1 /* 2 * Copyright (c) 1997, 2022, 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 26 #include "precompiled.hpp" 27 #include "cds/metaspaceShared.hpp" 28 #include "classfile/altHashing.hpp" 29 #include "classfile/classLoaderData.hpp" 30 #include "classfile/vmSymbols.hpp" 31 #include "gc/shared/collectedHeap.hpp" 32 #include "logging/log.hpp" 33 #include "logging/logStream.hpp" 34 #include "memory/allocation.inline.hpp" 35 #include "memory/resourceArea.hpp" 36 #include "memory/universe.hpp" 37 #include "oops/symbol.hpp" 38 #include "runtime/atomic.hpp" 39 #include "runtime/mutexLocker.hpp" 40 #include "runtime/os.hpp" 41 #include "runtime/signature.hpp" 42 #include "utilities/stringUtils.hpp" 43 #include "utilities/utf8.hpp" 44 45 Symbol* Symbol::_vm_symbols[vmSymbols::number_of_symbols()]; 46 47 uint32_t Symbol::pack_hash_and_refcount(short hash, int refcount) { 48 STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1)); 49 assert(refcount >= 0, "negative refcount"); 50 assert(refcount <= PERM_REFCOUNT, "invalid refcount"); 51 uint32_t hi = hash; 52 uint32_t lo = refcount; 53 return (hi << 16) | lo; 54 } 55 56 Symbol::Symbol(const u1* name, int length, int refcount) { 57 _hash_and_refcount = pack_hash_and_refcount((short)os::random(), refcount); 58 _length = length; 59 // _body[0..1] are allocated in the header just by coincidence in the current 60 // implementation of Symbol. They are read by identity_hash(), so make sure they 61 // are initialized. 62 // No other code should assume that _body[0..1] are always allocated. E.g., do 63 // not unconditionally read base()[0] as that will be invalid for an empty Symbol. 64 _body[0] = _body[1] = 0; 65 memcpy(_body, name, length); 66 } 67 68 void* Symbol::operator new(size_t sz, int len) throw() { 69 #if INCLUDE_CDS 70 if (DumpSharedSpaces) { 71 MutexLocker ml(DumpRegion_lock, Mutex::_no_safepoint_check_flag); 72 // To get deterministic output from -Xshare:dump, we ensure that Symbols are allocated in 73 // increasing addresses. When the symbols are copied into the archive, we preserve their 74 // relative address order (sorted, see ArchiveBuilder::gather_klasses_and_symbols). 75 // 76 // We cannot use arena because arena chunks are allocated by the OS. As a result, for example, 77 // the archived symbol of "java/lang/Object" may sometimes be lower than "java/lang/String", and 78 // sometimes be higher. This would cause non-deterministic contents in the archive. 79 DEBUG_ONLY(static void* last = 0); 80 void* p = (void*)MetaspaceShared::symbol_space_alloc(size(len)*wordSize); 81 assert(p > last, "must increase monotonically"); 82 DEBUG_ONLY(last = p); 83 return p; 84 } 85 #endif 86 int alloc_size = size(len)*wordSize; 87 address res = (address) AllocateHeap(alloc_size, mtSymbol); 88 return res; 89 } 90 91 void* Symbol::operator new(size_t sz, int len, Arena* arena) throw() { 92 int alloc_size = size(len)*wordSize; 93 address res = (address)arena->AmallocWords(alloc_size); 94 return res; 95 } 96 97 void Symbol::operator delete(void *p) { 98 assert(((Symbol*)p)->refcount() == 0, "should not call this"); 99 FreeHeap(p); 100 } 101 102 #if INCLUDE_CDS 103 void Symbol::update_identity_hash() { 104 // This is called at a safepoint during dumping of a static CDS archive. The caller should have 105 // called os::init_random() with a deterministic seed and then iterate all archived Symbols in 106 // a deterministic order. 107 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 108 _hash_and_refcount = pack_hash_and_refcount((short)os::random(), PERM_REFCOUNT); 109 } 110 111 void Symbol::set_permanent() { 112 // This is called at a safepoint during dumping of a dynamic CDS archive. 113 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 114 _hash_and_refcount = pack_hash_and_refcount(extract_hash(_hash_and_refcount), PERM_REFCOUNT); 115 } 116 #endif 117 118 bool Symbol::is_Q_signature() const { 119 int len = utf8_length(); 120 return len > 2 && char_at(0) == JVM_SIGNATURE_PRIMITIVE_OBJECT && char_at(len - 1) == JVM_SIGNATURE_ENDCLASS; 121 } 122 123 bool Symbol::is_Q_array_signature() const { 124 int l = utf8_length(); 125 if (l < 2 || char_at(0) != JVM_SIGNATURE_ARRAY || char_at(l - 1) != JVM_SIGNATURE_ENDCLASS) { 126 return false; 127 } 128 for (int i = 1; i < (l - 2); i++) { 129 char c = char_at(i); 130 if (c == JVM_SIGNATURE_PRIMITIVE_OBJECT) { 131 return true; 132 } 133 if (c != JVM_SIGNATURE_ARRAY) { 134 return false; 135 } 136 } 137 return false; 138 } 139 140 bool Symbol::is_Q_method_signature() const { 141 assert(SignatureVerifier::is_valid_method_signature(this), "must be"); 142 int len = utf8_length(); 143 if (len > 4 && char_at(0) == JVM_SIGNATURE_FUNC) { 144 for (int i=1; i<len-3; i++) { // Must end with ")Qx;", where x is at least one character or more. 145 if (char_at(i) == JVM_SIGNATURE_ENDFUNC && char_at(i+1) == JVM_SIGNATURE_PRIMITIVE_OBJECT) { 146 return true; 147 } 148 } 149 } 150 return false; 151 } 152 153 Symbol* Symbol::fundamental_name(TRAPS) { 154 if ((char_at(0) == JVM_SIGNATURE_PRIMITIVE_OBJECT || char_at(0) == JVM_SIGNATURE_CLASS) && ends_with(JVM_SIGNATURE_ENDCLASS)) { 155 return SymbolTable::new_symbol(this, 1, utf8_length() - 1); 156 } else { 157 // reference count is incremented to be consistent with the behavior with 158 // the SymbolTable::new_symbol() call above 159 this->increment_refcount(); 160 return this; 161 } 162 } 163 164 bool Symbol::is_same_fundamental_type(Symbol* s) const { 165 if (this == s) return true; 166 if (utf8_length() < 3) return false; 167 int offset1, offset2, len; 168 if (ends_with(JVM_SIGNATURE_ENDCLASS)) { 169 if (char_at(0) != JVM_SIGNATURE_PRIMITIVE_OBJECT && char_at(0) != JVM_SIGNATURE_CLASS) return false; 170 offset1 = 1; 171 len = utf8_length() - 2; 172 } else { 173 offset1 = 0; 174 len = utf8_length(); 175 } 176 if (ends_with(JVM_SIGNATURE_ENDCLASS)) { 177 if (s->char_at(0) != JVM_SIGNATURE_PRIMITIVE_OBJECT && s->char_at(0) != JVM_SIGNATURE_CLASS) return false; 178 offset2 = 1; 179 } else { 180 offset2 = 0; 181 } 182 if ((offset2 + len) > s->utf8_length()) return false; 183 if ((utf8_length() - offset1 * 2) != (s->utf8_length() - offset2 * 2)) 184 return false; 185 int l = len; 186 while (l-- > 0) { 187 if (char_at(offset1 + l) != s->char_at(offset2 + l)) 188 return false; 189 } 190 return true; 191 } 192 193 // ------------------------------------------------------------------ 194 // Symbol::index_of 195 // 196 // Test if we have the give substring at or after the i-th char of this 197 // symbol's utf8 bytes. 198 // Return -1 on failure. Otherwise return the first index where substr occurs. 199 int Symbol::index_of_at(int i, const char* substr, int substr_len) const { 200 assert(i >= 0 && i <= utf8_length(), "oob"); 201 if (substr_len <= 0) return 0; 202 char first_char = substr[0]; 203 address bytes = (address) ((Symbol*)this)->base(); 204 address limit = bytes + utf8_length() - substr_len; // inclusive limit 205 address scan = bytes + i; 206 if (scan > limit) 207 return -1; 208 for (; scan <= limit; scan++) { 209 scan = (address) memchr(scan, first_char, (limit + 1 - scan)); 210 if (scan == NULL) 211 return -1; // not found 212 assert(scan >= bytes+i && scan <= limit, "scan oob"); 213 if (substr_len <= 2 214 ? (char) scan[substr_len-1] == substr[substr_len-1] 215 : memcmp(scan+1, substr+1, substr_len-1) == 0) { 216 return (int)(scan - bytes); 217 } 218 } 219 return -1; 220 } 221 222 bool Symbol::is_star_match(const char* pattern) const { 223 if (strchr(pattern, '*') == NULL) { 224 return equals(pattern); 225 } else { 226 ResourceMark rm; 227 char* buf = as_C_string(); 228 return StringUtils::is_star_match(pattern, buf); 229 } 230 } 231 232 char* Symbol::as_C_string(char* buf, int size) const { 233 if (size > 0) { 234 int len = MIN2(size - 1, utf8_length()); 235 for (int i = 0; i < len; i++) { 236 buf[i] = char_at(i); 237 } 238 buf[len] = '\0'; 239 } 240 return buf; 241 } 242 243 char* Symbol::as_C_string() const { 244 int len = utf8_length(); 245 char* str = NEW_RESOURCE_ARRAY(char, len + 1); 246 return as_C_string(str, len + 1); 247 } 248 249 void Symbol::print_utf8_on(outputStream* st) const { 250 st->print("%s", as_C_string()); 251 } 252 253 void Symbol::print_symbol_on(outputStream* st) const { 254 char *s; 255 st = st ? st : tty; 256 { 257 // ResourceMark may not affect st->print(). If st is a string 258 // stream it could resize, using the same resource arena. 259 ResourceMark rm; 260 s = as_quoted_ascii(); 261 s = os::strdup(s); 262 } 263 if (s == NULL) { 264 st->print("(null)"); 265 } else { 266 st->print("%s", s); 267 os::free(s); 268 } 269 } 270 271 char* Symbol::as_quoted_ascii() const { 272 const char *ptr = (const char *)&_body[0]; 273 int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length()); 274 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1); 275 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1); 276 return result; 277 } 278 279 jchar* Symbol::as_unicode(int& length) const { 280 Symbol* this_ptr = (Symbol*)this; 281 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length()); 282 jchar* result = NEW_RESOURCE_ARRAY(jchar, length); 283 if (length > 0) { 284 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length); 285 } 286 return result; 287 } 288 289 const char* Symbol::as_klass_external_name(char* buf, int size) const { 290 if (size > 0) { 291 char* str = as_C_string(buf, size); 292 int length = (int)strlen(str); 293 // Turn all '/'s into '.'s (also for array klasses) 294 for (int index = 0; index < length; index++) { 295 if (str[index] == JVM_SIGNATURE_SLASH) { 296 str[index] = JVM_SIGNATURE_DOT; 297 } 298 } 299 return str; 300 } else { 301 return buf; 302 } 303 } 304 305 const char* Symbol::as_klass_external_name() const { 306 char* str = as_C_string(); 307 int length = (int)strlen(str); 308 // Turn all '/'s into '.'s (also for array klasses) 309 for (int index = 0; index < length; index++) { 310 if (str[index] == JVM_SIGNATURE_SLASH) { 311 str[index] = JVM_SIGNATURE_DOT; 312 } 313 } 314 return str; 315 } 316 317 static void print_class(outputStream *os, const SignatureStream& ss) { 318 int sb = ss.raw_symbol_begin(), se = ss.raw_symbol_end(); 319 for (int i = sb; i < se; ++i) { 320 int ch = ss.raw_char_at(i); 321 if (ch == JVM_SIGNATURE_SLASH) { 322 os->put(JVM_SIGNATURE_DOT); 323 } else { 324 os->put(ch); 325 } 326 } 327 } 328 329 static void print_array(outputStream *os, SignatureStream& ss) { 330 int dimensions = ss.skip_array_prefix(); 331 assert(dimensions > 0, ""); 332 if (ss.is_reference()) { 333 print_class(os, ss); 334 } else { 335 os->print("%s", type2name(ss.type())); 336 } 337 for (int i = 0; i < dimensions; ++i) { 338 os->print("[]"); 339 } 340 } 341 342 void Symbol::print_as_signature_external_return_type(outputStream *os) { 343 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 344 if (ss.at_return_type()) { 345 if (ss.is_array()) { 346 print_array(os, ss); 347 } else if (ss.is_reference()) { 348 print_class(os, ss); 349 } else { 350 os->print("%s", type2name(ss.type())); 351 } 352 } 353 } 354 } 355 356 void Symbol::print_as_signature_external_parameters(outputStream *os) { 357 bool first = true; 358 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 359 if (ss.at_return_type()) break; 360 if (!first) { os->print(", "); } 361 if (ss.is_array()) { 362 print_array(os, ss); 363 } else if (ss.is_reference()) { 364 print_class(os, ss); 365 } else { 366 os->print("%s", type2name(ss.type())); 367 } 368 first = false; 369 } 370 } 371 372 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero 373 // a thread could be concurrently removing the Symbol. This is used during SymbolTable 374 // lookup to avoid reviving a dead Symbol. 375 bool Symbol::try_increment_refcount() { 376 uint32_t found = _hash_and_refcount; 377 while (true) { 378 uint32_t old_value = found; 379 int refc = extract_refcount(old_value); 380 if (refc == PERM_REFCOUNT) { 381 return true; // sticky max or created permanent 382 } else if (refc == 0) { 383 return false; // dead, can't revive. 384 } else { 385 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value + 1); 386 if (found == old_value) { 387 return true; // successfully updated. 388 } 389 // refcount changed, try again. 390 } 391 } 392 } 393 394 // The increment_refcount() is called when not doing lookup. It is assumed that you 395 // have a symbol with a non-zero refcount and it can't become zero while referenced by 396 // this caller. 397 void Symbol::increment_refcount() { 398 if (!try_increment_refcount()) { 399 #ifdef ASSERT 400 print(); 401 fatal("refcount has gone to zero"); 402 #endif 403 } 404 #ifndef PRODUCT 405 if (refcount() != PERM_REFCOUNT) { // not a permanent symbol 406 NOT_PRODUCT(Atomic::inc(&_total_count);) 407 } 408 #endif 409 } 410 411 // Decrement refcount potentially while racing increment, so we need 412 // to check the value after attempting to decrement so that if another 413 // thread increments to PERM_REFCOUNT the value is not decremented. 414 void Symbol::decrement_refcount() { 415 uint32_t found = _hash_and_refcount; 416 while (true) { 417 uint32_t old_value = found; 418 int refc = extract_refcount(old_value); 419 if (refc == PERM_REFCOUNT) { 420 return; // refcount is permanent, permanent is sticky 421 } else if (refc == 0) { 422 #ifdef ASSERT 423 print(); 424 fatal("refcount underflow"); 425 #endif 426 return; 427 } else { 428 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value - 1); 429 if (found == old_value) { 430 return; // successfully updated. 431 } 432 // refcount changed, try again. 433 } 434 } 435 } 436 437 void Symbol::make_permanent() { 438 uint32_t found = _hash_and_refcount; 439 while (true) { 440 uint32_t old_value = found; 441 int refc = extract_refcount(old_value); 442 if (refc == PERM_REFCOUNT) { 443 return; // refcount is permanent, permanent is sticky 444 } else if (refc == 0) { 445 #ifdef ASSERT 446 print(); 447 fatal("refcount underflow"); 448 #endif 449 return; 450 } else { 451 int hash = extract_hash(old_value); 452 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, pack_hash_and_refcount(hash, PERM_REFCOUNT)); 453 if (found == old_value) { 454 return; // successfully updated. 455 } 456 // refcount changed, try again. 457 } 458 } 459 } 460 461 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) { 462 if (log_is_enabled(Trace, cds)) { 463 LogStream trace_stream(Log(cds)::trace()); 464 trace_stream.print("Iter(Symbol): %p ", this); 465 print_value_on(&trace_stream); 466 trace_stream.cr(); 467 } 468 } 469 470 void Symbol::print_on(outputStream* st) const { 471 st->print("Symbol: '"); 472 print_symbol_on(st); 473 st->print("'"); 474 st->print(" count %d", refcount()); 475 } 476 477 void Symbol::print() const { print_on(tty); } 478 479 // The print_value functions are present in all builds, to support the 480 // disassembler and error reporting. 481 void Symbol::print_value_on(outputStream* st) const { 482 st->print("'"); 483 for (int i = 0; i < utf8_length(); i++) { 484 st->print("%c", char_at(i)); 485 } 486 st->print("'"); 487 } 488 489 void Symbol::print_value() const { print_value_on(tty); } 490 491 bool Symbol::is_valid(Symbol* s) { 492 if (!is_aligned(s, sizeof(MetaWord))) return false; 493 if ((size_t)s < os::min_page_size()) return false; 494 495 if (!os::is_readable_range(s, s + 1)) return false; 496 497 // Symbols are not allocated in Java heap. 498 if (Universe::heap()->is_in(s)) return false; 499 500 int len = s->utf8_length(); 501 if (len < 0) return false; 502 503 jbyte* bytes = (jbyte*) s->bytes(); 504 return os::is_readable_range(bytes, bytes + len); 505 } 506 507 void Symbol::print_Qvalue_on(outputStream* st) const { 508 st->print("'Q"); 509 for (int i = 0; i < utf8_length(); i++) { 510 st->print("%c", char_at(i)); 511 } 512 st->print(";'"); 513 } 514 515 // SymbolTable prints this in its statistics 516 NOT_PRODUCT(size_t Symbol::_total_count = 0;) 517 518 #ifndef PRODUCT 519 bool Symbol::is_valid_id(vmSymbolID vm_symbol_id) { 520 return vmSymbols::is_valid_id(vm_symbol_id); 521 } 522 #endif