JDK14/Java14源码在线阅读
/*
* Copyright (c) 2000, 2019, 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 "jni.h"
#include "jvm.h"
#include "classfile/classFileStream.hpp"
#include "classfile/classLoader.hpp"
#include "classfile/vmSymbols.hpp"
#include "jfr/jfrEvents.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "oops/access.inline.hpp"
#include "oops/fieldStreams.inline.hpp"
#include "oops/objArrayOop.inline.hpp"
#include "oops/oop.inline.hpp"
#include "oops/typeArrayOop.inline.hpp"
#include "prims/unsafe.hpp"
#include "runtime/globals.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/jniHandles.inline.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/reflection.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/thread.hpp"
#include "runtime/threadSMR.hpp"
#include "runtime/vm_version.hpp"
#include "services/threadService.hpp"
#include "utilities/align.hpp"
#include "utilities/copy.hpp"
#include "utilities/dtrace.hpp"
#include "utilities/macros.hpp"
/**
* 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 assert_field_offset_sane(oop p, jlong field_offset) {
#ifdef ASSERT
jlong byte_offset = field_offset_to_byte_offset(field_offset);
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(p->field_addr_raw((jint)byte_offset) == ptr_plus_disp,
"raw [ptr+disp] must be consistent with oop::field_addr_raw");
}
jlong p_size = HeapWordSize * (jlong)(p->size());
assert(byte_offset < p_size, "Unsafe access: offset " INT64_FORMAT " > object's size " INT64_FORMAT, (int64_t)byte_offset, (int64_t)p_size);
}
#endif
}
static inline void* index_oop_from_field_offset_long(oop p, jlong field_offset) {
assert_field_offset_sane(p, field_offset);
jlong byte_offset = field_offset_to_byte_offset(field_offset);
if (p != NULL) {
p = Access<>::resolve(p);
}
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 to wrap memory accesses in JavaThread::doing_unsafe_access()
*/
class GuardUnsafeAccess {
JavaThread* _thread;
public:
GuardUnsafeAccess(JavaThread* thread) : _thread(thread) {
// 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);
}
~GuardUnsafeAccess() {
_thread->set_doing_unsafe_access(false);
}
};
/**
* Helper class for accessing memory.
*
* Normalizes values and wraps accesses in
* JavaThread::doing_unsafe_access() if needed.
*/
template <typename T>
class MemoryAccess : StackObj {
JavaThread* _thread;
oop _obj;
ptrdiff_t _offset;
// Resolves and returns the address of the memory access.
// This raw memory access may fault, so we make sure it happens within the
// guarded scope by making the access volatile at least. Since the store
// of Thread::set_doing_unsafe_access() is also volatile, these accesses
// can not be reordered by the compiler. Therefore, if the access triggers
// a fault, we will know that Thread::doing_unsafe_access() returns true.
volatile T* addr() {
void* addr = index_oop_from_field_offset_long(_obj, _offset);
return static_cast<volatile T*>(addr);
}
template <typename U>
U normalize_for_write(U x) {
return x;
}
jboolean normalize_for_write(jboolean x) {
return x & 1;
}
template <typename U>
U normalize_for_read(U x) {
return x;
}
jboolean normalize_for_read(jboolean x) {
return x != 0;
}
public:
MemoryAccess(JavaThread* thread, jobject obj, jlong offset)
: _thread(thread), _obj(JNIHandles::resolve(obj)), _offset((ptrdiff_t)offset) {
assert_field_offset_sane(_obj, offset);
}
T get() {
if (_obj == NULL) {
GuardUnsafeAccess guard(_thread);
T ret = RawAccess<>::load(addr());
return normalize_for_read(ret);
} else {
T ret = HeapAccess<>::load_at(_obj, _offset);
return normalize_for_read(ret);
}
}
void put(T x) {
if (_obj == NULL) {
GuardUnsafeAccess guard(_thread);
RawAccess<>::store(addr(), normalize_for_write(x));
} else {
HeapAccess<>::store_at(_obj, _offset, normalize_for_write(x));
}
}
T get_volatile() {
if (_obj == NULL) {
GuardUnsafeAccess guard(_thread);
volatile T ret = RawAccess<MO_SEQ_CST>::load(addr());
return normalize_for_read(ret);
} else {
T ret = HeapAccess<MO_SEQ_CST>::load_at(_obj, _offset);
return normalize_for_read(ret);
}
}
void put_volatile(T x) {
if (_obj == NULL) {
GuardUnsafeAccess guard(_thread);
RawAccess<MO_SEQ_CST>::store(addr(), normalize_for_write(x));
} else {
HeapAccess<MO_SEQ_CST>::store_at(_obj, _offset, normalize_for_write(x));
}
}
};
// 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_GetReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
oop p = JNIHandles::resolve(obj);
assert_field_offset_sane(p, offset);
oop v = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
return JNIHandles::make_local(env, v);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_PutReference(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
oop x = JNIHandles::resolve(x_h);
oop p = JNIHandles::resolve(obj);
assert_field_offset_sane(p, offset);
HeapAccess<ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
} UNSAFE_END
UNSAFE_ENTRY(jobject, Unsafe_GetReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
oop p = JNIHandles::resolve(obj);
assert_field_offset_sane(p, offset);
oop v = HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_load_at(p, offset);
return JNIHandles::make_local(env, v);
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_PutReferenceVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
oop x = JNIHandles::resolve(x_h);
oop p = JNIHandles::resolve(obj);
assert_field_offset_sane(p, offset);
HeapAccess<MO_SEQ_CST | ON_UNKNOWN_OOP_REF>::oop_store_at(p, offset, x);
} 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
#define DEFINE_GETSETOOP(java_type, Type) \
\
UNSAFE_ENTRY(java_type, Unsafe_Get##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) { \
return MemoryAccess<java_type>(thread, obj, offset).get(); \
} UNSAFE_END \
\
UNSAFE_ENTRY(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
MemoryAccess<java_type>(thread, obj, offset).put(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<java_type>(thread, obj, offset).get_volatile(); \
} UNSAFE_END \
\
UNSAFE_ENTRY(void, Unsafe_Put##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \
MemoryAccess<java_type>(thread, obj, offset).put_volatile(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(jlong, Long);
DEFINE_GETSETOOP_VOLATILE(jfloat, Float);
DEFINE_GETSETOOP_VOLATILE(jdouble, Double);
#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 = align_up(sz, HeapWordSize);
void* x = os::malloc(sz, mtOther);
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 = align_up(sz, HeapWordSize);
void* x = os::realloc(p, sz, mtOther);
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);
{
GuardUnsafeAccess guard(thread);
if (StubRoutines::unsafe_arraycopy() != NULL) {
StubRoutines::UnsafeArrayCopy_stub()(src, dst, sz);
} else {
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;
{
JavaThread* thread = JavaThread::thread_from_jni_environment(env);
GuardUnsafeAccess guard(thread);
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);
{
GuardUnsafeAccess guard(thread);
Copy::conjoint_swap(src, dst, sz, esz);
}
} JVM_END
}
} UNSAFE_END
UNSAFE_LEAF (void, Unsafe_WriteBack0(JNIEnv *env, jobject unsafe, jlong line)) {
assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
#ifdef ASSERT
if (TraceMemoryWriteback) {
tty->print_cr("Unsafe: writeback 0x%p", addr_from_java(line));
}
#endif
assert(StubRoutines::data_cache_writeback() != NULL, "sanity");
(StubRoutines::DataCacheWriteback_stub())(addr_from_java(line));
} UNSAFE_END
static void doWriteBackSync0(bool is_pre)
{
assert(StubRoutines::data_cache_writeback_sync() != NULL, "sanity");
(StubRoutines::DataCacheWritebackSync_stub())(is_pre);
}
UNSAFE_LEAF (void, Unsafe_WriteBackPreSync0(JNIEnv *env, jobject unsafe)) {
assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
#ifdef ASSERT
if (TraceMemoryWriteback) {
tty->print_cr("Unsafe: writeback pre-sync");
}
#endif
doWriteBackSync0(true);
} UNSAFE_END
UNSAFE_LEAF (void, Unsafe_WriteBackPostSync0(JNIEnv *env, jobject unsafe)) {
assert(VM_Version::supports_data_cache_line_flush(), "should not get here");
#ifdef ASSERT
if (TraceMemoryWriteback) {
tty->print_cr("Unsafe: writeback pre-sync");
}
#endif
doWriteBackSync0(false);
} UNSAFE_END
////// Random queries
static jlong find_field_offset(jclass clazz, jstring name, TRAPS) {
assert(clazz != NULL, "clazz must not be NULL");
assert(name != NULL, "name must not be NULL");
ResourceMark rm(THREAD);
char *utf_name = java_lang_String::as_utf8_string(JNIHandles::resolve_non_null(name));
InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(clazz)));
jint offset = -1;
for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
Symbol *name = fs.name();
if (name->equals(utf_name)) {
offset = fs.offset();
break;
}
}
if (offset < 0) {
THROW_0(vmSymbols::java_lang_InternalError());
}
return field_offset_from_byte_offset(offset);
}
static jlong 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_ObjectFieldOffset1(JNIEnv *env, jobject unsafe, jclass c, jstring name)) {
return find_field_offset(c, name, 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) {
jclass cls = env->FindClass(ename);
if (env->ExceptionCheck()) {
env->ExceptionClear();
tty->print_cr("Unsafe: cannot throw %s because FindClass has failed", ename);
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_RETURN_NULL(jbyte, length, mtInternal);
if (body == NULL) {
throw_new(env, "java/lang/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_RETURN_NULL(char, len + 1, mtInternal);
if (utfName == NULL) {
throw_new(env, "java/lang/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
// if host_class is itself anonymous then it is replaced with its host class.
// - 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.
// The package of an anonymous class must either match its host's class's package or be in the
// unnamed package. If it is in the unnamed package then it will be put in its host class's
// package.
//
// Access checks for linkage sites within U continue to follow the same rules as for named classes.
// 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 InstanceKlass*
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_RETURN_NULL(u1, length, mtInternal);
if (class_bytes == NULL) {
THROW_0(vmSymbols::java_lang_OutOfMemoryError());
}
// caller responsible to free it:
*temp_alloc = class_bytes;
ArrayAccess<>::arraycopy_to_native(arrayOop(JNIHandles::resolve_non_null(data)), typeArrayOopDesc::element_offset<jbyte>(0),
reinterpret_cast<jbyte*>(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_unsafe_anonymous()) {
host_klass = InstanceKlass::cast(host_klass)->unsafe_anonymous_host();
}
// Primitive types have NULL Klass* fields in their java.lang.Class instances.
if (host_klass == NULL) {
THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "Host class is null");
}
assert(host_klass->is_instance_klass(), "Host class must be an instance class");
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,
InstanceKlass::cast(host_klass),
cp_patches,
CHECK_NULL);
if (anonk == NULL) {
return NULL;
}
return InstanceKlass::cast(anonk);
}
UNSAFE_ENTRY(jclass, Unsafe_DefineAnonymousClass0(JNIEnv *env, jobject unsafe, jclass host_class, jbyteArray data, jobjectArray cp_patches_jh)) {
ResourceMark rm(THREAD);
jobject res_jh = NULL;
u1* temp_alloc = NULL;
InstanceKlass* 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:
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_CompareAndExchangeReference(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);
assert_field_offset_sane(p, offset);
oop res = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, 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);
if (p == NULL) {
volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
return RawAccess<>::atomic_cmpxchg(addr, e, x);
} else {
assert_field_offset_sane(p, offset);
return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
}
} UNSAFE_END
UNSAFE_ENTRY(jlong, Unsafe_CompareAndExchangeLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
oop p = JNIHandles::resolve(obj);
if (p == NULL) {
volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
return RawAccess<>::atomic_cmpxchg(addr, e, x);
} else {
assert_field_offset_sane(p, offset);
return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
}
} UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetReference(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);
assert_field_offset_sane(p, offset);
oop ret = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x);
return ret == e;
} UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetInt(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jint e, jint x)) {
oop p = JNIHandles::resolve(obj);
if (p == NULL) {
volatile jint* addr = (volatile jint*)index_oop_from_field_offset_long(p, offset);
return RawAccess<>::atomic_cmpxchg(addr, e, x) == e;
} else {
assert_field_offset_sane(p, offset);
return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x) == e;
}
} UNSAFE_END
UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSetLong(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong e, jlong x)) {
oop p = JNIHandles::resolve(obj);
if (p == NULL) {
volatile jlong* addr = (volatile jlong*)index_oop_from_field_offset_long(p, offset);
return RawAccess<>::atomic_cmpxchg(addr, e, x) == e;
} else {
assert_field_offset_sane(p, offset);
return HeapAccess<>::atomic_cmpxchg_at(p, (ptrdiff_t)offset, e, x) == e;
}
} UNSAFE_END
static void post_thread_park_event(EventThreadPark* event, const oop obj, jlong timeout_nanos, jlong until_epoch_millis) {
assert(event != NULL, "invariant");
assert(event->should_commit(), "invariant");
event->set_parkedClass((obj != NULL) ? obj->klass() : NULL);
event->set_timeout(timeout_nanos);
event->set_until(until_epoch_millis);
event->set_address((obj != NULL) ? (u8)cast_from_oop<uintptr_t>(obj) : 0);
event->commit();
}
UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time)) {
HOTSPOT_THREAD_PARK_BEGIN((uintptr_t) thread->parker(), (int) isAbsolute, time);
EventThreadPark event;
JavaThreadParkedState jtps(thread, time != 0);
thread->parker()->park(isAbsolute != 0, time);
if (event.should_commit()) {
const oop obj = thread->current_park_blocker();
if (time == 0) {
post_thread_park_event(&event, obj, min_jlong, min_jlong);
} else {
if (isAbsolute != 0) {
post_thread_park_event(&event, obj, min_jlong, time);
} else {
post_thread_park_event(&event, obj, time, min_jlong);
}
}
}
HOTSPOT_THREAD_PARK_END((uintptr_t) thread->parker());
} UNSAFE_END
UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread)) {
Parker* p = NULL;
if (jthread != NULL) {
ThreadsListHandle tlh;
JavaThread* thr = NULL;
oop java_thread = NULL;
(void) tlh.cv_internal_thread_to_JavaThread(jthread, &thr, &java_thread);
if (java_thread != NULL) {
// This is a valid oop.
if (thr != NULL) {
// The JavaThread is alive.
p = thr->parker();
}
}
} // ThreadsListHandle is destroyed here.
// 'p' points to type-stable-memory if non-NULL. If the target
// thread terminates before we get here the new user of this
// Parker will get a 'spurious' unpark - which is perfectly valid.
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 "getReference", CC "(" OBJ "J)" OBJ "", FN_PTR(Unsafe_GetReference)},
{CC "putReference", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReference)},
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