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. 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 #include "cds/archiveBuilder.hpp" 26 #include "cds/metaspaceShared.hpp" 27 #include "classfile/altHashing.hpp" 28 #include "classfile/classLoaderData.hpp" 29 #include "classfile/vmSymbols.hpp" 30 #include "gc/shared/collectedHeap.hpp" 31 #include "logging/log.hpp" 32 #include "logging/logStream.hpp" 33 #include "memory/allocation.inline.hpp" 34 #include "memory/resourceArea.hpp" 35 #include "memory/universe.hpp" 36 #include "oops/symbol.hpp" 37 #include "runtime/atomic.hpp" 38 #include "runtime/mutexLocker.hpp" 39 #include "runtime/os.hpp" 40 #include "runtime/signature.hpp" 41 #include "utilities/stringUtils.hpp" 42 #include "utilities/utf8.hpp" 43 44 Symbol* Symbol::_vm_symbols[vmSymbols::number_of_symbols()]; 45 46 uint32_t Symbol::pack_hash_and_refcount(short hash, int refcount) { 47 STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1)); 48 assert(refcount >= 0, "negative refcount"); 49 assert(refcount <= PERM_REFCOUNT, "invalid refcount"); 50 uint32_t hi = hash; 51 uint32_t lo = refcount; 52 return (hi << 16) | lo; 53 } 54 55 Symbol::Symbol(const u1* name, int length, int refcount) { 56 assert(length <= max_length(), "SymbolTable should have caught this!"); 57 _hash_and_refcount = pack_hash_and_refcount((short)os::random(), refcount); 58 _length = (u2)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 // This copies the symbol when it is added to the ConcurrentHashTable. 69 Symbol::Symbol(const Symbol& s1) { 70 _hash_and_refcount = s1._hash_and_refcount; 71 _length = s1._length; 72 memcpy(_body, s1._body, _length); 73 } 74 75 #if INCLUDE_CDS 76 void Symbol::update_identity_hash() { 77 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 78 _hash_and_refcount = pack_hash_and_refcount((short)ArchiveBuilder::current()->entropy(), PERM_REFCOUNT); 79 } 80 81 void Symbol::set_permanent() { 82 // This is called at a safepoint during dumping of a dynamic CDS archive. 83 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 84 _hash_and_refcount = pack_hash_and_refcount(extract_hash(_hash_and_refcount), PERM_REFCOUNT); 85 } 86 #endif 87 88 Symbol* Symbol::fundamental_name(TRAPS) { 89 if (char_at(0) == JVM_SIGNATURE_CLASS && ends_with(JVM_SIGNATURE_ENDCLASS)) { 90 return SymbolTable::new_symbol(this, 1, utf8_length() - 1); 91 } else { 92 // reference count is incremented to be consistent with the behavior with 93 // the SymbolTable::new_symbol() call above 94 this->increment_refcount(); 95 return this; 96 } 97 } 98 99 bool Symbol::is_same_fundamental_type(Symbol* s) const { 100 if (this == s) return true; 101 if (utf8_length() < 3) return false; 102 int offset1, offset2, len; 103 if (ends_with(JVM_SIGNATURE_ENDCLASS)) { 104 if (char_at(0) != JVM_SIGNATURE_CLASS) return false; 105 offset1 = 1; 106 len = utf8_length() - 2; 107 } else { 108 offset1 = 0; 109 len = utf8_length(); 110 } 111 if (ends_with(JVM_SIGNATURE_ENDCLASS)) { 112 if (s->char_at(0) != JVM_SIGNATURE_CLASS) return false; 113 offset2 = 1; 114 } else { 115 offset2 = 0; 116 } 117 if ((offset2 + len) > s->utf8_length()) return false; 118 if ((utf8_length() - offset1 * 2) != (s->utf8_length() - offset2 * 2)) 119 return false; 120 int l = len; 121 while (l-- > 0) { 122 if (char_at(offset1 + l) != s->char_at(offset2 + l)) 123 return false; 124 } 125 return true; 126 } 127 128 // ------------------------------------------------------------------ 129 // Symbol::index_of 130 // 131 // Test if we have the give substring at or after the i-th char of this 132 // symbol's utf8 bytes. 133 // Return -1 on failure. Otherwise return the first index where substr occurs. 134 int Symbol::index_of_at(int i, const char* substr, int substr_len) const { 135 assert(i >= 0 && i <= utf8_length(), "oob"); 136 if (substr_len <= 0) return 0; 137 char first_char = substr[0]; 138 address bytes = (address) ((Symbol*)this)->base(); 139 address limit = bytes + utf8_length() - substr_len; // inclusive limit 140 address scan = bytes + i; 141 if (scan > limit) 142 return -1; 143 for (; scan <= limit; scan++) { 144 scan = (address) memchr(scan, first_char, (limit + 1 - scan)); 145 if (scan == nullptr) 146 return -1; // not found 147 assert(scan >= bytes+i && scan <= limit, "scan oob"); 148 if (substr_len <= 2 149 ? (char) scan[substr_len-1] == substr[substr_len-1] 150 : memcmp(scan+1, substr+1, substr_len-1) == 0) { 151 return (int)(scan - bytes); 152 } 153 } 154 return -1; 155 } 156 157 bool Symbol::is_star_match(const char* pattern) const { 158 if (strchr(pattern, '*') == nullptr) { 159 return equals(pattern); 160 } else { 161 ResourceMark rm; 162 char* buf = as_C_string(); 163 return StringUtils::is_star_match(pattern, buf); 164 } 165 } 166 167 char* Symbol::as_C_string(char* buf, int size) const { 168 if (size > 0) { 169 int len = MIN2(size - 1, utf8_length()); 170 for (int i = 0; i < len; i++) { 171 buf[i] = char_at(i); 172 } 173 buf[len] = '\0'; 174 } 175 return buf; 176 } 177 178 char* Symbol::as_C_string() const { 179 int len = utf8_length(); 180 char* str = NEW_RESOURCE_ARRAY(char, len + 1); 181 return as_C_string(str, len + 1); 182 } 183 184 void Symbol::print_utf8_on(outputStream* st) const { 185 st->print("%s", as_C_string()); 186 } 187 188 void Symbol::print_symbol_on(outputStream* st) const { 189 char *s; 190 st = st ? st : tty; 191 { 192 // ResourceMark may not affect st->print(). If st is a string 193 // stream it could resize, using the same resource arena. 194 ResourceMark rm; 195 s = as_quoted_ascii(); 196 s = os::strdup(s); 197 } 198 if (s == nullptr) { 199 st->print("(null)"); 200 } else { 201 st->print("%s", s); 202 os::free(s); 203 } 204 } 205 206 char* Symbol::as_quoted_ascii() const { 207 const char *ptr = (const char *)&_body[0]; 208 size_t quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length()); 209 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1); 210 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1); 211 return result; 212 } 213 214 jchar* Symbol::as_unicode(int& length) const { 215 Symbol* this_ptr = (Symbol*)this; 216 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length()); 217 jchar* result = NEW_RESOURCE_ARRAY(jchar, length); 218 if (length > 0) { 219 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length); 220 } 221 return result; 222 } 223 224 const char* Symbol::as_klass_external_name(char* buf, int size) const { 225 if (size > 0) { 226 char* str = as_C_string(buf, size); 227 int length = (int)strlen(str); 228 // Turn all '/'s into '.'s (also for array klasses) 229 for (int index = 0; index < length; index++) { 230 if (str[index] == JVM_SIGNATURE_SLASH) { 231 str[index] = JVM_SIGNATURE_DOT; 232 } 233 } 234 return str; 235 } else { 236 return buf; 237 } 238 } 239 240 const char* Symbol::as_klass_external_name() const { 241 char* str = as_C_string(); 242 int length = (int)strlen(str); 243 // Turn all '/'s into '.'s (also for array klasses) 244 for (int index = 0; index < length; index++) { 245 if (str[index] == JVM_SIGNATURE_SLASH) { 246 str[index] = JVM_SIGNATURE_DOT; 247 } 248 } 249 return str; 250 } 251 252 static void print_class(outputStream *os, const SignatureStream& ss) { 253 int sb = ss.raw_symbol_begin(), se = ss.raw_symbol_end(); 254 for (int i = sb; i < se; ++i) { 255 char ch = ss.raw_char_at(i); 256 if (ch == JVM_SIGNATURE_SLASH) { 257 os->put(JVM_SIGNATURE_DOT); 258 } else { 259 os->put(ch); 260 } 261 } 262 } 263 264 static void print_array(outputStream *os, SignatureStream& ss) { 265 int dimensions = ss.skip_array_prefix(); 266 assert(dimensions > 0, ""); 267 if (ss.is_reference()) { 268 print_class(os, ss); 269 } else { 270 os->print("%s", type2name(ss.type())); 271 } 272 for (int i = 0; i < dimensions; ++i) { 273 os->print("[]"); 274 } 275 } 276 277 void Symbol::print_as_signature_external_return_type(outputStream *os) { 278 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 279 if (ss.at_return_type()) { 280 if (ss.is_array()) { 281 print_array(os, ss); 282 } else if (ss.is_reference()) { 283 print_class(os, ss); 284 } else { 285 os->print("%s", type2name(ss.type())); 286 } 287 } 288 } 289 } 290 291 void Symbol::print_as_signature_external_parameters(outputStream *os) { 292 bool first = true; 293 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 294 if (ss.at_return_type()) break; 295 if (!first) { os->print(", "); } 296 if (ss.is_array()) { 297 print_array(os, ss); 298 } else if (ss.is_reference()) { 299 print_class(os, ss); 300 } else { 301 os->print("%s", type2name(ss.type())); 302 } 303 first = false; 304 } 305 } 306 307 void Symbol::print_as_field_external_type(outputStream *os) { 308 SignatureStream ss(this, false); 309 assert(!ss.is_done(), "must have at least one element in field ref"); 310 assert(!ss.at_return_type(), "field ref cannot be a return type"); 311 assert(!Signature::is_method(this), "field ref cannot be a method"); 312 313 if (ss.is_array()) { 314 print_array(os, ss); 315 } else if (ss.is_reference()) { 316 print_class(os, ss); 317 } else { 318 os->print("%s", type2name(ss.type())); 319 } 320 #ifdef ASSERT 321 ss.next(); 322 assert(ss.is_done(), "must have at most one element in field ref"); 323 #endif 324 } 325 326 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero 327 // a thread could be concurrently removing the Symbol. This is used during SymbolTable 328 // lookup to avoid reviving a dead Symbol. 329 bool Symbol::try_increment_refcount() { 330 uint32_t found = _hash_and_refcount; 331 while (true) { 332 uint32_t old_value = found; 333 int refc = extract_refcount(old_value); 334 if (refc == PERM_REFCOUNT) { 335 return true; // sticky max or created permanent 336 } else if (refc == 0) { 337 return false; // dead, can't revive. 338 } else { 339 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value + 1); 340 if (found == old_value) { 341 return true; // successfully updated. 342 } 343 // refcount changed, try again. 344 } 345 } 346 } 347 348 // The increment_refcount() is called when not doing lookup. It is assumed that you 349 // have a symbol with a non-zero refcount and it can't become zero while referenced by 350 // this caller. 351 void Symbol::increment_refcount() { 352 if (!try_increment_refcount()) { 353 print(); 354 fatal("refcount has gone to zero"); 355 } 356 #ifndef PRODUCT 357 if (refcount() != PERM_REFCOUNT) { // not a permanent symbol 358 NOT_PRODUCT(Atomic::inc(&_total_count);) 359 } 360 #endif 361 } 362 363 // Decrement refcount potentially while racing increment, so we need 364 // to check the value after attempting to decrement so that if another 365 // thread increments to PERM_REFCOUNT the value is not decremented. 366 void Symbol::decrement_refcount() { 367 uint32_t found = _hash_and_refcount; 368 while (true) { 369 uint32_t old_value = found; 370 int refc = extract_refcount(old_value); 371 if (refc == PERM_REFCOUNT) { 372 return; // refcount is permanent, permanent is sticky 373 } else if (refc == 0) { 374 print(); 375 fatal("refcount underflow"); 376 return; 377 } else { 378 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value - 1); 379 if (found == old_value) { 380 return; // successfully updated. 381 } 382 // refcount changed, try again. 383 } 384 } 385 } 386 387 void Symbol::make_permanent() { 388 uint32_t found = _hash_and_refcount; 389 while (true) { 390 uint32_t old_value = found; 391 int refc = extract_refcount(old_value); 392 if (refc == PERM_REFCOUNT) { 393 return; // refcount is permanent, permanent is sticky 394 } else if (refc == 0) { 395 print(); 396 fatal("refcount underflow"); 397 return; 398 } else { 399 short hash = extract_hash(old_value); 400 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, pack_hash_and_refcount(hash, PERM_REFCOUNT)); 401 if (found == old_value) { 402 return; // successfully updated. 403 } 404 // refcount changed, try again. 405 } 406 } 407 } 408 409 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) { 410 if (log_is_enabled(Trace, cds)) { 411 LogStream trace_stream(Log(cds)::trace()); 412 trace_stream.print("Iter(Symbol): %p ", this); 413 print_value_on(&trace_stream); 414 trace_stream.cr(); 415 } 416 } 417 418 void Symbol::print_on(outputStream* st) const { 419 st->print("Symbol: '"); 420 print_symbol_on(st); 421 st->print("'"); 422 st->print(" count %d", refcount()); 423 } 424 425 void Symbol::print() const { print_on(tty); } 426 427 // The print_value functions are present in all builds, to support the 428 // disassembler and error reporting. 429 void Symbol::print_value_on(outputStream* st) const { 430 st->print_raw("'", 1); 431 st->print_raw((const char*)base(), utf8_length()); 432 st->print_raw("'", 1); 433 } 434 435 void Symbol::print_value() const { print_value_on(tty); } 436 437 bool Symbol::is_valid(Symbol* s) { 438 if (!is_aligned(s, sizeof(MetaWord))) return false; 439 if ((size_t)s < os::min_page_size()) return false; 440 441 if (!os::is_readable_range(s, s + 1)) return false; 442 443 // Symbols are not allocated in Java heap. 444 if (Universe::heap()->is_in(s)) return false; 445 446 int len = s->utf8_length(); 447 if (len < 0) return false; 448 449 jbyte* bytes = (jbyte*) s->bytes(); 450 return os::is_readable_range(bytes, bytes + len); 451 } 452 453 // SymbolTable prints this in its statistics 454 NOT_PRODUCT(size_t Symbol::_total_count = 0;) 455 456 #ifndef PRODUCT 457 bool Symbol::is_valid_id(vmSymbolID vm_symbol_id) { 458 return vmSymbols::is_valid_id(vm_symbol_id); 459 } 460 #endif