| /* |
| * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #ifndef SHARE_VM_RUNTIME_JNIHANDLES_HPP |
| #define SHARE_VM_RUNTIME_JNIHANDLES_HPP |
| |
| #include "memory/allocation.hpp" |
| #include "runtime/handles.hpp" |
| |
| class JNIHandleBlock; |
| |
| |
| // Interface for creating and resolving local/global JNI handles |
| |
| class JNIHandles : AllStatic { |
| friend class VMStructs; |
| private: |
| static JNIHandleBlock* _global_handles; // First global handle block |
| static JNIHandleBlock* _weak_global_handles; // First weak global handle block |
| static oop _deleted_handle; // Sentinel marking deleted handles |
| |
| inline static bool is_jweak(jobject handle); |
| inline static oop& jobject_ref(jobject handle); // NOT jweak! |
| inline static oop& jweak_ref(jobject handle); |
| |
| template<bool external_guard> inline static oop guard_value(oop value); |
| template<bool external_guard> inline static oop resolve_impl(jobject handle); |
| template<bool external_guard> static oop resolve_jweak(jweak handle); |
| |
| public: |
| // Low tag bit in jobject used to distinguish a jweak. jweak is |
| // type equivalent to jobject, but there are places where we need to |
| // be able to distinguish jweak values from other jobjects, and |
| // is_weak_global_handle is unsuitable for performance reasons. To |
| // provide such a test we add weak_tag_value to the (aligned) byte |
| // address designated by the jobject to produce the corresponding |
| // jweak. Accessing the value of a jobject must account for it |
| // being a possibly offset jweak. |
| static const uintptr_t weak_tag_size = 1; |
| static const uintptr_t weak_tag_alignment = (1u << weak_tag_size); |
| static const uintptr_t weak_tag_mask = weak_tag_alignment - 1; |
| static const int weak_tag_value = 1; |
| |
| // Resolve handle into oop |
| inline static oop resolve(jobject handle); |
| // Resolve externally provided handle into oop with some guards |
| inline static oop resolve_external_guard(jobject handle); |
| // Resolve handle into oop, result guaranteed not to be null |
| inline static oop resolve_non_null(jobject handle); |
| |
| // Local handles |
| static jobject make_local(oop obj); |
| static jobject make_local(JNIEnv* env, oop obj); // Fast version when env is known |
| static jobject make_local(Thread* thread, oop obj); // Even faster version when current thread is known |
| inline static void destroy_local(jobject handle); |
| |
| // Global handles |
| static jobject make_global(Handle obj); |
| static void destroy_global(jobject handle); |
| |
| // Weak global handles |
| static jobject make_weak_global(Handle obj); |
| static void destroy_weak_global(jobject handle); |
| |
| // Sentinel marking deleted handles in block. Note that we cannot store NULL as |
| // the sentinel, since clearing weak global JNI refs are done by storing NULL in |
| // the handle. The handle may not be reused before destroy_weak_global is called. |
| static oop deleted_handle() { return _deleted_handle; } |
| |
| // Initialization |
| static void initialize(); |
| |
| // Debugging |
| static void print_on(outputStream* st); |
| static void print() { print_on(tty); } |
| static void verify(); |
| static bool is_local_handle(Thread* thread, jobject handle); |
| static bool is_frame_handle(JavaThread* thr, jobject obj); |
| static bool is_global_handle(jobject handle); |
| static bool is_weak_global_handle(jobject handle); |
| static long global_handle_memory_usage(); |
| static long weak_global_handle_memory_usage(); |
| |
| // Garbage collection support(global handles only, local handles are traversed from thread) |
| // Traversal of regular global handles |
| static void oops_do(OopClosure* f); |
| // Traversal of weak global handles. Unreachable oops are cleared. |
| static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f); |
| // Traversal of weak global handles. |
| static void weak_oops_do(OopClosure* f); |
| }; |
| |
| |
| |
| // JNI handle blocks holding local/global JNI handles |
| |
| class JNIHandleBlock : public CHeapObj<mtInternal> { |
| friend class VMStructs; |
| friend class CppInterpreter; |
| |
| private: |
| enum SomeConstants { |
| block_size_in_oops = 32 // Number of handles per handle block |
| }; |
| |
| oop _handles[block_size_in_oops]; // The handles |
| int _top; // Index of next unused handle |
| JNIHandleBlock* _next; // Link to next block |
| |
| // The following instance variables are only used by the first block in a chain. |
| // Having two types of blocks complicates the code and the space overhead in negligible. |
| JNIHandleBlock* _last; // Last block in use |
| JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call |
| oop* _free_list; // Handle free list |
| int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list |
| |
| // Check JNI, "planned capacity" for current frame (or push/ensure) |
| size_t _planned_capacity; |
| |
| #ifndef PRODUCT |
| JNIHandleBlock* _block_list_link; // Link for list below |
| static JNIHandleBlock* _block_list; // List of all allocated blocks (for debugging only) |
| #endif |
| |
| static JNIHandleBlock* _block_free_list; // Free list of currently unused blocks |
| static int _blocks_allocated; // For debugging/printing |
| |
| // Fill block with bad_handle values |
| void zap(); |
| |
| // Free list computation |
| void rebuild_free_list(); |
| |
| // No more handles in the both the current and following blocks |
| void clear() { _top = 0; } |
| |
| public: |
| // Handle allocation |
| jobject allocate_handle(oop obj); |
| |
| // Release Handle |
| void release_handle(jobject); |
| |
| // Block allocation and block free list management |
| static JNIHandleBlock* allocate_block(Thread* thread = NULL); |
| static void release_block(JNIHandleBlock* block, Thread* thread = NULL); |
| |
| // JNI PushLocalFrame/PopLocalFrame support |
| JNIHandleBlock* pop_frame_link() const { return _pop_frame_link; } |
| void set_pop_frame_link(JNIHandleBlock* block) { _pop_frame_link = block; } |
| |
| // Stub generator support |
| static int top_offset_in_bytes() { return offset_of(JNIHandleBlock, _top); } |
| |
| // Garbage collection support |
| // Traversal of regular handles |
| void oops_do(OopClosure* f); |
| // Traversal of weak handles. Unreachable oops are cleared. |
| void weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f); |
| |
| // Checked JNI support |
| void set_planned_capacity(size_t planned_capacity) { _planned_capacity = planned_capacity; } |
| const size_t get_planned_capacity() { return _planned_capacity; } |
| const size_t get_number_of_live_handles(); |
| |
| // Debugging |
| bool chain_contains(jobject handle) const; // Does this block or following blocks contain handle |
| bool contains(jobject handle) const; // Does this block contain handle |
| int length() const; // Length of chain starting with this block |
| long memory_usage() const; |
| #ifndef PRODUCT |
| static bool any_contains(jobject handle); // Does any block currently in use contain handle |
| static void print_statistics(); |
| #endif |
| }; |
| |
| inline bool JNIHandles::is_jweak(jobject handle) { |
| STATIC_ASSERT(weak_tag_size == 1); |
| STATIC_ASSERT(weak_tag_value == 1); |
| return (reinterpret_cast<uintptr_t>(handle) & weak_tag_mask) != 0; |
| } |
| |
| inline oop& JNIHandles::jobject_ref(jobject handle) { |
| assert(!is_jweak(handle), "precondition"); |
| return *reinterpret_cast<oop*>(handle); |
| } |
| |
| inline oop& JNIHandles::jweak_ref(jobject handle) { |
| assert(is_jweak(handle), "precondition"); |
| char* ptr = reinterpret_cast<char*>(handle) - weak_tag_value; |
| return *reinterpret_cast<oop*>(ptr); |
| } |
| |
| // external_guard is true if called from resolve_external_guard. |
| // Treat deleted (and possibly zapped) as NULL for external_guard, |
| // else as (asserted) error. |
| template<bool external_guard> |
| inline oop JNIHandles::guard_value(oop value) { |
| if (!external_guard) { |
| assert(value != badJNIHandle, "Pointing to zapped jni handle area"); |
| assert(value != deleted_handle(), "Used a deleted global handle"); |
| } else if ((value == badJNIHandle) || (value == deleted_handle())) { |
| value = NULL; |
| } |
| return value; |
| } |
| |
| // external_guard is true if called from resolve_external_guard. |
| template<bool external_guard> |
| inline oop JNIHandles::resolve_impl(jobject handle) { |
| assert(handle != NULL, "precondition"); |
| oop result; |
| if (is_jweak(handle)) { // Unlikely |
| result = resolve_jweak<external_guard>(handle); |
| } else { |
| result = jobject_ref(handle); |
| // Construction of jobjects canonicalize a null value into a null |
| // jobject, so for non-jweak the pointee should never be null. |
| assert(external_guard || result != NULL, |
| "Invalid value read from jni handle"); |
| result = guard_value<external_guard>(result); |
| } |
| return result; |
| } |
| |
| inline oop JNIHandles::resolve(jobject handle) { |
| oop result = NULL; |
| if (handle != NULL) { |
| result = resolve_impl<false /* external_guard */ >(handle); |
| } |
| return result; |
| } |
| |
| // Resolve some erroneous cases to NULL, rather than treating them as |
| // possibly unchecked errors. In particular, deleted handles are |
| // treated as NULL (though a deleted and later reallocated handle |
| // isn't detected). |
| inline oop JNIHandles::resolve_external_guard(jobject handle) { |
| oop result = NULL; |
| if (handle != NULL) { |
| result = resolve_impl<true /* external_guard */ >(handle); |
| } |
| return result; |
| } |
| |
| inline oop JNIHandles::resolve_non_null(jobject handle) { |
| assert(handle != NULL, "JNI handle should not be null"); |
| oop result = resolve_impl<false /* external_guard */ >(handle); |
| assert(result != NULL, "NULL read from jni handle"); |
| return result; |
| } |
| |
| inline void JNIHandles::destroy_local(jobject handle) { |
| if (handle != NULL) { |
| jobject_ref(handle) = deleted_handle(); |
| } |
| } |
| |
| #endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP |