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 "oops/symbol.hpp" 35 #include "runtime/atomic.hpp" 36 #include "runtime/os.hpp" 37 38 uint32_t Symbol::pack_length_and_refcount(int length, int refcount) { 39 STATIC_ASSERT(max_symbol_length == ((1 << 16) - 1)); 40 STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1)); 41 assert(length >= 0, "negative length"); 42 assert(length <= max_symbol_length, "too long symbol"); 43 assert(refcount >= 0, "negative refcount"); 44 assert(refcount <= PERM_REFCOUNT, "invalid refcount"); 45 uint32_t hi = length; 46 uint32_t lo = refcount; 47 return (hi << 16) | lo; 48 } 49 50 Symbol::Symbol(const u1* name, int length, int refcount) { 51 _length_and_refcount = pack_length_and_refcount(length, refcount); 52 _identity_hash = (short)os::random(); 53 for (int i = 0; i < length; i++) { 54 byte_at_put(i, name[i]); 55 } 56 } 57 58 void* Symbol::operator new(size_t sz, int len, TRAPS) throw() { 59 int alloc_size = size(len)*wordSize; 60 address res = (address) AllocateHeap(alloc_size, mtSymbol); 61 return res; 62 } 63 64 void* Symbol::operator new(size_t sz, int len, Arena* arena, TRAPS) throw() { 65 int alloc_size = size(len)*wordSize; 66 address res = (address)arena->Amalloc_4(alloc_size); 67 return res; 68 } 69 70 void Symbol::operator delete(void *p) { 71 assert(((Symbol*)p)->refcount() == 0, "should not call this"); 72 FreeHeap(p); 73 } 74 75 // ------------------------------------------------------------------ 76 // Symbol::starts_with 77 // 78 // Tests if the symbol starts with the specified prefix of the given 79 // length. 80 bool Symbol::starts_with(const char* prefix, int len) const { 81 if (len > utf8_length()) return false; 82 while (len-- > 0) { 83 if (prefix[len] != char_at(len)) 84 return false; 85 } 86 assert(len == -1, "we should be at the beginning"); 87 return true; 88 } 89 90 bool Symbol::is_Q_signature() const { 91 return utf8_length() > 2 && char_at(0) == 'Q' && char_at(utf8_length() - 1) == ';'; 92 } 93 94 Symbol* Symbol::fundamental_name(TRAPS) { 95 if ((char_at(0) == 'Q' || char_at(0) == 'L') && char_at(utf8_length() - 1) == ';') { 96 return SymbolTable::lookup(this, 1, utf8_length() - 1, CHECK_NULL); 97 } else { 98 // reference count is incremented to be consistent with the behavior with 99 // the SymbolTable::lookup() call above 100 this->increment_refcount(); 101 return this; 102 } 103 } 104 105 bool Symbol::is_same_fundamental_type(Symbol* s) const { 106 if (this == s) return true; 107 if (utf8_length() < 3) return false; 108 int offset1, offset2, len; 109 if (char_at(utf8_length() - 1) == ';') { 110 if (char_at(0) != 'Q' && char_at(0) != 'L') return false; 111 offset1 = 1; 112 len = utf8_length() - 2; 113 } else { 114 offset1 = 0; 115 len = utf8_length(); 116 } 117 if (s->char_at(s->utf8_length() - 1) == ';') { 118 if (s->char_at(0) != 'Q' && s->char_at(0) != 'L') return false; 119 offset2 = 1; 120 } else { 121 offset2 = 0; 122 } 123 if ((offset2 + len) > s->utf8_length()) return false; 124 if ((utf8_length() - offset1 * 2) != (s->utf8_length() - offset2 * 2)) 125 return false; 126 int l = len; 127 while (l-- > 0) { 128 if (char_at(offset1 + l) != s->char_at(offset2 + l)) 129 return false; 130 } 131 return true; 132 } 133 134 // ------------------------------------------------------------------ 135 // Symbol::index_of 136 // 137 // Finds if the given string is a substring of this symbol's utf8 bytes. 138 // Return -1 on failure. Otherwise return the first index where str occurs. 139 int Symbol::index_of_at(int i, const char* str, int len) const { 140 assert(i >= 0 && i <= utf8_length(), "oob"); 141 if (len <= 0) return 0; 142 char first_char = str[0]; 143 address bytes = (address) ((Symbol*)this)->base(); 144 address limit = bytes + utf8_length() - len; // inclusive limit 145 address scan = bytes + i; 146 if (scan > limit) 147 return -1; 148 for (; scan <= limit; scan++) { 149 scan = (address) memchr(scan, first_char, (limit + 1 - scan)); 150 if (scan == NULL) 151 return -1; // not found 152 assert(scan >= bytes+i && scan <= limit, "scan oob"); 153 if (memcmp(scan, str, len) == 0) 154 return (int)(scan - bytes); 155 } 156 return -1; 157 } 158 159 160 char* Symbol::as_C_string(char* buf, int size) const { 161 if (size > 0) { 162 int len = MIN2(size - 1, utf8_length()); 163 for (int i = 0; i < len; i++) { 164 buf[i] = char_at(i); 165 } 166 buf[len] = '\0'; 167 } 168 return buf; 169 } 170 171 char* Symbol::as_C_string() const { 172 int len = utf8_length(); 173 char* str = NEW_RESOURCE_ARRAY(char, len + 1); 174 return as_C_string(str, len + 1); 175 } 176 177 void Symbol::print_utf8_on(outputStream* st) const { 178 st->print("%s", as_C_string()); 179 } 180 181 void Symbol::print_symbol_on(outputStream* st) const { 182 char *s; 183 st = st ? st : tty; 184 { 185 // ResourceMark may not affect st->print(). If st is a string 186 // stream it could resize, using the same resource arena. 187 ResourceMark rm; 188 s = as_quoted_ascii(); 189 s = os::strdup(s); 190 } 191 if (s == NULL) { 192 st->print("(null)"); 193 } else { 194 st->print("%s", s); 195 os::free(s); 196 } 197 } 198 199 char* Symbol::as_quoted_ascii() const { 200 const char *ptr = (const char *)&_body[0]; 201 int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length()); 202 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1); 203 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1); 204 return result; 205 } 206 207 jchar* Symbol::as_unicode(int& length) const { 208 Symbol* this_ptr = (Symbol*)this; 209 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length()); 210 jchar* result = NEW_RESOURCE_ARRAY(jchar, length); 211 if (length > 0) { 212 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length); 213 } 214 return result; 215 } 216 217 const char* Symbol::as_klass_external_name(char* buf, int size) const { 218 if (size > 0) { 219 char* str = as_C_string(buf, size); 220 int length = (int)strlen(str); 221 // Turn all '/'s into '.'s (also for array klasses) 222 for (int index = 0; index < length; index++) { 223 if (str[index] == '/') { 224 str[index] = '.'; 225 } 226 } 227 return str; 228 } else { 229 return buf; 230 } 231 } 232 233 const char* Symbol::as_klass_external_name() const { 234 char* str = as_C_string(); 235 int length = (int)strlen(str); 236 // Turn all '/'s into '.'s (also for array klasses) 237 for (int index = 0; index < length; index++) { 238 if (str[index] == '/') { 239 str[index] = '.'; 240 } 241 } 242 return str; 243 } 244 245 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero 246 // a thread could be concurrently removing the Symbol. This is used during SymbolTable 247 // lookup to avoid reviving a dead Symbol. 248 bool Symbol::try_increment_refcount() { 249 uint32_t found = _length_and_refcount; 250 while (true) { 251 uint32_t old_value = found; 252 int refc = extract_refcount(old_value); 253 if (refc == PERM_REFCOUNT) { 254 return true; // sticky max or created permanent 255 } else if (refc == 0) { 256 return false; // dead, can't revive. 257 } else { 258 found = Atomic::cmpxchg(old_value + 1, &_length_and_refcount, old_value); 259 if (found == old_value) { 260 return true; // successfully updated. 261 } 262 // refcount changed, try again. 263 } 264 } 265 } 266 267 // The increment_refcount() is called when not doing lookup. It is assumed that you 268 // have a symbol with a non-zero refcount and it can't become zero while referenced by 269 // this caller. 270 void Symbol::increment_refcount() { 271 if (!try_increment_refcount()) { 272 #ifdef ASSERT 273 print(); 274 fatal("refcount has gone to zero"); 275 #endif 276 } 277 #ifndef PRODUCT 278 if (refcount() != PERM_REFCOUNT) { // not a permanent symbol 279 NOT_PRODUCT(Atomic::inc(&_total_count);) 280 } 281 #endif 282 } 283 284 // Decrement refcount potentially while racing increment, so we need 285 // to check the value after attempting to decrement so that if another 286 // thread increments to PERM_REFCOUNT the value is not decremented. 287 void Symbol::decrement_refcount() { 288 uint32_t found = _length_and_refcount; 289 while (true) { 290 uint32_t old_value = found; 291 int refc = extract_refcount(old_value); 292 if (refc == PERM_REFCOUNT) { 293 return; // refcount is permanent, permanent is sticky 294 } else if (refc == 0) { 295 #ifdef ASSERT 296 print(); 297 fatal("refcount underflow"); 298 #endif 299 return; 300 } else { 301 found = Atomic::cmpxchg(old_value - 1, &_length_and_refcount, old_value); 302 if (found == old_value) { 303 return; // successfully updated. 304 } 305 // refcount changed, try again. 306 } 307 } 308 } 309 310 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) { 311 if (log_is_enabled(Trace, cds)) { 312 LogStream trace_stream(Log(cds)::trace()); 313 trace_stream.print("Iter(Symbol): %p ", this); 314 print_value_on(&trace_stream); 315 trace_stream.cr(); 316 } 317 } 318 319 void Symbol::print_on(outputStream* st) const { 320 st->print("Symbol: '"); 321 print_symbol_on(st); 322 st->print("'"); 323 st->print(" count %d", refcount()); 324 } 325 326 // The print_value functions are present in all builds, to support the 327 // disassembler and error reporting. 328 void Symbol::print_value_on(outputStream* st) const { 329 st->print("'"); 330 for (int i = 0; i < utf8_length(); i++) { 331 st->print("%c", char_at(i)); 332 } 333 st->print("'"); 334 } 335 336 bool Symbol::is_valid(Symbol* s) { 337 if (!is_aligned(s, sizeof(MetaWord))) return false; 338 if ((size_t)s < os::min_page_size()) return false; 339 340 if (!os::is_readable_range(s, s + 1)) return false; 341 342 // Symbols are not allocated in Java heap. 343 if (Universe::heap()->is_in_reserved(s)) return false; 344 345 int len = s->utf8_length(); 346 if (len < 0) return false; 347 348 jbyte* bytes = (jbyte*) s->bytes(); 349 return os::is_readable_range(bytes, bytes + len); 350 } 351 352 void Symbol::print_Qvalue_on(outputStream* st) const { 353 if (this == NULL) { 354 st->print("NULL"); 355 } else { 356 st->print("'Q"); 357 for (int i = 0; i < utf8_length(); i++) { 358 st->print("%c", char_at(i)); 359 } 360 st->print(";'"); 361 } 362 } 363 364 // SymbolTable prints this in its statistics 365 NOT_PRODUCT(size_t Symbol::_total_count = 0;)