1 /* 2 * Copyright (c) 1997, 2019, 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 "classfile/altHashing.hpp" 28 #include "classfile/classLoaderData.hpp" 29 #include "gc/shared/collectedHeap.hpp" 30 #include "logging/log.hpp" 31 #include "logging/logStream.hpp" 32 #include "memory/allocation.inline.hpp" 33 #include "memory/resourceArea.hpp" 34 #include "memory/universe.hpp" 35 #include "oops/symbol.hpp" 36 #include "runtime/atomic.hpp" 37 #include "runtime/os.hpp" 38 #include "utilities/utf8.hpp" 39 40 uint32_t Symbol::pack_length_and_refcount(int length, int refcount) { 41 STATIC_ASSERT(max_symbol_length == ((1 << 16) - 1)); 42 STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1)); 43 assert(length >= 0, "negative length"); 44 assert(length <= max_symbol_length, "too long symbol"); 45 assert(refcount >= 0, "negative refcount"); 46 assert(refcount <= PERM_REFCOUNT, "invalid refcount"); 47 uint32_t hi = length; 48 uint32_t lo = refcount; 49 return (hi << 16) | lo; 50 } 51 52 Symbol::Symbol(const u1* name, int length, int refcount) { 53 _length_and_refcount = pack_length_and_refcount(length, refcount); 54 _identity_hash = (short)os::random(); 55 for (int i = 0; i < length; i++) { 56 byte_at_put(i, name[i]); 57 } 58 } 59 60 void* Symbol::operator new(size_t sz, int len) throw() { 61 int alloc_size = size(len)*wordSize; 62 address res = (address) AllocateHeap(alloc_size, mtSymbol); 63 return res; 64 } 65 66 void* Symbol::operator new(size_t sz, int len, Arena* arena) throw() { 67 int alloc_size = size(len)*wordSize; 68 address res = (address)arena->Amalloc_4(alloc_size); 69 return res; 70 } 71 72 void Symbol::operator delete(void *p) { 73 assert(((Symbol*)p)->refcount() == 0, "should not call this"); 74 FreeHeap(p); 75 } 76 77 void Symbol::set_permanent() { 78 // This is called at a safepoint during dumping of a dynamic CDS archive. 79 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); 80 _length_and_refcount = pack_length_and_refcount(length(), PERM_REFCOUNT); 81 } 82 83 84 // ------------------------------------------------------------------ 85 // Symbol::starts_with 86 // 87 // Tests if the symbol starts with the specified prefix of the given 88 // length. 89 bool Symbol::starts_with(const char* prefix, int len) const { 90 if (len > utf8_length()) return false; 91 while (len-- > 0) { 92 if (prefix[len] != char_at(len)) 93 return false; 94 } 95 assert(len == -1, "we should be at the beginning"); 96 return true; 97 } 98 99 100 // ------------------------------------------------------------------ 101 // Symbol::index_of 102 // 103 // Finds if the given string is a substring of this symbol's utf8 bytes. 104 // Return -1 on failure. Otherwise return the first index where str occurs. 105 int Symbol::index_of_at(int i, const char* str, int len) const { 106 assert(i >= 0 && i <= utf8_length(), "oob"); 107 if (len <= 0) return 0; 108 char first_char = str[0]; 109 address bytes = (address) ((Symbol*)this)->base(); 110 address limit = bytes + utf8_length() - len; // inclusive limit 111 address scan = bytes + i; 112 if (scan > limit) 113 return -1; 114 for (; scan <= limit; scan++) { 115 scan = (address) memchr(scan, first_char, (limit + 1 - scan)); 116 if (scan == NULL) 117 return -1; // not found 118 assert(scan >= bytes+i && scan <= limit, "scan oob"); 119 if (memcmp(scan, str, len) == 0) 120 return (int)(scan - bytes); 121 } 122 return -1; 123 } 124 125 126 char* Symbol::as_C_string(char* buf, int size) const { 127 if (size > 0) { 128 int len = MIN2(size - 1, utf8_length()); 129 for (int i = 0; i < len; i++) { 130 buf[i] = char_at(i); 131 } 132 buf[len] = '\0'; 133 } 134 return buf; 135 } 136 137 char* Symbol::as_C_string() const { 138 int len = utf8_length(); 139 char* str = NEW_RESOURCE_ARRAY(char, len + 1); 140 return as_C_string(str, len + 1); 141 } 142 143 void Symbol::print_utf8_on(outputStream* st) const { 144 st->print("%s", as_C_string()); 145 } 146 147 void Symbol::print_symbol_on(outputStream* st) const { 148 char *s; 149 st = st ? st : tty; 150 { 151 // ResourceMark may not affect st->print(). If st is a string 152 // stream it could resize, using the same resource arena. 153 ResourceMark rm; 154 s = as_quoted_ascii(); 155 s = os::strdup(s); 156 } 157 if (s == NULL) { 158 st->print("(null)"); 159 } else { 160 st->print("%s", s); 161 os::free(s); 162 } 163 } 164 165 char* Symbol::as_quoted_ascii() const { 166 const char *ptr = (const char *)&_body[0]; 167 int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length()); 168 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1); 169 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1); 170 return result; 171 } 172 173 jchar* Symbol::as_unicode(int& length) const { 174 Symbol* this_ptr = (Symbol*)this; 175 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length()); 176 jchar* result = NEW_RESOURCE_ARRAY(jchar, length); 177 if (length > 0) { 178 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length); 179 } 180 return result; 181 } 182 183 const char* Symbol::as_klass_external_name(char* buf, int size) const { 184 if (size > 0) { 185 char* str = as_C_string(buf, size); 186 int length = (int)strlen(str); 187 // Turn all '/'s into '.'s (also for array klasses) 188 for (int index = 0; index < length; index++) { 189 if (str[index] == '/') { 190 str[index] = '.'; 191 } 192 } 193 return str; 194 } else { 195 return buf; 196 } 197 } 198 199 const char* Symbol::as_klass_external_name() const { 200 char* str = as_C_string(); 201 int length = (int)strlen(str); 202 // Turn all '/'s into '.'s (also for array klasses) 203 for (int index = 0; index < length; index++) { 204 if (str[index] == JVM_SIGNATURE_SLASH) { 205 str[index] = JVM_SIGNATURE_DOT; 206 } 207 } 208 return str; 209 } 210 211 static void print_class(outputStream *os, char *class_str, int len) { 212 for (int i = 0; i < len; ++i) { 213 if (class_str[i] == JVM_SIGNATURE_SLASH) { 214 os->put(JVM_SIGNATURE_DOT); 215 } else { 216 os->put(class_str[i]); 217 } 218 } 219 } 220 221 static void print_array(outputStream *os, char *array_str, int len) { 222 int dimensions = 0; 223 for (int i = 0; i < len; ++i) { 224 if (array_str[i] == JVM_SIGNATURE_ARRAY) { 225 dimensions++; 226 } else if (array_str[i] == JVM_SIGNATURE_CLASS) { 227 // Expected format: L<type name>;. Skip 'L' and ';' delimiting the type name. 228 print_class(os, array_str+i+1, len-i-2); 229 break; 230 } else { 231 os->print("%s", type2name(char2type(array_str[i]))); 232 } 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, (char*)ss.raw_bytes(), (int)ss.raw_length()); 244 } else if (ss.is_object()) { 245 // Expected format: L<type name>;. Skip 'L' and ';' delimiting the class name. 246 print_class(os, (char*)ss.raw_bytes()+1, (int)ss.raw_length()-2); 247 } else { 248 os->print("%s", type2name(ss.type())); 249 } 250 } 251 } 252 } 253 254 void Symbol::print_as_signature_external_parameters(outputStream *os) { 255 bool first = true; 256 for (SignatureStream ss(this); !ss.is_done(); ss.next()) { 257 if (ss.at_return_type()) break; 258 if (!first) { os->print(", "); } 259 if (ss.is_array()) { 260 print_array(os, (char*)ss.raw_bytes(), (int)ss.raw_length()); 261 } else if (ss.is_object()) { 262 // Skip 'L' and ';'. 263 print_class(os, (char*)ss.raw_bytes()+1, (int)ss.raw_length()-2); 264 } else { 265 os->print("%s", type2name(ss.type())); 266 } 267 first = false; 268 } 269 } 270 271 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero 272 // a thread could be concurrently removing the Symbol. This is used during SymbolTable 273 // lookup to avoid reviving a dead Symbol. 274 bool Symbol::try_increment_refcount() { 275 uint32_t found = _length_and_refcount; 276 while (true) { 277 uint32_t old_value = found; 278 int refc = extract_refcount(old_value); 279 if (refc == PERM_REFCOUNT) { 280 return true; // sticky max or created permanent 281 } else if (refc == 0) { 282 return false; // dead, can't revive. 283 } else { 284 found = Atomic::cmpxchg(old_value + 1, &_length_and_refcount, old_value); 285 if (found == old_value) { 286 return true; // successfully updated. 287 } 288 // refcount changed, try again. 289 } 290 } 291 } 292 293 // The increment_refcount() is called when not doing lookup. It is assumed that you 294 // have a symbol with a non-zero refcount and it can't become zero while referenced by 295 // this caller. 296 void Symbol::increment_refcount() { 297 if (!try_increment_refcount()) { 298 #ifdef ASSERT 299 print(); 300 fatal("refcount has gone to zero"); 301 #endif 302 } 303 #ifndef PRODUCT 304 if (refcount() != PERM_REFCOUNT) { // not a permanent symbol 305 NOT_PRODUCT(Atomic::inc(&_total_count);) 306 } 307 #endif 308 } 309 310 // Decrement refcount potentially while racing increment, so we need 311 // to check the value after attempting to decrement so that if another 312 // thread increments to PERM_REFCOUNT the value is not decremented. 313 void Symbol::decrement_refcount() { 314 uint32_t found = _length_and_refcount; 315 while (true) { 316 uint32_t old_value = found; 317 int refc = extract_refcount(old_value); 318 if (refc == PERM_REFCOUNT) { 319 return; // refcount is permanent, permanent is sticky 320 } else if (refc == 0) { 321 #ifdef ASSERT 322 print(); 323 fatal("refcount underflow"); 324 #endif 325 return; 326 } else { 327 found = Atomic::cmpxchg(old_value - 1, &_length_and_refcount, old_value); 328 if (found == old_value) { 329 return; // successfully updated. 330 } 331 // refcount changed, try again. 332 } 333 } 334 } 335 336 void Symbol::make_permanent() { 337 uint32_t found = _length_and_refcount; 338 while (true) { 339 uint32_t old_value = found; 340 int refc = extract_refcount(old_value); 341 if (refc == PERM_REFCOUNT) { 342 return; // refcount is permanent, permanent is sticky 343 } else if (refc == 0) { 344 #ifdef ASSERT 345 print(); 346 fatal("refcount underflow"); 347 #endif 348 return; 349 } else { 350 int len = extract_length(old_value); 351 found = Atomic::cmpxchg(pack_length_and_refcount(len, PERM_REFCOUNT), &_length_and_refcount, old_value); 352 if (found == old_value) { 353 return; // successfully updated. 354 } 355 // refcount changed, try again. 356 } 357 } 358 } 359 360 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) { 361 if (log_is_enabled(Trace, cds)) { 362 LogStream trace_stream(Log(cds)::trace()); 363 trace_stream.print("Iter(Symbol): %p ", this); 364 print_value_on(&trace_stream); 365 trace_stream.cr(); 366 } 367 } 368 369 void Symbol::print_on(outputStream* st) const { 370 st->print("Symbol: '"); 371 print_symbol_on(st); 372 st->print("'"); 373 st->print(" count %d", refcount()); 374 } 375 376 void Symbol::print() const { print_on(tty); } 377 378 // The print_value functions are present in all builds, to support the 379 // disassembler and error reporting. 380 void Symbol::print_value_on(outputStream* st) const { 381 st->print("'"); 382 for (int i = 0; i < utf8_length(); i++) { 383 st->print("%c", char_at(i)); 384 } 385 st->print("'"); 386 } 387 388 void Symbol::print_value() const { print_value_on(tty); } 389 390 bool Symbol::is_valid(Symbol* s) { 391 if (!is_aligned(s, sizeof(MetaWord))) return false; 392 if ((size_t)s < os::min_page_size()) return false; 393 394 if (!os::is_readable_range(s, s + 1)) return false; 395 396 // Symbols are not allocated in Java heap. 397 if (Universe::heap()->is_in(s)) return false; 398 399 int len = s->utf8_length(); 400 if (len < 0) return false; 401 402 jbyte* bytes = (jbyte*) s->bytes(); 403 return os::is_readable_range(bytes, bytes + len); 404 } 405 406 // SymbolTable prints this in its statistics 407 NOT_PRODUCT(size_t Symbol::_total_count = 0;)