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