1 /*
  2  * Copyright (c) 2011, 2025, 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.
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 23  */
 24 
 25 #ifndef SHARE_OOPS_FIELDINFO_HPP
 26 #define SHARE_OOPS_FIELDINFO_HPP
 27 
 28 #include "memory/allocation.hpp"
 29 #include "oops/typeArrayOop.hpp"
 30 #include "utilities/unsigned5.hpp"
 31 #include "utilities/vmEnums.hpp"
 32 
 33 static constexpr u4 flag_mask(int pos) {
 34   return (u4)1 << pos;
 35 }
 36 
 37 
 38 // Helper class for access to the underlying Array<u1> used to
 39 // store the compressed stream of FieldInfo
 40 template<typename ARR, typename OFF>
 41 struct ArrayHelper {
 42   uint8_t operator()(ARR a, OFF i) const { return a->at(i); };
 43   void operator()(ARR a, OFF i, uint8_t b) const { a->at_put(i,b); };
 44   // So, an expression ArrayWriterHelper() acts like these lambdas:
 45   // auto get = [&](ARR a, OFF i){ return a[i]; };
 46   // auto set = [&](ARR a, OFF i, uint8_t x){ a[i] = x; };
 47 };
 48 
 49 // This class represents the field information contained in the fields
 50 // array of an InstanceKlass.  Currently it's laid on top an array of
 51 // Java shorts but in the future it could simply be used as a real
 52 // array type.  FieldInfo generally shouldn't be used directly.
 53 // Fields should be queried either through InstanceKlass or through
 54 // the various FieldStreams.
 55 class FieldInfo {
 56   friend class fieldDescriptor;
 57   friend class JavaFieldStream;
 58   friend class ClassFileParser;
 59   friend class FieldInfoStream;
 60   friend class FieldStreamBase;
 61   friend class FieldInfoReader;
 62   friend class VMStructs;
 63 
 64  public:
 65 
 66   class FieldFlags {
 67     friend class VMStructs;
 68     friend class JVMCIVMStructs;
 69 
 70     // The ordering of this enum is totally internal.  More frequent
 71     // flags should come earlier than less frequent ones, because
 72     // earlier ones compress better.
 73     enum FieldFlagBitPosition {
 74       _ff_initialized,  // has ConstantValue initializer attribute
 75       _ff_injected,     // internal field injected by the JVM
 76       _ff_generic,      // has a generic signature
 77       _ff_stable,       // trust as stable b/c declared as @Stable
 78       _ff_contended,    // is contended, may have contention-group
 79     };
 80 
 81     // Some but not all of the flag bits signal the presence of an
 82     // additional 32-bit item in the field record.
 83     static const u4 _optional_item_bit_mask =
 84       flag_mask((int)_ff_initialized) |
 85       flag_mask((int)_ff_generic)     |
 86       flag_mask((int)_ff_contended);
 87 
 88     // boilerplate:
 89     u4 _flags;
 90 
 91     bool test_flag(FieldFlagBitPosition pos) const {
 92       return (_flags & flag_mask(pos)) != 0;
 93     }
 94     void update_flag(FieldFlagBitPosition pos, bool z) {
 95       if (z)    _flags |=  flag_mask(pos);
 96       else      _flags &= ~flag_mask(pos);
 97     }
 98 
 99    public:
100     FieldFlags(u4 flags) {
101       _flags = flags;
102     }
103     u4 as_uint() const { return _flags; }
104     bool has_any_optionals() const {
105       return (_flags & _optional_item_bit_mask) != 0;
106     }
107 
108     bool is_initialized() const     { return test_flag(_ff_initialized); }
109     bool is_injected() const        { return test_flag(_ff_injected); }
110     bool is_generic() const         { return test_flag(_ff_generic); }
111     bool is_stable() const          { return test_flag(_ff_stable); }
112     bool is_contended() const       { return test_flag(_ff_contended); }
113 
114     void update_initialized(bool z) { update_flag(_ff_initialized, z); }
115     void update_injected(bool z)    { update_flag(_ff_injected, z); }
116     void update_generic(bool z)     { update_flag(_ff_generic, z); }
117     void update_stable(bool z)      { update_flag(_ff_stable, z); }
118     void update_contended(bool z)   { update_flag(_ff_contended, z); }
119   };
120 
121  private:
122   // The following items are the unpacked bitwise information content
123   // of a field record.  Per-field metadata extracted from the class
124   // file are stored logically as a group of these items.  The
125   // classfile parser produces these records in a temporary array, and
126   // then compresses them into a FieldInfoStream.
127   //
128   u4 _index;                    // which field it is
129   u2 _name_index;               // index in CP of name
130   u2 _signature_index;          // index in CP of descriptor
131   u4 _offset;                   // offset in object layout
132   AccessFlags _access_flags;    // access flags (JVM spec)
133   FieldFlags _field_flags;      // VM defined flags (not JVM spec)
134   u2 _initializer_index;        // index from ConstantValue attr (or 0)
135   u2 _generic_signature_index;  // index from GenericSignature attr (or 0)
136   u2 _contention_group;         // index from @Contended group item (or 0)
137 
138  public:
139 
140   FieldInfo() : _index(0),
141                 _name_index(0),
142                 _signature_index(0),
143                 _offset(0),
144                 _access_flags(AccessFlags(0)),
145                 _field_flags(FieldFlags(0)),
146                 _initializer_index(0),
147                 _generic_signature_index(0),
148                 _contention_group(0) { }
149 
150   FieldInfo(AccessFlags access_flags, u2 name_index, u2 signature_index, u2 initval_index, FieldInfo::FieldFlags fflags) :
151             _index(0),
152             _name_index(name_index),
153             _signature_index(signature_index),
154             _offset(0),
155             _access_flags(access_flags),
156             _field_flags(fflags),
157             _initializer_index(initval_index),
158             _generic_signature_index(0),
159             _contention_group(0) {
160               if (initval_index != 0) {
161                 _field_flags.update_initialized(true);
162               }
163             }
164 
165   u4 index() const                           { return _index; }
166   void set_index(u4 index)                   { _index = index; }
167   u2 name_index() const                      { return _name_index; }
168   void set_name_index(u2 index)              { _name_index = index; }
169   u2 signature_index() const                 { return _signature_index; }
170   void set_signature_index(u2 index)         { _signature_index = index; }
171   u4 offset() const                          { return _offset; }
172   void set_offset(u4 offset)                 { _offset = offset; }
173   AccessFlags access_flags() const           { return _access_flags; }
174   FieldFlags field_flags() const             { return _field_flags; }
175   FieldFlags* field_flags_addr()             { return &_field_flags; }
176   u2 initializer_index() const               { return _initializer_index; }
177   void set_initializer_index(u2 index)       { _initializer_index = index; }
178   u2 generic_signature_index() const         { return _generic_signature_index; }
179   void set_generic_signature_index(u2 index) { _generic_signature_index = index; }
180   u2 contention_group() const                { return _contention_group; }
181 
182   bool is_contended() const {
183     return _field_flags.is_contended();
184   }
185 
186   u2 contended_group() const {
187     assert(is_contended(), "");
188     return _contention_group;
189   }
190 
191   void set_contended_group(u2 group) {
192     _field_flags.update_contended(true);
193     _contention_group = group;
194   }
195 
196   bool is_offset_set() const {
197     return _offset != 0;
198   }
199 
200   inline Symbol* name(ConstantPool* cp) const;
201 
202   inline Symbol* signature(ConstantPool* cp) const;
203 
204   inline Symbol* lookup_symbol(int symbol_index) const;
205 
206   void print(outputStream* os, ConstantPool* cp);
207   void static print_from_growable_array(outputStream* os, GrowableArray<FieldInfo>* array, ConstantPool* cp);
208 };
209 
210 class FieldInfoStream;
211 
212 // Gadget for sizing and/or writing a stream of field records.
213 template<typename CON>
214 class Mapper {
215   CON* _consumer;  // can be UNSIGNED5::Writer or UNSIGNED5::Sizer
216   int _next_index;
217 public:
218   Mapper(CON* consumer) : _consumer(consumer) { _next_index = 0; }
219   int next_index() const { return _next_index; }
220   void set_next_index(int next_index) { _next_index = next_index; }
221   CON* consumer() const { return _consumer; }
222   void map_field_info(const FieldInfo& fi);
223 };
224 
225 // Gadget for decoding and reading the stream of field records.
226 class FieldInfoReader {
227   UNSIGNED5::Reader<const u1*, int> _r;
228   int _next_index;
229 
230 public:
231   FieldInfoReader(const Array<u1>* fi);
232 
233 private:
234   inline uint32_t next_uint() { return _r.next_uint(); }
235   void skip(int n) { int s = _r.try_skip(n); assert(s == n,""); }
236 
237 public:
238   void read_field_counts(int* java_fields, int* injected_fields);
239   int has_next() const { return _r.position() < _r.limit(); }
240   int position() const { return _r.position(); }
241   int next_index() const { return _next_index; }
242   void read_name_and_signature(u2* name_index, u2* signature_index);
243   void read_field_info(FieldInfo& fi);
244 
245   int search_table_lookup(const Array<u1>* search_table, const Symbol* name, const Symbol* signature, ConstantPool* cp, int java_fields);
246 
247   // skip a whole field record, both required and optional bits
248   FieldInfoReader&  skip_field_info();
249 
250   // Skip to the nth field.  If the reader is freshly initialized to
251   // the zero index, this will call skip_field_info() n times.
252   FieldInfoReader& skip_to_field_info(int n);
253 
254   // for random access, if you know where to go up front:
255   FieldInfoReader& set_position_and_next_index(int position, int next_index);
256 };
257 
258 // The format of the stream, after decompression, is a series of
259 // integers organized like this:
260 //
261 //   FieldInfoStream := j=num_java_fields k=num_injected_fields Field[j+k] End
262 //   Field := name sig offset access flags Optionals(flags)
263 //   Optionals(i) := initval?[i&is_init]     // ConstantValue attr
264 //                   gsig?[i&is_generic]     // signature attr
265 //                   group?[i&is_contended]  // Contended anno (group)
266 //   End = 0
267 //
268 class FieldInfoStream : AllStatic {
269   friend class fieldDescriptor;
270   friend class JavaFieldStream;
271   friend class FieldStreamBase;
272   friend class ClassFileParser;
273   friend class FieldInfoReader;
274   friend class FieldInfoComparator;
275 
276  private:
277   static int compare_name_and_sig(const Symbol* n1, const Symbol* s1, const Symbol* n2, const Symbol* s2);
278 
279  public:
280   static int num_java_fields(const Array<u1>* fis);
281   static int num_injected_java_fields(const Array<u1>* fis);
282   static int num_total_fields(const Array<u1>* fis);
283 
284   static Array<u1>* create_FieldInfoStream(GrowableArray<FieldInfo>* fields, int java_fields, int injected_fields,
285                                            ClassLoaderData* loader_data, TRAPS);
286   static Array<u1>* create_search_table(ConstantPool* cp, const Array<u1>* fis, ClassLoaderData* loader_data, TRAPS);
287   static GrowableArray<FieldInfo>* create_FieldInfoArray(const Array<u1>* fis, int* java_fields_count, int* injected_fields_count);
288   static void print_from_fieldinfo_stream(Array<u1>* fis, outputStream* os, ConstantPool* cp);
289 
290   DEBUG_ONLY(static void validate_search_table(ConstantPool* cp, const Array<u1>* fis, const Array<u1>* search_table);)
291 
292   static void print_search_table(outputStream* st, ConstantPool* cp, const Array<u1>* fis, const Array<u1>* search_table);
293 };
294 
295 class FieldStatus {
296   enum FieldStatusBitPosition {
297     _fs_access_watched,       // field access is watched by JVMTI
298     _fs_modification_watched, // field modification is watched by JVMTI
299     _initialized_final_update // (static) final field updated outside (class) initializer
300   };
301 
302   // boilerplate:
303   u1 _flags;
304   static constexpr u1 flag_mask(FieldStatusBitPosition pos) { return (u1)1 << (int)pos; }
305   bool test_flag(FieldStatusBitPosition pos) { return (_flags & flag_mask(pos)) != 0; }
306   // this performs an atomic update on a live status byte!
307   void update_flag(FieldStatusBitPosition pos, bool z);
308   // out-of-line functions do a CAS-loop
309   static void atomic_set_bits(u1& flags, u1 mask);
310   static void atomic_clear_bits(u1& flags, u1 mask);
311 
312   public:
313   FieldStatus() { _flags = 0; }
314   FieldStatus(u1 flags) { _flags = flags; }
315   u1 as_uint() { return _flags; }
316 
317   bool is_access_watched()        { return test_flag(_fs_access_watched); }
318   bool is_modification_watched()  { return test_flag(_fs_modification_watched); }
319   bool is_initialized_final_update() { return test_flag(_initialized_final_update); }
320 
321   void update_access_watched(bool z);
322   void update_modification_watched(bool z);
323   void update_initialized_final_update(bool z);
324 };
325 
326 #endif // SHARE_OOPS_FIELDINFO_HPP