1 /*
2 * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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.
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20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #include "code/vtableStubs.hpp"
26 #include "compiler/compileBroker.hpp"
27 #include "compiler/disassembler.hpp"
28 #include "logging/log.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "memory/resourceArea.hpp"
31 #include "oops/instanceKlass.hpp"
32 #include "oops/klass.inline.hpp"
33 #include "oops/klassVtable.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "prims/forte.hpp"
36 #include "prims/jvmtiExport.hpp"
37 #include "runtime/handles.inline.hpp"
38 #include "runtime/mutexLocker.hpp"
39 #include "runtime/sharedRuntime.hpp"
40 #include "utilities/align.hpp"
41 #include "utilities/powerOfTwo.hpp"
42
43 // -----------------------------------------------------------------------------------------
44 // Implementation of VtableStub
45
46 address VtableStub::_chunk = nullptr;
47 address VtableStub::_chunk_end = nullptr;
48 VMReg VtableStub::_receiver_location = VMRegImpl::Bad();
49
50
51 void* VtableStub::operator new(size_t size, int code_size) throw() {
52 assert_lock_strong(VtableStubs_lock);
53 assert(size == sizeof(VtableStub), "mismatched size");
54
55 MACOS_AARCH64_ONLY(os::thread_wx_enable_write());
56
57 // compute real VtableStub size (rounded to nearest word)
58 const int real_size = align_up(code_size + (int)sizeof(VtableStub), wordSize);
59 // malloc them in chunks to minimize header overhead
60 const int chunk_factor = 32;
61 if (_chunk == nullptr || _chunk + real_size > _chunk_end) {
62 const int bytes = chunk_factor * real_size + pd_code_alignment();
63
64 // There is a dependency on the name of the blob in src/share/vm/prims/jvmtiCodeBlobEvents.cpp
65 // If changing the name, update the other file accordingly.
66 VtableBlob* blob = VtableBlob::create("vtable chunks", bytes);
67 if (blob == nullptr) {
68 return nullptr;
69 }
70 _chunk = blob->content_begin();
71 _chunk_end = _chunk + bytes;
72 Forte::register_stub("vtable stub", _chunk, _chunk_end);
73 align_chunk();
74 }
75 assert(_chunk + real_size <= _chunk_end, "bad allocation");
76 void* res = _chunk;
77 _chunk += real_size;
78 align_chunk();
79 return res;
80 }
81
82
83 void VtableStub::print_on(outputStream* st) const {
84 st->print("vtable stub (index = %d, receiver_location = %zd, code = [" INTPTR_FORMAT ", " INTPTR_FORMAT "])",
85 index(), p2i(receiver_location()), p2i(code_begin()), p2i(code_end()));
86 }
87
88 void VtableStub::print() const { print_on(tty); }
89
90 // -----------------------------------------------------------------------------------------
91 // Implementation of VtableStubs
92 //
93 // For each hash value there's a linked list of vtable stubs (with that
94 // hash value). Each list is anchored in a little hash _table, indexed
95 // by that hash value.
96
97 VtableStub* volatile VtableStubs::_table[VtableStubs::N];
98 int VtableStubs::_vtab_stub_size = 0;
99 int VtableStubs::_itab_stub_size = 0;
100
101 #if defined(PRODUCT)
102 // These values are good for the PRODUCT case (no tracing).
103 static const int first_vtableStub_size = 64;
104 static const int first_itableStub_size = 256;
105 #else
106 // These values are good for the non-PRODUCT case (when tracing can be switched on).
107 // To find out, run test workload with
108 // -Xlog:vtablestubs=Trace -XX:+CountCompiledCalls -XX:+DebugVtables
109 // and use the reported "estimate" value.
110 // Here is a list of observed worst-case values:
111 // vtable itable
112 // aarch64: 460 324
113 // arm: ? ?
114 // ppc (linux, BE): 404 288
115 // ppc (linux, LE): 356 276
116 // ppc (AIX): 416 296
117 // s390x: 408 256
118 // Solaris-sparc: 792 348
119 // x86 (Linux): 670 309
120 // x86 (MacOS): 682 321
121 static const int first_vtableStub_size = 1024;
122 static const int first_itableStub_size = 512;
123 #endif
124
125
126 void VtableStubs::initialize() {
127 assert(VtableStub::_receiver_location == VMRegImpl::Bad(), "initialized multiple times?");
128
129 VtableStub::_receiver_location = SharedRuntime::name_for_receiver();
130 {
131 MutexLocker ml(VtableStubs_lock, Mutex::_no_safepoint_check_flag);
132 for (int i = 0; i < N; i++) {
133 AtomicAccess::store(&_table[i], (VtableStub*)nullptr);
134 }
135 }
136 }
137
138
139 int VtableStubs::code_size_limit(bool is_vtable_stub) {
140 if (is_vtable_stub) {
141 return _vtab_stub_size > 0 ? _vtab_stub_size : first_vtableStub_size;
142 } else { // itable stub
143 return _itab_stub_size > 0 ? _itab_stub_size : first_itableStub_size;
144 }
145 } // code_size_limit
146
147
148 void VtableStubs::check_and_set_size_limit(bool is_vtable_stub,
149 int code_size,
150 int padding) {
151 const char* name = is_vtable_stub ? "vtable" : "itable";
152
153 guarantee(code_size <= code_size_limit(is_vtable_stub),
154 "buffer overflow in %s stub, code_size is %d, limit is %d", name, code_size, code_size_limit(is_vtable_stub));
155
156 if (is_vtable_stub) {
157 if (log_is_enabled(Trace, vtablestubs)) {
158 if ( (_vtab_stub_size > 0) && ((code_size + padding) > _vtab_stub_size) ) {
159 log_trace(vtablestubs)("%s size estimate needed adjustment from %d to %d bytes",
160 name, _vtab_stub_size, code_size + padding);
161 }
162 }
163 if ( (code_size + padding) > _vtab_stub_size ) {
164 _vtab_stub_size = code_size + padding;
165 }
166 } else { // itable stub
167 if (log_is_enabled(Trace, vtablestubs)) {
168 if ( (_itab_stub_size > 0) && ((code_size + padding) > _itab_stub_size) ) {
169 log_trace(vtablestubs)("%s size estimate needed adjustment from %d to %d bytes",
170 name, _itab_stub_size, code_size + padding);
171 }
172 }
173 if ( (code_size + padding) > _itab_stub_size ) {
174 _itab_stub_size = code_size + padding;
175 }
176 }
177 return;
178 } // check_and_set_size_limit
179
180
181 void VtableStubs::bookkeeping(MacroAssembler* masm, outputStream* out, VtableStub* s,
182 address npe_addr, address ame_addr, bool is_vtable_stub,
183 int index, int slop_bytes, int index_dependent_slop) {
184 const char* name = is_vtable_stub ? "vtable" : "itable";
185 const int stub_length = code_size_limit(is_vtable_stub);
186
187 if (log_is_enabled(Trace, vtablestubs)) {
188 log_trace(vtablestubs)("%s #%d at " PTR_FORMAT ": size: %d, estimate: %d, slop area: %d",
189 name, index, p2i(s->code_begin()),
190 (int)(masm->pc() - s->code_begin()),
191 stub_length,
192 (int)(s->code_end() - masm->pc()));
193 }
194 guarantee(masm->pc() <= s->code_end(), "%s #%d: overflowed buffer, estimated len: %d, actual len: %d, overrun: %d",
195 name, index, stub_length,
196 (int)(masm->pc() - s->code_begin()),
197 (int)(masm->pc() - s->code_end()));
198 assert((masm->pc() + index_dependent_slop) <= s->code_end(), "%s #%d: spare space for 32-bit offset: required = %d, available = %d",
199 name, index, index_dependent_slop,
200 (int)(s->code_end() - masm->pc()));
201
202 // After the first vtable/itable stub is generated, we have a much
203 // better estimate for the stub size. Remember/update this
204 // estimate after some sanity checks.
205 check_and_set_size_limit(is_vtable_stub, masm->offset(), slop_bytes);
206 s->set_exception_points(npe_addr, ame_addr);
207 }
208
209
210 address VtableStubs::find_stub(bool is_vtable_stub, int vtable_index, bool caller_is_c1) {
211 assert(vtable_index >= 0, "must be positive");
212
213 VtableStub* s;
214 {
215 MutexLocker ml(VtableStubs_lock, Mutex::_no_safepoint_check_flag);
216 s = lookup(is_vtable_stub, vtable_index, caller_is_c1);
217 if (s == nullptr) {
218 if (is_vtable_stub) {
219 s = create_vtable_stub(vtable_index, caller_is_c1);
220 } else {
221 s = create_itable_stub(vtable_index, caller_is_c1);
222 }
223
224 // Creation of vtable or itable can fail if there is not enough free space in the code cache.
225 if (s == nullptr) {
226 return nullptr;
227 }
228
229 enter(is_vtable_stub, vtable_index, caller_is_c1, s);
230 if (PrintAdapterHandlers) {
231 tty->print_cr("Decoding VtableStub (%s) %s[%d]@" PTR_FORMAT " [" PTR_FORMAT ", " PTR_FORMAT "] (%zu bytes)",
232 caller_is_c1 ? "c1" : "full opt",
233 is_vtable_stub? "vtbl": "itbl", vtable_index, p2i(VtableStub::receiver_location()),
234 p2i(s->code_begin()), p2i(s->code_end()), pointer_delta(s->code_end(), s->code_begin(), 1));
235 Disassembler::decode(s->code_begin(), s->code_end());
236 }
237 // Notify JVMTI about this stub. The event will be recorded by the enclosing
238 // JvmtiDynamicCodeEventCollector and posted when this thread has released
239 // all locks. Only post this event if a new state is not required. Creating a new state would
240 // cause a safepoint and the caller of this code has a NoSafepointVerifier.
241 if (JvmtiExport::should_post_dynamic_code_generated()) {
242 JvmtiExport::post_dynamic_code_generated_while_holding_locks(is_vtable_stub? "vtable stub": "itable stub", // FIXME: need to pass caller_is_c1??
243 s->code_begin(), s->code_end());
244 }
245 }
246 }
247 return s->entry_point();
248 }
249
250
251 inline uint VtableStubs::hash(bool is_vtable_stub, int vtable_index, bool caller_is_c1) {
252 // Assumption: receiver_location < 4 in most cases.
253 int hash = ((vtable_index << 2) ^ VtableStub::receiver_location()->value()) + vtable_index;
254 if (caller_is_c1) {
255 hash = 7 - hash;
256 }
257 return (is_vtable_stub ? ~hash : hash) & mask;
258 }
259
260
261 inline uint VtableStubs::unsafe_hash(address entry_point, bool caller_is_c1) {
262 // The entrypoint may or may not be a VtableStub. Generate a hash as if it was.
263 address vtable_stub_addr = entry_point - VtableStub::entry_offset();
264 assert(CodeCache::contains(vtable_stub_addr), "assumed to always be the case");
265 address vtable_type_addr = vtable_stub_addr + offset_of(VtableStub, _type);
266 address vtable_index_addr = vtable_stub_addr + offset_of(VtableStub, _index);
267 bool is_vtable_stub = *vtable_type_addr == static_cast<uint8_t>(VtableStub::Type::vtable_stub);
268 short vtable_index;
269 static_assert(sizeof(VtableStub::_index) == sizeof(vtable_index), "precondition");
270 memcpy(&vtable_index, vtable_index_addr, sizeof(vtable_index));
271 return hash(is_vtable_stub, vtable_index, caller_is_c1);
272 }
273
274 VtableStub* VtableStubs::lookup(bool is_vtable_stub, int vtable_index, bool caller_is_c1) {
275 assert_lock_strong(VtableStubs_lock);
276 unsigned hash = VtableStubs::hash(is_vtable_stub, vtable_index, caller_is_c1);
277 VtableStub* s = AtomicAccess::load(&_table[hash]);
278 while( s && !s->matches(is_vtable_stub, vtable_index, caller_is_c1)) s = s->next();
279 return s;
280 }
281
282
283 void VtableStubs::enter(bool is_vtable_stub, int vtable_index, bool caller_is_c1, VtableStub* s) {
284 assert_lock_strong(VtableStubs_lock);
285 assert(s->matches(is_vtable_stub, vtable_index, caller_is_c1), "bad vtable stub");
286 unsigned int h = VtableStubs::hash(is_vtable_stub, vtable_index, caller_is_c1);
287 // Insert s at the beginning of the corresponding list.
288 s->set_next(AtomicAccess::load(&_table[h]));
289 // Make sure that concurrent readers not taking the mutex observe the writing of "next".
290 AtomicAccess::release_store(&_table[h], s);
291 }
292
293 VtableStub* VtableStubs::entry_point(address pc) {
294 // The pc may or may not be the entry point for a VtableStub. Use unsafe_hash
295 // to generate the hash that would have been used if it was. The lookup in the
296 // _table will only succeed if there is a VtableStub with an entry point at
297 // the pc.
298 MutexLocker ml(VtableStubs_lock, Mutex::_no_safepoint_check_flag);
299 VtableStub* stub = (VtableStub*)(pc - VtableStub::entry_offset());
300 uint hash = VtableStubs::unsafe_hash(pc, stub->caller_is_c1());
301 VtableStub* s;
302 for (s = AtomicAccess::load(&_table[hash]); s != nullptr && s->entry_point() != pc; s = s->next()) {}
303 return (s != nullptr && s->entry_point() == pc) ? s : nullptr;
304 }
305
306 bool VtableStubs::contains(address pc) {
307 // simple solution for now - we may want to use
308 // a faster way if this function is called often
309 return stub_containing(pc) != nullptr;
310 }
311
312
313 VtableStub* VtableStubs::stub_containing(address pc) {
314 for (int i = 0; i < N; i++) {
315 for (VtableStub* s = AtomicAccess::load_acquire(&_table[i]); s != nullptr; s = s->next()) {
316 if (s->contains(pc)) return s;
317 }
318 }
319 return nullptr;
320 }
321
322 void vtableStubs_init() {
323 VtableStubs::initialize();
324 }
325
326 void VtableStubs::vtable_stub_do(void f(VtableStub*)) {
327 for (int i = 0; i < N; i++) {
328 for (VtableStub* s = AtomicAccess::load_acquire(&_table[i]); s != nullptr; s = s->next()) {
329 f(s);
330 }
331 }
332 }
333
334
335 //-----------------------------------------------------------------------------------------------------
336 // Non-product code
337 #ifndef PRODUCT
338
339 extern "C" void bad_compiled_vtable_index(JavaThread* thread, oop receiver, int index) {
340 ResourceMark rm;
341 Klass* klass = receiver->klass();
342 InstanceKlass* ik = InstanceKlass::cast(klass);
343 klassVtable vt = ik->vtable();
344 ik->print();
345 fatal("bad compiled vtable dispatch: receiver " INTPTR_FORMAT ", "
346 "index %d (vtable length %d)",
347 p2i(receiver), index, vt.length());
348 }
349
350 #endif // PRODUCT