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8141491: Unaligned memory access in Bits.c

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Introduce alignment-safe Copy::conjoint_swap and j.i.m.Unsafe.copySwapMemory

Reviewed-by: jrose, dholmes, psandoz
This commit is contained in:
Mikael Vidstedt 2016-02-10 15:20:38 -08:00
parent 3fc0fa269a
commit 4e53f48812
4 changed files with 230 additions and 4 deletions
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33
hotspot/src/share/vm/prims/unsafe.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -660,6 +660,36 @@ UNSAFE_ENTRY(void, Unsafe_CopyMemory(JNIEnv *env, jobject unsafe, jobject srcObj
Copy::conjoint_memory_atomic(src, dst, sz);
UNSAFE_END
// This function is a leaf since if the source and destination are both in native memory
// the copy may potentially be very large, and we don't want to disable GC if we can avoid it.
// If either source or destination (or both) are on the heap, the function will enter VM using
// JVM_ENTRY_FROM_LEAF
JVM_LEAF(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
UnsafeWrapper("Unsafe_CopySwapMemory0");
size_t sz = (size_t)size;
size_t esz = (size_t)elemSize;
if (srcObj == NULL && dstObj == NULL) {
// Both src & dst are in native memory
address src = (address)srcOffset;
address dst = (address)dstOffset;
Copy::conjoint_swap(src, dst, sz, esz);
} else {
// At least one of src/dst are on heap, transition to VM to access raw pointers
JVM_ENTRY_FROM_LEAF(env, void, Unsafe_CopySwapMemory0) {
oop srcp = JNIHandles::resolve(srcObj);
oop dstp = JNIHandles::resolve(dstObj);
address src = (address)index_oop_from_field_offset_long(srcp, srcOffset);
address dst = (address)index_oop_from_field_offset_long(dstp, dstOffset);
Copy::conjoint_swap(src, dst, sz, esz);
} JVM_END
}
} JVM_END
////// Random queries
@ -1363,6 +1393,7 @@ static JNINativeMethod jdk_internal_misc_Unsafe_methods[] = {
{CC "getLoadAverage", CC "([DI)I", FN_PTR(Unsafe_Loadavg)},
{CC "copyMemory", CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory)},
{CC "copySwapMemory0", CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
{CC "setMemory", CC "(" OBJ "JJB)V", FN_PTR(Unsafe_SetMemory)},
{CC "defineAnonymousClass", CC "(" DAC_Args ")" CLS, FN_PTR(Unsafe_DefineAnonymousClass)},