/*

 * 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.inline.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 in the Java heap.

#define truncate_jboolean(x) ((x) & 1)

#define truncate_jbyte(x) (x)

#define truncate_jshort(x) (x)

#define truncate_jchar(x) (x)

#define truncate_jint(x) (x)

#define truncate_jlong(x) (x)

#define truncate_jfloat(x) (x)

#define truncate_jdouble(x) (x)

#define GET_FIELD(obj, offset, type_name, v) \

  oop p = JNIHandles::resolve(obj); \

  type_name v = *(type_name*)index_oop_from_field_offset_long(p, offset)

#define SET_FIELD(obj, offset, type_name, x) \

  oop p = JNIHandles::resolve(obj); \

  *(type_name*)index_oop_from_field_offset_long(p, offset) = truncate_##type_name(x)

#define GET_FIELD_VOLATILE(obj, offset, type_name, v) \

  oop p = JNIHandles::resolve(obj); \

  if (support_IRIW_for_not_multiple_copy_atomic_cpu) { \

    OrderAccess::fence(); \

  } \

  volatile type_name v = OrderAccess::load_acquire((volatile type_name*)index_oop_from_field_offset_long(p, offset));

#define SET_FIELD_VOLATILE(obj, offset, type_name, x) \

  oop p = JNIHandles::resolve(obj); \

  OrderAccess::release_store_fence((volatile type_name*)index_oop_from_field_offset_long(p, offset), truncate_##type_name(x));

// Get/SetObject 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_SetObject(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_SetObjectVolatile(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

UNSAFE_ENTRY(jclass, Unsafe_GetJavaMirror(JNIEnv *env, jobject unsafe, jlong metaspace_klass)) {

  Klass* klass = (Klass*) (address) metaspace_klass;

  return (jclass) JNIHandles::make_local(klass->java_mirror());

} UNSAFE_END

UNSAFE_ENTRY(jlong, Unsafe_GetKlassPointer(JNIEnv *env, jobject unsafe, jobject obj)) {

  oop o = JNIHandles::resolve(obj);

  jlong klass = (jlong) (address) o->klass();

  return klass;

} 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()) {

    GET_FIELD_VOLATILE(obj, offset, jlong, v);

    return v;

  } else {

    Handle p (THREAD, JNIHandles::resolve(obj));

    jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));

    MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);

    jlong value = Atomic::load(addr);

    return value;

  }

} UNSAFE_END

UNSAFE_ENTRY(void, Unsafe_SetLongVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jlong x)) {

  if (VM_Version::supports_cx8()) {

    SET_FIELD_VOLATILE(obj, offset, jlong, x);

  } else {

    Handle p (THREAD, JNIHandles::resolve(obj));

    jlong* addr = (jlong*)(index_oop_from_field_offset_long(p(), offset));

    MutexLockerEx mu(UnsafeJlong_lock, Mutex::_no_safepoint_check_flag);

    Atomic::store(x, addr);

  }

} 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)) { \

  GET_FIELD(obj, offset, java_type, v); \

  return v; \

} UNSAFE_END \

 \

UNSAFE_ENTRY(void, Unsafe_Set##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \

  SET_FIELD(obj, offset, 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)) { \

  GET_FIELD_VOLATILE(obj, offset, java_type, v); \

  return v; \

} UNSAFE_END \

 \

UNSAFE_ENTRY(void, Unsafe_Set##Type##Volatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \

  SET_FIELD_VOLATILE(obj, offset, 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

////// Data in the C heap.

// Note:  These do not throw NullPointerException for bad pointers.

// They just crash.  Only a oop base pointer can generate a NullPointerException.

//

#define DEFINE_GETSETNATIVE(java_type, Type, native_type) \

 \

UNSAFE_ENTRY(java_type, Unsafe_GetNative##Type(JNIEnv *env, jobject unsafe, jlong addr)) { \

  void* p = addr_from_java(addr); \

  JavaThread* t = JavaThread::current(); \

  t->set_doing_unsafe_access(true); \

  java_type x = *(volatile native_type*)p; \

  t->set_doing_unsafe_access(false); \

  return x; \

} UNSAFE_END \

 \

UNSAFE_ENTRY(void, Unsafe_SetNative##Type(JNIEnv *env, jobject unsafe, jlong addr, java_type x)) { \

  JavaThread* t = JavaThread::current(); \

  t->set_doing_unsafe_access(true); \

  void* p = addr_from_java(addr); \

  *(volatile native_type*)p = x; \

  t->set_doing_unsafe_access(false); \

} UNSAFE_END \

 \

// END DEFINE_GETSETNATIVE.

DEFINE_GETSETNATIVE(jbyte, Byte, signed char)

DEFINE_GETSETNATIVE(jshort, Short, signed short);

DEFINE_GETSETNATIVE(jchar, Char, unsigned short);

DEFINE_GETSETNATIVE(jint, Int, jint);

// no long -- handled specially

DEFINE_GETSETNATIVE(jfloat, Float, float);

DEFINE_GETSETNATIVE(jdouble, Double, double);

#undef DEFINE_GETSETNATIVE

UNSAFE_ENTRY(jlong, Unsafe_GetNativeLong(JNIEnv *env, jobject unsafe, jlong addr)) {

  JavaThread* t = JavaThread::current();

  // We do it this way to avoid problems with access to heap using 64

  // bit loads, as jlong in heap could be not 64-bit aligned, and on

  // some CPUs (SPARC) it leads to SIGBUS.

  t->set_doing_unsafe_access(true);

  void* p = addr_from_java(addr);

  jlong x;

  if (is_ptr_aligned(p, sizeof(jlong)) == 0) {

    // jlong is aligned, do a volatile access

    x = *(volatile jlong*)p;

  } else {

    jlong_accessor acc;

    acc.words[0] = ((volatile jint*)p)[0];

    acc.words[1] = ((volatile jint*)p)[1];

    x = acc.long_value;

  }

  t->set_doing_unsafe_access(false);

  return x;

} UNSAFE_END

UNSAFE_ENTRY(void, Unsafe_SetNativeLong(JNIEnv *env, jobject unsafe, jlong addr, jlong x)) {

  JavaThread* t = JavaThread::current();

  // see comment for Unsafe_GetNativeLong

  t->set_doing_unsafe_access(true);

  void* p = addr_from_java(addr);

  if (is_ptr_aligned(p, sizeof(jlong))) {

    // jlong is aligned, do a volatile access

    *(volatile jlong*)p = x;

  } else {

    jlong_accessor acc;

    acc.long_value = x;

    ((volatile jint*)p)[0] = acc.words[0];

    ((volatile jint*)p)[1] = acc.words[1];

  }

  t->set_doing_unsafe_access(false);

} UNSAFE_END

UNSAFE_LEAF(jlong, Unsafe_GetNativeAddress(JNIEnv *env, jobject unsafe, jlong addr)) {

  void* p = addr_from_java(addr);

  return addr_to_java(*(void**)p);

} UNSAFE_END

UNSAFE_LEAF(void, Unsafe_SetNativeAddress(JNIEnv *env, jobject unsafe, jlong addr, jlong x)) {

  void* p = addr_from_java(addr);

  *(void**)p = addr_from_java(x);

} UNSAFE_END

////// Allocation requests