1 /*
2 * Copyright (c) 1998, 2018, 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 #ifndef SHARE_VM_RUNTIME_JNIHANDLES_HPP
26 #define SHARE_VM_RUNTIME_JNIHANDLES_HPP
27
28 #include "memory/allocation.hpp"
29 #include "runtime/handles.hpp"
30
31 class OopStorage;
32
33 // Interface for creating and resolving local/global JNI handles
34
35 class JNIHandles : AllStatic {
36 friend class VMStructs;
37 private:
38 static OopStorage* _global_handles;
39 static OopStorage* _weak_global_handles;
40
41 inline static bool is_jweak(jobject handle);
42 inline static oop* jobject_ptr(jobject handle); // NOT jweak!
43 inline static oop* jweak_ptr(jobject handle);
44
45 template<bool external_guard> inline static oop resolve_impl(jobject handle);
46 static oop resolve_jweak(jweak handle);
47
48 // This method is not inlined in order to avoid circular includes between
49 // this header file and thread.hpp.
50 static bool current_thread_in_native();
51
52 public:
53 // Low tag bit in jobject used to distinguish a jweak. jweak is
54 // type equivalent to jobject, but there are places where we need to
55 // be able to distinguish jweak values from other jobjects, and
56 // is_weak_global_handle is unsuitable for performance reasons. To
57 // provide such a test we add weak_tag_value to the (aligned) byte
58 // address designated by the jobject to produce the corresponding
59 // jweak. Accessing the value of a jobject must account for it
60 // being a possibly offset jweak.
61 static const uintptr_t weak_tag_size = 1;
62 static const uintptr_t weak_tag_alignment = (1u << weak_tag_size);
63 static const uintptr_t weak_tag_mask = weak_tag_alignment - 1;
64 static const int weak_tag_value = 1;
65
66 // Resolve handle into oop
67 inline static oop resolve(jobject handle);
68 // Resolve handle into oop, result guaranteed not to be null
69 inline static oop resolve_non_null(jobject handle);
70 // Resolve externally provided handle into oop with some guards
71 static oop resolve_external_guard(jobject handle);
72
73 // Local handles
74 static jobject make_local(oop obj);
75 static jobject make_local(JNIEnv* env, oop obj); // Fast version when env is known
76 static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known
77 inline static void destroy_local(jobject handle);
78
79 // Global handles
80 static jobject make_global(Handle obj, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
81 static void destroy_global(jobject handle);
82
83 // Weak global handles
84 static jobject make_weak_global(Handle obj, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
85 static void destroy_weak_global(jobject handle);
86 static bool is_global_weak_cleared(jweak handle); // Test jweak without resolution
87
88 // Initialization
89 static void initialize();
90
91 // Debugging
92 static void print_on(outputStream* st);
93 static void print() { print_on(tty); }
94 static void verify();
95 // The category predicates all require handle != NULL.
96 static bool is_local_handle(Thread* thread, jobject handle);
97 static bool is_frame_handle(JavaThread* thread, jobject handle);
98 static bool is_global_handle(jobject handle);
99 static bool is_weak_global_handle(jobject handle);
100 static size_t global_handle_memory_usage();
101 static size_t weak_global_handle_memory_usage();
102
103 #ifndef PRODUCT
104 // Is handle from any local block of any thread?
105 static bool is_local_handle(jobject handle);
106 #endif
107
108 // precondition: handle != NULL.
109 static jobjectRefType handle_type(Thread* thread, jobject handle);
110
111 // Garbage collection support(global handles only, local handles are traversed from thread)
112 // Traversal of regular global handles
113 static void oops_do(OopClosure* f);
114 // Traversal of weak global handles. Unreachable oops are cleared.
115 static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f);
116 // Traversal of weak global handles.
117 static void weak_oops_do(OopClosure* f);
118 };
119
120
121
122 // JNI handle blocks holding local/global JNI handles
123
124 class JNIHandleBlock : public CHeapObj<mtInternal> {
125 friend class VMStructs;
126 friend class CppInterpreter;
127
128 private:
129 enum SomeConstants {
130 block_size_in_oops = 32 // Number of handles per handle block
131 };
132
133 oop _handles[block_size_in_oops]; // The handles
134 int _top; // Index of next unused handle
135 JNIHandleBlock* _next; // Link to next block
136
137 // The following instance variables are only used by the first block in a chain.
138 // Having two types of blocks complicates the code and the space overhead in negligible.
139 JNIHandleBlock* _last; // Last block in use
140 JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call
141 oop* _free_list; // Handle free list
142 int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list
143
144 // Check JNI, "planned capacity" for current frame (or push/ensure)
145 size_t _planned_capacity;
146
147 #ifndef PRODUCT
148 JNIHandleBlock* _block_list_link; // Link for list below
149 static JNIHandleBlock* _block_list; // List of all allocated blocks (for debugging only)
150 #endif
151
152 static JNIHandleBlock* _block_free_list; // Free list of currently unused blocks
153 static int _blocks_allocated; // For debugging/printing
154
155 // Fill block with bad_handle values
156 void zap() NOT_DEBUG_RETURN;
157
158 // Free list computation
159 void rebuild_free_list();
160
161 // No more handles in the both the current and following blocks
162 void clear() { _top = 0; }
163
164 public:
165 // Handle allocation
166 jobject allocate_handle(oop obj);
167
168 // Block allocation and block free list management
169 static JNIHandleBlock* allocate_block(Thread* thread = NULL);
170 static void release_block(JNIHandleBlock* block, Thread* thread = NULL);
171
172 // JNI PushLocalFrame/PopLocalFrame support
173 JNIHandleBlock* pop_frame_link() const { return _pop_frame_link; }
174 void set_pop_frame_link(JNIHandleBlock* block) { _pop_frame_link = block; }
175
176 // Stub generator support
177 static int top_offset_in_bytes() { return offset_of(JNIHandleBlock, _top); }
178
179 // Garbage collection support
180 // Traversal of handles
181 void oops_do(OopClosure* f);
182
183 // Checked JNI support
184 void set_planned_capacity(size_t planned_capacity) { _planned_capacity = planned_capacity; }
185 const size_t get_planned_capacity() { return _planned_capacity; }
186 const size_t get_number_of_live_handles();
187
188 // Debugging
189 bool chain_contains(jobject handle) const; // Does this block or following blocks contain handle
190 bool contains(jobject handle) const; // Does this block contain handle
191 size_t length() const; // Length of chain starting with this block
192 size_t memory_usage() const;
193 #ifndef PRODUCT
194 static bool any_contains(jobject handle); // Does any block currently in use contain handle
195 static void print_statistics();
196 #endif
197 };
198
199 #endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP