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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "verified_method.h"
     18 
     19 #include <algorithm>
     20 #include <memory>
     21 
     22 #include <android-base/logging.h>
     23 
     24 #include "dex/code_item_accessors-inl.h"
     25 #include "dex/dex_file.h"
     26 #include "dex/dex_instruction-inl.h"
     27 #include "runtime.h"
     28 #include "verifier/method_verifier-inl.h"
     29 #include "verifier/reg_type-inl.h"
     30 #include "verifier/register_line-inl.h"
     31 #include "verifier/verifier_deps.h"
     32 
     33 namespace art {
     34 
     35 VerifiedMethod::VerifiedMethod(uint32_t encountered_error_types, bool has_runtime_throw)
     36     : encountered_error_types_(encountered_error_types),
     37       has_runtime_throw_(has_runtime_throw) {
     38 }
     39 
     40 const VerifiedMethod* VerifiedMethod::Create(verifier::MethodVerifier* method_verifier) {
     41   DCHECK(Runtime::Current()->IsAotCompiler());
     42   std::unique_ptr<VerifiedMethod> verified_method(
     43       new VerifiedMethod(method_verifier->GetEncounteredFailureTypes(),
     44                          method_verifier->HasInstructionThatWillThrow()));
     45 
     46   if (method_verifier->HasCheckCasts()) {
     47     verified_method->GenerateSafeCastSet(method_verifier);
     48   }
     49 
     50   return verified_method.release();
     51 }
     52 
     53 bool VerifiedMethod::IsSafeCast(uint32_t pc) const {
     54   if (safe_cast_set_ == nullptr) {
     55     return false;
     56   }
     57   return std::binary_search(safe_cast_set_->begin(), safe_cast_set_->end(), pc);
     58 }
     59 
     60 void VerifiedMethod::GenerateSafeCastSet(verifier::MethodVerifier* method_verifier) {
     61   /*
     62    * Walks over the method code and adds any cast instructions in which
     63    * the type cast is implicit to a set, which is used in the code generation
     64    * to elide these casts.
     65    */
     66   if (method_verifier->HasFailures()) {
     67     return;
     68   }
     69   for (const DexInstructionPcPair& pair : method_verifier->CodeItem()) {
     70     const Instruction& inst = pair.Inst();
     71     const Instruction::Code code = inst.Opcode();
     72     if (code == Instruction::CHECK_CAST) {
     73       const uint32_t dex_pc = pair.DexPc();
     74       if (!method_verifier->GetInstructionFlags(dex_pc).IsVisited()) {
     75         // Do not attempt to quicken this instruction, it's unreachable anyway.
     76         continue;
     77       }
     78       const verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
     79       const verifier::RegType& reg_type(line->GetRegisterType(method_verifier,
     80                                                               inst.VRegA_21c()));
     81       const verifier::RegType& cast_type =
     82           method_verifier->ResolveCheckedClass(dex::TypeIndex(inst.VRegB_21c()));
     83       // Pass null for the method verifier to not record the VerifierDeps dependency
     84       // if the types are not assignable.
     85       if (cast_type.IsStrictlyAssignableFrom(reg_type, /* method_verifier */ nullptr)) {
     86         // The types are assignable, we record that dependency in the VerifierDeps so
     87         // that if this changes after OTA, we will re-verify again.
     88         // We check if reg_type has a class, as the verifier may have inferred it's
     89         // 'null'.
     90         if (reg_type.HasClass()) {
     91           DCHECK(cast_type.HasClass());
     92           verifier::VerifierDeps::MaybeRecordAssignability(method_verifier->GetDexFile(),
     93                                                            cast_type.GetClass(),
     94                                                            reg_type.GetClass(),
     95                                                            /* strict */ true,
     96                                                            /* assignable */ true);
     97         }
     98         if (safe_cast_set_ == nullptr) {
     99           safe_cast_set_.reset(new SafeCastSet());
    100         }
    101         // Verify ordering for push_back() to the sorted vector.
    102         DCHECK(safe_cast_set_->empty() || safe_cast_set_->back() < dex_pc);
    103         safe_cast_set_->push_back(dex_pc);
    104       }
    105     }
    106   }
    107   DCHECK(safe_cast_set_ == nullptr || !safe_cast_set_->empty());
    108 }
    109 
    110 }  // namespace art
    111