == java_lang_System::out_offset_in_bytes() ||

   253             _offset == java_lang_System::err_offset_in_bytes() ) {

   254           _is_constant = false;

   255           return;

   256         }

   257       }

   258       _is_constant = true;

   259     } else {

   260       // An instance field can be constant if it's a final static field or if

   261       // it's a final non-static field of a trusted class (classes in

   262       // java.lang.invoke and sun.invoke packages and subpackages).

   263       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);

   264     }

   265   } else {

   266     // For CallSite objects treat the target field as a compile time constant.

   267     assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");

   268     if (k == SystemDictionary::CallSite_klass() &&

   269         _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {

   270       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");

   271       _is_constant = true;

   272     } else {

   273       // Non-final & non-stable fields are not constants.

   274       _is_constant = false;

   275     }

   276   }

   277 }

   278 

   279 // ------------------------------------------------------------------

   280 // ciField::constant_value

   281 // Get the constant value of a this static field.

   282 ciConstant ciField::constant_value() {

   283   assert(is_static() && is_constant(), "illegal call to constant_value()");

   284   if (!_holder->is_initialized()) {

   285     return ciConstant(); // Not initialized yet

   286   }

   287   if (_constant_value.basic_type() == T_ILLEGAL) {

   288     // Static fields are placed in mirror objects.

   289     VM_ENTRY_MARK;

   290     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());

   291     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());

   292   }

   293   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {

   294     return ciConstant();

   295   }

   296   return _constant_value;

   297 }

   298 

   299 // ------------------------------------------------------------------

   300 // ciField::constant_value_of

   301 // Get the constant value of non-static final field in the given object.

   302 ciConstant ciField::constant_value_of(ciObject* object) {

   303   assert(!is_static() && is_constant(), "only if field is non-static constant");

   304   assert(object->is_instance(), "must be instance");

   305   ciConstant field_value = object->as_instance()->field_value(this);

   306   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {

   307     return ciConstant();

   308   }

   309   return field_value;

   310 }

   311 

   312 // ------------------------------------------------------------------

   313 // ciField::compute_type

   314 //

   315 // Lazily compute the type, if it is an instance klass.

   316 ciType* ciField::compute_type() {

   317   GUARDED_VM_ENTRY(return compute_type_impl();)

   318 }

   319 

   320 ciType* ciField::compute_type_impl() {

   321   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);

   322   if (!type->is_primitive_type() && is_shared()) {

   323     // We must not cache a pointer to an unshared type, in a shared field.

   324     bool type_is_also_shared = false;

   325     if (type->is_type_array_klass()) {

   326       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped

   327     } else if (type->is_instance_klass()) {

   328       type_is_also_shared = type->as_instance_klass()->is_shared();

   329     } else {

   330       // Currently there is no 'shared' query for array types.

   331       type_is_also_shared = !ciObjectFactory::is_initialized();

   332     }

   333     if (!type_is_also_shared)

   334       return type;              // Bummer.

   335   }

   336   _type = type;

   337   return type;

   338 }

   339 

   340 

   341 // ------------------------------------------------------------------

   342 // ciField::will_link

   343 //

   344 // Can a specific access to this field be made without causing

   345 // link errors?

   346 bool ciField::will_link(ciMethod* accessing_method,

   347                         Bytecodes::Code bc) {

   348   VM_ENTRY_MARK;

   349   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||

   350          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,

   351          "unexpected bytecode");

   352 

   353   if (_offset == -1) {

   354     // at creation we couldn't link to our holder so we need to

   355     // maintain that stance, otherwise there's no safe way to use this

   356     // ciField.

   357     return false;

   358   }

   359 

   360   // Check for static/nonstatic mismatch

   361   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);

   362   if (is_static != this->is_static()) {

   363     return false;

   364   }

   365 

   366   // Get and put can have different accessibility rules

   367   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);

   368   if (is_put) {

   369     if (_known_to_link_with_put == accessing_method) {

   370       return true;

   371     }

   372   } else {

   373     if (_known_to_link_with_get == accessing_method->holder()) {

   374       return true;

   375     }

   376   }

   377 

   378   LinkInfo link_info(_holder->get_instanceKlass(),

   379                      _name->get_symbol(), _signature->get_symbol(),

   380                      accessing_method->get_Method());

   381   fieldDescriptor result;

   382   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));

   383 

   384   // update the hit-cache, unless there is a problem with memory scoping:

   385   if (accessing_method->holder()->is_shared() || !is_shared()) {

   386     if (is_put) {

   387       _known_to_link_with_put = accessing_method;

   388     } else {

   389       _known_to_link_with_get = accessing_method->holder();

   390     }

   391   }

   392 

   393   return true;

   394 }

   395 

   396 // ------------------------------------------------------------------

   397 // ciField::print

   398 void ciField::print() {

   399   tty->print("<ciField name=");

   400   _holder->print_name();

   401   tty->print(".");

   402   _name->print_symbol();

   403   tty->print(" signature=");

   404   _signature->print_symbol();

   405   tty->print(" offset=%d type=", _offset);

   406   if (_type != NULL)

   407     _type->print_name();

   408   else

   409     tty->print("(reference)");

   410   tty->print(" flags=%04x", flags().as_int());

   411   tty->print(" is_constant=%s", bool_to_str(_is_constant));

   412   if (_is_constant && is_static()) {

   413     tty->print(" constant_value=");

   414     _constant_value.print();

   415   }

   416   tty->print(">");

   417 }

   418 

   419 // ------------------------------------------------------------------

   420 // ciField::print_name_on

   421 //

   422 // Print the name of this field

   423 void ciField::print_name_on(outputStream* st) {

   424   name()->print_symbol_on(st);

   425 }