Quelle  var_handles.cc

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "var_handles.h"

#include "art_method.h"
#include "common_throws.h"
#include "dex/dex_instruction.h"
#include "handle.h"
#include "method_handles-inl.h"
#include "mirror/method_type-inl.h"
#include "mirror/var_handle.h"

namespace art HIDDEN {

namespace {

template <typename CallSiteType, typename CalleeType>
class ThrowWrongMethodTypeFunctionImpl final : public ThrowWrongMethodTypeFunction {
 public:
  ThrowWrongMethodTypeFunctionImpl(CallSiteType callsite_type, CalleeType callee_type)
      : callsite_type_(callsite_type),
        callee_type_(callee_type) {}

  ~ThrowWrongMethodTypeFunctionImpl() {}

  void operator()() const override REQUIRES_SHARED(Locks::mutator_lock_) {
    ThrowWrongMethodTypeException(mirror::MethodType::PrettyDescriptor(callee_type_),
                                  mirror::MethodType::PrettyDescriptor(callsite_type_));
  }

 private:
  CallSiteType callsite_type_;
  CalleeType callee_type_;
};

template <typename CallSiteType>
bool VarHandleInvokeAccessorWithConversions(Thread* self,
                                            ShadowFrame& shadow_frame,
                                            Handle<mirror::VarHandle> var_handle,
                                            CallSiteType callsite_type,
                                            mirror::VarHandle::AccessMode access_mode,
                                            const InstructionOperands* operands,
                                            JValue* result)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  // Use a raw method handle for `accessor_type`, avoid allocating a managed `MethodType`.
  VariableSizedHandleScope accessor_type_hs(self);
  mirror::RawMethodType accessor_type(&accessor_type_hs);
  var_handle->GetMethodTypeForAccessMode(access_mode, accessor_type);
  using HandleScopeType = std::conditional_t<
      std::is_same_v<VariableSizedHandleScope*, CallSiteType>,
      Thread*,  // No handle scope needed, use `Thread*` that can be initialized from `self`.
      StackHandleScope<3>>;
  HandleScopeType hs(self);
  ThrowWrongMethodTypeFunctionImpl throw_wmt(callsite_type, accessor_type);
  auto from_types = mirror::MethodType::NewHandlePTypes(callsite_type, &hs);
  auto to_types = mirror::MethodType::NewHandlePTypes(accessor_type, &hs);
  const size_t num_vregs = mirror::MethodType::NumberOfVRegs(accessor_type);
  ShadowFrameAllocaUniquePtr accessor_frame =
      CREATE_SHADOW_FRAME(num_vregs, shadow_frame.GetMethod(), shadow_frame.GetDexPC());
  ShadowFrameGetter getter(shadow_frame, operands);
  static const uint32_t kFirstDestinationReg = 0;
  ShadowFrameSetter setter(accessor_frame.get(), kFirstDestinationReg);
  if (!PerformConversions(throw_wmt, from_types, to_types, &getter, &setter)) {
    DCHECK(self->IsExceptionPending());
    return false;
  }
  RangeInstructionOperands accessor_operands(kFirstDestinationReg,
                                             kFirstDestinationReg + num_vregs);
  if (!var_handle->Access(access_mode, accessor_frame.get(), &accessor_operands, result)) {
    DCHECK(self->IsExceptionPending());
    return false;
  }
  if (!ConvertReturnValue(throw_wmt,
                          mirror::MethodType::GetRType(accessor_type),
                          mirror::MethodType::GetRType(callsite_type),
                          result)) {
    DCHECK(self->IsExceptionPending());
    return false;
  }
  return true;
}

template <typename CallSiteType>
bool VarHandleInvokeAccessorImpl(Thread* self,
                                 ShadowFrame& shadow_frame,
                                 Handle<mirror::VarHandle> var_handle,
                                 CallSiteType callsite_type,
                                 const mirror::VarHandle::AccessMode access_mode,
                                 const InstructionOperands* const operands,
                                 JValue* result) REQUIRES_SHARED(Locks::mutator_lock_) {
  if (var_handle.IsNull()) {
    ThrowNullPointerExceptionFromDexPC();
    return false;
  }

  if (!var_handle->IsAccessModeSupported(access_mode)) {
    ThrowUnsupportedOperationException();
    return false;
  }

  mirror::VarHandle::MatchKind match_kind =
      var_handle->GetMethodTypeMatchForAccessMode(access_mode, callsite_type);
  if (LIKELY(match_kind == mirror::VarHandle::MatchKind::kExact)) {
    return var_handle->Access(access_mode, &shadow_frame, operands, result);
  } else if (match_kind == mirror::VarHandle::MatchKind::kWithConversions) {
    return VarHandleInvokeAccessorWithConversions(self,
                                                  shadow_frame,
                                                  var_handle,
                                                  callsite_type,
                                                  access_mode,
                                                  operands,
                                                  result);
  } else {
    DCHECK_EQ(match_kind, mirror::VarHandle::MatchKind::kNone);
    ThrowWrongMethodTypeException(var_handle->PrettyDescriptorForAccessMode(access_mode),
                                  mirror::MethodType::PrettyDescriptor(callsite_type));
    return false;
  }
}

}  // namespace

bool VarHandleInvokeAccessor(Thread* self,
                             ShadowFrame& shadow_frame,
                             Handle<mirror::VarHandle> var_handle,
                             Handle<mirror::MethodType> callsite_type,
                             const mirror::VarHandle::AccessMode access_mode,
                             const InstructionOperands* const operands,
                             JValue* result) {
  return VarHandleInvokeAccessorImpl(
      self, shadow_frame, var_handle, callsite_type, access_mode, operands, result);
}

bool VarHandleInvokeAccessor(Thread* self,
                             ShadowFrame& shadow_frame,
                             Handle<mirror::VarHandle> var_handle,
                             mirror::RawMethodType callsite_type,
                             const mirror::VarHandle::AccessMode access_mode,
                             const InstructionOperands* const operands,
                             JValue* result) {
  return VarHandleInvokeAccessorImpl(
      self, shadow_frame, var_handle, callsite_type, access_mode, operands, result);
}

bool VarHandleInvokeAccessor(Thread* self,
                             ShadowFrame& shadow_frame,
                             Handle<mirror::VarHandle> var_handle,
                             ArtMethod* caller_method,
                             const dex::ProtoIndex callsite_type_id,
                             const mirror::VarHandle::AccessMode access_mode,
                             const InstructionOperands* const operands,
                             JValue* result) {
  StackHandleScope<3> hs(self);
  ClassLinker* class_linker = Runtime::Current()->GetClassLinker();

  Handle<mirror::DexCache> dex_cache = hs.NewHandle(caller_method->GetDexCache());
  Handle<mirror::ClassLoader> class_loader = hs.NewHandle(caller_method->GetClassLoader());

  // If the `ThreadLocalRandom` class is not yet initialized, do the `VarHandle` operation
  // without creating a managed `MethodType` object. This avoids a circular initialization
  // issue when `ThreadLocalRandom.<clinit>` indirectly calls `AtomicLong.compareAndSet()`
  // (implemented with a `VarHandle`) and the `MethodType` caching circles back to the
  // `ThreadLocalRandom` with uninitialized `seeder` and throws NPE.
  //
  // Do a quick test for "visibly initialized" without a read barrier and, if that fails,
  // do a thorough test for "initialized" (including load acquire) with the read barrier.
  if (LIKELY(WellKnownClasses::java_util_concurrent_ThreadLocalRandom
                 .Get<kWithoutReadBarrier>()
                 ->IsVisiblyInitialized()) ||
      WellKnownClasses::java_util_concurrent_ThreadLocalRandom->IsInitialized()) {
    Handle<mirror::MethodType> callsite_type(hs.NewHandle(
        class_linker->ResolveMethodType(self, callsite_type_id, dex_cache, class_loader)));

    if (LIKELY(callsite_type != nullptr)) {
      return VarHandleInvokeAccessor(self,
                                     shadow_frame,
                                     var_handle,
                                     callsite_type,
                                     access_mode,
                                     operands,
                                     result);
    }
    // This implies we couldn't resolve one or more types in this VarHandle,
    // or we could not allocate the `MethodType` object.
    CHECK(self->IsExceptionPending());
    if (self->GetException()->GetClass() != WellKnownClasses::java_lang_OutOfMemoryError.Get()) {
      return false;
    }
    // Clear the OOME and retry without creating an actual `MethodType` object.
    // This prevents unexpected OOME for trivial `VarHandle` operations.
    // It also prevents odd situations where a `VarHandle` operation succeeds but the same
    // operation fails later because the `MethodType` object was evicted from the `DexCache`
    // and we suddenly run out of memory to allocate a new one.
    //
    // We have previously seen OOMEs in the run-test `183-rmw-stress-test` with
    // `--optimizng --no-image` (boot class path methods run in interpreter without JIT)
    // but it probably happened on the first execution of a trivial `VarHandle` operation
    // and not due to the `DexCache` eviction mentioned above.
    self->ClearException();
  }

  VariableSizedHandleScope callsite_type_hs(self);
  mirror::RawMethodType callsite_type(&callsite_type_hs);
  if (!class_linker->ResolveMethodType(self,
                                       callsite_type_id,
                                       dex_cache,
                                       class_loader,
                                       callsite_type)) {
    CHECK(self->IsExceptionPending());
    return false;
  }
  return VarHandleInvokeAccessor(self,
                                 shadow_frame,
                                 var_handle,
                                 callsite_type,
                                 access_mode,
                                 operands,
                                 result);
}

}  // namespace art