8161720: Better byte behavior for off-heap data
Summary: Normalize boolean values read with Unsafe.
Reviewed-by: aph, simonis, jrose, psandoz
/*
* 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "classfile/classFileStream.hpp"
#include "classfile/vmSymbols.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "oops/objArrayOop.inline.hpp"
#include "oops/oop.inline.hpp"
#include "prims/jni.h"
#include "prims/jvm.h"
#include "prims/unsafe.hpp"
#include "runtime/atomic.hpp"
#include "runtime/globals.hpp"
#include "runtime/interfaceSupport.hpp"
#include "runtime/orderAccess.inline.hpp"
#include "runtime/reflection.hpp"
#include "runtime/vm_version.hpp"
#include "services/threadService.hpp"
#include "trace/tracing.hpp"
#include "utilities/copy.hpp"
#include "utilities/dtrace.hpp"
#include "utilities/macros.hpp"
#if INCLUDE_ALL_GCS
#include "gc/g1/g1SATBCardTableModRefBS.hpp"
#endif // INCLUDE_ALL_GCS
/**
* Implementation of the jdk.internal.misc.Unsafe class
*/
#define MAX_OBJECT_SIZE \
( arrayOopDesc::header_size(T_DOUBLE) * HeapWordSize \
+ ((julong)max_jint * sizeof(double)) )
#define UNSAFE_ENTRY(result_type, header) \
JVM_ENTRY(static result_type, header)
#define UNSAFE_LEAF(result_type, header) \
JVM_LEAF(static result_type, header)
#define UNSAFE_END JVM_END
static inline void* addr_from_java(jlong addr) {
// This assert fails in a variety of ways on 32-bit systems.
// It is impossible to predict whether native code that converts
// pointers to longs will sign-extend or zero-extend the addresses.
//assert(addr == (uintptr_t)addr, "must not be odd high bits");
return (void*)(uintptr_t)addr;
}
static inline jlong addr_to_java(void* p) {
assert(p == (void*)(uintptr_t)p, "must not be odd high bits");
return (uintptr_t)p;
}
// Note: The VM's obj_field and related accessors use byte-scaled
// ("unscaled") offsets, just as the unsafe methods do.
// However, the method Unsafe.fieldOffset explicitly declines to
// guarantee this. The field offset values manipulated by the Java user
// through the Unsafe API are opaque cookies that just happen to be byte
// offsets. We represent this state of affairs by passing the cookies
// through conversion functions when going between the VM and the Unsafe API.
// The conversion functions just happen to be no-ops at present.
static inline jlong field_offset_to_byte_offset(jlong field_offset) {
return field_offset;
}
static inline jlong field_offset_from_byte_offset(jlong byte_offset) {
return byte_offset;
}
static inline void* index_oop_from_field_offset_long(oop p, jlong field_offset) {
jlong byte_offset = field_offset_to_byte_offset(field_offset);
#ifdef ASSERT
if (p != NULL) {
assert(byte_offset >= 0 && byte_offset <= (jlong)MAX_OBJECT_SIZE, "sane offset");
if (byte_offset == (jint)byte_offset) {
void* ptr_plus_disp = (address)p + byte_offset;
assert((void*)p->obj_field_addr<oop>((jint)byte_offset) == ptr_plus_disp,
"raw [ptr+disp] must be consistent with oop::field_base");
}
jlong p_size = HeapWordSize * (jlong)(p->size());
assert(byte_offset < p_size, "Unsafe access: offset " INT64_FORMAT " > object's size " INT64_FORMAT, byte_offset, p_size);
}
#endif
if (sizeof(char*) == sizeof(jint)) { // (this constant folds!)
return (address)p + (jint) byte_offset;
} else {
return (address)p + byte_offset;
}
}
// Externally callable versions:
// (Use these in compiler intrinsics which emulate unsafe primitives.)
jlong Unsafe_field_offset_to_byte_offset(jlong field_offset) {
return field_offset;
}
jlong Unsafe_field_offset_from_byte_offset(jlong byte_offset) {
return byte_offset;
}
///// Data read/writes on the Java heap and in native (off-heap) memory
/**
* Helper class for accessing memory.
*
* Normalizes values and wraps accesses in
* JavaThread::doing_unsafe_access() if needed.
*/
class MemoryAccess : StackObj {
JavaThread* _thread;
jobject _obj;
jlong _offset;
// Resolves and returns the address of the memory access
void* addr() {
return index_oop_from_field_offset_long(JNIHandles::resolve(_obj), _offset);
}
template <typename T>
T normalize_for_write(T x) {
return x;
}
jboolean normalize_for_write(jboolean x) {
return x & 1;
}
template <typename T>
T normalize_for_read(T x) {
return x;
}
jboolean normalize_for_read(jboolean x) {
return x != 0;
}
/**
* Helper class to wrap memory accesses in JavaThread::doing_unsafe_access()
*/
class GuardUnsafeAccess {
JavaThread* _thread;
bool _active;
public:
GuardUnsafeAccess(JavaThread* thread, jobject _obj) : _thread(thread) {
if (JNIHandles::resolve(_obj) == NULL) {
// native/off-heap access which may raise SIGBUS if accessing
// memory mapped file data in a region of the file which has
// been truncated and is now invalid
_thread->set_doing_unsafe_access(true);
_active = true;
} else {
_active = false;
}
}
~GuardUnsafeAccess() {
if (_active) {
_thread->set_doing_unsafe_access(false);
}
}
};
public:
MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
: _thread(thread), _obj(obj), _offset(offset) {
}
template <typename T>
T get() {
GuardUnsafeAccess guard(_thread, _obj);
T* p = (T*)addr();
T x = normalize_for_read(*p);
return x;
}
template <typename T>
void put(T x) {
GuardUnsafeAccess guard(_thread, _obj);
T* p = (T*)addr();
*p = normalize_for_write(x);
}
template <typename T>
T get_volatile() {
GuardUnsafeAccess guard(_thread, _obj);
T* p = (T*)addr();
if (support_IRIW_for_not_multiple_copy_atomic_cpu) {
OrderAccess::fence();
}
T x = OrderAccess::load_acquire((volatile T*)p);
return normalize_for_read(x);
}
template <typename T>
void put_volatile(T x) {
GuardUnsafeAccess guard(_thread, _obj);
T* p = (T*)addr();
OrderAccess::release_store_fence((volatile T*)p, normalize_for_write(x));
}
#ifndef SUPPORTS_NATIVE_CX8
jlong get_jlong_locked() {
GuardUnsafeAccess guard(_thread, _obj);
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
jlong* p = (jlong*)addr();
jlong x = Atomic::load(p);
return x;
}
void put_jlong_locked(jlong x) {
GuardUnsafeAccess guard(_thread, _obj);
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
jlong* p = (jlong*)addr();
Atomic::store(normalize_for_write(x), p);
}
#endif
};
// Get/PutObject must be special-cased, since it works with handles.
// These functions allow a null base pointer with an arbitrary address.
// But if the base pointer is non-null, the offset should make some sense.
// That is, it should be in the range [0, MAX_OBJECT_SIZE].
UNSAFE_ENTRY(jobject, Unsafe_GetObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
oop p = JNIHandles::resolve(obj);
oop v;
if (UseCompressedOops) {
narrowOop n = *(narrowOop*)index_oop_from_field_offset_long(p, offset);
v = oopDesc::decode_heap_oop(n);
} else {
v = *(oop*)index_oop_from_field_offset_long(p, offset);
}
jobject ret = JNIHandles::make_local(env, v);
#if INCLUDE_ALL_GCS
// We could be accessing the referent field in a reference
// object. If G1 is enabled then we need to register non-null
// referent with the SATB barrier.
if (UseG1GC) {
bool needs_barrier = false;
if (ret != NULL) {
if (offset == java_lang_ref_Reference::referent_offset && obj != NULL) {
oop o = JNIHandles::resolve(obj);
Klass* k = o->klass();
if (InstanceKlass::cast(k)->reference_type() != REF_NONE) {
assert(InstanceKlass::cast(k)->is_subclass_of(SystemDictionary::Reference_klass()), "sanity");
needs_barrier = true;
}
}
}
if (needs_barrier) {
oop referent = JNIHandles::resolve(ret);
G1SATBCardTableModRefBS::enqueue(referent);
}
}
#endif // INCLUDE_ALL_GCS
return ret;
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_PutObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
oop x = JNIHandles::resolve(x_h);
oop p = JNIHandles::resolve(obj);
if (UseCompressedOops) {
oop_store((narrowOop*)index_oop_from_field_offset_long(p, offset), x);
} else {
oop_store((oop*)index_oop_from_field_offset_long(p, offset), x);
}
} UNSAFE_END
UNSAFE_ENTRY(jobject, Unsafe_GetObjectVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
oop p = JNIHandles::resolve(obj);
void* addr = index_oop_from_field_offset_long(p, offset);
volatile oop v;
if (UseCompressedOops) {
volatile narrowOop n = *(volatile narrowOop*) addr;
(void)const_cast<oop&>(v = oopDesc::decode_heap_oop(n));
} else {
(void)const_cast<oop&>(v = *(volatile oop*) addr);
}
OrderAccess::acquire();
return JNIHandles::make_local(env, v);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_PutObjectVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
oop x = JNIHandles::resolve(x_h);
oop p = JNIHandles::resolve(obj);
void* addr = index_oop_from_field_offset_long(p, offset);
OrderAccess::release();
if (UseCompressedOops) {
oop_store((narrowOop*)addr, x);
} else {
oop_store((oop*)addr, x);
}
OrderAccess::fence();
} UNSAFE_END
UNSAFE_ENTRY(jobject, Unsafe_GetUncompressedObject(JNIEnv *env, jobject unsafe, jlong addr)) {
oop v = *(oop*) (address) addr;
return JNIHandles::make_local(env, v);
} UNSAFE_END
#ifndef SUPPORTS_NATIVE_CX8
// VM_Version::supports_cx8() is a surrogate for 'supports atomic long memory ops'.
//
// On platforms which do not support atomic compare-and-swap of jlong (8 byte)
// values we have to use a lock-based scheme to enforce atomicity. This has to be
// applied to all Unsafe operations that set the value of a jlong field. Even so
// the compareAndSwapLong operation will not be atomic with respect to direct stores
// to the field from Java code. It is important therefore that any Java code that
// utilizes these Unsafe jlong operations does not perform direct stores. To permit
// direct loads of the field from Java code we must also use Atomic::store within the
// locked regions. And for good measure, in case there are direct stores, we also
// employ Atomic::load within those regions. Note that the field in question must be
// volatile and so must have atomic load/store accesses applied at the Java level.
//
// The locking scheme could utilize a range of strategies for controlling the locking
// granularity: from a lock per-field through to a single global lock. The latter is
// the simplest and is used for the current implementation. Note that the Java object
// that contains the field, can not, in general, be used for locking. To do so can lead
// to deadlocks as we may introduce locking into what appears to the Java code to be a
// lock-free path.
//
// As all the locked-regions are very short and themselves non-blocking we can treat
// them as leaf routines and elide safepoint checks (ie we don't perform any thread
// state transitions even when blocking for the lock). Note that if we do choose to
// add safepoint checks and thread state transitions, we must ensure that we calculate
// the address of the field _after_ we have acquired the lock, else the object may have
// been moved by the GC
UNSAFE_ENTRY(jlong, Unsafe_GetLongVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
if (VM_Version::supports_cx8()) {
return MemoryAccess(thread, obj, offset).get_volatile<jlong>();
} else {
return MemoryAccess(thread, obj, offset).get_jlong_locked();
}
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_PutLongVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong x)) {
if (VM_Version::supports_cx8()) {
MemoryAccess(thread, obj, offset).put_volatile<jlong>(x);
} else {
MemoryAccess(thread, obj, offset).put_jlong_locked(x);
}
} UNSAFE_END
#endif // not SUPPORTS_NATIVE_CX8
UNSAFE_LEAF(jboolean, Unsafe_isBigEndian0(JNIEnv *env, jobject unsafe)) {
#ifdef VM_LITTLE_ENDIAN
return false;
#else
return true;
#endif
} UNSAFE_END
UNSAFE_LEAF(jint, Unsafe_unalignedAccess0(JNIEnv *env, jobject unsafe)) {
return UseUnalignedAccesses;
} UNSAFE_END
#define DEFINE_GETSETOOP(java_type, Type) \
\
UNSAFE_ENTRY(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
return MemoryAccess(thread, obj, offset).get<java_type>(); \
} UNSAFE_END \
\
UNSAFE_ENTRY(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
MemoryAccess(thread, obj, offset).put<java_type>(x); \
} UNSAFE_END \
\
// END DEFINE_GETSETOOP.
DEFINE_GETSETOOP(jboolean, Boolean)
DEFINE_GETSETOOP(jbyte, Byte)
DEFINE_GETSETOOP(jshort, Short);
DEFINE_GETSETOOP(jchar, Char);
DEFINE_GETSETOOP(jint, Int);
DEFINE_GETSETOOP(jlong, Long);
DEFINE_GETSETOOP(jfloat, Float);
DEFINE_GETSETOOP(jdouble, Double);
#undef DEFINE_GETSETOOP
#define DEFINE_GETSETOOP_VOLATILE(java_type, Type) \
\
UNSAFE_ENTRY(java_type, Unsafe_Get##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
return MemoryAccess(thread, obj, offset).get_volatile<java_type>(); \
} UNSAFE_END \
\
UNSAFE_ENTRY(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
MemoryAccess(thread, obj, offset).put_volatile<java_type>(x); \
} UNSAFE_END \
\
// END DEFINE_GETSETOOP_VOLATILE.
DEFINE_GETSETOOP_VOLATILE(jboolean, Boolean)
DEFINE_GETSETOOP_VOLATILE(jbyte, Byte)
DEFINE_GETSETOOP_VOLATILE(jshort, Short);
DEFINE_GETSETOOP_VOLATILE(jchar, Char);
DEFINE_GETSETOOP_VOLATILE(jint, Int);
DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
#ifdef SUPPORTS_NATIVE_CX8
DEFINE_GETSETOOP_VOLATILE(jlong, Long);
#endif
#undef DEFINE_GETSETOOP_VOLATILE
UNSAFE_LEAF(void, Unsafe_LoadFence(JNIEnv *env, jobject unsafe)) {
OrderAccess::acquire();
} UNSAFE_END
UNSAFE_LEAF(void, Unsafe_StoreFence(JNIEnv *env, jobject unsafe)) {
OrderAccess::release();
} UNSAFE_END
UNSAFE_LEAF(void, Unsafe_FullFence(JNIEnv *env, jobject unsafe)) {
OrderAccess::fence();
} UNSAFE_END
////// Allocation requests
UNSAFE_ENTRY(jobject, Unsafe_AllocateInstance(JNIEnv *env, jobject unsafe, jclass cls)) {
ThreadToNativeFromVM ttnfv(thread);
return env->AllocObject(cls);
} UNSAFE_END
UNSAFE_ENTRY(jlong, Unsafe_AllocateMemory0(JNIEnv *env, jobject unsafe, jlong size)) {
size_t sz = (size_t)size;
sz = round_to(sz, HeapWordSize);
void* x = os::malloc(sz, mtInternal);
return addr_to_java(x);
} UNSAFE_END
UNSAFE_ENTRY(jlong, Unsafe_ReallocateMemory0(JNIEnv *env, jobject unsafe, jlong addr, jlong size)) {
void* p = addr_from_java(addr);
size_t sz = (size_t)size;
sz = round_to(sz, HeapWordSize);
void* x = os::realloc(p, sz, mtInternal);
return addr_to_java(x);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_FreeMemory0(JNIEnv *env, jobject unsafe, jlong addr)) {
void* p = addr_from_java(addr);
os::free(p);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_SetMemory0(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong size, jbyte value)) {
size_t sz = (size_t)size;
oop base = JNIHandles::resolve(obj);
void* p = index_oop_from_field_offset_long(base, offset);
Copy::fill_to_memory_atomic(p, sz, value);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_CopyMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size)) {
size_t sz = (size_t)size;
oop srcp = JNIHandles::resolve(srcObj);
oop dstp = JNIHandles::resolve(dstObj);
void* src = index_oop_from_field_offset_long(srcp, srcOffset);
void* dst = index_oop_from_field_offset_long(dstp, dstOffset);
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
UNSAFE_LEAF(void, Unsafe_CopySwapMemory0(JNIEnv *env, jobject unsafe, jobject srcObj, jlong srcOffset, jobject dstObj, jlong dstOffset, jlong size, jlong elemSize)) {
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
}
} UNSAFE_END
////// Random queries
UNSAFE_LEAF(jint, Unsafe_AddressSize0(JNIEnv *env, jobject unsafe)) {
return sizeof(void*);
} UNSAFE_END
UNSAFE_LEAF(jint, Unsafe_PageSize()) {
return os::vm_page_size();
} UNSAFE_END
static jint find_field_offset(jobject field, int must_be_static, TRAPS) {
assert(field != NULL, "field must not be NULL");
oop reflected = JNIHandles::resolve_non_null(field);
oop mirror = java_lang_reflect_Field::clazz(reflected);
Klass* k = java_lang_Class::as_Klass(mirror);
int slot = java_lang_reflect_Field::slot(reflected);
int modifiers = java_lang_reflect_Field::modifiers(reflected);
if (must_be_static >= 0) {
int really_is_static = ((modifiers & JVM_ACC_STATIC) != 0);
if (must_be_static != really_is_static) {
THROW_0(vmSymbols::java_lang_IllegalArgumentException());
}
}
int offset = InstanceKlass::cast(k)->field_offset(slot);
return field_offset_from_byte_offset(offset);
}
UNSAFE_ENTRY(jlong, Unsafe_ObjectFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
return find_field_offset(field, 0, THREAD);
} UNSAFE_END
UNSAFE_ENTRY(jlong, Unsafe_StaticFieldOffset0(JNIEnv *env, jobject unsafe, jobject field)) {
return find_field_offset(field, 1, THREAD);
} UNSAFE_END
UNSAFE_ENTRY(jobject, Unsafe_StaticFieldBase0(JNIEnv *env, jobject unsafe, jobject field)) {
assert(field != NULL, "field must not be NULL");
// Note: In this VM implementation, a field address is always a short
// offset from the base of a a klass metaobject. Thus, the full dynamic
// range of the return type is never used. However, some implementations
// might put the static field inside an array shared by many classes,
// or even at a fixed address, in which case the address could be quite
// large. In that last case, this function would return NULL, since
// the address would operate alone, without any base pointer.
oop reflected = JNIHandles::resolve_non_null(field);
oop mirror = java_lang_reflect_Field::clazz(reflected);
int modifiers = java_lang_reflect_Field::modifiers(reflected);
if ((modifiers & JVM_ACC_STATIC) == 0) {
THROW_0(vmSymbols::java_lang_IllegalArgumentException());
}
return JNIHandles::make_local(env, mirror);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_EnsureClassInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
assert(clazz != NULL, "clazz must not be NULL");
oop mirror = JNIHandles::resolve_non_null(clazz);
Klass* klass = java_lang_Class::as_Klass(mirror);
if (klass != NULL && klass->should_be_initialized()) {
InstanceKlass* k = InstanceKlass::cast(klass);
k->initialize(CHECK);
}
}
UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_ShouldBeInitialized0(JNIEnv *env, jobject unsafe, jobject clazz)) {
assert(clazz != NULL, "clazz must not be NULL");
oop mirror = JNIHandles::resolve_non_null(clazz);
Klass* klass = java_lang_Class::as_Klass(mirror);
if (klass != NULL && klass->should_be_initialized()) {
return true;
}
return false;
}
UNSAFE_END
static void getBaseAndScale(int& base, int& scale, jclass clazz, TRAPS) {
assert(clazz != NULL, "clazz must not be NULL");
oop mirror = JNIHandles::resolve_non_null(clazz);
Klass* k = java_lang_Class::as_Klass(mirror);
if (k == NULL || !k->is_array_klass()) {
THROW(vmSymbols::java_lang_InvalidClassException());
} else if (k->is_objArray_klass()) {
base = arrayOopDesc::base_offset_in_bytes(T_OBJECT);
scale = heapOopSize;
} else if (k->is_typeArray_klass()) {
TypeArrayKlass* tak = TypeArrayKlass::cast(k);
base = tak->array_header_in_bytes();
assert(base == arrayOopDesc::base_offset_in_bytes(tak->element_type()), "array_header_size semantics ok");
scale = (1 << tak->log2_element_size());
} else {
ShouldNotReachHere();
}
}
UNSAFE_ENTRY(jint, Unsafe_ArrayBaseOffset0(JNIEnv *env, jobject unsafe, jclass clazz)) {
int base = 0, scale = 0;
getBaseAndScale(base, scale, clazz, CHECK_0);
return field_offset_from_byte_offset(base);
} UNSAFE_END
UNSAFE_ENTRY(jint, Unsafe_ArrayIndexScale0(JNIEnv *env, jobject unsafe, jclass clazz)) {
int base = 0, scale = 0;
getBaseAndScale(base, scale, clazz, CHECK_0);
// This VM packs both fields and array elements down to the byte.
// But watch out: If this changes, so that array references for
// a given primitive type (say, T_BOOLEAN) use different memory units
// than fields, this method MUST return zero for such arrays.
// For example, the VM used to store sub-word sized fields in full
// words in the object layout, so that accessors like getByte(Object,int)
// did not really do what one might expect for arrays. Therefore,
// this function used to report a zero scale factor, so that the user
// would know not to attempt to access sub-word array elements.
// // Code for unpacked fields:
// if (scale < wordSize) return 0;
// The following allows for a pretty general fieldOffset cookie scheme,
// but requires it to be linear in byte offset.
return field_offset_from_byte_offset(scale) - field_offset_from_byte_offset(0);
} UNSAFE_END
static inline void throw_new(JNIEnv *env, const char *ename) {
char buf[100];
jio_snprintf(buf, 100, "%s%s", "java/lang/", ename);
jclass cls = env->FindClass(buf);
if (env->ExceptionCheck()) {
env->ExceptionClear();
tty->print_cr("Unsafe: cannot throw %s because FindClass has failed", buf);
return;
}
env->ThrowNew(cls, NULL);
}
static jclass Unsafe_DefineClass_impl(JNIEnv *env, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd) {
// Code lifted from JDK 1.3 ClassLoader.c
jbyte *body;
char *utfName = NULL;
jclass result = 0;
char buf[128];
assert(data != NULL, "Class bytes must not be NULL");
assert(length >= 0, "length must not be negative: %d", length);
if (UsePerfData) {
ClassLoader::unsafe_defineClassCallCounter()->inc();
}
body = NEW_C_HEAP_ARRAY(jbyte, length, mtInternal);
if (body == NULL) {
throw_new(env, "OutOfMemoryError");
return 0;
}
env->GetByteArrayRegion(data, offset, length, body);
if (env->ExceptionOccurred()) {
goto free_body;
}
if (name != NULL) {
uint len = env->GetStringUTFLength(name);
int unicode_len = env->GetStringLength(name);
if (len >= sizeof(buf)) {
utfName = NEW_C_HEAP_ARRAY(char, len + 1, mtInternal);
if (utfName == NULL) {
throw_new(env, "OutOfMemoryError");
goto free_body;
}
} else {
utfName = buf;
}
env->GetStringUTFRegion(name, 0, unicode_len, utfName);
for (uint i = 0; i < len; i++) {
if (utfName[i] == '.') utfName[i] = '/';
}
}
result = JVM_DefineClass(env, utfName, loader, body, length, pd);
if (utfName && utfName != buf) {
FREE_C_HEAP_ARRAY(char, utfName);
}
free_body:
FREE_C_HEAP_ARRAY(jbyte, body);
return result;
}
UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring name, jbyteArray data, int offset, int length, jobject loader, jobject pd)) {
ThreadToNativeFromVM ttnfv(thread);
return Unsafe_DefineClass_impl(env, name, data, offset, length, loader, pd);
} UNSAFE_END
// define a class but do not make it known to the class loader or system dictionary
// - host_class: supplies context for linkage, access control, protection domain, and class loader
// - data: bytes of a class file, a raw memory address (length gives the number of bytes)
// - cp_patches: where non-null entries exist, they replace corresponding CP entries in data
// When you load an anonymous class U, it works as if you changed its name just before loading,
// to a name that you will never use again. Since the name is lost, no other class can directly
// link to any member of U. Just after U is loaded, the only way to use it is reflectively,
// through java.lang.Class methods like Class.newInstance.
// Access checks for linkage sites within U continue to follow the same rules as for named classes.
// The package of an anonymous class is given by the package qualifier on the name under which it was loaded.
// An anonymous class also has special privileges to access any member of its host class.
// This is the main reason why this loading operation is unsafe. The purpose of this is to
// allow language implementations to simulate "open classes"; a host class in effect gets
// new code when an anonymous class is loaded alongside it. A less convenient but more
// standard way to do this is with reflection, which can also be set to ignore access
// restrictions.
// Access into an anonymous class is possible only through reflection. Therefore, there
// are no special access rules for calling into an anonymous class. The relaxed access
// rule for the host class is applied in the opposite direction: A host class reflectively
// access one of its anonymous classes.
// If you load the same bytecodes twice, you get two different classes. You can reload
// the same bytecodes with or without varying CP patches.
// By using the CP patching array, you can have a new anonymous class U2 refer to an older one U1.
// The bytecodes for U2 should refer to U1 by a symbolic name (doesn't matter what the name is).
// The CONSTANT_Class entry for that name can be patched to refer directly to U1.
// This allows, for example, U2 to use U1 as a superclass or super-interface, or as
// an outer class (so that U2 is an anonymous inner class of anonymous U1).
// It is not possible for a named class, or an older anonymous class, to refer by
// name (via its CP) to a newer anonymous class.
// CP patching may also be used to modify (i.e., hack) the names of methods, classes,
// or type descriptors used in the loaded anonymous class.
// Finally, CP patching may be used to introduce "live" objects into the constant pool,
// instead of "dead" strings. A compiled statement like println((Object)"hello") can
// be changed to println(greeting), where greeting is an arbitrary object created before
// the anonymous class is loaded. This is useful in dynamic languages, in which
// various kinds of metaobjects must be introduced as constants into bytecode.
// Note the cast (Object), which tells the verifier to expect an arbitrary object,
// not just a literal string. For such ldc instructions, the verifier uses the
// type Object instead of String, if the loaded constant is not in fact a String.
static instanceKlassHandle
Unsafe_DefineAnonymousClass_impl(JNIEnv *env,
jclass host_class, jbyteArray data, jobjectArray cp_patches_jh,
u1** temp_alloc,
TRAPS) {
assert(host_class != NULL, "host_class must not be NULL");
assert(data != NULL, "data must not be NULL");
if (UsePerfData) {
ClassLoader::unsafe_defineClassCallCounter()->inc();
}
jint length = typeArrayOop(JNIHandles::resolve_non_null(data))->length();
assert(length >= 0, "class_bytes_length must not be negative: %d", length);
int class_bytes_length = (int) length;
u1* class_bytes = NEW_C_HEAP_ARRAY(u1, length, mtInternal);
if (class_bytes == NULL) {
THROW_0(vmSymbols::java_lang_OutOfMemoryError());
}
// caller responsible to free it:
*temp_alloc = class_bytes;
jbyte* array_base = typeArrayOop(JNIHandles::resolve_non_null(data))->byte_at_addr(0);
Copy::conjoint_jbytes(array_base, class_bytes, length);
objArrayHandle cp_patches_h;
if (cp_patches_jh != NULL) {
oop p = JNIHandles::resolve_non_null(cp_patches_jh);
assert(p->is_objArray(), "cp_patches must be an object[]");
cp_patches_h = objArrayHandle(THREAD, (objArrayOop)p);
}
const Klass* host_klass = java_lang_Class::as_Klass(JNIHandles::resolve_non_null(host_class));
// Make sure it's the real host class, not another anonymous class.
while (host_klass != NULL && host_klass->is_instance_klass() &&
InstanceKlass::cast(host_klass)->is_anonymous()) {
host_klass = InstanceKlass::cast(host_klass)->host_klass();
}
// Primitive types have NULL Klass* fields in their java.lang.Class instances.
if (host_klass == NULL) {
THROW_0(vmSymbols::java_lang_IllegalArgumentException());
}
const char* host_source = host_klass->external_name();
Handle host_loader(THREAD, host_klass->class_loader());
Handle host_domain(THREAD, host_klass->protection_domain());
GrowableArray<Handle>* cp_patches = NULL;
if (cp_patches_h.not_null()) {
int alen = cp_patches_h->length();
for (int i = alen-1; i >= 0; i--) {
oop p = cp_patches_h->obj_at(i);
if (p != NULL) {
Handle patch(THREAD, p);
if (cp_patches == NULL) {
cp_patches = new GrowableArray<Handle>(i+1, i+1, Handle());
}
cp_patches->at_put(i, patch);
}
}
}
ClassFileStream st(class_bytes, class_bytes_length, host_source, ClassFileStream::verify);
Symbol* no_class_name = NULL;
Klass* anonk = SystemDictionary::parse_stream(no_class_name,
host_loader,
host_domain,
&st,
host_klass,
cp_patches,
CHECK_NULL);
if (anonk == NULL) {
return NULL;
}
return instanceKlassHandle(THREAD, anonk);
}
UNSAFE_ENTRY(jclass, Unsafe_DefineAnonymousClass0(JNIEnv *env, jobject unsafe, jclass host_class, jbyteArray data, jobjectArray cp_patches_jh)) {
ResourceMark rm(THREAD);
instanceKlassHandle anon_klass;
jobject res_jh = NULL;
u1* temp_alloc = NULL;
anon_klass = Unsafe_DefineAnonymousClass_impl(env, host_class, data, cp_patches_jh, &temp_alloc, THREAD);
if (anon_klass() != NULL) {
res_jh = JNIHandles::make_local(env, anon_klass->java_mirror());
}
// try/finally clause:
if (temp_alloc != NULL) {
FREE_C_HEAP_ARRAY(u1, temp_alloc);
}
// The anonymous class loader data has been artificially been kept alive to
// this point. The mirror and any instances of this class have to keep
// it alive afterwards.
if (anon_klass() != NULL) {
anon_klass->class_loader_data()->dec_keep_alive();
}
// let caller initialize it as needed...
return (jclass) res_jh;
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_ThrowException(JNIEnv *env, jobject unsafe, jthrowable thr)) {
ThreadToNativeFromVM ttnfv(thread);
env->Throw(thr);
} UNSAFE_END
// JSR166 ------------------------------------------------------------------
UNSAFE_ENTRY(jobject, Unsafe_CompareAndExchangeObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
oop x = JNIHandles::resolve(x_h);
oop e = JNIHandles::resolve(e_h);
oop p = JNIHandles::resolve(obj);
HeapWord* addr = (HeapWord *)index_oop_from_field_offset_long(p, offset);
oop res = oopDesc::atomic_compare_exchange_oop(x, addr, e, true);
if (res == e) {
update_barrier_set((void*)addr, x);
}
return JNIHandles::make_local(env, res);
} UNSAFE_END
UNSAFE_ENTRY(jint, Unsafe_CompareAndExchangeInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
oop p = JNIHandles::resolve(obj);
jint* addr = (jint *) index_oop_from_field_offset_long(p, offset);
return (jint)(Atomic::cmpxchg(x, addr, e));
} UNSAFE_END
UNSAFE_ENTRY(jlong, Unsafe_CompareAndExchangeLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
Handle p(THREAD, JNIHandles::resolve(obj));
jlong* addr = (jlong*)index_oop_from_field_offset_long(p(), offset);
#ifdef SUPPORTS_NATIVE_CX8
return (jlong)(Atomic::cmpxchg(x, addr, e));
#else
if (VM_Version::supports_cx8()) {
return (jlong)(Atomic::cmpxchg(x, addr, e));
} else {
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
jlong val = Atomic::load(addr);
if (val == e) {
Atomic::store(x, addr);
}
return val;
}
#endif
} UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSwapObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h)) {
oop x = JNIHandles::resolve(x_h);
oop e = JNIHandles::resolve(e_h);
oop p = JNIHandles::resolve(obj);
HeapWord* addr = (HeapWord *)index_oop_from_field_offset_long(p, offset);
oop res = oopDesc::atomic_compare_exchange_oop(x, addr, e, true);
if (res != e) {
return false;
}
update_barrier_set((void*)addr, x);
return true;
} UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSwapInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
oop p = JNIHandles::resolve(obj);
jint* addr = (jint *)index_oop_from_field_offset_long(p, offset);
return (jint)(Atomic::cmpxchg(x, addr, e)) == e;
} UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSwapLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
Handle p(THREAD, JNIHandles::resolve(obj));
jlong* addr = (jlong*)index_oop_from_field_offset_long(p(), offset);
#ifdef SUPPORTS_NATIVE_CX8
return (jlong)(Atomic::cmpxchg(x, addr, e)) == e;
#else
if (VM_Version::supports_cx8()) {
return (jlong)(Atomic::cmpxchg(x, addr, e)) == e;
} else {
MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);
jlong val = Atomic::load(addr);
if (val != e) {
return false;
}
Atomic::store(x, addr);
return true;
}
#endif
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time)) {
EventThreadPark event;
HOTSPOT_THREAD_PARK_BEGIN((uintptr_t) thread->parker(), (int) isAbsolute, time);
JavaThreadParkedState jtps(thread, time != 0);
thread->parker()->park(isAbsolute != 0, time);
HOTSPOT_THREAD_PARK_END((uintptr_t) thread->parker());
if (event.should_commit()) {
oop obj = thread->current_park_blocker();
event.set_parkedClass((obj != NULL) ? obj->klass() : NULL);
event.set_timeout(time);
event.set_address((obj != NULL) ? (TYPE_ADDRESS) cast_from_oop<uintptr_t>(obj) : 0);
event.commit();
}
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread)) {
Parker* p = NULL;
if (jthread != NULL) {
oop java_thread = JNIHandles::resolve_non_null(jthread);
if (java_thread != NULL) {
jlong lp = java_lang_Thread::park_event(java_thread);
if (lp != 0) {
// This cast is OK even though the jlong might have been read
// non-atomically on 32bit systems, since there, one word will
// always be zero anyway and the value set is always the same
p = (Parker*)addr_from_java(lp);
} else {
// Grab lock if apparently null or using older version of library
MutexLocker mu(Threads_lock);
java_thread = JNIHandles::resolve_non_null(jthread);
if (java_thread != NULL) {
JavaThread* thr = java_lang_Thread::thread(java_thread);
if (thr != NULL) {
p = thr->parker();
if (p != NULL) { // Bind to Java thread for next time.
java_lang_Thread::set_park_event(java_thread, addr_to_java(p));
}
}
}
}
}
}
if (p != NULL) {
HOTSPOT_THREAD_UNPARK((uintptr_t) p);
p->unpark();
}
} UNSAFE_END
UNSAFE_ENTRY(jint, Unsafe_GetLoadAverage0(JNIEnv *env, jobject unsafe, jdoubleArray loadavg, jint nelem)) {
const int max_nelem = 3;
double la[max_nelem];
jint ret;
typeArrayOop a = typeArrayOop(JNIHandles::resolve_non_null(loadavg));
assert(a->is_typeArray(), "must be type array");
ret = os::loadavg(la, nelem);
if (ret == -1) {
return -1;
}
// if successful, ret is the number of samples actually retrieved.
assert(ret >= 0 && ret <= max_nelem, "Unexpected loadavg return value");
switch(ret) {
case 3: a->double_at_put(2, (jdouble)la[2]); // fall through
case 2: a->double_at_put(1, (jdouble)la[1]); // fall through
case 1: a->double_at_put(0, (jdouble)la[0]); break;
}
return ret;
} UNSAFE_END
/// JVM_RegisterUnsafeMethods
#define ADR "J"
#define LANG "Ljava/lang/"
#define OBJ LANG "Object;"
#define CLS LANG "Class;"
#define FLD LANG "reflect/Field;"
#define THR LANG "Throwable;"
#define DC_Args LANG "String;[BII" LANG "ClassLoader;" "Ljava/security/ProtectionDomain;"
#define DAC_Args CLS "[B[" OBJ
#define CC (char*) /*cast a literal from (const char*)*/
#define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
#define DECLARE_GETPUTOOP(Type, Desc) \
{CC "get" #Type, CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type)}, \
{CC "put" #Type, CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type)}, \
{CC "get" #Type "Volatile", CC "(" OBJ "J)" #Desc, FN_PTR(Unsafe_Get##Type##Volatile)}, \
{CC "put" #Type "Volatile", CC "(" OBJ "J" #Desc ")V", FN_PTR(Unsafe_Put##Type##Volatile)}
static JNINativeMethod jdk_internal_misc_Unsafe_methods[] = {
{CC "getObject", CC "(" OBJ "J)" OBJ "", FN_PTR(Unsafe_GetObject)},
{CC "putObject", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutObject)},
{CC "getObjectVolatile",CC "(" OBJ "J)" OBJ "", FN_PTR(Unsafe_GetObjectVolatile)},
{CC "putObjectVolatile",CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutObjectVolatile)},
{CC "getUncompressedObject", CC "(" ADR ")" OBJ, FN_PTR(Unsafe_GetUncompressedObject)},
DECLARE_GETPUTOOP(Boolean, Z),
DECLARE_GETPUTOOP(Byte, B),
DECLARE_GETPUTOOP(Short, S),
DECLARE_GETPUTOOP(Char, C),
DECLARE_GETPUTOOP(Int, I),
DECLARE_GETPUTOOP(Long, J),
DECLARE_GETPUTOOP(Float, F),
DECLARE_GETPUTOOP(Double, D),
{CC "allocateMemory0", CC "(J)" ADR, FN_PTR(Unsafe_AllocateMemory0)},
{CC "reallocateMemory0", CC "(" ADR "J)" ADR, FN_PTR(Unsafe_ReallocateMemory0)},
{CC "freeMemory0", CC "(" ADR ")V", FN_PTR(Unsafe_FreeMemory0)},
{CC "objectFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_ObjectFieldOffset0)},
{CC "staticFieldOffset0", CC "(" FLD ")J", FN_PTR(Unsafe_StaticFieldOffset0)},
{CC "staticFieldBase0", CC "(" FLD ")" OBJ, FN_PTR(Unsafe_StaticFieldBase0)},
{CC "ensureClassInitialized0", CC "(" CLS ")V", FN_PTR(Unsafe_EnsureClassInitialized0)},
{CC "arrayBaseOffset0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayBaseOffset0)},
{CC "arrayIndexScale0", CC "(" CLS ")I", FN_PTR(Unsafe_ArrayIndexScale0)},
{CC "addressSize0", CC "()I", FN_PTR(Unsafe_AddressSize0)},
{CC "pageSize", CC "()I", FN_PTR(Unsafe_PageSize)},
{CC "defineClass0", CC "(" DC_Args ")" CLS, FN_PTR(Unsafe_DefineClass0)},
{CC "allocateInstance", CC "(" CLS ")" OBJ, FN_PTR(Unsafe_AllocateInstance)},
{CC "throwException", CC "(" THR ")V", FN_PTR(Unsafe_ThrowException)},
{CC "compareAndSwapObject", CC "(" OBJ "J" OBJ "" OBJ ")Z", FN_PTR(Unsafe_CompareAndSwapObject)},
{CC "compareAndSwapInt", CC "(" OBJ "J""I""I"")Z", FN_PTR(Unsafe_CompareAndSwapInt)},
{CC "compareAndSwapLong", CC "(" OBJ "J""J""J"")Z", FN_PTR(Unsafe_CompareAndSwapLong)},
{CC "compareAndExchangeObjectVolatile", CC "(" OBJ "J" OBJ "" OBJ ")" OBJ, FN_PTR(Unsafe_CompareAndExchangeObject)},
{CC "compareAndExchangeIntVolatile", CC "(" OBJ "J""I""I"")I", FN_PTR(Unsafe_CompareAndExchangeInt)},
{CC "compareAndExchangeLongVolatile", CC "(" OBJ "J""J""J"")J", FN_PTR(Unsafe_CompareAndExchangeLong)},
{CC "park", CC "(ZJ)V", FN_PTR(Unsafe_Park)},
{CC "unpark", CC "(" OBJ ")V", FN_PTR(Unsafe_Unpark)},
{CC "getLoadAverage0", CC "([DI)I", FN_PTR(Unsafe_GetLoadAverage0)},
{CC "copyMemory0", CC "(" OBJ "J" OBJ "JJ)V", FN_PTR(Unsafe_CopyMemory0)},
{CC "copySwapMemory0", CC "(" OBJ "J" OBJ "JJJ)V", FN_PTR(Unsafe_CopySwapMemory0)},
{CC "setMemory0", CC "(" OBJ "JJB)V", FN_PTR(Unsafe_SetMemory0)},
{CC "defineAnonymousClass0", CC "(" DAC_Args ")" CLS, FN_PTR(Unsafe_DefineAnonymousClass0)},
{CC "shouldBeInitialized0", CC "(" CLS ")Z", FN_PTR(Unsafe_ShouldBeInitialized0)},
{CC "loadFence", CC "()V", FN_PTR(Unsafe_LoadFence)},
{CC "storeFence", CC "()V", FN_PTR(Unsafe_StoreFence)},
{CC "fullFence", CC "()V", FN_PTR(Unsafe_FullFence)},
{CC "isBigEndian0", CC "()Z", FN_PTR(Unsafe_isBigEndian0)},
{CC "unalignedAccess0", CC "()Z", FN_PTR(Unsafe_unalignedAccess0)}
};
#undef CC
#undef FN_PTR
#undef ADR
#undef LANG
#undef OBJ
#undef CLS
#undef FLD
#undef THR
#undef DC_Args
#undef DAC_Args
#undef DECLARE_GETPUTOOP
// This function is exported, used by NativeLookup.
// The Unsafe_xxx functions above are called only from the interpreter.
// The optimizer looks at names and signatures to recognize
// individual functions.
JVM_ENTRY(void, JVM_RegisterJDKInternalMiscUnsafeMethods(JNIEnv *env, jclass unsafeclass)) {
ThreadToNativeFromVM ttnfv(thread);
int ok = env->RegisterNatives(unsafeclass, jdk_internal_misc_Unsafe_methods, sizeof(jdk_internal_misc_Unsafe_methods)/sizeof(JNINativeMethod));
guarantee(ok == 0, "register jdk.internal.misc.Unsafe natives");
} JVM_END