/* * Copyright (c) 2000, 2020, 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 = cast_from_oop
(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 cast_from_oop
(p) + (jint) byte_offset; } else { return cast_from_oop
(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 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(addr); } template U normalize_for_write(U x) { return x; } jboolean normalize_for_write(jboolean x) { return x & 1; } template 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::load(addr()); return normalize_for_read(ret); } else { T ret = HeapAccess::load_at(_obj, _offset); return normalize_for_read(ret); } } void put_volatile(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)); } } }; // 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::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::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::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::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(thread, obj, offset).get(); \ } UNSAFE_END \ \ UNSAFE_ENTRY(void, Unsafe_Put##Type(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, java_type x)) { \ MemoryAccess(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(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(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; assert(is_aligned(sz, HeapWordSize), "sz not aligned"); 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; assert(is_aligned(sz, HeapWordSize), "sz not aligned"); 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(0), reinterpret_cast(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* 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(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; ClassLoadInfo cl_info(host_domain, InstanceKlass::cast(host_klass), cp_patches, NULL, // dynamic_nest_host Handle(), // classData false, // is_hidden false, // is_strong_hidden true); // can_access_vm_annotations Klass* anonk = SystemDictionary::parse_stream(no_class_name, host_loader, &st, cl_info, 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::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::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(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)}, {CC "getReferenceVolatile", CC "(" OBJ "J)" OBJ, FN_PTR(Unsafe_GetReferenceVolatile)}, {CC "putReferenceVolatile", CC "(" OBJ "J" OBJ ")V", FN_PTR(Unsafe_PutReferenceVolatile)}, {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 "objectFieldOffset1", CC "(" CLS LANG "String;)J", FN_PTR(Unsafe_ObjectFieldOffset1)}, {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 "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 "compareAndSetReference",CC "(" OBJ "J" OBJ "" OBJ ")Z", FN_PTR(Unsafe_CompareAndSetReference)}, {CC "compareAndSetInt", CC "(" OBJ "J""I""I"")Z", FN_PTR(Unsafe_CompareAndSetInt)}, {CC "compareAndSetLong", CC "(" OBJ "J""J""J"")Z", FN_PTR(Unsafe_CompareAndSetLong)}, {CC "compareAndExchangeReference", CC "(" OBJ "J" OBJ "" OBJ ")" OBJ, FN_PTR(Unsafe_CompareAndExchangeReference)}, {CC "compareAndExchangeInt", CC "(" OBJ "J""I""I"")I", FN_PTR(Unsafe_CompareAndExchangeInt)}, {CC "compareAndExchangeLong", 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 "writeback0", CC "(" "J" ")V", FN_PTR(Unsafe_WriteBack0)}, {CC "writebackPreSync0", CC "()V", FN_PTR(Unsafe_WriteBackPreSync0)}, {CC "writebackPostSync0", CC "()V", FN_PTR(Unsafe_WriteBackPostSync0)}, {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)}, }; #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