1 /* 2 * Copyright (c) 1997, 2021, 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/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 = 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 void* Symbol::operator new(size_t sz, int len) throw() { 68 #if INCLUDE_CDS 69 if (DumpSharedSpaces) { 70 MutexLocker ml(DumpRegion_lock, Mutex::_no_safepoint_check_flag); 71 // To get deterministic output from -Xshare:dump, we ensure that Symbols are allocated in 72 // increasing addresses. When the symbols are copied into the archive, we preserve their 73 // relative address order (sorted, see ArchiveBuilder::gather_klasses_and_symbols). 74 // 75 // We cannot use arena because arena chunks are allocated by the OS. As a result, for example, 76 // the archived symbol of "java/lang/Object" may sometimes be lower than "java/lang/String", and 77 // sometimes be higher. This would cause non-deterministic contents in the archive. 78 DEBUG_ONLY(static void* last = 0); 79 void* p = (void*)MetaspaceShared::symbol_space_alloc(size(len)*wordSize); 80 assert(p > last, "must increase monotonically"); 81 DEBUG_ONLY(last = p); 82 return p; 83 } 84 #endif 85 int alloc_size = size(len)*wordSize; 86 address res = (address) AllocateHeap(alloc_size, mtSymbol); 87 return res; 88 } 89 90 void* Symbol::operator new(size_t sz, int len, Arena* arena) throw() { 91 int alloc_size = size(len)*wordSize; 92 address res = (address)arena->AmallocWords(alloc_size); 93 return res; 94 } 95 96 void Symbol::operator delete(void *p) { 97 assert(((Symbol*)p)->refcount() == 0, "should not call this"); 98 FreeHeap(p); 99 } 100 101 #if INCLUDE_CDS 102 void Symbol::update_identity_hash() { 103 // This is called at a safepoint during dumping of a static CDS archive. The caller should have 104 // called os::init_random() with a deterministic seed and then iterate all archived Symbols in 105 // a deterministic order. 106 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 107 _hash_and_refcount = pack_hash_and_refcount((short)os::random(), PERM_REFCOUNT); 108 } 109 110 void Symbol::set_permanent() { 111 // This is called at a safepoint during dumping of a dynamic CDS archive. 112 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 113 _hash_and_refcount = pack_hash_and_refcount(extract_hash(_hash_and_refcount), PERM_REFCOUNT); 114 } 115 #endif 116 117 // ------------------------------------------------------------------ 118 // Symbol::index_of 119 // 120 // Finds if the given string is a substring of this symbol's utf8 bytes. 121 // Return -1 on failure. Otherwise return the first index where str occurs. 122 int Symbol::index_of_at(int i, const char* str, int len) const { 123 assert(i >= 0 && i <= utf8_length(), "oob"); 124 if (len <= 0) return 0; 125 char first_char = str[0]; 126 address bytes = (address) ((Symbol*)this)->base(); 127 address limit = bytes + utf8_length() - len; // inclusive limit 128 address scan = bytes + i; 129 if (scan > limit) 130 return -1; 131 for (; scan <= limit; scan++) { 132 scan = (address) memchr(scan, first_char, (limit + 1 - scan)); 133 if (scan == NULL) 134 return -1; // not found 135 assert(scan >= bytes+i && scan <= limit, "scan oob"); 136 if (len <= 2 137 ? (char) scan[len-1] == str[len-1] 138 : memcmp(scan+1, str+1, len-1) == 0) { 139 return (int)(scan - bytes); 140 } 141 } 142 return -1; 143 } 144 145 146 char* Symbol::as_C_string(char* buf, int size) const { 147 if (size > 0) { 148 int len = MIN2(size - 1, utf8_length()); 149 for (int i = 0; i < len; i++) { 150 buf[i] = char_at(i); 151 } 152 buf[len] = '\0'; 153 } 154 return buf; 155 } 156 157 char* Symbol::as_C_string() const { 158 int len = utf8_length(); 159 char* str = NEW_RESOURCE_ARRAY(char, len + 1); 160 return as_C_string(str, len + 1); 161 } 162 163 void Symbol::print_utf8_on(outputStream* st) const { 164 st->print("%s", as_C_string()); 165 } 166 167 void Symbol::print_symbol_on(outputStream* st) const { 168 char *s; 169 st = st ? st : tty; 170 { 171 // ResourceMark may not affect st->print(). If st is a string 172 // stream it could resize, using the same resource arena. 173 ResourceMark rm; 174 s = as_quoted_ascii(); 175 s = os::strdup(s); 176 } 177 if (s == NULL) { 178 st->print("(null)"); 179 } else { 180 st->print("%s", s); 181 os::free(s); 182 } 183 } 184 185 char* Symbol::as_quoted_ascii() const { 186 const char *ptr = (const char *)&_body[0]; 187 int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length()); 188 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1); 189 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1); 190 return result; 191 } 192 193 jchar* Symbol::as_unicode(int& length) const { 194 Symbol* this_ptr = (Symbol*)this; 195 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length()); 196 jchar* result = NEW_RESOURCE_ARRAY(jchar, length); 197 if (length > 0) { 198 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length); 199 } 200 return result; 201 } 202 203 const char* Symbol::as_klass_external_name(char* buf, int size) const { 204 if (size > 0) { 205 char* str = as_C_string(buf, size); 206 int length = (int)strlen(str); 207 // Turn all '/'s into '.'s (also for array klasses) 208 for (int index = 0; index < length; index++) { 209 if (str[index] == JVM_SIGNATURE_SLASH) { 210 str[index] = JVM_SIGNATURE_DOT; 211 } 212 } 213 return str; 214 } else { 215 return buf; 216 } 217 } 218 219 const char* Symbol::as_klass_external_name() const { 220 char* str = as_C_string(); 221 int length = (int)strlen(str); 222 // Turn all '/'s into '.'s (also for array klasses) 223 for (int index = 0; index < length; index++) { 224 if (str[index] == JVM_SIGNATURE_SLASH) { 225 str[index] = JVM_SIGNATURE_DOT; 226 } 227 } 228 return str; 229 } 230 231 static void print_class(outputStream *os, const SignatureStream& ss) { 232 int sb = ss.raw_symbol_begin(), se = ss.raw_symbol_end(); 233 for (int i = sb; i < se; ++i) { 234 int ch = ss.raw_char_at(i); 235 if (ch == JVM_SIGNATURE_SLASH) { 236 os->put(JVM_SIGNATURE_DOT); 237 } else { 238 os->put(ch); 239 } 240 } 241 } 242 243 static void print_array(outputStream *os, SignatureStream& ss) { 244 int dimensions = ss.skip_array_prefix(); 245 assert(dimensions > 0, ""); 246 if (ss.is_reference()) { 247 print_class(os, ss); 248 } else { 249 os->print("%s", type2name(ss.type())); 250 } 251 for (int i = 0; i < dimensions; ++i) { 252 os->print("[]"); 253 } 254 } 255 256 void Symbol::print_as_signature_external_return_type(outputStream *os) { 257 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 258 if (ss.at_return_type()) { 259 if (ss.is_array()) { 260 print_array(os, ss); 261 } else if (ss.is_reference()) { 262 print_class(os, ss); 263 } else { 264 os->print("%s", type2name(ss.type())); 265 } 266 } 267 } 268 } 269 270 void Symbol::print_as_signature_external_parameters(outputStream *os) { 271 bool first = true; 272 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 273 if (ss.at_return_type()) break; 274 if (!first) { os->print(", "); } 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 first = false; 283 } 284 } 285 286 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero 287 // a thread could be concurrently removing the Symbol. This is used during SymbolTable 288 // lookup to avoid reviving a dead Symbol. 289 bool Symbol::try_increment_refcount() { 290 uint32_t found = _hash_and_refcount; 291 while (true) { 292 uint32_t old_value = found; 293 int refc = extract_refcount(old_value); 294 if (refc == PERM_REFCOUNT) { 295 return true; // sticky max or created permanent 296 } else if (refc == 0) { 297 return false; // dead, can't revive. 298 } else { 299 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value + 1); 300 if (found == old_value) { 301 return true; // successfully updated. 302 } 303 // refcount changed, try again. 304 } 305 } 306 } 307 308 // The increment_refcount() is called when not doing lookup. It is assumed that you 309 // have a symbol with a non-zero refcount and it can't become zero while referenced by 310 // this caller. 311 void Symbol::increment_refcount() { 312 if (!try_increment_refcount()) { 313 #ifdef ASSERT 314 print(); 315 fatal("refcount has gone to zero"); 316 #endif 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 #ifdef ASSERT 337 print(); 338 fatal("refcount underflow"); 339 #endif 340 return; 341 } else { 342 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value - 1); 343 if (found == old_value) { 344 return; // successfully updated. 345 } 346 // refcount changed, try again. 347 } 348 } 349 } 350 351 void Symbol::make_permanent() { 352 uint32_t found = _hash_and_refcount; 353 while (true) { 354 uint32_t old_value = found; 355 int refc = extract_refcount(old_value); 356 if (refc == PERM_REFCOUNT) { 357 return; // refcount is permanent, permanent is sticky 358 } else if (refc == 0) { 359 #ifdef ASSERT 360 print(); 361 fatal("refcount underflow"); 362 #endif 363 return; 364 } else { 365 int hash = extract_hash(old_value); 366 found = Atomic::cmpxchg(&_hash_and_refcount, old_value, pack_hash_and_refcount(hash, PERM_REFCOUNT)); 367 if (found == old_value) { 368 return; // successfully updated. 369 } 370 // refcount changed, try again. 371 } 372 } 373 } 374 375 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) { 376 if (log_is_enabled(Trace, cds)) { 377 LogStream trace_stream(Log(cds)::trace()); 378 trace_stream.print("Iter(Symbol): %p ", this); 379 print_value_on(&trace_stream); 380 trace_stream.cr(); 381 } 382 } 383 384 void Symbol::print_on(outputStream* st) const { 385 st->print("Symbol: '"); 386 print_symbol_on(st); 387 st->print("'"); 388 st->print(" count %d", refcount()); 389 } 390 391 void Symbol::print() const { print_on(tty); } 392 393 // The print_value functions are present in all builds, to support the 394 // disassembler and error reporting. 395 void Symbol::print_value_on(outputStream* st) const { 396 st->print("'"); 397 for (int i = 0; i < utf8_length(); i++) { 398 st->print("%c", char_at(i)); 399 } 400 st->print("'"); 401 } 402 403 void Symbol::print_value() const { print_value_on(tty); } 404 405 bool Symbol::is_valid(Symbol* s) { 406 if (!is_aligned(s, sizeof(MetaWord))) return false; 407 if ((size_t)s < os::min_page_size()) return false; 408 409 if (!os::is_readable_range(s, s + 1)) return false; 410 411 // Symbols are not allocated in Java heap. 412 if (Universe::heap()->is_in(s)) return false; 413 414 int len = s->utf8_length(); 415 if (len < 0) return false; 416 417 jbyte* bytes = (jbyte*) s->bytes(); 418 return os::is_readable_range(bytes, bytes + len); 419 } 420 421 // SymbolTable prints this in its statistics 422 NOT_PRODUCT(size_t Symbol::_total_count = 0;) 423 424 #ifndef PRODUCT 425 bool Symbol::is_valid_id(vmSymbolID vm_symbol_id) { 426 return vmSymbols::is_valid_id(vm_symbol_id); 427 } 428 #endif --- EOF ---