1 /* 2 * Copyright (c) 2003, 2019, 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_RUNTIME_JFIELDIDWORKAROUND_HPP 26 #define SHARE_RUNTIME_JFIELDIDWORKAROUND_HPP 27 28 class jfieldIDWorkaround: AllStatic { 29 // This workaround is because JVMTI doesn't have distinct entry points 30 // for methods that use static jfieldIDs and instance jfieldIDs. 31 // The workaround is to steal a low-order bit: 32 // a 1 means the jfieldID is an instance jfieldID, 33 // and the rest of the word is the offset of the field. 34 // a 0 means the jfieldID is a static jfieldID, 35 // and the rest of the word is the JNIid*. 36 // 37 // Another low-order bit is used to mark if an instance field 38 // is accompanied by an indication of which class it applies to. 39 // 40 // Bit-format of a jfieldID (most significant first): 41 // address:30 instance=0:1 checked=0:1 42 // offset:30 instance=1:1 checked=0:1 43 // klass:23 offset:7 instance=1:1 checked=1:1 44 // 45 // If the offset does not fit in 7 bits, or if the fieldID is 46 // not checked, then the checked bit is zero and the rest of 47 // the word (30 bits) contains only the offset. 48 // 49 private: 50 enum { 51 checked_bits = 1, 52 instance_bits = 1, 53 address_bits = BitsPerWord - checked_bits - instance_bits, 54 55 large_offset_bits = address_bits, // unioned with address 56 small_offset_bits = 7, 57 klass_bits = address_bits - small_offset_bits, 58 59 checked_shift = 0, 60 instance_shift = checked_shift + checked_bits, 61 address_shift = instance_shift + instance_bits, 62 63 offset_shift = address_shift, // unioned with address 64 klass_shift = offset_shift + small_offset_bits, 65 66 checked_mask_in_place = right_n_bits(checked_bits) << checked_shift, 67 instance_mask_in_place = right_n_bits(instance_bits) << instance_shift, 68 #ifndef _WIN64 69 large_offset_mask = right_n_bits(large_offset_bits), 70 small_offset_mask = right_n_bits(small_offset_bits), 71 klass_mask = right_n_bits(klass_bits) 72 #endif 73 }; 74 75 #ifdef _WIN64 76 // These values are too big for Win64 77 const static uintptr_t large_offset_mask = right_n_bits(large_offset_bits); 78 const static uintptr_t small_offset_mask = right_n_bits(small_offset_bits); 79 const static uintptr_t klass_mask = right_n_bits(klass_bits); 80 #endif 81 82 // helper routines: is_checked_jfieldID(jfieldID id)83 static bool is_checked_jfieldID(jfieldID id) { 84 uintptr_t as_uint = (uintptr_t) id; 85 return ((as_uint & checked_mask_in_place) != 0); 86 } raw_instance_offset(jfieldID id)87 static intptr_t raw_instance_offset(jfieldID id) { 88 uintptr_t result = (uintptr_t) id >> address_shift; 89 if (VerifyJNIFields && is_checked_jfieldID(id)) { 90 result &= small_offset_mask; // cut off the hash bits 91 } 92 return (intptr_t)result; 93 } 94 static intptr_t encode_klass_hash(Klass* k, intptr_t offset); 95 static bool klass_hash_ok(Klass* k, jfieldID id); 96 static void verify_instance_jfieldID(Klass* k, jfieldID id); 97 98 public: 99 static bool is_valid_jfieldID(Klass* k, jfieldID id); 100 is_instance_jfieldID(Klass * k,jfieldID id)101 static bool is_instance_jfieldID(Klass* k, jfieldID id) { 102 uintptr_t as_uint = (uintptr_t) id; 103 return ((as_uint & instance_mask_in_place) != 0); 104 } is_static_jfieldID(jfieldID id)105 static bool is_static_jfieldID(jfieldID id) { 106 uintptr_t as_uint = (uintptr_t) id; 107 return ((as_uint & instance_mask_in_place) == 0); 108 } 109 to_instance_jfieldID(Klass * k,int offset)110 static jfieldID to_instance_jfieldID(Klass* k, int offset) { 111 intptr_t as_uint = ((offset & large_offset_mask) << offset_shift) | instance_mask_in_place; 112 if (VerifyJNIFields) { 113 as_uint |= encode_klass_hash(k, offset); 114 } 115 jfieldID result = (jfieldID) as_uint; 116 #ifndef ASSERT 117 // always verify in debug mode; switchable in anything else 118 if (VerifyJNIFields) 119 #endif // ASSERT 120 { 121 verify_instance_jfieldID(k, result); 122 } 123 assert(raw_instance_offset(result) == (offset & large_offset_mask), "extract right offset"); 124 return result; 125 } 126 from_instance_jfieldID(Klass * k,jfieldID id)127 static intptr_t from_instance_jfieldID(Klass* k, jfieldID id) { 128 #ifndef ASSERT 129 // always verify in debug mode; switchable in anything else 130 if (VerifyJNIFields) 131 #endif // ASSERT 132 { 133 verify_instance_jfieldID(k, id); 134 } 135 return raw_instance_offset(id); 136 } 137 to_static_jfieldID(JNIid * id)138 static jfieldID to_static_jfieldID(JNIid* id) { 139 assert(id->is_static_field_id(), "from_JNIid, but not static field id"); 140 jfieldID result = (jfieldID) id; 141 assert(from_static_jfieldID(result) == id, "must produce the same static id"); 142 return result; 143 } 144 from_static_jfieldID(jfieldID id)145 static JNIid* from_static_jfieldID(jfieldID id) { 146 assert(jfieldIDWorkaround::is_static_jfieldID(id), 147 "to_JNIid, but not static jfieldID"); 148 JNIid* result = (JNIid*) id; 149 assert(result->is_static_field_id(), "to_JNIid, but not static field id"); 150 return result; 151 } 152 to_jfieldID(InstanceKlass * k,int offset,bool is_static)153 static jfieldID to_jfieldID(InstanceKlass* k, int offset, bool is_static) { 154 if (is_static) { 155 JNIid *id = k->jni_id_for(offset); 156 debug_only(id->set_is_static_field_id()); 157 return jfieldIDWorkaround::to_static_jfieldID(id); 158 } else { 159 return jfieldIDWorkaround::to_instance_jfieldID(k, offset); 160 } 161 } 162 }; 163 164 #endif // SHARE_RUNTIME_JFIELDIDWORKAROUND_HPP 165