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: |
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 | } |
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 | |
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 | } |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |