| /* |
| * Copyright (c) 2003, 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_JFIELDIDWORKAROUND_HPP |
| #define SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP |
| |
| class jfieldIDWorkaround: AllStatic { |
| // This workaround is because JVMTI doesn't have distinct entry points |
| // for methods that use static jfieldIDs and instance jfieldIDs. |
| // The workaround is to steal a low-order bit: |
| // a 1 means the jfieldID is an instance jfieldID, |
| // and the rest of the word is the offset of the field. |
| // a 0 means the jfieldID is a static jfieldID, |
| // and the rest of the word is the JNIid*. |
| // |
| // Another low-order bit is used to mark if an instance field |
| // is accompanied by an indication of which class it applies to. |
| // |
| // Bit-format of a jfieldID (most significant first): |
| // address:30 instance=0:1 checked=0:1 |
| // offset:30 instance=1:1 checked=0:1 |
| // klass:23 offset:7 instance=1:1 checked=1:1 |
| // |
| // If the offset does not fit in 7 bits, or if the fieldID is |
| // not checked, then the checked bit is zero and the rest of |
| // the word (30 bits) contains only the offset. |
| // |
| private: |
| enum { |
| checked_bits = 1, |
| instance_bits = 1, |
| address_bits = BitsPerWord - checked_bits - instance_bits, |
| |
| large_offset_bits = address_bits, // unioned with address |
| small_offset_bits = 7, |
| klass_bits = address_bits - small_offset_bits, |
| |
| checked_shift = 0, |
| instance_shift = checked_shift + checked_bits, |
| address_shift = instance_shift + instance_bits, |
| |
| offset_shift = address_shift, // unioned with address |
| klass_shift = offset_shift + small_offset_bits, |
| |
| checked_mask_in_place = right_n_bits(checked_bits) << checked_shift, |
| instance_mask_in_place = right_n_bits(instance_bits) << instance_shift, |
| #ifndef _WIN64 |
| large_offset_mask = right_n_bits(large_offset_bits), |
| small_offset_mask = right_n_bits(small_offset_bits), |
| klass_mask = right_n_bits(klass_bits) |
| #endif |
| }; |
| |
| #ifdef _WIN64 |
| // These values are too big for Win64 |
| const static uintptr_t large_offset_mask = right_n_bits(large_offset_bits); |
| const static uintptr_t small_offset_mask = right_n_bits(small_offset_bits); |
| const static uintptr_t klass_mask = right_n_bits(klass_bits); |
| #endif |
| |
| // helper routines: |
| static bool is_checked_jfieldID(jfieldID id) { |
| uintptr_t as_uint = (uintptr_t) id; |
| return ((as_uint & checked_mask_in_place) != 0); |
| } |
| static intptr_t raw_instance_offset(jfieldID id) { |
| uintptr_t result = (uintptr_t) id >> address_shift; |
| if (VerifyJNIFields && is_checked_jfieldID(id)) { |
| result &= small_offset_mask; // cut off the hash bits |
| } |
| return (intptr_t)result; |
| } |
| static intptr_t encode_klass_hash(Klass* k, intptr_t offset); |
| static bool klass_hash_ok(Klass* k, jfieldID id); |
| static void verify_instance_jfieldID(Klass* k, jfieldID id); |
| |
| public: |
| static bool is_valid_jfieldID(Klass* k, jfieldID id); |
| |
| static bool is_instance_jfieldID(Klass* k, jfieldID id) { |
| uintptr_t as_uint = (uintptr_t) id; |
| return ((as_uint & instance_mask_in_place) != 0); |
| } |
| static bool is_static_jfieldID(jfieldID id) { |
| uintptr_t as_uint = (uintptr_t) id; |
| return ((as_uint & instance_mask_in_place) == 0); |
| } |
| |
| static jfieldID to_instance_jfieldID(Klass* k, int offset) { |
| intptr_t as_uint = ((offset & large_offset_mask) << offset_shift) | instance_mask_in_place; |
| if (VerifyJNIFields) { |
| as_uint |= encode_klass_hash(k, offset); |
| } |
| jfieldID result = (jfieldID) as_uint; |
| #ifndef ASSERT |
| // always verify in debug mode; switchable in anything else |
| if (VerifyJNIFields) |
| #endif // ASSERT |
| { |
| verify_instance_jfieldID(k, result); |
| } |
| assert(raw_instance_offset(result) == (offset & large_offset_mask), "extract right offset"); |
| return result; |
| } |
| |
| static intptr_t from_instance_jfieldID(Klass* k, jfieldID id) { |
| #ifndef ASSERT |
| // always verify in debug mode; switchable in anything else |
| if (VerifyJNIFields) |
| #endif // ASSERT |
| { |
| verify_instance_jfieldID(k, id); |
| } |
| return raw_instance_offset(id); |
| } |
| |
| static jfieldID to_static_jfieldID(JNIid* id) { |
| assert(id->is_static_field_id(), "from_JNIid, but not static field id"); |
| jfieldID result = (jfieldID) id; |
| assert(from_static_jfieldID(result) == id, "must produce the same static id"); |
| return result; |
| } |
| |
| static JNIid* from_static_jfieldID(jfieldID id) { |
| assert(jfieldIDWorkaround::is_static_jfieldID(id), |
| "to_JNIid, but not static jfieldID"); |
| JNIid* result = (JNIid*) id; |
| assert(result->is_static_field_id(), "to_JNIid, but not static field id"); |
| return result; |
| } |
| |
| static jfieldID to_jfieldID(InstanceKlass* k, int offset, bool is_static) { |
| if (is_static) { |
| JNIid *id = k->jni_id_for(offset); |
| debug_only(id->set_is_static_field_id()); |
| return jfieldIDWorkaround::to_static_jfieldID(id); |
| } else { |
| return jfieldIDWorkaround::to_instance_jfieldID(k, offset); |
| } |
| } |
| }; |
| |
| #endif // SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP |