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 <DecoratorSet decorators, bool external_guard> inline static oop resolve_impl(jobject handle); 46 47 // Resolve handle into oop, without keeping the object alive 48 inline static oop resolve_no_keepalive(jobject handle); 49 50 // This method is not inlined in order to avoid circular includes between 51 // this header file and thread.hpp. 52 static bool current_thread_in_native(); 53 54 public: 55 // Low tag bit in jobject used to distinguish a jweak. jweak is 56 // type equivalent to jobject, but there are places where we need to 57 // be able to distinguish jweak values from other jobjects, and 58 // is_weak_global_handle is unsuitable for performance reasons. To 59 // provide such a test we add weak_tag_value to the (aligned) byte 60 // address designated by the jobject to produce the corresponding 61 // jweak. Accessing the value of a jobject must account for it 62 // being a possibly offset jweak. 63 static const uintptr_t weak_tag_size = 1; 64 static const uintptr_t weak_tag_alignment = (1u << weak_tag_size); 65 static const uintptr_t weak_tag_mask = weak_tag_alignment - 1; 66 static const int weak_tag_value = 1; 67 68 // Resolve handle into oop 69 inline static oop resolve(jobject handle); 70 // Resolve handle into oop, result guaranteed not to be null 71 inline static oop resolve_non_null(jobject handle); 72 // Resolve externally provided handle into oop with some guards 73 static oop resolve_external_guard(jobject handle); 74 75 // Check for equality without keeping objects alive 76 static bool is_same_object(jobject handle1, jobject handle2); 77 78 // Local handles 79 static jobject make_local(oop obj); 80 static jobject make_local(JNIEnv* env, oop obj); // Fast version when env is known 81 static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known 82 inline static void destroy_local(jobject handle); 83 84 // Global handles 85 static jobject make_global(Handle obj, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM); 86 static void destroy_global(jobject handle); 87 88 // Weak global handles 89 static jobject make_weak_global(Handle obj, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM); 90 static void destroy_weak_global(jobject handle); 91 static bool is_global_weak_cleared(jweak handle); // Test jweak without resolution 92 93 // Initialization 94 static void initialize(); 95 96 // Debugging 97 static void print_on(outputStream* st); print()98 static void print() { print_on(tty); } 99 static void verify(); 100 // The category predicates all require handle != NULL. 101 static bool is_local_handle(Thread* thread, jobject handle); 102 static bool is_frame_handle(JavaThread* thread, jobject handle); 103 static bool is_global_handle(jobject handle); 104 static bool is_weak_global_handle(jobject handle); 105 static size_t global_handle_memory_usage(); 106 static size_t weak_global_handle_memory_usage(); 107 108 #ifndef PRODUCT 109 // Is handle from any local block of any thread? 110 static bool is_local_handle(jobject handle); 111 #endif 112 113 // precondition: handle != NULL. 114 static jobjectRefType handle_type(Thread* thread, jobject handle); 115 116 // Garbage collection support(global handles only, local handles are traversed from thread) 117 // Traversal of regular global handles 118 static void oops_do(OopClosure* f); 119 // Traversal of weak global handles. Unreachable oops are cleared. 120 static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f); 121 // Traversal of weak global handles. 122 static void weak_oops_do(OopClosure* f); 123 124 static OopStorage* global_handles(); 125 static OopStorage* weak_global_handles(); 126 }; 127 128 129 130 // JNI handle blocks holding local/global JNI handles 131 132 class JNIHandleBlock : public CHeapObj<mtInternal> { 133 friend class VMStructs; 134 friend class CppInterpreter; 135 136 private: 137 enum SomeConstants { 138 block_size_in_oops = 32 // Number of handles per handle block 139 }; 140 141 oop _handles[block_size_in_oops]; // The handles 142 int _top; // Index of next unused handle 143 JNIHandleBlock* _next; // Link to next block 144 145 // The following instance variables are only used by the first block in a chain. 146 // Having two types of blocks complicates the code and the space overhead in negligible. 147 JNIHandleBlock* _last; // Last block in use 148 JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call 149 oop* _free_list; // Handle free list 150 int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list 151 152 // Check JNI, "planned capacity" for current frame (or push/ensure) 153 size_t _planned_capacity; 154 155 #ifndef PRODUCT 156 JNIHandleBlock* _block_list_link; // Link for list below 157 static JNIHandleBlock* _block_list; // List of all allocated blocks (for debugging only) 158 #endif 159 160 static JNIHandleBlock* _block_free_list; // Free list of currently unused blocks 161 static int _blocks_allocated; // For debugging/printing 162 163 // Fill block with bad_handle values 164 void zap() NOT_DEBUG_RETURN; 165 166 // Free list computation 167 void rebuild_free_list(); 168 169 // No more handles in the both the current and following blocks clear()170 void clear() { _top = 0; } 171 172 public: 173 // Handle allocation 174 jobject allocate_handle(oop obj); 175 176 // Block allocation and block free list management 177 static JNIHandleBlock* allocate_block(Thread* thread = NULL); 178 static void release_block(JNIHandleBlock* block, Thread* thread = NULL); 179 180 // JNI PushLocalFrame/PopLocalFrame support pop_frame_link() const181 JNIHandleBlock* pop_frame_link() const { return _pop_frame_link; } set_pop_frame_link(JNIHandleBlock * block)182 void set_pop_frame_link(JNIHandleBlock* block) { _pop_frame_link = block; } 183 184 // Stub generator support top_offset_in_bytes()185 static int top_offset_in_bytes() { return offset_of(JNIHandleBlock, _top); } 186 187 // Garbage collection support 188 // Traversal of handles 189 void oops_do(OopClosure* f); 190 191 // Checked JNI support set_planned_capacity(size_t planned_capacity)192 void set_planned_capacity(size_t planned_capacity) { _planned_capacity = planned_capacity; } get_planned_capacity()193 const size_t get_planned_capacity() { return _planned_capacity; } 194 const size_t get_number_of_live_handles(); 195 196 // Debugging 197 bool chain_contains(jobject handle) const; // Does this block or following blocks contain handle 198 bool contains(jobject handle) const; // Does this block contain handle 199 size_t length() const; // Length of chain starting with this block 200 size_t memory_usage() const; 201 #ifndef PRODUCT 202 static bool any_contains(jobject handle); // Does any block currently in use contain handle 203 static void print_statistics(); 204 #endif 205 }; 206 207 #endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP 208