1 /* 2 * Copyright (c) 2018, 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 "gc/shared/barrierSetAssembler.hpp" 26 #include "memory/universe.hpp" 27 #include "utilities/globalDefinitions.hpp" 28 29 bool BarrierSetAssembler::needs_explicit_null_check(intptr_t offset) const { 30 // Exception handler checks the nmethod's implicit null checks table 31 // only when this method returns false. 32 #ifdef _LP64 33 if (UseCompressedOops && Universe::narrow_oop_base() != NULL) { 34 assert (Universe::heap() != NULL, "java heap should be initialized"); 35 // The first page after heap_base is unmapped and 36 // the 'offset' is equal to [heap_base + offset] for 37 // narrow oop implicit null checks. 38 uintptr_t base = (uintptr_t)Universe::narrow_oop_base(); 39 if ((uintptr_t)offset >= base) { 40 // Normalize offset for the next check. 41 offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1)); 42 } 43 } 44 #endif 45 return offset < 0 || os::vm_page_size() <= offset; 46 }