1 /* 2 * Copyright (c) 1997, 2023, 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 "precompiled.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 _hash_and_refcount = pack_hash_and_refcount((short)os::random(), refcount); 57 _length = (u2)length; 58 // _body[0..1] are allocated in the header just by coincidence in the current 59 // implementation of Symbol. They are read by identity_hash(), so make sure they 60 // are initialized. 61 // No other code should assume that _body[0..1] are always allocated. E.g., do 62 // not unconditionally read base()[0] as that will be invalid for an empty Symbol. 63 _body[0] = _body[1] = 0; 64 memcpy(_body, name, length); 65 } 66 67 // This copies the symbol when it is added to the ConcurrentHashTable. 68 Symbol::Symbol(const Symbol& s1) { 69 _hash_and_refcount = s1._hash_and_refcount; 70 _length = s1._length; 71 memcpy(_body, s1._body, _length); 72 } 73 74 #if INCLUDE_CDS 75 void Symbol::update_identity_hash() { 76 // This is called at a safepoint during dumping of a static CDS archive. The caller should have 77 // called os::init_random() with a deterministic seed and then iterate all archived Symbols in 78 // a deterministic order. 79 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 80 _hash_and_refcount = pack_hash_and_refcount((short)os::random(), PERM_REFCOUNT); 81 } 82 83 void Symbol::set_permanent() { 84 // This is called at a safepoint during dumping of a dynamic CDS archive. 85 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 86 _hash_and_refcount = pack_hash_and_refcount(extract_hash(_hash_and_refcount), PERM_REFCOUNT); 87 } 88 #endif 89 90 Symbol* Symbol::fundamental_name(TRAPS) { 91 if (char_at(0) == JVM_SIGNATURE_CLASS && ends_with(JVM_SIGNATURE_ENDCLASS)) { 92 return SymbolTable::new_symbol(this, 1, utf8_length() - 1); 93 } else { 94 // reference count is incremented to be consistent with the behavior with 95 // the SymbolTable::new_symbol() call above 96 this->increment_refcount(); 97 return this; 98 } 99 } 100 101 bool Symbol::is_same_fundamental_type(Symbol* s) const { 102 if (this == s) return true; 103 if (utf8_length() < 3) return false; 104 int offset1, offset2, len; 105 if (ends_with(JVM_SIGNATURE_ENDCLASS)) { 106 if (char_at(0) != JVM_SIGNATURE_CLASS) return false; 107 offset1 = 1; 108 len = utf8_length() - 2; 109 } else { 110 offset1 = 0; 111 len = utf8_length(); 112 } 113 if (ends_with(JVM_SIGNATURE_ENDCLASS)) { 114 if (s->char_at(0) != JVM_SIGNATURE_CLASS) return false; 115 offset2 = 1; 116 } else { 117 offset2 = 0; 118 } 119 if ((offset2 + len) > s->utf8_length()) return false; 120 if ((utf8_length() - offset1 * 2) != (s->utf8_length() - offset2 * 2)) 121 return false; 122 int l = len; 123 while (l-- > 0) { 124 if (char_at(offset1 + l) != s->char_at(offset2 + l)) 125 return false; 126 } 127 return true; 128 } 129 130 // ------------------------------------------------------------------ 131 // Symbol::index_of 132 // 133 // Test if we have the give substring at or after the i-th char of this 134 // symbol's utf8 bytes. 135 // Return -1 on failure. Otherwise return the first index where substr occurs. 136 int Symbol::index_of_at(int i, const char* substr, int substr_len) const { 137 assert(i >= 0 && i <= utf8_length(), "oob"); 138 if (substr_len <= 0) return 0; 139 char first_char = substr[0]; 140 address bytes = (address) ((Symbol*)this)->base(); 141 address limit = bytes + utf8_length() - substr_len; // inclusive limit 142 address scan = bytes + i; 143 if (scan > limit) 144 return -1; 145 for (; scan <= limit; scan++) { 146 scan = (address) memchr(scan, first_char, (limit + 1 - scan)); 147 if (scan == nullptr) 148 return -1; // not found 149 assert(scan >= bytes+i && scan <= limit, "scan oob"); 150 if (substr_len <= 2 151 ? (char) scan[substr_len-1] == substr[substr_len-1] 152 : memcmp(scan+1, substr+1, substr_len-1) == 0) { 153 return (int)(scan - bytes); 154 } 155 } 156 return -1; 157 } 158 159 bool Symbol::is_star_match(const char* pattern) const { 160 if (strchr(pattern, '*') == nullptr) { 161 return equals(pattern); 162 } else { 163 ResourceMark rm; 164 char* buf = as_C_string(); 165 return StringUtils::is_star_match(pattern, buf); 166 } 167 } 168 169 char* Symbol::as_C_string(char* buf, int size) const { 170 if (size > 0) { 171 int len = MIN2(size - 1, utf8_length()); 172 for (int i = 0; i < len; i++) { 173 buf[i] = char_at(i); 174 } 175 buf[len] = '\0'; 176 } 177 return buf; 178 } 179 180 char* Symbol::as_C_string() const { 181 int len = utf8_length(); 182 char* str = NEW_RESOURCE_ARRAY(char, len + 1); 183 return as_C_string(str, len + 1); 184 } 185 186 void Symbol::print_utf8_on(outputStream* st) const { 187 st->print("%s", as_C_string()); 188 } 189 190 void Symbol::print_symbol_on(outputStream* st) const { 191 char *s; 192 st = st ? st : tty; 193 { 194 // ResourceMark may not affect st->print(). If st is a string 195 // stream it could resize, using the same resource arena. 196 ResourceMark rm; 197 s = as_quoted_ascii(); 198 s = os::strdup(s); 199 } 200 if (s == nullptr) { 201 st->print("(null)"); 202 } else { 203 st->print("%s", s); 204 os::free(s); 205 } 206 } 207 208 char* Symbol::as_quoted_ascii() const { 209 const char *ptr = (const char *)&_body[0]; 210 int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length()); 211 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1); 212 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1); 213 return result; 214 } 215 216 jchar* Symbol::as_unicode(int& length) const { 217 Symbol* this_ptr = (Symbol*)this; 218 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length()); 219 jchar* result = NEW_RESOURCE_ARRAY(jchar, length); 220 if (length > 0) { 221 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length); 222 } 223 return result; 224 } 225 226 const char* Symbol::as_klass_external_name(char* buf, int size) const { 227 if (size > 0) { 228 char* str = as_C_string(buf, size); 229 int length = (int)strlen(str); 230 // Turn all '/'s into '.'s (also for array klasses) 231 for (int index = 0; index < length; index++) { 232 if (str[index] == JVM_SIGNATURE_SLASH) { 233 str[index] = JVM_SIGNATURE_DOT; 234 } 235 } 236 return str; 237 } else { 238 return buf; 239 } 240 } 241 242 const char* Symbol::as_klass_external_name() const { 243 char* str = as_C_string(); 244 int length = (int)strlen(str); 245 // Turn all '/'s into '.'s (also for array klasses) 246 for (int index = 0; index < length; index++) { 247 if (str[index] == JVM_SIGNATURE_SLASH) { 248 str[index] = JVM_SIGNATURE_DOT; 249 } 250 } 251 return str; 252 } 253 254 static void print_class(outputStream *os, const SignatureStream& ss) { 255 int sb = ss.raw_symbol_begin(), se = ss.raw_symbol_end(); 256 for (int i = sb; i < se; ++i) { 257 char ch = ss.raw_char_at(i); 258 if (ch == JVM_SIGNATURE_SLASH) { 259 os->put(JVM_SIGNATURE_DOT); 260 } else { 261 os->put(ch); 262 } 263 } 264 } 265 266 static void print_array(outputStream *os, SignatureStream& ss) { 267 int dimensions = ss.skip_array_prefix(); 268 assert(dimensions > 0, ""); 269 if (ss.is_reference()) { 270 print_class(os, ss); 271 } else { 272 os->print("%s", type2name(ss.type())); 273 } 274 for (int i = 0; i < dimensions; ++i) { 275 os->print("[]"); 276 } 277 } 278 279 void Symbol::print_as_signature_external_return_type(outputStream *os) { 280 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 281 if (ss.at_return_type()) { 282 if (ss.is_array()) { 283 print_array(os, ss); 284 } else if (ss.is_reference()) { 285 print_class(os, ss); 286 } else { 287 os->print("%s", type2name(ss.type())); 288 } 289 } 290 } 291 } 292 293 void Symbol::print_as_signature_external_parameters(outputStream *os) { 294 bool first = true; 295 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 296 if (ss.at_return_type()) break; 297 if (!first) { os->print(", "); } 298 if (ss.is_array()) { 299 print_array(os, ss); 300 } else if (ss.is_reference()) { 301 print_class(os, ss); 302 } else { 303 os->print("%s", type2name(ss.type())); 304 } 305 first = false; 306 } 307 } 308 309 void Symbol::print_as_field_external_type(outputStream *os) { 310 SignatureStream ss(this, false); 311 assert(!ss.is_done(), "must have at least one element in field ref"); 312 assert(!ss.at_return_type(), "field ref cannot be a return type"); 313 assert(!Signature::is_method(this), "field ref cannot be a method"); 314 315 if (ss.is_array()) { 316 print_array(os, ss); 317 } else if (ss.is_reference()) { 318 print_class(os, ss); 319 } else { 320 os->print("%s", type2name(ss.type())); 321 } 322 #ifdef ASSERT 323 ss.next(); 324 assert(ss.is_done(), "must have at most one element in field ref"); 325 #endif 326 } 327 328 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero 329 // a thread could be concurrently removing the Symbol. This is used during SymbolTable 330 // lookup to avoid reviving a dead Symbol. 331 bool Symbol::try_increment_refcount() { 332 uint32_t found = _hash_and_refcount; 333 while (true) { 334 uint32_t old_value = found; 335 int refc = extract_refcount(old_value); 336 if (refc == PERM_REFCOUNT) { 337 return true; // sticky max or created permanent 338 } else if (refc == 0) { 339 return false; // dead, can't revive. 340 } else { 341 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value + 1); 342 if (found == old_value) { 343 return true; // successfully updated. 344 } 345 // refcount changed, try again. 346 } 347 } 348 } 349 350 // The increment_refcount() is called when not doing lookup. It is assumed that you 351 // have a symbol with a non-zero refcount and it can't become zero while referenced by 352 // this caller. 353 void Symbol::increment_refcount() { 354 if (!try_increment_refcount()) { 355 print(); 356 fatal("refcount has gone to zero"); 357 } 358 #ifndef PRODUCT 359 if (refcount() != PERM_REFCOUNT) { // not a permanent symbol 360 NOT_PRODUCT(Atomic::inc(&_total_count);) 361 } 362 #endif 363 } 364 365 // Decrement refcount potentially while racing increment, so we need 366 // to check the value after attempting to decrement so that if another 367 // thread increments to PERM_REFCOUNT the value is not decremented. 368 void Symbol::decrement_refcount() { 369 uint32_t found = _hash_and_refcount; 370 while (true) { 371 uint32_t old_value = found; 372 int refc = extract_refcount(old_value); 373 if (refc == PERM_REFCOUNT) { 374 return; // refcount is permanent, permanent is sticky 375 } else if (refc == 0) { 376 print(); 377 fatal("refcount underflow"); 378 return; 379 } else { 380 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value - 1); 381 if (found == old_value) { 382 return; // successfully updated. 383 } 384 // refcount changed, try again. 385 } 386 } 387 } 388 389 void Symbol::make_permanent() { 390 uint32_t found = _hash_and_refcount; 391 while (true) { 392 uint32_t old_value = found; 393 int refc = extract_refcount(old_value); 394 if (refc == PERM_REFCOUNT) { 395 return; // refcount is permanent, permanent is sticky 396 } else if (refc == 0) { 397 print(); 398 fatal("refcount underflow"); 399 return; 400 } else { 401 short hash = extract_hash(old_value); 402 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, pack_hash_and_refcount(hash, PERM_REFCOUNT)); 403 if (found == old_value) { 404 return; // successfully updated. 405 } 406 // refcount changed, try again. 407 } 408 } 409 } 410 411 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) { 412 if (log_is_enabled(Trace, cds)) { 413 LogStream trace_stream(Log(cds)::trace()); 414 trace_stream.print("Iter(Symbol): %p ", this); 415 print_value_on(&trace_stream); 416 trace_stream.cr(); 417 } 418 } 419 420 void Symbol::print_on(outputStream* st) const { 421 st->print("Symbol: '"); 422 print_symbol_on(st); 423 st->print("'"); 424 st->print(" count %d", refcount()); 425 } 426 427 void Symbol::print() const { print_on(tty); } 428 429 // The print_value functions are present in all builds, to support the 430 // disassembler and error reporting. 431 void Symbol::print_value_on(outputStream* st) const { 432 st->print_raw("'", 1); 433 st->print_raw((const char*)base(), utf8_length()); 434 st->print_raw("'", 1); 435 } 436 437 void Symbol::print_value() const { print_value_on(tty); } 438 439 bool Symbol::is_valid(Symbol* s) { 440 if (!is_aligned(s, sizeof(MetaWord))) return false; 441 if ((size_t)s < os::min_page_size()) return false; 442 443 if (!os::is_readable_range(s, s + 1)) return false; 444 445 // Symbols are not allocated in Java heap. 446 if (Universe::heap()->is_in(s)) return false; 447 448 int len = s->utf8_length(); 449 if (len < 0) return false; 450 451 jbyte* bytes = (jbyte*) s->bytes(); 452 return os::is_readable_range(bytes, bytes + len); 453 } 454 455 // SymbolTable prints this in its statistics 456 NOT_PRODUCT(size_t Symbol::_total_count = 0;) 457 458 #ifndef PRODUCT 459 bool Symbol::is_valid_id(vmSymbolID vm_symbol_id) { 460 return vmSymbols::is_valid_id(vm_symbol_id); 461 } 462 #endif