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
VerifiedMethod(uint32_t encountered_error_types,bool has_runtime_throw)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
Create(verifier::MethodVerifier * method_verifier)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
IsSafeCast(uint32_t pc) const53 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
GenerateSafeCastSet(verifier::MethodVerifier * method_verifier)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, /* 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 /* is_strict= */ true,
96 /* is_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